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Full text of "Kodak Data Book Volume 1 & 2"

DATA BOOK 
OF APPLIED 
PHOTOGRAPHY 



VOLUME 



Kodak 



Scientific Applications 



■- a 



Industrial Applications 



Medical Applications 



Radiography 



Filters and Equipment 



IL1U 



Audiovisual 



General Technique 



(B »™ 



Index 



Reference 



Document Copying 



o a. 

O O 
QO 



INDEX Spring 1972 

to Volumes 1, 2, and 3, and the SE Section of Volume 4 

Plates, Papers, and Films — in Volumes 4 and 5 — are covered by their Contents 
Sheets 



The bold figures immediately preceding the Data Sheet reference letters and numbers indicate 
the volume in which each particular Data Sheet will be found. An item in bold type indicates 
an actual Data Sheet title. 



A 

Acetate film splicing I, AV-2 

Acutance I, GN-I I 

4, SE-I 

Aero film speed rating 5, FM-62 

5, FM-64 

Agitation procedures 3, PR- 1 3 

Alloys, light, radiography of 2, IN-I4 

Animated films I, AV-3 

Application of infra-red 

photography in the study of 

plant diseases 2, SC-7 

Artificial-light colour photography 3, CL-8 

Artwork, size standards I, AV-6 

Astronomy, Scientific Plates for. . . .4, SE-3 

Autoradiographic Plate 2, SC-IO 

Autoradiography 2, SC-IO 



B 

Back-projection methods I, AV-I 

Bleach formulae 3, FY-5 



c 

Camera extension at various 

magnifications I, RF-4 

Camera shake I, GN-I I 

Camera-to-subject distance/ 

width-of-field tables (cine) I, AV-3 

Cell animation I, AV-3 

Centring of photomicrographic 

apparatus 2, SC-12 

Characteristic curves 4, SE-I 

Chemical Aids to Rapid 

Drying 3, PR-II 



Chemical Sundries, list of 'Kodak'. .3, FY-I 

Chemicals, list of 'Kodak' 3, FY-I 

Chromatograms, recording 

thin-layer 2, SC-6 

Chronocyclograph study 2, IN-7 

Cine films, lengths of 4, SE-4 

Cine films, splicing of I, AV-2 

Cine-Fluorography, Spot 

Filming and Kinescopy 2, MD-4 

Cinematography, high-speed 2, IN-2 

Cine-micrography, 16 mm 2, SC-8 

Cine projection I, AV-I 

, running times for super 8, 

double 8 and 16 mm films. ... I, AV-3 

techniques I, AV-3 

Cleaner and Stain-Remover 

Formulae 3, FY-7 

Cleaning colour transparencies. . . .3, CL-4 

Colour blindness 3, CL-7 

Colour Films Processed as Mono- 
chrome 3, PR-14 

, filter recommendations 

for exposing 3, CL-4 

harmony 3, CL-7 

materials, storage of 3, CL-4 

materials, filters for 3, CL-3 

perception 3, CL-7 

Colour Photographs of Signs, 

Lights and other Night 

Subjects 3, CL-12 

Colour Photography and the 

Human Eye 3, CL-9 

by Artificial Light 3, CL-8 

, problems in 3, CL-7 

reproduction in colour 

photography 3, CL-9 

sensitivity 4, SE-I 



Colour Temperature 3, CL-5 

meters 3, CL-S 

transparencies from artwork . I, AV-7 

transparencies, making mono- 
chrome negativesfrom I, GN-6 

transparencies, production 

of, for projection I, AV-7 

transparencies, cleaning of . . .3, CL-4 

Colour-Compensating Filters 3, CL-3 

3, CL-13 

Colour-print making, Dye Transfer 3, CL-2 

Colour-Printing Filters 3, CL-3 

3, CL-13 

Colour-separation filters I, FT-6 

Contact copying 2, DC- 1 

copying in the drawing office. .2, IN-5 

Microradiography 2, IN-12 

Construction materials for 

processing apparatus 3, PR-6 

Contrast 4, SE-IA 

Contrast, subject, in colour 

photography 3, CL-7 

Copiers, 'Kodak', for document- 
copying 2, IN-5 

Copying by contact 2, DC-I 

, diffusion-transfer 2, DC-4 

colour transparencies in mono- 
chrome I, GN-6 

factors, scales for 

determining I, RF-4 

Photographs and Other 

Illustrations I, GN-I 

Radiographs and Other 

Transparencies I, GN-2 

Crystallography, X-ray 2, SC-15 

D 

Darkroom Design 3, PR-7 

Darkroom design; disposal of 

wastes 3, PR-I 

Definition, sharpness of I, GN-I I 

Density and densitometers 4, SE-I 

Density strips I, FT-2 

Depth-of-field table I, RF-3 

Dermatitis from Photographic 

Chemicals 3, PR-8 

Design of darkrooms 3, PR-7 

Developer Formulae 3, FY-2 

Developers, packed, list of 3, FY-2 

Developing 'Kodak' Films, Plates 

and Papers 3, PR-13 

Developing X-ray films 2, XR-6 

Development of plates, uniform. . . .3, PR-5 



Development, tropical, 
of X-ray films 2, XR-8 

Diagrams for films' and slides I, AV-3 

Diffusion-Transfer Process using 
Kodak'Instafax'CT Materials, 
The 2, DC-4 

Dimensional Stability of Photo- 
graphic Films and Plates, The I, RF-IO 

Dish-cleaner formulae 3, FY-7 

Disposal of Photographic 

Processing Wastes 3, PR-I 

Document copying 2, DC-I 

in the drawing office ... .2, IN-5 

with 'Instafax' CT 

materials 2, DC-4 

with 'Kodak' copiers. .. .2, IN-5 

Drawing office, document 
copying in 2, IN-5 

Drying, rapid, chemical aids to 3, PR-I I 

Dyeline printing in the drawing 
office 2, IN-5 

Dye Transfer Process 3, CL-2 

E 

Effects, animated, for films I, AV-3 

Effects, image, various 4, SE-I 

Effluents; disposal of photographic 

processi ng wastes 3, PR-I 

'Ektachrome' Films, filters for 3, CL-3 

'Ektacolor' Films, filters for 3, CL-3 

'Ektagraphic' Write-on slide I, AV-4 

'Ektalux' Filters I, FT-IO 

Electron micrography, materials 

for 4, SE-5 

Emulsion distortion, 

prevention of I , RF- 1 

Emulsion speed, derivation of 4, SE-I 

Emulsion speed, methods of 

increasing I, GN-7 

Equipment, vibration insulation of 1, RF- 1 2 

for copying I, GN-I 

for making transparencies. ... I, AV-7 

'Estar' film splicing I, AV-2 

Estimating Adjustment of 
Exposure Time when Print- 
ing from Colour Negatives. . .3, CL-13 

Etch-bleach formulae 3, FY-5 

Exposure adjustment in colour 

printing 3, CL-13 

calibration of meters 4, SE-I 

chart, temperature 

distribution 2, IN-8 

charts, 

gamma-radiography 2, IN-16 



Exposure correction necessitated by 

reciprocity failure 4, SE-I 

corrections at various 

camera extensions I, RF-4 

corrections for extension 

tube lengths (cine) I, AV-3 

for colour photographs of signs, 

lights, and other night subjects 3, CL-12 

in Photomicrography 2, SC-13 

meter settings 4, SE-I 

4, SE-2 

ratios for different lens 

apertures I, RF-7 

Extension tube exposure 
factors (cine) I, AV-3 



Failure, reciprocity 4, SE-I 

False-colour photography 5, FM-IH 

Faults in Processing X-ray 

Films 2, XR-7 

Film speed scales, comparison of ..4, SE-I 
Film speeds (general): see Meter settings 

Film titling I, AV-3 

Films 5, Contents Sheet FM 

Films, animated I, AV-3 

, lengths of 4, SE-4 

, scientific 4, SE-3 

Filter sets for scientific and 

industrial purposes I, FT-3 

Filters, available forms I, FT-I 

, care of I, FT-I 

, Colour-Compensating 3, CL-3 

3, CL-13 

, Colour-Printing 3, CL-3 

3, CL-13 

, colour-separation I, FT-6 

, 'Ektalux' I, FT-IO 

for 'Kodak' Colour 

Materials 3, CL-3 

, infra-red, Nos. 87, 87C, 88A, 

89B I, FT-9 

, liquid, mercury-line I, FT-5 

■ — — , monochromatic I, FT-4 

, neutral-density I, FT-2 

, safelight I, RF-2 

I, FT-7 

, selection of I, FT-I 

, status 4, SE-I 

, ultra-violet, Nos. 2A, 2B, 2E, 

I8A, I8B I, FT-9 

, 'Wratten' Nos. 8(K2), 

9(K3), 1 1 (XI), 15(G), 25 I, FT-8 



Finishing slides I, AV-4 

Fixer regeneration 3, PR-9 

Fixers, packed, list of 3, FY-4 

Fixing-bath formulae 3, FY-4 

Flash Photography I, RF-8 

Fluid-flow visualization 2, IN- 1 

Fluorescence ultra-violet photo- 
graphy 2, SC-3 

Fluorography, cine- 2, MD-4 

Formulae, developer 3, FY-2 

, dish cleaner, stain remover. .3, FY-7 

, index to 3, FY-I 

, reducer, intensifier, and 

bleach 3, FY-S 

, stop, hardening, and 

fixing bath 3, FY-4 

, toner 3, FY-6 

Formulary: Index and General 
Information 3, FY-I 

G 

Gamma-Radiography 2, IN-16 

Gelatin adhesive 3, FY-5 

General Data on 

'Kodak' Sensitized Materials 4, SE-2 
Glossary of Some Terms Used 

in Photography I, RF-5 

Grain, fineness of I, GN-I I 

Graininess, granularity and 3, PR-2 

4, SE-I 

Granularity and Graininess 3, PR-2 

Gross specimens, pathological, 

photography of 2, MD-3 

H 

Hardeners, packed, list of 3, FY-4 

Hardening bath formulae 3, FY-4 

High-speed photography 2, IN-2 

Hypersensitization I, GN-7 

Hypo-eliminator formula 3, FY-4 

Hypo test solution formula 3, FY-4 



Image intensifies in 

cine-fluorography 2, MD-4 

Image-structure characteristics...^, SE-I 

Increasing emulsion speed I, GN-7 

Index to Formulary 3, FY-I 



Infra-red filters I, FT-9 

Photography 2, SC-7 

Photography in Medicine. .2, MD-2 

photography in the study 

of plant diseases 2, SC-7 

: recording temperature 

distribution 2, 1N-8 

sensitive plates 4, SE-3 

'Instafax' CT materials 2, DC-4 

'Instafax' Offset Materials 2, DC-5 

Intensifier formulae 3, FY-5 

Intensifying Screens 2, XR-4 



K 

Keeping of monochrome photographic 

materials and records I, RF-6 

Keeping properties and useful life 

of solutions 3, FY- 1 

Kinescopy 2, MD-4 

'Kodachrome' Films, filters 

for 3, CL-3 

'Kodacolor-X' Film, filters 

for 3, CL-3 

Kodak Dye Transfer Process . . .3, CL-2 

'Ektalux' Filters I, FT-IO 

Film Lengths 4, SE-4 

Photographic Materials for 

Electron Micrography 4, SE-5 

Photo-Sensitive Resists in 

Industry 4, SE-9 

Tola* Screen I, FT-I I 

Safelight Filters I, FT-7 

Scientific Plates and Films. 4, SE-3 

'Wratten' Filter Sets for 

Scientific and Industrial 

Purposes I, FT-3 

'Wratten' Filters I, FT-I 

'Wratten' Filters Nos.8(K2), 

9(K3), ll(XI), 1 5(G), 25... I, FT-8 

'Wratten' Ultra-Violet 

Filters Nos. 2A, 2B, 2E, I8A, 
I8B and Infra-Red Filters, 
Nos. 87, 87C, 88A, 89B I , FT-9 

'Wratten' Filter Colour- 
Separation Sets I, FT-6 

L 

Intensification | ( GN-7 

Latitude, exposure, in colour 

photography 3, CL-6 

Legal requirements relating to 

the disposal of photographic 

processing wastes 3, PR-I 



Legibility in projected visuals I, AV-6 

Lens Apertures and Exposure 

Ratios I, RF-7 

Light alloys, radiography of 2, IN-14 

Light-sources, artificial, in colour 

photography 3, CL-8 

Light-Balancing filters 3, CL-3 

Lighting for colour transparency 

production I, AV-7 

Liquid developers, list of 3, FY-2 

Liquid Filters for the Isolation 

of Certain Lines of the 

Mercury Discharge Lamp I, FT-5 

Liquids, study of flow within 2, IN-I 

Loading 'Kodak' cine and 35 mm 

miniature cameras 4, SE-4 

Loading X-ray film hangers 2, XR-6 

Localisation in Radiography. . . .2, XR-3 

M 

Macrostructure of metals, 

photography of 2, IN-IO 

Magnification at various camera 

extensions I, RF-4 

Making Monochrome Negatives 

from 35 mm Colour Trans- 
parencies I, GN-6 

Making Monochrome Slides for 

Projection I, AV-4 

Making Cine Titles, Diagrams, 

and Animated Effects I, AV-3 

Materials for the production of 

artwork I , AV-6 

Materials, 'Instafax' offset 2, DC-5 

Medicine, infra-red photography in. 2, MD-2 

Memomotion study 2, IN-7 

Metallography 2, IN-I I 

Metals, photography of macro- 
structure of 2, IN-IO 

Meter settings of 'Kodak' sensitized 

materials 4, SE-2 

Methods of Increasing Emulsion 

Speed I, GN-7 

Metol-free developers 3, PR-8 

Metol poisoning 3, PR-8 

Microfilming 2, DC- 1 

Micrography, 16 mm cine- 2, SC-8 

, electron, materials for 4, SE-5 

, X-ray 2, IN-12 

Micromotion study 2, IN-7 

Microradiography, contact 2, IN-12 

Microscope, setting up for 
photomicrography 2, SC-12 



Microstructure of metals 2, IN-I I 

Miniature films, lengths of, and 
loading into 'Kodak' 35 mm 
miniature cameras 4, SE-4 

Mired values 3, CL-5 

Mired-shift values 3, CL-5 

Modulation transfer 4, SE-I 

Monochromats and Monochro- 
matic Combinations from the 
Kodak 'Wratten' Filter Range I, FT-4 

Monochrome negative making from 
colour transparencies I, GN-6 

Monochrome Slides for Projec- 
tion, Making I, AV-4 

Motion study, photographic 
techniques in 2, IN-7 

Mould growth on photographic 

materials I, RF-9 

Movie films, lengths of 4, SE-4 



N 

Negative materials, general 

information on 4, SE-I 

, processing stains 3, PR- 1 2 

, storage stains I , RF- 1 1 

Quality I, GN-I I 

Neutral-Density Filters 
(Kodak 'Wratten* Filters 
No. 96) and 'Kodak' Photo- 
graphic Step Tablets I, FT- 2 

Night subjects, colour 
photographs of 3, CL-12 



Optical Formulae and, 

Depth-of-Field Table I, RF-3 

Offset materials, 'Instafax' 2, DC-5 



Packed developers, list of 3, FY-2 

fixers, list of 3, FY-4 

hardeners, list of 3, FY-4 

Papers 4, Contents Sheet PP 

Pathological specimens, 

photography of 2, MD-3 

Penumbral Unsharpness 2, XR-2 

Photo-Elastic Stress Analysis. . .2, SC-I 



Photographic Aspects of X-ray 

Crystallography, The 2, SC-15 

Copying of Documents 2, DC- 1 

processing wastes, disposal of 3, PR-I 

Techniques in Work 

Study 2, IN-7 

terms I, RF-5 

thermometry 2, IN-8 

Photographing Pathological 

Specimens 2, MD-3 

Photography Applied to Flow 

Visualization 2, IN-I 

, high-speed 2, IN-2 

, infra red 2, SC-7 

in the Drawing Office 2, IN-5 

in the Tropics I, GN-5 

of High-Speed Events 2, IN-2 

of the Macrostructure 

of Metals 2, IN-IO 

, ultra-violet 2, SC-3 

r, underwater I, GN-12 

Photomacrography 2, SC-I I 

Photomicrography: Centring 
and Adjustment of 

Apparatus 2, SC-I 2 

, exposure 2, SC-13 

, ultra-violet 2, SC-4 

Photo-optical techniques 2, IN-I 

Photo-sensitive resists in 

industry 4, SE-9 

'Photostat' Machine 2, IN-5 

Plant diseases, infra-red photo- 
graphy in study of 2, SC-7 

Planning boards and cards I, AV-6 

Planning, Preparation and 
Legibility in the Production 
of Transparencies for 

Projection I , AV-6 

'Platemaster' Platemaker 2, DC-I 

Plates 4, Contents Sheet PL 

, autoradiographic 2, SC-IO 

for spectrography 4, SE-3 

, scientific 4, SE-3 

, uniform development of 3, PR-5 

'Pola' screen I , FT- 1 1 

Pollution; disposal of photographic 

processing wastes 3, PR- 1 

Polyester film splicing I, AV-2 

Prevention and Removal of 
Mould Growth on Photo- 
graphic Materials, The I, RF-9 

Prevention of emulsion distortion. . I, RF-IO 

Principles of processing 3, PR-13 

Print stains from processing 3, PR- 1 2 



KODAK 

and product names quoted thus 

'EKTACHROME* 

are trade marks 



KODAK LIMITED LONDON YI262PDDB-5/xWP9*/4-72 



Kodak Data Book 



List of Sections in the five volumes 













1 




Index 




RF 


Reference 






GN 


General Technique 






AV 


Audiovisual 






FT 


Filters and Equipment 











XR Radiography 

MD Medical Applications 

IN Industrial Applications 

SC Scientific Applications 

DC Document Copying 



CL Colour 
PR Processing 
FY Formulary 



SE Sensitized Materials 
PL Plates 
PP Papers 



FM Films 



TO CLOSE - Squeeze UPPER LEVERS together 



TO OPEN - Use LOWER LEVERS 




Twist first 



then squeeze 



REFERENCE 



CONTENTS EDITION 

RF-2 Tables of Recommended Safelighting for Issue N 
Handling Sensitized Materials 

RF-3 Optical Formulae and Depth-of-Field Table Issue C 

RF-4 Scales for Determining Copying Factors Issue A 

RF-5 Glossary of Some Terms Used in Photography Issue C 

RF-6 The Storage of Monochrome Photographic Materials Issue A 
and Records 

RF-7 Lens Apertures and Exposure Ratios Issue A 

RF-8 Flash Photography Issue G 

RF-9 The Prevention and Removal of Mould Growth Issue 8 
on Photographic Materials 

RF-IO The Dimensional Stability of Photographic Films Issue 8 
and Plates 

RF-I I Stains Appearing on Stored Monochrome Issue 8 
Negatives and Prints 

RF-I 2 The Vibration Insulation of Photographic Issue A 
Equipment 



Associated Data Sheets in this or other volumes or sections 

I, FT-I KODAK 'Wratten' Filters 
I, FT-7 'Kodak' Safelight Filters 

3, PR-7 Darkroom Design 

4, SE-I Sensitometry, and Image-Structure Characteristics of 

Sensitized Materials 

4, SE-2 'Kodak' General-Purpose Still and Cine Films 



Kodak and Wratten are trade marks KODAK LIMITED 

Printed in England 
YI329PDDB-35/xWPI0/5-73 




'KODAK' FILMS 'KODAK' SAFELIGHT FILTER NO. 

Direct light from a safelamp fitted with a 25 watt pearl lamp at 1 .2 metres (4 feet) 

'4-X' Negative 7224 TD* 

2475 Recording TD 

2479 RAR TD 

2484 Pan TD 

2485 High Speed Recording TD 

2490,2491 RAR 2(1) 

2495 RAR 2 

2496, 2498, 5498 RAR TD 

'Aerochrome' Infrared 2443 TD 

'Aerocolor' Negative 2445 TD 

'Aerographic' Duplicating 2420 and 4427 I A 

'Aerographic' Duplicating 2644 I (I A) 

'Aerographic' Positive 2646 I A (OB) 

'Aerographic' SO-531 (2645) TD 

'Autopositive' 2577 Nonef 

Commercial Fine Grain CF7 I 

Commercial Ortho 4180 2 

'Defilux' Dental Nonef 

Dental X-ray — all except 'Defilux' Dental OB 

'Double-X' Negative 7222 TD* 

'Ektachrome' — all TD 

'Ektacolor' — off except Print and Slide TD 

'Ektacolor' Print 4109 and Slide 5028 I0H§ 

'Ektapan'— all TD* 

Electron Microscope 4489 IA 

Fine Grain Positive 0B 

Fine Grain Aerial Duplicating 2430 I A 

Gravu re Positive 4135 I 

High Contrast Negative 7457 TD 

High Definition Aerial 1414 and 3414 TD 

High Speed Duplicating 2575 and 4575 I A 

High Speed Infrared TD 

High Speed Infrared 2481 TD 

Infrared 'Aerographic' 2424 9 

'Kodacolor'— all TD 

'Kodachrome' — all TD 

KODAGRAPH 'Autopositive' 2576 Nonef 

'Kodagraph' Contact 2580 0B or I A 

'Kodagraph' Projection 2691 0B 

'Kodagraph' Ortho 2696 I (I A) 

'Kodaline' Reproduction 2566 and 4566 IA 

'Kodaline' Standard 2698 0B 

KODALITH 'Autoscreen' Ortho 2563 I A 

'Kodalith' Contact 2571 and 4571 0B 

'Kodalith' LR 2572 I A 

'Kodalith' Ortho Type 3— all IA 

'Kodalith' MP Contact 2562 and 4562 I A (0B) 

'Kodalith' MP High Speed Duplicating 2565 and 4565 . . I A (0B) 

'Kodalith' MP Ortho 2557, 3557 and 4557 I (I A) 

'Kodalith' MP Line 2559 I A 

'Kodalith' MP Pan 2558 TD* 

'Kodalith' Pan 2568 TD* 

'Kodalith' ROYAL Ortho 2569 and 4569 I A 

'Kodalith' Transparent Stripping 6554 Type 3 IA 

•Linagraph' Ortho 2 

'Linagraph' Pan R60 TD 

Matrix 4150 I 

Ortho Scanner 4152 I 

Pan Masking 4570 TD* 

'Panatomic-X'— all TD* 

'Panchro-Royal' 4141 TD* 

Photomicrography Color SO-456 TD 

Phototypesetting 6591 and 8591 I 

'Plus-X*— all TD* 

«Polyta«asL£olpr Proofing 2970..22Z1. 2W2 and 2973 . . ± 



'KODAK' PLATES 'KODAK* SAFELIGHT FILTER NO. 

Direct light from a safelamp fitted with a 25 watt pearl lamp at 1 .2 metres (4 feet) 

Fine Grain Autoradiographic Stripping AR.I0 . ... I 

Electron Image I 

High Resolution IA 

Metallographic 2 

M TD 

'Photoplast' and Spectroscopic, Type 649-0 I A 

Spectroscopic, Classes D, E, F and 649-F TD 

Spectroscopic, Classes J, G and O 2 

Spectroscopic, Class N and Z 9 

Spectrum Analysis No. I and No. 3 I 

SWR I 



'KODAK' PAPERS 'KODAK' SAFELIGHT FILTER NO. 

Direct light from a safelamp fitted with a 25 watt pearl lamp at 1 .2 metres (4 feet) 

'Bromesko' OBff 

Bromide — all OBff 

Contact CI45 00 (Nonef) 

'Ektachrome' RC TD 

'Ektacolor*— all I0H§ 

'Ektalith' Transfer I 

'Ektamatic' Photomechanical, S I 

'Ektamatic' Photomechanical, T I A 

'Ektamatic' Projection OBff 

EV Offset Master None 

FC OBff 

'Instafax' Offset Negative Paper, Contact Speed . Nonef 

'Instafax' Offset Foil None 

'Instafax' Offset Negative Paper, Projection Speed IA 

'Kodagraph' AUTOPOSITIVE— all Nonef 

'Kodagraph' Contact, Thin, CI3 00 

'Kodagraph' Projection P84, PWT89, PI.PP and PRQ5 . 0B 

'Kodagraph' Contact Reflex, CR 00 (Nonef) 

•Kodagraph' Slow Projection, Thin, SP53 00 

'Kodagraph' SUPER K Contact KC5 I A (0B) 

'Kodagraph* SUPER K Projection KP5 (I) 

'Kodalith'— all IA 

'Kodaprove' 0B 

'Linagraph' 1932 2 

'Linagraph' 480 and 553, Thin 2 

'Linagraph' Direct Print 1799 and 1801 Iff 

'Linagraph' Direct Print 1843, 1895 and 2022 ff 

•Linagraph' 1930 2 

'Linagraph' RP.30 2 

Mural OBff 

'Panalure'— all I0H 

Photogravure Line PLP IA (0B) 

Photogravure Regular and Special I A 

Photolettering IA (0B) 

'Photostat'— all IA 

Phototypesetting I 

PMT Negative IA 

PMT Reflex Nonef 

Projection PI53 Nonef 

Projection 'Velox' 00** 

Q.-F X-ray 0B 

'Royal Bromesko' OBff 

•Veribrom' OBff 

'Verilith* Plate, Types N, P and PL IA 

X-ray 6B 

Indirect light from a safelamp fitted with a 25 watt pearl lamp, 2 metres 
(7 feet) from the reflecting surface 

X-ray 6BR 



TABLES OF RECOMMENDED SAFELIGHTING 
FOR HANDLING SENSITIZED MATERIALS 



TABLE OF SAFELIGHT FILTER COLOURS 



'Kodak' 
Safelight 
Filter No. 


Colour 


'Kodak' 
Safelight 
Filter No. 


Colour 


00 

OB 

1 

IA 

2 


Light yellow 
Amber-yellow 
Red 

Light red 
Dark red 


3 

6B 

6BR 

9 

I0H 

12 


Dark green 
Brown 
Light brown 
Blue-green 
Dark amber 
Light green 



For further information on safelight filters, their spectral transmission 
curves, and a suitable safelight test for most materials, see Data Sheet 
FT-7 " 'Kodak' Safelight Filters". 



Issue N 



Kodak Data Sheet 
RF-2 



Kodak and product names printed thus — 'Ektachrome', KODALITH- 
are trade marks 



Kodak Data Sheet 
RF-2 



KODAK LIMITED 

Printed in England 
YI285PDRF-2/XWPI0/I0-72 




Processr*l8"K OB 

Projection Print 4588 I A 

'Quick-Finish' Pan 5295 TD* 

'Royal-X' Pan— all TD 

RP/F X-OMAT 'Flurospot* 2 

Separation Negative, 4131 Type I and 4133 Type 2 TD* 

Spectrum Analysis No. I and No. 3 I 

SUPER-XX 'Aero' and 'Aerecon' Type H TD* 

SWR I 

«Tri-X'— all except 'Tri-X' Ortho TD* 

'Tri-X* Ortho 4163 2 

'Tri-Mask' 4104 TD 

•Verichrome' Pan TD* 

X-ray — all industrial and medical, including Monitoring, and all 

X-OMAT, except RP/F X-OMAT 'Flurospot' and dental 6B 

Indirect light from a safelamp fitted with a 25 watt pearl lamp, 
at 2 metres (7 feet) from the reflecting surface 

X-ray — all industrial and medical except RP/F X-OMAT 

'Flurospot'— (not dental) 6BR 



FOOTNOTES 

A Kodak 'Wratten' Safelamp may be used at 1 metre (3 feet) instead of direct 
illumination at 1.2 metres (4 feet). 



The safelight filter numbers or lighting condition appearing in brackets indicate 
that these can be used with caution. 

Some films and papers may be loaded into the exposing or processing apparatus 
in brighter light than the specified safelight allows — see instructions packed 
with the product. 

TD=total darkness. 

* Handle the film in total darkness for complete freedom from safelight fog. 
However, if indirect safelighting is customarily used for general darkroom 
illumination, the film must be kept at least 2 metres or 7 feet away from the 
ceiling or other reflecting surface. The safelamp should be fitted with a 
'Kodak' Safelight Filter No. 3 (dark green) and a 25 watt pearl lamp. The film 
should be shielded from the light as much as possible. White light may be 
used to inspect the film during processing after it has been immersed in an acid 
rinse followed by fixing for at least 1 minute, or, after it has been rinsed in 
running water and fixed for at least 1 minute in a fresh acid fixing bath. 

f Whilst no safelamp and safelight filter are required, these products should be 
handled as briefly as is reasonable in subdued tungsten illumination. 

J Gold fluorescent lighting only may be used. 

§ See instructions packed with the product. 

** These papers may be handled by the light of a 'Kodak' Sodium Safelamp 
with Bromide or 'Velox' Diffusers if the room is not smaller than 6x9 metres 
(20 x 30 feet) with a ceiling at least 3 metres (10 feet) high. A working 
distance of at least 2 metres (7 feet) must be used. 

tt These papers may be handled by the light of a 'Kodak' Sodium Safelamp 
with Bromide Diffusers if the room is not smaller than 6x9 metres (20 x 30 feet) 
with a ceiling at least 3 metres (10 feet) high. A working distance of at least 
2 metres (7 feet) must be used. 

X i Rolls may be loaded into magazines and processors in subdued room lighting. 



The table is used by selecting, in the top section, a row opposite the focal length 
involved and following along this row until the correct aperture is found (or the nearest 
to it). This column should then be followed down into the main body of the table until 
its conjunction with the "distance focused on", where will be found the depth-of-field 
required. If a particular focal length is not included in the table, the appropriate depth- 
of-field figures may be estimated by interpolation. 







FOCAL LENGTH AND APERTURE 








1 in (25 mm) 

2 in (50 mm) 

3 in (75 mm) 
3^ in (90 mm) 

4 in (100 mm) 

5 in (125 mm) 
5£ in (135 mm) 
8 in (200 mm) 


f/l 

f/2 

f/2.8 

f/3.5 

f/4 

T/4.5 

f/5.6 

m 


f/l. 4 
f/2.8 

m 

f/4.5 
f/5.6 
f/6.3 

m 

f/H 


f/2 

f/4 

f/5.6 

f/6.3 

f/8 

f/9 

f/H 

f/16 


f/2.8 

f/5.6 

f/8 

f/9 

f/H 

f/l 2.5 

f/16 

f/22 


f/4 
f/8 

f/H 
f/12.5 
f/16 
f/18 

f/22 
f/32 


f/5.6 

f/ll 
f/16 
f/18 

f/22 
f/25 
f/32 


f/8 
f/16 

f/22 
f/25 
f/32 
f/36 


f/H 
f/22 
f/32 
f/36 


f/16 
f/32 


Distance 
focused on 




LIMITS OF 


DEPTH OF FIELD (in feet 


and inches) 




Infinity 
(°°) 


100' 

00 


70' 

CO 


45' 

CO 


30' 

CO 


23' 

CO 


15' 

CO 


II' 

CO 


7' 8" 

CO 


5' 2" 

CO 


100 
feet 


50' 

CO 


40' 

CO 


30' 

CO 


25' 

CO 


18' 

CO 


13' 

CO 


9' 6" 

CO 


7' 1" 

CO 


5' 

CO 


50 
feet 


30' 
100' 


26' 
100' 


23' 

CO 


19' 

CO 


15' 

CO 


II' 6" 

CO 


8' 10" 

CO 


6' 6" 

CO 


4' 9" 

CO 


30 
feet 


24' 
50' 


22' 
70' 


17' 
100' 


15' 

CO 


13' 

CO 


10' 

CO 


7' 10" 

CO 


6' 2" 

CO 


4' 5" 

CO 


20 
feet 


17' 
IT 


15' 
29' 


14' 
40' 


12' 
70' 


10' 6" 
100' 


8' 8" 

CO 


6' II" 

CO 


5' 6" 

CO 


4' 2" 

CO 


15 
feet 


13' 6" 
17' 


12' 
20' 


II' 
23' 


10' 
28' 


9' 
50' 


7' 6" 

CO 


6' 3" 

CO 


5' 

CO 


3' 10" 

CO 


10 
feet 


9' 

1 1 ' 3" 


8' 8" 
II' 10" 


8' 2" 
13' 


7' 6" 
15' 


6' 10" 
19' 


6' 
30' 


5' 3" 
100' 


4' 4" 

CO 


3' 5" 

CO 


7 
feet 


6' 7" 
7' 8" 


6' 4" 
8' 


6' 1" 
8'5" 


5' 9" 
9' 2" 


5' 4" 
10' 6" 


4' 10" 
13' 


4' 3" 
20' 


3' 8" 
100' 


3' 

CO 


5 
feet 


4' 9" 
5' 4" 


4' 7" 
5' 5" 


4' 5" 
5' 8" 


4' 4" 
6' 


4' 1" 
6' 6" 


3' 9" 
7' 6" 


3' 5" 
9' 4" 


3' 
15' 


2' 7" 
100' 


4 
feet 


3' 10" 
4' 2" 


3' 9" 
4' 3" 


3' 8" 
4' 5" 


3' 7" 
4' 7" 


3' 4" 
4' II" 


3' 2" 
5' 6" 


2' II" 
6' 4" 


2' 8" 
8' 6" 


2' 3" 
18' 


3 
feet 


2' II" 
3' 1" 


2' 10" 
3' 2" 


2' 10" 
3' 2" 


2' 9" 
3' 4" 


2' 8" 
3' 6" 


2' 6" 
3' 9" 


2' 4" 
4' 2" 


2' 2" 
5' 


1 ' II" 
7' 2" 






LIMITS 


OF DEPTH OF F 


IELD (in i 


netres) 


Infinity 
(a>) 


30 

CO 


20 

CO 


15 

CO 


10 

CO 


7 

CO' 


5 

CO 


3.5 

CO 


2.5 

CO 


2 

CO' 


30 

metres 


14 

CO 


II 

CO 


8.9 

CO 


6.9 

CO 


5.2 

CO 


4.4 

CO 


2.9 

CO 


2.2 

CO 


1.53 

CO' 


20 

metres 


II 

CO 


9.1 

CO 


7.7 

CO 


6.2 

CO 


4.8 

CO 


3.7 

CO' 


2.8 

CO 


2.1 

CO 


1.50 

CO 


15 
metres 


9.4 
34 


8.2 

CO 


6.9 

CO 


5.4 

CO 


4.5 

■CO 


3.5 

CO 


2.6 

CO 


2.0 

CO 


1.46 

CO' 


10 
metres 


7.2 
17 


6.4 
23 


5.5 

CO 


4.7 

CO 


3.9 

CO 


3.2 

CO 


2.4 

CO 


1.89 

CO 


1.39 

CO 


7 
metres 


5.5 
9.7 


5.0 
II 


4.5 
16 


4.0 
32 


3.3 

CO 


2.8 

CO 


2.2 

CO 


1.75 

CO 


1.32 

CO' 


5 

metres 


4.2 
6.2 


3.9 
6.9 


3.6 
8.4 


3.2 
II 


2.8 
25 


2.2 

CO 


1.95 

CO 


1.60 

CO 


1.23 

CO 


3 

metres 


2.7 
3.4 


2.6 
3.6 


2.4 
3.9 


2.3 

4.5 


2.0 
5.7 


1.83 

CO 


1.56 

CO 


1.31 

CO 


1.06 

CO' 


2.5 
metres 


2.3 
2.8 


2.2 
2.9 


2.1 
3.1 


1.96 
3.5 


1.80 
4.1 


1.63 
5.9 


1.43 
12 


1.22 

CO 


1.00 

CO 


2 

metres 


1.86 
2.0 


1.80 
2.3 


1.73 
2.4 


1.64 
2.6 


1.53 
2.9 


1.40 
3.5 


1.24 
5.5 


1.09 
16 


0.94 

CO 


1.5 
metres 


1.42 
1.59 


1.39 
1.63 


1.35 
1.70 


1.29 
1.82 


1.22 
1.97 


1.14 
2.2 


1.15 
2.8 


0.92 
4.3 


0.79 
36 


1 

metre 


0.96 
1.04 


0.95 
1.06 


0.93 
1.09 


0.90 
1.12 


0.87 
1.19 


0.82 
1.28 


0.76 
1.46 


0.70 
1.77 


0.62 
2.7 



BIBLIOGRAPHY 



A. Cox, Optics, Focal Press, 12th edition, 1961. 

R. Kingslake, Lenses in Photography, Yoseloff, 1963. 



OPTICAL FORMULAE AND 
DEPTH-OF-FIELD TABLE 



OPTICAL FORMULAE 

The following formulae form the basis for various optical calculations. 
They serve to determine focal length (/), magnification (m), lens-to- 
subject distance (w), and lens-to-image distance (v) as required. The 
distances u and v should be measured from approximately the plane 
of the lens diaphragm. Whilst these formulae are accurate enough for 
most practical purposes, they are only approximations; therefore, the 
results obtained from them may be different from the tables of optical 
data published by lens manufacturers, because such data are derived with 
special regard for the construction and characteristics of the particular 
lenses concerned. 

Focal length 

The parent formula from which all the others are derived is : 

1 1 1 

/ v u 

Two other formulae are given for determining / when either v or u is 
unknown. These are: 



/ = 



uxm 



m+l 



/ = 



m+l 



Magnification 



m = 



Lens-to-subject distance 



u = 



Lens-to-image distance 



v = uxm 



u-f 



« = — +/ 
m 



v = f (m+l) 



m = 



v-f 



fXV 



fXU 

u—f 



DEPTH-OF-FIELD TABLE 

In the table overleaf, the criterion of sharpness is a "disc (or circle) of 
confusion" having a diameter of f+ 1000. This criterion is defined as 
the size of the image of an infinitesimal point on the subject. It may be 
necessary to adopt somewhat different values for the disc of confusion, 
as for example between large-format cameras, miniature cameras, and 
cine cameras, in order to take account of the difference in the degree of 
final enlargement which the use of these cameras involves. This accounts 
for the differences which may well be found between the depth-of-field 
figures given in this table and those published for specific lenses. 



Issue C 



Kodak Data Sheet 
RF-3 



KODAK 

is a trade mark 



Kodak Data Sheet 
RF-3 



KODAK LIMITED LONDON 

PDRF-3/xWPI0/8-70 



SCALES TO DETERMINE MAGNIFICATION AND EXPOSURE CORRECTIONS AT VARIOUS CAMERA EXTENSIONS 



EXPOSURE FACTOR 



44- 



I I I 



I . I 



l-\ 



I I I I 



I I I I 



I I 1 



I 1 I, 1 



J L_J L 



TT 



/ 



MAGNIFICATION 



TTT 



14 



l l l l 



I I II 



iu 



TT 



\ 

\ 

\ 

\ 

\ 

*\> 
444 



1l 



ACTUAL EXPOSURE REQUIRED IN SAME TIME UNIT AS SCALE E 



3 § 

111 I 1,1 I 



o> CO t~- 



I I.I 1.1 I.I 1,1 1 1 1 I.I I. I.I ll h I.I 1,1 1,1 llllll II 111 I 



T II I 



■,■ ,' , "," ■ " ■ ' ■ ' ■ ■ ■■■ 



I III I I 



I I I I 



T 



i I r 



|T , 

9> S3 



CAMERA EXTENSION DISTANCE FROM FILM PLANE TO REAR PLANE OF LENS, IN SAME UNIT AS SCALE A 



\ 
\ 

\ INDICATED EXPOSURE AT INFINITY SETTING — ANY UNIT OF TIME 

\ 
\ 



I I I I I I I I I 



I I I I I I I I I Ml I 



_L_L 



I ,1 1,1 



14. 



ll i.l ll i 



1,1,1 



I I I I 



Inn In i i In i i 



rn r 



i i r 



FOCAL LENGTH OF LENS — ANY UNIT OF LENGTH 



Instructions for use: Starting at the focal length of the lens (in any unit) on scale A, 
draw a line through the point on scale B which corresponds to the camera extension 
(in the same unit). The magnification is given by the point at which this line meets 
scale C. Drawasecond line from the magnification on scale C to the point on scale E 
corresponding to the indicated exposure (in any time unit). The actual exposure 



required is given by the point at which this second line intersects scale F (in the same 
unit as scale E). The exposure factor is given by scale D. 

Example: A 5-j in or 55 mm lens working at a total extension of I9£ in or 192.5 mm 
yields a magnification of x2.5. The exposure factor at this magnification is x 12.25 
so that if the indicated exposure is 12 sec the actual exposure should be 147 sec. 



RF-4 



SCALES FOR DETERMINING 
COPYING FACTORS 



By courtesy of R. LI. Rees 



KODAK 

is a trade mark 



Issue A Kodak Data Sheet KODAK LIMITED LONDON PDRF-4/xWPI0/3-7l 

RF-4 



GLOSSARY 

OF SOME TERMS USED IN PHOTOGRAPHY 



aberration 
accelerator 

achromat 

acutance 

agitation 

Anaglyph 

anastigmat 

anhydrous 
(anhyd.) 

angular field 

angstrom (A) 

anti-halation 
backing or 
undercoating 

aperture 

apochromat 

backing 

background 
base 



black-body 
radiator 



Issue C 



Inherent fault in the performance of a lens. 

An alkaline constituent of a developer; it activates and 
increases the activity of the developer. 

A lens which brings radiations of two chosen colours (usually 
yellow and blue-violet) to focus at the same plane. 

A numerical measure of the sharpness of the photographic 
image. 

Intermittent or continuous movement of photographic 
materials in processing solutions, or of the processing 
solutions themselves, to promote uniform processing. 

A stereoscopic process in which two images are printed in 
complementary colours and viewed through spectacles 
having one lens of each colour; each eye therefore sees only 
a single image, thus producing the sensation of a single 
stereoscopic neutral-tone image. 

A lens corrected for astigmatism (the inability to bring 
horizontal and vertical lines to a focus at the same plane). 

A dry chemical; one which does not contain water of crystal- 
lization or absorbed water (see also crystalline). 

Angle converging at the lens from the largest field of view 
which the lens can transmit on to the image plane. 

Unit of length— lO -10 metre or 0.1 nanometre. 

A coating on the back of the film base or between the emulsion 
and film base. Used to prevent light-rays, which pass 
through the emulsion, from reflecting back into the emulsion. 

In a lense — the opening, the size of which is usually controlled 
by a diaphragm. 

A lens which brings three chosen colours (usually red, green, 
and blue) to focus at the same plane. 

A layer coated on the back of films and plates to minimize 
halation (q.v.), or with for example roll-films, a strip of 
opaque material used to prevent fogging through the back of 
the film. 

Normally, the part of the scene which appears behind the 
principal subject. 

Normally the cellulose ester film, polyester film, glass, or 
paper support on which the emulsion is coated. 

A body that absorbs all the radiation that falls upon it. 
Its most important property is that it will radiate more power 
at any wavelength, and hence more total power, than any 
other body at the same temperature. 

Kodak Data Sheet 
RF-5 



candela (cd) 

cassette 

characteristic 
curve 



chromatic 
aberration 



cinching 



circle or disc 
of confusion 



clearing agent 

'cobb"-type 
test-object 



collotype 

colour 
temperature 



composition 

contrast 
contrast index 

cut (cine) 



Unit of luminous intensity. Unit of luminance is cd/m 2 . 

Light-tight film holder. 

The curve relating the density (q.v.), produced in an emulsion 
under specified conditions, to the logarithm of the exposure. 
Typically, the curve has a curved toe, a straight-line portion, 
and a shoulder (the "overexposed" region). Also called 
D Log E curve or H & D curve. 

An inherent lens characteristic causing radiation of different 
wavelengths to separate. Therefore the red, green and 
blue rays will come to a focus at different planes. The short 
wavelength, blue, closest to the lens and the long wave- 
length, red, furthest away. Consequently, the images 
formed by these three light rays do not coincide in position 
nor in size. 

Tightening a roll of film by holding the spool and pulling 
the free end. This is liable to result in intermittent parallel 
scratches or abrasion marks. 

The size at the focal plane of the image of a point. Ideally, 
a point object should give a point image, and the permissible 
departure from this ideal varies with the degree of sharpness 
and quality required. 

A chemical that neutralizes hypo in film or paper, reducing 
washing time and helping to give a more stable image. 

The pattern, prescribed by British Standard 1613:1961, 
Resolving Power of Lenses, which consists of two solid 
rectangles, each three times as long as it is wide, separated 
by one rectangle width. A sequence of such patterns, 
graduated in size, is arranged in an approximate spiral, so 
that the pattern size decreases radially inwards. 

A photomechanical process in which a hardened gelatin 
image, formed on a glass plate, is printed with greasy ink. 

The temperature to which a black-body radiator (q.v.) 
must be raised so that its visual colour matches that of 
a particular light-source. It is usually expressed in kelvins 
(q.v.). No colour temperature is applicable to light-sources, 
e.g., fluorescent tubes, having a spectral energy distribution 
differing greatly from that of a black-body radiator. For 
tungsten lamps, the colour temperature is very approximately 
50 kelvins above the actual temperature of the filament. 

The distribution, balance, and general relationship of 
masses and degrees of light and shade, line, and colour 
within a picture area. 

Generally taken to mean the density range of a negative, 
involving additionally the tone scale of the subject. 

The slope of a straight line joining two points on the 
characteristic curve that represent the approximate minimum 
and maximum densities used in practice. 

(1) The instantaneous change from one scene to another. 
Successive frames contain the last frame of one scene and 
the first frame of the following scene. (2) To stop opera- 
tion of camera, action, and/or sound recording equipment. 
(3) To sever or splice film in the editing process. 



RF-S 



crystalline 

deliquescence 

density 
(optical) 

depth of field 
depth of focus 
diaphragm 

diapositive 
dichroic fog 

diffuse (adj.) 
diffraction 



dioptre 



direct positive 
dispersion 

dissolve (cine) 



double 

(multiple) 

exposure 

dubbing 



edge fog 
editing (cine) 



Applying to solid substances which assume a definite geo- 
metrical or crystal form; such salts may or may not be 
combined with molecules of water (water of crystallization). 
Absorption of atmospheric moisture by water-soluble 
substances, which may finally liquefy. 
The light-absorbing power of a photographic image. The 
quantity of silver deposited in a given area. Normally 
expressed as the logarithm of the opacity (q.v.), or the 
logarithm of the reciprocal of the transmission (q.v.). 
The distance between the objects nearest to and furthest 
from the lens which, for practical purposes, are in focus 
at the same time. 

The distance through which the film or lens may be moved 
without the image becoming objectionably out of focus. 
(Often confused with depth of field). 

A partition in front of or behind a single lens or in between 
the components of a multiple lens, having an adjustable 
aperture controlling the amount of light reaching the sensi- 
tized material. 

A transparency; a positive image on a transparent support, 
such as glass or film. 

A form of chemical fog in which the deposit appears red or 
yellow by transmitted light and green by reflected light. 

Light scattered by a medium. 

In optics, where light from a point source passing a sharp 
edge and giving a shadow of that edge on a plane surface does 
not in fact give a sharply defined edge to the shadow. This 
arises from the interruption of the wave-train giving rise to 
interference effects due to phase differences in the waves 
reaching the obstacle from different parts of the wave front. 

A measure of lens power. The reciprocal of the focal length 
of a lens, in metres, e.g., if the focal length (/) of a lens is 

500 mm (0.5 m), then its power is ^-= — 2 dioptres. 

40 
Approximately, power in dioptres 

See reversal. 



/(in inches). 



The separation of a single beam of white light into a group 
of coloured rays by a prism, diffraction grating, etc. 

An optical or camera effect in which one scene gradually 
fades out at the same time as a second scene fades in. 
There is an apparent double exposure during the centre 
portion of a dissolve sequence where the two scenes overlap. 

The photographic recording of two (or more) images on a 
single strip of film. The images may be either superimposed 
or side by side in any relationship, sometimes individually 
vignetted (q.v.). 

The addition of sound (either music or dialogue) to a visual 
presentation via a re-recording process, which prepares a 
complete sound track (usually magnetic) that can be trans- 
ferred to and synchronized with the visual presentation. 

Light fog due to leakage of light on to the edges of a sensitized 
material. 

The process of assembling, arranging and trimming the 
desired scenes and sound tracks to the best advantage. 



RF-5 



efflorescence The property of certain chemicals to lose their water of 

crystallization and to assume a dry or powder form. 

emulsion A gelatin solution or coating containing, in colloidal suspen- 

sion, light-sensitive material usually silver halides. 

emulsion speed The photosensitivity of an emulsion, usually expressed as a 
meter setting based on the manufacturer's recommendations 
for the use of the sensitized material under typical conditions 
of exposure and development. 

Estar' film This is a thermoplastic material — polyethylene terephthalate 

base (polyester). This film base has excellent dimensional 

stability as well as extremely high strength and resistance to 

tearing. 

exposure Exposure is the product of the exposing time (t) and the 

intensity (/) of the light. The term is popularly but in- 
correctly used to mean exposing time (q.v.). 

exposing time The length of time for which the sensitized material is 

exposed to the light-source or subject. In a camera, the time 
for which the shutter is open. 

filter Transparent material used before, behind or between the 

components of the camera lens, or in any light beam, to alter 
the composition of the light by selective absorption. 

fixing Conversion of undeveloped silver salts in the emulsion to 

soluble salts which are then dissolved out partly by the fix 
and partly by the wash in order to make the image stable 
to light. 

fluorescence See luminescence. 

f/number The effective size of the lens aperture expressed as a fraction 

of the focal length of the lens. For example, the //number is 
16 if the effective diameter of the lens aperture=2mm 
where the focal length (q.v.) of the lens=32mm. 

,, , focal length 

effective diameter of lens 

focal length (f ) The distance between the image of a very distant object and 
the principal nodal point of the lens. The approximate back 
focal length may be measured from the rear component. 

fog Darkening, lightening or discoloration of a negative, print or 

transparency caused by (1) Exposure to non-image-forming 
light to which the material is sensitive. (2) Oxidation 
products during development. (3) Overdevelopment. (4) Out- 
dated film or paper. (5) Improper storage of unprocessed 
sensitized materials. 

f.p.S. Frames per second. 

gamma (y) The slope of the straight-line portion of the characteristic 

curve (q.v.). 

graininess The grainy appearance of photographic images when magni- 

fied or in enlargements, as distinct from granularity, graini- 
ness is dependent on the brightness. 

grains (1) The black specks of silver in developed materials. 

(2) Obsolescent unit of weight. 

RF-S 4 



granularity 



H&D 
halation 

half-frame 

halide 

halogen 

hertz (Hz) 
hygroscopic 

hyperfocal 
distance 

hypersensitising 

hypo 

infra-red 

irradiation 
kelvin (K) 
latent image 

latitude 



light-filter 
lumen (Im) 



Because of the irregular distribution of grains in developed 
materials. The density fluctuates irregularly from point to 
point. The granularity is the product of the mean fluctuation 
and the square root of the area of the scanning spot of the 
microdensitometer used for measuring the fluctuation. The 
values derived using this system are often referred to RMS 
Granularity values. The word is sometimes used in a quali- 
tative sense to describe the irregularity of density. 

The initials of Messrs. Hurter and Driffield. The H&D 
curve is now termed the characteristic curve (q.v.). 

Spreading of the image, caused by light which has passed 
through the emulsion and then been reflected back by the 
support. 

Usually applied to a camera or a negative having a format of 
approximately 18 x 24mm — half the size of the standard 
miniature format on 35 mm film, and the same size as one 
of the 35mm motion-picture standard film formats. 

In photographic chemistry, a compound of halogen and a 
metal, e.g., silver bromide. 

The non-metallic elements — fluorine, chlorine, bromine and 
iodine. 

Unit of frequency — cycles per second. 

The property of liquid or solid chemicals to attract moisture 
from the air. 

If a lens is so adjusted that objects at infinity are no sharper 
than the acceptable limit, the distance at which objects have 
the sharpest image is called the hyperfocal distance. A 
camera focussed on this distance gives the maximum depth 
of field (q.v.). 

Increasing the speed of a film by treatment after manufacture 
and, usually, shortly before use. 

The name for sodium thiosulphate, or a fixing bath made from 
it and other chemicals, and water. 

Invisible radiation having a wavelength longer than that of 
the red portion of the spectrum, or the descriptor for material 
specially sensitized to such radiation. 

The scattering of light within the emulsion by inter-reflection 
between the silver halide grains. 

Unit of thermodynamic temperature. Conversion of 
Celsius (°C) to K is approximately equal to °C +273. 

The invisible image which is produced by the action of 
radiation on a sensitized material and which can be developed 
to give a visible image. 

Correctly, the exposure range over which the characteristic 
curve is straight and over which negatives of the same contrast 
can be obtained. In practice, the range of exposures over 
which a film or paper will give a printable negative or an 
acceptable transparency or print. 

See filter. 

Unit of luminous flux (1 lumen per square foot= 10.764 lux) 



RF-5 



luminescence On exposure to radiation (light, ultra-violet, X-rays, electrons, 

etc.) certain substances emit radiation, usually light. This is 
called luminescence. Broadly, there are two kinds, fluor- 
escence and phosphorescence. In fluorescence, the time 
interval between absorption and emission is very short, 
whereas in phosphorescence, the time, short though it may 
be, is longer and may extend to some hours, and it continues 
for some time after the exciting radiation has ceased. 

Unit of illumination. 

Magnetic stripe on film used for sound recording. 

micrometre ((J.m) Unit of length — lCr 6 metre or 10~ 3 mm, or approximately 

(previously 0.000 04 inch. 

micron) 



lux (Ix) 
magnetic track 



microphoto- 
graphy 

miniature 
camera 



numerical 
aperture (N.A.) 



nanometre (nm) 

(previously 

millimicron) 

narrow-gauge 



newton (N) 



nodal points 



opacity 
optical track 



The copying of objects or documents at an extremely small 
scale. 

Conventionally, a camera giving a negative not larger than 
2} inches square (miniature negative). Usually applied to 
cameras using 35 mm film and giving a format of approxi- 
mately 24 x 36 mm. 

Just as the aperture of a camera lens is expressed by the 
//number, the aperture of a microscope is expressed by the 
N.A., but whereas the //number decreases with increase in 
aperture, the N.A. increases as the aperture increases. 

Unit of length — 10~ 9 metre or 10 A. 



Cine or movie film of widths narrower than standard 35 mm 
film, e.g., 16 mm, 9.5 mm, Super-8 and 8 mm, etc. Pre- 
viously known as sub-standard. 

Unit of force. That force which, when applied to a body 
having a mass of 1 kilogramme, gives it an acceleration of 
1 metre per second squared. 

Two points on the optical axis of a lens or lens system such 
that an incident ray directed towards one of the points 
emerges from the lens as if from the other point in a direction 
parallel to that of the incident ray. Although each lens 
element within a combination will have its own nodal points, 
if the incident and emergent rays only are considered then the 
combination can be treated as a single lens having a single 
pair of nodal points. These theoretical points are called 
the principal nodal points. 

The ratio of the intensity of incident light to transmitted 
light. The reciprocal of transmission. 

( 1 ) Variable-area — an optically-sensed motion-picture sound 
track in which the density of the image is constant, modulation 
being achieved by varying the area of the track. (2) Variable 
density — an optically-sensed motion-picture sound track 
in which the width of the track is constant, modulation 
being effected by variation in density. 



RF-5 



orthochromatic 
(ortho) 

panchromatic 
(pan) 

pH 



Sensitive to ultra-violet, blue, and green radiation. 



Sensitive to ultra-violet, blue, green, yellow, and red radiation. 



The logarithm of the reciprocal of the hydrogen ion con- 
centration of a solution. The value indicating neutrality 
is 7; an increase in this value indicates increasing alkalinity, 
a decrease indicates increasing acidity. 



phosphorescence See luminescence. 



photomacro- 
graphy 



photomicro- 
graphy 

polarization 



processing 



reciprocity 
failure 



refraction 



rem-jet 
resolving power 



reticulation 



Work done at low magnification (less than approximately 
x50), which is distinguished from photomicrography by the 
fact that instead of a compound microscope, a single lens 
is used to obtain the magnification by working with a lens- 
to-film distance which is greater than twice the focal length 
of the lens. 

The photography, through a microscope, of very small areas 
of a subject, usually involving considerable magnification. 

Light may be considered as vibrating in many directions. 
A polarizing filter transmits light vibrating in mainly one 
direction; light vibrating in this way is said to be polarized. 

The development and subsequent treatment of the sensitized 
material after exposure. 

The failure of the exposure factors, intensity (I) and time (r) 
to behave in a reciprocal fashion. Failure usually occurs at 
very low or very high intensities or at very long or very short 
exposure times. 

When a thin pencil (or ray) of light passes from air into 
glass or similar transparent material, or conversely, at any 
angle other than perpendicular to the surface, it undergoes an 
abrupt change of direction known as refraction. Beyond a 
certain 'critical angle' the ray is reflected from the surface, 
thus limiting the range of angles at which a ray can cross the 
boundary between materials of two different densities. 

Removable jet backing (see also anti-halation backing). 

The smaller any object pattern is, the less well seen is the 
image of it in a photograph. When it is only just visible 
it is said to be just resolved. The simplest pattern is a 
sequence of equidistant lines. When these are just resolved 
the reciprocal of the width of a line plus space is called the 
resolving power. 

A net-like appearance of an emulsion, generally caused by 
differences in temperature between the processing baths, 
the rinsing or washing water. Serious reticulation shows 
as a roughening of the surface of the emulsion. Often, 
it appears only as a microscopically fine structure and the 
image then appears "grainy". Its appearance under a 
low-power microscope or a magnifier, however, is quite 
typical. 



RF-S 



reversal 



safelamp 
safelight 

safety base 
screen 



spectrum 
(optical) 



speed or 
sensitivity 

specular 



stop (equipment) 
stop (process) 

sub-miniature 
camera 

substratum 

supercoat 

transmission 
tungsten-halogen 

ultra-violet 
'Vectograph' 



As a process, the production of a direct positive, as by 
dissolving the negative image without fixing, re-exposing, 
and developing to give a positive image: as an effect, the 
conversion of a negative image into a positive (locally or 
completely), or vice versa, under particular conditions of 
exposure or development. 

Holder consisting of a suitable light-source and safelight 
filter or niters. 

Illumination in which sensitized materials are handled, 
and therefore light modified by a suitable filter to give 
light to which the material is relatively insensitive. 

Film bases of cellulose ester or polyester which are relatively 
non-flammable. 

Surface on which projected images are viewed. Also, in 
graphic arts, a means of breaking up a continuous-tone 
image so that it may be reproduced photomechanically; 
called half-tone screen or line screen. Occasionally safelight 
niters are called safelight-screens. This term screen, 
is also used in radiography, where intensifying-screens 
consiting of a material based on lead, or more commonly 
a luminescent salt, are used to reduce exposure times. 

The range of frequencies into which ultra-violet radiation, 
light, or infra-red radiation is split on passing through a 
prism or diffraction grating. The visible spectrum covers 
the range of wavelengths from about 400 nm (blue region) to 
about 700 nm (red region). 

The response of a photographic emulsion to incident radia- 
tion. Expressed, commonly, as ASA/BS (arithmetical) 
and DIN (logarithmic), meter-settings. 

Light reflected or transmitted direct, without scattering, 
as from a mirror. Also applied to measurement made by 
collimated light beam. 

Aperture of camera lens or the setting thereof. 

An intermediate bath to stop the previous chemical action 
and to prevent carry over into the next bath. 

Usually applied to one having a format smaller than half- 
frame (q.v.). 

The layer which holds an emulsion to its base. 

A thin layer of transparent gelatin applied to the top of a 
sensitized material to provide some protection against 
physical damage to the emulsion. 

The ratio of the intensity of transmitted light to incident 
light. The reciprocal of opacity. 

Type of high-efficiency tungsten lamp. Incorrectly called 
quartz-iodine or tungsten-iodine, as envelopes may be made 
of material other than quartz, and a halogen other than 
iodine may be used. 

Invisible radiation having a wavelength shorter than that of 
the blue-violet part of the spectrum. 

A stereoscopic photograph composed of two almost super- 
imposed images which polarize light in planes 90° apart. 
A three-dimensional image is seen when they are viewed 
through properly oriented 'Polaroid' stereoscopic spectacles. 

Kodak is a trade mark 



Kodak Data Sheet 
RF-5 



KODAK LIMITED LONDON 



YI225 PDRF-5/xWPI0/2-72 



THE STORAGE OF MONOCHROME 
PHOTOGRAPHIC MATERIALS AND RECORDS 



PHOTOGRAPHIC MATERIALS 

Heat, moisture, and other unfavourable conditions may have a very 
definitely harmful effect on the life of all sensitive photographic material. In 
view of this it is desirable to store such materials so that they are protected 
as much as possible against such adverse conditions. Stored incorrectly, 
materials lose speed, clarity and sometimes contrast, and may become 
completely unusable. 

The data in this sheet refer only to storage of monochrome materials 
giving a silver image, microfilm storage conditions are covered by British* 
and American 7 Standards and in a proposed International Standard. 
Data on the storage of colour films can be found in Data Sheet CL-4. 
Diazo, vesicular and other non-silver films or processes may require 
special conditions and are therefore excluded from this Data Sheet. 
Greater detail on the storage of Motion Picture Film can be found in 
Kodak Motion Picture Leaflet MP 21. 

Storage hazards 

If a separate room is to be used as a store, it is preferable to avoid rooms 
with bad ventilation, damp basements, or top-floor rooms or rooms with 
an outside wall facing south unless the roof or wall can be thermally 
insulated. Protection should be given against excessive heat : never place 
photographic materials near hot pipes, boiler rooms, radiators, heaters or 
fires. Sensitized materials should be protected from the possibility of 
damage by water, whether from leaks, fire sprinklers or flooding of the 
floor. Exposure to harmful gases* or to rays emitted by radio-active 
substances or X-ray equipment, can soon render photographic materials 
quite useless. An adequate thickness of lead or other form of suitable 
protection must be provided when the store is relatively near any form of 
X-ray or gamma-ray sources. Further details regarding the protection of 
rooms may be obtained from the Radiological Protection Service, Clifton 
Avenue, Belmont, Sutton, Surrey. 

Atmospheric conditions 

The most important precautions to be taken when materials are to be 
kept for any length of time before exposure are protection against excessive 
humidity, large temperature variations, or high humidity combined with 
high temperature. Where large quantities of materials are involved and 
where the expense is justified, an air-conditioning plant may well be used; 
it is of particular benefit for the storage of infra-red and high-speed 
materials, which deteriorate more quickly than other materials. In 
general, it may be said that the faster a material, or the further 

* Formaldehyde, hydrogen sulphide, sulphur dioxide, ammonia, coal gas, mercury vapour, certain 
industrial gases, motor exhausts and vapour of turpentine and some solvents and cleaners. 

Issue A Kodak Data Sheet 

RF-6 



into the red or infra-red it is sensitized, the sooner it will deteriorate, 
other factors remaining constant. Relative humidity, ideally, should be 
40 to 60 per cent. The actual temperature matters much less: ideally it 
should be kept between 4 and 10°C (40 and 50°F) but this may be varied 
for different conditions and times of storage, according to the table below. 
More important is the maintenance of a reasonably constant temperature. 
Where a cold store is used, as may be essential in tropical or sub-tropical 
climates, materials should be removed several hours — preferably twenty- 
four — before the package is to be opened. This will prevent the conden- 
sation of moisture on the surface of the materials. 



De-humidifying treatment 

If materials, especially in opened packages, have been exposed to a high 
humidity for any length of time, it may be practicable to lower their 
moisture content adequately merely by taking them into a drier atmosphere, 
where they will usually reach equilibrium with the ambient air within 
twenty-four hours. Tightly coiled rolls and other forms of material 
where the air has difficulty of access may, however, take rather longer. In 
more serious cases where the material has a dangerously high moisture 
content it will be necessary to use some means of desiccation. The most 
useful desiccating agents are silica gel (8 to 20 mesh grade), rice or tea- 
leaves, and these may need drying out in an oven before use. The agent 
should be contained in a finely-woven air-permeable bag, but strict 
measures must be adopted to avoid contamination of the emulsion by dust 
particles. Calcium chloride, although generally satisfactory as a desiccat- 
ing agent, is not recommended because of possible chemical activity and 
its tendency to liquefy when saturated. 



Stockroom routine 

Where provided, the expiration date of packages should be noted; if 
none is shown, the date of receipt should be recorded by the store per- 
sonnel. The withdrawing system should ensure that the oldest materials 
are always issued first. Out-dated material, or material suspect through 
knowledge of previous storage conditions, should always be tested before 
use. 

All packages of film, plates or paper are best stored so that the material 
stands on edge. This is to obviate, as far as possible, the occurrence of 
pressure marks. 

Temperature and relative humidity 

It is important in all cases to process photographic materials as soon as 
possible after exposure; if delay is unavoidable, just as much care should 
be taken of the exposed material as of the unexposed. 

The table below shows the ideal recommendations for the storage of 
photographic films and plates. For papers, such strict measures are not 
usually necessary; if kept in a reasonably dry store at a temperature below 
21°C (70°F), papers will normally be found quite satisfactory. 

RF-6 2 



ATMOSPHERIC CONDITIONS FOR PHOTOGRAPHIC FILMS AND PLATES 



Type of Storage 


Temperature 


Relative Humidity 


Short-term 
(up to 3 months) 


Below 24°C (75°F) 


25-65 per cent 


Moderate-term 
(up to 6 months) 


Below I6°C(60°F) 


30-60 per cent 


Long-term 
(up to 12 months) 


Below 1 0°C(50°F) 


40-60 per cent 



It must be noted very strongly that, as well as causing loss of emulsion 
speed, alteration of inherent contrast and possible eventual waste, improper 
storage may also result in greatly increased fog and physical defects. 
Damage caused by unfavourable conditions, in most cases, cannot after- 
wards be made good. 

PROCESSED PHOTOGRAPHIC RECORDS 

As with unprocessed photographic materials, records must be kept 
under reasonable storage conditions if their life is not to be unduly 
shortened by the deleterious effects of heat, moisture and other factors. 
The following suggestions and recommendations are based on laboratory 
tests and experience and are made with the object of helping to preserve 
valuable photographic records. If followed they will reduce to a mini- 
mum any chance of deterioration brought about by climatic or storage 
conditions. They are made, however, without guarantee or warranty of 
any kind and do not apply to records on nitrate film base. 

If allowed to become too dry,records on film and paper become brittle and, 
if handled carelessly in this condition, will probably crack. Conversely, 
very high relative humidities can cause irreparable damage by mould 
growth and by sticking. Both high and low relative humidities, outside 
the limits set below, should be avoided. 

Three levels of permanence in records can be broadly assumed according 
to the estimated length of time that the records are required to be kept. 
The three levels have their associated recommendations for the pro- 
cessing and protection of records, and each is considered separately : 

Short-term permanence : where the requirements are that the records 
shall last for a few years. 



Moderate-term permanence: 
maximum of 25 years. 



where the anticipated life is up to a 



Archival permanence: where the records are required to last for an 
indefinitely long period, possibly hundreds of years. 

Short-term permanence 

Processing : In general, in temperate climates, no special precautions 
need be taken if the processing is carried out thoroughly. All records, 
whether on film, glass or paper support should be well fixed, preferably 
in two fixing baths, the second being fresh or almost fresh. Hardening, 
if employed, should be by means of an inorganic hardening agent and 



RF-6 



should be carried out before the washing stage. Washing should be 
equivalent to that obtained by 30 minutes washing at a temperature of 
20°C (68°F) in an efficient washing vessel, or for whatever time is recom- 
mended by the film manufacturer. The image may then be considered 
to be adequately permanent for this class of record in temperate climates; 
but in tropical or semi-tropical conditions it is recommended that more 
elaborate steps be taken to ensure the removal of residual silver and 
thiosulphate compounds, by the adoption of the processing recommenda- 
tions given for archival permanence. 

Protection From Fire and Water: Records on glass may be considered to 
be non-flammable while those on safety film or paper may be considered 
to be relatively non-flammable; the burning rate of safety film does not 
exceed that of ordinary newsprint paper. The use of fire-resistant cabinets 
or safes, however, is a valuable safeguard against damage to the film by 
external fires. Safety film will be buckled or blistered by excessive 
heat with such a cabinet or safe, but the film should be able to withstand 
a temperature of 93°C (200°F) for an hour or two. At 121°C 
(250°F) damage will occur; and at 149°C (300°F) the damage may be so 
severe as to render the records useless. Damage may also be caused 
by the generation of steam from moisture within the safe or cabinet. 

Obviously all records should be protected from the possibility of damage 
by water, whether from leaks, fire sprinklers or flooding of the floor. 

Chemical Contamination : The fumes of either hydrogen sulphide or 
sulphur dioxide can cause slow deterioration of records on any photo- 
graphic film or paper base, and gradual image fading of any photographic 
records. If present, such fumes should be eliminated, or an alternative 
store should be found free from such deteriorants. Dry-mounting 
methods are recommended if paper prints are to be kept in a mounted state. 

Temperature and Relative Humidity : In temperate regions normal room 
temperatures are, in general, considered satisfactory for the short-term 
storage of black-and-white negatives and prints; but with colour trans- 
parencies rather lower temperatures favour the preservation of the dye 
images. However, if a cold store is used, for any records, care must be 
taken to prevent the formation of moisture on a record when it is with- 
drawn for inspection or for copying purposes. This can be ensured by 
removing it, in its container, some hours — preferably twenty-four — before 
it is required for use. The control of the relative humidity, if this should 
be necessary, is of rather more importance than the temperature, but in 
temperate climates, if the store is well chosen, humidification or desiccation 
is unnecessary. Relative humidities within the range 25 to 60 per cent 
are permissible. 

Moderate-term permanence 

In addition to the recommendations covered in the previous section — 
Short-term permanence — the following additional points should be 
covered for the storage of records for up to 25 years. 

RF-6 4 



1 The residual hypo content of the image layer of records on film or 
glass base should not exceed 0.005 mg per sq in. No residual hypo 
should remain in records on paper base and, as this is impossible to 
achieve by washing alone, use must be made of a hypo eliminator such as 
the Kodak formula HE-1* 

2 A spot test, with sulphide, for residual silver compounds should give 
a negative indication.* This applies to all records whether on film, 
glass or paper base. 

3 Air conditioning, although not essential, is desirable; but where it is 
not possible an alternative is to condition the records to a relative humidity 
of between 25 and 60 per cent and then, if fluctuations outside this range 
are likely, to seal them within moisture-proof and air-tight containers. 

4 High temperatures must be avoided. 

Archival permanence 

Further recommendations are given below and these, in addition to 
those appropriate in the two preceding sections, must be stringently 
observed if records are required to last for a very long period. Only the 
best possible conditions are sufficiently good and inferior arrangements 
should not be considered. 

1 The storage space must be air-conditioned to give a relative humidity 
of between 40 and 50 per cent with a temperature in the range of 16 to 
27°C (60 to 80°F) but preferably near 21°C (70°F). 

2 The air should be filtered, and cleansed of acidic gases, and circulated 
under slight positive pressure. 

3 Records should be stored either in cans with loosely fitting lids, or 
individually in envelopes which must be of suitable type. The paper 
from which they are made must be free from any harmful compounds 
and preferably of a low hygroscopic tendency. The seams should be 
narrow and near the edge of the envelopes, and the adhesive used should 
be such as will not release acids or sulphur-compounds under the action 
of mould or bacteria. On the inside of the envelope there should be an 
overlap of 1 inch of paper beyond the glued area, and records should be 
inserted with the image side away from the seam. 

4 Records, either in cans or envelopes, should be kept in metal cabinets 
or drawers having louvres or other openings to provide free access of air. 
The cabinets or drawers must be placed within the storage space so as 
to allow free circulation of air around them. 

5 The containers of records, both cans and envelopes, should be stored 
so that the records stand on edge, and envelopes should not be stacked 
so tightly that excessive sideways pressure is introduced. 

6 Prints on paper base should be toned with selenium, sulphide or, 
preferably, with gold. 

7 If mounted prints are to be kept, the mounting boards should be of 
the best possible quality and the dry-mounting method should be used. 
Other adhesives usually contain some chemicals which may in time have a 
deleterious effect on the image. 

* Kodak formula HE-1 (Hypo Eliminator) and ST-1 (Residual Silver Test Solution), together with 
instructions for their use can be found in Data Sheet FY-4. 

5 RF-6 



SUMMARY OF RECOMMENDATIONS FOR 
PHOTOGRAPHIC RECORDS 


REQUIRED LIFE 


Short-term 
Permanence 
(A few years) 


Moderate-term 

Permanence 
(Up to 25 years) 


Archival Permanence 
{An indefinitely 
long period) 


RESIDUAL 
HYPO 


Low 


Must not exceed 
0.005 mg per sq in 


Must not exceed 
0.005 mg per sq in 


RESIDUAL 

SILVER 

COMPOUNDS 


Low 


Must give 
negative indication 


Must give 
negative indication 


RELATIVE 
HUMIDITY 


Preferably 
25-60 per cent 


25-60 per cent 


40-50 per cent 


TEMPERATURE 


Avoid high 
temperature 


Avoid high 
temperature 


I6-27°C 
(60-80°F) 


AIR 
PURIFICATION 


Usually 
unnecessary 


Desirable but 
not essential 


Essential 


AIR 
CONDITIONING 


Usually 
unnecessary 


Desirable but 
not essential 


Essential 



REFERENCES 

1 J. I. Crabtree, G. T. Eaton and L. E. Muehler, The Elimination of Hypo 
from Photographic Images, J. Phot. Soc. Amer., 6, Oct. 1940, pp. 6-13, 42. 

2 J. I. Crabtree, G. T. Eaton and L. E. Muehler, The Removal of Hypo 
and Silver Salts from Photographic Materials as Affected by the Composition 
of the Processing Solutions, J. Soc. Mot. Pict. Engr., 4 1 , July 1943, pp. 9-68, 

3 E. Lindgren, The Work of the National Film Library, J. Brit. Kinematgr. 
Soc, 8, Jan.-March 1945, pp. 13-22. 

4 Recommendations for the Storage of Microfilm, British Standard 
1153:1955, British Standards Institution. 

5 B. W. Scribner, Summary Report of Research at the National Bureau of 
Standards on the Stability and Preservation of Records on Photographic 
Film, National Bureau of Standards Miscellaneous Publication M162, 
May 1939. 

6 Storage and Care of Kodak Black-and-White Films in Rolls. Eastman 
Kodak publication AF-7. American Standard PH 5-4: 1970. 

7 American National Standards Institute. 

8 Storage and Preservation of Motion Picture Film. Kodak Motion 
Picture Leaflet MP-21. 



Kodak Data Sheet 
RF-6 



KODAK LIMITED LONDON 

PDRF-6/xWPI 1/2-71 



CHART TO DETERMINE EXPOSURE RATIOS FOR DIFFERENT LENS APERTURES 



1.2 



1.7 



2.4 



3.4 



4.8 



6.7 



9.5 



13.4 



19 



B 



1.4 



2.8 



5.6 



II 



16 



22 



22 



512 



360 



256 



180 



128 



90 



64 



45 



32 



22 



16 



II 



5.6 



2.8 



1.4 



19 



360 



256 



180 



128 



90 



64 



45 



32 



22 



5.6 



2.8 



1.4 



16 



256 



180 



128 



90 



64 



45 



32 



22 



5.6 



2.8 



1.4 



13.4 



180 



128 



90 



64 



45 



32 



22 



16 



II 



5.6 



2.8 



1.4 



II 



128 



90 



64 



45 



32 



22 



16 



II 



5.6 



2.8 



1.4 



9.5 



90 



64 



45 



32 



22 



16 



5.6 



2.8 



1.4 



64 



45 



32 



22 



16 



II 



5.6 



2.8 



1.4 



6.7 



45 



32 



22 



16 



5.6 



2.8 



1.4 



5.6 



32 



22 



16 



II 



5.6 



2.8 



1.4 



4.8 



22 



16 



II 



5.6 



2.8 



1.4 



16 



II 



5.6 



2.8 



1.4 



3.4 



5.6 



2.8 



1.4 



2.8 



5.6 



2.8 



1.4 



2.4 



5.6 



2.8 



1.4 



2.8 



1.4 



1.7 



2.8 



1.4 



1.4 



1.4 



1.2 



1.4 



Each of the letters at the top left-hand corner of the 
chart indicates a row and a column of f/ numbers as 
follows: — 



A— Exact half-stops between standard f/numbers. 
B — The scale normally used on most lenses. 



How to use this Chart — The figure obtained, by reading down a column and across a row, is the 
exposure ratio of the two f/numbers chosen. This ratio can then be used to 
multiply or divide a known exposure time according to whether the new 
f/number is a larger or a smaller f/number respectively. 



Example — reading down the f/16 column and across the f/5.6 row, a ratio of 8 is obtained. If the exposure at 
f/16 was x seconds, then the exposure at f/5.6 will be f seconds. If the exposure at f/5.6 was x 
seconds, then the exposure at f/16 will be 8x seconds. 



RF-7 



LENS APERTURES AND 
EXPOSURE RATIOS 



KODAK LIMITED LONDON Kodak Data Sheet 

Issue A RF-7 

PDRF-7/xWPI0i/3-70 



THE PREVENTION AND REMOVAL OF MOULD 
GROWTH ON PHOTOGRAPHIC MATERIALS 



All silver-gelatin photographic materials are adversely affected by high 
temperatures and high relative humidities. Of these two conditions, 
high relative humidity is more detrimental than heat. 

When materials, either monochrome or colour, are stored or kept for 
any length of time in an atmosphere having a relative humidity above 
60 per cent, there is a tendency for mould to grow on the emulsion 
surface or, with roll or sheet film, on the gelatin backing. Spores of 
moulds are found in the air everywhere, regardless of temperature and 
humidity. There are a great many varieties of moulds, and like plant 
seeds, the spores germinate and grow wherever favourable conditions exist. 

Whether or not anything can be done to correct for the effects of mould 
growth on materials depends upon the degree of the growth and whether 
it started to grow before or after exposure and processing. 

When mould grows on unexposed or unprocessed material, it leaves a 
pattern of filaments which shows up in the processed image. In the case 
of colour film, the areas which have been attacked by mould will generally 
show a change in colour, whereas in the case of monochrome materials, 
there will generally be an area of different density. It is impossible to 
correct for these changes. If materials are not properly protected before 
exposure, mould may grow inside the package or even inside a roll of film. 
If a material is partly used and left in a camera for some time in an atmos- 
phere having a relative humidity above 60 per cent, mould will quite 
frequently grow on it inside the camera. 

When the material is in a vapour-tight packing, there is practically no 
chance of any mould growth occurring before the package is opened. 
As soon as the package is opened, however, and a humid atmosphere has 
access to thematerial, mould growth may start to form. If material in vapour- 
tight packing is exposed and processed promptly, there are rarely any 
indications of mould growth before processing. If the processed material 
is subsequently sent to tropical climates, however, mould may develop. 

When mould growth occurs on processed material, the damage to the 
image is not so immediate, so that if its development is discovered in 
time, some steps can be taken to remove it and to prevent its recurrence. 
If the growth has gone too far, however, it may have caused permanent 
damage to the image. This is likely to be more serious with colour film, 
because the growth of mould may liberate substances which affect the 
dyes. With either monochrome or colour materials, mould growth may 
also etch or distort the gelatin of the emulsion or, with roll or sheet film, 
the backing. 

Prevention of mould growth 

The best method of protecting materials against mould growth is to 
store them in an airtight cabinet or container in which the relative humidity 
can be kept below 60 per cent. This can be done by using a desiccating 

Issue B Kodak Data Sheet 

RF-9 



agent such as activated silica gel. Silica gel lasts indefinitely, but it must 
be reactivated periodically to remove the absorbed moisture. This can 
be done by heating it at a temperature between 150°C (approx. 300°F) 
and 200°C (approx. 400°F) in a vented oven or over a fire. Heating 
for about 30 minutes is sufficient to reactivate small quantities of silica 
gel; larger quantities require 2 or 3 hours. 30 grammes (approx. one ounce) 
of silica gel is sufficient for about 50 colour transparencies in card 
mounts, about 200 feet of 16 mm film, or a total weight of about 120 
grammes of film negatives in storage envelopes. 

Some desiccation can be obtained within a metal storage cabinet of the 
type used for office supplies and records, by providing on the inside of 
the cabinet an electric socket in which a low-wattage lamp can be kept 
constantly burning. A 25-watt lamp, for example, is suitable for most 
cabinets, and the burning of this lamp will raise the temperature within 
the cabinet a few degrees, and by that means drop the relative humidity 
significantly. Temperatures inside the cabinet, on the shelves where the 
processed material is stored, should not be permitted to rise more than 
11°C (approx. 20°F) above the ambient room temperature. 

When desiccating agents are not available or convenient, considerable 
protection against mould attack is afforded by the ordinary principles of 
good housekeeping. For example, valuable negatives should be stored 
in such a manner that they are protected from dirt and dust and also 
protected from any insects that may be present. Furthermore, every 
effort should be made when handling the negatives to avoid leaving finger- 
prints, etc., on the surface, or to remove them immediately with 'Kodak' 
Movie Film Cleaner. Any form of surface contamination provides pro- 
tection for spores of moulds and encourages an initial growth of the 
mould itself. 

Removal of mould growth 

Neither water nor aqueous solutions should be used for the removal of 
mould. In the great majority of cases, mould growth on the emulsion 
causes the gelatin to become soluble in water, and the use of water or 
aqueous solutions would, therefore, lead to disintegration of the image. 

Films mounted in card mounts should be unmounted before cleaning, 
and their mounts discarded. 

The material should be cleaned by wiping it with soft plush, cotton- 
wool or chamois leather, moistened with 'Kodak' Movie Film Cleaner. 
This treatment should remove most of the surface mould growth. 

When the gelatin has become etched or distorted by the mould growth, 
no satisfactory method of complete restoration is known. If the mould 
is only in the gelatin backing of a film, it is possible to remove the backing, 
but the film may curl excessively as a result. 

Mounted films that have developed mould growths, and have been 
successfully treated, should not be remounted in their original cardboard 
holders, but after being dried thoroughly, remounted in new cardboard 
mounts or between glass. Although there may be a tendency for mould 
to grow on the inside surface of the glass, experience with large numbers 
of glass-mounted slides in the tropics has shown very little trouble. 
Kodak is a trade mark 

Kodak Data Sheet KODAK LIMITED 

RF-9 Printed in England 

YI3I3PDRF-9/XWPI4/4-73 




FLASH PHOTOGRAPHY 



The constant use of flash for subjects where low-level lighting conditions 
prevail or where the recording of high-speed action is essential, has 
brought about a simplification of flash exposure recommendations and 
of the use of flash equipment. However, it is still necessary to give some 
attention to the methods of exposure calculations so that correct exposure 
can consistently be achieved. The types of flash sources that are dealt 
with here are the expendable flashbulb and the electronic flash. 



EXPOSURE 

The following are important factors which will affect correct exposure: 

1 Size and light output of the flash source. 

2 Size, shape, and surface-finish of the reflector. 

3 Flash- to-subject distance. 

4 Lens aperture. 

5 Synchronization. 

6 Shutter speed. 

7 Speed of sensitized material. 

In practice, the product of the lens aperture and flash-to-subject distance 
is expressed as a guide number which can conveniently be used to calculate 
the correct exposure (guide numbers for flashbulbs with appropriate 
KODAK sensitized materials are given in their respective Data Sheets in 
the FM section). If all other factors remain constant, then the guide 
number may be used to calculate the flash-to-subject distance by 
dividing it by the lens aperture required. Conversely, the flash-to- 
subject distance may be used to calculate what aperture will be required. 

Further though slightly less important factors which must be con- 
sidered are the type of surroundings and the type of subject. Guide 
numbers are usually expressed for "average" subjects of medium tone 
or colour taken in a studio or large room with light-to-medium coloured 
walls which reflect only a moderate proportion of light on to the subject. 
Further exposure allowance can be provided. For example, if the 
subject is darker than average in colour, the general recommendation 
is that the aperture should be opened by half a stop more than that 
calculated; for lighter than average coloured subjects the aperture 
may be closed by half a stop. Still further exposure allowance will 
be necessary if the surroundings reflect little or no light on to the sub- 
ject, as in a large hall, dark studio, or outdoors, when the aperture 
may need to be opened by up to two stops. Conversely, for those sur- 
roundings which reflect a great deal of fight, as in small rooms with walls 
of light tone, the aperture may be closed by one stop. Of course, these 
"subject" and "surrounding" corrections may be combined, if necessary. 

Flashbulb guide numbers quoted for shutter speeds of 1/30 second 
are effectively open-flash guide numbers, and will be greater than those 

Issue G Kodak Data Sheet 

RF-8 



given for use at faster shutter speeds, during which a smaller proportion 
of the total light output is utilized — assuming that the same flash 
source is used in both cases. Correct shutter synchronization must be 
used to fully utilize the flash output of the bulb — see below. 

Correct exposure with electronic flash in the studio can best be calcu- 
lated with an electronic flash meter. Guide numbers are used with the 
small portable units. 

SYNCHRONIZATION 
Diaphragm shutters 

To utilize the full flash emission with a diaphragm shutter, it is necessary 
for the synchronizing device to arrange that the peak of the flash co- 
incides with the period during which the shutter blades are in the fully 
open position. Expressed in time, the average diaphragm shutter 
takes from approximately 2 to 5 milliseconds to open fully from the 
instant it starts to move, and approximately the same time to close. 
This does not take into consideration the small delay which exists be- 
tween the moment that the shutter release is operated and the shutter 
blades start to move. The length of time during which the shutter is 
in the fully open position will, of course, vary with the shutter speed 
selected. The two classes of synchronization commonly used are : 

X- Synchronization: No delay period. Electrical contact is made when 
the shutter blades are in the fully open position. 

M- Synchronization: With this type of synchronization there is a delay, 
after electrical contact has been made, of 16-17 milliseconds before the 
shutter blades are in the fully open position. The necessary delay is 
usually brought about by some mechanical means. 

The following table gives details of the types of flashbulb that can be 
used with the two camera synchronization settings, and also includes 
electronic flash. 

SHUTTER SPEEDS AND SYNCHRONIZATION SETTINGS 
FOR DIAPHRAGM SHUTTERS 





Flashbulb Class 




Synchronization 


MF 


M 


FP+ 
andFP 


S 


Flash 


X 


1/60 sec 
or longer 


1/30 sec 
or longer 


1/30 sec 
or longer 


1/15 sec 
or longer 


All Speeds 


M 


1/60 sec 
or shorter 


1/60 sec 
or shorter 


All 
Speeds 


1/60 sec 
or longer 


Not Suitable 



Focal-plane shutters 

The synchronization of focal-plane shutters produces special prob- 
lems, and is very much dependent on the design of the shutter. The 
camera manufacturer's instructions should be consulted for information on 
suitable shutter speeds for flash synchronization. At slow shutter speeds 



RF-8 



the first blind completely uncovers the image area before the second blind 
commences its travel and X-synchronization can be used. At faster 
shutter speeds the focal-plane blinds form a slit as they travel across in 
front of the focal plane and to obtain even exposure, a class FP bulb 
must be used with FP synchronization. 

X- Synchronization : The circuit is closed when the first blind reaches 
the end of its travel. Suitable for electronic flash and flashbulbs at slower 
shutter speeds, consult your camera instructions for precise information. 

FP- Synchronization : The circuit is closed 16 to 20 milliseconds before 
the first blind begins its travel. Suitable for FP bulbs at faster shutter 
speeds. 

REFLECTORS 

A very important factor affecting the amount of light reaching the 
subject is the size, shape, surface finish, and position of the flash reflector. 
Generally, a large reflector is more efficient than a small one, and a para- 
bolic reflector is more efficient than one which is shallow or dish-shaped. 
Additionally, a reflector with a highly polished surface will tend to be 
more efficient than one of the same shape and size with a satin or matt 
surface; similarly, a parabolic reflector, which has the flashbulb located 
at its focal point, is more efficient than one where the flashbulb is at any 
other position. A shallow, dish-shaped reflector tends to give a less 
concentrated beam of light along the reflector axis than does the para- 
bolic type, although a more even light may be achieved owing to the 
greater divergence of the reflected beam. When the intensity of light 
along the reflector axis is relatively strong, a "hot-spot" of light is 
produced. Properly designed reflectors take into account the size and 
position of the flashbulb relative to the reflector, and usually combine 
the characteristics of the shallow and parabolic types of reflectors so as to 
concentrate the light from the bulb without giving a hot-spot. Alter- 
natively, the surface of the reflector can be diffused sufficiently to give 
an even spread of light. Diffusing screens can also be placed over the 
reflector in cases where trouble may arise from a reflector giving local 
concentrations of light; one or two layers of clean white handkerchief, 
white paper tissues, or thin tissue paper may help to correct this, but at 
the expense of some loss of light. 

FLASH WITH COLOUR MATERIALS 

The details given in this Data Sheet apply equally to both monochrome 
and colour films. However, correct exposure is rather more critical with 
colour films than with monochrome films, and correct exposure of colour 
reversal films is somewhat more critical than with colour negative films. 
As an example, the latitude of under-exposure or over-exposure with 
'Kodachrome' II Film may amount to no more than plus or minus half 
a stop from correct exposure, but for critical work with 'Kodacolor-X' 
Film, while the under-exposure latitude is similar, the over-exposure 
latitude can amount to approximately 2 stops. 

As the brightness range which can be accommodated by colour films is 
usually somewhat less than that of monochrome films, a lower lighting 
ratio will usually produce a much better colour photograph. Very often, 

3 RF-8 



it is found that approximately 50 per cent more light is required to re- 
produce dark colours, such as dark blues and greens, correctly, than 
lighter skin tones. Conversely, lighter colours need less light in order 
to reproduce them as the eye saw them in the original scene. In order 
to reduce the lighting contrast, the use of extra light from more than one 
flash unit is especially valuable in order to lighten the darker colours, and 
to illuminate adequately the shadows and the dark areas of a scene. Light- 
ing contrast may also be reduced by the use of such techniques as 
bounced-flash, or bare-bulb flash — these techniques are described in 
further detail on page 7. 

One essential difference between the use of monochrome and colour 
films in flash photography is the care which should be taken to avoid 
reflections being thrown on to the subject from highly coloured objects 
outside the picture area, but surrounding the scene. With monochrome 
materials, these reflections are not usually important and, in fact, can be 
beneficial. With colour films, strong colour casts may often ruin an 
otherwise good picture. 

FLASHBULBS AND FLASHCUBES 

To a certain extent, the light output from a flashbulb is limited by its 
size. However, the light output can be controlled during manufacture 
by slightly varying the quantity or nature of the combustible material 
within the bulb. The nature and form of the filling, whether it be 
shredded foil or wire, affects the construction, performance, and most 
important of all, the length of time that the bulb will take to reach its 
maximum light output. The following flashbulb classifications are 
grouped according to the time they take to reach their peak output. The 
term "effective duration" means the time during which the luminous flux 
or luminous intensity is more than one-half of the maximum value. 
Flashcubes are small, square, plastic boxes, with transparent sides, each 
containing four small flashbulbs. Each flashbulb has its own, built-in 
reflector. The whole flashcube fits into a special socket on the camera or 
accessory flashcube holder. The bulbs contained in flashcubes are 
classified as MF. 





LUMINOUS FLUX/TIME CHARACTERISTICS 


CLASS 


Time-to-peak 
(milliseconds) 


Time-to-half-peak 
(milliseconds) 


Effective duration 
(milliseconds) 


MF (medium-fast) 
M (medium) 
FP+ (focal-plane) 
FP (focal-plane) 
S (slow) 


I3±3 
20±5 

30±3 


8±3 
I5±5 
I0±4 

I5±6 
20±3 


12 (approx.) 
15 (approx.) 
25 (minimum) 
25 (minimum) 
20 (approx.) 



Flashbulb circuits 

A reliable firing system for flashbulbs consists of battery and capaci- 
tor. It provides ample power, long battery life, and overcomes most of 
the troubles of high contact resistance associated with low voltage batteries. 



RF-8 



It is essential to ensure that where ordinary dry-cell batteries are being 
used as the power supply, the electrical contacts should be kept clean, even 
to the extent of rubbing the contacts with fine emery cloth or similar 
abrasive material. Regular cleaning will help to reduce the resistance of the 
flash circuit and will, thus, ensure that the batteries in use will provide 
the maximum power to fire the bulb, giving accurate synchronization and 
reducing the chance of a flash failure. 

MAGICUBES 

These are very much like flashcubes in construction but have a com- 
pletely different firing system. They can only be used on cameras 
specially designed for them. Such cameras have a firing pin which 
emerges from the camera and enters the magicube at the appropriate point 
in the shutter operation, so pushing aside a spring in the magicube and 
firing a percussion cap which ignites the bulb. 

Magicubes are not electrical in any way and are independent of problems 
inherent in low voltage battery circuits. At present their use is largely 
confined to relatively simple cameras such as KODAK pocket 'Instamatic' 
cameras. Because they are only used in cameras specially designed for 
them, magicubes have not been given flashbulb classification. 

ELECTRONIC FLASH 

Electronic flash units give a short duration flash, which is extremely 
useful for action photography or where short exposures are essential, and 
emit "daylight quality" light which compares very favourably with that 
of natural daylight illumination. 

It is not possible to describe here the enormous range of electronic 
flash units that is now available. 

The exposure necessary when using electronic flash depends on many 
factors, including the output of the flash tube and the way the light is 
used, e.g., in much studio work diffuse lighting is now used. A flash- 
meter is therefore the most practical way of determining exposure for the 
professional photographer. 

When using a flash head as a direct light-source, guide numbers 
established empirically or recommended by manufacturers may be used to 
calculate exposure. Where available, a flashmeter is a more reliable 
guide, especially when using colour reversal films which, by their nature, 
are less tolerant of over or under-exposure. 

Since, in most cases, the duration of the electronic flash is extremely 
short, altering the shutter speed has no effect on the exposure. However, 
where other strong light is present, such as sunlight, or bright modelling 
lights, the use of a fast shutter speed is recommended — especially if it 
is required to stop action. This technique will avoid double or "ghost" 
images which might otherwise be produced. 

When using certain monochrome negative materials, it may be found 
necessary to increase their developing times owing to the effects of 
reciprocity-law failure (see Data Sheet SE-1), which occurs with the 
very short flash duration of some of these units (especially the larger, 
studio units). The amount of increase in development is somewhat 
dependent upon the type of subject, as well as the type of flash unit and 

s RF-8 



its flash duration. Electronic flash has a characteristic softness (often the 
consequence of some form of diffusion introduced into the beam, e.g., 
a matted plastic screen or a facetted reflector) and a great many of the 
portable flash units are used close to the lens axis. When used thus the 
resultant contrast may be low, and some increase in the developing time 
may be necessary. 

Some electronic flash units give light of such a quality that the result- 
ant transparencies are rather too blue, even on daylight-balanced colour 
films. In this case, the use of a filter will help to improve the overall 
colour balance. Recommendations for filters for specific materials are 
given in the appropriate Data Sheets in the FM section. 

TECHNIQUES 
Open flash 

With interior work for example, where the light is very dim, the shutter 
can be opened while repeated flashes from bulbs or an electronic flash unit 
may be used to "paint" the subject with light. If the camera operator 
is working alone, this system may be used (providing there is little existing 
light) by closing the shutter or, preferably, using a lens cap over the 
camera lens between each successive flash. There are numerous 
situations where open flash can be used with existing light to obtain 
special effects, e.g., in the work-study field. 

Fill-in flash 

In bright sunlight, the lighting contrast is often too high, particularly 
with close-up subjects lit obliquely, or from the side or back. This 
contrast can be lowered, and a natural effect retained by the use of blue 
flashbulbs or electronic flash as a "fill-in" light-source. 

The following formula will enable a natural lighting ratio to be obtained : 

„. , , . .. 2\ x basic guide number 

Flash-to-subiect distance= — - — -. -, — 

aperture to be used 

Multiple flash 

Where it is found necessary to increase the level of flash illumination, 
more than one flash unit can be employed in the flash circuit. This is 
extremely useful where large areas have to be fit, such as in studio work, 
or where it is necessary to produce balanced lighting conditions for 
taking colour and monochrome photographs. 

Applying the same formula that is used for single-source flash, the 
guide number for the additional bulbs to be used (assuming that the bulbs 
are all of the same type and are used in identical reflectors) can be deter- 
mined by increasing the basic guide number by the square root of the 
number of bulbs to be employed, for example : 

2 bulbs : x 1.4 

3 bulbs : x 1.7 

4 bulbs : x 2 

The above rule applies only when the additional flashbulbs are used 

RF-8 6 



as the main source of illumination; it is not normally necessary to consider 
flash sources which are to be used only as background lighting or to 
reduce shadows. However, the safest method of judging exposure with 
multiple flash is to use a flashmeter. 

As may be expected, the use of the multiple-flash technique reduces 
the overall lighting ratio considerably; an advantage in colour photography. 
The use of modelling lights on flash units helps the arrangement of 
lighting, when using multiple flash, since the effects of the lights can be 
seen. 

Diffuse flash 

Many types of subject, ranging from fashion models to bright metal 
objects, require diffuse lighting. This is often achieved by the pro- 
fessional photographer using flash (usually electronic) and some diffusion 
technique, such as an "umbrella" or "tent". Many flash heads can be 
used simultaneously and a relatively high level of illumination attained. 

When such facilities are not available, a similar though less controlled 
effect can be obtained by bouncing the flash from a convenient, light-toned 
wall or ceiling. When using colour films, extreme care must be taken to 
avoid coloured reflections, however slight, which will produce a colour 
cast in the picture. If this technique is to be used frequently, a standard 
white card known not to produce a colour cast can be kept as a reflector. 

Exposure, when using bounced flash, is difficult to estimate without a 
flashmeter, but as a guide, when the flash is to be bounced from a ceiling 
of average height (approximately 2.4m [8 feet]), and the flash head held at 
about two-thirds of the total height of the ceiling, an increase in exposure 
of at least 2 stops over the direct technique may be tried. 

A diffuse effect can also be achieved when using a flashbulb, by the 
"bare-bulb" technique. In this case, the flashbulb's reflector is dispensed 
with and surrounding objects are used to reflect light on to the subject. 
When using this technique, the safety precaution of placing a clear plastic 
bag over the bulb should be taken. 

Determining accurate exposure with the "bare-bulb" technique may be 
even more difficult than with bounced flash and, if a flashmeter is not 
available, only experience and experiment will give the correct answer. 

Close-up flash 

When flash is used on the camera at distances closer than the minimum 
specified in the instructions, the system of using guide numbers for 
calculating exposure conditions becomes impracticable. 

The following exposure details for close-up flash apply chiefly to the 
use of flashbulbs. However, the principle may be applied successfully 
to the use of electronic flash units, but a full range of tests should be made. 

The use of flashbulbs at such short distances as those given overleaf, 
permits the use of small apertures with the advantage of an increased depth 
of field. Because of its position relative to the camera lens, the flash re- 
flector in use does not uniformly light an extreme close-up. It is there- 
fore suggested that when using this table, one or two thicknesses of 

7 RF-8 



white handkerchief, white paper tissues, or thin tissue paper should be 
placed over the reflector to act as a diffuser. When so covered, the diff- 
erences in reflector shape, size, and surface are reduced considerably. 
The table assumes the use of a properly diffused reflector, attached to, 
or in close proximity to, the camera, and a shutter speed of 1/30 second. 



FLASHBULB 


'KODACHROME' II 
FILM 


•KODACHROME-X', 'EKTA- 

CHROME-XVKODACOLOR-X' 

FILM 


AGIB/3B, PFIB, 


8-10 in 


12-14 in 


18-22 in 


8-10 in 


12-14 in 


18-22 in 


Type IB 


f/ll-16 


f/H 


f/8-ll 


fl 16-22 


f/16 


f/ll-16 



Flash extension 

Flash units attached to the camera are convenient for taking photographs 
spontaneously. However, this method poses its own lighting problems. 
Highly reflecting surfaces behind the subject may cause disturbing "hot 
spots" of light in the picture. Subjects placed close to the background 
will be framed by hard dark shadows, and the flat frontal lighting causes a 
lack of modelling. For these and many other reasons, flash is best 
used (where possible) away from the lens axis, and preferably at an angle 
and distance from the subject to improve the modelling and eliminate 
any unwanted reflections. The use of one flash unit on extension (at 
about 45° to the camera-subject axis) with a second flash unit attached to 
the camera, will in most cases, improve the results still further. 

Besides allowing improvements to be made in the modelling, and 
avoiding unwanted reflections, special effects are possible. By carefully 
arranging the flash unit, it may be used to simulate light from other 
sources, e.g., open fires, candles, etc. Provided that the light from the 
flash is reasonably frontal, the exposure can be calculated in the same 
manner as for normal flash exposures. 

Infra-red flash 

Infra-red or "dark" flash is used fairly extensively in press and forensic 
photography where normal visible flash photography is impossible, 
undesirable, or prohibited. 

Where monochrome negatives are to be made, KODAK High Speed 
Infrared Film may be used. It is essential to screen the flash source so 
as to ensure that only invisible infra-red radiation is transmitted; if any 
appreciable amount of visible light is transmitted, or is allowed to leak 
past the screen, the effect will be completely ruined. A suitable method of 
"filter-coating" flashbulbs is given in the paper by R. B. Morris and 
D. A. Spencer, Dazzle-free Photo/lash Photography, Brit. J. Phot., 87, 
14 June 1940, pp 288-289. Alternatively, use a KODAK 'Wratten' No. 
87 or 88A Filter over the flash reflector for either flashbulbs or electronic 
flash. 

Kodak, Kodachrome, Kodachrome-X, Ektachrome-X, 
Kodacolor-X, Instamatic and Wratten are trade marks 



Kodak Data Sheet 
RF-8 



KODAK LIMITED 

Printed in England 

Y 1 3 1 5PDRF-8/xWP 12/4-73 




THE DIMENSIONAL STABILITY 

OF PHOTOGRAPHIC FILMS AND PLATES 



The dimensional stability of photographic films and plates is an im- 
portant factor in many applications of photography; these include the 
reproduction of drawings and plans, topography and photogrammetry, 
microphotography, colour-separation work, many photomechanical 
techniques, and all other photographic techniques where the retention 
of size is important. This Data Sheet is intended to outline the reasons 
why films and plates change size, and to give a guide to the relative 
merits of the various supports used for photographic emulsions. 

FILMS 

Photographic film comprises a plastics base coated with a light-sensitive 
emulsion. This emulsion is normally a suspension of silver halides in 
gelatin, and the film is, therefore, a laminate of two chemically different 
materials, each of which is affected differently by environment and age. 
Consequently, the dimensional behaviour of film is extremely complex; 
for consideration in this Data Sheet the subject is sub-divided thus : 

1 Temporary or reversible dimensional changes — (a) humidity effects, 
(b) thermal effects. 

2 Permanent or irreversible dimensional changes — (a) processing effects, 
(b) ageing shrinkage. 

The magnitude of each of these types of dimensional change in a given 
film depends on the chemical composition and thickness of the base and 
emulsion, and on the treatment received during manufacture and subse- 
quent storage. There are also complex phenomena, such as hysteresis 
and elastic memory, which account for small dimensional changes. 

Two types of base are used for 'Kodak' films: 

1 Cellulose acetate bases, such as cellulose tri-acetate. 

2 'Estar' base: this is the Kodak trade-name for a thermo-plastic 
material known as polyethylene terephthalate which belongs to a class 
of materials called polyesters. 'Estar' base is stronger and more durable 
than acetate bases, and has much higher dimensional stability owing to 
the method of manufacture. It is commonly used for 'Kodak' graphic- 
arts films, aerographic films, X-ray films and general-purpose monochrome 
films. 

TEMPORARY OR REVERSIBLE DIMENSIONAL CHANGES 

The reversible changes of size are more likely to be caused by humidity 
than by temperature. This is partly because of the magnitude of the 
coefficients involved, and partly because the relative humidity of most 
laboratories and workrooms is more apt to vary than the temperature. 

Issue B Kodak Data Sheet 

RF-IO 



Humidity effects 

Humidity expansion or contraction of film is caused by a gain or loss 
of moisture from the air with which it is in contact, and the magnitude 
of the change depends on the chemical nature of the film. For any given 
film it is the relative humidity of the ambient air, and not its absolute 
humidity, which determines its moisture content and its corresponding 
size. After a change in the relative humidity of the air, the dimensions 
of a sheet of film exposed to it will change gradually for about one hour 
until equilibrium is re-established. 

Thermal effects 

Film, in common with many other materials, expands or contracts at 
different temperatures; such thermal size-changes occur rapidly, some- 
times in a minute or two. Frequently, an increase in air temperature is 
accompanied by a decrease in relative humidity, or vice versa, so that 
these two effects may partially cancel one another. Under other condi- 
tions, however, they may be additive. 




3= u 
a c 
o ai 



- 










- 




i, 






1 





Glass 'Estar' Base Triacetate 

(0.004 in thick) (0.005 in thick) 

Figure I 



Glass 'Estar' Base Triacetate 

(0.004 in thick) (0.005 in thick) 

Figure 2 



PERMANENT OR IRREVERSIBLE DIMENSIONAL CHANGES 
Processing effects 

Film swells during processing and contracts again during drying. If 
the film, after processing and drying, is brought to equilibrium with the 
same relative humidity and temperature as existed before processing, a 
small net change can generally be found. If the film is not brought back 
to the same conditions, the apparent processing shrinkage may be increased 
by humidity contraction and increase in temperature, or reduced by 
humidity expansion and decrease in temperature. 



RF-10 



Ageing shrinkage 

Permanent shrinkage during the storage period prior to exposure is 
generally very low and is unimportant because no image has yet been 
recorded on the film. At all times after exposure, however, film continues 
to shrink at a rate which in time gradually decreases under any given 
storage conditions. Where film is used within a week or two after 
exposure, shrinkage caused by the various ageing effects is of little practical 
consequence usually less than 0.02 per cent, unless the storage conditions 
are extreme. 



+ 0.1 - 



0.0 



-0.1 



-0.2 



-0.3 



-0.4 



-0.51 



Stored at 26° C (79°F) - 60%RH 



tsst-^- 



Stored at 32°C (90°F) - 90% RH 



Figure 3 

The first of the ageing effects, in the case of acetate bases, is the change 
brought about by the gradual loss from the base of solvents and plasti- 
cizers used in its manufacture. Polyester base contains neither solvents 
nor plasticizers and, so, this effect does not occur. Another of the effects 
is the plastic flow of the base caused by contraction of the emulsion; 
this can vary greatly with different emulsion compositions. This type 
of behaviour is true of all existing film supports but polyester base will 
show less of this plastic flow than the cellulose acetate types. The last 
of the three major ageing effects is the release of mechanical stresses and 
strains introduced originally during the manufacture of the base. 



RF-10 



Over long periods of time the amount of shrinkage must depend on 
the composition of the film, but storage conditions have certain effects 
and recommendations are given below for the minimizing of shrinkage. 
Heat is known to accelerate all three of the effects listed in the previous 
paragraph, so that elevated temperatures should be avoided. 

Both extremes of relative humidity may accelerate permanent film 
shrinkage. Low relative humidities cause a greater contraction of the 
emulsion, and this, in turn, induces a greater degree of plastic flow in the 
base. Conversely, high relative humidities facilitate the escape of any 
residual solvents and plasticizers. 

RECOMMENDATIONS TO MINIMIZE SIZE CHANGES 

Where the user of film cannot prevent large variations in atmosphere 
conditions, size changes can be greatly minimized by attention to handling 
details. 'Kodak' films are in equilibrium with air at approximately 45 
per cent relative humidity at the time of packing. However, some change 
in the moisture content of the unexposed film may occur, depending on 
the storage conditions, and it is unlikely that the film will be in equilibrium 
with the air in the workroom. Where the utmost in dimensional stability 
is required, the film, before exposure, should be conditioned to the air 
of the workroom by hanging up individual sheets of film, in the dark, for 
approximately 1 hour. Gentle circulation of the air is beneficial. Then, 
if the film is reconditioned in the same atmosphere after exposure and 
processing, the dimensional changes caused by changing humidity will 
be reduced. 

In colour work a moderate degree of dimensional change is often per- 
missible provided that all the colour separations change by exactly the 
same amount. In such cases, it is important that each sheet of film be 
treated in exactly the same manner from the moment the original package 
is opened. It is desirable for the conditions in the workroom to be 
similar to those in the storage room. If the relative humidity of the 
workroom is either low or high, the films should each be conditioned to 
room air, before exposure, as described in the previous paragraph. 

The provision of a properly controlled air-conditioning system is highly 
recommended. A temperature of 18-24°C (64-75T) and a relative 
humidity of 40-50 per cent are most satisfactory. Too low a humidity 
should be avoided as it increases the possibility of static. If the film 
becomes electrified, dust will adhere, and spots will appear on the film 
after exposure and development. Too high a humidity (more than 60 
per cent) is to be avoided because of the danger of mould growth, and 
other moisture defects, as well as the promotion of higher shrinkage. 

GLASS 

Since the earliest days of photography, emulsions have been coated 
on glass plates. With the introduction of flexible film base, the use of 
glass fell into disfavour owing to its bulk, weight, and brittleness. How- 
ever, glass has yet to be surpassed as a support for photographic emulsions 
in critical applications where dimensional stability is of paramount 

RF-10 4 



importance. For this reason glass plates are still used in astronomy, 
photogrammetry and topography, microphotography for producing 
micro-electronic devices, and some photomechanical techniques. 

DIMENSIONAL STABILITY OF GLASS PLATES 

Glass is the only material used as an emulsion support that is 
unaffected by humidity changes, and only extremely large temperature 
changes need ever be considered. Its humidity coefficient is nil (see 
Figure 1) and its thermal coefficient of linear expansion is only 80 X 10" 7 /C° 
(45xlO" 7 /F°). In this respect glass is superior to hardened steel and 
significantly better than the most stable film bases (see Figure 2). With 
glass, dimensional changes owing to temperature effects, if any, are truly 
reversible. 

DIMENSIONAL STABILITY OF THE EMULSION LAYER 

During processing, the wet emulsion layer swells vertically, but 
because of its firm attachment to the glass other dimensional changes 
are restrained. During the drying process, the lateral dimensions of the 
layer remain essentially unchanged, but the thickness may vary according 
to treatment. Thereafter, the layer does not change lateral dimensions 
independently of the glass. 

When using microphotographic plates, such as the H-R 'Kodak' 
High-Resolution Plate, for producing minute, accurate scales and 
graticules, or masks for micro-electronic devices, even these small pro- 
cessing changes can be objectionable. The following paragraph, 
reprinted from the book "Microphotography" by G. W. W. Stevens 
(Chapman and Hall, 1968) suggests means of minimizing these changes : 



"Prevention of Emulsion Distortion 

Although silver-halide-gelatin emulsions coated on glass normally 
reproduce the dimensions of the image printed on them with com- 
mendable faithfulness, there is some tendency for small distortions 
to occur, particularly when the plates are not processed correctly. 
Methods already suggested for preventing excessive swelling should, 
for most purposes, suffice to eliminate a harmful degree of distortion, 
but extra precautions can be taken when the dimensional stability 
of the image is particularly important. Distortion may occur in the 
rinse bath between development and fixation, as a result of the rapid 
rate at which the emulsion swells in this stage. This danger can be 
avoided by using a non-swelling stop-bath such as Kodak formula 
SB-4 . . . Another precaution, recommended by Cooksey and 
Cooksey for astronomical or spectroscopic photography, is to anneal 
the emulsion layer before exposure. They considered that the 
emulsion on factory-dried plates is in a state of strain, which can 
cause distortion when the emulsion is swollen. They released the 
strain by swelling the emulsion slightly in an aqueous-alcohol solu- 

RF-10 



tion, and dried slowly before exposure. This treatment was reported 
to lessen distortions substantially, but the risk of contaminating the 
emulsion surface makes such bathing treatments inadvisable for 
microphotography. Essentially the same result should be obtained 
without this risk by supporting the unexposed plates (emulsion-side 
down) over a dish of water for an hour or two. This permits the 
emulsion to swell enough to become quite plastic, without any 
liquid actually touching the emulsion surface." 



Distortion may occur during the final drying operation, when there 
is likely to be a rapid transition between swollen and unswollen emulsion 
within a distance of a few millimetres. This transition zone usually 
creeps across the emulsion surface, and is almost certainly associated 
with severe local stresses; for this reason, a safer technique for special 
purposes might be to pass the plate through solutions of ascending 
concentration of industrial spirit in water; 50 per cent, 75 per cent, and 
90 per cent of spirit by volume are suggested, with approximately 
5 minutes' soaking in each solution. At the final stage, so little water 
should be left in the emulsion that air drying should be quite safe. 



RF-IO 



BIBLIOGRAPHY 

J. M. Calhoun, The Physical Properties and Dimensional Behaviour of 
Motion Picture Film, J.Soc.Motion Pict. Telev.Engrs, 43, No. 4, 
Oct. 1944, pp. 227-266. 

A. A. Ray, Dimensional Stability of Sensitized Photographic Material, 
Photogr.J., 87B, No. 6, Nov.-Dec. 1947, pp. 135-136. 

J. M. Calhoun, The Physical Properties and Dimensional Stability of Safety 
Aerographic Film, Photogramm. Engng, 13, No. 2, June 1947, pp. 163- 
221. 

C. R. Fordyce, J. M. Calhoun, and E. E. Moyer, Shrinkage Behaviour of 
Motion Picture Film, J.Soc.Motion Pict. Telev.Engrs, 64, Feb. 1955, 
pp. 62-66. 

J. M. Calhoun, Technology of New Film Bases, Perspective, 2, No. 3, 
1960, pp. 250-256. 

P. Z. Adelstein and J. M. Calhoun, Interpretation of Dimensional Changes 
in Cellulose Estar Base Motion-Picture Films, J. Soc. Motion Pict. 
Telev.Engrs, 69, No. 3, March 1960, pp. 157-163. 

J. M. Calhoun, P. Z. Adelstein, and J. T. Parker, Physical Properties of 
'Estar' Polyester Base Aerial Films for Topographic Mapping, Photo- 
gramm. Engng, 27, No. 3, June 1961, pp. 461-470. 

P. Z. Adelstein and D. A. Leister, Non-uniform Dimensional Changes in 
Topographic Aerial Films, Photogramm. Engng, 29, No. 1, Jan. 1963, 
pp. 149-161. 

R. H. Brock and A. H. Faulds, Film Stability Investigation, Photogramm. 
Engng, 29, No. 5, Sept. 1963, pp. 809-818. 

P. Z. Adelstein and J. L. McCrea, Permanence of Processed 'Estar' Poly- 
ester Base Photographic Films, Photogr. Sci. Engng, 9, No. 5, Sept.- 
Oct. 1965, pp. 305-313. 

Dimensional Stability of KODAK 'Estar' Base Films for the Graphic Arts, 
Eastman Kodak Data Sheet Q-34. 



RF-10 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 
ESTAR 



Kodak Data Sheet KODAK LIMITED LONDON 

RF-IO 

PDRF-IO/axWPII/2-71 



STAINS APPEARING ON STORED 
MONOCHROME NEGATIVES AND PRINTS 



YELLOWING AND FADING OF NEGATIVES AND PRINTS 

The silver images of modern sensitized materials are remarkably stable 
when the material has been properly fixed, washed and stored away from 
excessive humidity and sulphurous gases. With poorly processed 
materials, however, storage for a few months in humid conditions may 
produce stains. 

Poorly fixed and inadequately washed negatives or prints may develop 
yellow-brown stains from the decomposition of silver thiosulphates to form 
silver sulphide. Prints may also exhibit yellow discoloration or toning 
of the lowest density of the image. This change, first noticeable in the 
highlights and popularly known as fading because the image becomes less 
visible, is produced by the action of thiosulphate on the silver image to 
form yellowish silver sulphide. 

Some of the factors which affect the degree of fading are the quantity 
of hypo or of silver compounds left in the image, and the storage tem- 
perature and humidity. The finer the grain of the material, the more 
readily it is attacked; thus, prints, which have very fine-grain images, fade 
much more readily than negatives. At room temperatures an image may 
not fade within 6 months, but at a temperature of 38°C (100°F), with high 
humidity, the same image may fade overnight. 

Silver sulphide may be formed in negatives or prints either as an area 
of stain or as a fading of the image. Silver sulphide stain owes its origin 
to an internal cause— the presence of unremoved silver compound. Fading 
of the image, with the conversion of silver to silver sulphide, may be the 
result of either internal or external causes or a combination of both. 
Internal agents are usually hypo and silver compounds left in the material 
from insufficient fixing and washing. External agents are sulphurous 
gases in the air, such as hydrogen sulphide, sulphur dioxide, etc. 

Preventive measures to minimize fading and staining 

The recommendations given in Data Sheet RF-6, The Storage of 
Photographic Materials and Photographic Records, should be followed 
according to the estimated length of time for which the records are 
required to be kept. 

With the paper envelopes used for storing negatives, the seam should 
be along the edge, and not in the middle of the envelope as fading is likely 
to occur where the seam is in contact with the image. 

When mounting prints the use of paste adhesives is best avoided. Most 
pastes are hygroscopic, and the presence of moisture tends to accelerate 
fading. Ordinary starch paste has very little tendency to cause fading, 
but for long-term permanence, dry-mounting tissue should be used. 

The fading of prints as a result of the action of external agents may be 
minimized by the use of a waterproof lacquer over the print surface, the 
use of dry-mounting tissue, and by gold, selenium or sulphide toning (see 
Data Sheet FY-6). 

Issue B Kodak Data Sheet 

RF-II 



Restoration of faded and yellow prints 

The removal of the stains, or the restoration of the image to its original 
colour, is frequently quite simple but may occasionally prove to be a 
complicated procedure. 

If the image is faded but there are no highlight stains, the bleaching and 
re-developing method, given in the Appendix, under formula S-6, will 
usually completely restore the print. In a severe case the following 
procedure should be followed. 

All dirt should be removed from the print by rubbing with an artist's 
quality rubber. Grease marks should be removed with benzene or petrol, 
and the print should be finally swabbed with industrial spirit. If the 
print is mounted, it should be detached from the mount, first by soaking 
thoroughly in water, then by placing it face downwards on a smooth 
surface and tearing the mount away from the print. If an attempt is 
made to pull the print away from the mount, the print will probably be 
torn. If the print has been dry-mounted, it should be heated in a dry- 
mounting press and stripped from the mount. 

The print should then be thoroughly fixed in plain hypo, to remove any 
undissolved silver halide, washed thoroughly, hardened by bathing for 5 
minutes in a solution made up according to formula SH-1, and 
again washed. Any stain in the highlights is probably silver stain, which 
should be removed in a 1 per cent solution of potassium cyanide, the print 
being removed as soon as the image begins to be attacked. Cyanide is a 
deadly poison and should be used with the greatest of care. * The 
print should then be thoroughly washed, and bleached and re-developed 
as indicated under formula S-6, in the Appendix. 

Removal of silver stain from negatives 

The above-mentioned cyanide treatment can be given, or a much less 
toxic bath, which has a preferential action on the stain, can be made from 
'Kodak' Rapid Fixer and citric acid. This is made up by mixing the 
Rapid Fixer, to the films and plates dilution, and adding citric acid in the 
proportion 1J ounces to each 80 fluid ounces (15 grammes per litre) of 
diluted solution. Only one negative should be treated at a time and it 
should be removed as soon as the stain disappears or if the image is 
attacked. It should then be thoroughly washed and dried in the usual way. 

Silver stains can be removed from dry negatives by mild abrasion. It is 
possible to remove the surface silver, without damaging the emulsion 
layer, by carefully rubbing the surface with a pad of cotton-wool 
moistened with a small quantity of Bluebell metal polish. 

MOUNTING STAINS 

Pink stains are frequently produced on prints which have been mounted 
with rubber cement. These are caused by the solvent action of the cement on 
the dyes present in the paper base or the mount. Also, some grades of 
rubber cement contain sulphur, which will tend to cause fading of the 

♦Caution — Prevention of contact with cyanide should always be ensured by wearing intact rubber 
gloves in good condition. It is essential to avoid exposure to cyanide fumes; therefore, cyanide 
solutions should never be used in conditions of poor ventilation. Acids coming into contact with 
cyanide result in the formation of highly poisonous hydrogen cyanide gas. When discarding a 
solution containing any cyanide, large quantities of water should be used to flush it out of the sink 
as quickly as possible. 

RF-II 2 



image. Other difficulties encountered with mountants include the transfer 
of iron from mountant to print, with consequent yellow rust stains, 
and the hygroscopic properties of the mountant, which cause the print to 
retain moisture and thus accelerate fading of the image. 

Removal of mounting stains 

Pink stains and a faded appearance can usually be eliminated by first 
removing the print from the mount as described above, and then by using 
the bleaching and re-developing method described in the Appendix. Iron 
rust stains may often be removed by soaking the print in a 10 per cent 
solution of oxalic acid. 

BROWN STAINS CAUSED BY SEAMS OF PAPER ENVELOPES 

Negatives stored in paper envelopes may develop yellowish-brown 
stains wherever they were in contact with pasted seams. Most pastes are 
somewhat hygroscopic, so that the negative tends to retain an excess of 
moisture in the region of the seams, a condition conducive to fading of the 
image. This is especially true of storage at high temperature and high 
humidity, and if the negative is not thoroughly washed. 

The stains may be prevented by the use of envelopes having seams only 
at the edge, and not in the centre, and having only a pure starch, dextrine, 
synthetic resin or shellac adhesive. It is also helpful to store the negative 
in the envelope with its emulsion side away from any seam. 

Removal of envelope seam stains 

Such stains can often be partially removed by the bleaching and 
re-developing method described in the Appendix, but usually the negative 
cannot be restored completely by this treatment. 

MOULD GROWTH 

Negatives or prints stored under humid conditions, even at moderate 
temperatures, may accumulate a mould growth. Full details regarding 
prevention and removal may be found in Data Sheet RF-9, The Prevention 
and Removal of Mould Growth on Photographic Materials. 

APPENDIX 

SH-l FORMALIN HARDENER 

Metric Avoirdupois 

10 ml ... . Formalin (40% formaldehyde solution) . . . 360 minims 

5 grammes . Sodium carbonate (anhyd.) 175 grains 

I litre . . . Water to make 80 fluid ounces 

S-6 STAIN REMOVER - Formula and Instructions 
Metric Stock Solution A Avoirdupois 

5.3 grammes . Potassium permanganate 185 grains 

I litre . . . Water to make 80 fluid ounces 

Stock Solution B 

75 grammes Sodium chloride 6 ounces 

16 ml ... *Sulphuric acid (concentrated) ... I fl oz 135 minims 

I litre . . Water to make 80 fluid ounces 

*Add the sulphuric acid slowly while stirring constantly. Never add the solution to the acid as the 
solution may boil and spatter acid on the hands or face, causing serious burns. 

3 RF-I I 



Use equal parts of A and B. 

In mixing Solution B, care should be taken to see that the sodium chloride solution 
is cool before adding the sulphuric acid slowly and with constant stirring. 

The material should first be hardened by immersion in a 5 per cent formalin 
solution for 2 or 3 minutes, followed by 5 minutes' washing. The image is then 
bleached, an operation which should be complete in 3 to 4 minutes at (20°C) 68°F. 
The brown stain of manganese dioxide is then removed by immersing the material 
in I per cent sodium metabisulphite solution. Then rinse well and develop in strong 
light with any non-staining developer, e.g., D-163. (Do not use a developer con- 
taining high sulphite and low alkali content, because the sulphite tends to dissolve 
the silver image before the developer can act on it.) 



Kodak is a trade mark 



Kodak Data Sheet KODAK LIMITED LONDON 

RF-II 

PDRF-ll/rlWPI/12-70 



THE VIBRATION INSULATION 
OF PHOTOGRAPHIC EQUIPMENT 

By courtesy of W. P. Fletcher, B.Sc, A.lnst.P., and Metalastik Ltd. 
Revised by A. R. Payne, B.Sc, A.lnst.P., A.I. R.I. , of the Rubber and 
Plastics Research Association of Great Britain. 



The ever-increasing use of photography as a tool of research and investi- 
gation presents to the photographer a number of new problems, some of 
which are far removed from optical science. One such problem arises in 
the production of photographs under conditions of mechanical shock or 
vibration, and this becomes more common with the present trend to larger 
and more powerful engines and production units in all types of industrial 
plant. The degree of resolution and definition of a photograph taken 
under such conditions is limited by the movement of the camera relative 
to the object during the exposure time, and hence in order to take full 
advantage of the potentialities of modern optical equipment and photo- 
graphic emulsions it is necessary to reduce such movement to the lowest 
possible value. Further, photographic equipment of a delicate type may 
sustain quite severe damage if subjected to any considerable mechanical 
vibration. 

Most textbooks deal with the elimination of vibration at the source, a 
course of action rarely possible in photographic work which has to be 
carried out under the conditions prevailing. ThisDataSheethas therefore 
been specially prepared to deal with the problem of insulating the camera 
and other apparatus from floor and wall vibrations. 

Mounting systems fall into three types : 

1 Those employing rubber; 

2 Those employing metal springs; 

3 Pendulum systems. 

Of these three classes, systems falling in the first are generally the most 
simple to design and construct. This class is therefore most fully con- 
sidered in this sheet. 

The use of rubber mountings 

Most problems of insulation against mechanical disturbance may con- 
veniently be solved by the use of mountings composed of natural or 
synthetic rubber. For the sake of convenience and stability, it is often 
bonded to metal. Such mountings may be obtained in a wide variety of 
shapes and sizes and in many different types of rubber, giving a range of 
stiffness sufficiently large for the solution of all problems normally en- 
countered. Mechanical disturbances are of two general types : continuous 
vibrations, hereafter referred to as vibrations, and transient shocks, here- 
after referred to as shocks. The properties of mounting systems needed 
to give maximum insulation against the two types of disturbances are not 
identical and thus it is necessary to consider which type predominates in 
any given case. Probably the more usual problem is that of insulation 

Issue A Kodak Data Sheet 

RF-12 



against vibration, and in general this allows of more accurate planning 
than shock insulation; a brief account is given below of the elementary 
theory of vibration insulation. 



Elementary theory of vibration insulation 

Suppose that from a floor vibrating vertically with an amplitude A m 
and frequency / hertz, it is desired to mount a piece of apparatus of 
mass M kg. If mountings are chosen such that the system has a vertical 
stiffness (where unit stiffness is the force required to cause a displacement 
of 1 m) of C N/m, illustrated diagrammatically in Figure 1, then the 
body on its mountings will have a natural frequency of vertical vibration 
n hertz, such that 




«=iV£ 



-2n 



•(1) 



It can be shown that under the 
above conditions the mass will take 
up a forced vibration of frequency 
/ (the same as that of the incident 
vibration) and of amplitude Af 
where 



Aj=A/(l- £) 



•(2) 



Now in order to gain advantage 
from the mounting system, it is 
necessary that Af should be less 
than A, which latter would be the amplitude of the body if it were fixed 



Figure 



rigidly to the floor. 



The ratio -J, the amplitude ratio, is given by 



4i 

A 



2-1/(1-^) 



n 2 



•(3) 



.A f . f 



A graph of the numerical value of -/ against - is given (Figure 4 full 

line), and this shows that in order to gain advantage from the mounting 

system (-/ less than 1) the value of - must be greater than \/2. 

A modification to the simple theory is necessary in order to take account 
of the fact that rubber is not a perfect spring material; its damping char- 
acteristics lead to a dissipating of energy by a type of viscosity effect when 
the material is subjected to vibrations. In consequence of this, the ampli- 
tude is modified as indicated by the dotted curve, Figure 4. In the region of 

f 
insulation (- greater than V2) the amplitude is increased slightly, thus the 

calculated degree of insulation is not fully achieved. No general expres- 
RF-12 2 



sion for the deviation from the simple theory can be given, since it varies 
with the type of rubber, but the deviation is not sufficiently large to cause 
real difficulty in the solution of normal problems. 



1.4 
1.2 
1.0 


| 






























.c 
u 

•E, 0.8 


1 










1 










DEFLECTION 

p 












\ 










fc 0.4 


\ 




















0.2 























5 10 IS 20 25 

RESONANT FREQUENCY (hertz) 

Figure 2 

Figure 2 shows the relationship between static deflection and resonant 
frequency for an undamped system that is supported upon isolators with a 
uniform stiffness. The effect of damping will be merely to cause a slight 
lowering of the resonant frequency for the same stiffness. 

The problem is further complicated by the fact that for any system there 
is not one but six resonant frequencies. These are illustrated conveniently 
in Figure 3, overleaf, which represents a rectangular unit mounted upon 
four isolators, the various modes being as follows : 

1 Vertical resonance. This is the only resonance that has been considered 
in the above discussion. 

2 & 3 Lower rocking mode in each of the two vertical planes. These are 
the modes in which the unit rocks about a horizontal axis below the plane 
of the isolators. 

4 & 5 Upper rocking mode in each of the two vertical planes. These are 
the modes in which the unit rocks about a horizontal axis above its centre 
of gravity. 

6 Rotational mode. This will cause the unit to oscillate about a vertical 
axis through its centre of gravity. 



3 



R.F-12 





SIDE VIEW 



Figure 3 



t 
A 



The rocking-mode resonances are dependent upon the ratio between the 
vertical and the horizontal stiffnesses of the isolators, the distance apart of 
the isolators in the direction perpendicular to the axis of rocking, and the 
radius of gyration of the unit about the axis of rotation. 

Practical application of the theory 

The following example illustrates the use of this method of calculation. 
The photographic laboratory in 
a power station was disturbed 
by a vibration of frequency 50 
hertz and in order to produce 
satisfactory photomicrographs, it 
was necessary to reduce the vibra- 
tion transmitted to the optical 
equipment. 

By using an ordinary dial gauge 
graduated in one-thousandths of 
an inch, it was found that the 
vertical component of vibration 
was by far the most troublesome, 
having an amplitude at least 20 
times that of any horizontal com- 
ponent. An examination of the 
work produced under these condi- 
tions led to the conclusion that 
this vertical component must be 
reduced by 80 per cent to give satisfactory results 

theory given above, we see that -£ must be ^ and Figure 4 shows that the 

required value of - is about 3, allowing for a small safety margin. 
n 

Thus n = J - = — = 16.7 hertz 



1 


i > 









i 








J 










j 


v \ 











' V 


.^ 






► i : 



Figure 4 



Reverting to the 



RF-12 



Equation (1) gives for the vertical vibration 
16.7 



= i v?~ 



2tt 20 
the mass being expressed in kilogrammes. 

Thus the mounting stiffness C=22x 10 4 N/m. 

If a system of four mountings is to be used, the stiffness of each mount- 
ing in a vertical direction must be 5.5 X 10 4 N/m. Since the horizontal 
components of vibration were negligible, it is not necessary to calculate 
the horizontal characteristics of the system, but in order to be perfectly 
safe on this account mountings should be chosen which have the calculated 
vertical stiffness (5.5 X 10 4 Njm) and have a horizontal stiffness of a similar 
value. 

The steps to be taken in the accurate design of a mounting system are, 
briefly : 

1 The incident vibration along the three axes must be known in amplitude 
and frequency. 

2 The insulation factors (amplitude ratios) necessary to reduce these 
amplitudes to the required low value are calculated. 

3 From the curve, Figure 4, the corresponding ratios of — are obtained. 

4 From equation (1), the stiffnesses of the mounting system in the three 
directions are calculated. These figures are taken as maximum stiffness 
values, and a set of mountings chosen such that the three stiffnesses are 
not greater than the calculated values. 

The limiting factors to the softness of the mounting system are, firstly, 
the ability of the mountings to bear the steady load of the equipment, 
secondly the amount of deflection due to this load which could be allowed 
without fouling any external parts, and thirdly the general stability of the 
system. As a general statement it can be said that such considerations 
cause little trouble except where incident vibration is of very low frequency 
(below 10 hertz). 

It is now necessary to consider the differences between shock and anti- 
vibration mountings, and in particular the difference between a typical 
vibration wave-form and that of a shock wave. Vibration usually has a 
wave-form of substantially constant amplitude consisting of one or more 
frequencies, which will for the most part be continuous. In a shock pulse, 
the wave-form is a transient of random frequencies. These two wave- 
forms are illustrated in Figure 5. 




kj/r - — 



Figure 5 

RF-12 



When dealing with a resonance of a mounted system upon its isolators, 
it is usual to refer to it as a "resonance of the isolators". While this is not 
strictly true it helps to prevent confusion when dealing with the resonances 
of component parts of the unit. 

The requirements for an anti-vibration mount are that when supporting 
its rated load, the resonant frequency is as low as possible, consistent with 
stability, in order to isolate the majority of the applied vibration, and that 
it should also be damped in order that the amplitude at resonance shall not 
build up to a damaging degree. If the isolators are required to protect 
equipment that is only subjected to frequencies at least 2 \ times that of the 
resonant frequency of the system, damping is unnecessary. However this 
case is very rare since usually vibration is caused by rotating machines, or 
similar items, that are required to accelerate through the resonant fre- 
quency while being brought up to their normal running speed. 

The curves shown in Figure 6 indicate the load-deflection characteristics 
of typical anti-vibration and shock-mounts. The energy that is absorbed 
by an isolator is equivalent to the area under the load-deflection curve. 
The shaded areas under each of these two curves are equal, and the maxi- 
mum force transmitted in this instance when the load is mounted upon 
the shock-mounts is S. It can be seen that, in this example, the maximum 
force A transmitted by the anti-vibration mounts is approximately three 
times that transmitted by the shock-mounts. However, a shock-mount is 
also an anti-vibration mounting but owing to being designed to operate at, 
usually, a higher resonant frequency, the isolation efficiency is not as great. 





DEFLECTION 



Figure 6 



DEFLECTION 



The mounting of a system from a pendulum orientated to give maxi- 
mum freedom along the line of maximum incident vibration, or by use of a 
ball-joint-suspended pendulum to give freedom along all horizontal 
directions, is effective in certain special problems. The lack of damping, 
as with metal springs, leads to long persistence of free vibrations once they 
are started, but an additional difficulty with a pendulum mounting is that 



RF-12 



no insulation is provided against vertical vibration and if these are en- 
countered a second system must be added to give the necessary insulation. 

The damping force can be obtained in various ways, of which the two 
simplest are the dry-friction and the dashpot methods. 
Dry Friction: This system has a number of disadvantages. Since the 
damping force is normally constant, when the vibration energy levels are 
low, and hence the total vibratory force between the support and the unit 
is low, the initial friction may be high enough to prevent any movement of 
the relative parts of the isolator and the unit will not obtain any protection. 
If the frictional force is kept low enough to allow movement at the lower 
energy levels, it will probably not be adequate to restrict the motion when 
the amplitude at the resonant frequency is high. Another practical dis- 
advantage is that the rubbing of the friction elements can generate high 
frequencies in a similar manner to those generated by drawing a bow 
across violin strings. 

The advantage of friction damping is that it is usually the simplest to 
apply and is not greatly affected by heat. 

Dashpot: This method of introducing damping is probably the most 
commonly known. In its simplest form it consists of a plate attached to 
the mounted unit and immersed in an oil-filled cylinder. 

The use of oil as a viscous fluid is only suitable in a relatively few 
applications, since the viscosity is greatly affected by temperature, and 
the design of a dashpot is usually such that unless a complex mechanical 
linkage is used, the freedom of movement is limited to one direction only. 

A variation of this theme is the use of air as the viscous damping medium. 
In the design shown in Figure 7 the damping force is derived from the 
movement of air through the small orifice as a result of the pumping 
action of the rubber balloon. This system has the advantage that the 
damping is unaffected over a wide temperature range, is light in weight, 
and has few sealing problems. 



ATTACHMENT POINT FOR UNIT 



LOAD BEARING SPRING 



Figure 7 

The flexibility of the balloon allows freedom of movement in all three 
planes. Owing to the ability of the rubber balloon to change volume 
slightly, without forcing air through the orifice, small excitation ampli- 
tudes will cause the isolator to operate as if it were undamped, thereby 

7 RF-12 



APPENDIX 



List of equipment manufacturers 

It should be emphasised that, if any doubt exists in the matter of the 
mounting of photographic equipment, advice should be asked of the manu- 
facturers of instrument mountings who are able, by reason of their 
experience, to suggest the best solution to any vibration problem, provided 
that full information is given to them. 

The following is a list of manufacturers of instrument mountings in this 
country; it should not, however, be regarded as comprehensive: 



Andre Rubber Co. Ltd. 



BTR Industries Ltd. 



Hook Rise, Kingston By-Pass, 
Surbiton, Surrey. 

Horninglow Works, 
Burton-upon-Trent, Staffs. 



Metalastik Ltd. or 

John Bull Rubber Co. Ltd. 



George Spencer Moulton & Co. Ltd. 
Rubber Bonders Ltd. 

Silentbloc Ltd. 



Evington Valley Mills, 
Leicester. 

Bradford-upon-Avon, 

Wilts. 

Cleveland Road 

Industrial Estate, 

Hemel Hempstead, Herts. 

Manor Royal, 
Crawley, Sussex. 



Kodak Data Sheet 
RF-12 



KODAK LIMITED LONDON 



PDRF-I2/HWP2/I2-70 



GENERAL TECHNIQUE 



CONTENTS EDITION 

GN-I Copying Photographs and Other Illustrations Issue £ 

GN-2 Copying Radiographs and Other Transparencies Issue D 

GN-5 Photography in the Tropics Issue D 

GN-6 Making Monochrome Negatives from Colour Issue D 

Transparencies 

GN-7 Methods of Increasing Emulsion Speed Issue A 

GN-I I Negative Quality Issue C 

GN-I 2 Underwater Photography Issue D 



Associated Data Sheets in this or other volumes or sections 

I, RF-3 Optical Formulae and Depth-of-Field Table 

I, RF-4 Scales for Determining Copying Factors 

I, RF-8 Flash Photography 

3, CL-7 Problems in Colour Photography 

3, CL-8 Colour Photography by Artificial Light 

3, CL-12 Colour Photographs of Signs, Lights, and Other Night 
Subjects 



Kodak is a trade mark KODAK LIMITED 

Printed in England 

Y 1 328PDDB-29/xWP 1 0/5-73 




COPYING PHOTOGRAPHS AND 
OTHER ILLUSTRATIONS 



EQUIPMENT 
Camera 

It is essential that the camera be of rigid construction to prevent 
movement of the lens and film relative to the original during the exposure. 
It should be capable of being focused over the required range of copying 
distances and preferably have provision for double extension, by bellows 
or extension tubes, to permit same-size copying. The ability to focus the 
whole camera makes copying at small ratios (1:1 and nearer) much easier. 
A ground-glass screen provides accurate viewfinding and focusing. A lens 
specially designed for copying is ideal but any high-quality anastigmat will 
give acceptable copies if stopped down (the amount of stopping down 
depends on the individual design of lens). The choice of film depends on: 

1 The purpose for which the copies are being made. 

2 The range of films available in any given size. 

3 The means of processing — individual exposures or film in rolls. 

Camera support 

Ideally, the camera should be purpose-built and firmly mounted on a 
track or column. A horizontal arrangement is easier to construct, but a 
vertical arrangement permits easier handling of the originals to be copied, 
especially books and large originals. 

For occasional copying, a suitable camera can be mounted on a tripod, 
and the original either attached to a wall or laid on the floor. A spirit 
level is helpful in levelling the camera. 

Copying easel 

The material to be copied must be supported so that it lies in a plane 
perpendicular to the camera axis and parallel with that of the sensitized 
material. This is necessary to keep distortion to a minimum. 

The simplest easel merely consists of a display board upon which the 
originals can be laid or pinned; it should be painted matt black 
to prevent the reflection into the camera lens of stray light from its surface. 
As originals will sometimes be found in a wrinkled or creased condition, 
a sheet of 6 mm (J inch) flawless bevelled glass (and suitable clips to hold 
it) should be available for covering them, or a large contact printing 
frame can be used. 

Books present a special problem, best met by a vertical copying arrange- 
ment; the matter to be copied can be held flat by a sheet of plate glass, 
while the facing page, covered with black paper to prevent stray reflections 
and bound to the cover with a rubber band, can rest at an inclined angle 
against a block of wood. Special care must be taken when photographing 
rare or old material. 

Issue E Kodak Data Sheet 

GN-I 



Lighting equipment 

Two lamps will normally be sufficient to provide even illumination 
unless the available space precludes their being placed sufficiently far back; 
in this case, four will be necessary, one at each corner of the copying board. 
If reflectors are used, those giving diffuse illumination are to be preferred 
to polished ones and they should be checked for evenness of illumination. 

Reflector lamps, either ordinary tungsten or one of the special photo- 
graphic types, are suitable. For high intensity, photographic quality 
light tungsten-halogen lamps are particularly useful. 

The colour-quality of the light of the lamps chosen should match the 
film being used, or else the light should be corrected for colour by a 
light-balancing filter over the camera lens. Electronic flash may be used 
with monochrome films, or colour films balanced for daylight. 

For details of 'Kodak' Films, refer to the respective Data Sheets. 

SENSITIZED MATERIALS (COLOUR) 









OTHER 'KODAK' 


LIGHTING 


'KODAK' MATERIAL 


DATA 


MATERIALS 


FOR COPYING 


RECOMMENDED 


SHEET 


WHICH MAY 
BE SUITABLE 


TUNGSTEN 


'Ektachrome' 

Professional Film, 
Type B (Process E-3) 








— (RollandSheetFilm) 


FM-ID 






'Kodachrome' II 








Professional Film, 








(Type A) — (35 mm) 


FM-2A 






'Ektacolor' Professional 








Film 6102, Type L 








(Sheet Film) 


FM-3 






'Kodacolor-X' Film 








— (Roll and 35 mm) 


FM-4A 






High Speed 








'Ektachrome' Film, 








(Tungsten) 








—(Roll and 35 mm) 


FM-IB 




DAYLIGHT- 


'Ektachrome' 






QUALITY LIGHT 


Professional Film, 
Daylight Type 
(Process E-3) 








—(Roll and Sheet Film) 


FM-ID 






'Ektacolor' Professional 








Film 6101, Type S 








— (Roll and Sheet Film) 


FM-3 






'Kodachrome' II Film, 




'Ektachrome-X' 




(Daylight) — (35 mm) 


FM-2A 


Film 




'Kodacolor-X' Film 




'Kodachrome-X' 




—(Roll and 35 mm) 


FM-4A 


Film 




High Speed 








'Ektachrome' Film 








(Daylight) 








— (Roll and 35 mm) 


FM-IB 





GN-I 



SENSITIZED MATERIALS (MONOCHROME) 

Monochrome continuous-tone copies require the use of materials of 
moderate contrast, while line copies require materials of extremely high 
contrast. Recommended materials are shown in the table below : 









OTHER 'KODAK' 


NATURE 


'KODAK' MATERIAL 


DATA 


MATERIALS 


OF ORIGINAL 


RECOMMENDED 


SHEET 


WHICH MAY 
BE SUITABLE 


CONTINUOUS- 


'Plus-X' Pan 




Commercial Ortho 


TONE 


Professional Film 4147 




Film 4180 ('Estar' 


Monochrome 


('Estar' Thick 




Thick Base) 


and colour 


Base)— (Sheet Film) 


FM-36 


—(Sheet Film) 
and 'Tri-X' Ortho 
Film 4163 ('Estar' 
Thick Base) 
—(Sheet Film) 




'Panatomic-X' Film 




'Verichrome' Pan 




—(Roll Film) 


FM-47 


Film— (Roll Film) 




'Panatomic-X' Film 




'Plus-X' Pan Film— 




(35 mm Film) 


FM-51 


(35 mm) 


LINE White background 


'Kodalith' Ortho Film 
3556, Type 3 
('Estar' Thin Base) 








—(Sheet Film) 


FM-30 






35 mm RECORDAK 








'Micro-File' Film 5669 


FM-58 






Fine Grain Positive 








Film (35 mm) 


FM-56 




Faded or yellow 


'Kodalith' Ortho Film 






background (using 


3556, Type 3 






'Wratten' 15 Filter) 


('Estar' Thin Base) 








—(Sheet Film) 


FM-30 






35 mm Recordak 








'Micro-File' Film 5669 


FM-58 




Blueprints (using 


'Kodalith' Ortho Film 






'Wratten' 25 or 29 


3556, Type 3 






Filter) 


('Estar' Thin Base) 








—(Sheet Film) 


FM-30 






'Kodalith' Pan Film 








2568 ('Estar' Base) 








—(Sheet Film) 


FM-30A 






35 mm Recordak 








'Micro-File' Film 5669 


FM-58 




Colour 


'Kodalith' Pan Film 
2568 ('Estar' Base) 








—(Sheet Film) 


FM-30A 






35 mm Recordak 








'Micro-File' Film, 5669 


FM-58 




LINE AND TONE, 


Process Film 4181 




'Panatomic-X' Film 


AND PENCIL 


('Estar' Thick Base) 




— (35 mm) and 




— (Sheet Film) 


FM-33 


35 mm RECORDAK 




'Verichrome' Pan Film 




'Micro-File' Film 




(Roll Film) 


FM-49 


5669 




Fine Grain Positive 








Film — (35 mm) 


FM-56 





GN-I 



THE ORIGINAL 
Treatment of the original 

A certain amount of treatment is possible even when the preparation of 
the original is out of the photographer's control. 

If necessary, clean the original with art gum. Repair defects, if this 
is possible without danger to the original but, if not, make a copy of the 
defective original suitable for re-copying, repair this copy and re-copy. 
Mount thin originals on smooth white card, or back them temporarily with 
heavy white paper unless the reverse side carries matter that may show 
through, in which case use black card or paper. Spot out any defects 
on photographs. 

Preparation of the original 

When originals are to be prepared especially for copying, the following 
points will enable copies of the highest possible quality to be obtained. 

Carbon-dust and Shaded-pencil Drawings: Draw the original on a larger 
scale than required for the copies. Ensure that the finest detail will still 
be visible on reduction; place lettering in open areas or where fine detail 
can be omitted. 

Line Drawings in Pencil or Ink: Copies of traces produced by recording 
instruments : draw on smooth white paper. 

Graphs, etc.: Ensure that co-ordinate squares are sufficiently large and of 
sufficient density to enable values to be read from the copies. 

Typewritten Matter : Type the original on one side of the paper only with a 
carbon ribbon, or without a ribbon through unused black carbon paper. 
Use a good-quality smooth paper, backed with a reversed sheet of new 
carbon paper. Always back thetypescript with whitepaper when copying it. 

Line Diagrams on or with Continuous-tone Photographs: Make the photo- 
graph with a severely restricted contrast and density range; use glossy 
paper but do not glaze it if the diagram is to be drawn on the print; 
if the diagram is white, print the highlight areas darker than usual; if 
black, print the shadows lighter. 

Photographs made especially for Continuous-tone Copying: The best prints 
for normal viewing of most subjects make use of the whole tone range of 
the paper, from practically clear white to the deepest attainable black. In 
such prints, the contrast in highlight details and the contrast in shadow 
details are less than the contrast in the middle tones. This is because use 
is made of the whole of the characteristic curve of the printing material 
and the highlight and shadow tones fall on the toe and shoulder of this 
curve. Such prints, when copied, exhibit the same lack of highlight and 
shadow contrast in the copy negatives. When one of these negatives is 
printed, a further compression of the highlight and shadow tones takes 

GN-I 4 



place, since use is again made of the toe and shoulder of the paper in 
the copy print. The final print is therefore obviously inferior to the 
original. 

To minimize this degradation of quality, a print specially made for 
copying (e.g., for photo-montage work) should be of low contrast; its 
highlights should be a light grey and its shadows should not reach the 
deepest black which the paper can yield. The tone rendering in the print 
will then be confined to the middle portion of the characteristic curve 
of the paper and all tones will therefore be recorded at about the same 
contrast. If then, by appropriate exposure, the copy negative also records 
these tones on the middle portion of its characteristic curve, the proper 
relationship between the tones is maintained, and with suitable processing 
such a negative will yield prints of very good quality, with practically 
as good highlight and shadow detail as the original print. In this final 
print the overall contrast should, of course, be such that use is made 
of as much as necessary of the available tone range. 

TECHNIQUE 
Illumination 

Important considerations in illuminating an original for copying are: 
even light distribution, control of reflections, and — in colour photography 
— the spectral quality of the light-source. 

Reflector-type photographic lamps or photographic lamps in reflectors 
are suitable for copying in both monochrome and colour. The proper 
filters must be used with colour films (see the Data Sheets on the respective 
colour films). Fluorescent tubes, closed carbon arcs, and mercury arcs 
are suitable for monochrome work only. 

Light distribution is much more critical in copying than in most other 
photographic work. The illumination must be quite even at the focal 
plane in the camera. With large, permanent copying arrangements, it 
is desirable to place the lamps so that all the corners of the largest original 
are equally illuminated, and possibly 25 per cent brighter than the centre. 
The need for higher illumination round the margin and corners of the 
original arises from the way in which light is distributed over the focal 
plane by the lens. The intensity in the focal plane from a uniformly 
illuminated original is highest at the centre, and falls off gradually the 
greater the angle from the lens axis. To ensure that all points on the film 
are within a desirably small angle, the lens-to-film distance should prefer- 
ably be twice the diagonal of the film format being used but never less 
than the diagonal. This precludes wide-angle copying. 

Reflectors producing a central area of great brightness (a " hot-spot ") 
should be avoided or else located so that the " hot-spot " covers the entire 
surface of the original. 

If a photo-electric exposure meter is available, use it to check the 
evenness of the illumination. Alternatively, use a visual photometer. 
The lighting can be tested by photographing a matt white card, equal 
in size to the largest original likely to be copied, on to the largest possible 
size of film (or paper of similar characteristics) of the highest contrast 

5 GN-i 



that will be used. Material for line copying should include a black 
character to check that the exposure level is correct. Inspection of the 
developed negative will indicate any changes which may be necessary. 






The angle between the lamps and the camera-subject axis should be 
arranged so that the conditions described above are fulfilled; an angle of 
45-60° will usually be found suitable. This arrangement avoids specular 
reflections from most smooth-surfaced originals. Other originals, having 
a lustrous rough surface, may need the lamps placed at a greater angle 
than 60° to the camera-subject axis, and further from the original to obtain 
even illumination. Provided that the light-sources are suitably large 
or diffuse, some rough-surfaced originals may be copied in this manner 
without the surface texture being shown up. These recommendations 
are intended only as a guide to a suitable arrangement; other originals 
may require different treatment. 

Once the lamp positions have been adjusted for best results, it is 
desirable to fix them for future use. The area of best light distribution 
with the usual two-lamp arrangement is wider than it is high, so a rec- 
tangular original should be placed with its longer dimension parallel with 
a line joining the two lights. 

Calculation of the exposure 

The exposure is best determined by experiment; a series of stepped 
exposures should be given on one sheet of film by withdrawing the 
slide completely and then replacing it 10mm (about \ inch) at a time; the 
exposures should differ from one another by a factor of 2. 

In the case of monochrome 35 mm and roll films this is impracticable, 
but the series of test exposures may be made on separate frames. With all 
forms of colour film, it is either impracticable or uneconomical to make 
test exposures on the colour film. In this case test exposures should be 
made on a monochrome film of suitable speed and contrast (such as 



GN-l 



Kodak 'Plus-X' Pan Film), and related to the exposure required for the 
particular colour film, using a pre-determined exposure correction. 

When the exposure has been found for one particular set-up, the correct 
exposure for other conditions can be found from Data Sheet RF-4 or by 
comparing the relative effective brightness of the subjects, as indicated 
by a photo-electric exposure meter, or preferably, by an exposure photo- 
meter. Whichever method is adopted, allowance must be made if the 
lens-subject distance is less than, say, 1 metre (or 3 feet), as in such a case the 
indicated relative aperture of the lens (i.e., the //number) is no longer 
effective. The effective //number is the indicated //number multiplied 
by (Af+1) where M is magnification, i.e., the image width divided by 
the subject width. The exposure time must be increased accordingly. 

When the distance of the lamps from the subject is changed, the follow- 
ing approximate formula will indicate the new exposure : 

Known exposure x (new distance) 2 

Required exposure = — 

(old distance) 2 

The efficiency of the lamps used, the tonal range of the subject and the 
speed and other characteristics of the sensitized material employed are 
other variables that must be taken into account when a change in technique 
is made. 

Processing (monochrome) 

Two distinct techniques are indicated, dependent on whether con- 
tinuous-tone or line copies are required; for the former, sensitive materials 
of moderate inherent contrast should be given normal development, while 
for line copies, materials of high inherent contrast should be used and 
processed in a more vigorous developer. 

Recommended developers and developing times for various materials 
are given in the appropriate Data Sheets indicated in the tables on pages 
2 and 3. 

Judging quality (monochrome) 

A correctly exposed and processed copy negative of a continuous-tone 
subject should be similar in appearance to a normal direct negative, and 
detail should be visible in both highlights and shadows. 

In a good line negative, black regions of the original should be repro- 
duced as clear areas, free from "veiling", while the areas representing the 
white portions of the original should be as dense as possible. Even the 
finest lines should be clearly visible when the negative is placed in contact 
with white paper and viewed by reflected light. 

Corrective treatment (monochrome) 

Line negatives that have been somewhat over-exposed show slight 
veiling in the areas that should be clear. This can be decreased by treat- 
ment with a reducer (see Data Sheet FY-5 for Kodak formula R-4a or 
R-4b). 

7 GN-l 



PHOTOGRAPHS FOR PHOTOMECHANICAL REPRODUCTION 
(MONOCHROME) 

To preserve as far as possible the quality of the original photograph 
in reproductions by photomechanical methods, prints should be made 
on Kodak Bromide or 'Bromesko' Papers (glossy surface), using Kodak 
D-163 Developer (see Data Sheets PP-9 and PP-10). The photograph 
should preferably be dry-mounted on to heavy, perfectly smooth cardboard 
to minimize accidental surface reflections. 

Never use paper clips on original photographs. 

COPYING COLOURED ORIGINALS 

The foregoing remarks apply in the main to the copying of black-and- 
white originals, but colour is essential to many drawings, charts and maps. 
When these are to be copied in monochrome, it is frequently necessary 
to maintain a tonal differentiation between areas of different colour in the 
original. If the colours themselves vary sufficiently, it is satisfactory to 
make the copy negatives on panchromatic material with a filter which will 
give a monochrome rendering approximating to the visual effect. 

If the colours are all of similar visual brightness, they can be separated 
on the copy negatives by the use of contrast filters. Thus, with a diagram 
drawn in red and green inks of equal luminosities, a green filter, Kodak 
'Wratten' Filter No. 58, will suppress the green ink and accentuate the 
red ink. Further information will be found in Data Sheet FT-1. 

USE OF COLOUR FILM 

'Kodak' colour films, in common with other colour films, are not 
capable of recording every colour with precise accuracy, but depend 
upon a mixture of the three complementary colours to simulate other 
colours. For this reason, the accurate rendering of colours depends to 
some extent upon the reflection characteristics of the pigments used in the 
original. For example, two greens that appear visually to be identical may 
record differently because they reflect the colours of the spectrum in 
different ways. In preparing coloured originals, therefore, only those 
pigments should be used which have been proved capable of affording 
satisfactory copies. 

The white backgrounds of some originals record with a blue cast; this 
may be due to the paper used having an unusually high ultra-violet 
reflectance, and can be minimized by photographing through a Kodak 
'Wratten' Filter No. 1A. 

COPYING RADIOGRAPHS 

The copying of radiographs and other transparencies involves certain 
special considerations which are indicated in Data Sheet GN-2. 

Kodak and product names printed thus — 'Ektachrome', Recordak 
— are trade marks 



KODAK LIMITED 

Kodak Data Sheet Printed in England 

GN-I YI307PDGN-l ( xWPI5/4-73 




COPYING RADIOGRAPHS AND 
OTHER TRANSPARENCIES 



Although this Data Sheet refers specifically to the reproduction of 
radiographs, the recommendations made apply, with some modifications, 
to the photographic reproduction of any continuous-tone transparency. 
The recommendations are based on radiographs, since they are the most 
difficult type of transparency to reproduce. Moreover, they are a type of 
transparency frequently requiring reproduction. 

Copies of radiographs can be made in several ways using monochrome 
materials, or by the use of reversal colour film (see page 7). 

COPYING WITH MONOCHROME MATERIALS 

In order to convey as clear a picture of the technique as possible, it is 
necessary to define the terms used in this Data Sheet. The original 
radiograph is a shadow picture of the subject, the densest portions of 
which appear as transparent areas and the least dense as relatively opaque 
areas. Any direct reproduction of this in which the tonal relations are 
reversed, produced either in the camera or by contact printing, will be 
called a "reversed-tone radiograph" or "intermediate positive". From 
this a "copy radiograph" may be made having the same tone values as the 
original; this is sometimes loosely called a "facsimile", though a paper 
print can rarely be a true facsimile of a transparency for reasons given 
overleaf, and even a transparent reproduction is not usually a perfect 
facsimile. Figure 1 shows an illustration of a radiograph. 

As the chief problem in reproducing radiographs lies in the production 
of suitable paper prints from which half-tone blocks are to be made for 
illustrations, this aspect is dealt with most fully in this sheet. Radiographs 
may be reproduced as positives made directly by contact or reduction 
from the original radiograph, but, since the tonal relations will be reversed, 
this may handicap interpretation. For this reason, reproductions in the 
negative image, made via an intermediate positive or by direct reversal, 
are generally preferred. 'Microdak' Panchromatic Film has been designed 
specifically for the production of miniature copies of radiographs. As 
well as having an emulsion of extremely fine grain and high resolving 
power, it has a very long exposure scale which will accommodate the wide 
range of densities which are normally found in radiographs. Further 
details of this film are given in Data Sheet FM-61. 

Photographically speaking, the detail of a radiograph consists only of 
variations in the density of the silver deposit; from this point of view, 
radiographs vary in two respects : 

1 The contrast, or extent of the scale of tones. 

2 The density, or degree of opacity, of the areas transmitting the least 
fight yet still containing some detail. 

Figure 1 indicates the characteristic tones: A, dense areas devoid of 
detail; B, the darkest areas in which detail is visible; C, the lightest areas 

Issue D Kodak Data Sheet 

GN-2 



exhibiting detail and even lighter areas showing no detail. B and C are the 
critical areas in the process of reproduction. The effective contrast to be 
considered is the density difference between B and C; if this is great The 
radiograph has high contrast. It is due to the inherent high contrast of 
the majority of radiographs that the problem of preparing satisfactory 
copies, especially on paper, becomes rather difficult. In a normal radio- 
graph, C may easily transmit 1000 times as much light as B; this has to be 
reproduced as a paper print which can only have a much more limited range, 
the white parts of the image rarely reflecting more than 50 times the light 
reflected by the blacks. The detail in high-density areas B, must be 
recorded in the intermediate positive without over-exposing the areas of 
low density, such as C, sufficiently to obliterate detail in them. Therefore, 
a material having great exposure latitude must be selected. In addition, 
it is necessary to compress the density range of the intermediate positive so 
that it may be reproduced satisfactorily as a print; this is done either by re- 
ducing the developing time (which lowers the contrast of the resulting 
image) or by means of local variation in exposure during printing (so-called 
"dodging"), which will be discussed later. 




Figure I . Illustration made from a radiograph of the chest in facsimile-tone reproduction 
(i.e., negative image). This shows examples of the areas to be considered in copying 

radiographs. 

A — Dense areas devoid of detail. 

B — Darkest areas in which detail is visible. 

C — Lightest areas in which detail is visible. 



GN-2 




rO — — — 0-| 


K-1-" 1 


LB 




— 15± — 



SIDE ELEVATION 




Figure 2. Diagram of a copying stand based on the use of a half -plate view camera. 

Note that the camera must be rigidly attached to the sliding carriage; the tripod socket 

of the camera can be used for this purpose. 

Making the reversed-tone radiograph or intermediate positive 

Equipment : The ideal camera for copying purposes is one fitted with a 
long bellows extension and ground-glass focusing screen or a miniature 
single-lens-reflex camera with extension tubes or a bellows attachment. 
However, the great majority of hand cameras will be found satisfactory 
for occasional work, although they usually require the use of a supple- 
mentary lens and some care in avoiding parallax error when framing. 
When using a supplementary lens, the camera lens must be well stopped 
down to ensure adequate sharpness over the whole field of view. The 
camera must be perfectly rigid during the actual exposure; if only a few 
radiographs are to be copied at irregular intervals, a sturdy tripod or stand 
is sufficient, but where many are to be copied, a special camera stand is 
desirable. A plan which can be adapted for practically any type of camera 
is shown in Figure 2. Additionally, special copying stands are available 
for the various brands of single-lens-reflex camera. 

With any form of camera an ordinary X-ray illuminator will be found 
satisfactory provided that the radiograph is evenly illuminated, and that 
illuminated areas beyond the edges of the radiograph are masked off to 
prevent flare in the camera. The Tndustrex' X-ray Illuminators are 
particularly useful in this connection, as they are fitted with adjustable 
metal shutters to screen off the non-image-forming light emanating from 
the surrounding illuminated area when radiographs smaller than 14 x 17 
inches (35x43 cm) are to be copied; this avoids the necessity for cutting 
special masks. 

Technique : The radiograph is first placed on the illuminator in the cor- 
rect position for interpretation. In some cases focusing may be found 
easier if the radiograph is mounted upside down so that the image seen on 
the focusing screen is the correct way up. The visible margins of the 
glass should be covered with an opaque mask, and the exposure made in 
a darkened room to prevent reflections from the surface of the radiograph. 
The camera is placed with the centre of the lens aligned with the centre of 



GN-2 



the radiograph, and the sensitized material parallel to the radiograph; if it 
is not strictly parallel, distortion will occur. It is as well to make all 
intermediate positives at the largest scale possible with the camera in use, 
thus automatically arranging that all radiographs of the same size will be 
copied at the same degree of reduction. 

When the camera has been placed correcdy, the image is brought into 
focus on the ground glass. Many non-reflex miniature cameras, not fitted 
with ground-glass focusing attachments, permit the temporary insertion of 
a small piece of ground-glass in the focal plane of the camera; focusing in 
this manner is accomplished before the camera is loaded. Note that the 
ground side of the glass must be toward the lens. The nature of a radio- 
graph is often such that focusing is difficult unless an object with a clearly 
defined edge, such as a strip of black paper, is temporarily held against it in 
close contact; a low-power magnifier, such as a reading glass, will help in 
obtaining critical focus. 

The lens of the camera must be perfectly clean, otherwise the foreign 
matter on the lens will scatter the light and cause a veiling of the image, 
with consequent obliteration of fine detail. 

The correct exposure time is chiefly determined by the surface bright- 
ness of the illuminator and the actual density of areas such as B in Figure 1 ; 
it is best determined by trial. Under-exposure should be avoided at all 
costs, for an under-exposed intermediate positive will be badly lacking in 
detail; over-exposure tends to "block-up" detail in low-density portions 
of the original, but is a lesser evil than under-exposure. 

When the correct exposure has been determined for any radiograph 
under certain conditions, all other radiographs having the same density in 
the densest area in which detail is visible can be given the same exposure. 
It is thus possible to accumulate a series of radiographs, the exposures for 
which have been determined by test, to act as a guide in estimating expo- 
sure times. When making exposure trials, the exposure should be either 
doubled or halved in each succeeding test, as smaller changes do not 
produce sufficiently marked differences. 

Adjustment of Radiographic Contrast : The simplest way of altering the 
contrast in copying a radiograph is by varying the length of development 
given to the intermediate positive. By developing the positive made from 
a high-contrast radiograph for a relatively short time, and that from a low- 
contrast radiograph for a relatively long time, it is possible to produce 
two intermediate positives of about the same printing quality. In cases of 
extreme contrast, this difficulty may be overcome by changing to a de- 
veloper of lower contrast, such as 'Kodak' Soft-Gradation or D-165 
developer. 

When, however, a radiograph exhibits an extremely long density range 
in which there are details of diagnostic importance in areas of both high 
and low density — B and C, Figure 1 — it may prove impossible to produce 
a good intermediate positive without special precautions. This difficulty 
occurs most frequently in industrial radiography and in such cases it may 
be preferable to take a further original radiograph of lower contrast. This 
may be attained, for instance, by an increase in voltage or by the use of 
niters or blocking media. Full details of these techniques will be found 

GN-2 4 



in the standard works on industrial radiography. 1 - 2 If it is impossible to 
make such modifications in making the original radiograph, variations in 
exposure must be given over the area of the radiograph in making the 
intermediate positive. The simplest method consists of exposing in the 
ordinary way until the point is reached at which more exposure would 
"block-up" detail in areas such as C, Figure 1. Additional local ex- 
posure is then given to areas such as B by means of a black cardboard 
mask, twice the size of the radiograph, with a small hole (e.g., a 1 inch 
(25 mm) circle) cut in the centre; this mask is held parallel and close to 
the radiograph and moved about continuously so that light from all the 
area requiring local exposure can pass through the hole, while no image is 
formed of the hole itself. It should be remembered that this operation 
must be undertaken in a darkened room. 

" Dodging " procedures, such as that just described, are not always easy 
to perform satisfactorily, especially where the areas concerned are small or 
of awkward shapes. A contact-printing method has been suggested by 
Thorpe and Davison 3 for carrying out local control of exposure, auto- 
matically, by means of a mask fixed to the radiograph. It is obvious that 
if a radiograph were masked with a suitable positive transparency of the 
same view through a perfect specimen, the defects shown in the radiograph 
would stand out clearly against a background of even density. This is, 
of course, impossible in practice but a similar result can be obtained by 
making a positive transparency of correct contrast from the negative 
radiograph by contact and placing this in register, but slightly out of con- 
tact, with the radiograph; the intermediate positive is made from this com- 
bination. This has the effect of giving general masking only, leaving 
defects in the specimen clearly visible. In practice, the mask is made by 
contact printing on to any suitable film, which is then developed in 'Kodak' 
Soft-Gradation or D-165 developer to a rather lower contrast than the 
radiograph itself, fixed and washed. This mask, when dry, is held in 
register with the radiograph but spaced from it by a sheet of glass about 
1/16 inch (1.5 mm) thick. This combination is then copied by contact. 
As the mask is diffused by its displacement from the radiograph, exact 
registration is not required and there is no risk of a double image. 

Sensitized materials 

The material to be used for making the intermediate positive or reversed- 
tone radiograph must be capable of recording a long range of densities; 
if miniature sizes are to be used, it must also be of very fine grain and 
capable of reproducing fine detail. 

The following materials are recommended : 
Sheet film: 'Tri-X' Ortho* (Data Sheet FM-35); Gravure Positive* 

(Data Sheet FM-32); Tlus-X' Panf (Data Sheet FM-36). 
Miniature film : 'Microdak' Panchromatic Safety Film* (Data Sheet 

FM-61); Fine-Grain Positive* (Data Sheet FM-56); 'Panatomic-X't 

(Data Sheet FM-51); 'Plus-X' Panf (Data Sheet FM-52). 
Roll film: 'Panatomic-X'f (Data Sheet FM-47); 'Verichrome' Panf 

(Data Sheet FM-49). 

* For radiographs and other monochrome originals. t Particularly for coloured originals. 

5 GN-2 



Processing : The contrast of the intermediate positive should be con- 
trolled by adjustment of developing time; processing should be as 
recommended in the Data Sheets describing the specific material used. 

The above procedure should give an intermediate positive of satisfactory 
quality, although experience alone will enable the operator to tell when this 
has been achieved. The positive should show every detail present in 
the original radiograph and yet provide adequate contrast. 

Where a positive image is considered satisfactory as an end in itself, it 
may be produced either by the above technique, or, if the contrast of the 
original negative radiograph is sufficiently low, by direct contact printing 
or projection printing on to smooth glossy bromide paper, using suitable 
"dodging" control if necessary. 

Making the copy radiograph 

The preparation of a copy radiograph from a good-quality intermediate 
positive is relatively simple. The methods which may be employed are 
these : 

1 Contact printing, using a printing frame or box. 

2 Projection printing, using an enlarger. 

3 Photographing the intermediate positive in the same way as that in 
which it was itself made. 

The choice of method depends largely on the type and size of copy 
radiograph required. 

Projection slides must be made on a sensitized material capable of 
recording faithfully the detail present in the intermediate positive, and 
yet providing adequate contrast. Several materials are recommended, 
the choice being governed largely by the method to be used in making the 
copy radiograph: 35mm Fine-Grain Positive Film, 'Tri-X' Ortho or 
Process Sheet Film. 

For making copy radiographs for viewing on an illuminator in the 
ordinary way, 'Tri-X' Ortho or Gravure Positive Sheet Film is recom- 
mended. 

These films should be developed in Kodak D-76 developer; Fine- 
Grain Positive Film in 'Kodak' D-163 developer, diluted 1+3 (for 
lower contrast, 'Kodak' Soft-Gradation or D-165 developer should be 
used). For formulae see Data Sheet FY-2. Because the contrast of 
the intermediate positive determines the contrast to which the copy 
should be developed, developing times are not given here; they should be 
determined by trial. 

Judging Quality : It is as well to make a series of test transparencies from 
which the one exhibiting the correct qualities can be selected as a guide for 
future work. If, on inspection, a transparency is found to be unsatis- 
factory, it should be borne in mind that greater or less density can be 
obtained by increasing or decreasing the exposure, and greater or less 
contrast by increasing or decreasing the developing time. 

Transparencies for projection are normally inspected for quality on an 
illuminator, the surface brightness of which is usually much greater than 
that of the illuminated surface of a projection screen, so that a satisfactory 

GN-2 6 



transparency for projection will appear slightly under-exposed and defi- 
cient in density and contrast when viewed on an illuminator. When 
many slides are to be made as a routine operation, the work of judging the 
quality can be facilitated by reducing the brightness of the illuminator. 
As a final check, it is as well to project the finished slide on a screen under 
normal viewing conditions. 

Making negative-image paper prints 

Contact prints and enlargements are best made on smooth glossy 
bromide paper, using D-163 developer, diluted 1 part to 3 parts of water. 
This paper is available in a range of contrasts, of which either WSG.l 
(soft) or WSG.2 (normal) will usually be found suitable. 

'Kodak' Radiograph Duplicating Film 

The preceding method for copying radiographs is capable of producing 
copies of the highest quality to meet a wide range of requirements. How- 
ever, the time, equipment, and skill it requires is often a deterrent to its 
use. As an alternative, medical radiographs and industrial weld radio- 
graphs can be copied quickly and surely, at same size, by using 'Kodak' 
Radiograph Duplicating Film. This is coated with a direct-positive 
emulsion which reproduces the tones of the original radiograph in one 
step without the need for reversal processing. Radiograph Duplicating 
Film can be processed in the same solutions as X-ray film, either manually 
or in automatic processors such as the 'Kodak' Medical or Industrial 
'X-Omat' Processors. Full details of handling and processing are given 
in Data Sheet FM-24. 

COPYING WITH REVERSAL COLOUR FILMS 

When darkroom facilities are not available, or for other reasons, it 
may be convenient to make slides of radiographs using a reversal colour 
film, which can be processed by one of the commercial processing 
laboratories or by the user. 

A 35 mm single-lens-reflex camera, fitted with close-up lenses or 
extension tubes and slow shutter speeds, can be used with High Speed 
'Ektachrome' Film (Daylight). This can be employed in conjunction with 
an 'Industrex' X-ray Illuminator, Model 2, which is a convenient apparatus 
for providing even illumination and a means of masking the radiograph. 

Transparencies made using this technique have a cyan cast, but this can 
be adjusted to the blue cast typical of radiographs by using a 'Kodak' 
Colour Compensating Filter CC30M over the lens. 

Exposures should be determined experimentally, but 1/8 second at //l 1, 
when using the system described, is a basis for a radiograph of average 
density. 



GN-2 



REFERENCES 

1 J. A. Crowther (editor), Handbook of Industrial Radiology, Arnold, 
2nd edition, 1949. 

2 W. J. Wiltshire (editor), A Further Handbook of Industrial Radiology, 
Arnold, 1957. 

3 S. H. Thorpe and D. W. Davison, Improved Methods of Printing 
from Radiograph Negatives, Engineering, 157, 31 Mar. 1944, pp. 241-242. 

BIBLIOGRAPHY 

C. G. Brownell, Making Copies of Radiographs, Med. Radiogr. Photogr., 
27, No. 4, 1951, pp. 114-121. 

H. L. Gibson, Copying Radiographs with Miniature Kodachrome Film, 
Med. Radiogr. Photogr., 27, No. 4, 1951, pp. 125-128. 

H. L. Gibson, Copying Radiographs with the New Kodak Colour Films, 
Med. Radiogr. Photogr., 38, No. 3, 1962, p. 117. 

P. Hansell & R. Ollerenshaw (editors), Longmore's Medical Photography, 
Focal Press, 8th edition, 1969. 



Product names quoted thus — 'Kodak' — are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

GN-2 

PDGN-2/xWPI3/IO-69 



PHOTOGRAPHY IN THE TROPICS 



INTRODUCTION 

Photography in the tropics is complicated mainly by the fact that high 
temperatures and humidities are unfavourable to the life and performance 
of all sensitized materials and of some types of apparatus. Furthermore, 
these conditions in turn favour the growth of moulds on organic matter. 
The ravages of insects may prove a menace, whilst airborne sand or dust 
may also present serious problems. The following account is intended to 
summarize many of the precautions which have been suggested for mini- 
mizing these troubles. 

Tropical climatic conditions fluctuate between wide limits but in general 
two main types may be encountered. The first is characterized by high 
and widely varying temperatures, which may rise to 50°C (122°F) in the 
shade, accompanied by low relative humidity, and may persist for long 
periods during the " dry season " or in desert regions. The second type 
occurs, for example, in the rainy season or on tropical islands and is 
characterized by a very high humidity with temperatures which do not 
often rise above 35°C (95°F). The precautions to be observed during 
the hot, dry conditions of the first type are relatively simple, but pre- 
cautions additional to these must be taken in very humid conditions. 

It should be realised that great variations of temperature, humidity, or 
other complicating factors may be encountered even within one of these 
main types of condition. 

In attempting to give general guidance for all such areas, it is inevitable 
that these notes may give a rather exaggerated impression of the difficulties 
to some users and a barely adequate one to others. Photographers must 
therefore use their own discretion in judging to what extent these notes 
may be applied and at all times should make the fullest possible use of the 
local information available from others with special experience in their 
particular area. 

SUMMARIZED RECOMMENDATIONS 

1 Keep apparatus dry and as clean as possible. Treat leather parts with 
wax polish, keep metal parts lightly greased and clean the lens surface 
frequently. 

2 Avoid leaving apparatus in the sun unnecessarily, especially if it 
contains sensitized material. 

3 If sensitized materials are ordered from suppliers in temperate 
climates specify that they are for tropical use so that they can be chosen 
and packed suitably, preferably in as small units as possible. 

4 Keep sensitized materials in the manufacturer's containers as long as 
possible. Once open, use the contents quickly, or alternatively, dry out 
the residue and reseal the container. 

Issue D Kodak Data Booklet 

GN-5 



5 At all times keep sensitized materials as cool and dry as possible and 
avoid sudden temperature variations. Where cooling facilities are 
available films and plates are best kept below 16°C (60°F), papers not 
above 21°C (70°F), ideal relative humidity 40 to 60 per cent. Under 
difficult conditions, keep storage temperature below 32 C C (90°F) if 
possible and avoid damp. Prolonged holding at 38°C (100°F) is very 
undesirable. Photographic materials cannot be depended upon to survive 
a temperature continuously maintained at 50°C (122°F) for more than a 
few weeks. In general, at all temperatures, the higher the humidity the 
more rapid the deterioration. 

6 Use the recommended exposure tables as a basis but be guided by 
local experience. Choose any exposure meter carefully. Note that a 
common fault in tropical photography is under-exposure. 

7 Develop as soon after exposure as possible. If delay is unavoidable, 
take just as much care of the exposed material as of the unexposed — keep 
it in dry containers and keep it cool. 

8 Keep processing solutions cool. If this is not possible, at least avoid 
sudden temperature variations from one bath to the next. Try to 
minimize swelling of the emulsion layer at all stages in processing. 

9 If, under field conditions, thorough fixing or washing is impossible, dry 
the negatives and prints and then re-fix or re-wash when more favourable 
conditions are available. For maximum permanence, use a hypo- 
eliminator bath as a final step after washing; the permanence of prints may 
be greatly improved by toning with hypo-alum or selenium, and they may 
also be varnished. 

10 Before final drying, treat negatives in a solution of zinc fluosilicate.* 

11 Store negatives and prints in cool, airy and fairly dry conditions; 
dampness is dangerous, but extreme dryness is also to be avoided, 
particularly where paper prints are concerned. Inspect negatives and 
prints periodically for signs of deterioration, so that corrective treatments 
can be applied or reproductions made. 

HANDLING AND STORAGE OF PHOTOGRAPHIC APPARATUS 

If treated with care, practically any camera may be used in the tropics 
for a short time. Cameras which are to be used in the tropics for long 
periods may require to be thoroughly cleaned, and moving parts must 
be lubricated with the correct oils; the manufacturer or a reputable 
camera repairer should be consulted. 

If a camera becomes very hot, this may not only spoil any film it con- 
tains but may also tend to soften the lens cement. Subsequent mech- 
anical strain produced by jarring or rapid cooling may cause "starring" 
of the lens cement which, at best, can only be rectified by the lens manu- 
facturer. Cameras should therefore never be allowed to lie in the open 
sun and should be kept in a case, preferably dust-tight, when not actually 
in use. The use of a white slip cover with non-corrodible metal fastenings 
has also been suggested for preventing overheating if cameras are used 
continuously for long periods. 

* Zinc fluosilicate and its solution are toxic and should be used with great care. 

GN-5 2 



Particular care should also be taken of lenses, since they are more 
likely to be contaminated with airborne grit under tropical conditions. 
External surfaces should be covered with a lens cap whenever a lens is not 
in use. Lenses may also be protected during use by a coloured filter, or 
a 'Wratten' No. 1A ('Kodak' Skylight) filter when using colour films, or 
by a piece of optical glass in a filter mount when no filter is required. 
This is particularly useful in deserts where much sand is to be contended 
with and also on the coast as a protection against salt spray. If damaged, 
such a filter can be replaced far more cheaply and readily than a lens. 
In maintaining outer lens surfaces clean, loose dirt and grit should as far 
as possible be removed by blowing or gentle tapping. If the lens surface 
requires wiping, cotton-wool or open-mesh fabrics such as butter muslin 
should be employed. Used with great care, these pick up the dirt particles 
without scratching the glass. If necessary the cotton-wool or fabric may 
be slightly moistened with 'Kodak' Lens Cleaner, water, or a solvent 
such as petrol or alcohol. The lens should be wiped finally with a dry wad. 

Fine dust, silt or sand will penetrate through any openings there may 
be in the apparatus. If cameras are to be used in dusty or sandy areas, 
they should be protected so that the dust cannot enter the shutter or 
diaphragm mechanism. One way of protecting such parts is to cover, 
where practical, any cracks or openings with pressure-sensitive tape. 

Certain insects may attack such materials as wood, fabrics, leather, and 
glue, and appropriate precautions should therefore be taken when neces- 
sary. 

High humidities, encouraging corrosion, have a harmful effect on many 
materials used in the construction of photographic apparatus. Moulds 
may attack leather, fabrics, stitches in cases and straps, glues and gelatin 
(including photographic sensitized layers, and filter and safelight filters), 
wood and even the glass surfaces of lenses. Metal parts, particularly if 
they consist of unprotected steel or aluminium, are liable to corrosion 
Thus, cameras and other apparatus unless constructed of materials 
resistant to tropical conditions should be protected from high humidities, 
at least when not actually in use. Parts held together by glue should be 
avoided, but some synthetic adhesives are less likely to be affected. 
Most modern cameras, without bellows, of a type constructed mainly of 
light metal or plastics, are very suitable for tropical use. The air space 
in such cameras is almost hermetically sealed, and if of the type where 
the lens is permanently extended and the front cell focused by a helical 
movement, diffusion in or out of the camera air space is greatly retarded. 
Thus, if such cameras are loaded under conditions of low humidity it is 
probable that the time taken for high humidities to affect the film will be 
appreciably lengthened. Even when such a camera is loaded at a high 
humidity the total amount of moisture available for the emulsion to 
imbibe is strictly limited. Only the first few exposures, therefore, are 
likely to be affected. 

Between-lens shutters are to be preferred to those of focal-plane type 
since the latter tend to cause trouble as a result of warmth, humidity, and 
airborne grit. Condensation of moisture on the lens may prove trouble- 
some if the camera is brought suddenly from a cool place into a hot, humid 

3 GN-5 



atmosphere. Any such condensation should be carefully wiped off 
before use or before returning the camera to its case. The above con- 
siderations also apply in general to darkroom apparatus which is, however, 
unlikely to be exposed to any such extremes of atmospheres or such 
rapid changes of humidity. 

As electricity will often not be available, the photographer intending to 
do his own processing may often have to use such light-sources as oil 
lamps or electric torches in the darkroom for safelights and as exposing 
lamps. The extra speed of bromide paper compared with that of chloride 
may be invaluable when making even contact prints under such conditions. 

Filters and safelight filters which are quite satisfactory for use in temp- 
erate climates have been known to break down rapidly under tropical 
conditions. Available from Kodak Houses are modified types which 
are much more resistant. The prospective user should therefore always 
mention that any filters or safelight filters ordered are required for use 
in the tropics. 

Most of the troubles due to high humidity mentioned above may be 
prevented by storing apparatus at lower humidities. Small articles such 
as miniature cameras can well be carried in airtight metal boxes containing 
a desiccating agent. The use of these is described on page 7; they are 
suitable for the storage or transport of a variety of equipment provided 
that the relative humidity can be reduced to a value less than 65 per cent. 
Alternatively, apparatus may be kept in a store, cabinet, or box main- 
tained a few degrees above the temperature of the outside air, thus 
reducing the relative humidity. This can be done by using continuously 
burning electric lamps, or an electrical heater, in the bottom part of the 
cabinet. The number and wattage of the lamps should be adjusted 
to keep the temperature about 6°C (10°F) above the average prevailing 
temperature. Air spaces and small holes should be provided at the top 
and bottom of the cabinet and small holes through the shelves, to allow 
a slow circulation of air to carry off any moisture introduced by the 
equipment. The positions of the holes should be staggered on the 
different shelves in order to obtain a more thorough circulation of air. 
Such a heated store should not be used for sensitized materials. 

The effect of humid conditions may also be lessened by frequent 
inspection and cleaning of apparatus, and by frequent airing. Treatment 
with a wax polish has also been advocated for discouraging the growth of 
moulds on leather bellows and other parts. Any stitching on straps and 
cases should be inspected frequently. The thread may rot without 
showing any external signs and such frequent testing is the only method 
by which to avoid an accident. 

SENSITIZED MATERIALS 
General considerations 

When ordering sensitized materials for use in the tropics several points 
should be kept in mind. Many sensitized materials are manufactured 
today with the emulsion hardened to suit tropical conditions, but when 
ordering materials direct from the manufacturers in a temperate country, 
the fact that they are intended for tropical use must always be emphasized. 

GN-5 4 



The selection of sensitized materials will generally be guided by the 
purpose for which they are needed. In the case of monochrome films 
for 35 mm or other miniature cameras, however, fine-grain emulsion is 
particularly recommended to minimize the increase of graininess which is 
likely to occur when processing is undertaken at above 24°C (75°F). 
The packing of materials for tropical use is of paramount importance 
and various forms of humidity-proof packing are used by photographic 
manufacturers. As explained below, once the humidity-proof packing 
is open, the materials are liable to undergo deterioration, which may be 
more or less rapid according to the prevailing conditions. Materials 
should therefore be ordered in as small units as possible. 

Deterioration under tropical conditions 

Either high temperatures or high humidities are bad for photographic 
materials. Photographic sensitized materials deteriorate when kept at a 
high temperature, but the velocity, and to some extent the nature of the 
changes, are so dependent on the humidity that two separate sets of con- 
ditions may be distinguished as follows : — 

1 The materials are kept in a humidity-proof container at a low relative 
humidity. 

2 The humidity-proof container is opened and the material is exposed 
to the high humidity conditions which occur for varying lengths of time 
in most tropical countries. Under this heading we may also include 
exposure to the atmosphere when working near salt water. 

Under the conditions of I, most photographic materials show a gradual 
rise of fog accompanied by loss of speed in the case of high-speed, low- 
contrast materials, and a rise of speed and a loss of contrast in the case of 
high-contrast, low-speed materials. These changes become increasingly 
rapid as the temperature is raised. Six months' keeping of 35 mm 
films in the original humidity-proof tins at a continuously maintained 
temperature of 32°C (90°F) has been suggested as a safe limit. If main- 
tained at 38°C (100°F), the life of most sensitized materials is measured 
in weeks, while some materials, such as infra-red film, break down even 
more rapidly at this temperature. At a temperature continuously main- 
tained at 50°C (122°F) all materials have a fife of only a few weeks or 
even days. These rough estimates of the maximum safe periods may no 
doubt appear rather conservative when compared with practical experience, 
but it must be remembered that they are expressed in terms of continuously 
maintained temperatures and not in terms of mean day temperatures only. 

Under the conditions of 2, the rate of deterioration at elevated tempera- 
tures is greatly accelerated and is characterized by latent-image fading after 
exposure, as well as by rise of fog and reduction of speed before exposure. 
It has been shown that, owing to latent image fading, the total time for 
which the film is left open to a humid atmosphere is significant. At 35°C 
(95°F) materials, if left completely open to an atmosphere of 90 per cent 
relative humidity, may become unusable in as little as a few days. Condi- 
tions of such severity are relatively frequent during the rainy season in 
various localities. It should, however, be remembered that photographic 
materials are seldom left completely open to the atmosphere, and the 

5 GN-5 



camera, wrapping paper, or even adjacent sheets or convolutions of 
sensitized material may greatly restrict access of the prevailing humidity. 
For these reasons deterioration at the rate mentioned above rarely arises 
in practice. 

Other troubles rising from high humidity are caused by the sensitized 
layers swelling until they become sticky. Adjacent sheets or convolutions 
of film may stick together and film may also fail to pass safely through the 
mechanism of the camera. Mould is also liable to grow on the unpro- 
cessed emulsion surface. Moisture droplets which will aggravate the 
swelling of the sensitive layer may be deposited following the rapid cooling 
of vessels sealed at high humidities. At all times, packages and other 
containers for sensitized materials should be protected from sudden 
temperature changes. 

Handling and storage precautions 

General Precautions : On storage shelves, individual packages of paper 
and sheet film should be placed on edge to avoid pressure marks. Cine 
film cartons should be stored flat so that the weight of the film rests on the 
sides of the spools. 

Photographic materials should be protected from high concentrations 
of such harmful gases as hydrogen sulphide, formaldehyde, ammonia, coal 
gas, mercury vapour, industrial gases, war gases, motor exhausts, and 
vapours of solvents, cleaners, and turpentine. Packages of photographic 
materials should preferably be kept away from these gases, but the 
humidity-proof tropical packing used by manufacturers should give a high 
degree of protection against most of them. 

Where well-equipped storage accommodation can be provided, films and 
plates should be kept below 16°C (60°F), but 10°C (50°F) is preferable; 
paper should be kept below 21°C (70°F). The ideal relative humidity 
is 40 to 60 per cent. Obviously, however, these conditions are unlikely 
to be attainable, but the following precautions may be taken to prevent 
deterioration due to high temperature alone. It should, however, be 
remembered that the shorter the proposed storage time the more can the 
precautions be safely relaxed. The temperature of the sensitized mat- 
erials should at all times be kept as near to the above recommended 
temperature limits as possible. 

During transport, all cases containing photographic materials should be 
kept out of direct sunlight. They should be placed in the shade or under 
other materials, and should not be allowed to remain for long on loading 
platforms or docks. The same precautions should be maintained through- 
out expeditions. It should be remembered that the smaller the unit in 
which the material is contained, the more rapidly will heating by the sun 
affect it. A camera left lying in the sun in still air, as for example in an 
open car, may reach a temperature very considerably higher than the air 
temperature and may set up very dangerous conditions for any film 
contained within. During shipment the baggage or mail rooms of ships, 
which are usually close to the engines, should be avoided, as temperatures 
are often likely to exceed 50°C (122°F) for considerable periods. 

GN-S 6 



In choosing the storage space the following precautions should be taken. 
Unventilated buildings and the top floors of uninsulated buildings should 
be avoided, and materials should be stored well away from outside walls, 
steam pipes or other heat sources. A cold store is very desirable in 
order to attain the above recommended conditions, but if this type of 
storage is used, packages should be brought out into more moderate 
conditions a few hours before use. This is to allow the material to warm 
up gradually, so that condensation of moisture, particularly on the emul- 
sion surface, does not occur when it is exposed to the warm air. Cold 
stores which are not equipped with air drying plant are not necessarily 
best run at the lowest temperature obtainable, in that the lower the tem- 
perature, the higher will be the relative humidity. Except where the 
materials are all enclosed in humidity-proof containers it may, for example, 
be preferable to maintain the cold store at 16°C (60°F) with 40 per cent 
relative humidity rather than 4°C (40°F) with 80 per cent relative 
humidity. 

The preservation of an even temperature may also lengthen the life of 
materials in partially sealed containers, which might otherwise acquire 
moisture through " breathing " due to temperature changes. In perma- 
nent stations, the use of storage pits may help to secure a lower and more 
uniform temperature, and caves should also prove useful for storage 
purposes. Materials in completely humidity-proof containers may be 
kept at a lower average temperature by chilling as much as possible during 
cool nights, and then storing with bedding or other insulating material 
heaped on top during the day. 

Special Precautions for Humid Conditions : The adverse effects of high 
humidity during storage can be largely avoided by keeping the humidity- 
proof packages intact as long as possible. For this reason the packages 
should be examined on receipt to make sure that no damage has occurred 
in transit which will affect their protection against humidity. If the 
packages have to be opened for any reason in humid conditions, the metal 
container should be re-closed either in a dry atmosphere or else enclosed 
with a desiccating agent, such as silica gel (see overleaf) to lower the 
humidity of the enclosed atmosphere. Various types of metal boxes are 
advocated as humidity-proof containers. Flat sensitized materials may 
be stored in zinc-lined boxes which are sealed by soldering. Metal boxes 
sealed with adhesive tape are also advocated, although the tape may 
require to be renewed from time to time. Boxes may alternatively be 
sealed by stout clamps holding down a lid equipped with a rubber gasket. 
Steel "African" uniform boxes the size of a suitcase are also suggested as 
suitable for the transport of a small stock of sensitized material in the 
field; such a box should be painted white to lessen radiant heat absorption. 
The hermetically sealed Garrison type container may also be used for the 
same purpose. 

The following precautions are intended to neutralize the harmful effect 
of high humidities. The stringency with which it is necessary to practise 
them depends on the severity of the conditions likely to be encountered. 

Although it is possible to dry out and re-seal the materials, after a 
humidity-proof package has once been opened to extract part of its 

7 GN-5 



contents, it is more convenient to employ small unit packages and use up 
all the sensitized materials in each, as rapidly as possible after opening. 
No benefit is obtained, however, by exposing all the material as soon as it 
is opened to avoid loss of emulsion speed, if development is delayed for 
such a time that serious latent-image fading occurs, unless suitable care of 
the exposed material is also taken. Under field conditions of use, this 
may in fact prove the greater problem. 

The effects of high humidities after exposure may be largely avoided by 
exposing all the material as soon as possible after opening the original 
package and then either developing, or drying the material out and re- 
packing in humidity-proof containers, as soon as possible after exposure. 

The following considerations will probably influence the choice of 
procedure under any one set of conditions in the field or during an expedi- 
tion. Immediate processing will often entail additional difficulties such 
as shortage of water supply and very high processing temperatures — 
which are not encountered in a studio or any other properly equipped 
darkroom. It also necessitates the carrying of chemicals and other 
additional equipment. It has, however, the advantage of revealing at the 
earliest possible moment whether satisfactory results have been obtained, 
and hence of allowing any necessary re-takes to be made with minimum 
inconvenience. This may be important when the photographer is not 
very certain of the condition of his photographic material or of the exposure 
required by local conditions. On the other hand it has frequently been 
claimed that perfectly satisfactory results are obtainable by processing film 
several months or even a year after exposure in the tropics, so long as the 
material is thoroughly dried out soon after exposure. It may even be 
desirable to delay processing of film until the return to a more temperate 
climate, so that any adverse effect of high-temperature processing on 
graininess may be avoided. It should perhaps also be noted in comparing 
these two procedures that a photographer using film packed in sealed 
metal containers does not have to carry desiccating agents if he intends to 
process shortly after exposure. 

The following methods are recommended for desiccating film after 
exposure. Film which has absorbed only a small amount of moisture can 
be dried satisfactorily by re-packing in dried black photographic paper, 
and re-sealing in a metal can with two turns of pressure-sensitive tape 
around the lid joint. Only black photographic wrapping paper may be 
used in direct contact with the film, since most ordinary papers contain 
chemicals injurious to the emulsion surface. The wrapping paper should 
be dried before use, in an oven or over a fire. As it rapidly absorbs 
moisture from the film it should preferably be re-dried daily for the first 
few days after re-packing. Materials in moisture-permeable photo- 
graphic wrappings may be kept dry by surrounding the package with as 
large a mass of dried-out cellulose material (such as newspaper, or even 
hay or straw) as possible. This acts both as a desiccating agent and as a 
thermal and moisture insulator. 

Silica gel (in 8 to 20 mesh grade) is a far more effective desiccating 
agent. It should be dried before use by heating to 200°C (390°F), or 
more, stirred and cooled in a closed container. One to two pounds are 

GN-5 8 



necessary to dry 1000 feet of 35 mm film completely saturated with 
moisture (an extreme case), proportionately less being required for less- 
saturated film. When silica gel is not available, ordinary rice (dried by 
heating to a faint brown) is also a useful drying agent; ten pounds will 
effect reasonable drying of 1000 feet of 35 mm film. These agents should 
be left with the film for several days, depending on the quantity of moisture 
in the film and the tightness of the roll. They should be separated from 
the film by a suitable membrane in order to prevent its dust from reaching 
the emulsion. Either chamois or some finely woven fabric may be used 
and may be made up into a bag to contain the desiccating agent. These 
agents should not be used to dry film when the atmosphere is obviously 
dry. Chemical drying under these conditions may cause the film to 
become excessively brittle and it may crack or develop static marks during 
later handling. Excessive drying may also have a bad effect on papers. 

Attention is drawn to the danger of enclosing moist sensitized materials 
in completely sealed or even semi-sealed cans. This may cause even 
more damage than enclosing in a moisture-permeable package, while the 
fact that the material is enclosed in a can may give rise to a false sense of 
security. In addition, rapid cooling may be followed by the condensation 
of moisture droplets on the emulsion surface, which will cause a mottle 
to develop. 

In miniature cameras, where the exposed film is usually wound back 
into a closely fitting cassette, subsequent drying out of the film on being 
placed in a desiccating tin may be somewhat hindered and effects of the 
type referred to above may occur if the conditions of use in the camera are 
such as to allow the film to take up an appreciable amount of moisture. 
In such special cases, therefore, it may be safer, if possible, to take the 
spool out of the cassette before packing in a humidity-proof tin. 

Colour Films: Colour films, processed or unprocessed, are affected by 
exposure to the fumes of paraformaldehyde, which is an ingredient in 
many anti-mildew compounds. The fumes work in from the edges of 
the film and have the effect of hardening the emulsion, thereby interfering 
seriously with the processing and causing colour-balance shifts. They 
adversely affect the stability of the dyes — particularly the yellow dye — in 
processed colour films. 

Typical exposure to this chemical occurs when a loaded camera is put 
in a clothes cupboard in which a bag of anti-mildew compound has been 
hung. Even when an empty camera is exposed to this vapour, enough 
of the vapour may remain to affect a film subsequently loaded into the 
camera. Whilst compounds of formaldehyde seem to represent the 
greatest danger, other chemicals, such as paradichlorobenzene (often 
contained in insect and moth repellent), are also harmful. 

Loaded cameras and any opened film should be kept away from these 
vapours, but unopened packages of colour film are sufficiently vapour- 
tight to provide protection in ordinary circumstances. 

Storage of Papers before Exposure : The photographic characteristics of 
sensitized paper are, like those of film, adversely affected by heat and 

9 GN-5 



moisture, although to a lesser extent. Some 'Kodak' papers intended for 
use in tropical countries are specially packed in heat-sealed foil and 
hermetically sealed. This foil wrapping protects the contents from 
moisture but not from heat; therefore, the paper should be kept in as cool a 
place as possible. Once the seal has been broken and the package opened, 
the paper should be used as quickly as possible. 

To prevent heat deterioration, papers should not be stored and prints 
should not be displayed in direct sunlight, or against outside walls on which 
direct sunlight falls. Interior rooms, should be selected as storage areas. 

Adverse storage conditions for only a brief period may have a permanent 
effect on the paper. The ill effects are cumulative, and changes resulting 
from improper storage cannot be corrected. Systematic stock rotation 
is one of the best ways of minimizing the possibility of cumulative 
deterioration. 



EXPOSURE 
Monochrome films 

Guidance as to approximate exposures may be obtained from published 
tables such as those given in the instruction sheets packed with 'Kodak' 
films and those in relevant Kodak Data Sheets. Photo-electric exposure 
meters should also prove useful, but only those makes with particularly 
robust movements (this does not mean that they must necessarily be 
heavily constructed) are likely to stand up well to tropical conditions. 
Many writers have emphasized both the misleading exposure indications 
likely to be obtained with exposure meters in the tropics and the great 
difference produced by local conditions. The advice of photographers 
acquainted with local conditions should, therefore, when possible, 
always be sought. If extensive photographic work in the tropics is 
planned, the development of a few test exposures is good insurance against 
major failures. It is usually sufficient to determine a basic set of exposures 
which can be modified to suit other materials, subjects or conditions. 

Practical experience has shown that in many cases very little increase in 
light value is experienced with sun elevations above 36°. In consequence, 
there is a tendency to under-estimate the exposure necessary, particularly 
in the middle of the day. This assumption does not hold, however, for 
open subjects such as open seascapes, landscapes with light sandy surfaces 
or views of very distant objects. With subjects at a closer range the correct 
exposure is strongly influenced by the illumination of the shadows. The 
moisture and dust content of the atmosphere is therefore important, 
because shadows are illuminated mainly by light reflected from particles 
suspended in the air, except in cases where supplementary reflectors or 
lighting can be used. Thus, in regions where the atmosphere is very dry 
and clear, the shadows tend to be deeper than in temperate countries, 
particularly under foliage. A full exposure should be given to counteract 
this condition if any important areas of the picture are in the shade; 
double the normal or indicated exposure may be given. The film should 
then be developed to a lower contrast than is customary in temperate 
countries, except when the exposed film has been kept for a considerable 

GN-5 10 



time at a high temperature. Consideration should also be given to the 
time of day at which exposures are made. Heat shimmer is likely to be 
pronounced around mid-day and can cause bad definition. In addition, 
the trouble due to heavy shadows is aggravated by high sun altitudes, 
which also give a flat lighting most unfavourable for showing ground 
configuration. Morning or evening exposures will minimize these diffi- 
culties although subject contrast may still tend to be high. 

Regions of extremely high humidity, on the other hand, seem to call for 
a lower general level of exposure, since the moisture particles in the air 
reflect a considerable amount of light into the shadow areas. Under these 
conditions, care must be taken to avoid over-exposure. Particularly large 
variations of exposure may be experienced with a change of altitude in 
mountainous country in tropical regions. 

Atmospheric conditions will also affect the choice of colour filters for 
cutting haze or improving the rendering of clouds. In humid tropical 
climates, penetration of the characteristic drapery of bluish haze will 
require a very deep yellow filter such as the 'Wratten' No. 15 (G) and on 
occasions even the red 'Wratten' No. 25 may be needed. Similarly a filter 
at least as deep as the yellow 'Wratten' No. 8 (K2) is needed to obtain good 
cloud effects. On the other hand, niters may be unnecessary for haze 
cutting in arid or semi-arid regions even for long-distance shots. 



Colour films 

In general, the exposures for colour films should follow the same basic 
recommendations as are given for temperate zones. There are, however, 
some differences in the lighting conditions and scene characteristics, in 
the tropics, which justify special consideration. The more important of 
these considerations are listed below. 

1 During the rainy season, a light haze is generally present in the 
atmosphere. When this haze is present, the disk of the sun is clearly 
discernible and fairly distinct shadows are cast. Under these conditions 
the exposure should be increased to about half a stop more than the 
normal recommendation. 

2 Frequently the brightness of beach and marine scenes is appreciably 
greater than that encountered in temperate zones. With such scenes 
the exposure should be decreased to one stop less than the normal recom- 
mendation for an average subject. 

It should be remembered that the term "average subject" refers to a 
subject or scene in which light, medium, and dark areas are roughly equal 
in proportion; it should not be interpreted as "usual" for a particular 
location or area. For example, a usual desert scene is a light subject 
rather than average, and should be exposed as such. 

3 When the sun is high overhead, heavy shadows are cast across vertical 
surfaces, very much like those occurring in side-lit scenes. Therefore, 
the exposure should be increased to half a stop more than the normal 
exposure, just as is recommended for side-lit scenes. With close-up 
subjects containing important shadow detail, the exposure increase may 

II GN-5 



amount to a whole stop, depending on the effect desired. A better 
procedure involves the use of supplementary flash as a "fill-in" to lighten 
deep shadows. 

4 Many objects in the tropics, not only painted buildings and light- 
coloured fabrics, but even the leaves of many plants and trees, have a 
high reflectance. Consequently, with front lighting they should be 
treated as light subjects, whilst with side, top, or back lighting they should 
be considered average subjects. 

5 Very often, the colours of objects will be affected by the green light 
reflected from nearby bright green foliage. Similarly, in courtyards or 
narrow streets, the side that is in shadow gets much of its illumination 
from the opposite, sunlit wall, which may be strongly coloured. There 
is little that can be done to correct for this situation, but it should be 
recognized as a possible cause of poor results in colour photography. 
Pictures of nearby people can be improved, in these situations, by the 
use of fill-in supplementary flash. 

PROCESSING 
General aspects 

When processing in the tropics, the temperature of the solutions will 
often be relatively high, and this is liable to cause excessive swelling or even 
melting of the emulsion. Excessive swelling may cause the emulsion 
to strip or frill. If a developer containing carbonate is used for films, 
blistering may be caused by the evolution of carbon dioxide on transferring 
the greatly swollen layer to an acid fixing bath; this difficulty, however, 
may be avoided by the use of 'Kodalk' Balanced Alkali as the alkali in the 
developer. Excessive swelling can also produce the crinkled configuration 
of the layer known as reticulation, which may be coarse enough to be seen 
with the naked eye, or may be so fine that it is often mistaken for increased 
graininess. 

Greatly swollen layers also take much longer to dry, particularly in 
humid conditions, and contamination of the emulsion by dust or even 
growth of moulds is thereby encouraged. The risk of accidental damage 
is increased by the low mechanical strength of a heavily swollen emulsion 
layer, but may be lessened by the use of film hangers or other apparatus 
into which the exposed material is loaded while dry and thus receives no 
fingering until processing is completed. Difficulties due to excessive 
swelling occur mainly with films, the emulsions of which are generally 
thicker and less hard than those of papers. Papers can safely be processed 
in developers made up with carbonate. 

Humid tropical atmospheres affect not only the keeping properties of 
sensitized materials but also the permanence of the processed images, 
particularly on paper prints. Thus, if photographic records are required 
for more than a few months' storage under tropical conditions, special 
precautions are needed either to achieve as complete hypo elimination 
from the layer as possible, or else to protect the image from the combined 
action of hypo residues and tropical storage conditions. Detailed proces- 
sing instructions for obtaining a reasonable degree of permanence are 

GN-s 12 



given in the Appendix. It is easier to produce permanent records on 
films than on papers. 

Another factor which may lessen permanence is the tendency of moulds 
to grow on all moist gelatin surfaces. This is lessened if the gelatin is 
thoroughly hardened, but is almost completely avoided by the use of 
a zinc fluosilicate solution immediately prior to drying. 

Processing at high temperatures also introduces some modification of 
the photographic characteristics of the material employed. Increased fog 
is obtained, together with a decrease in gamma. The fog can be lessened 
in some cases by adding 'Kodak' Anti-Fog Powder according to the 
instructions or as indicated by tests in each individual case. Loss of 
contrast may be particularly undesirable in the case of "process" materials 
normally used with special caustic developers, which are too alkaline for 
use at temperatures above 24°C (75°F). Fast negative materials often 
show an increase in graininess (quite apart from any reticulation effect) 
and reduced resolving power when processed at high temperatures. 
The coarser the intrinsic grain of the original material the more serious 
is this likely to be, but fine-grain, medium-speed materials, such as 'Pana- 
tomic-X' Film, show a change which should only be significant in ex- 
ceptionally great enlargements. 

The practical difficulty in the handling of dry photographic material, for 
instance, when making prints, is the rapidity with which the hands become 
wet with perspiration. It may be necessary to wash and dry the hands 
every few minutes to prevent results being disfigured by fingerprints. 

Colour-film processing in the tropics 

Colour-film processing should not be attempted unless the solutions 
can be used at the recommended temperatures. 

A block of ice, or a day's production of ice-cubes from a large modern 
refrigerator, can be used to bring the processing solutions and washing 
water to the desired temperature. The solutions, in bottles, should be 
placed on the ice until they approach the proper temperature, then 
immersed in water at a degree or two below the processing temperature. 
For processing, tanks may be placed in a bath of water which has been 
brought to the correct temperature, but on no account should ice be put 
directly into processing solutions. 

Darkrooms in the tropics 

Darkrooms for tropical photography may be identical in arrangement 
to those for photography in temperate zones, except in the matter of 
ventilation. 

Because of the higher air temperature in the tropics, it is essential to 
provide ample ventilation for the darkroom; three or four times more 
air-flow is desirable in tropical zones as compared with a well-ventilated 
darkroom in a temperate zone. Darkroom ventilating fans are desirable 
to ensure this ventilation. If such fans are not available, however, 
ventilators should be installed, and it is sometimes possible to locate the 
darkroom so that draughts set up by the prevailing winds will flow 

13 GN-5 



through the ventilators. Alternatively, if it is not possible to change the 
location, then it is recommended that the positions of the ventilators be 
arranged so that the maximum possible flow of air is obtained. Work 
can also be done at night, when temperatures are generally lower. 

Tropical temperatures can have a damaging effect on sensitized 
materials, and on equipment. Consequently, darkrooms in the tropics 
should be larger in volume than those in temperate zones, unless the 
darkroom is air-conditioned. Further recommendations for darkroom 
design and layout may be found in Data Sheet PR-7. 

Insects and reptiles also introduce certain hazards, and ordinary precau- 
tions must be taken against their entry into darkrooms. Insects such as 
mosquitoes are liable to setde on emulsion surfaces during drying and 
larger gelatin-eating insects such as cockroaches may damage considerable 
areas of negatives. 

Developing and fixing 

Vigorous agitation during development is advisable since this speeds up 
development, allowing a shorter time to be used with consequent lessening 
of swelling. Excessive swelling of the emulsion of films may, within 
certain temperature limits, be prevented satisfactorily by loading the 
developer with a neutral salt such as sodium sulphate and by using 
potassium alum in the fixing bath. In this connection it should be noted 
that hardening of the emulsion by the fixing bath is just as important as 
the clearing and fixing-out of the silver salts. The full recommended 
fixing times should therefore always be used even if the emulsion clears 
in much less than half this time. Formaldehyde should not be used in 
the developer as it causes fog. A hardening-fixing bath must always be 
used in the tropics. 

The whole processing procedure must therefore be designed to prevent 
excessive swelling occurring at any stage prior to permanent hardening 
of the emulsion. These methods are beneficial if applied before excessive 
swelling has occurred but are relatively useless if applied after excessive 
swelling has taken place ; in this case they may actually promote reticulation. 
For similar reasons, uncontrolled changes of temperature from one 
solution to the next may result in more damage than if all the solutions 
were used at the same high temperature. 

Photographic papers in general do not need special precautions to avoid 
swelling but care should be taken to avoid development fog (see Appendix). 

During the development of films, they should, as far as possible, 
be kept under the surface of the developer. This is advisable since 
processing at high temperatures is likely to favour the formation of aerial 
fog. 

Finally, it should be noted that development in the tropics is likely to 
show considerable variations, particularly if the materials are not quite 
fresh. When a number of films is to be processed, therefore, the first 
one developed should be examined before starting on the others, and if the 
contrast obtained is found to be either too low or too high, the time should 
be increased or decreased accordingly. 

GN-5 14 



Washing and drying 

The washing of films at tropical temperatures causes further swelling, 
but if the precautions suggested are complied with, the recommended 
washing time may be given safely. If records of the highest possible 
archival permanence are required, the dried materials may be re-washed 
later (as described in the Appendix) when conditions are more favourable. 
In this connection it should be mentioned that when a hardened emulsion 
layer is dried down for any appreciable time an irreversible hardening 
occurs which renders it much more resistant to excessive swelling during 
any subsequent treatment. Some workers take advantage of this effect by 
giving the material only a very brief rinse after fixing and before drying. 
The rinse need only be sufficient to prevent hypo crystallizing out when the 
emulsion dries down. This method is quite safe if the material can be 
re-washed (preferably also re-fixed) within a few days, and has certain 
practical advantages. If, in spite of all precautions during the early stages 
of processing, a film appears to be swollen to a dangerous extent while still 
in the fixing bath, this may be the only convenient method of preventing 
reticulation. Failure to re-wash the negatives within a few days may, 
however, allow serious fading of the developed image to occur. 

Either the use of Kodak 'Photo-Flo' Solution as a final rinse, or wiping 
down with a viscose sponge or chamois leather will help remove the surface 
film of water from the emulsion, thus speeding up drying and preventing 
the formation of water spots. Wiping down of the emulsion before drying 
also removes surface dirt but must be done gently and requires some 
judgement and practice. The following points should be considered. If 
the emulsion is very soft or if appreciable frilling or stripping is apparent, 
any wiping should be avoided, but in this case the wetting agent will help 
the negatives to drain rapidly. More robust layers may be given gentle 
swabbing or wiping under water, with a viscose sponge, chamois leather, 
or cotton-wool swab. This helps to detach most of the dirt from the 
emulsion surface. When hung up to dry, both sides of films may be 
wiped down with a leather to remove the film of liquid from the surface. 
The necessity of removing surface dirt by swabbing is particularly great in 
the case of miniature negatives. 

The drying of processed materials is often rendered difficult by the high 
humidity of the surrounding air. Under extreme conditions it may be 
found impracticable to raise the temperature of the air during the initial 
stage of drying because of the risk of melting the gelatin. In these cases, 
drying can be accelerated either by keeping the air moving rapidly or by 
using alcohol. The material may be bathed for up to 5 minutes in a 
mixture of water and industrial (or surgical) spirit just before drying. 
With most films, a mixture of 7 parts of spirit with 3 parts of water can be 
used safely. Films with thin base or with no non-curl layer (usually cine, 
aero, and miniature film) should be treated carefully to avoid damage to the 
base, and in these cases it is safer to use a spirit bath not stronger than equal 
parts by volume of spirit and water. In the final stages of drying, the air 
temperature may be raised considerably since gelatin in the nearly dry 
condition is not likely to melt. The dried films should be transferred 
immediately to storage envelopes or cans so as to hinder re-absorption of 

15 GN-S 



moisture as the material cools. Prints on single or light-weight paper base 
may, if necessary, be dried very rapidly by soaking in undiluted spirit and 
hanging in a current of air. 

Although the use of alcohol will usually halve the drying time required, 
it precipitates zinc fluosilicate, and these treatments cannot be given at the 
same time. Thus, if negatives or prints which have been dried with the 
aid of alcohol are to be stored under humid conditions, they should, when 
conditions are more suitable for drying, be soaked in zinc fluosilicate 
solution and dried without the aid of alcohol. This treatment may be 
combined with any re-fixing, hypo elimination, or toning treatment it is 
decided to employ, to ensure results of maximum (archival) permanence 
(see Appendix). 

During drying, negatives should be protected from insects or coarse dirt 
by the use of gauze or mosquito netting. Protection from cockroaches 
may be eifected by hanging films from a wire. 



Choice and storage of photographic chemicals 

All processing chemicals carried in the solid state should be kept as dry 
as possible and well away from sensitized materials, but certain chemicals 
need particular care. Some chemicals, such as ammonium thiocyanate, 
potassium carbonate, sodium hydroxide (caustic soda), potassium 
hydroxide (caustic potash), and sodium sulphide, take up water from the 
air, first becoming moist and then dissolving into a liquid. These should 
be kept in corked bottles with the neck dipped in melted paraffin wax. 
On the other hand, some chemicals such as the crystalline forms of sodium 
carbonate (10 H 2 0) and sodium sulphate (10 H 2 0) tend to lose water of 
crystallization and become powdery. Alkalis such as sodium hydroxide, 
potassium hydroxide and, in moist atmospheres, 'Kodalk' Balanced 
Alkali will, however, keep sufficiently well in the original covered container. 

All these changes complicate the use of the chemicals, which should 
therefore be protected from free access of air as much as possible. 

For processing under difficult " field " conditions, the anhydrous forms 
of chemicals are generally preferable to crystalline. Usually only half the 
weight and a considerably smaller bulk need be carried. Monohydrated 
sodium carbonate is less affected by the atmosphere and it is stated to have 
less tendency than the anhydrous to cake on mixing with water. Experi- 
ments have shown, however, that with only moderate care in storage the 
anhydrous salt is in no way inferior to the monohydrate, whilst 17 per cent 
more of the latter salt has to be used. Anhydrous sodium sulphite is much 
less prone to oxidation than the crystalline form. 

Compounded packed processing chemicals are prepared by photo- 
graphic manufacturers in special containers for tropical use. When 
ordering such chemicals in temperate countries the user should, therefore, 
always emphasize that they are required for use in tropical regions. 

GN-5 16 



Preparation of solutions under field conditions 

Some of the recommendations given in this section apply in particular 
where operations are being carried out under crude field conditions but 
are worth keeping in mind even when reasonably good storage and dark- 
room facilities are available. 

Measurement of Chemicals : For best quality and reproducibility, it is 
desirable to weigh out and measure the constituents of solutions to within 
1 per cent. Where facilities for weighing are crude or chemicals are of 
doubtful purity, tolerable results are given by most solutions with variations 
of 10 to 20 per cent in the quantities, and even much larger variations may 
give acceptable results, though a preliminary practical test of the perform- 
ance should be made. The problem of accuracy is obviated if prepared 
developer and other packages are available. 

The following methods may be used for estimating weights and measures 
roughly in the field. 

Containers such as developing tanks, bottles, cans, and watertight 
boxes, and mess kit such as spoons and cups may have their volume 
measured, and then be marked indelibly. Small volumes of liquids may 
be measured by drops, and a general average of 20 drops per ml may be 
assumed. This is only a very rough measure, however, as the size of 
the drop depends on many uncontrolled factors. The weight of solid 
chemicals may be roughly estimated from the volume they occupy when 
poured into a measuring cylinder and packed by tapping. 

The table below gives some approximate figures for the volume of 
some solid chemicals. It is important to note, however, that the volume 
per unit weight of any chemical varies according to the shape and size of 
the particles, and the operator should preferably determine the appropriate 
figure for himself for each consignment or sample he has to use. 

Chemicals used in only very small amounts should be made up to give 
stock solutions of suitable strength, such as 10, 1, 0.1 or 0.01 per cent. 

APPROXIMATE VOLUME OF SOLID CHEMICALS 



Chemical 


State 


Volume of 100 grammes 
(in millilitres) 




Crystals 

Crystals 

Fine crystals 

Fine crystals 

Pea crystals 

Fine crystals 

Fine crystals 

Crystals 

Crystals 

Powder 

Powder 

Powder 


115 


Metol ('Elon' Developing Agent). 

Hypo 

Potassium chrome alum . . . 

Sodium metabisulphite . . . 
Sodium carbonate (anhyd.) . . 
Sodium sulphate (anhyd.) . . . 
Sodium sulphite (anhyd.) . . . 


110 
150 
160 
95 
100 
105 
70 
85 
140 
75 
65 



17 



GN-5 



Dissolving the Chemicals : When the solutions are required immediately, 
two procedures are possible: (1) dissolve the chemicals in the smallest 
possible volume of hot water 50°C (122°F) and then dilute with cold 
water, or (2) dissolve the chemicals in almost the complete volume of 
water at the working temperature, finally making up with extra water to 
give the correct volume. Procedure (1) is rapid but should only be used 
when it is possible to add water cool enough to bring the solution to the 
working temperature. 

When hypo crystals are dissolved in water, the temperature of the solu- 
tion drops considerably and care should be taken, if it is used immediately 
after mixing, to note that there is no great divergence of temperature 
between it and other processing solutions. This may be avoided by 
dissolving the hypo in hot water. 

Water Supply : Although distilled water is ideal for the preparation of 
solutions it is neither readily obtainable nor essential. Natural water may 
contain as impurities (1) soluble salts, (2) suspended matter and (3) dis- 
solved gases. Calcium and magnesium salts are the most important and 
are found in almost all water except rain water. They cause cloudiness of 
freshly prepared developer, sometimes resulting in the formation of a 
white irregular scum on the surface of the film which, however, is removed 
in fresh acid fixing baths, but it is better to lessen the risk of occurrence 
by allowing the sludge to settle, decanting, and then using the clear liquid. 
The addition of 35 to 175 grains of sodium hexametaphosphate per 80 
fluid ounces (1 to 5 grammes per litre) to the water to be used for making 
up the developer, will largely prevent the cloudiness and scum, but may 
itself cause scum if the developer is kept for long periods. It is important 
that the sodium hexametaphosphate be dissolved before the developer 
chemicals. It may be necessary to rinse thoroughly between developing 
and fixing to avoid precipitation of aluminium phosphate by sodium 
hexametaphosphate carried over into the fixing bath. Soluble sulphides 
and copper and zinc salts are rarely found in natural waters, but when 
present will cause severe fogging. Water contaminated by mining or 
industrial wastes is to be avoided. Suspended mineral and vegetable 
matter is found in many sources and may cause spots on the film. Fil- 
tration will remove coarse particles but not the suspended matter. Boiling 
the water will coagulate this, or if the developer is prepared hot and 
allowed to cool overnight the suspended matter will settle out and the clear 
decanted liquid may be used. Any coagulated matter which rises to the 
surface should be skimmed off with blotting paper or absorbent cloth. 

The chlorine content of drinking water which has been treated with 
chloride of lime is so low that it may safely be used for photographic 
purposes. There is, however, no need to sterilize water used for processing. 

Sea water or brackish waters may be employed for preparing developers 
but may produce a heavy sludge after a few minutes' standing. This 
should preferably be allowed to settle. A speed loss of 50 per cent may 
be experienced if fast films are being developed in low-energy developers, 
such as D-76, made up with sea water, but other more energetic developers 
are not likely to show appreciable loss. Salt water is entirely satisfactory 
for making up an acid hardening-fixing bath. Films and prints can be 

GN-5 18 



safely washed in sea water, since hypo is actually removed from photo- 
graphic materials more rapidly by sea water than by fresh water. Washing 
in sea water should, however, be followed by a rinse in each of two or even 
three changes of fresh water to remove the residual salts which would 
otherwise accelerate the fading of the image. Alternatively, the material 
might in an emergency be dried without the fresh water rinses and re- 
washed in fresh water within a few weeks. 

Potassium alum efficiently coagulates suspended matter in muddy 
water. About 9 grains are added per 80 fluid ounces (0.25 gramme per 
litre) and, after settling, the clear water is drained off. This amount 
of alum is insufficient to interfere with developers and other photographic 
solutions made up with such water. Fixing baths can be made up with 
muddy water if alum is added; they should clear on standing. Hydrogen 
sulphide is the only troublesome dissolved gas which is likely to be 
encountered, and it may cause severe fog if present in the water used for 
making up developers. Sulphurous water used for developers should, 
therefore, always be boiled, to drive off gases and to coagulate suspended 
sulphur. 

PROTECTION AND STORAGE OF NEGATIVES AND PRINTS 

In general, negatives and prints are not so susceptible to their conditions 
of storage as are the sensitized materials. In all cases, the humidity should 
be neither excessively high nor excessively low. For greater permanence, 
high temperatures should be avoided, but in some cases, where the imme- 
diate physical condition of the material is more important than its perma- 
nence, it may be advantageous deliberately to raise the air temperature 
over a limited period as a means of reducing the relative humidity and 
thereby the moisture content of the material. High temperature and 
humidity accelerate the deterioration of images which have not been 
specially stabilized in processing, and encourage the growth of moulds. 
Data Sheet RF-9 gives details of the prevention and removal of mould 
growth on photographic materials. Excessive heat and dryness, on the 
other hand, may render paper prints brittle by degradation of the paper 
base. Thus, in general, negatives and prints should be stored in 
moderately cool and fairly dry conditions, and in addition good ventilation 
is desirable. In the case of old records made on nitrate film base, good 
ventilation is essential; these films should be inspected periodically so 
that corrective treatment can be applied, or reproductions made, before 
deterioration has gone too far. 

The permanence of negatives and prints, even of those not processed 
ideally, may be increased by the use of a suitable varnish. The permanence 
of prints is greatly improved by the gold protective treatment or by the 
hypo-alum treatment given in the Appendix, and may be further improved 
by varnishing on both sides. Most paste adhesives are hygroscopic, and 
should not, therefore, be used for mounting prints to be kept in the 
tropics; dry-mounting tissue should be used for permanence. 

Reels of processed cine film, and particularly release prints which may 
be projected several times daily, introduce a special problem. If the 

19 GN-S 



loosely coiled turns of film are exposed to a high humidity, the consequent 
swelling of the gelatin layer may cause the turns of the film to distort into 
kinks or even to take up a polygonal form on the reel; the swelling may be 
so great as to cause the film to become tacky on sudden heating-up in the 
projector gate. Both these effects lessen the ease of projection and can 
lead to severe damage of the film. The use of desiccators in the film cans 
will reduce the trouble, but may be inconvenient under these conditions 
of use. The difficulty may be largely avoided by sealing the film up in a 
can while still warm from the projector; the can should be sealed with 
two turns of pressure-sensitive tape. Alternatively, if it is unavoidable 
that the film takes up moisture and if its immediate physical condition is 
more important than its permanence, the reel may be stored in a large box 
with ample air space, the temperature of which is maintained at about 
6°C (10°F) above atmospheric conditions by electrical heaters; this (pro- 
vided the box is large) reduces the relative humidity of the air in contact 
with the reel and will greatly lessen the risk of deterioration for projection 
purposes, even though such storage conditions would not be suitable for 
use over very long periods. 



GN-5 20 



APPENDIX 

PROCESSING PROCEDURES FOR 'KODAK* MONOCHROME FILMS 

The outlines of recommended practices are here given for solution 
temperatures of 24-35°C (75-95°F). 

In high-temperature work, it is very important that the temperatures 
of all the processing solutions be equal and fairly constant, otherwise 
reticulation may be produced. Developer, hardening stop bath, fixer, 
and washing water must be held at the same temperature to within 
approximately 3°C (5°F). 

(a) Development : The addition of sodium sulphate, as shown in the 
table below, will give approximately the same developing times at the 
higher temperatures as are required for the plain developing solutions at 
normal temperatures. The developer solution should be stirred con- 
tinuously while the sodium sulphate is being added and until it is com- 
pletely dissolved. If crystalline sodium sulphate is used, multiply the 
quantities recommended by 2\ times. 



KODAK 
DEVELOPERS 



D-ll 
D-19 



D-23 
D-76 



DK-50 
'Dektol' 



(1+1) 



i 



RANGE OF 
TEMPERATURES 



24-27X (75-80°F) 
27-29°C (80-85°F) 
29-32X (8S-90°F)* 



24-27°C (75-80°F) 
27-29°C (80-85°F) 
29-32°C (85-90° F)* 



QUANTITY OF SODIUM SULPHATE 
(anhydrous) 



Per 80 fluid ounces 



A ounces 
6 ounces 
8 ounces 



8 ounces 
10 ounces 
12 ounces 



Per litre 



50 grammes 
75 grammes 
100 grammes 



100 grammes 
125 grammes 
150 grammes 



* If necessary to develop at 32-35°C (90-95°F), use these quantities of sodium sulphate and decrease 
the developing time by about one-third. 

(b) Hardening : After developing, the film should be immersed in the 
Hardening Stop Bath, Kodak formula SB-4, for at least 3 minutes. If 
the temperature is below 29°C (85°F), rinse for 1 to 2 seconds in water 
before immersing in the hardening bath. Agitate the negatives for 30 to 
45 seconds when they are first immersed or streakiness will result. 

This bath is a violet blue colour by tungsten light when freshly mixed, 
but it ultimately turns a yellow-green with use; it then ceases to harden 
and should be replaced with a fresh bath. The hardening bath should 
never be overworked. An unused bath will keep indefinitely, but the 
hardening power of a partially used bath decreases rapidly on standing for 
a few days. 

(c) Fixing: The negatives should then be immersed for at least 10 
minutes, but not more than 20 minutes, in a good acid hardening-fixing 
bath. Kodak 'Unifix' Powder or Kodak formula F-5 (or F-6) should 
be used. 



21 



GN-5 



(d) Washing : The negatives should be washed for 10-15 minutes in 
running water or in several changes of water. Longer washing times 
may cause reticulation if the water temperature is above 32°C (90°F). 
Insufficient washing will cause a rapid staining of film stored in tropical 
areas owing to the decomposition of residual silver salts. If there is any 
doubt on the efficiency of the washing, and to ensure permanence, the 
negatives should subsequently be re-washed when an adequate supply of 
cooler water is available. The treatment of negatives in 'Kodak' Hypo- 
Clearing Agent will reduce considerably the amount of washing necessary 
to ensure permanent images. 

Any scum should be removed by carefully wiping the film under water 
with cotton-wool. 

(e) Drying : To minimize drying marks, the film should be immersed in 
Kodak 'Photo-Flo' solution at the dilution recommended, or the surfaces 
wiped very gently with thoroughly moistened cotton-wool or chamois 
leather. The drying of film which has been allowed to swell excessively 
may be slow, even at fairly high temperatures. The usual precautions 
against mechanical damage should be taken; in the field, it may be necessary 
to protect film with a cage of mosquito netting to keep insects off. * '- 
circulation is essential, especially when the relative humidity is high. 



Air 



When it has been found impossible adequately to fix or wash the film, 
it should be given, within two or three days, the Re-fixing Treatment 
outlined opposite, if it is intended that the film shall be retained. 

PROCESSING PROCEDURE FOR 'KODAK' MONOCHROME PAPERS 

(a) Development : For temperatures of 24-32°C (75-90°F), use D-163 
developer, diluted 1+3, for the times given below. If longer times must 
be used, if the paper storage conditions have not been ideal, or if the 
paper develops a high fog level, modify the developer, as follows. Take 
one part of the D-163 stock solution, add a solution made up from 'Kodak' 
Anti-Fog Powder in the proportion of 2 fluid ounces to every 80 fluid 
ounces (25 ml to every litre), and dilute with 3 parts of water. This 
addition, however, will reduce the image warmth yielded by 'Royal 
Bromesko' Papers. 



TEMPERATURE 


BROMIDE, 'BROMESKO' 
AND 'ROYAL BROMESKO' 


'VELOX' 


24°-32°C (75°-90°F) 


60 seconds 


40 seconds 



(b) Rinse : Rinse in 'Kodak' Indicator Stop Bath, or in a stop bath made 
up according to Kodak formula SB-1, for 5-10 seconds. 

(c) Fixing : Fix for 5-10 minutes in each of two successive baths of acid 
hardening-fixing bath, 'Unifix' Powder or Kodak formula F-5 (or F-6). 
The prints should be kept well separated in these baths and the fixing 
time should never exceed 15 minutes in each bath. The first bath should 
not be used for more than the equivalent of thirty 10 X 12 inch sheets per 
gallon (eleven 18x24 cm per litre), at which stage, or before, the second 
bath should replace the first and a fresh second bath brought into use. 



GN-5 



22 



(d) Washing : Wash single-weight or light-weight prints for 30 minutes, 
and double-weight prints for 45 minutes. The water flow should be 
rapid and care should be taken that the prints are kept well separated. 

When no running water is available, immerse the fixed prints for 5 
minutes in each of 6-12 changes of still water, allowing 15 fluid ounces 
per square foot (0.5 ml per square centimetre) of the material for each 
change. 

(e) Drying : The usual drying technique, with drum or flat-bed glazers, 
will be found to be quite satisfactory, but scrupulous maintenance of the 
drum and cloth is essential; ample water should be used when the prints 
are laid down. Otherwise, prints should be dried in a dry, dust-free 
atmosphere. 

TREATMENTS FOR IMPROVING THE PERMANENCE 
OF NEGATIVES AND PRINTS 
Re-fixing treatment for films 

If it is desired to obtain records of maximum (archival) permanence, the film 
should be given the treatment outlined below within 21 days of processing. This 
treatment, which is best undertaken at about 24°C (75°F), considerably improves the 
permanence of the image. 

(a) Initial Soak : Immerse in water or preferably in 'Photo-Flo' Solution, at the 
recommended dilution, for 5 minutes. 

(b) Fixing : Use freshly prepared acid hardening-fixing bath, 'Unifix' Powder or 
Kodak formula F-5 (or F-6) for 10 minutes. 

(c) Washing : Wash for 30 minutes in running water. 

(d) Hypo Elimination : Soak in 0.03 per cent (by volume) solution of 0.880 am- 
monia for 5 minutes. 

(e) Washing : Wash for 5 minutes. 

(f) Fungicide Treatment : Immerse in a 1 per cent solution of zinc fluosilicate* 
for 2 minutes before drying. 

Treatments for improving permanence of prints 

Because, by straight fixing and washing, it is impossible to eliminate the thio- 
sulphate complexes adsorbed to the paper fibres of prints, images formed of 
developed silver may fade under extreme tropical conditions. Where prints are 
required for archival records, two alternative methods are available for improving 
their permanence. The first is to eliminate the hypo by chemical treatment and 
then to gold coat the image, which renders it far less susceptible to attack by 
external agents. The second is to convert the silver image to a more stable 
compound. The former method retains the original silver image without sig- 
nificantly modifying its colour, whereas the latter will generally modify the image 
colour but is rather simpler to apply. Both methods may be used either immediate- 
ly after washing or after the print has been dried. 

Treatment for obtaining permanent black-and-white prints 

To eliminate hypo from paper fibres it is necessary to use the hypo eliminator 
(Kodak formula HE-1), which, however, is not very stable at temperatures above 
27°C (80°F). The treatment described below, therefore, should only be given at 
temperatures not above 24°C (75°F). If this temperature cannot be attained when 
the prints are first processed, the recommended treatment, including fixing, should 
be applied in full as a re-treatment as soon as more favourable conditions prevail. 
Since the success of the treatment depends upon the complete removal of adsorbed 
thiosulphate complexes, extreme care must be taken to ensure that prints which 
have been given the hypo-elimination treatment do not subsequently come into 

* Zinc fluosilicate and its solution are toxic and should be used with great care. 

23 GN-5 



contact with hypo-contaminated fingers or surfaces such as bench tops, drying 
racks, blankets of drying drums, etc. When prints in a large quantity are to be 
treated, special equipment should be reserved for washing and drying. 

(a) Fixing : Follow the treatments in the two fixing baths as outlined on page 22, 
either with or without subsequent drying, by immersing the material for 5-10 
minutes in the following fixing bath : 

Metric Avoirdupois 

100 grammes Sodium thiosulphate (hypo cryst.) 8 ounces 

1 litre Water to make 80 fluid ounces 

The prints should be kept well separated in all three fixing baths, and the fixing 
time should never exceed 15 minutes in each bath. 

(b) Hypo Clearing : Treat prints in 'Kodak' Hypo Clearing Agent and wash them, 
according to the instructions provided with the Agent, or wash single-weight or 
lightweight prints for 40 and double-weight prints for 60 minutes; the rate of 
change of the water in the tank should be at least 12 times per hour, and take care 
to keep the prints well separated during washing. 

(c) Hypo Elimination : Immerse the prints in the hypo eliminator HE-1 for 5-10 
minutes. The hypo eliminator should not be used for more than thirty 10 x 12 
inch sheets per gallon (eleven 18 x 24 cm per litre), nor stored longer than 24 hours 
in the mixed condition. 

(d) Washing : Wash single- weight or light-weight prints for 10 minutes and double- 
weight prints for 15 minutes. 

(e) Gold Coating : Immerse the prints in Gold Protective Solution, Kodak formula 
GP-1, for 10 minutes at 20°C (68°F) or until a just-perceptible change in image 
tone (very slightly blue-black) takes place. This solution should not be used for 
more than twenty four 10 x 12 inch sheets per gallon (ten 18 x 24 cm per litre). 

(f) Washing : Wash prints for 10 minutes in running water, and dry them in the 
usual manner. 

Treatment for obtaining permanent sepia-toned prints 

By converting the silver image to a stable silver salt, such as silver sulphide, 
permanent sepia-toned prints may be produced. This treatment is simple to apply 
and has the advantage that washing need not be very thorough, as hypo is a con- 
stituent of the toning bath. If, however, prints have already been dried, soak 
them thoroughly in water and then proceed with item (c) below. 

(a) Fixing : Fix normally, using two baths in succession. 

(b) Washing : Wash in running water for a few minutes. 

(c) Toning : Tone prints in Hypo Alum Sepia Toner, Kodak formula T-la, for 12 
to 15 minutes at 49°C (120°F). Toning should not be continued for more than 
20 minutes at this temperature, and blisters and stains may result if a higher 
temperature is used. To ensure even toning, prints should be immersed com- 
pletely and separated occasionally, especially during the first few minutes. In order 
to produce good sepia tones, expose prints so that, with normal development, 
prints are slightly darker than normal. 

(d) Sponging : Wipe prints with a soft sponge and warm water, to remove any 
sediment. 

(e) Washing : Wash prints for 1 hour in running water, and dry them in the usual 
manner. 



GN-S 24 



FORMULAE 

Unless specific instructions are given, dissolve or mix all chemicals, in sufficient water, 
in the order given in each formula. 

D- 1 1 High-Contrast Negative Developer 

Metric 



I gramme 
75 grammes 

9 grammes 
25.5 grammes 

5 grammes 

I litre 



'Elon' Developing Agent 

Sodium sulphite (anhyd.) 

Hydroquinone 

Sodium carbonate (anhyd.) 

Potassium bromide 

Water to make 



Available as a 'Kodak' Packed Developer Powder. 



D-19 High-Contrast Negative Developer 



Avoirdupois 
35 grains 
6 ounces 

315 grains 
2 ounces 25 grains 
175 grains 
80 fluid ounces 



Metric 




Avoirdupois 


2 grammes 


'Elon' Developing Agent 


70 grains 


90 grammes 


Sodium sulphite (anhyd.) 


7 ounces 90 grains 


8 grammes 


Hydroquinone 


280 grains 


45 grammes 


Sodium carbonate (anhyd.) 


3 ounces 265 grains 


5 grammes 


Potassium bromide 


175 grains 


1 litre 


Water to make 


80 fluid ounces 



Available as a 'Kodak' Packed Developer Powder. 



D-23 Fine-Grain Developer 

Metric 

7.5 grammes 'Elon' Developing Agent 

100 grammes Sodium sulphite (anhyd.) 

I litre Water to make 



Avoirdupois 

265 grains 
8 ounces 
80 fluid ounces 



DK-50 Elon'-Hydroquinone-'Kodalk' Developer 

Metric 

2.5 grammes 'Elon' Developing Agent 

30 grammes Sodium sulphite (anhyd.) 

2.5 grammes Hydroquinone 

10 grammes 'Kodalk' Balanced Alkali 

0.5 gramme Potassium bromide 

I litre Water to make 
Available as a 'Kodak' Packed Developer Powder. 



Avoirdupois 

88 grains 

2 ounces 175 grains 

88 grains 

350 grains 

18 grains 

80 fluid ounces 



D-76 Fine-Grain D 


eveloper 




Metric 




Avoirdupois 


2 grammes 


'Elon' Developing Agent 


70 grains 


100 grammes 


Sodium sulphite (anhyd.) 


8 ounces 


5 grammes 


Hydroquinone 


175 grains 


2 grammes 


Borax 


70 grains 


1 litre 


Water to make 


80 fluid ounces 



Available as a 'Kodak' Packed Developer Powder. 



25 



GN-5 



D-163 'Elon'-Hydroquinone Developer 

Metric 

2.2 grammes 'Elon' Developing Agent 

75 grammes Sodium sulphite (anhyd.) 

17 grammes Hydroquinone 

65 grammes Sodium carbonate (anhyd.) 

2.8 grammes Potassium bromide 

I litre Water to make 

Available as a 'Kodak' Packed Developer — powder or liquid. 



Av 


oirdu 


10IS 




80 


grains 


6 ounces 






1 ounce 


160 


grains 


5 ounces 


80 


grains 




100 


grains 


80 fluid ounces 





SB- 1 Stop Bath 

Metric 

I litre 
17 ml 



Water 

Acetic acid (80% solution) 



Avoirdupois 

80 fluid ounces 
I fl oz 170 minims 



SB-4 Tropical Hardening Stop Bath 

Metric 

I litre Water 

30 grammes Potassium chrome alum 

60 grammes Sodium sulphate (anhyd.) 



Avoirdupois 
80 fluid ounces 
2 ounces 175 grains 
4 ounces 350 grains 



F-5 Acid Hardening-Fixing Bath 

Metric 

240 grammes Sodiumthiosulphate(hypocryst.) 

15 grammes Sodium sulphite (anhyd.) 

17 ml Acetic acid (80% solution) 

7.5 grammes Boric acid 

15 grammes Potassium alum 

I litre Water to make 



Avoirdupois 

19 ounces 90 grains 

I ounce 90 grains 

I fl oz 170 minims 

260 grains 

I ounce 90 grains 

80 fluid ounces 



F-6 Acid Hardening-Fixing Bath 

A modification of formula F-5 which has much less tendency to give off sulphur 
dioxide fumes when used at temperatures above normal. This characteristic can be 
eliminated almost entirely by omitting the boric acid in the F-5 formula above, and 
substituting twice its weight of 'Kodalk' Balanced Alkali. 

Kodak 'Unifix' Powder (alternative to F-5) 

Available from Kodak Limited, as a fully compounded chemical. 



HE- 1 Hypo Eliminator 

Metric 

500 ml Water 

125 ml Hydrogen peroxide 3% solution 

(10 vol. solution as purchased) 
100 ml Ammonia (3% solution) 

I litre Water to make 



Avoirdupois 

40 fluid ounces 



10 fluid ounces 

8 fluid ounces 

80 fluid ounces 

Mix just before use and store in an unstoppered container. To make an approxi- 
mately 3% ammonia solution, dilute I part of 0.880 ammonia with 9 parts of water. 



GN-5 



26 



GP-I Gold Protective Solution 

Metric Avoirdupois 

750 ml Water 60 fluid ounces 

10 ml *Gold chloride (1% stock solution) 385 minims 

10 grammes Sodium thiocyanate 350 grains 

I litre Water to make 80 fluid ounces 

*A 1% stock solution of gold chloride is made by dissolving I gramme in 100 ml of 
water. 

Add the gold chloride stock solution to the volume of water indicated. Separately, 
dissolve the sodium thiocyanate in 10 fluid ounces (125 ml) of water. Then add the 
thiocyanate solution slowly to the gold chloride solution, while stirring rapidly. 
For best results, GP-I solution should be mixed immediately before use. 



T-la Hypo Alum Sepia Toner 

Metric Avoirdupois 

700 ml Cold water 56 fluid ounces 

120 grammes Sodium thiosulphate (hypo cryst.) 9 ounces 260 grains 

Dissolve thoroughly and add the following 

160 ml Hot water at about 70°C (1 58°F) 12 fluid ounces 

30 grammes Potassium alum 2 ounces 175 grains 

Then add the following solution (including precipitate) slowly to and while rapidly 
stirring the hypo-alum solution. 

16 ml Cold water |i fluid ounces 

I gramme Silver nitrate (cryst.) 32 grains 

I gramme Sodium chloride 32 grains 

After combining the above solutions, make up to the final quantity. 

1 litre Water to make 80 fluid ounces 

NOTE: The silver nitrate should be dissolved completely before adding the sodium 
chloride, and immediately afterwards the solution containing the milky white pre- 
cipitate should be added to the hypo-alum solution, as directed above. The 
formation of a black precipitate in noway impairs the toning action of the bath. 



27 GN-5 



Product names quoted thus 

'KODAK' 

are trade marks 



Kodak Data Booklet KODAK LIMITED LONDON 

GN-5 

PDGN-5/xWPI2/3-70 



MAKING MONOCHROME NEGATIVES 
FROM COLOUR TRANSPARENCIES 



Monochrome copy-negatives are frequently required from positive colour 
transparencies so that black-and-white prints may be produced. 

It is possible to make these copy-negatives either by contact or by 
projection, but particularly when any spotting or retouching is to be 
undertaken, it is recommended that copy-negatives be made by projection 
in an enlarger, which should be of precision type fitted with a high-grade, 
colour-corrected, enlarging lens. Some form of hood may need to be im- 
provised to ensure that no stray light can escape from the lamphouse or 
negative carrier. The negatives should preferably be made on film no 
smaller than 2|x3| inches (5.7x8.3 cm), as this greatly facilitates any 
necessary handwork. It is this enlarging technique, in which the negative 
is produced on one of the recommended sheet films, which is described 
herein. 

The film used should give a long range of tone values, but in the great 
majority of cases it does not need to have a full panchromatic colour 
sensitivity. This is necessary only for those transparencies having 
important areas of red or orange, and in these cases the use of a light 
yellow-green filter over the enlarger lens gives the amount of colour 
correction required when a tungsten light-source is used. Mercury- 
vapour lamps should not be used for this work, but white cold-cathode 
tubes, used unfiltered, are satisfactory with both orthochromatic and 
panchromatic films. 



Details of the method 

1 Insert the colour transparency, emulsion side uppermost, into the 
carrier of the enlarger. 

2 Place a sheet of thin white card, of approximately the same thickness 
as the film being used, in the correct position on the baseboard. If a 
darkslide or film sheath is to be used, load it with the card before placing 
it in position. Use this card for focusing, after which it should be re- 
placed by the film, under appropriate safelighting. 

3 The exposure, which should be determined by trial, should then be 
made; avoid over-exposure. If the exposure time is to be controlled 
manually, adjust the lens aperture to give an exposure of at least 15 
seconds in order to gain accuracy and reproducibility. With panchro- 

Issue D Kodak Data Sheet 

GN-6 



matic films, if a tungsten light-source is used, make the exposure through 
a Kodak 'Wratten' Filter No. 11. 

4 Develop the exposed film. 'Kodak' D-76 Developer (undiluted) is 
recommended; the developing time will probably come within the range 
given in the table below, but the time should be determined by trial as 
it may vary according to the quality of the transparency and the type of 
copy-negative required. 

5 Subsequent rinsing, fixing, washing, and drying operations are normal. 
Recommendations for each film may be found in the appropriate Data 
Sheet, the numbers of which are given below. 

Films and their development in KODAK D-76 Developer (undiluted) 



'KODAK' SHEET FILM 



DATA 

SHEET 

NUMBER 



DEVELOPING TIME 

(in minutes) 

AT 20°C (68°F) 



Continuous 
agitation 



Intermittent 
agitation* 



Commercial Ortho4l80 ('Estar' Thick Base) 
'Tri-X' Ortho 4163 ('Estar' Thick Base) 
'Plus-X' Pan Professional 4147 ('Estar' Thick 

Base) 

'Tri-X' Pan Professional 4164 ('Estar' Thick 

Base) 



FM-35 
FM-36 
FM-37 



6-71 
5—7 

4±-6 

S— 7 



6i-9 



6—8 



r With thorough agitation for 5 seconds every minute. 



Kodak, Wratten, Tri-X, Estar and Plus-X are trade marks 



Kodak Data Sheet 
GN-6 



KODAK LIMITED 

Printed in England 
Y 1 306PDGN-6/xWP 1 2/4-73 




METHODS OF INCREASING EMULSION SPEED 



It is sometimes desirable to increase the emulsion speed of a sensitized 
photographic material above that which is given by normal processing. 
The sensitivity produced during the manufacture of the material is as 
high as can be obtained without introducing undesirable effects, but there 
are several methods of treating the emulsion just before or after exposure 
which often produce a little extra speed, although this is normally accom- 
panied by increased fog, contrast and graininess, and reduced resolution. 
There is usually little advantage in undertaking these procedures with 
medium-speed or low-speed materials unless known under-exposure has 
occurred, since it is far easier to substitute a faster material. However, 
in the case of known under-exposure of a serious degree, the main part of 
the subject is on the toe of the characteristic curve and the contrast is 
insufficient, even when using a high-contrast printing paper, to produce 
detail in the shadows. The methods of increasing the speed of the 
material, therefore, are mainly concerned with increasing the contrast of 
the toe regions sufficiently to enable shadow detail to be recorded in 
the print. 

The various methods of increasing speed that are described below do 
not always give similar results with different types of materials. It is, 
therefore, advisable to evaluate the method under controlled conditions 
with the type of material to be used before a valuable exposed material 
is treated. The appropriate safelighting must be used in all cases. 

CHEMICAL METHODS 
Prolonged development 

Some extra speed can often be produced by increasing the development 
time two or three fold, or even longer, in most types of developer such as 
'Microdol-X', D-76, D-23, etc. The toe contrast is increased, but un- 
fortunately the overall contrast of the negative is also increased. Thus, 
this method should be used only when the brightness range of the subject 
is low or when gross under-exposure has occurred. Under these condi- 
tions, the method can be very useful. The speed increase is accompanied 
by an increase in fog and usually by an increase in graininess. 

Bathing treatments 

Chemical Hypersensitization (Pre-Exposure): With this treatment the 
material is usually bathed in the recommended alkaline sensitizing agent 
and is dried prior to the exposure in the camera. The best effect is 
obtained when the concentration of sensitizing agent and the time of 
treatment are such that about twice the normal fog value is obtained. 

A typical procedure is as follows: — The material should be bathed 
before exposure in a 4 per cent solution of ammonia (sp.gr. 0.88), or in 
a 0.5 per cent aqueous solution of triethanolamine for 2 minutes at 13°C 
(55°F). After bathing, the excess solution should be carefully removed 
from the material with a viscose sponge and the material dried as quickly 
as possible at normal room temperature. 

Issue A Kodak Data Sheet 

GN-7 



The low temperature of this treatment is recommended to minimise 
swelling of the emulsion during immersion, and to ensure rapid drying. 
The material should be used as soon as possible after treatment, the speed 
advantage being lost after about one month. On subsequent development 
the addition of 'Kodak' Anti-Fog Powder to the developer will help to 
lower the fog density. 

Chemical Latensification {Post-Exposure) : This treatment of the material 
is given after the camera exposure. When using roll films it is more 
convenient than treatment before exposure since it is not necessary to 
replace the backing paper, etc. A satisfactory method of treatment is 
by the use of an aqueous sulphite solution. 

Increases in speed up to nearly 100 per cent have been obtained on 
high-speed negative materials with this method, details of which are as 
follows: — After exposure the material should be bathed for about 5 
minutes at 20°C (68°F) in a solution of 175 grains (5 grammes) of potassium 
metabisulphite and 300 grains (8.5 grammes) sodium sulphite (anhydrous) 
per 80 ounces (1 litre). The pH of this solution will be about 6.0. The 
material should be well drained or squeegeed, and dried as quickly as 
possible at normal room temperature. When the film is thoroughly dry 
it should be developed in the conventional manner. 

The fog density that is produced is slightly higher than normal and 
the grain slightly coarser. 

Vapour treatments 

Chemical Hypersensitization (Pre- Exposure): A common method of 
undertaking this treatment is the use of mercury vapour. The method, 
however, is rather erratic and it is very necessary to experiment with the 
particular emulsion to be used in order to obtain optimum conditions of 
time, temperature, humidity, etc. The conditions as found should then 
be followed strictly. 

A non-metallic container is required which can be well sealed. The 
material should be removed from any metal reel and placed in the con- 
tainer alongside an open jar containing a small quantity of liquid mercury* 
— about the size of a pea. The lid of the container should then be tightly 
sealed. Treatment times of 2, 4, 8, 16, and 32 hours should be given, 
after which the trial material should be developed. The time that gives 
the best increase in speed with acceptable fog can readily be chosen by 
visual examination. As with the pre-exposure bathing treatment, the 
speed increase obtained with mercury vapour is gradually lost on keeping. 
The camera exposure should be made as soon as possible after the 
treatment. 

Chemical Latensification (Post-Exposure) : The same procedure should be 
undertaken as is recommended for pre-exposure chemical hypersensitiza- 
tion, but the treatment is given after the camera exposure. The same 
disadvantages apply, such as the need for precise control of conditions 
and the somewhat erratic behaviour of the method. Here also, it is 
necessary to accept an increase in fog in order to obtain a worthwhile 
increase in speed. 

* Warning: Great care must be exercised in the handling of mercury. It should never be kept in 
an unstoppered bottle in the darkroom owing to the danger of fogging photographic materials. 

GN-7 2 



Intensification after development 

The concept of increasing the effective speed by treatment of the 
negative after development and fixing may appear paradoxical at first but 
it should be emphasized that the emulsion speed is defined in terms of 
the exposure required to reach a certain density of gradient. 

If printing papers of sufficient contrast to print a very weak negative 
are not available, the image can be intensified to increase the contrast and 
produce a more nearly normal print with the available printing papers. 
If by this means printable detail is produced in a negative previously too 
weak to print on the most contrasty paper available, the speed of the 
emulsion for extreme under-exposure has been effectively increased. 

Where extreme under-exposure has occurred, the maximum degree of 
intensification will usually be required and for this purpose the Kodak 
formula IN-6 Quinone-Thiosulphate Intensifier (formula in Appendix) is 
recommended, particularly for use with high-speed negative materials. 

After developing and fixing the negative, it should be washed for 5-10 
minutes in running water. The emulsion should not be touched with 
the fingers, either prior to or during intensification, otherwise surface 
markings may be produced. If a previously processed negative is 
required to be intensified, any finger marks should be removed by swab- 
bing the emulsion surface with cotton-wool moistened with benzene. 

Negatives, whether dry or freshly processed, should be hardened for 
5 minutes at 20°C (68°F) in Kodak formula SH-1 Formalin Hardener 
(formula in Appendix), followed by a 5-minute wash in running water. 

After hardening and washing, the negative should be immersed in the 
intensifier and given maximum agitation to avoid streaking. 

The maximum degree of intensification is obtained in about 10 minutes at 
20°C (68°F); for a lower degree of intensification the treatment should be 
given for a shorter time, inspecting the negative at intervals. The nega- 
tive should then be washed for 10 to 20 minutes in running water and 
dried in the normal way. 

The chief disadvantages of this method of intensification are the 
excessive contrast produced in the normal exposure range, and the relative 
instability of the toned image. However, it does offer an opportunity to 
increase the effective speed in cases where the under-exposure is not 
recognised until after processing. 

PHYSICAL METHODS 

It is often possible to increase the effective speed of a photographic 
material by a uniform exposure to light, which according to the circum- 
stances may be given either before or after the exposure it is desired to 
record, described as the camera exposure. 

In order to understand the principle underlying these methods, latent- 
image formation may be compared with the well-known processes of 
crystallisation or the formation of water drops in the atmosphere (fog or 
clouds). Exposure of the silver-halide grains in a photographic emulsion 
layer will cause any one grain to become developable, providing at least 
one of the latent-image specks formed on it is sufficiently large. Latent- 
image formation can thus be regarded as a condensation process in any 

3 GN-7 



one emulsion grain, and this can be considered as being representative 
of the emulsion as a whole. 

In order to form a fine precipitate, the process of crystallisation has to 
be rapid, whereas if it is required to obtain large crystals, crystallisation 
has to be slow and deliberate. This applies also to latent-image forma- 
tion; if a brief exposure at high intensities of light is given, the latent 
image tends to be in a highly dispersed form, i.e., on any one grain a 
number of small latent-image specks are obtained. With long exposures 
at low intensities, the latent image tends to be in the form of relatively 
large specks, few in number. 

The only other fact that has to be appreciated is the occurrence of 
low-intensity reciprocity failure in photographic materials, i.e., as the 
intensity of light decreases its photographic effect steadily diminishes. 
In order to obviate this effect the time of exposure has to be increased 
in a greater proportion than would be expected from the intensity drop. 
Whereas the product Ixt, of intensity / and time t, measures the total 
amount of light falling on the photographic material, the factors I and t 
fail to act reciprocally in their photographic effect, so that larger values of 
Ixt are required to produce the same effect the lower the intensity and 
the longer the time of exposure. 

The basic reason for reciprocity failure at low intensities is the insta- 
bility of a latent image in its very early stages of formation; a small 
speck may be formed and may disintegrate again before it is built-up to 
a stable size. As a result of this, exposures at low intensities of light 
often have to be many times that necessary for an exposure at more 
normal times and intensities such as in snapshot photography. 

Both methods here described, hypersensitization and latensification by 
light, are capable of giving the ultimate speed of which a photographic 
material is capable. As they utilise the grains without affecting their 
size in any way they do not in themselves cause any increase in graininess, 
although if the veil produced by the uniform exposure is high, an increase 
in graininess will be produced. The change in curve shape caused by 
exposure addition may also result in changes in the resolving power and 
sharpness of the picture. 

Hypersensitization by light (p re-exposure) 

The inefficiency of latent-image formation at low intensities and long 
exposure times can sometimes be overcome by ensuring that emulsion 
grains carry latent-image specks (sub-image), in their early stages of 
formation. These specks are so small that they do not cause the grain 
to develop, but they are sufficiently large to be stable. This can be 
achieved by giving the photographic material a uniform exposure before 
the camera exposure. The time of this pre-exposure should be between 
l/10th and l/100th second, and the intensity adjusted to obtain optimum 
sensitivity under the conditions of the camera exposure which is to 
follow the pre-exposure. Where it is not possible to establish optimum 
conditions for the pre-exposure, a rough-and-ready rule is to arrange for 
it to be undertaken at an intensity which causes the veil to reach a density 
level of 0.2 — 0.3 above the inherent "chemical" fog of the emulsion. 
The time for this uniform exposure should not be shorter than 1/ 100th 

GN-7 4 



second because it would then form latent-image specks in the interior of 
the grains ; this, in general terms, would have the effect of desensitizing 
the grains towards further exposure (Clayden effect). No actual de- 
sensitization may be observed, but the effect may be shown by the fact 
that a very brief uniform exposure is less effective in sensitizing the 
emulsion than an exposure at the recommended exposure time. 

The increase in sensitivity which can be obtained in this way is often 
spectacular and is greater the longer the time of the camera exposure. 
There is usually some distortion of curve shape in the sense that the fast 
grains tend to be increased in sensitivity more than the slower ones. The 
characteristic curve will have a longer toe and the contrast will be lowered. 

In principle, the effect of the pre-exposure does not depend on the 
colour of the light used as long as it results in the production of a density, 
but in order to sensitize the grains as fully as possible throughout the 
depth of the emulsion layer, it is desirable to use light of as long a wave- 
length as possible, as longer wave radiation will more effectively penetrate 
the emulsion layer. 

To keep the fog level low, it should be remembered that a latent image 
formed by a low-intensity exposure, for which this method is useful, 
develops more rapidly than that due to an exposure at more normal 
intensities, simply because the latent-image specks formed at the low 
intensities tend to be large. There is, therefore, no point in prolonging 
the time of development unduly as it would increase the fog. 

Intensification by light (post-exposure) 

The fact that the latent image is produced in the form of numerous 
small specks, for exposures of short duration and at high intensity, results 
in an inefficiency of latent-image formation : a small speck is less readily 
developable than a larger one. The latent-image specks can be built-up 
in size and then develop more rapidly if the camera exposure is followed 
by a uniform exposure of long duration and low intensity. This will 
tend to build up the latent-image specks which are present in the grains 
as a result of the camera exposure, but will have little effect in the un- 
exposed grains, which are subject to reciprocity failure at low intensities, 
at which the uniform second exposure is being given. 

As with hypersensitization, the best level of exposure can be ascertained 
accurately only under the conditions of use, i.e., under the exposure levels 
and the development conditions to be used. However, results not far 
from optimum will be obtained if the time for the uniform exposure is 
around 30 minutes, and the intensity such that a uniform density is 
produced of between 0.2 and 0.3 above the inherent fog of the material. 

The degree of latensification obtainable with any one material under a 
given set of exposure conditions depends to a large extent on the develop- 
ment; in fact, it is convenient to think of latensification as a method of 
developing the latent sub-image. Thus, if development is heavy, the 
effect of latensification is small, but for short development latensification 
may have a very large effect. 

The effect of latensification also varies with the exposure conditions 
themselves, and in general is greater the shorter the time of the camera 
exposure. A very large effect might be obtained with flash pictures, 

5 GN-7 



whereas at ordinary exposure levels (e.g., l/25th second) the effect may 
be small; it may be almost entirely absent with exposure times running 
into minutes. 

It may be thought that latensiflcation and development being inter- 
dependent, little might be gained by applying a latensiflcation treatment. 
This is not so, since a combination of latensiflcation and development 
will allow a large measure of control over the curve shape of the photo- 
graphic material. As the time of development is increased, the contrast 
of a photographic material builds up, and for this reason development 
cannot always be continued sufficiently for full speed to be obtained. 
This often applies for exposures at high intensity and of short duration. 
The latensiflcation treatment is most effective for the fastest grains and 
thus may be used to obtain both optimum speed and a reasonably low 
level of contrast. 

APPENDIX 

Kodak Quinone-Thiosulphate Intensifier — Formula IN-6 

Solution A 

Metric Avoirdupois 

750 ml . . Distilled water (about 2 l°C—70°F) . . 60 ounces 

30 ml . . Sulphuric acid (concentrated) .... 2 ounces 96 minims 

22.5 grammes . Potassium bichromate I ounce 350 grains 

I litre . . Distilled water to make 80 ounces 

Add the sulphuric acid to the water very gradually and with constant stirring. 

Solution B 

750 ml . . Distilled water (about 21 °C— 70°F) . . 60 ounces 

3.8 grammes . Sodium bisulphite 133 grains 

15.0 grammes . Hydroquinone I ounce 88 grains 

20 ml . . 'Kodak' Wetting Agent (10% solution) . I ounce 270 minims 

I litre . . Distilled water to make 80 ounces 

Solution C 

750 ml . . Distilled water (about 2I°C—70°F) . . 60 ounces 
22.5 grammes . Sodium thiosulphate (hypo cryst.) ... I ounce 350 grains 
I litre . . Distilled water to make 80 ounces 

For use, add 2 parts of solution B to I part of solution A while stirring; then add 
2 parts of solution C, continue stirring and finally add I part of solution A. The order 
of mixing is important and should be followed. 

In stoppered bottles, solution A is stable indefinitely; solutions B and C remain 
stable for several months. Solution B should be discarded when it becomes appreci- 
ably coloured, the colouring indicating oxidation. Solution C should be discarded 
if a precipitate forms indicating sulphurization. 

Kodak Formalin Hardener — Formula SH-I 

10 ml . . Formalin (40% formaldehyde solution) . 360 minims 

5 grammes . Sodium carbonate (anhydrous) .... 175 grains 

I litre . . Water to make 80 ounces 

This solution should be used as indicated in the text. 



Kodak and Microdol-X are trade marks 

Kodak Data Sheet KODAK LIMITED LONDON 

GN-7 

PDGN-7/r3WPI/l2-70 



THE CEMENTING OF COLOUR OR MONOCHROME 
MINIATURE TRANSPARENCIES TO GLASS 

There are occasions when it is desirable to cement colour or monochrome 
transparencies to glass — particularly when a transparency must be held 
flat despite exposure to warm conditions. 

The widely-followed practice of binding a transparency between two 
pieces of thin glass provides considerable protection from dust, finger- 
prints and scratching, but it is not a completely satisfactory solution of the 
mounting problem. Buckling frequently occurs when transparencies are 
displayed and Newton's rings are very often apparent in the projected 
image of miniature transparencies. In these and other similar cases the 
cementing of a transparency emulsion side down to glass may provide a 
more effective method of mounting. 

For this purpose, glass should be of good quality and free from bubbles 
and strains. Its thickness should be adequate to give rigidity, yet not 
sufficient to cause undue absorption of heat and subsequent breakage; 
a thickness of 0.04 or 0.05 inch should be satisfactory. 

In cementing transparencies to glass, cleanliness in all the operations 
is of paramount importance, since if dust particles are embedded in the 
cement they will cause air bells and poor adhesion, and will be seen on 
projection. If the surface of the transparency or glass is contaminated 
with oil or grease, poor adhesion will result. Proper cleaning of the glass 
and transparency, and the use of a camel-hair dusting brush or rubber 
bulb are recommended. 

In cementing transparencies, emulsion side to glass, proper adhesion 
must be ensured. A gelatin solution containing a suitable wetting agent 
has been found to produce satisfactory results. Gelatin-coated glass is 
more suitable than uncoated glass in that it not only gives greater final 
adhesion, but also considerable initial adhesion, because of the immediate 
absorption of moisture from the cement. The gelatin coating also serves 
to prevent air bells from occurring during the cementing operation; 
particles of dust which normally may cause this trouble, become embedded 
in the gelatin coating and are covered with cement. When gelatin-coated 
glass cannot be obtained suitable glass should be coated with gelatin and 
dried. Alternatively, thoroughly fixed-out, washed and dried photographic 
plates or lantern plates should be used. 

After cementmg a transparency to glass, adequate drying time should 
be allowed, since the heat of a projector may cause bubbles owing to 
vaporization of residual moisture at the emulsion-glass or emulsion-base 
interface. Just how dry the laminated transparency must be depends on 
the conditions of projection, but a few trials will determine the proper 
drying time. Desiccants are of value in reducing the drying time, or pre- 
ferably, if equipment is available, a vacuum pump, providing that not too 
high a vacuum is used. This may reduce the normal drying time of about 
8 hours to something of the order of 1 to 2 hours. 

Most recently-processed transparencies adhere satisfactorily, and 
transparencies, in which the emulsion is thoroughly dried out, Old 

Issue A Kodak Data Sheet 

GN-8 



particularly those which have been projected frequently, may not adhere 
so firmly to the glass. Transparencies which have a serious curl or are 
bent or cracked may not cement successfully even though recently pro- 
cessed. If any wetting agent is used during processing a thin film remains 
on the emulsion surface of the transparency and causes difficulty in 
obtaining proper adhesion. 

The first transparency chosen for cementing should be one to which 
little value is attached, since the various procedures outlined below require 
a certain skill in handling; for best results, a transparency should be newly 
processed and flat. 

PROCEDURE FOR CEMENTING 'KODAK' COLOUR TRANSPARENCIES 

1 Removal of Transparency from Mount. Most 35mm and 'Bantam' trans- 
parencies, when returned from processing, are mounted in Ready- 
Mounts, and such a transparency must be removed from its mount. The 
best method is to cut off, with a pair of sharp scissors, a strip one-quarter 
of an inch wide from the top of the mount. The mount can then be pulled 
apart and the transparency removed without twisting. Most 'Ektachrome' 
4x4 cm transparencies, also known as Superslides, are returned from 
processing mounted in Superslide Ready-Mounts; such mounts may be 
opened by cutting a strip one-eighth of an inch wide from the top of the 
mount, and the transparency removed as described above. 

2 Cleaning the Transparency. The emulsion side of the transparency, 
particularly, should be thoroughly clean and free from oil or grease. The 
use of 'Kodak' Movie Film Cleaner is recommended. If the trans- 
parency has been lacquered it is essential that this lacquer be removed 
before proceeding further. Recommendations for the removal of the 
lacquer may be obtained on application. 

3 Registration of the Transparency on the Glass Plate. The transparency 
should next be placed on a piece of clean, dry cloth or 'Fotonic' Photographic 
(blotting) Paper, with its base side uppermost, and a piece of cellulose 
tape attached to one of the long edges of the transparency, allowing 
the tape to overhang about half its width. This piece of tape should 
be the same length as the transparency or slightly shorter. A glass 
plate, with its gelatin-coated side uppermost, should then be laid along- 
side the transparency on the piece of cloth or paper. The taped trans- 
parency is then held over the plate until it is seen to be in the correct 
position, and the tape pressed down firmly. 

4 Cementing. Using the thumb and forefinger, the glass plate should 
be picked up by the corners opposite the edge to which the transparency 
is attached. With the other hand, the transparency should be folded 
back away from the glass — the tape acting as a hinge — and any loose dust 
or particles removed by the use of a rubber bulb or a soft camel-hair 
brush. The transparency only should then be completely immersed in 
a gelatin solution prepared according to the formula given in the Appendix. 
It will cause no difficulty if a small portion of the glass must be immersed 
in order to coat the film thoroughly. 

GN-8 9 



After complete immersion the film should be removed from the solution. 
While the film is held clear of the glass, the edge of the glass nearest to and 
parallel with the tape, should be inserted between the rollers of a wringer* 
and, with a slow, even motion, the transparency should be rolled into con- 
tact with the glass. 

The film must be rolled down into contact with the glass — not allowed to fall 
against the glass as it is rolled through the wringer, since this may trap air 
between the two surfaces. 

5 Cooling and Cleaning the Cemented Slide. Immediately after being 
rolled through the wringer, the slide should be dipped in a dish of cold 
water containing Kodak 'Photo-Flo' solution (in the dilution recom- 
mended). It is important that the water be cold as the purpose of this 
step is to set or harden the gelatin. After immersion for about 10 
seconds the slide should be removed and the tip of the fingernail used to 
prise up one corner of the tape by which the transparency was originally 
fastened to the glass plate. The tape should be carefully pulled away 
from the film at an acute angle. The slide should then be re-immersed 
in the water, and the film gently rubbed with the finger to remove any 
excess gelatin. 

The slide should be allowed to drain for a few seconds, and examined 
by both reflected and transmitted light to see if any air bubbles or defects 
in the cementing are detectable. If the cementing is imperfect, the 
transparency can be removed by the method given in the next step and 
re-cemented as above. If the slide is seen to be satisfactory it should be 
placed in a rack to drain and dry. It is not necessary to wipe the slide 
dry as the 'Photo-Flo' in the water will cause it to dry evenly and without 
leaving spots. This step normally takes about 8 hours at room tempera- 
ture; other methods of drying can reduce this time (see page 1). 

6 Removing Improperly Cemented Transparencies. Transparencies 
cemented to glass by the above process can be removed, washed, dried, 
and re-cemented. This step is an emergency measure, however, and 
should be used only when necessary, as it is usually more difficult to 
re-cement the transparency satisfactorily and since slight colour changes 
may occur. 

If the transparency is to be removed immediately after cementing and 
before the cement has had an opportunity to set, the slide should be held, 
with the transparency upwards, in a stream of warm running water, the 
temperature of which should not be so high that it is unbearable to the 
hand. After the slide has been in the stream of water for about 30 
seconds, a corner of the transparency should be prised up and the warm 
water allowed to run into the opening. With the fingers, and very gently, 
the transparency should be pulled away from the glass, but only as rapidly 
as the softening of the gelatin will permit. The glass should be discarded 
and the transparency held under the warm water, and the emulsion side 
rubbed gently with the fingers to remove any gelatin which may be left on 

*The wringer used in this step may be any hand-operated rubber-roller wringer, but the rollers 
must be soft and smooth with no uneven surfaces, and should turn freely. The pressure should 
be adjusted so that the sandwich can be rolled through without difficulty. After each slide, the 
rollers should be cleaned of any gelatin by rubbing them with a cloth wet with warm water. Leaving 
gelatin on the wringer rollers will cause the surface to become hard and rough. 

3 GN-8 



it. It is possible to tell if any gelatin is still present because it will feel 
softer and more slippery than the emulsion of the transparency. 

If the cemented slide has already dried, it should be dropped into a 
container of warm water at a temperature of about 38°C (100°F) and 
allowed to soak for about 24 hours. The water may be allowed to cool 
to room temperature. After soaking, the transparency can be removed 
by following the procedure given above. 

The transparency which has been removed from the glass slide and 
washed free of gelatin should be set or hung upright in a dust-proof 
position, such that the emulsion side, which has been softened by the warm 
water, cannot be scored by contact with any object, or pick up dust or fluff 
before it has become dry and firm again. It should be allowed to 
dry for about 8 hours at room temperature before re-cementing is attemp- 
ted. 

7 Binding and Masking. Cemented and dried slides can be used without 
cover glasses or masks, but this is not advisable. The cover glass protects 
transparency against scratches and dirt, and a white or bright reflecting 
sheet-metal mask will help to protect the transparency from the heat of the 
projector. 

'Kodak' Slide Cover Glasses are available, and a satisfactory type 
of mask can be made from thin sheet metal such as 0.010 inch aluminium 
or thinner. These can easily be made to specification by a sheet-metal 
company. 

PROCEDURE FOR CEMENTING MONOCHROME TRANSPARENCIES 

The procedure for cementing monochrome transparencies to glass is 
almost identical with that used for colour transparencies except as regards 
the type of cement used and the manner of setting. 

The cement consists of a 50 per cent lactic acid solution made with 
distilled water. This solution should keep for about two months. 

After the cementing operation, the cement should be set by dipping 
quickly in and out of a cold 'Photo-Flo' solution (in the dilution recom- 
mended) and the slide then swabbed with the finger. Prolonged immersion 
in cold water as in Step 5, is not desirable, since it has been found that the 
water tends to creep under the transparency, thereby weakening the bond. 



GN-8 



APPENDIX 

Gelatin Adhesive 

Metric Avoirdupois 

1000 cc .... Distilled water 80 fluid ounces 

100 cc .... 'Photo-Flo' I per cent solution* . 8 fluid ounces 
22 grammes . . . Gelatin I ounce 325 grains 

*This should be prepared by diluting the concentrated 'Photo-Flo' solution as follows: 

'Photo-Flo' 600 I part plus 99 parts distilled water 

'Photo Flo' 200 3 parts plus 97 parts distilled water 

This adhesive should be heated to approximately 38°C (100°F) and 
stirred constantly; at this temperature it should become clear. It should 
be allowed to cool to room temperature before use, but if it has become 
too viscous it may be slightly re-heated. 



GN-8 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

KODACHROME 

EKTACHROME 

PHOTO-FLO 



Kodak Data Sheet KODAK LIMITED LONDON 

GN-8 

YI200PDGN-8/r4WPi/l 1-71 



NEGATIVE QUALITY 



The desiderata of negative quality have varied in some respects with 
changes in photographic practice, and the continuous trend to the use of 
smaller negative sizes over the past forty years or so has involved some 
reassessment of negative quality. 

Furthermore, some of the classical teachings have become obsolete 
because they have been recognised to be unsound; for example, the 
accepted doctrine at one time was that the prime requirement of ideal 
negative quality was that all the tones of the negative should fall on the 
straight-line portion of the characteristic curve. It is true that this means 
that the intensities of light transmitted through the various parts of the 
negative correctly represent, in an inverse sense, the brilliancies of the 
various areas of the scene; but it is not true that this ensures a correct 
transcription of tones in the print made from such a negative, whether as 
a paper print or a transparency. A correct transcription could, in fact, 
be obtained by printing a positive transparency such that all the tones of 
the image again fell on the straight-line portion of the curve of the trans- 
parency material. But this is not what normally occurs in practice, and 
as soon as one comes to make a positive print on paper the characteristic 
curve of the paper comes into and complicates the matter. In fact the 
deficiencies in the tone-rendering characteristic of the paper can be 
partially compensated for by the deviations of the negative from the 
straight-line relationship, and in the end the nearest approach to perfect 
tone reproduction in the print is obtained when the camera exposure is 
somewhat curtailed. When the camera exposure is short enough to 
place the shadow tones of the subject on the "toe" of the characteristic 
curve of the negative material, the overall tone reproduction in the print 
tends to be at the optimum. This is one justification for the modern 
practice of reducing camera exposures to the minimum. 

Early workers in photography made contact prints from large negatives. 
Their interests were considered to be best served by films having the 
maximum exposure latitude, which led to the introduction of double- 
coated roll films capable of recording a colossal range of exposures. 
Present-day workers, however, make enlargements from small negatives, 
and it has been shown* that enlargements make more obvious the loss in 
quality in the negative due to over-exposure. Also, it becomes unreason- 
able to attempt to print exceedingly dense negatives in an enlarger. Hence 
the demands of modern practice have shifted again towards materials of 
relatively modest exposure scale, not necessarily with a well-marked, 
extended "straight-line" characteristic. 

REQUIREMENTS OF MODERN PRACTICE 

The requirements of negative quality in current photographic practice 
are concerned with: 

(a) tone gradation 

*C. N. Nelson, Safety Factors in Camera Exposures, Photographic Science and 
Engineering, 4, No. 1, Jan/Feb. 1960, pp. 48-58. 

Issue C Kodak Data Sheet 

GN-II 



(b) fineness of grain (which determines image resolution) 

(c) sharpness of definition 

Tone gradation 

Most practical workers agree that it is desirable, from the points of 
view of print quality and working convenience, to adopt a working pro- 
cedure by which the majority of average negatives print best on to 
medium-contrast paper under normal conditions of enlarging. This may 
be regarded as the first touchstone by which working methods may be 
checked. 

Producing negatives which satisfy this test is pardy a question of 
suitable exposure, pardy of suitable degree of development. As a 
practical guide to the judging of exposure levels it may be taken that — 
except for particular purposes such as studio work or available-light 
subjects — a negative should have little, if any, clear area: there should be 
slight density and discernible differentiation of tone down into the deepest 
shadow area of the subject in which detail is required. Much modern 
work may appear to conflict with this statement — but much modern work 
of photo-reporting or pictorial kind is much less concerned with photo- 
graphic quality than with "impact". 

With the rendering of shadow detail provided for by this level of 
adequate exposure, it rests with the control of development to allow the 
retention of gradation in the highlight areas of the subject. Any difficulty 
in recording highlight tones in the print implies either a subject having 
an exceptionally long range of tones or development of the negative to 
excessive contrast. With modern printing papers and semi-condensed 
enlarger illumination the densest negative areas should just about allow 
ordinary letterpress print to be read through the silver density, when the 
negative is held almost in contact with the printed sheet in good light. 

One avoidable fault which can play havoc with the quality of a negative 
is lens flare : this can destroy the brilliance and clarity of a negative even 
when it does not produce obvious local fogging of the image. A certain 
amount of scatter of light into the shadow areas of the image — as the 
result of stray reflections within the lens or camera, or scatter from the 
emergent lens surface — is inevitable; but degradation of the image in 
this way should be kept to a minimum by carefully preserving the surface 
polish of the lens, by regularly cleaning the external lens surfaces, and by 
shielding the lens from the direct light-beam in back-lit subjects. The 
degree of flare by reflection from the walls of the camera is in fact one 
of the finer points to observe when selecting the camera in the first place. 

Fineness of grain 

Though the fineness or coarseness of grain is primarily a characteristic 
of the material and largely determined by its speed, both the exposure 
and the development of the film or plate have some effect on negative 
quality in this respect (see Data Sheet PR-2). Fine-grain quality in the 
negative is best preserved by keeping the camera exposure down to the 
minimum, and by using a developer of fine-grain or extra-fine-grain type. 

GN-II 2 



i 



The fineness of grain of a silver image is bound up with, and sets a 
limit to, the image resolution. This is concerned with the magnitude of 
details which can be distinguished in the image. It determines for 
example, whether or not the individual hairs in an animal's fur can be 
discerned in the image, and whether or not the facial area of an enlarged 
portrait appears as an even tone or broken up into an irregular pattern 
of minute grains. While fineness of grain and the resulting smoothness 
of tone is generally regarded as a desirable feature, it is considered by 
some that a granular image structure forms part of the aesthetic appeal 
of certain pictorial printing processes. 

Faulty control of the temperatures of processing solutions can cause 
micro-reticulation to occur so that course grain is simulated, even with a 
fine-grain emulsion. When a low-power magnifier is used to examine the 
image, a minute net-like structure can be seen. This is caused by 
the contractile and expansive forces which are present when variations 
in temperature occur, resulting in a pattern of ridges and valleys in the 
surface of the emulsion. 

Sharpness of definition 

Only comparatively recently has it been realized that the visual quality 
of a photographic image is not determined simply by the fineness of 
grain of the silver deposit forming the image. In fact there is a further 
factor, that of image sharpness, which may work in the directly contrary 
sense. Recognition of this factor arose out of the observation that one 
image which appears visually sharper than another may in fact be notice- 
ably coarser in grain. 

The distinction between the two factors may perhaps be put in this 
way: whereas it is the fineness of grain (or resolution) of the image which 
separates one hair from another in a picture of a girl looking out of a 
window, it is the image sharpness which determines whether the frame 
of the window appears perfectly clear-cut or not. 

Image sharpness is concerned with the abruptness of the change in 
density along the hard line of separation between a light area and a 
dark area. 

Assuming an optical system which forms a sharp image of such a line 
of demarcation, there are two properties of the photographic emulsion 
which determine the degree of sharpness of the resulting line in the 
developed image. The sharpness of the fine suffers blurring first as the 
result of scatter of light within the emulsion, by reflection of light from 
one illuminated grain of silver halide towards neighbouring non-illumi- 
nated grains: this form of light scatter in all directions through the 
turbid emulsion is known as "irradiation". Blurring of a different kind 
occurs if light rays penetrating right through the emulsion reach the base 
and are reflected back into the emulsion: this effect is known as halation. 
It occurs typically as a ring of density round a point of highlight, and 
at a slight distance from it. The separation of the "halo" will be much 
smaller with a film material than with a plate owing to the thinner base, 
but it will be evident on close inspection. Halation is normally sup- 
pressed, or minimized, either by means of a dyed backing on the rear 
surface of the film or plate, to absorb light which penetrates to this 

3 GN-ll 



surface; a dyed film base, to absorb light as it passes through the base; 
or a dyed interlayer between the emulsion and the base, to absorb rays 
before they reach the base at all. 

The modern type of "high-acutance" film represents still another 
approach to this problem. By the use of emulsion coatings which are 
much thinner than those normally used in the past, and correspondingly 
of higher turbidity, less opportunity for scatter within the emulsion is 
allowed and the image sharpness is correspondingly increased. These 
"thin-coated" films are thus inherently capable of giving improved image 
sharpness, but they lend themselves in addition to a special processing 
technique which artificially enhances the image sharpness. 

This method involves the use of a developing solution in which the 
developing agent is at a low concentration but the activity is maintained 
by a high alkali content. What happens along the line of demarcation 
between highlight and shadow when such a developer is used is that in 
the highlight area the developing agent is rapidly exhausted and develop- 
ment is checked. But ample developing agent remains in the adjacent 
shadow area, where the light action and consequent development has 
been slight: and as this fresh developing agent diffuses gradually across 
the line between unexposed and exposed areas it gives a further build-up 
of image density just inside the exposed area. At the same time silver 
bromide formed in the area of developed silver density diffuses in the 
other direction towards the lightly exposed area, and as it diffuses across 
the separating line it begins to restrain development on the edge of this 
area. Thus on the dense side of the line there is a fringe of increased 
density, and on the low-density side there is a fringe of decreased density. 
The obvious result of these combined edge-effects is to produce a much 
harder and more abrupt change of density across the line of this edge — 
and a visual effect of much increased sharpness. The term "acutance" 
is applied to an involved mathematical measurement of the rate of change 
of density across this edge, and the modern class of "high-definition" 
developer includes those which are so compounded as to act in this 
special way. 

Camera shake: It is obviously useless to seek improvement of negative 
quality by the avenues of fine grain or high acutance if the image which the 
photographic material itself receives is not sharply defined, and it is essen- 
tial here to emphasize how destructive and deceptive is the risk of camera 
shake. The modern miniature and roll-film cameras are naturally pre- 
dominantly used as hand-cameras: but if it is desired to make the utmost 
of the remarkable quality which these modern instruments permit with 
modern films it should be made a regular practice to use speeds of 1/100 
second or faster whenever the camera is used in the hand. With long- 
focus lenses 1/250 second or less should be preferred. 



Kodak is a trade mark 



Kodak Data Sheet KODAK LIMITED 

GN-II 

YI290PDGN-I I /xWP 1 0/1 0-72 




i 



UNDERWATER PHOTOGRAPHY 



The rapid growth of underwater swimming as a popular sport has led to 
a parallel development of underwater photography, not only for pictorial 
and record work but also as a valuable tool in the fields of marine biology 
and underwater surveying. A number of difficulties arise when a camera 
is taken underwater, and the purpose of this Data Sheet is to provide a 
starting point for photographers faced with the necessity of working 
underwater. 

THE PROPERTIES OF WATER 
Pressure 

The pressure underwater increases by one atmosphere (1 kilogramme 
per square centimetre or approximately 14.7 pounds per square inch) 
for every 10 metres (33 feet) of depth. From this it can be seen that the 
camera must be in a case which is not only watertight but also strong 
enough to withstand considerable external pressure. Cases can be 
pressurized to counteract this effect, but for normal cameras they can be 
designed to operate unpressurized down to 60 metres (200 feet) without 
being too heavy or bulky. 

Refractive index 

Water has a refractive index of about 1.33. This causes objects viewed 
or photographed through a plane porthole to appear one third larger and 
nearer than they really are, as shown in the diagram below. 



APPARENT POSITION 



REAL OBJECT 



LENS 




Optical compensation is possible but is relatively expensive. The 
camera must, therefore, be focused on the apparent distance (A) of the 
subject, or if distances are measured with a rule, the focusing scale of the 
camera must be set to three-quarters of the real distance (B). 

Visibility 

The fact that water is frequently not very clear makes it necessary to 
approach as close as possible to the subject. A wide angle lens is therefore 
the normal choice for most work. Normal and telephoto lenses have their 



Issue D 



Kodak Data Sheet 
GN-12 



applications, however, for photographing small specimens in very clear 
water. 

Colour 

Colour photography underwater is complicated by the fact that water 
is coloured. 1 The absorption of the red component of white light increases 
rapidly with depth. In addition, organic matter, in coastal and most 
fresh waters, absorbs blue light to a varying degree. These absorbtions 
impart a cyan or green colour to unaltered colour photographs ; this is not 
necessarily objectionable, and in fact conveys an "underwater" atmosphere 
to the shots. 

COLOUR FILMS 
Reversal 

For photographs in which the colours of the subject must be correct, 
such as with biological or geological specimens, the colour of the light must 
be corrected. This is achieved in shallow water by means of 'Kodak' 
Colour-Compensating red (R) filters at the rate of 12 CC units per metre 
(per 3.3 feet) of light path (depth + camera-subject distance). For 
instance, with a subject 2 metres deep at a distance of 1 metre from the 
camera, the number of units required to give the necessary correction is 
(l+2)x 12=36. In this case the filter to use is the CC40R. As this 
method is only approximate, calculated correction to within plus or minus 
5 CC units is usually satisfactory. In fresh water lakes and some sea areas, 
the water is greenish rather than cyan and, then, magenta filters should 
be used. 

Below approximately 6 metres (20 feet) the density of the filters required 
makes the use of flash more practicable when correct colour rendering 
is necessary. 

Colour-negative 

At first sight it may appear that anything that is true for reversal films 
will also apply to colour-negative films. This is true if the negatives are 
not to be printed on automatic colour printers. These work on the 
principle that all scenes integrate to a neutral grey, and negatives are 
automatically corrected to yield a print with equal amounts of the three 
dyes — yellow, magenta, and cyan. If a negative of an underwater subject, 
which has not had the full CC filter correction as suggested for reversal 
films, is printed using one of these machines, the print will have cyan 
highlights and red shadows owing to the severe under-exposure of the red- 
sensitive layer. This can be avoided, if the printing is done in a normal 
enlarger, by adding cyan filters to the filter pack until the shadow areas on 
the print just begin to turn brownish. The print will still have an overall 
cyan cast but any more filtration will make the shadow rendering objec- 
tionable. 

GN-12 2 



DESIGN OF CAMERA CASE 

The underwater camera case must be strong enough to withstand the 
pressure. Most commercial cases are made from aluminium alloy cast- 
ings or 'Perspex' plastics. The corrosive effect of sea water must also be 
considered. Stainless steel, brass, and certain special aluminium alloys 
are suitable provided that care is taken not to have two dissimilar metals 
in contact. This can give rise to electrolytic corrosion of metals which 
are normally resistant to the effects of salt water. Particularly bad in this 
respect is the combination of brass and aluminium. Brass and stainless 
steel, however, can be used together without trouble. 

Control rods can easily be sealed by means of O-rings which give 
excellent freedom of movement, even when under pressure. A typical 
control-rod seal for a 'Perspex' case is shown in the diagram below. 



EXTERNAL CONTROL 




Va in STAINLESS-STEEL ROD 



U0375inM 



CAMERA LINKAGE 



LOCKING BUSH 



External controls should be large and easily gripped, even when the 
operator is wearing gloves. Also, owing to the fact that delicate move- 
ments are difficult underwater, strong end stops should be fitted to all 
controls to avoid damaging the camera. 




GN-12 



The normal direct-vision viewfinder is useless underwater, even in a 
transparent 'Perspex' case, because the eye cannot be placed close enough 
to the eyepiece. Instead, a large robust frame finder is recommended. 
The method (as illustrated on page 3) for determining the dimensions of this 
viewfinder allows for the reduction in the effective angle of view which 
occurs when the camera is immersed in water (see "Refractive index" 
on page 1). Since the eye cannot be placed close to the backsight, the 
centre of the foresight should be defined by a cross which can be lined up 
with the backsight. 

Reflex cameras 

Reflex focusing and viewing is a great advantage, especially for close-up 
work. For underwater use, a camera in which the focusing screen can be 
viewed direct is preferable to one employing a pentaprism. This is 
because it is difficult to see more than a small central area of the focusing 
screen when the eye is separated from the eye-piece of the pentaprism, 
as it will be in an underwater case. 

Square-format cameras present no problem in obtaining vertical pictures 
since the screen can be viewed direct through a large magnifier built in to the 
top of the case and they do not need to be turned on their sides. When 
a camera with a rectangular format is used, it is almost impossible to 
compose a vertical picture with the reflex camera on its side. In this case, a 
good compromise is to use a single 45° mirror over the ground glass and 
a magnifier behind the camera : this gives an inverted picture but at least 
the image does not rotate when the camera is rotated about its lens axis. 

The lens should have a fully automatic iris diaphragm and it is helpful 
to have a focusing screen which incorporates a split-image rangefinder 
rather than the more recent "microprism" focusing aid. With the split- 
image system, the direction of displacement of the moving image tells the 
operator which way to turn the focusing knob; the microprism system 
does not give this guide. 

Correcting lenses 

The definition at the edges of a picture taken through a plane porthole 
suffers from transverse chromatic aberration, particularly when wide- 
angle lenses are used. Two ways of avoiding this have been devised : 

1 The porthole is made in the form of a plano-concave lens and the 
camera lens is placed close to its centre of curvature. This eliminates 
the chromatic aberration and the dioptric power of the porthole is corrected 
by using a positive lens close to the front of the camera lens. 2 

2 A dome is used as the porthole, with the camera lens close to the centre 
of curvature. This is an inexpensive and versatile version of I and 
similarly to I a supplementary lens is required. Although curvature of 
field could be a problem with some lenses, with the use of wide angle 

GN-12 4 



150/jF 


INSIDE HOUSING 






1 




EXPOSED 


CENTRE OF 


> skn 


TO SEA 


CO-AXIAL PLUG 
TO FLASH CONTACTS 




lltf 








* 






TO BULB 


OUTER RING OF 
CO-AXIAL PLUG 


= 


r 

= EARTHED TO CASE (IF METAL) 


\ 



lenses on cine and still cameras (e.g. a 21 mm lens on a 35 mm camera) the 
increased depth of field, gives adequate edge definition. 
3 An afocal lens of two cemented elements is used as the porthole. The 
elements are chosen so that the combination has a dispersion equal and 
opposite to that encountered at a plane air-water interface. 3 

FLASH UNITS 

The usual method of arranging flash units for underwater cameras is 
to incorporate the battery-capacitor circuit and the camera connections 
inside the case, with only the two wires leading to the flashbulb being 
brought through the case. The bulb and flash-head can be exposed to 
the water without affecting efficiency. A suitable circuit is shown opposite. 
With a metal camera case only one wire needs to be taken through the 
case, the return path being through the metal. This one wire must, 
however, be insulated from the case and must be watertight. 

Electronic-flash units can also be used, sealed in a housing separate 
from the camera case. They can be triggered by means of wires passing 
down a sealed tube into the camera case, thyrister triggered or by a relay 
energized by the conventional bulb circuit shown above. In this case 
the wires and plugs can be exposed to the water. 

Plugs and sockets exposed to sea-water should be kept well greased 
to prevent the accumulation of an insulating layer of corrosion. 

Except in very clear water, the flash should be as far as practicable 
from the camera, at least 0.6 metre (2 feet), to minimize the flare caused 
by the flash lighting up the organic matter, particles and sediment close to 
the camera. 

TECHNIQUE 

The technique employed for underwater photography is completely 
different from that of normal photography. Both the diver and the 
camera will be virtually weightless underwater. While this is a very 
pleasant state for the diver, it does introduce problems of stability of 
the camera. A good strong frame finder is a great help in this respect; 



GN-12 



it can be braced firmly against the mask, greatly reducing the risk of 
camera shake. The majority of photographs will probably be taken on 
the bottom, and it is therefore an advantage to take down about 1.5 kilo- 
grammes (3 or 4 pounds) more weight than that required for neutral 
buoyancy. Also, as much of the weight as possible should be carried near 
the front of the diver's belt; this increases stability both when travelling 
horizontally and also when sitting on the bottom. However, exactly 
neutral buoyancy is essential when working over soft mud where there is 
no current to clear any sediment raised by touching the mud. 

Exposure 

Exposure underwater can be determined by means of a normal exposure 
meter in a special case, in a preserving jar, or inside the camera case if 
there is room and sufficient visibility, as with a 'Perspex' case. Incident- 
light measurements tend to be unreliable, and the normal reflected-light 
technique should be used. 

Some CdS cells give unreliable readings underwater because they have 
an unbalanced colour sensitivity with excessive red response. 

The following table can be used as a guide to exposing colour and 
monochrome film rated at 64 ASA/BS (arithmetical), or 19 DIN (logarith- 
mic). It applies for clear water (visibility greater than 10 metres or 
30 feet) in the middle of the day with the sun shining. In tropical 
waters, where subjects are generally much lighter, rather less exposure 
will be necessary. In poor visibility, or when filters are used, the com- 
pensation for depth will need to be greater and an exposure meter is 
essential. 

EXPOSURE TABLE FOR 64 ASA/BS FILM UNDER CLEAR-WATER CONDITIONS 
IN THE MIDDLE OF THE DAY WITH THE SUN SHINING— SHUTTER SPEED 1/60 

SECOND 



Depth 


Over 


Average and in 


Over Dark Rock 


Light Sand 


Open Water 


or Weed 


Down to 0.6 metre (2 feet) 


f/16 


f/H 


f/8 


1.5 metres (5 feet) 


f/H 


f/8 


f/5.6 


3 metres (10 feet) 


m 


f/5.6 


m 


6 metres (20 feet) 


f/5.6 


f/4 


f/2.8 


1 2 metres (40 feet) 


f/4 


f/2.8 


f/2 


24 metres (80 feet) 


f/2.8 


f/2 


f/1.4 



Flash 

When using monochrome film, the flash technique is fairly straight- 
forward, except that subjects are generally dark in colour and as there are 
no nearby reflecting surfaces guide numbers should be doubled to com- 
pensate. To avoid loss of contrast, never use the flash further from the 
subject than a quarter of the visibility distance. This is particularly 
important when the low visibility is due to plankton and similar large 
suspended particles. When working at distances greater than 3 metres 



GN-12 



(10 feet) in clear water, the absorption of the water adds to the loss of 
intensity as calculated from the inverse square law (on which guide 
numbers are based), and an additional exposure allowance will be needed. 
This will amount to approximately 1 stop for each 3 metres (10 feet) 
subject distance— 6 metres or 20 feet total light path— using flashbulbs 
or electronic flash and no camera filters. 

The same principles apply to colour film, with the additional problem 
of colour correction. Blue flashbulbs, or electronic flash, and the ap- 
propriate CC red filter— 12 CC units per metre (per 3.3 feet) of total light 
path — must be used for complete colour correction. 

For example, High-Speed 'Ektachrome' Film used with a AG IB* 
flashbulb has a metric guide number of 32 at 1/250 second. This "indoor" 
guide number must be divided by 2, giving an effective guide number 
of 16; with the subject at a distance of 1 metre (3.3 feet), an aperture 
of //16 is indicated. However, this aperture must be varied according 
to the filter to be used. In this case it is a CC20R— total light path 
of 2 metres (6.6 feet) multiplied by 12, as shown on page 2 — which 
necessitates an exposure increase of J stop (see Data Sheet CL-3), 
giving an aperture of about// 14. Once underwater it is not easy to work 
out calculations. All necessary calculations should therefore be done 
beforehand, and a note of the settings made on a plastic sheet. 

Cine 

Most of the foregoing principles apply equally to cinematography. 
Underwater floodlighting is possible but the equipment is bulky and of 
short range. 

When filming underwater, it is particularly important to keep the 
camera as steady as possible. For subjects requiring no movement of 
the camera, a tripod can be useful. The camera-tripod assembly should 
be negatively buoyant by a few pounds, as should the diver. Technique 
in this case is similar to that used on land. For tracking and mid-water 
shots the equipment and diver should be neutrally buoyant. It is essential 
to keep the case firmly braced against the mask and to make all move- 
ments as smoothly as possible. 

Another point is that shots should be longer than the equivalent surface 
shot. An audience takes a little time to get orientated to an underwater 
scene, and whereas a quick glimpse is adequate with familiar surface 
scenes, a similar technique in an underwater film results in a confused 
impression. 15 seconds should be regarded as a minimum except for 
very obvious and clear subjects. 

For shallow-water work in colour, CC filters can be used for accurate 
colour rendering. However, for non-technical films the cyan cast pro- 
duced by the water may be considered an advantage in creating the 
underwater effect. 

AUTOMATIC CAMERAS 

Fully automatic cine and still cameras, in which the exposure is set by 

* The only flashbulbs that do not float; this is a great advantage, making them very suitable if their 
output is sufficient. 

7 GN-12 



direct or servo control from a photo-electric cell, are very suitable for 
use underwater, bearing in mind the possible unreliable readings of 
some CdS cells, as mentioned under "Exposure" (page 5). With 
colour film, exposure correction for depth will be automatic if the same 
filter is used over the camera photocell as is used over the camera lens. 

The automatic control is especially valuable underwater because the 
camera is always ready for action. The use of automatic exposure- 
controlled cine cameras makes possible impressive tracking shots in 
locations such as caves and wrecks where the light intensity varies from 
place to place. 



REFERENCES 

1 J. B. Collins, Underwater Photography, Photogr. J., 90B, Tan./Feb. 
1950, pp. 24-31. 

2 A. Ivanoff and P. Cherney, Correcting Lenses for Underwater Use, 
J. Soc. Motion Pict. Telev. Engrs., 69, No. 4, April 1960, pp. 264-266. 

3 R. E. Craig and R. Priestley, Undersea Photography in Marine Research, 
Marine Research (Department of Agriculture and Fisheries for Scotland), 
No. 1, 1963. 



BIBLIOGRAPHY 

History of Underwater Photography, J. Photogr. Soc. Am., 17, Nov. 1951, 
pp. 689-691. 

H. Shenck and H. W. Kendall, Underwater Photography, Cornell Mari- 
time, Cambridge, Maryland, 1957. 

The Undersea Challenge {Proceedings of the 2nd World Congress of Under- 
water Activities), British Sub- Aqua Club, 1963. 

D. H. O. John, Photography on Expeditions, Focal Press, 1965. 

Underwater Photo-Optical Instrumentation Applications, Seminar, 1968, 
Society of Photo-Optical Instrumentation Engineers. 

C. E. Engel (editor), Photography for the Scientist, Chapter 9, Academic 
Press, 1968. 

Bibliography on Underwater Photography and Photogr ammetry, Eastman 
Kodak Pamphlet No. P-124. 



Kodak and Ektachrome are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

GN-12 

Y 1 226PDG N- 1 2/xWP I 0/2-72 



AUDIOVISUAL 



CONTENTS EDITION 

AV-I Still and Cine Projection Issue C 

AV-2 The Splicing of Cine Film Issue 8 

AV-3 Making Cine-Titles, Diagrams, and Animated Effects Issue B 

AV-4 Making Monochrome Slides for Projection Issue 8 

AV-5 Standard Sizes of Transparencies for Projection Issue 8 
AV-6 Planning, Preparation and Legibility in the Production Issue B 

of Transparencies for Projection 

AV-7 The Production of Colour Transparencies for Issue A 

Projection 



Associated Data Sheets in this or other volumes or sections 

I, RF-3 Optical Formulae and Depth-of-Field Table 
I, RF-4 Scales for Determining Copying Factors 
I, GN-I Copying Photographs and Other Illustrations 
i, GN-2 Copying Radiographs and Other Transparencies 
4, SE-4 'Kodak' Film Lengths 



Kodak is a trade mark KODAK LIMITED 

Printed in England 
YI327PDDB-20/xWPI0/S-73 




MAKING MONOCHROME SLIDES FOR PROJECTION 

Three sizes of slides are in common use in the United Kingdom : 5 X 5, 
7x7, 3jX3J. These were previously known as 2x2, 2| square, and 
3J square slides, with the measurements all in inches. Details of the 
currently accepted dimensions are given in the table below. 

Slides consist of a piece of film mounted into a holder, or suitably 
masked and bound between two cover glasses. 

DIMENSIONS OF SLIDES AND MASKS 



DESCRIP- 
TION 


OVERALL 


OVERALL 


NOMINAL 




LENGTH OF 


THICK- 


PICTURE 


MASK OPENING 


SIDES 


NESS* 


AREA 






mm 


mm 


mm 


mm 


5x5 


50.0 x 50.0 + 0.8 


1.2 to 3.2 


18 x 24 


15.5 x 22.5 ± 0.5 




- 0.0 




24 x 24 
24 x 36 
28 X 28 
40 x 40 


22.5 x 22.5 ± 0.5 
22.5 x 34.3 ± 0.5 
26.5 x 26.5 ± 0.2 
37.5 x 37.5 ± 0.7 


7x7 


69.9 x 69.9 ± 0.8 


3.5 (max.) 


55 x 55 


53.5 x 53.5 ± 0.7 


tH x H 


3± X 3± ± -& inch 


■&inch 


3x3 inch 


3x3 inch 



* Certain slide changers do not necessarily accept all slides lying within these thickness requirements, 
f This size is obsolescent; use the other two sizes in preference. 

On 5 X 5 slides the largest useful area is approximately 38 X 38 mm, but 
if this is restricted to an area of 34.3x34.3 mm (to match the longer 
dimensions of the majority of slides) then this will enable those slides 
requiring the full area of the (square) screen to be mixed with slides having 
a mask of the standard 22.5 x 34.3 mm. Slides with rectangular images 
may have the longer dimension either horizontal or vertical. 

MAKING SLIDES 

Monochrome continuous-tone images should show a long range of 
tones and maximum detail, and should have as high a degree of trans- 
parency as is compatible with retention of detail in the lightest areas. 
They should be reasonably bright but not too contrasty, judged under 
normal projection conditions. They can be printed in most cases, from 
existing negatives, but if negatives have to be made specially they should 
present the subject boldly, with the lighting arranged to bring out a full 
range of tones. 

The method used in making monochrome slides is analogous to that 
used in making prints on paper. A transparent material is used, in place 
of paper, on to which the negative is printed by contact or in the enlarger 
(which in this case may be used for projecting reduced images as well as 
enlarged ones). 

The preparation of the data or artwork for use in transparencies is 
extremely important, for the recommendations as to layout, lettering, etc., 
see Data Sheet AV-6. 



Issue B 



Kodak Data Sheet 
AV-4 



RECOMMENDED MATERIALS 

The films are listed approximately in the order of contrast that they 
give, but note that Fine Grain Positive Film and Kodalith Ortho Type 3 
are the only 35 mm films. The speeds of the films are similar to that of 
bromide paper. 

The developing times are for dish development at 20°C (68°F) with 
continuous agitation. 



FILM 


♦DEVELOPER 

AND 

DILUTION 


TIME IN 
MINUTES 


CONTRAST 
INDEX 


SAFE- 
LIGHT 
NO. 


SUITABLE FOR 


12556 


Kodalith Super 
Liquid 


2f-4 


Extremly 
High 


IA 


Linework 

~1 Linework and 
^extremely soft con- 


f257l 


D-163 (1+3) 


21 


3.3 


OB 


)( 


DPC (1+9) 


24-3 


3.2-3.3 


OB 


ftinuous-tone 
J negatives 












f2698 


D-163 (1 + 1) 


11-3 


2.1-2.4 


OB 


-, Linework and very 
Isoft continuous- 


■ > 


DPC (1+4) 


4-3 


2.3 


OB 


J tone negatives 


„ 


D-163 (1+3) 


24-3 


1.8-2.1 


OB 


(jContinuous-tone 




DPC (1+9) 


21-3 


2.0 


OB 


>. 


+■4181 


DPC (1+9) 


21-3 


1.4 


OB 


• > >> 




D-163 (1+3) 


21-3 


1.3-1.4 


OB 


.. .. 


ifF.G. Pos. 


D-163 (l + l) 


14-3 


1.4-1.5 


OB 


.. 


tt 


D-163 (1+3) 


21 


1.4 


OB 


,< 


M 


DPC (1+4) 


14-3 


1.3 


OB 


.. ,, 


■• 


DPC (1+9) 


21-3 


1.3 


OB 


" 



* Developers 

'Kodak' D-163 Developer (liquid or powder). 

'Kodak' DPC Developer (liquid), 
f Sheet Films 

'Kodalith' Contact Film 2571 ('Estar' base). 

'Kodaline' Standard Film 2698 ('Estar* base)— see Data Sheet FM-31. 

'Kodak' Process Film 4181 ('Estar' thick base)— see Data Sheet FM-33. 

I 35mm Film 

'Kodalith' Ortho Film 2556, Type 3 ('Estar* Base) 

'Kodak' Fine Grain Positive Film — see Data Sheet FM-56. 
§ A wide range of contrast is available to suit most continuous-tone negatives by the optimum film/ 

developer combination. It should be noted that transparencies have a greater tone range than 

paper prints and therefore there cannot be any precise correlation between the films in the table 

and the grades of bromide paper. 

LOCATION OF MASK OPENING 

Whether the printing is done by contact or projection, keep the mask 
opening within a centrally located area. Keep the distance from the edge 
of the slide to the adjacent edge of the mask opening equal on opposite 
sides of the slide within 0.5 mm, both for horizontal and vertical centring. 

PRINTING BY CONTACT 

When the negative to be used provides an image of the correct size for 
the slide, contact printing is the simplest procedure, for which a printing 
frame can be used. It may be more convenient to use the projected 
beam of light from an enlarger to make the exposure rather than a bare 
lamp. The negative should be masked to an area just larger than that 
to be recorded in the final slide; this will prevent extraneous light from 
fogging the film. The mask should not be placed between the negative 
and the sensitized material, however, or definition will be impaired. If 



AV-4 



placed on the back of the negative, the fuzzy edge can be masked off in 
the final slide. 

As the finished slide is to be magnified many times on projection, it is 
important that extreme care should be taken to prevent dust settling be- 
tween the negative and the sensitized material during exposure; good 
contact is also most important. To check this, a test negative can be 
prepared by scratching the emulsion side of a fogged and developed 
sheet or piece of film. This will give a pattern of fine lines with extremely 
sharp edges. Transparencies made from such a negative can be examined 
with a magnifier to make certain that all the lines are sharp. If any are 
blurred, contact cannot have been sufficiently good and the printing 
frame should be modified to give more even pressure. 

In place of a printing frame, a printer can be used, or a printing box 
can be made up quite easily. A suitable box has sides of about 18 inches 
(45 cm), contains a 25-watt lamp and has arrangements for ventilation. 
It has a panel of flashed opal glass let into the top. Lay the negative on 
this, emulsion side up, and press the film into contact by means of a block 
of wood faced with a pad of felt. Maintain firm contact during exposure. 
A red pilot-lamp inside may make positioning of the negative and sen- 
sitized material easier, but care must be taken to see that it is not of a type 
which will fog the material. (However, the pilot-lamp can be dispensed 
with if suitable guides are attached to the top of the box to locate the film 
and negative.) 

PRINTING BY PROJECTION 
Requirements in the enlarger 

The enlarger should permit reduction as well as enlargement. The 
illumination should be even at all ratios and cover the largest negative 
likely to be used. The baseboard should be capable of retaining pieces of 
film (e.g., using a cork mat or a masking frame). Use a matt black base 
for the film. The negative carrier should be capable of being masked 
down to the required area to reduce unwanted light. 

Procedure 

Focus the image on an undeveloped piece of film with the emulsion 
facing the lens, or on a piece of thick white paper. Use a mask of the 
appropriate size to determine the exact position of the required area. 
It is advisable to use another mask with a slightly larger opening over the 
film during exposure to prevent fogging by scattered light. Focus 
accurately, as the degree of enlargement on projection is many times the 
degree of enlargement used in making prints. 

In some cases it may be difficult to arrange an enlarger to produce a 
sufficiently small image when making 5x5 slides. If so, the negative 
may be set up in front of an illuminated panel and photographed with a 
35 mm camera, using Fine-Grain Positive Film, afterwards binding the 
piece of film between glasses. It is, of course, necessary to obtain really 
even illumination over the negative, to see that the camera-back is parallel 
to the negative, and to ensure that focusing is critical. Further recom- 
mendations are given in Data Sheets GN-2 and DC-1. 

3 AV-4 



REDUCING 3^x3i SLIDES TO SMALLER SIZES 

It may be desired to re-make existing 3J x 3 \ slides (82 x 82 mm) 
to form a new library of 5 x 5 slides. If the original negative is not avail- 
able, make a copy negative either by unbinding the slide and contact 
printing it, or by copying the slide, as it stands, with a camera. A single- 
lens reflex camera with a bellows attachment and a rack for focusing the 
whole assembly would be very suitable. Other cameras require supple- 
mentary lenses over the camera lenses to enable them to be focused at 
close distances. The slide to be copied should be placed on an illuminated 
viewer with extraneous light masked off. It may be convenient to copy 
a number of slides at the same time. If a reversal process is used, the 
separate images may be cut after processing and mounted in the normal 
way, or where an intermediate negative is used the whole group may be 
printed in one operation, after which the positive is cut and mounted. 
Those who possess a titler may find that it can be adapted for copying 
3| x 3\ slides, alternatively a diagram of a suitable copying arrangement 
can be found in Data Sheet AV-7. 

Using reversal film 

Kodak 'Panatomic-X' Film is excellent for producing direct positives 
by reversal processing. See Data Sheet PR-4. 

Colour films, although intended for colour reproduction, will, never- 
theless, give good-quality slides of monochrome material, and many 
slidemakers find this the simplest method where a reversal process is 
acceptable. It is particularly suitable when monochrome slides have to 
be mixed with colour slides and it has the advantage of being a standardized 
process. High-Speed 'Ektachrome' Film should be used for continuous 
tone slides (see Data Sheet FM-1B); daylight type for electronic flash, 
and type B for tungsten illumination. For line work 'Kodachrome' films 
(see Data Sheets FM-2A and FM-2B) are recommended because of the 
higher contrast and "cleaner" outlines, however, any of the 'Kodak' 
colour reversal films may be used. Colour film used for line work has 
the advantage that a colour may easily be added to the slide by using the 
appropriate filter — see Data Sheet FT-i. Tests should be made to 
determine whether any filtration is necessary to obtain a neutral rendering 
or the desired colour, as the case may be. See also Data Sheet AV-3. 

NEGATIVE SLIDES FROM LINE DIAGRAMS 

If viewing is to take place in a lighted room, then many line originals, 
such as drawings, maps, letters and printed documents, make more 
suitable slides when reproduced as negatives rather than positives — 
i.e., on the screen the background is dark and the lines appear white. 
This effect can easily be achieved by copying the material with a camera 
and using the negative direct. Failing this, Indian ink, typed or printed 
originals of suitable size on white paper can be printed direct, by contact, 
on to film. Use a high-contrast material. 

Using reversal film 

Colour reversal film may also be used to produce negative slides of 
fine subjects with the advantage that a coloured background can be 
introduced. 

AV-4 4 



PROCESSING THE FILM 

After the film has been exposed as described above, it must be processed. 
See table on page 2 and its footnotes for the recommended developers, 
dilutions, times and safelight. These are the recommended develop- 
ment times; the contrast of the slide can be varied to some extent by 
altering the exposure time and the degree of development outside those 
given in the table but this may adversely alter the characteristics of the 
film. Prolonged development should be avoided as it causes objectionable 
fogging of the highlights. 

Exposures on 35 mm film can be developed in a daylight tank of the 
type used for negative materials, provided that the same development 
is suitable for the whole film. If it is not suitable, the film must be 
exposed in separate short sections with only one exposure on each. These 
should be about 3 inches (75 mm) long and can be developed separately 
in a dish, using the ends of the film for handling. A rough guide to the 
progress of the image can be had by watching the highlights developing. 
When detail is seen in the lightest significant highlight then the image 
should be sufficiently developed. 

After development, rinse the film in running water and fix in a solution 
made up from one of the following: 'Kodafix' Solution, Kodak 'Unifix' 
Powder, 'Kodak' Rapid Fixer, or Kodak formula F-5. Wash for 30 
minutes in running water, at 18-24°C (64-75°F) or bathe in a solution of 
'Kodak' Hypo Clearing Agent and give a short wash in running water. 
Finally rinse in a bath of Kodak 'Photo-Flo' solution, and dry in a dust- 
free place. 

JUDGING DENSITY AND CONTRAST 

It is difficult to judge a film image for correct density and contrast 
until it is dried and projected. After some experience it is possible to 
make an assessment while the film is wet, but even so, it is always desirable 
to dry and project the slide before finally passing it as satisfactory. If 
time is short, the test film can be washed for a few minutes and then rinsed 
in a solution of 70 per cent industrial spirit with water, after which it 
will dry very quickly and can be projected without binding. It should 
be noted that it is not satisfactory to view it against an illuminator with 
opal or ground-glass diffusion. A dry transparency always appears lower 
in contrast when viewed in this way than when projected. 

In slides of line diagrams or lettering the lightest tones should appear 
completely transparent, while the blacks should be as dense as the material 
will allow. The edges of the lines should be sharp and there should be no 
trace of "spreading" of the blacks. Spreading of the blacks is a sure sign 
of over-exposure of the film, provided the negative is a good one. If 
adequate contrast cannot be obtained, print the film rather dark and then 
reduce with Farmers' reducer (see Data Sheet FY-5) until the light areas 
are just completely clear. 

FINISHING SLIDES 

When the film is dry, examine it for quality. Points to look for are: 
sharpness, framing, density, contrast, image tone and freedom from 
blemishes. 

If any spots or markings are present, they can be carefully removed 



AV-4 



by means of water colours on a fine brush, using a magnifier. The brush 
should be as dry as possible and the colour built up by several applica- 
tions, rather than by one blob. 

If slides contain excessive moisture, this may condense on the inside 
of the cover glasses during projection and may even swell the emulsion 
so that it melts. It is therefore wise when binding slides during damp 
weather to dry out the transparencies and masks to a reasonable degree. 
Place them in an airtight container with a desiccating agent, such as silica 
gel, for 15 to 20 minutes or keep them in an airing cupboard for 24 hours. 
The slides should be subsequently stored in a dry atmosphere and should 
always be warmed slightly before projection. 

Binding the slide 

Clean the cover glasses carefully. Mask the film with a pre-cut mask 
(either single or double) and make a sandwich with the two glasses. 
Use black gummed paper tape for binding all round the edges except 
where a duplex tape is used for a position indicator on one edge (see 
below). 

Transparencies in cardboard mounts are not satisfactory for binding 
between cover glasses, as the slide is then too thick for use in some 
projectors. 

Great care must be taken to clean the transparency and the glasses 
so that no small particles of dust are trapped inside. This can con- 
veniently be done by holding them upright and tapping their edges 
against a clean hard surface. If necessary a clean, soft, camel-hair brush 
(such as a lens-cleaning brush) can be used in addition. 

Title strip 

If a title strip is required, this should be a white strip in the upper- 
margin of the slide as the slide is correctly oriented for viewing in the 
hand. The text should be right way up in this position. 

Position indicator 

An indication should be given to the projectionist and the sorter of the 
correct orientation of the slide for projection. Two methods are in 
current use. One is to use a spot near the bottom left-hand corner when 
the slide is viewed in the hand; the other is to use a white/black duplex 
binding strip over the bottom edge, with the white portion on the front 
face and over the edge when the slide is viewed in the hand. This white 
strip gives a quick, clear indication that slides in a slide box are correctly 
oriented for projection. 

'EKTAGRAPHIC* WRITE-ON SLIDE 

These are pieces of film specially treated to give a "tooth" to one 
surface and allow it to accept all the normal writing materials. They 
are mounted in 5 x 5 card mounts. 



Product names quoted thus — 'Kodak' — are trade marks. 



Kodak Data Sheet KODAK LIMITED LONDON 



PDAV-4/xWPI 1/8-71 



STANDARD SIZES OF TRANSPARENCIES 
FOR PROJECTION 



Transparencies are normally prepared in one of three forms. The form 
chosen will depend on whether the transparencies are for projection by a 
slide, film strip or overhead projector. 

DIMENSIONS OF SLIDES AND MASKS 

Three sizes of slides are in common use in the United Kingdom: 
2x2 inches, 2f inches square, and 3j inches square. These are now 
designated 5x5, 7x7, and 3Jx3J in British Standard 1915: 1968. 

Details of the currently accepted dimensions are given in the table 
below. 



DESCRIP- 
TION 


OVERALL 

LENGTH OF 

SIDES 


OVERALL 
THICK- 
NESS* 


NOMINAL 

PICTURE 

AREA 


SLIDE-MASK 
APERTURE 


5x5 


mm 
50.0x50.0+°q 


mm 
1.2 to 3.2 


mm 
18x24 
24x24 
24x36 
28x28 
40x40 


mm 
I5.5x22.5±0.5 
22.5x22.5±0.5 
22.5x34.3±0.5 
26.5x34.3±0.2 
37.5x37.5±0.7 


7x7 


69.9x69.9±0.8 


3.5 (max.) 


55x55 


53.5x53.5±0.7 


t3±x3± 


H><H±-h inch 


^ inch 


3x3 inch 


3x3 inch 



♦Certain slide changers do not necessarily accept all slides lying within these thickness 

requirements. 
fThis size is obsolescent; use the other two sizes in preference. 

Maximum useful area 

On 5x5 (2x2 inch) slides the largest useful area is approximately 
38 x 38 mm, preferably this should be restricted to a 34.3 x 34.3 mm (to 
match the longer dimensions of the majority of slides). This will then 
enable those slides requiring the full area of the (square) screen to be 
mixed with slides having a mask of the standard 22.5 X 34.3 mm; main- 
taining one dimension constant in this way gives a better standard of 
presentation. Slides with rectangular images may have the longer 
dimension either horizontal or vertical. 

Position indicator 

To facilitate correct orientation during projection, mark the trans- 
parency frame or mask. Two methods are in current use. One is to use 
a spot near the bottom left-hand corner when the slide is correctly 
orientated whilst viewed in the hand. The transparency must be placed 
in the projector so that the spot is at the top right-hand corner of the slide 
holder, visible to the projectionist whilst looking towards the screen. The 
alternative method is the use of a white-and-black duplex binding strip 
over the bottom edge, with the white portion on the front face and over the 
edge when the slide is correctly orientated whilst viewed in the hand. 



Issue A 



Kodak Data Sheet 
AV-5 



Title strip 

If a title strip is required, this should be a white strip in the upper- 
margin of the slide when the slide is correctly orientated for viewing in the 
hand. The text or title should be right way up with the slide in this 
position. 



^r 



Typical transparency 

Slides consist of a piece of film mounted into a holder, (transparency 
mount) or suitably masked and bound between two cover glasses. 
Typical arrangements can be seen from the diagram below. 



FILM 

(EMULSION 

SIDE) 



SLIDE COVER 
WITH GLASS 




FILM 

(EMULSION 

SIDE) 



CARD 
READY -MOUNTS 



Figure I 

FILM STRIPS 

Where a series of still pictures is required to be shown in a regular or 
fixed programme, film strips may be used. 



NOMINAL FRAME SIZE 


PROJECTOR MASK APERTURE 


mm 
18x24 
24x24 
24x36 


mm 
I7.5±0.3x23±0.3 
23 ±0.3x23±0.3 
23 ±0.3x34±0.3 



The above table gives the mask sizes for film strip projectors (from 
BS 1915 : 1968); the table on page 1 refers only to masks bound into indivi- 
dual slides. 



AV-5 



Maximum useful area 

For film strips, the largest useful area is approximately 17.5 x 23 mm, the 
mask being incorporated in the projector or in its film strip adaptor. 

Typical film strip 

A film strip consists of a strip of 35 mm film carrying photographic 
images suitable for still, but not cinematographic projection. As shown 
in the diagram below, where both vertical and horizontal formats are to be 
included they should be arranged so that only a 90° rotation is needed 
between adjacent frames. For better presentation, however, film strips 
should be of one format and orientation only. 



LEADER 
150mm min 



TRAILER 
150mmmin 




SCREEN 



Note: Not more than 90° rotation between (a) and (b) 

Figure 2 i 

TRANSPARENCIES FOR OVERHEAD PROJECTION 

The standard size for these is 10 x 10 inches (254x254 mm). Trans- 
parencies for overhead projection may be made either as a roll of trans- 
parent material 254 mm (10 inches) wide or on 254 (10 inch) square 
material mounted into a suitable support. The supports usually are made 
to fit either a pin or bar registration system to allow progressive build up of 
visual data, during projection, to be properly registered on the screen. 
NOTE: Certain projectors, of non U.K. origin, may not, however conform 
to the British Standards indicated in this Data Sheet. 



BIBLIOGRAPHY 



British Standard 1915: 1968. 
British Standard 1917: 1968. 



AV-5 



KODAK 

is a trade mark 



Kodak Data Sheet KODAK LIMITED LONDON 

AV-5 

PDA V-5/xWPI 1/10-70 



STANDARD SIZES OF TRANSPARENCIES 
FOR PROJECTION 



Transparencies are normally prepared in one of three forms. The form 
chosen will depend on whether the transparencies are for projection by a 
slide, film strip or overhead projector. 



DIMENSIONS OF SLIDES AND MASKS 

Four sizes of slide mounts are in use in the United Kingdom: \\, 2, 
and 31 inches square. They are designated 3x3, 5x5, 7x7 and 
\. 3x3 mounts take size 110 slides; 5x5 mounts take all sizes 
of 35 mm slides, 126 slides, and 127 "superslides" ; and 7x7 mounts 
take 2\ inch square slides. 

Details of the currently accepted dimensions are given in the table 
below. 



3Jx3 



DESCRIP- 
TION 


OVERALL 

SIZE OF 

SIDES 


OVERALL 
THICK- 
NESS* 


NOMINAL 

PICTURE 

AREA 


SLIDE-MASK 
APERTURE 


3x3 


mm 
30.3x30.3±0.2 


mm 
1.3 (max.) 


mm 
13x17 


mm 
I2.00xl5.80±0.05 


5x5 


50.0x50.0±0.8 


1.2 to 3.2 


18x24 
24x24 
24x36 
28x28 
40x40 


I5.5x22.5±0.5 
22.5x22.5±0.5 
22.5x34.3 ±0.5 
26.5x26.5±0.2 
37.5x37.5±0.7 


7x7 


69.9x69.9±0.8 


3.5 (max.) 


55x55 


53.5x53.5±0.7 


t3±x3± 


3ix3i±^ inch 


A inch 


3x3 inch 


3x3 inch 



♦Certain slide changers do not necessarily accept all slides lying within these thickness 

requirements. 
fThis size is obsolescent; use the other sizes in preference. 

Maximum useful area 

On 5x5 (2x2 inch) slides the largest useful area is approximately 
38 X 38 mm, preferably this should be restricted to a 34.3 X 34.3 mm (to 
match the longer dimensions of the majority of slides). This will then 
enable those slides requiring the full area of the (square) screen to be 
mixed with slides having a mask of the standard 22.5 X 34.3 mm; main- 
taining one dimension constant in this way gives a better standard of 
presentation. Slides with rectangular images may have the longer 
dimension either horizontal or vertical. 

Position indicator 

To facilitate correct orientation during projection, mark the trans- 
parency frame or mask. Two methods are in current use. One is to use 
a spot near the bottom left-hand corner when the slide is correctly 
orientated whilst viewed in the hand. The transparency must be placed 
in the projector so that the spot is at the top right-hand corner of the slide 
holder, visible to the projectionist whilst looking towards the screen. The 



Issue B 



Kodak Data Sheet 
AV-5 



alternative method is the use of a white-and-black binding strip over 
the bottom edge, with the white portion on the front face and over the 
edge when the slide is correctly orientated whilst viewed in the hand. 

Title strip 

If a title strip is required, this may conveniently be a white strip in the 
upper-margin of the slide when the slide is correctly orientated for viewing 
in the hand. The text or title should be right way up with the slide in 
this position. 

Typical transparency 

Slides consist of a piece of film mounted into a holder, (transparency 
mount) or suitably masked and bound between two cover glasses. 
Typical arrangements can be seen from the diagram below. 

SLIDE COVER 
WITH GLASS 




FILM 

(EMULSION 

SIDE) 



FILM 

(EMULSION 

SIDE) 



CARD 
READY -MOUNTS 



Figure I 

FILM STRIPS 

Where a series of still pictures is required to be shown in a regular or 
fixed programme, film strips may be used. 



NOMINAL FRAME SIZE 


PROJECTOR MASK APERTURE 


mm 
18x24 
24x24 
24x36 


mm 
I7.5±0.3x23±0.3 
23 ±0.3x23±0.3 
23 ±0.3x34±0.3 



AV-5 



The table opposite gives the mask sizes for film strip projectors (from 
BS 1915: 1968); the table on page 1 refers only to masks bound into indivi- 
dual slides. For film strips, the largest useful area is that of the mask 
incorporated in the projector or in its film strip adapter. 

Typical film strip 

A film strip consists of a strip of 35 mm film carrying photographic 
images suitable for still, but not cinematographic projection. As shown 
in the diagram below, where both vertical and horizontal formats are to be 
included they should be arranged so that only a 90° rotation is needed 
between adjacent frames. For better presentation, however, film strips 
should be of one format and orientation only. 



LEADER 
150mm min 



PROJECTOR 



TRAILER 
150mmmin 



fe c '/^^cc^c cmrccccccc L-ircrcrrrrrrrrr rrrrrrrr r^ri^ 



title 



end 



- ^aWccpcrcccLccccircirirrririrrirrcirr ccrcrrrrrrrrrnfc 



(a) (b) 




SCREEN 



Note: Not more than 90° rotation between (a) and (b) 
Figure 2 

TRANSPARENCIES FOR OVERHEAD PROJECTION 

The standard British size for these is 10x10 inches (254x254 mm) 
with a useful area of 8x8 inches (203x203 mm). Transparencies for 
overhead projection may be made either as a roll of transparent material 
254 mm (10 inches) wide or on 254 mm (10 inch) square material mounted 
into a suitable support. The supports usually are made to fit either a 
pin or bar registration system to allow progressive build up of visual 
data, during projection, to be properly registered on the screen. 

NOTE : Certain projectors, of non UK origin, may not, however conform 
to the British Standards indicated in this Data Sheet. 



BIBLIOGRAPHY 



British Standard 1915: 1968. 
British Standard 1917: 1968. 
ISO R-1755 October 1971. 



AV-5 



AV-S 



KODAK 

is a trade mark 



Kodak Data Sheet KODAK LIMITED 



Printed in England 

Y 1 284PDAV-5/xWP 1 0/ 1 0-72 




THE PRODUCTION OF 

COLOUR TRANSPARENCIES FOR PROJECTION 



The projection of data in the form of black-and-white diagrams or 
graphs in the middle of a series of colour slides, can be very distracting. 
It is recommended therefore, that the presentation and preparation be 
carried out taking into account the points given in detail on Data Sheet 
AV-6. 

Data Sheet AV-6 contains information on the planning, preparation and 
legibility of transparencies, to achieve the smooth, unobtrusive but 
effective dissemination of information. When the proper planning of 
the whole presentation and of each transparency has been completed 
and where necessary the artwork produced, a start may be made on the 
actual production of the transparencies. 

Two main groups of techniques are usual, dependent mainly on the 
method of preparing the original artwork. These groups are firstly, for 
artwork prepared in colour and secondly for artwork prepared in black- 
and-white. The techniques discussed are not the only ones, but are 
those known to be successful and relatively simple. 

TRANSPARENCIES FROM ARTWORK PREPARED IN COLOUR 

These should be treated as normal copy operations (as given fully in 
Data Sheet GN-1, lighting for copying colour is given in more detail 
on page 7). Ensure, however, that even lighting of the right type is 
used. This is discussed more fully under the section of this Data Sheet 
entitled Lighting. Exposure, too, is more critical with colour work; 
the exposure can best be assessed by using a meter. 

TRANSPARENCIES FROM ART WORK PREPARED IN BLACK-AND-WHITE ONLY 

Often facilities for the proper preparation of artwork originals in 
colour are not readily available. The higher cost of such work may be 
considered unjustifiable in some cases, or perhaps the time available 
does not permit obtaining coloured artwork. In this case the use of 
normal, high-contrast, bold, black-on-white originals, may be preferred, 
with the colour being added at the photographic stage. 

The Use of Colour Dyes and Toning 

If adequate separation between the lines or areas requiring colour differen- 
tiation is provided, it is possible with practice, to dye the appropriate 
section of the transparencies with various colours. Colour retouching 
dyes or photo tints used in this way should be diluted or the general effect 
would be too dark. For this reason, also, it is recommended that all lines 
and characters used should be even bolder than normal to ensure adequate 
legibility. If only one colour is required, the transparency may be dyed 
or toned with an overall colour. Two or more colours may be obtained 
by mounting a second overall dyed or toned slide (with emulsion side to 

Issue A Kodak Data Sheet 

AV-7 



emulsion side) together with the first. The information on the second slide 
should be laterally reversed in copying. This technique can also be used 
to add titles to pictorial transparencies. A range of suitable colours can 
be obtained using 'TetanaP Multitoner processing. Two slides of 
different colours combined in this way will also produce a third colour; 
by the combining of yellow and blue, for instance, green is produced. 

Filters as a means of Adding Colour 

A better balance between colour and line slides can also be obtained by 
the expedient of binding into the line slide, or even placing over the projec- 
tor lens, a suitable filter of the Kodak Colour Compensating range. This 
system is most useful when slides from a variety of sources have to be 
projected in a single programme and time does not permit remaking. The 
density of the filter required will vary according to the density and type 
of material recorded, but will usually be in the 025 to 20 range — filter 
factors, which in this case are only used to give an idea of the light loss 
on projection, are given in full in Data Sheet CL-3. In general, this 
technique is only useful for transparencies of low initial density. 

Photographic Techniques 

Line material artwork, prepared in black-and-white, can be made into 
colour transparencies with excellent quality and legibility in a variety of 
background colours, by the method outlined below. 

The original, high contrast, black-and-white artwork or printed 
information is copied on to 'Kodalith' film, which after development in 
'Kodalith' developer gives a clear, white-on-black negative of high 
contrast. 

After spotting out any dust marks or pinholes, place the negative on 
a 'Kodak' Transparency Viewer. At this stage, the 'Kodalith' negative 
can be of any convenient size, but to avoid a lot of tedious and time- 
consuming realignment of the 35 mm camera normally used in the next 
stage, a convenient standard size should be adopted. The 'Kodalith' 
negative size adopted is usually smaller than the screen of the 'Kodak' 
Transparency Viewer, and to avoid problems from stray light (flare) an 
opaque mask, cut to take the negatives, should be used. 

A 35 mm camera, carefully aligned with the 'Kodalith' negative, is then 
used to produce the final transparencies on, for example, 'Ektachrome-X' 
colour reversal film. Two exposures are made for each transparency, 
and the camera must therefore be capable of deliberate double exposure, 
or, alternatively, the film can be rewound between first and second 
exposures. 

The first exposure is with a camera setting of approximately | second 
at// 11, and is to record the lettering — no filter is used on this exposure. 
This first exposure, recording the letters or characters;, is not too critical, 
but is subject to the usual considerations of lens and original negative 
quality. Over-exposure has little effect, providing contrast and back- 
ground density in the 'Kodalith' negative are adequate. Under-exposure 
will, however, give veiled lettering and thus lower contrast in the final 
transparency. 

AV-7 •> 



A second exposure, of approximately \ second at/711, is then made 
through a suitable 'Wratten' filter, the 'Kodalith' negative having been 
removed prior to this, so that the screen of the 'Kodak' Transparency 
Viewer is presented direct to the camera during this exposure. This 
second exposure, through the filter, is not critical and gives the background 
colour. As no filter has perfect transmission, however, but allows small 
amounts of other wavelengths to pass; and as the layers in the colour 
emulsions are affected slightly by more than one colour, prolonged over- 
exposure leads to a lighter more diluted colour. Under-exposure will 
give a darker less saturated background colour. 



CAMERA 



VIEWER OR 
ILLUMINATOR 




Figure I. Diagram of the suggested arrangements for the production of colour slides 
from black and white originals. 



AV-7 



SUMMARY OF TRANSPARENCY EXPOSURES 



ACTION 


COMMENT 


FILTER 


EXPOSURE 


First Exposure . 
Second Exposure 


Kodalith negative on 
the viewer 
Viewer only 


None 

As in nexttabte 


5 second at f/l 1 
Jj second at f/l 1 



The colour of background achieved, is dependent on the filter type 
chosen. Although almost any filter can be used, some typical examples 
are given in the table below. 



KODAK 'WRATTEN' FILTER 


COLOUR OF TRANSPARENCY 
BACKGROUND* 


22 Deep Orange 


Orange 


29 Deep Red 


Red 


33 Medium Magenta 


Magenta 


45 Blue Green 


Blue/Green 


47B Deep Blue 


Blue 


61 Deep Green 


Green 



* The actual colour of the background will vary slightly according to the type of viewer used as a light- 
source; the 'Kodak' Transparency Viewer is fitted with I5W 'Phillips* Colour 46 tubes and the 'Kodak' 
Coldlight Viewer is fitted with I5W 'Atlas' Tropical Daylight tubes. Providing consistent use is made 
of one or the other, the difference in colour temperature in this application is not important. 

Superimposition of data on to photographs or transparencies 

Follow the same double exposure procedure as above; but instead of 
making the second exposure of the viewer, use a photograph or transparency 
in place of the viewer. This, taken without any filter, other than may be 
required for colour correction, will then give white letters superimposed 
on to the transparency copied. The first exposure will be the same 
(approximately J second at//ll), but the second exposure will depend 
now on the lighting and density of the photograph or transparency 
and the number of filters needed to obtain correct rendering. An 
exposure meter should be used to assess the actual exposure to be given. 

Radiographs 

Where radiographs and colour slides are to be shown together, it 
may be convenient to make slides of the radiographs using a reversal 
colour film. 

A 35 mm single-lens-reflex camera, fitted with close-up lenses or 
extension tubes and slow shutter speeds, can be used with High Speed 
'Ektachrome' Film (Daylight). This can be employed in conjunction 
with an Tndustrex' X-ray Illuminator, Model 2, which is a convenient 



AV-7 



apparatus for providing even illumination and a means of masking the 
radiograph. 

Transparencies made using this technique have a cyan cast, but this 
can be adjusted to the blue cast typical of radiographs by using a 'Kodak' 
Colour Compensating Filter CC30M over the lens. Exposures should be 
determined experimentally, but | second at// 11, when using the system 
described, is a good basis for a radiograph of average density. 

Judging Density and Contrast in the final transparency 

When the film is dry, after processing, examine it for quality. Points 
to look for are: sharpness, framing density, contrast, image tone, and 
freedom from blemishes. 

It is difficult to judge a colour film image for correct density, colour 
and contrast until it is dried and projected. After some experience, it 
is possible to make an assessment while the film is wet, but even so, it 
is always desirable to dry and project the slide before finally passing it 
as satisfactory. It should be noted that it is not satisfactory to view it 
against an illuminator with opal or ground-glass diffusion. A dry 
transparency always appears lower in contrast when viewed in this way 
than when projected. 

Finishing Slides 

If slides contain excessive moisture this may condense on the inside 
of the cover glasses during projection, and may even swell the emulsion 
so that it melts. It is therefore wise, when binding slides during damp 
weather, to dry out the transparencies and masks to a reasonable degree. 
Place them in an airtight container with a desiccating agent, such as 
silica gel, for 15 to 20 minutes, or keep them in an airing cupboard for 
24 hours. The slides should be subsequently stored in a dry atmosphere 
and should always be warmed slightly before projection. 

Film strips do not require mounting but should be stored in air-tight 
tins to avoid damage. 

Binding Transparencies: Clean the cover glasses carefully. Mask the 
film with a precut mask (either single or double) and place these between 
the two glasses. Use black gummed paper tape for binding all round the 
edges except where a duplex tape is used for a position indicator on one 
edge (see below). Transparencies in cardboard mounts are not satis- 
factory for binding between cover glasses, as the slide is then too thick 
for use in some projectors. There are also numerous purpose-made 
slide mounts in plastic or metal with built-in masks and glasses and these 
are recommended for normal use. 

Great care must be taken to clean the transparency and the glasses 
so that no small particles of dust are trapped inside. This can con- 
veniently be done by holding them upright and tapping their edges 
against a clean hard surface. If necessary, a clean, soft, camel-hair 
brush (such as a lens-cleaning brush), Selvyte cloth or 'Perostatic' anti- 
static brush can be used. 

c AV-7 



Title Strip : If a title strip is required, it should be a white strip in the 
upper-margin of the slide when the slide is correctly orientated for viewing 
when held in the hand. The test should be right way up in this position. 
With film strips, the markings are usually photographed on to the film, 
as shown in the diagram at the beginning of Data Sheet AV-5. 

Position indicator for proper projection : An indication should be given to 
the projectionist, and to the sorter, of the correct orientation of the slide 
for projection. Two methods are in current use. The preferred standard 
is to mark a spot on the mount, near the bottom left-hand corner when 
the slide is viewed in the hand; another, is to use a white/black duplex 
binding strip over the bottom edge, with the white portion on the front 
face and over the edge when the slide is viewed in the hand. This 
white strip gives a quick, clear indication that slides in a slide box are 
correctly orientated for projection. The two systems can be and often 
are combined and used together. Where a film strip is being used, the 
script which normally accompanies it should state whether the next 
frame is vertical or horizontal. 

' Ektagraphic' Write-On Slide : These are pieces of film specially treated 
to give a "tooth", to one surface, which allows it to accept all the normal 
writing materials. Coloured felt-tip pens or inks or ball-point pens 
may be used, but care must be taken especially in damp conditions, to 
avoid smearing of the writing. They are mounted in 5 x 5 (2 in. x 2 in.) 
card mounts. 

Equipment 

When making transparencies for projection, it is important to remember 
that, any misalignment of the vertical or horizontals can be compared 
directly with the edge of the transparency mount, or with the edge of the 
screen. Extreme care should therefore be taken to align correctly, as 
very slight deviations can be easily seen. Non single-lens reflex cameras 
may be used, but, to avoid any parallax error, alignment should be under- 
taken by using a focusing screen at the film plane. Even with single-lens 
reflex 35 mm cameras, accurate alignment can be difficult owing to the 
small size of the image, and occasionally the degradation of image quality, 
due to scatter at, or curvature of, the ground glass or opal viewing screen. 

It is recommended, therefore, that a standard piece of equipment be 
made. This should have a means of attaching the camera, in a fixed 
relationship, to a copy holder or base-board marked with rectangles 
of decreasing sizes, to facilitate proper and consistent alignment. The 
equipment may be simply made, either using a horizontal camera with 
a vertical copy holder, or a horizontal copy holder with the camera 
mounted vertically. One of the methods of producing a suitable mounting 
is to make a bracket and mount the camera on to a standard enlarger, 
preferably one in which the head moves in a locating channel in the 
column, as this will prevent the camera rotating about the column. 
Suitable equipment can also be made from timber, Dexion or optical 
bench parts. 

AV-7 A 



The illustration on page 3 shows a typical arrangement for use when 
copying black-and-white transparencies, translucent copy or when 
photographing small objects requiring back lighting. For normal 
artwork, a copy holder may be substituted for, or mounted on the viewer 
and normal copy lighting added as illustrated on page 8. 

Choice of camera : Any camera should be suitable. Initially, the size 
of transparency required will in the main determine the choice; the 
method of production will also affect the choice of camera. The camera 
should be capable of accepting extension tubes or close-up lenses, to 
ease the problem of sealing with small and difference sizes of original. 
However, if a suitable large size of original copy or art work is selected, 
simple cameras, such as the Kodak 'Instamatic' cameras, may, with care, 
be used. 

Choice of lens : The lens used for copying whether on an enlarger or 
camera, should preferably be of the so-called "flat field" type. At 
the close distances and higher than normal magnifications used in this 
type of work, the curved field of view of normal camera lenses can lead to 
some softening of focus. Trouble from this cause can sometimes be 
recognised by the difficulty experienced in obtaining sharpness simul- 
taneously at the centre and at the edge or corners of the screen. A 
smaller aperture will normally overcome this difficulty, but with some 
lenses, particularly those of shorter focal length, this may mean stopping 
down too far when diffraction effects, due to the extremely small aperture, 
may again lower overall sharpness. 

It is recommended, therefore, that for the best results care be taken 
to select a lens of reasonable focal length, as well as one copy, process 
or enlarger type, designed to give a flat field. It should be remembered 
too that the use of lenses of very short focal length may give rise to 
perspective distortion (obliquity). As the angle of view increases from 
the lens-axis, with raised letters for example, more of the edges of the 
letters can be seen, and their apparent shape changes. A longer focal- 
length lens used at a slightly greater distance from the copy-board, will 
in most cases, correct this. 

Exposure : Many of the films that are used for making titles, diagrams, 
etc., are of the reversal type, and with these films accurate exposure is 
important. This is particularly so when using colour films, as a small 
deviation from correct exposure may upset the colour quality of the 
projected image considerably. It is advisable to use an exposure meter 
in order to obtain consistent results. 

Owing to the varied and unusual lighting conditions which are 
encountered, it is not possible to give specific exposure recommendations 
for all types of transparency making techniques. 

Lighting 

With the lighting arrangements shown in Figure 2, which is used for 
most copy operations, ensure that the light distribution is even over the 
whole area of the easel. 

7 AV-7 



The evenness of the light can be checked with an incident-light meter 
measuring the light reflected from a white or more usually a grey card, or 
alternatively by placing a 12 in. opaque rule against the copy, parallel 
to the lens-easel axis, and observing the evenness of the shadows produced 
on either side. 

Particular care should be taken in the placing of the lights to avoid 
reflections from the copy, the copy board, or the lights themselves. If 
care is not taken, the resultant image may not only be seriously degraded 
but, in certain circumstances, can be completely obliterated. 

The reflections affecting control of lighting are as follows : 

1 Reflections of the lights into the camera lens by the copy itself, 
especially if the copy has a rough, creased or curved surface. 

2 Light, reflected by the copy or its surroundings, striking the front 
of the camera and causing an image of the camera to appear on the copy. 
This is most noticeable when photographing glossy or glass-covered 
originals, particularly those with any large dark areas. 

Reflections of the first type can sometimes be avoided by placing the 
lights outside the reflection angle of the lens (shown in the diagram). 
A further method is by applying a matt lacquer, or a specially prepared 
anti-reflection compound such as Win-Gel (made by Winsor and Newton 
Ltd.). 




cork. 



Figure 2. Lighting arrangements for copy : 

Reflections of the second type can often be eliminated by painting 
the copy board with matt black paint, by masking with black paper any 
white or highly polished areas that fall within the field of view of the 



AV-7 



camera, or by covering the front of the camera, except for the lens, with 
black card or paper. The area immediately within the vicinity of the 
camera and copying easel should also be darkened. White or brightly 
coloured clothes or overalls worn by operators near the camera may also 
give rise to unwanted reflections. 

The foregoing is particularly significant with the use of colour films, 
as the inclusion of unwanted reflections in the subject area covered 
by the camera not only produces undesirable "ghost" images of the 
various parts of the copying equipment, but also reduces colour saturation. 
Data Sheet FT- 11, gives details of the various applications of the KODAK 
Tola' Screen which, when used over the camera lens, and with suitable 
polarizing sheet material over the lamps, can give control of reflections. 

Two or more No. 1 or No. 2 reflector Photofloods comprise a suitable 
lighting set-up for copying, etc., when used with artificial light type film. 
The lamps should be placed equidistant from the title board on either 
side of the camera, as in Figure 1. Flash, pulsed xenon or daylight 
can all be used as light-sources. The choice will depend on the equip- 
ment available and to some extent on the type and size of the original 
to be illuminated. Except for deliberate special lighting effects, even 
lighting is most essential. 

Lighting, change of colour temperature with voltage : To ensure consistent 
colour rendering when producing a series of transparencies by tungsten 
lighting, adequate voltage stabilization is essential. Minor fluctuations in 
voltage have a quite large effect on colour balance. 

With a 3200 K floodlamp on 240 volts, colour temperature will be 
lowered approximately 108K, by a drop of 20 volts. On a 110 volt 
system, the same drop in colour temperature is brought about by a drop 
of only 9 volts. 

It is possible to calculate the approximate fall in colour temperature 
produced for a given drop in voltage. 



ST = Tc — 620 degrees per volt 
2Vt 

When 

ST = Change in colour 

temperature in K per volt 

Tc = Initial colour temperature 

Vt = Voltage at which such a 
300 2,o 220 230 2 4o colour temperature is produced 

VOLTAGE 

Figure 3. Curve showing approximate relationship between colour temperature and 
voltage. The formula by which other combinations may be calculated is also given. 

9 AV-7 



COLOUR TEMPERATURE AT VARIOUS VOLTAGES 



Voltage 


Colour Temperature 


CORRECTION * 
Nearest 'Wratten' Filter 


240 V 
230 V 
220 V 
210V 


3200 K 
3144 Kf 
3083 Kf 
3016 Kf 


Normal 
82 Filter 
82 ,, 
82 A „ 



* Approximation; only to be used as a basis for practical experiment. 
t Rounded to nearest whole number. 

Lighting, change of output with voltage : Fluctuations in voltage also vary 
the output of tungsten lamps, roughly as the fourth power of the voltage. 
For example, a drop of 40 volts from a 250 volt supply can halve the 
lamp output and double the required exposure. If a variable light 
source is required, it is suggested that to avoid colour changes, the lamp-to- 
subject distance is altered. 

Photoflood lamps also tend to darken with age and the output and 
colour of their light then changes considerably. As soon as any darkening 
is noticed, both lamps should be replaced with new ones, otherwise 
unbalanced illumination may result. 



AV-7 



10 



BIBLIOGRAPHY 

Books and Pamphlets 

Audiovisual Aids and Techniques in Managerial and Supervisory 

Training. 

Hamish Hamilton Ltd., 90 Great Russell Street, London WC1; 1969. 

Audiovisual Methods in Teaching. 

Edgar Dale. Holt, Rhinehart and Winston Inc., 383 Madison Avenue, 

New York; 1969. 

Diagrams. 

Studio Vista. London 1969. 

Making Lantern Slides and Filmstrips, Focal Press 1953. 

Making Slide Duplicates, Titles and Filmstrips. 

Norman Rothschild. Chilton Press, 915 Broadway, New York; 1965. 

The Overhead Projector. 

L. S. Powel, British Association for commercial and Industrial Education, 

26a Buckingham Palace Road, London SW1. 

Periodicals {Monthly) 

'Visual Education' published by National Committee for Visual Aids in 

Education, 33 Queen Anne Street, London Wl . 



Further information may also be found in Kodak Data Sheets AV 
Audiovisual Series, CL Colour Series, and in Reference Sections RF-3, 
RF-4 and in the GN General Technique Series. 

In the education field "The National Audio-Visual Aids Centre", 
254/256 Belsize Road, London NW6, provides advice, on equipment and 
materials and will advise on the proper use of visual aids. 



APPENDIX 

Materials suitable for producing colour transparencies for direct 
viewing, projection or use as an original for subsequent duplication. 
For fuller information consult the Data Sheet listed against the film. 

REVERSAL MATERIALS 

Materials suitable for producing colour transparencies for direct 
viewing, projection or use as an original for subsequent duplication. 

Kodak High Speed 'Ektachrome' film, daylight type and type B 

Very fast, multi-layer, reversal colour film, intended for processing 
by the user, or by suitable processing laboratory. (Data Sheet FM-1B). 

1 1 AV-7 



Kodak 'Ektachrome' Film, daylight type and type B 

Medium speed, multi-layer reversal colour film, intended for user 
processing, or processing by suitable processing laboratory. (Data Sheet 
FM-1D). 

Kodak 'Ektachrome-X' Film, daylight type 

Multi-layer reversal colour film for general outdoor photography or 
for use with electronic flash or blue flash bulbs. (Data Sheet FM-1E). 

'Kodachrome' II Film, daylight type and type A 

Medium speed, multi-layer, reversal colour film, processing by Kodak 
Laboratory included in original price. (Data Sheet FM-2a). 

'Kodachrome-X Film, daylight type 

Fast, multi-layer reversal colour film, processing by Kodak Laboratory 
included in the original price. (Data Sheet FM-2B). 

NEGATIVE-POSITIVE MATERIALS 

For use where a negative-positive process is preferred. This would 
normally be where both prints and transparencies are needed, or where 
large numbers of duplicate transparencies are required. 

Kodak 'Ektacolor' Professional Films, Type S and Type L 

These negative films contain colour couplers to provide automatic 
colour correction, make possible excellent quality colour reproduction 
without supplementary masking. (Data Sheet FM-3). 

'Kodacolor-X' Colour-Negative Film 

Produces negatives in complementary colours from which transparencies 
can be made by printing. 

Kodak 'Ektacolor' Print Film 

Multi-layer colour film for the production of positive colour trans- 
parencies from colour negatives. (Data Sheet FM-3A). 



Kodak and product names quoted thus 'Wratten' are trade marks 



Kodak Data Booklet KODAK LIIMITED LONDON 

AV-7 

PDA V-7/xWP I 1/10-70 



PLANNING. PREPARATION AND LEGIBILITY IN 
THE PRODUCTION OF TRANSPARENCIES FOR 
PROJECTION 



If the communication of ideas and data by the use of projection techniques 
is to be effective, proper planning and preparation are essential. The key 
to effective visuals for projection is in co-operation and understanding 
between lecturer, photographer and artist of the objectives and of the level 
at which the presentation is to be aimed. To achieve effective com- 
munication with an audience, all those concerned should have a proper 
appreciation of, and should plan for, the more important factors affecting 
the ability of the audience to perceive, understand and retain projected 
information. 

One important point is — why use visual training in preference to other 
forms ? In general, people learn more quickly through seeing and hearing, 
than through hearing alone. Therefore, while other forms of training 
should not be ignored, visual presentation of information is a most 
important means of communication. 

Achieving the smooth, unobtrusive but effective presentation of 
information by the use of slides or film strips, need not be difficult. For 
general guidence, an outline of the main points to be considered follows. 



FACTORS AFFECTING COMMUNICATION 

Effective visuals rely on the following factors : 

1. The needs of the subject 

The subject itself may well impose an outline or discipline of its own on 
the way the information is prepared and presented. For example, visuals 
intended to impart factual information will often require a quite different 
treatment from those intended to impart ideas or emotions. 

2. The needs of the audience 

The composition of the audience must be carefully considered. What 
age group, sex, educational background will it be composed of? Will the 
audience be hostile or sympathetic to subject or speaker? Does the 
audience have any prior knowledge of the subject; if so, to what level? 
All these questions affect the receptivity of the audience and so affect the 
effectiveness of the planned visual. 

3. The needs of the speaker himself 

The speaker or lecturer will have to stand before the audience and deliver 
his address. All the visuals must, therefore, support him in making his 
point to the audience. Occasionally, the presentation of information will 
be by visuals alone with no speaker present; visuals may have to be pre- 
pared differently for this type of presentation. 

The use of a check list, as given in Appendix 1, ensures that none of the 
points above is forgotten or missed. 

Issue B Kodak Data Booklet 

AV-6 



PLANNING AND APPROACH 

When the basic outline plan has been produced, taking into account the 
factors given briefly in the previous section, the lecturer, author or visual- 
izer can then discuss with the artist and photographer the visuals required 
to illustrate each point. It is then probable that after discussion the out- 
line plan will be changed to accommodate new ideas and to overcome pre- 
viously unforeseen difficulties. After analysing the problem, and estab- 
lishing the objectives and strategy to be used, an effective work plan can be 
devised. In order that visual and story continuity can be maintained, the 
use of a planning board is strongly recommended. 

The planning board 

This is merely a board on to which can be clipped, slotted or pinned a 
series of planning cards. The completed board gives at a glance the 
sequence and type of visuals to be used. At any time during the actual 
production of the story the lecturer can utilize the planning board to go 
through and practise his presentation, for either his own or an observer's 
evaluation. This does not interrupt actual production. The talk can thus 
be given its final polish simultaneously with the actual production of the 
illustrations. 



A 



4 








Figure I 



Through the planning board, the photographer also becomes familiar 
with the entire story line. He can see how each illustration relates to 
others in the sequence, and how each message will be presented and the 
point each transparency is to make. The lecturer is helped by the board 
in the organizing and planning of his presentation as a coherent whole. 
The use of a planning board helps to make the production smooth and 
effective (see Figure 1). 



AV-6 



Planning board cards 

The cards used on the board can be standard filing cards, or even post- 
cards. These cards should be marked with various areas; one facet of 
information can then be recorded in each area. For example the lower 
part of the card can be used to write in the idea, continuity or summary of 
what will be said while that transparency is being shown to the audience. In 
a rectangle at the top left of the card, a rough sketch of the major elements 
or components of either the proposed artwork or photograph should be 
included. The right-hand side of the card can contain notes relating the 
actual production details. Here symbols can be used to denote long shot, 
extreme close-up, background colour and type, etc.; any reference or file 
number can also be recorded in this space. 

The cards, if suitably designed, also form a useful record of work done. 
They can also be used finally as part of a card file reference system of what 
slides are available for the future. 

Planning individual transparencies 

It is important that before actual production of transparencies begins, 
certain points should be established. For example, what actual points of 
information are to be conveyed ? Are these best conveyed by one slide or a 
series ? 

The following points are some of the more important factors to be 
considered : 

I The way the information is to be presented should be carefully thought 
out; style, type of lettering and colour are each important in achieving 
effective visuals. An example is given in Figure 2, first in figures and then 
more clearly with the Temperature as blocks and with the Rainfall super- 
imposed as a line. 



Town A 

Temperature F 

44 48 51 59 66 70 73 73 71 67 56 46 
Rainfall 

6.2 4.6 3.5 1.5 0.3 - - - - 0.4 2.5 5.7 

Town B 

Temperature F 

45 49 53 59 66 74 B1 79 72 63 53 46 
Rainfall 

4.8 3.8 3.4 1,6 1.1 0.5 - - 0.8 1.4 2.8 4.4 

Month 

JFMAMJJASOND 



Town A 75 
70 
65 
*- 60 
° 55 
50 
45 

Town B 80 
75 
70 

u. 65 
o go 

55 
50 


;> 


s 










"1 


! 


7 
6 

in 
I 

3 <-> 

z 

5 ^ 

4 x 
U 

3 Z 


J F M A 


M 


J 


J 


A 


S 


O 


N D 

1,- 









Figure 2 

2 Include only a limited amount of information in each transparency, if 
necessary using more than one illustration to make a particular point. 

3 Remember that a close-up has more impact than a general view; the 
view is mainly used to set the scene, whilst a close-up makes a specific 
point. 

4 Try to standardize on a small range of techniques and styles of presenta- 
tion and do them well; avoid over-elaboration. The important point is 
that the audience should notice not the transparency but only the infor- 
mation it contains. 



AV-6 



A summary of the preceding sections is given in the form of a check list 
at the end of this data sheet (Appendix 1). 

THE USE OF COLOUR 

With the increased use of 5 x 5 cm (2 x 2 inch) slides, it has become more 
common for line and colour pictorial slides to be used in the same lecture. 
Mixed slides, when shown in quick succession and with constant changes 
from colour to black-on-white line transparencies and from line to colour, 
can be not only distracting, but may cause actual discomfort to the viewer. 

The large luminance difference between colour and black-on- white 
slides, or rapid changes from one saturated colour to another, may cause 
distress by requiring the eye and brain to accommodate a wider or more 
rapidly changing range than normal. Avoid using large changes in 
luminance or colour, therefore, but also note, with succeeding slides, that 
a slight mis-match in background colour will be noticed and may be just 
as distracting. 

Colour should be used in such a way that attention is called to the point 
of information, not to the colour itself. Colours that clash one with 
another, either on succeeding slides, or when used to differentiate between 
various points within a particular slide, should be avoided. Certain 
mauves and lilac colours, for example, are unacceptable when combined 
with some yellows and bright greens. Colours also tend to indicate speci- 
fic feelings or atmospheres; blue and green — coolness, orange or reds — 
warmth. A red title or graph would jar if included in a series of arctic 
pictures. Similarly, in a sequence on furnaces, it would be inappropriate 
to use blue for the slides used in presenting the data. 



THE PREPARATION OF MATERIAL 

Quite satisfactory coloured artwork charts and diagrams can be made 
without great difficulty or expense. Block or Pie diagrams can be made 
from coloured paper or plastic, cut to size and laid on to a plain or coloured 
background. Titles, individual parts of flow charts or organization 
structure diagrams, may be typewritten, cut out and placed on a coloured 
sheet and dry transfer lines can be used to join them to show flow, or 
indicate lines of responsibility. 

Numerous effects are possible in the preparation of material for trans- 
parency making. For example, the use of three-dimensional title letters 
which, when illuminated by a single spodight placed obliquely (normally 
above and to one side of the copy-board or easel), produce a feeling of 
depth, where the letters appear to stand out. If the light is below the 
letters, an impression of negative depth, i.e., recessed letters, is given and 
this may appear unnatural. Coloured filter material may also be used over 
the spotlights in order to produce a blend of various colours; this technique 
can give either strong or subtle effects as required and the full possibilities 
may be explored experimentally. 

Greater emphasis can be given to a title or subject by controlling 
independently the level of illumination, of the title or subject and the 
background. This can also be achieved by mounting the objects, or data, 

AV-6 4 



on to glass, Perspex, or plastic, and placing a photograph or a coloured 
background at a convenient distance behind the subject, say 7 inches 
(177 mm) or more. 

The use of black velvet as the background is very effective and gives the 
appearance of items suspended in a void. However, with colour films, 
which normally have a lower maximum density, this is not so effective. 

Backgrounds 

The choice of background, lighting and composition is directly in- 
fluenced by the subject. Very good backgrounds can be made from 
such materials as wallpaper, metal foil, grained wood, plastic or fibre glass 
sheets and fine coloured powders, etc. The choice and variety of mate- 
rials for backgrounds is virtually unlimited, depending only on the ability 
of the photographer to choose an appropriate material. A bright, flowery 
background is obviously unsuitable for a slide or film strip on engines, and 
likewise an angular background would hardly be in keeping with a story on 
rural life. 

For productions on science, architecture, handicrafts, and similar tech- 
nical subjects, the background is best kept to a mid-tone. An unobtrusive 
geometric pattern might help to fill the frame and enhance the mood. For 
subjects of a softer nature, a more delicate pattern can be used to advantage. 
The shadow of a branch and leaves on a background of a whitewashed 
garden wall may be appropriate to a nature subject. The vast majority of 
backgrounds are well served by plain colour of a medium saturation, so 
allowing both black and white information to be seen with equal contrast 
and, therefore ease. If only white information is being used, then greater 
colour saturation or a darker hue may be chosen for the background. 
Coloraid paper forms an ideal background for block letters. 



RECOMMENDED SIZES AND FORMATS FOR FLAT ARTWORK 

For 80 to 90 per cent of new, flat artwork, it should be possible to 
specify for each format*, a single, standard size for the area of the artwork 
that is to be reproduced on the transparency, e.g. one area for 35 mm 
reproduction (5x5 cm) and another for super 8 reproduction. This 
standardization of the majority of work for each format will result in 
greater convenience, fewer photographic errors in copying, savings in 
time and money, increased production, and transparencies of higher and 
more uniform quality. 

It is less essential that the width of paper surrounding the area to be 
reproduced should be standardized, although this may be useful when 
filing. Extra surround must be allowed if punch register* or a similar 
method is to be used for the registration of overlays* or for accurate 
location during photography. 

Artwork format 

The format of the area to be reproduced must match the format of the 
medium* being used e.g. : 

* See Glossary, page 15. 

5 AV-6 



Medium Approx. proportions 
of format 



Shape of artwork 



35 mm transparency 


2 


: 3 


vertical or horizontal rectanj 


126 transparency 


1 


: 1 


square 


Overhead projector 








transparency 


1 


: 1 


square 


16 mm movie film 


3 


: 4 


only horizontal rectangle 


Super 8 and double 








8 mm movie film 


3 


: 4 


only horizontal rectangle 


Television 


4 


: 5 


only horizontal rectangle 



Artwork areas 

• Overall area. 

• Area to be photographed and projected. 

• Area containing information. 



Example 



o o o 



o o o 



10in - 
10 1 / 2 in 

12in 



e\'\ri 7 in 9 in 



Li 



KEY 



■ Area containing information 



Total area of artwork 



Area to be photographed O O O Punch registration holes 



The dimensions given are suitable for 35mm reproduction 
AV-6 



Overall area: This gives a surrounding strip or margin to the area to be 
photographed to enable : 

• Centralization of the information to be photographed. 

• Artwork not placed squarely on the paper to be straightened at the 
photographic stage. 

• The moving of the artwork further from the camera than originally 
planned, to accommodate a non-standard size or format. 

A pattern or colour that is to "run out" of the side of the projected 
picture must be continued into the surrounding strip or margin. 

Area to be photographed and projected: For conventional uses, this 
area must allow a margin between the information on the artwork and the 
edge of the area to be photographed. This will ensure that the small 
amount of masking, that is necessary when mounting transparencies, does 
not result in information touching the sides or "running out" of the 
picture projected on the screen unless, of course, this is intentional. If 
transparencies are to be projected side-by-side and pictures or lettering 
from separate transparencies are to blend, it will be necessary to do away 
with this margin almost completely. If the information content of each 
slide is to be kept separate, it will be necessary to increase the margin. 
The choice of different colours for the backgrounds to the transparencies 
also helps to keep them self-contained. 

Area containing information: This is the area in which the drawing, 
lettering, etc., can be placed. It obviously lies within the area to be 
photographed. 

Example : If a | sheet of Coloraid paper is used to prepare artwork for 
a 35 mm slide, the various areas described above could have the following 
dimensions. 

The overall area=9x 12 in. 

The area to be photographed and projected=7x 10J in approximately. 

The area containing the information=6|x 10 in approximately. 

A sheet of transparent plastic or acetate material, with these dimensions 
marked upon it, can be of great help when preparing artwork. Such a 
sheet is called a template. It can be laid over the artwork and the 
boundaries of the areas concerned are immediately indicated. A separate 
template should be prepared for each format used. It is possible to 
include all the formats on one template but this may be found confusing 
and errors may result. An alternative template method is to use a mask 
made of thin card with an aperture cut to the dimensions of the area to 
contain the information. This can then be placed over the artwork during 
its preparation. 

Artwork size 

The size of a piece of artwork is determined by many factors and may 
have to be a compromise. The following factors and availabilities must be 
considered : 

• Quantity of work involved. 

• Finance for artist, photographer, materials, etc. 

• Time. 

7 AV-6 



• Workflow — steady or spasmodic. (The latter may result in the 
technique being forgotten between one batch of work and the next). 

• Type of equipment. 

• Type of work (e.g. will punch register be used?). 

The small user: The small user will probably produce and photograph 
his own artwork. He will therefore have everything under control and 
can be organized accordingly. The following size of artwork is suggested 
for this type of user. 

A whole sheet of 18x24 inch Coloraid paper or equivalent can be 
divided into four giving a sheet size of 9 x 12 inches. This is sufficiently 
large to give high quality projected images at the degrees of magnification * 
usually required. It is also sufficiently large to work on with dry transfer 
lettering and the normally available sizes of pens and pencils, even when 
a considerable amount of detail is required. It is sufficiently small to be 
convenient for desk-top working, filing in conventional filing cabinets 
and photographing with non-specialist equipment in non-professional 
surroundings, e.g. offices, classrooms, etc. A 9x12 inch size is also 
convenient when 8x 10 inch photographs are to be used. 

The large user: The large user may produce and photograph his own 
artwork, but he is more likely to delegate these tasks and, therefore, they 
will not be under his direct control. In either case, the volume of work 
will be greater than with the small user. The flow of work is likely to be 
more steady and the variety greater and/or more sophisticated. This makes 
streamlining for fast production and economy even more important. For 
this type of user the following size is suggested. 

A whole sheet (18x24 inches) of Coloraid paper or equivalent can be 
divided into two, giving a sheet size of 12 x 18 inches. Professional artists 
generally prefer to work on a sheet of this size, because it gives them 
greater freedom in composition and layout* (they can crop and vary the 
position of the centre of interest after the drawing and lettering has been 
done). If the artist plans his layout well, the area within which he must 
work could be as large as 10 X 13 inches. At this size, the artist needs to 
use less precision in his drawing and lettering (reduction* is greater 
during copying). However, if less planning is done through lack of time 
or insufficient guidance, the finished area containing the information 
could be only slightly larger than that prepared from a 9x 12 inch sheet 
and the working advantages of the larger size will be lost. 

Artists unfamiliar with this type of work must be reminded to give 
the margins discussed under the heading "Artwork areas". 

There are inevitable disadvantages in preparing large artwork rather 
than small. These are higher expenditure on materials (larger dry transfer 
lettering, the need for more paper and overlay materials, etc.) and the 
extra expense in photographer's time, since the artwork is less likely to 
be of standard size and the photographing of each piece may therefore 
be slightly different (involving changes in camera position, focus and 
lighting). This extra expense may be slightly offset by the artist taking 
less time to prepare artwork because less precision and calculation is 
required. 

• See Glossary, page 15. 

AV-6 8 



Sizes for information on artwork 

A reliable and obvious guide to the acceptable size of detail in a trans- 
parency is whether it can be recognized or read easily by a typical viewer 
at a reasonable distance. For viewing books, photographs, transparencies 
projected on to screens, and other items that are to be exhibited, it is 
usual to prepare material so that it can be viewed comfortably by most 
people at distances of between 3Hf and 9Hf, where H is the height of 
the image being viewed. In the case of a projected transparency a typical 
height for the projected image (limited by the screen size) might be 
three feet (approximately 1 m). For this size, the audience would be 
expected to be between 9 and 27 feet (approximately 2.7 and 8.2 m) from 
the screen. At both these distances, and between them, the screen image*, 
and the subject matter it contains, should be clear, legible and comfortable 
to view. Similarly, viewing the artwork at distances of 3H and 9H (where 
H is the height of the artwork) will guide you or the artist in selecting 
appropriate designs, colours, line widths, sizes for lettering, etc., e.g. for 
a 9x 12 inch piece of artwork, mask down the area intended for photo- 
graphy — 7x10^ inches approximately — and view it from 21 inches 
(approximately 530 mm) and from 63 inches (approximately 1.6 m) 
(3H and 9H). It is even worth checking that it is still satisfactory at 
72 inches (approximately 1.8 m), as you can rarely be precise in your 
estimation of audience area, nor can you guarantee the standard of the 
eyesight of your audience. 

Minimum height of elements (letters, symbols, etc.) for 3H to 9H viewing: 

As a general guide with 35 mm images, the height of the artwork area 
that will contain the information, e.g. in the example above this will be 
6^ inches, should be divided by 50 to obtain the minimum advisable 
height for one element* (a letter, symbol, etc) of the artwork. In the 
example above, such an element should be at least 0.13 inch high. For 
characters of this size, a maximum drawing pen width of 0.6 mm will be 
suitable. However, this pen width may be unsuitable for the surface 
texture of some papers, and a 1.2 mm pen width may be the workable 
minimum in many cases. 

This minimum element height is only a rough guide and should be 
exceeded whenever possible. Anything smaller is not likely to be seen 
when viewed at 9H. Important detail should be larger than this. Often, 
bold treatments or large characters are beneficial. 

Division by 50 works well for 35 mm projected images, while division 
by 25 works well with 16 mm, super 8, double 8 and television images. 

The letter size discussed here is the height of a lower case letter, 
excluding ascenders or descenders (the "tails" on p, g, b, d, etc.). In 
determining or specifying letter size for artwork, the smallest letters 
should be measured. 

Minimum height of elements (letters, symbols, etc.) for viewing at 
distances greater than 9H: At viewing distances greater than 9H, the 
screen will appear small, and fine detail may become difficult to see. 
There are two possible solutions to this problem. 
|3H=3xH, 9H=9xH. 
* See Glossary, page 15. 

9 AV-6 



• Use a larger screen (screen image) so that your audience returns to a 
maximum of 9H viewing. 

• If screen image (image size) cannot be increased, modify the size of 
the letters as follows : 

For 12H viewing divide height by 35 (17). 

For 16H viewing divide height by 30 (15). 

For 18H viewing divide height by 25 (12). 

(Figures outside brackets refer to 35 mm, figures within brackets 

refer to 16 mm, super 8, double 8 and television.) 
The second solution given above sometimes requires a good working 
knowledge of the lecture room conditions and projection situation, as the 
artwork may have to be tailor made. 

It is preferable, both from the audience's and artist's point of view, 
for the minimum size of element (letter, symbol, detail, etc.) to be very 
rarely used. Furthermore, the use of several transparencies, each con- 
taining a small amount of information, is likely to communicate far more 
effectively than a few transparencies each containing a wealth of informa- 
tion. It is important to pick out salient points and present them individu- 
ally, as clearly as possible, or in small, coherent groups. The method of 
presentation obviously depends on the type of material and audience. 
Even the most erudite of audiences can doze off if the presented material 
is not sufficiently stimulating. 



Long-distance viewing (large H factors): Transparencies that are used in 
small, rear-projection cabinets at exhibitions or display situations, are 
often viewed from distances greater than 9H. For this type of application, 
an image as small as 8 inches high may have to be readable at distances 
up to 20 or 25 feet (approximately 6 or 7.5 m) (approximately 36H). 
Lettering should, therefore, be at least four times larger than the minimum 
for 9H viewing. For an information area of 6 inches on the artwork, the 
minimum letter height should be half an inch. 



Television : Television images are frequently viewed at relatively great 
distances. For example, an image only 12 inches high (from a 21 inch 
picture tube) may often be viewed at 17 feet (approximately 5.2 m) (18H) 
in a classroom. Therefore, when material is being prepared for such use 
legibility must be sufficient for this viewing distance. As in all artwork 
preparation, the element size given previously is the absolute minimum 
that may be used, If possible, sizes should exceed this. 

Another factor to consider when preparing artwork for television is 
that some area of the original transparency may be lost in the trans- 
mission chain and in the receiver. The amount lost is not always the 
same; it will vary with such things as receiver adjustment and line voltage, 
as well as with the line standard. To ensure minimum loss, any essential 
information must be confined to a central area. An extra precaution of 
a larger-than-usual margin between the information area and the area 
to be photographed will avoid cut-off of information occurring. 

AV-6 10 



Other factors in artwork design 

Style of lettering: An important consideration is the style of lettering used. 
Some typefaces are easier to read than others. Some have a character 
which they can impart to the message they are conveying. Some look 
better in a light version rather than a bold version. Some bold versions 
of typefaces are difficult to read. Typical typefaces used for transparency 
artwork are Helvetica, Berling, Futura, etc. They are usually available 
as dry transfer lettering in a range of sizes. As a general rule for con- 
ventional work, it is safest to keep to one typeface for a set of trans- 
parencies, and to use either all capitals, or to standardize on a mixture of 
capitals and small letters. This will establish a style, and give the set 
cohesion. 

Horizontal spacing: The spacing of the elements across the transparency is 
important. For the smallest element sizes mentioned earlier (remembering 
that these were the absolute minima and should be exceeded whenever 
possible) the maximum number of elements that it is advisable to have in 
one line is twenty-six. This allows for normal spacing between letters, 
words, symbols, etc. Of course, if elements are larger, the maximum 
number per line must be reduced. 

Vertical spacing: With the minimum element size mentioned earlier, it is 
usual to limit the number of lines on the transparency to 7. When elements 
are larger than the minimum, the number of lines should be reduced. 
Normal spacing between lines is 1 J times the height of the elements. 

Contrast: It is essential to maintain good contrast between the information 
carried by a transparency and the background against which it appears. 

If using only black-and-white materials, a transparency with white 
writing on black is more comfortable to view than black on white, because 
of the dazzle from a large area of white screen. A white on black trans- 
parency can be obtained by preparing artwork with black lettering on a 
white background and photographing on to negative film stock developed 
to give fairly high contrast. Colour can be introduced to such a trans- 
parency by mounting the transparency together with a piece of coloured 
acetate of the same size. This will result in the information appearing 
coloured against a dark background. Suitable colours for this technique 
are mid-toned greens, blues or violets. 

When using colour materials, the scope for artwork design is obviously 
far greater. The choice of colours is largely subjective, but sufficient 
visual contrast, in tone or colour, should be maintained between the 
information and background. If you are relatively inexperienced in 
preparing artwork for transparencies, it may be worth getting several 
opinions on various colour combinations. People suffering from defective 
colour vision may have difficulty in distinguishing between certain 
colours, e.g. green and red or blue and green. It is therefore wise to avoid 
these colour combinations when preparing artwork for transparencies. 
Good tonal separation as well as colour separation helps to avoid problems 
for this type of viewer. 

1 1 AV-6 



The contrast of the projected image is affected by the level of ambient 
lighting in the room and the condition of the projection screen. With the 
KODAK 'Ektalite' Projection Screen, which is used with normal room 
lighting, the position and angle of the screen is an important factor. With 
matt white, beaded or lenticular type screens, the best projected image 
contrast will be obtained when the room is completely dark. However, 
this is quite often impracticable and it is frequently necessary to have 
sufficient room lighting to allow note taking to take place. This level of 
room lighting is likely to reduce the effective contrast of the screen image 
considerably. It should be allowed for in the preparation of the artwork 
by increasing the visual contrast of the transparency. 

Clarity of information: Among the obvious factors to consider are: 

• Grouping of information. 

• The audience's ability to recognize and identify patterns of information 
rather than individual symbols, letters or words. 

• The audience's subject knowledge (see Appendix 1). 

• Psychological effects of colour. 

• Whether the visuals are accompanied by a verbal (live or recorded) 
commentary or have to stand on their own. 



AV-6 12 



APPENDIX I 

CHECK LIST FOR PREPARING AUDIOVISUAL PRESENTATIONS 

1. Identify the essential points. What information is to be communi- 
cated? What is the aim of the presentation? 

2. Identify the people to whom it is wished to communicate. 
Who are they? 

What is their level of literacy ? 

How numerous are they? 

What level of general education have they reached ? 

What is their level of motivation to study this particular subject 

matter ? 

What is their probable level of retention? 

Have they a prior knowledge of the subject matter? 

What is their likely reaction to the subject matter ? 

What is their age and sex? 

3. Identify how best to communicate the information to the required 
people. The method of communication must be at the appropriate 
level, i.e. method of presentation, vocabulary and mathematics to be 
at a level they will easily understand; speed of delivery of new infor- 
mation to be at appropriate level and given the necessary amount of 
impact. Ensure that the visuals are relevant to the subject matter 
and the audience. 

4. Ensure that each visual conveys only one idea or part of an idea. 
Work from known to unknown information and from particular 
points to the general overall picture. 

5. Ensure that visuals and text are complementary to each other but not 
identical. 

6. When both planning board and text drafts are complete re-examine 
them for level of content and vocabulary, etc., applicable to the 
audience and remove any material that does not contribute to the 
understanding of the information. 

At this stage also ensure that the form of presentation is appropriate 
to the time and place at which it is to be given. 



APPENDIX 2 

USE OF TYPEWRITTEN INFORMATION 

Typewritten information is not recommended. However, if it has to be 
used, a single template, as shown below, will make the production of 
legible transparencies easier. 

During the actual camera operation, the outer corner marks should be 
just barely visible in the viewfinder, this will give the correct safety margin 
with most cameras. 

1 3 AV-6 



1 

5mm 



USE THIS TEMPLATE SAME SIZE TO PREPARE 
TYPEWRITTEN ORIGINALS FOR SLIDES 



Enlarge to 215mm x 145mm for Drawings 
and Artwork 



1 

All copy should be typed to fit in the rectangle (a maximum of 14 spaces 
high and 40 elite or 30 pica characters wide). If upper and lower case 
characters are used, the text will be legible up to 45 feet (13.7 m), from 
a 72 inch (1.83 m) wide screen image. The use of capitals alone will 
permit legibility to a somewhat greater distance. Legibility of typewritten 
work being prepared for reproduction can be improved by using a good 
quality white paper and reversing a carbon, so that it prints on the back 
of the main copy. This improves contrast considerably, especially when 
the copy is laid on to a reflective white surface to be photographed. 



AV-6 



14 



GLOSSARY 

Glossary of terms used in this publication 

Elements 

In this context, they are the smallest parts of the information portrayed on the 
artwork, e.g. individual letters or symbols. 

Format 

The shape of the area on which the information is to be presented. 

Layout 

A plan for positioning information and detail on artwork. 

Magnification 

The process of enlarging an original picture, piece of printed material, or artwork. 
In photography this usually involves the use of an optical lens. 

Medium 

The method by which the information is to be presented. 

Overlays 

These are sheets of a transparent material (usually acetate or plastic) which 
contain information additional to the basic artwork. These enable one picture 
to be taken of the basic artwork, and a second picture to be taken showing in 
addition the information on the overlay, e.g. a graph of rainfall year by year could 
have superimposed upon it a graph showing weight of harvest year by year. 

Punch register 

A method of ensuring that artwork, overlays, or a combination of both, are in 
the correct position for copying. Holes, punched in the margins of the various 
items to be positioned, are located over pins or pegs. In this way, the artwork 
can be correctly positioned, and overlays can be superimposed precisely as the 
artist intended. 

Reduction 

The process of making smaller an original picture, piece of printed material, or 
artwork. In photography an optical lens is normally used. 

Screen image 

The image projected on to a screen; in photography by an optical projector, 
in television by a cathode ray gun (part of the cathode ray tube). 



AV-6 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

WRATTEN 

EKTALITE 



Kodak Data Booklet KODAK LIMITED 

AV-6 Printed in England 

YI332PDAV-6/xWPI2/6-73 




FILTERS AND EQUIPMENT 



CONTENTS 



EDITION 



FT-I KODAK 'Wratten' Filters IssueG 

FT-2 Neutral-Density Filters (KODAK 'Wratten' IssueG 

Filters No. 96) and 'Kodak' Photographic Step 
Tablets 

FT-3 KODAK 'Wratten' Filters for Scientific and Issue £ 

Industrial Purposes 

FT-4 Monochromats and Monochromatic Combin- Issue B 

ations from the Range of KODAK 'Wratten' 
Filters 

FT-5 Liquid Filters for the Isolation of Certain Lines — 

of the Mercury Discharge Lamp 

FT-6 KODAK 'Wratten' Filter Colour Separation Sets Issue D 

FT-7 'Kodak' Safelight Filters Issue B 

FT-8 KODAK 'Wratten' Filters Nos. 8 (K2), 9 (K3), Issue D 

II (XI), 15(G), 25 

FT-9 KODAK 'Wratten' Ultra-Violet Filters Nos. 2A, Issue £ 

2B, 2E, I8A, I8B and Infra-Red Filters Nos. 87, 
87C, 88A, 89B 

FT-IO KODAK 'Ektalux' Filters Issue A 

FT-I I KODAK Tola' Screen Issue C 



Associated Data Sheets in this or other volumes or sections 

I, RF-2 Tables of Recommended Safelighting for Handling Sensitized 
Materials 

1, RF-12 The Vibration Insulation of Photographic Equipment 

2, XR-4 Intensifying Screens 

3, CL-3 Filters for 'Kodak' Colour Materials 

3, CL-5 Colour Temperature 

3, PR-6 The Selection of Materials for the Construction of 
Photographic Processing Apparatus 



Kodak, Wratten, Ektalux and Pola 
are trade marks 



KODAK LIMITED 

Printed in England 

Y 1 326PDDB-27/xWP I 0/5-73 




KODAK 'WRATTEN' FILTERS 



The principles involved in the selection of filters, and specific recommen- 
dations for their use in reproducing some of the more common subjects, 
are given below. It should be borne in mind, however, that the photo- 
graphic result obtained depends as much on the spectral sensitivity of the 
material used in the camera, and on the composition of the lighting, as 
on the filter employed; panchromatic emulsions should in general be 
used, but orthochromatic emulsions may be used in some circumstances. 

A coloured subject appears dark in the final print if the photograph is 
taken through a filter which absorbs the colour of the light reflected from or 
transmitted through the subject. This is because the filter allows only a 
little of the fight reflected from or transmitted through the subject to reach 
the sensitized material. For example, when photographing clouds the blue 
sky will need to be darkened relative to the white clouds in the black and 
white reproduction. A yellow filter absorbs blue light and consequently 
increased contrast would be obtained by the use of a filter of this colour. 
In this case, the use of a 'Wratten' 9 Filter and panchromatic material 
would be found most suitable. If more dramatic effects are required, 
'Wratten' 1 1 or 25 Filters may be used. 

This effect can be used in a different way. Because a coloured object 
appears light in the final print if the photograph is taken through a 
filter of the same colour as the subject (in the previous example a filter of 
complementary colour was used to cause the subject to appear dark in the 
reproduction), a deep yellow filter, such as the 'Wratten' 9 Filter can be used 
to photograph documents yellowed with age or staining. The use of 
this filter accentuates the contrast between the printed or written im- 
pression and the background, where it is required that this background 
shall be all of one even, low, density. 

This same principle should, in general, be applied in the selection 
of the filter to show the optimum detail in a coloured subject; that is, 
dark foliage will show the optimum detail when the negative is made on 
panchromatic material exposed through a light yellowish green filter such 
as the 'Wratten' 1 1 Filter or more drastically through the tricolour green 
'Wratten' 58 Filter, or on orthochromatic material through a deep yellow 
filter such as the 'Wratten' 9 Filter. 

Selection of the proper filter for multi-coloured subjects demands a 
measure of judgment. No single rule can be applied, but the problem can 
easily be resolved by careful consideration. The subject should first be 
examined carefully to determine how the various colours are required to 
be rendered in order to show a particular pattern or texture, or in order 

Issue G Kodak Data Booklet 

FT- 1 



to make an object either appear prominent against or merge with surround- 
ing objects or the background. It may be obvious that certain colours 
should be lightened and others darkened to achieve the desired effect. If 
so, the best method of selection of the appropriate filter is usually that of 
examining the subject visually through various filters; as a check, it is as 
well to make photographic tests, using those filters indicated by the visual 
examination to be most promising. If it is not evident which of the 
colours should be rendered lighter or darker than normal, the subject 
should be photographed on a panchromatic material, using in daylight 
a 'Wratten' 8 Filter, or in tungsten light a 'Wratten' 11 Filter. The 
resultant print will reproduce, approximately, the visual brightness values 
of the subject. If this normal rendering is not entirely suitable, the 
choice of a more appropriate filter for a second negative will then have 
been greatly simplified. 

The 'Wratten' 90 Filter is a valuable aid when judging the effect of 
reproducing coloured originals in monochromatic tones. When the sub- 
ject is viewed through this filter the colours lose much of their significance 
and interfere less with assessment of tonal quality. 

When selecting the filter for a particular task it should be remembered 
that a filter of approximately the same colour as a subject (e.g., brick 
buildings and the yellow-orange 'Wratten' 16 Filter) will reproduce it in 
lighter tones and will enhance detail within the area of colour. A filter 
approximately complementary in colour to that of the subject (e.g., blue sky 
and deep yellow 'Wratten' 9 Filter) will reproduce it in darker tones and 
will enhance contrast. The reference table below shows some filters which 
enable some of the more common colours to be reproduced on mono- 
chrome film in light or in dark tone. 



COLOUR 


TO REPRODUCE 


TO REPRODUCE 


OF OBJECT 


LIGHTER 


DARKER 


Red 


29, 25 or 1 5 


47B or 58 


Orange 


25 or 16 


47B or 1 1 


Magenta 


32 


58 


Yellow 


12 or 8 


47B or 38 


Green 


58 or 1 1 


47B, 25 or 15 


Blue-green 


44 


25 or 16 


Blue 


47B or 38 


25, 1 1 or 9 



It should be noted that it is not possible to add these effects by using two 
filters together. For instance, reds and blues in one subject cannot both 
be made lighter by employing the 'Wratten' 25 and the 47B Filters 
together. If these were combined, the 'Wratten' 25 Filter, absorbing 
all colours but red, would stop green and blue light, while the 'Wratten' 
47B Filter, absorbing all colours but blue, would stop red and green 



FT- 1 



light. The result would be that practically no light whatever would be 
transmitted. If a combined effect was required, e.g. both blue and red 
subjects were required to be light, a 'Wratten' 32 Filter would help. 
This filter is magenta in colour. 

Details of the ranges of 'Kodak' Colour Compensating Filters and 
Colour Printing Filters, which are not described in this sheet, may be 
found in Data Sheets CL-3 and PP-12. 

Below is listed the current range of Kodak 'Wratten' Filters, then- 
principal uses and descriptive colours. Further details of certain of these 
niters may be found in other Data Sheets (indicated by a Data Sheet 
number, in italics, following a filter number), and in the book "The Kodak 
range of light filters" : 



FILTER 


COLOUR 


REMARKS AND USE 







Colourless 


For focusing. 


IA 


CL-3 


Pale pink 


'Kodak' Skylight Filter. Absorbs ultra- 
violet radiation. Is of particular use 
with colour film, reducing blue cast 
caused by aerial haze or other sources 
of ultra-violet radiation. 


2A 


FT-9 


Pale yellow 


Absorbs radiant energy below 405 nm. 
Used with monochrome materials to 
reduce haze at high altitudes. 


2B 


FT-9 


Pale yellow 


Haze filter. Absorbs ultra-violet radiation 
strongly. For use with monochrome 
materials when used at high altitudes, or 
at other times when an excess of ultra- 
violet radiation is present. May also be 
used when printing 'Eastman' Colour 
Print Film and 'Ektacolor' Papers. 


2E 


FT-9 


Pale yellow 


Similar to No. 2B, but absorbs more 
ultra-violet. For use when printing 
'Eastman' Colour Intermediate Films, 
Types 5253 and 7253, and 'Ektachrome' 
Papers. 


3 




Light yellow 


Aerial photography and motion picture 
work as a partially correcting filter for 
excess blue. 


3N5 




No. 3 + neutral 

density of 0.5 


Partially correcting filter in motion pic- 
ture work. Enables a larger lens aperture 
to be used to reduce the depth of field. 


4 




Yellow 


Approximate correction with panchro- 
matic materials for outdoor scenes, 
including sky. Also contrast control with 
'Kodak' Magenta Contact Screens. 


6 




Light yellow 


Partial correction for outdoor scenes 
with panchromatic materials. 



FT- 1 



FILTER. 



FT-8 



8N5 



FT-8 
FT-8 



12 



13 



FT-8 



16 
*I8A 

*I8B 

21 
22 



FT-9 



FT-9 



COLOUR 



Yellow 



No. 8 + neutral 

density of 0.5 

Deep yellow 

Yellowish green 



Deep yellow 



Dark yellowish 
green 

Deep yellow 



Yellow-orange 



Visually opaque 
• filters for 



Orange 
Deep orange 



REMARKS AND USE 



Correcting filter. Absorbs ultra-violet 
and some blue. Reproduces colours in 
their correct monochromatic relation- 
ship when photographing in daylight 
with highly red-sensitive panchromatic 
materials. 

Correcting filter in motion picture work. 
Enables a larger lens aperture to be used 
to reduce the depth of field. 

Absorbs ultra-violet and some blue. 
Tends to over-correct sky. 

Correcting filter. Absorbs ultra-violet, 
some blue, and slightly more red. Gives 
correct monochromatic rendering of 
colours when photographing by tungsten 
with highly red-sensitive panchromatic 
materials. Reproduces greens slightly 
lighter in daylight 

Minus-blue complementary filter. Ab- 
sorbs ultra-violet and blue. Strong over- 
correction when used out-doors. Rend- 
ers blue very dark. Strong haze pene- 
tration. Sometimes used with Nos. 32 
and 44A. 

Full correction for highly-green-sensitive 
panchromatic materials in tungsten light. 

Contrast filter. Absorbs ultra-violet, 
blue, and a small amount of green. Gives 
strong over-correction to sky. Used in 
photomicrography and copying, also for 
special effects in infra-red photography. 

Absorbs ultra-violet, blue, and a small 
amount of green. Gives strong over- 
correction to sky and enhances detail in 
brick, furniture, etc. 

Ultra-violet work. Visually opaque. 
Used in the photography of fluorescent 
phenomena and in scientific instruments 
to isolate ultra-violet radiations. 

Ultra-violet work. Used in ultra-violet 
and infra-red (non-visual) flash photo- 
graphy, and in scientific instruments. 

Contrast filter. Absorbs blue and blue- 
green. 

Contrast filter. Absorbs ultra-violet, 
blue, and some green. Used in micro- 
scopy to increase contrast of blue pre- 
parations. Transmits only yellow radia- 
tion from mercury-vapour lamps. 



* Available only as a glass filter. 



FT- 1 



FILTER 


COLOUR 


REMARKS AND USE 


23A 


Light red 


Contrast filter. Absorbs ultra-violet, 
blue, and some green. 


24 


Red 


For "two-colour photography" (day- 
light or tungsten) and for white-flame- 
arc, tricolour projection. 


25 FT-6 and 8 


Red 


Standard, tricolour red filter for colour 
separation. Absorbs ultra-violet, blue, 
and green. Very strong over-correction 
to sky. Used for haze penetration in 
aerial work, and in infra-red photo- 
graphy. 


26 


Red 


Stereo red filter used with No. 55. 


29 


Deep red 


Narrow-cut, tricolour red filter for 
colour separation. Absorbs ultra-violet, 
blue, and green. Used for making colour- 
separation negatives from transparencies. 
Sometimes used with Nos. 47 and 61. 


30 


Light magenta 


Contrast filter. Absorbs green. Photo- 
micrography. Magenta Contact Screen 
Process. 


31 


Magenta 


Strong green absorption. 


32 


Magenta 


Minus-green complementary filter. Ab- 
sorbs green. Sometimes used with Nos. 
12 and 44A. 


33 


Magenta 


For making colour masks for colour- 
reproduction processes. 


34 


Deep violet 


Contrast filter. Absorbs green. 


34A 


Violet 


Minus green and plus blue. 


35 


Purple 


Contrast filter. Absorbs green and some 
red and blue. Photomicrography. 


36 


Dark violet 


Contrast filter. Absorbs all green, more 
red, and less blue than No. 35. Photo- 
micrography. 


38 


Light blue 


Contrast filter. Absorbs a little ultra- 
violet and red. Corrects tendency for 
reds to reproduce too light in tungsten 
illumination. 


38A 


Blue 


Contrast filter. Absorbs some ultra- 
violet and green, and much red. 
Photomicrography. 


40 


Light green 


For "two-colour photography" (tung- 
sten). 


44 


Light blue-green 


Minus-red complementary filter. Ab- 
sorbs red and much ultra-violet. Photo- 
micrography. 


44A 


Light blue-green 


Minus-red filter that strongly absorbs 
from 580 to 680 nm. 


45 


Blue-green 


Contrast filter. Absorbs red, some green 
and blue, and much ultra-violet. Photo- 
micrography. 


45A 


Blue-green 


Giving high resolving power in visual 
microscopy. 


46 


Blue 


Experimental filter for tricolour pro- 
jection. Sometimes used with Nos. 29 
and 57. 



FT- 1 



FILTER 


COLOUR 


REMARKS AND USE 


47 




Blue 


Tricolour blue filter used in colour- 
separation work. It may be used for 
special contrast effects in commercial 
and outdoor photography, and tungsten 
and white-flame-arc tricolour projection. 
Sometimes used with Nos. 29 and 61. 


47B 


FT-6 


Deep blue 


Standard narrow-cut tricolour blue 
filter for colour separation. Absorbs red, 
green, and much ultra-violet. 


48 




Deep blue 


Absorbs yellow and red strongly. 


48A 




Deep blue 


Similar to No. 48 but with slightly less 
ultra-violet absorption. 


49 




Dark blue 


Absorbs less blue than No. 48A. 


49B 




Dark blue 


Lower blue absorption than No. 49. 


SO 




Deep blue 


Monochromat. Absorbs red, green, and 
much ultra-violet. Photomicrography. 
Transmits mercury line at 436 nm and 
some at 398, 405 and 408 nm. 


52 




Light green 


Absorbs some blue and red. 


S3 




Green 


Absorbs strongly red and blue. 


54 


FT-4 


Deep green 


Contrast filter. Absorbs ultra-violet, 
blue and red, and some green. Photo- 
micrography. 


S5 




Green 


Stereo green filter used with No. 26. 


56 




Light green 


Absorbs some blue and red, useful for 
loosing green-brown lines when copy- 
ing graphs. 


57 




Green 


For "two-colour photography" (day- 
light). Often used when printing from 
'Eastman' Colour Negative Films. 


57A 




Green 


Absorbs red and some blue. 


58 


FT-8 


Green 


Standard green tricolour filter for colour 
separation and for contrast control in 
commercial photography. Absorbs 
ultra-violet, blue, and red. 


59 




Light green 


Contrast filter. Absorbs more blue than 
No. 57A but less yellow, red and green. 


59A 




Light green 


Absorbs less red and ultra-violet than 
No. 59. 


60 




Green 


For "two-colour photography" (tung- 
sten). 


61 




Deep green 


Narrow-cut tricolour green filter for 
colour separation. Absorbs ultra-violet, 
blue, and red. Used with No. 29 and 
47 for tricolour projection (tungsten), 
for colour-separation negatives from 
transparencies, and for visual estimation 
of colour negatives. 


64 




Light blue-green 


Some red absorption. 


65 




Blue-green 


Greater blue, green and red absorption 
than No. 64. 


6SA 




Blue-green 


More red absorption than No. 65, but 
less blue and green. 



FT- 1 



FILTER 



COLOUR 



REMARKS AND USE 



66 



70 



72A 



72B 
73 
74 
75 
f76 

*77 
77A 

78 

78AA 

78A 

78B 

78C 

79 



J80A 
J80B 
^80C 

J80D 



FT-4 



FT-4 
FT-4 
FT-4 
FT-4 
FT-4 

FT-3 
FT-3 



81 


CL-3 and 5 


8IA 


CL-3 and 5 


8IB 


CL-3 and 5 


8IC 


CL-3 and 5 


8ID 




81 EF CL-3and5 


82 


CL-3 and 5 


82A 


CL-3 and 5 


82B 


CL-3 and 5 


82C 


CL-3 and 5 



85 



CL-3 



Very light green 



Dark red 



Very deep orange- 
red 



Dark orange-yellow 
Dark yellow-green 
Dark green 
Dark blue-green 
Very deep violet 

Brownish yellow 
Brownish yellow 



Bluish 

Light blue 
Blue 
Blue 
Blue 

Blue 
Yellowish 




Absorbs some red, blue, and ultra-violet. 
Used as a contrast filter in microscopy 
and medical photography. 

Narrow-band monochromat. Used for 
making separation positives from colour 
negative films, and for tricolour printing 
on 'Ektacolor' Papers. 

Narrow-band monochromat. Used for 
simulating night effects in motion 
picture work. 



Monochromats. 



• Mercury-vapour-lamp monochromats. 



For photometric work. 



Used in photographic sensitometry to 
convert 2360 K to 5500 K. 

For daylight-type colour films with 
3200 K tungsten illumination. 

For daylight-type colour films with 
3400 K photolamps illumination. 

For daylight-type colour films with 
clear aluminium-filled flashbulbs (e.g., 
PF-60). 

For daylight-type colour films with clear 
zirconium-filled flashbulbs. 



Filters for light-balancing. Used to 

lower (81 Series) or raise (82 Series) 
l^the effective colour temperature of a 
"light-source by their use over a lens. 

Specific recommendations are given in 

Data Sheets for colour films. 



Conversion filter. For using colour films 
balanced for 3400 K illumination and 
Type L films in daylight, e.g., 
'Kodachrome' II Professional Film, Type A. 



* Available only as a glass filter. 

f Available only as a compound Fitter — 35+44. 

$ These correcting filters absorb some red and less green. With monochrome materials in tungsten, 
they correct the tendency for reds to reproduce too light. With 'Kodak' daylight-type colour films, 
they allow the use of artificial light (as described), but this procedure results in a considerable loss in 
effective film speed (see Data Sheets on specific colour films). 



FT- 1 



FILTER. 


COLOUR 


REMARKS AND USE 


85N3 


No. 85 + neutral 

density of 0.3 


^ 


85N6 


No. 85 + neutral 


Used instead of No. 85 to enable a 
f larger lens aperture to be used. 




density of 0.6 


8SN9 


No. 85 + neutral 


J 




density of 0.9 


8SB CL-3 


Amber 


Conversion filter. For using colour 
films balanced for 3200 K illumination 
for daylight exposures. 


8SBN3 


No. 85B + neutral 
density of 0.3 


^i 


85BN6 


No. 85B + neutral 


Used instead of No. 85B to enable a 




density of 0.6 


'"larger lens aperture to be used. 


85BN9 


No. 85B + neutral 






density of 0.9 


^ 


8SC 


Amber 


Sometimes preferred for exposing Type 
A or B (tungsten) colour materials in 
daylight, paler than No. 85 or 85B. 


86 
86A 


I 




86B 
86C 


fYellowish 


For photometric work. 


87 ^ 






ll C A ™ 


Visually opaque 


Filters for use in the near infra-red. 


89B J 






90 


Dark greyish amber 


Monochromatic viewing filter for visual 
use in daylight. Reduces the brightness 
of colours to assist judging of tone 
values. 


92 
93 
94 


Red 

Green 

Blue 


1 For use in the reflection densitometry 
[of colour papers (Status D). 


96 FT-2 


Neutral Density 


Generic number for a range of neutral 
density filters. 


97 


Dichroic red and 


Dichroic absorption filter, used to de- 




blue 


tect visually the red fluorescence of 
chlorophyll in green leaves. 


98 


Blue 


"1 Narrow-cut filters for making separa- 
tion positives from colour negative 


99 


Green 


ffilm, and for tricolour printing on 
J 'Ektacolor' Papers. 


102 


Yellow-green 


For converting the response characteris- 
tics of barrier-layer photocells to approx- 
imately the luminosity response of the 
eye. 


106 


Amber 


For converting the response of photo- 
cells, having type S4 sensitivity as used 
in some densitometers, to approximately 
the luminosity response of the eye. 



FT- 1 



AVAILABILITY 

With the exception of the 'Wratten' 18 A, 18B, 77, and 77 A Filters, which 
are available only in a special glass form and cannot be supplied in any 
other, and the 76, which is available only as a filter cemented between 
glasses of any of the undermentioned qualities or as two separate gelatin 
filters, i.e. Nos. 35 and 44, all filters are available in any of the following 
forms : 



KODAK 'Wratten' Gelatin Filters 

Supplied as squares of film which may easily be cut into circular form. 
They are available in four qualities : 

"Ordinary" quality : selected to be reasonably blemish-free and suitable 
for general photographic and scientific work. 

"Graphic Arts" quality : specially selected for colour-separation work 
where high optical quality is required. Kodak 'Wratten' Filter Colour 
Separation Sets are supplied in this quality when ordered as gelatin 
filters. 

"Photomechanical" quality : a somewhat limited range of very high 
optical quality filters, for use in multi-filtering techniques. It is important 
that orders for Colour Separation Sets in "Photomechanical" quality 
gelatin should carry a reference to this quality, otherwise "Graphic 
Arts" quality filters will be supplied. "Photomechanical" quality filters 
are prefixed PM, e.g., PM47B, to distinguish them from the other qualities. 
When ordering "Graphic Arts" or "Photomechanical" quality gelatin 
filters, it is important to specify the quality required, otherwise "Ordinary" 
quality filters will be supplied. 

Sizes: Most 'Wratten' Filters (except 18A, 18B, 77, and 77A which 
are available only as glass filters, and 76 which is only available as a 
compound filter comprising a No. 35 plus a 44) are available as gelatin 
sheets measuring up to approximately 280 x 280 mm. These are master 
sheets for cutting to size by the customer and 75-80% of the filter is 
blemish free. Most filters are available from stock in 50, 75, 100 and 
180 mm square sizes. 

"Photomechanical" quality filters are available only as 75 x 75 mm 
squares. 
Gelatin filters are not available in circular form. 
All sizes of gelatin filters have a thickness of 0.1 mm nominal. 

KODAK 'Wratten* Filters— Cemented 

These are gelatin filters cemented between glasses of the following 
qualities : 

"A" quality glass : specially selected optical flats of the highest quality 
which are surfaced with the same care and accuracy as that which is 
given to the preparation of lenses. This is recommended wherever 
the finest possible definition is required, and especially for use with 
long-focus or very wide-aperture lenses. 

9 FT-I 



"MP" quality glass : high-quality optical glass. Suitable for use with 
camera lenses of all focal lengths. 

" T" quality glass : good quality optical glass suitable for technical and 
scientific purposes, where the highest definition is not of prime importance. 

Sizes and Mounts : most 'Wratten' Filters of "MP" and "T" quality are 
available in three types of mount — 'Kodisk' Attachments, Kodak Rims, 
and Kodak 29.5 mm Screw-in Mounts (32 mm overall diameter). "A" 
quality filters are available in special metal rims. All qualities are available 
unmounted. 

The table below gives the rim sizes in which 'Wratten' Filters are 
available (to special order only), together with their overall diameters: 



'KODAK' RIM 


OVERALL DIAMETER 


'KODAK' RIM 
SIZE NO. 


OVERALL DIAMETER 


SIZE NO. 


millimetres 


millimetres 


206 
250 
320 
370 


20.6 
25.4 
30.2 
41.3 


420 
635 
825 


50.8 
63.5 
82.5 



All 'Wratten' Filters, except 18 A, 18B, 77, and 77 A, are available 
in Kodak 29.5 mm Screw-in Mounts (32 mm overall diameter) to fit 
'Retina' and 'Retinette' Cameras which have 32 mm diameter lens mounts. 

'Wratten' Filters cemented in "A", "MP" or "T" quality glass are 
available in sizes up to and including 150 mm diameter or 150 mm square. 
Some unmounted filters are normally stocked, but others have to be 
specially ordered. Other sizes are available subject to negotiation and 
special prices. 

Lateral dimensions, such as the diameter of a filter, are subject only 
to a negative tolerance; this ensures that a filter of a stated size will always 
fit a mount of corresponding specification. 

The table below gives details of the thickness of 'Wratten' Filters of all 
qualities : 



QUALITY 


SIZE 


THICKNESS 
Circles and Squares 


"A" 
"A" 

"MP" 
"T" 


Up to and including 40 mm 
All larger sizes 

Any size 
Any size 


7.5 mm ± 0.5 mm 
12.5 mm ± 1.5 mm 

7.5 mm + ° m 

— 1 mm 

7.5 mm + ? m 

— 1 mm 



FT- 1 



10 



Cemented filters in "MP" quality glass are available for certain motion- 
picture cameras that cannot accept the normal 50 mm, 75 mm and 100 mm 
square 'Wratten' Filters because they are too thick. "MP" quality 
filters are produced 50 mm, 75 mm and 100 mm square. Unless otherwise 
specified, they will be supplied in black metal frames with a maximum 
outside thickness of 7.5 mm. On request, 50 mm, 75 mm and 100 mm 
square filters will be supplied in black metal frames with a maximum 
outside thickness of 5 mm. All filters, except 18A, 18B, 77, and 77A, 
can be supplied in these forms. Filters in common use are stocked; 
others are available to special order. 

Requests for such filters and mounts to special order should be addressed 
to Kodak Limited, P.O. Box 66, Kodak House, Station Road, Hemel 
Hempstead, Herts., HP1 1JU. 

Compound filters 

In many cases, when a single filter does not have the desired transmission, 
the use of two filters together is indicated. Separate filters, either in 
gelatin form or cemented in "A", "MP" or "T" quality glass, are quite 
satisfactory when used in pairs, but under certain circumstances the extra 
air-to-glass surfaces may cause troublesome inter-reflections and loss of 
definition. These can be avoided by cementing the two gelatin films 
between glass as a single filter. 

Kodak Limited will cement combinations of filters to special order. 

CARE OF FILTERS 

In its simplest form, gelatin film, a filter requires considerable care in 
handling, though some protection is afforded by the special lacquer 
coating which is applied to all Kodak 'Wratten' Gelatin Filters. If it is 
used in front of or behind the lens in any form of carrier, it should be 
removed after use and placed, in clean paper, between the leaves of a book, 
where it will keep flat and dry. Moisture tends to cloud gelatin-film 
filters. Fingers are invariably moist and, to a certain extent, greasy; 
hence, in handling gelatin filters care should be exercised to hold them by 
one corner if they are square, or, better still, by the edges only. If it is 
necessary to cut the filter, it should be placed between two clean pieces 
of fairly stiff paper and cut with a pair of sharp scissors. The card 
packed with all Kodak 'Wratten' Gelatin Filters up to 100 mm square 
is marked with a series of circles as an aid to accurate cutting. 

Cemented filters should be treated with care equal to that accorded to 
lenses. They should be kept in their cases and on no account allowed to 
get damp or dirty. A filter should never be washed with water; if water 
comes into contact with the gelatin at the edges of the filter, it will cause 
it to swell and separate the glasses, allowing air to penetrate between the 
gelatin and the glass. Even if the swelling does not allow air to enter 
in this manner, the filter will be strained and the definition spoiled. 
Filters are clean when packed for distribution and, with reasonable 
care, they can be used indefinitely. If a filter gets so dirty that it cannot 
be cleaned simply by rubbing after breathing on it, a piece of lens- 
cleaning tissue should be moistened with a little 'Kodak' Lens Cleaner 
and gently rubbed over the surface of the filter. Care must be taken 

1 1 FT-I 



that the tissue is not wet enough for the fluid to run out and spread 
over the edge, as it may soften the compound with which filters are 
cemented and allow air to enter. Before attempting to clean a filter 
it should be seen that both the surface of the glass and the cleaning 
material are entirely free from grit, which may scratch the glass. 

Normal filters should never be subjected to undue heat. In photo- 
micrography or other work where a powerful light-source, such as an arc, 
is used, it should never be focused on the filter; temperatures above 
38°C (100°F) tend to soften the cement and cause the gelatin to contract. 
Where possible, in such circumstances, a heat-absorbing filter should be 
placed between the filter and the light-source. For such special purposes, 
filters can be specially produced using a cement which will withstand 
much higher temperatures; their supply is subject to negotiation. 

When used under tropical conditions, filters should be treated with the 
utmost care. They should be cleaned frequently to prevent damage by 
mould growth on the gelatin, or on the glass surfaces or edges. Dry, 
cool storage conditions are very desirable. The use of a desiccant, and 
a container which can be hermetically sealed, are recommended for this 
purpose. Further information for storage in the tropics may be found 
in Data Sheet GN-5. 

APPENDIX 

ALTERNATIVES TO DISCONTINUED 'WRATTEN' FILTERS 

The filters not now manufactured are listed in the following table which 
also shows which filters from the current range can in most cases be 
satisfactorily substituted. 



NOT NOW 


SUGGESTED 


NOT NOW 


SUGGESTED 


MANUFACTURED 


SUBSTITUTE 


MANUFACTURED 


SUBSTITUTE 


1 


IA 


49A 


47B 


2 


2B 


49C 


47B 


5 


8 


51 


CC30G 


7 


8 


58A 


58 


17* 


I8A 


62 


74 


23 


23A 


63 


61 


23B 


23A 


67 


none 


24A 


25 


68 


none 


27 


25 


69 


none 


27A 


25 


7IA 


29 


28 


25 


72 


72A 


30A 


none 


80 


80B 


32A 


none 


88 


88A 


39* 


none 


89 


70 


40A 


59 


89A 


70 


43 


38A 


101 


none 


47A 


47B 


105 


none 



* For ultra-violet work. 

Kodak and product names quoted thus, 'Wratten' , are trade marks 



Kodak Data Booklet 
FT- 1 



KODAK LIMITED 

Printed in England 
YI308 PDFT-I/XWPI2/4-73 




NEUTRAL-DENSITY FILTERS 

(KODAK 'WRATTEN' FILTERS No. 96) 

AND 'KODAK' PHOTOGRAPHIC STEP TABLETS 



NEUTRAL-density filters and step tablets (step wedges) are of use in many 
branches of optical work since they permit the reduction of light intensity 
in a known and definite manner. Those made by Kodak Limited are 
for use in the visible spectrum only; they are not intended for use in the 
ultra-violet or infra-red regions. They are made to have certain definite 
values of optical density, which are measured in terms of diffuse illum- 
ination upon approved types of photometers. 

Experience has shown that the transmission of a neutral-density filter 
depends to the extent of 2-3 per cent on the optical system with which it 
is used. This is the result of slight scattering of the transmitted light and 
inter-reflections. The effective density, therefore, may vary by a few 
per cent from the nominal value of any neutral-density filter. 

When a densitometer or other instrument, in which a filter or step tablet 
is to be used or measured, does not conform to the British Standard, then 
a correlation between the instument and the standard should be considered 
and tolerances agreed, otherwise discrepancies may occur. It is re- 
commended that for special work filters, or step tablets be calibrated by 
direct measurement under the conditions of use. 

Neutral-Density Filters ('Wratten' 96 Filter) 

These niters are available in thirteen densities as shown in the table 
below. For an extra charge, the filters are available individually calibrated. 
This range is available in gelatin or mounted in glass of any of the normally 
available qualities (see Data Sheet FT-1.) 



NAME 


DENSITY 


PERCENTAGE 
TRANSMISSION 


MULTIPLYING 
FACTOR 


INCREASE IN 

EXPOSURE 

(STOPS) 


NDO.I 


0.1 


80 


1* 


3" 


ND0.2 


0.2 


63 


l± 


3 


ND0.3 


0.3 


50 


2 


1 


ND0.4 


0.4 


40 


2-!- 


4 


ND0.5 


0.5 


32 


3 


If 


ND0.6 


0.6 


25 


4 


2 


ND0.7 


0.7 


20 


5 


2* 


ND0.8 


0.8 


16 


6 


2| 


ND0.9 


0.9 


13 


8 


3 


NDI.O 


1.0 


10 


10 


3± 


ND2.0 


2.0 


1 


100 


6| 


ND3.0 


3.0 


0.1 


1000 


10 


ND4.0 


4.0 


0.01 


10000 


I3± 



Issue G 



Kodak Data Sheet 
FT-2 



'Kodak' Photographic Step Tablets 

These step tablets (step wedges) consist of a series of steps of neutral 
photographic silver densities, with approximately equal density increments 
between steps. Nos. 2 and 3 include three colour patches to facilitate 
differentiation between colour-separation negatives. They are all normally 
supplied uncalibrated, but calibration is available at an extra charge. 



TABLET 


NOMINAL 
DENSITY 
INCRE- 
MENT 


STEP 
SIZE 


NUMBER 

OF 

STEPS 


NOMINAL 

DENSITY RANGE 

(INCLUDING 

BASE) 


TOTAL 

EFFECTIVE 

AREA 


OVERALL 
DIMENSIONS 


No. 1 
No. 2 
No. 3 


0.3 
0.15 
0.15 


3 mm 
5 mm 
10 mm 


II 

21 
21 


0.05 - 3.05 
0.05 - 3.05 
0.05 - 3.05 


2.2x3.3 cm 
2.2x 10.5cm 
2.2x21 cm 


2.2x7.5 cm 
2.2 x 14 cm 
2.2x25 cm 



Owing to the fact that the densities are of silver, and not dyed gelatin, 
the degree of scatter is higher than with neutral-density filters, and it is 
even more desirable that the steps should be calibrated only by direct 
measurement under the conditions of use. 

Similar strips of other sizes and density ranges may be supplied to 
special order, subject to the prior acceptance of a quotation; please address 
enquiries to Kodak Limited, P.O. Box 66, Kodak House, Station Road, 
Hemel Hempstead, Herts., providing the following information: — 

1 Overall size (total effective area) of the wedge. Each wedge can be 
made in any size up to a maximum of 18.3 X 23.5 cm. 

2 Direction of steps. If overall length or width is not greater than 18.3 cm 
steps can be parallel with long or short side. With lengths greater than 
18.3 cm, steps can only be parallel with short side. 

3 Total number of steps required. 

4 Width of steps, which are available in 1, 2, 3, 4, 5, 6, 7.5, 10, 15, 20, 24. 
and 30 millimetre widths. 

5 The density increments of the steps. Density ranges are available 
from fog level to 3.0 or according to the following: 

Fog level to density 0.5 Density 1.2 to density 2.0 

Density 0.5 to density 1.2 Density 2.0 to density 3.0 

Details of the tolerances available for these steps can be obtained from 
Kodak Limited upon request. Customers should state the required 
tolerance when submitting an order, or asking for a quotation. 

6 Total density range of whole wedge. 

7 Whether wedge is to be calibrated and where such calibrations are to 
be made on the steps. 

The above information should be used only as a guide : the production 
of a step wedge to a customer's own specification must be the subject of 
special negotiation. 

Kodak and Wratten are trade marks 



Kodak Data Sheet 
FT-2 



KODAK LIMITED 

Printed in Er.gland 
ri282PDFT-2/xWPI0/l0.72 



H^H I 



KODAK 'WRATTEN' FILTERS FOR 
SCIENTIFIC AND INDUSTRIAL PURPOSES 



The range of Kodak 'Wratten' Filters includes nearly one hundred 
different filters. Their absorption curves, transmission figures and other 
characteristics are given in detail in the book "Kodak 'Wratten' Filters", 
published by Kodak Limited, and for some filters in Data Sheets FT-8 
and FT-9. Details of the qualities and forms in which filters are available 
are given in Data Booklet FT-1. 

For the convenience of different classes of workers, a number of sets 
or groups of selected filters are available as follows : 

Technical Set of 8 Filters 

This set is designed to provide for much of the work arising in technical 
photography, and as such represents a selection of the most generally 
used filters in the 'Wratten' range. It consists of the following: Nos. 3, 
8, 11, 15, 25, 29, 47B, 58; they are all cemented in "T" quality glass. 

Laboratory Set of 50 Filters 

The laboratory set of 50 filters has been selected for use in laboratories, 
schools, universities, research stations and other places where the behaviour 
of light is demonstrated, observed or employed. By the proper choice 
of filters or combinations of filters, various parts of the spectrum can be 
absorbed or suppressed to suit most requirements. The set is supplied 
complete in a fitted mahogany case. The filters comprising the set are : 
Nos. 1A, 2B, 3, 8, 11, 12, 15, 18A, 18B, 22, 23A, 25, 29, 30, 32, 35, 36, 
38, 44, 45, 47B, 50, 58, 59, 61, 66, 70, 72B, 73, 74, 75, 76, 77, 78A, 78C, 
81, 81C, 82, 85, 85B, 86A, 86C, 87, 88A, 96 ND 0.1, 96 ND 0.2, 
96 ND 0.5, 96 ND 0.8, CC20Y, CC05M; they are all cemented in "T" 
quality glass. 

Laboratory Set of 24 Filters 

For those who do not require the full set of 50 filters, this smaller set is 
available. The set is supplied complete in a fitted mahogany case and 
includes the following filters: Nos. 2B, 8, 11, 12, 15, 22, 25, 29, 32, 35, 
44, 45, 47B, 50, 58, 59, 61, 70, 72B, 73, 74, 75, 76, 88A; "T" quality glass. 

Microscopy Set of 9 Filters 

These niters have been selected to enable the photomicrographer to 
control accurately the contrast of his photomicrographs. They are chosen 
for their purity, brightness of colour and their sharp absorption character- 
istics. In addition to their use as single filters, they can be used in 
pairs with which the spectrum can be divided into substantially mono- 
chromatic portions. 

Issue E Kodak Data Sheet 

FT-3 



The set comprises the following filters:— Nos. 11, 15, 22, 25, 29, 35, 
45, 47B, 58. 

These filters, mounted in frames 50 X 50 mm, should be used between 
the light-source and the sub-stage condenser; because of this they are 
available only as Kodak 'Wratten' Filters in "T" quality glass. 

When selecting a filter, care must always be taken that too much con- 
trast is not obtained, or the result will be a choking of the shadows and 
loss of detail. 

The more nearly monochromatic the illumination, the sharper will be 
the image from an achromatic objective. The following filters within this 
set are especially useful with achromats since they transmit suitable green 
light (given in order of decreasing breadth of transmission band) : — Nos. 
11,58,58+15,61,15+45. 

The spherical aberration of achromatic objectives is best corrected for 
the region of the spectrum transmitted by No. 58+15 filters. Hence, 
when the specimen is colourless, as it frequently is in metallography, the 
illumination is restricted by these filters in order to use achromatic ob- 
jectives most efficiently. Apochromatic objectives also give better 
definition when the illumination is restricted by a No. 98 blue filter. A 
considerable choice of dominant wavelengths throughout the spectrum 
is available by the use of these filters either singly or in pairs. 

Filters Dom. Wavelength Colour 

25 + 45 445 nm Violet 

47B + 45 460 nm Blue 

58 +45 510 nm Bluish-green 

15 + 45 525 nm Pure green 

58 +15 540 nm Yellowish-green 

58 + 22 575 nm Greenish-yellow 

25 615 nm Red 

29 630 nm Deep red 

25 + 35 670 nm Very deep red 

Monochromatic Set of 7 Filters 

The filters in this set are cemented in "T" quality glass, each filter 
transmitting a spectral region about 55 nm in width. 
70 Very deep red 75 Very deep blue-green 

72B Very deep orange-red 76 Very deep violet 

73 Very deep yellow-green 88A Visually opaque (infra-red) 

74 Very deep green 

Transmission figures for these filters (with the exception of the 88A, the 
figures for which are given in Data Sheet FT-9), and of certain mono- 
chromatic combinations, are given in Data Sheet FT-4. 

Mercury Monochromatic Set of 3 Filters 

These filters, Nos. 22, 50, and 74, as their name implies, are designed 
for the isolation of certain of the mercury lines; they are cemented in 
"T" quality glass. The No. 22 (yellow monochromat) transmits the 
yellow lines of 577 and 579 nm and all longer wavelengths. The No. 50 
(violet monochromat) transmits the blue-violet line of 436 nm, and to a 

FT-3 2 



lesser extent the ultra-violet line at 398 nm, and the deep-violet line at 
408 nm. The No. 74 filter (green monochromat) transmits approxi- 
mately 10 per cent of the green line at 546 nm and about 0.2 per cent of 
the yellow lines. 

The chief lines of mercury-vapour illumination occur at these positions : 
Yellow 577 and 579 nm Deep violet 405 and 408 nm 

Green 546 nm Ultra-violet 365 and 398 nm 

Blue-violet 436 nm 

Special Mercury Monochromatic Filters 

In addition to the standard set of mercury monochromats, four special 
filters, the 'Wratten' Nos. 18A, 18B, 77 and 77A are available. 

The No. 77 is designed to isolate the green line at 546 nm, but to 
suppress the nearby band of yellow at 577 and 579 nm; it transmits 
74 per cent of the green line and about 1 per cent of the yellow lines. 

Where the yellow lines must be suppressed still further, the No. 77A 
is recommended. This filter transmits approximately 68 per cent of the 
green line and has only a neglible transmission at 577 nm. Where the 
red lines of a quartz lamp are objectionable and must be eliminated, a 
No. 58 filter should be used in combination with either a No. 77 or a 
No. 77A. 

Further information concerning the characteristics of the 18A and 
18B niters may be obtained from Data Sheet FT-9. 



Colour-Separation Sets 

Details of two of these sets are given in Data Sheet FT-6. Other sets 
may be supplied as required. 

Filters for Photometric Use— Nos. 78A, 78C, 86A, 86C 

When light-sources of different colour temperatures are compared by 
means of a photometer, the colour difference introduces difficulty in 
making an accurate balance. This difficulty can be eliminated, or at 
least lessened considerably, if one of these filters is placed on one side 
of the photometer head. The difference in colour between the two 
parts of the photometric field will then be eliminated, or reduced to 
such an extent that it no longer interferes with the precise judgement of 
brightness equality. The transmission of the filter for light of the 
spectral quality which is incident upon it in the photometer must, of 
course, be determined. The calibration can, however, be made by taking 
a sufficiently large number of observations to obtain the desired precision. 

In present-day photometric practice, the standard of luminous in- 
tensity is almost invariably an electric incandescent lamp of standardized 
candle power. In order that this standard shall have a satisfactorily long 
life, it is necessary that it be operated at a relatively low filament tempera- 
ture. This means that the light emitted by such a standard is usually 

3 FT-3 



much more yellow than the illumination with which it is to be compared, 
which may come from commercial tungsten incandescent lamps operating 
at much higher temperatures, arc lamps of various kinds, or from natural 
sources, such as the sun or sky. 

Two series of filters for photometric use are provided. The No. 78 
series consists of bluish filters designed, in general, to be placed on the 
standard-lamp side of the photometer or illuminator. The No. 86 series 
consists of yellowish filters, designed to be placed on the test or comparison 
side of the photometric instrument. 

In the following tables, the colour differences which can be compensated 
for by these filters are shown in terms of colour-temperature differences. 
Standard lamps are normally operated at a colour temperature of approxi- 
mately 2360 K. This value, therefore, is taken as the reference point 
in listing the colour difference for which each filter (or filter combination) 
will compensate. 



No. 78 SERIES (BLUISH) 
For increasing colour temperature 



No. 86 SERIES (YELLOWISH) 
For decreasing colour temperature 



78A+78A raises 2360 K to 5000 K 
78A „ 2360 K to 3200 K 

78C+78C „ 2360 K to 2666 K 
78C „ 2360 K to 2500 K 



86A+86A reduces 5000 K to 2360 K 
86A „ 3200 K to 2360 K 

86C+86C „ 2666 K to 2360 K 
86C „ 2500 K to 2360 K 



NOTE: These filters are subject to the limitations of commercial pro- 
duction, though the tolerances have been reduced to the minimum prac- 
tical values: if they are to be used under circumstances where high 
precision is required, they should be individually calibrated. 

It should be emphasized that these filters are designed primarily for 
visual use to reduce the colour differences between illuminants operating 
at different colour temperature. They can, however, be used to introduce 
slight colour correction to the light-source when exposing colour films, 
provided that their limitations are realised and allowed for. 



Details of further sets of filters used in colour photography — ' Wratten' 
Filters for Light Balancing and 'Kodak' Colour Compensating and Colour 
Printing Filters — are given in Data Sheet CL-3. 



Kodak and Wratten are trade marks 



Kodak Data Sheet 
FT-3 



KODAK LIMITED LONDON 

PDFT-3/xWPI 1/9-71 



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MONOGHROMATS AND MONOCHROMATIC 

COMBINATIONS FROM THE RANGE OF 

KODAK 'WRATTEN' FILTERS 



TABLE OF TRANSMITTANCE 

VALUES AT VARIOUS 

WAVELENGTHS 



Issue B 



Kodak Data Sheet 
FT-4 



Kodak and Wratten are trade marks 



Kodak Data Sheet 
FT-4 



KODAK LIMITED 

Printed in England 
YI309 PDFT-4/xWP 1 2/4-73 




LIQUID FILTERS FOR THE ISOLATION 
OF CERTAIN LINES OF THE MERCURY 
DISCHARGE LAMP 



The following tables are taken from Chemical Aspects of Light by 
E. J. Bowen (Clarendon Press), by permission of the author and pub- 
lishers. Table I lists suitable stock solutions, and Table II on the next 
page gives recommendations for their use in various combinations. 



TABLE I 



STOCK SOLUTIONS 



Note : Nickel, cobalt and copper solutions must be free from traces of iron salts. 
'Analar' standard have been found suitable (B.D.H., and Hopkin & Williams Ltd). 



A 

B 

C 
D 

E 

G 

H 

J 
K 

L 

M 
N 

P 
R 

S 

T 
U 
V 

w 



Copper chloride, CuCI 2 .2H 2 C I kilogramme in I litre water. 

Calcium chloride, 3 molar, i.e., 333 grammes anhydrous salt made up to 

I litre solution with water. 

Potassium dichromate, IS grammes in 200 ml water. 
Didymium (or neodymium) nitrate, 30 grammes made up to 100 ml 
solution with water. 

Copper sulphate, CuS0 4 .5H 2 0, 25 grammes, ammonium hydroxide 
(d = 0-88) 300 ml made up to I litre with water. 

Copper sulphate, CuS0 4 .5H 2 0, 125 grammes made up to I litre with 
water. 

Copper nitrate, Cu(N0 3 ) 2 .6H 2 0, 200 grammes in 100 ml water. 
Iodine, 0.75 gramme in 100 ml carbon tetrachloride. 
Sodium nitrite, NaN0 2 , 75 grammes in 100 ml water. 
Nickel sulphate, NiS0 4 .6-7H 2 0, 145 grammes, cobalt sulphate, 
CoS0 4 .7H 2 0, 41.5 grammes, made up to I litre with water. 
Potassium hydrogen phthalate, 5 grammes in I litre water. 
Copper sulphate, CuS0 4 .5H 2 0, 15 grammes in I litre water. 
Potassium iodide, KI, 1.7 grammes in I litre water. 
Potassium iodide 0.14 gramme, iodine 0-1 gramme in I litre water. 
Cobalt chloride, CoCI 2 .6H 2 0, 30 grammes in 100 ml of 3M calcium 
chloride solution. 

Nickel sulphate, NiS0 4 .7H 2 0, 82 grammes in 100 ml of 0-25M copper 
sulphate solution. 

220 grammes NiS0 4 .7H 2 + 200 grammes CoS0 4 .7H 2 in I kilogramme 
solution. 

120 grammes NiS0 4 .7H 2 + 23.5 grammes (NH 4 ) 2 S0 4 + 82.8 grammes 

aq. NH 3 (d = 0.925) in I kilogramme solution. 

Gaseous chlorine at I atmosphere in a fused silica cell 3 cm deep. 



Solutions E, M, P, and R should be frequently renewed. 



Kodak Data Sheet 
FT-5 



TABLE II USE OF STOCK SOLUTIONS 


Note : Glass cells may be used for the visible region, and for the ultra-violet region down to the 
365-6 nm line ; silica must be used for the remainder of the ultra-violet region. 


Wavelength 

nm 


Filter Combinations 


578, 577 


10 ml A with 90 ml B, 1 cm combined with either C, 2 cm or 
Corning glass 344, 3.4 mm 


546 


20 ml A with 80 ml B, 1 cm combined with either D, 1 cm or 
Corning glass 512, 5 mm 


436, 435 


E, 2 cm, combined with K, 1 cm or H, 2 cm combined with K, 
1 cm (transmits a little 546 nm) 


405 


H, 2 cm combined with J, 1 cm 


366, 365 


G, 1 cm combined with Chance's black u.v. glass, 2-3 mm 


334-300 


S, 1 cm, combined with T, 1 cm 


334-289 


L, 10 cm, combined with N, 1 cm or U, 2.5 cm, combined with V, 
2 cm, and N, 1 cm 


313,312 


L, 10 cm, combined with M, 1 cm or U, 2.5 cm, combined with V, 
2 cm and M, 1 cm 


265 


L, 10 cm, combined with P, 1 cm and withW, 3 cm, or U, 2.5 cm, 
combined with V, 2 cm, and with P, 1 cm, and W, 3 cm 


265, 254 


L, 10 cm, combined with W, 3 cm, or U, 2.5 cm, combined with 
V, 2 cm, and W, 3 cm 


254 


L, 10 cm, combined with R, 1 cm, and with W, 3 cm, or U, 2.5 cm, 
combined with V, 2 cm, and with R, 1 cm, and W, 3 cm 



A convenient means of obtaining a concentrated beam of light with those 
filters which include a 10 cm path in solution L is to place this solution in 
a round flask of 10 cm diameter (and 500 ml capacity) very near to the 
lamp, followed by the other filters. The reaction cell should be placed 
behind a diaphragm about 24 cm from the lamp. 



Kodak is a trade mark 



Kodak Data Sheet 
FT-5 



KODAK LIMITED LONDON 



PDFT-5/r2WP2/2-70 



KODAK 'WRATTEN' FILTER 
COLOUR-SEPARATION SETS 



The following table indicates, with crosses, the constitution of each of 
the five sets and also the colours of the individual filters. 









'WRATTEN' 


FILTERS 








SET 
No. 


9 


25 


29 


33 


47B 


58 


61 


85B 


Medium 




Deef> 


Medium 


Deep 




Deep 






Yellow 


Red 


Red 


Magenta 


Blue 


Green 


Green 


Amber 


1 




X 






X 


X 






2 


X 


X 






X 


X 






3 






X 




X 




X 




4 






X 




X 




X 


X 


5 






X 


X 


X 


X 




X 



Spectrophotometric absorption curves 

Superimposed curves for five colour-separation filters are shown in 
the two graphs below. 



'Wratten' No. 25 
'Wratten' No. 47B 
'Wratten' No. 58 




100 300 4(10 500 400 700 

Wave-length mu. 

47B 61 29 



'Wratten' No. 29 
'Wratten' No. 47B 
'Wratten' No. 61 




Issue D 



400 500 


600 700 


Wave-length n\\x 






Kodak Data Sheet 




FT-6 



Available forms 

Gelatin film or, to special order, cemented in "A", "MP", or "T" quality 
glass, in all common sizes — see Data Sheet FT-1. 

When sets are ordered in gelatin form, a specially selected quality — 
designated "Graphic Arts" quality — is supplied. An even higher optical 
quality gelatin set is also available, "Photomechanical" quality, especially 
for use in multi-filtering techniques. 
Transmission tables 

The following tables give wave-length transmission figures for seven 
of the eight filters; these figures are not given for the eighth, the 85B, 
which is a conversion filter. In addition, are given the total visual 
transmission factors, expressed as percentages, for the standard illuminants 
'A' (2854 K), and 'C' (mixture of sunlight and skylight and approximately 
similar to the light from a 6500 K source), as adopted by the Commission 
Internationale de l'Eclairage (CLE.). 



WAVE-LENGTH 


PERCENTAGE TRANSMISSION 


mjx 


9 


25 


29 


33 


47B 


58 


61 


400 











0.85 


16.0 


, 





10 


— 


— 


— 


0.71 


29.5 








20 


— 


— 


— 


1.17 


43.6 








30 


— 


— 


— 


1.69 


50.0 








40 


— 


— 


— 


5.36 


47.2 








450 


— 


— 


— 


14.3 


56.0 








60 


— 


— 


— 


12.4 


25.0 








70 


1.78 


— 


— 


5.0 


13.2 


0.23 





80 


8.31 








0.50 


4.5 


1.38 


0.33 


90 


20.7 


— 


— 


— 


1.3 


4.90 


4.0 


500 


34.5 











0.17 


17.7 


16.6 


10 


48.8 


— 


— 


— 


— 


38.8 


32.3 


20 


62.0 


— 





— 





52.2 


40.0 


30 


76.0 














53.6 


39.6 


40 


83.8 














47.6 


34.5 


550 


87.0 











. — 


38.4 


26.3 


60 


88.3 














27.8 


17.3 


70 


88.8 














17.4 


9.70 


80 


89.1 














9.0 


4.40 


90 


89.3 


12.6 











3.50 


1.66 


600 


89.5 


50.0 











1.50 


0.38 


10 


89.7 


75.0 


10.0 


0.80 





0.41 





20 


89.8 


82.6 


45.3 


24.9 











30 


89.9 


85.5 


71.4 


60.8 





— 





40 


90.0 


86.7 


82.7 


78.0 











650 


90.1 


87.6 


86.6 


85.0 











60 


90.1 


88.2 


88.4 


87.5 











70 


90.2 


88.5 


89.4 


88.7 











80 


90.2 


89.0 


90.0 


89.4 











90 


90.3 


89.3 


90.3 


89.8 











700 


90.3 


89.5 


90.4 


90.0 


0.53 


— 


— 


Total 
















Transmission 
















Standard 'A' 
















(2854 K.) 


82.4 


22.5 


11.0 


8.9 


0.2 


19.8 


13.7 


Standard 'C 
















(6500 K) 


76.6 


14.0 


6.3 


5.2 


0.8 


23.7 


16.8 



Kodak and Wratten are trade marks 



Kodak Data Sheet 
FT-6 



KODAK LIMITED LONDON 

PDFT-6/xWP 1 1/9-71 



'KODAK' SAFELIGHT FILTERS 



The term "safelight" is used to describe the type of darkroom illumination 
that does not fog light-sensitive material under normal handling and 
processing conditions. Since photographic materials vary in sensitivity 
to different wavelengths of radiation, a safelight filter should be chosen 
such that the greater part of the radiation it transmits, lies outside the 
sensitivity range of the emulsion of the material to be used. However, 
since most emulsions have some sensitivity to wavelengths outside their 
normal range, it is necessary to keep exposure to safelighting to a minimum. 
For suitable safelight tests see below. 

Always use the safelight filter recommended for the product and observe 
the instructions for the correct lamp wattage and the distance of the lamp 
from the material (see Data Sheet RF-2). Do not use coloured lamps as 
improvised safelights as they will usually transmit some radiation which 
will fog a photographic emulsion. 

Change safelight filters periodically, and record the date of the replace- 
ment on a small sticker placed on the safelight. Remember to change 
the lamps at intervals as they discolour and so reduce the amount of 
illumination. 

The curves overleaf show the parts of the visible spectrum transmitted 
by the range of 'Kodak' Safelight Filters. 

SAFELIGHT TESTS 

Continuous-tone materials of normal tone range (except X-ray materials) 

In general, photographic products are more sensitive to post-exposure 
safelight fogging than pre-exposure fogging, so the post-exposure test is 
the more critical. A typical post-exposure safelight test is described below. 

Take a piece of the material of a reasonably large size or length. In 
total darkness, load the material into the exposing apparatus or place in 
the exposing position. Give a short exposure to the normal lighting 
source for the material so that it is lightly fogged (density about 0.5). 

Still in total darkness, unload the material and cover a portion of it with 
opaque card. Place six small coins along the remainder of the material 
and switch on the safelamp(s) to be tested. After J minute, move the 
card to cover up the nearest coin. After a total time of \ minute, cover 
up the next coin. Continue to cover further coins at 1, 2, 4 and 8 minutes. 

Switch off the safelamps and (in total darkness) process the material in 
the normal way. 

Examine the material carefully to see which outlines are visible in their 
respective steps. These indicate unacceptably long exposures to the 
safelighting. The next step to those visible, indicates the longest time 
the material can be exposed to the safelighting prior to processing. 

Continued on back of sheet 



Issue B 



Kodak Data Sheet 
FT-7 



Safelight filters fade after a period of use and should be tested from 
time to time. 

X-ray films 

See Data Sheet XR-6. 



Kodak is a trade mark 



Kodak Data Sheet 
FT-7 



KODAK LIMITED LONDON 

PDFT-7/xWPIO/IO-7l 



00 Light yellow 



nnr 




















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400 500 600 700 

Wavelength (nm) 



400 500 600 700 

Wavelength (nm) 




500 600 

Wavelength (nm) 



I A Light red 


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400 500 



600 
Wavelength (nm) 



2 Dark red 




3 Dark 



green 




500 600 700 

Wavelength (nm) 



500 600 

Wavelength (nm) 



FT-7 



OD Brown 




500 600 

Wavelength (nm) 



6BR Light brown 

















IBHH 


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500 600 

Wavelength (nm) 



Dark amber 




500 600 

Wavelength (nm) 




400 500 



600 
Wavelength (nm) 



1 2 Light 



green 




400 500 600 700 

Wavelength (nm) 



FT-7 



KODAK 'WRATTEN' FILTERS 

Nos. 8(K2), 9(K3), 11 (XI), 15(6), 25 

SPECTRAL CHARACTERISTICS 

No. 8 (K2) Yellow. Absorbs ultra-violet and some blue. 

No. 9 (K3) Medium yellow. Absorbs ultra-violet and some blue. 

No. II (XI) Light yellow-green. Absorbs ultra-violet, some blue, and 
some red. 

No. 1 5 (G) Very deep yellow. Absorbs ultra-violet, blue, and a little 
green. 

No. 25 Red. Absorbs ultra-violet, blue, and green. 



USES 

No. 8 Correction filter for outdoor use: This filter reproduces colours 

(K.2) in their correct monochromatic relationship when used in 

daylight with 'Kodak 5 panchromatic materials. It is recom- 
mended also for use with 'Kodak' orthochromatic materials. 
Its principal uses are (1) darkening a blue sky to obtain cloud 
effects; (2) photographing through distance haze; (3) photo- 
graphing foliage and grass to render it lighter than without a 
filter; (4) photographing gardens; (5) for any scenery (distant 
or close) where colours, especially greens, yellows and reds, 
are predominant; and (6) in much outdoor commercial work, 
such as architecture. 

Contrast effects in the studio: This filter should be used in the 
studio when a light rendering of red and yellow objects is 
required, but not so light a rendering as is given by the 
'Wratten' 15 filter. 

No. 9 Contrast filter: This filter is slightly more dense than the 

(K.3) 8 filter and may be used for the same purposes. It gives 

a slightly "over-correct" rendering when used for normal 
outdoor photography. It may be used with both panchro- 
matic and orthochromatic materials. 

No. 1 1 Correction filter with tungsten lighting: This filter reproduces 

(XI) colours in their correct monochromatic relationship when 

used in tungsten lighting with 'Kodak' panchromatic 
materials. It is not recommended for use with orthochro- 
matic materials. Should the first result on such panchromatic 
materials as 'Tri-X' film, as taken in tungsten light without 
a filter, need improvement in rendering, this filter should 

Issue D Kodak Data Sheet 

FT-8 



be tried before any of the contrast niters, unless the need for 
the latter is definitely indicated. 

Outdoor portraits: This filter also produces pleasing flesh tone 
and background rendering in close-up outdoor portraits 
against the sky, when the use of a yellow filter might result in 
a chalky rendering of flesh tones. 

No. 15 This filter may be used with both panchromatic and ortho- 

(G) chromatic materials. 

Sky and other outdoor contrast effects: Renders a blue sky 
darker than is correct in order to emphasize a foreground 
subject — a building, for example; in marine scenes, darkens 
the water surface. The bluer the water appears, the more 
pronounced is the effect. Red and yellow subjects, such as 
flowers, are rendered lighter than the eye sees them. Blue 
subjects are rendered darker. 

Texture rendering outdoors: Produces an enhanced rendering 
of texture in sunlit outdoor subjects photographed under a 
blue sky, e.g., with such subjects as architectural stone, sand, 
fabrics, etc. 

Haze penetration: Penetrates distant haze to a greater extent 
than the eye. 

Telephoto lenses: Many distant scenes taken with telephoto or 
other long-focus lenses are improved by this filter. Telephoto 
pictures taken without filters tend to lack contrast. With 
lenses longer than 10 inches in focal length, gelatin film 
or 'A' quality glass should be used. 

Contrast uses in the laboratory: Produces contrast between the 
blue parts and the yellow, brown, orange or red parts of a 
subject, such as stained biological slides, and renders detail in 
any yellow, brown or orange subject. 

No. 25 This filter should be used only with panchromatic or infra- 

red materials. 

Sky and other outdoor contrast effects: Applications outdoors 
are similar to those of the 15 filter, but the effects are 
more pronounced. The 25 filter renders red and yellow 
objects lighter, blue objects darker, and enhances the texture 
of outdoor subjects. It renders blue skies dark, which is 
helpful in producing spectacular photographs of buildings 
and so forth. This filter likewise penetrates aerial haze; green 
foliage, however, will be darkened. Slight under-exposure 
through a 25 filter produces moonlight effects. This filter 
renders sunsets spectacular, for the red and yellow parts are 
reproduced bright against blue sky and grey clouds. 

Contrast effects in the studio and laboratory: This filter is most 
useful in producing contrast — for example, in photographing 
a blue-print to show the lines light against a dark background. 

FT-8 2 



It renders blue and green as dark; and yellow, orange and red 

as very light. This filter is also valuable in reproducing detail 

in brown or red subjects, such as mahogany furniture and 

stained biological slides. 

Infra-red photography : This filter can also be used with 

infra-red materials. 

Colour-separation negatives: The No. 25 is the red filter of the 

standard tri-colour set (see Data Sheet FT-6). 



AVAILABLE FORMS 

These filters are available in any of the following forms : 

Kodak 'Wratten' Gelatin Filters 

Supplied as squares of film which may easily be cut into discs, etc. 
All sizes have a thickness of 0.1 ±0.01 mm. 

Kodak 'Wratten' Filters 

These are gelatin filters cemented between glasses of the following 
qualities : 

"A" quality glass — specially selected optical flats of the highest quality 
which are surfaced with the same care and accuracy as that which is 
given to the preparation of lenses. This is recommended wherever the 
finest possible definition is required, and especially for use with long- 
focus or very wide-aperture lenses. 

"MP" quality glass — high optical quality; suitable for use with all focal 
lengths of camera lenses. 

"T" quality glass — good-quality optical glass suitable for technical and 
scientific purposes, where the highest definition is not of prime importance. 

Further details of all these forms are given in Data Booklet FT-1. 



ABSORPTION CURVES 



No. 8 
(K2) 



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_ 











FT-8 



No. 9 
(K3) 























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.- 





















No. II 
(XI) 





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No. 15 
(G) 





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No. 25 




FT-8 



TRANSMISSION TABLES 

The following tables give wavelength :transmission figures for the 
five filters. In addition are given the total visual transmission factors, 
expressed as percentages, for the standard illuminants 'A' (2854 K), and 
'C (mixture of sunlight and sky light and approximately similar to the 
light from a 6500 K source), as adopted by the Commission Internationale 
de l'Eclairage (CLE.). 





PERCENTAGE TRANSMISSION 


WAVELENGTH 




Filter Numbe 


r 




nm 














8 


9 


II 


15 


25 


400 
10 
20 


— 


— 


— 


— 


— 








0.16 








30 


— 


— 


0.29 


— 


— 


40 


— 


— 


0.56 


— 


— 


450 


— 


— 


1.32 


— 


— 


60 


0.25 


— 


4.0 


— 


— 


70 


5.5 


1.78 


12.0 


— 


— 


80 


19.0 


8.31 


26.0 


— 


— 


90 


41.0 


20.7 


43.7 


— 


— 


500 


63.5 


34.5 


55.0 


— 


— 


10 


78.0 


48.8 


60.0 


1.0 


— 


20 


84.1 


62.0 


60.2 


16.0 


— 


30 


86.5 


76.0 


57.8 


52.1 


— 


40 


87.7 


83.8 


54.2 


75.0 


— 


550 


88.4 


87.0 


50.0 


84.3 


— 


60 


88.8 


88.3 


44.8 


87.5 


— 


70 


89.2 


88.8 


38.9 


88.7 


— 


80 


89.5 


89.1 


33.1 


89.3 


— 


90 


89.8 


89.3 


27.6 


89.7 


12.6 


600 


90.1 


89.5 


22.7 


90.0 


50.0 


10 


90.3 


89.7 


19.0 


90.1 


75.0 


20 


90.5 


89.8 


14.9 


90.2 


82.6 


30 


90.7 


89.9 


11.4 


90.3 


85.5 


40 


90.9 


90.0 


9.1 


90.4 


86.7 


650 


91.0 


90.1 


8.05 


90.5 


87.6 


60 


91.1 


90.1 


7-5 


90.6 


88.2 


70 


91.2 


90.2 


7.05 


90.6 


88.5 


80 


91.3 


90.2 


6.5 


90.7 


89.0 


90 


91.4 


90.3 


6.1 


90.7 


89.3 


700 


91.5 


90.3 


6.2 


90.8 


89.5 


Total Transmission 












CLE. Standard 'A' 












(2854 K) 


86.6 


82.4 


36.3 


75.5 


22.5 


C.I.E.Standard'C 












(6500 K) 


82.7 


76.6 


40.2 


66.6 


14.0 



FT-8 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

WRATTEN 

TRI-X 



Kodak Data Sheet KODAK LIMITED LONDON 

FT-8 

PDFT-8/xWP I 1/9-71 



KODAK 'WRATTEN' ULTRA-VIOLET FILTERS 

Nos.2A,2B,2E,18A,18B 

AND INFRA-RED FILTERS Nos. 87, 87C, 88A, 89B 



SPECTRAL CHARACTERISTICS AND USES 

No. 2A Very faint yellow. Absorbs radiant energy below 405 nm. 
Similar to No. 2B but absorbs slightly more ultra-violet 
radiation. 

No. 2B Very faint yellow. This filter absorbs ultra-violet radiation 
strongly (below 390 nm) and transmits a large percentage of 
all visible radiation. It is recommended for use with black- 
and-white materials when used at high altitudes or on other 
occasions when the elimination of ultra-violet radiation is 
required, as in the fluorescence method of ultra-violet photo- 
graphy. 

No. 2E Very faint yellow. Similar to No. 2B but absorbs more 
ultra-violet radiation (below 415 nm). 

No. I8A Visually opaque. Transmits ultra-violet radiation and 
absorbs all visible radiation except a very small amount of 
extreme red. Also transmits some infra-red. Recom- 
mended for the direct method of ultra-violet photography 
and for other ultra-violet work. Having peaks of trans- 
mission at approximately 360 nm and 740 nm, it is particu- 
larly suitable when using the 365 nm mercury line, or 
infra-red radiation. 

No. I8B Very deep violet. This filter is generally similar to the 
No. 18A, but has wider transmission bands. Transmits 
ultra-violet radiation down to the 254 nm mercury line, and 
infra-red radiation. It absorbs all visible radiation except 
some extreme blue and some extreme red. 

No. 87 Transmits infra-red radiation and absorbs visible radiation. 
This is a special infra-red filter recommended for use with 
infra-red sensitized materials under a variety of technical 
conditions. 

No. 87C Transmits infra-red radiation and absorbs visible radiation. 
It has a narrower transmission band than the No. 87. 

No. 88 A Transmits infra-red radiation and absorbs visible radiation. 
It has a wider transmission band than the No. 87. This 
filter is recommended for all general-purpose infra-red 
work, including special-effect outdoor photography. 

No. 89B Transmits infra-red radiation and absorbs visible radiation. 
It has an even wider transmission band than the No. 88A. 

Issue E Kodak Data Sheet 

FT-9 



AVAILABLE FORMS 

The Nos. 18A and 18B filters are available only in a special glass and 
cannot be supplied in any other form. 

The Nos. 2A, 2B, 2E, 87, 87C, 88A and 89B filters are available in any of 
the following forms : 

KODAK 'Wratten' Gelatin Filters 

Supplied as squares of film which may easily be cut into discs, etc. 
All sizes have a thickness of 0.1 ±0.01 mm. 

KODAK 'Wratten' Filters 

These are gelatin filters cemented between glasses of the following 
qualities : 

"A" quality glass : specially selected optical flats of the highest quality 
which are surfaced with the same care and accuracy as that which is 
given to the preparation of lenses. This is recommended whenever the 
finest possible definition is required, and especially for use with long- 
focus or very wide-aperture lenses. 

"MP" quality glass: high optical quality; suitable for use with all focal 
lengths of camera lenses. 

"T" quality glass : good-quality optical glass suitable for technical and 
scientific purposes, where the highest definition is not of prime importance. 

Further details of all these forms are given in Data Booklet FT-1. 



ABSORPTION CURVES 



No. 2A 



400 500 

WAVELENGTH nm 



















































































































































































- 
























II 


























I 


















































































































































II II 

























































FT-9 



No. 2B 



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400 500 600 

WAVELENGTH nm 



No. 2E 





























































































































































































































































































1 




























1 


























































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400 500 

WAVELENGTH nm 













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200 300 400 500 600 700 800 900 

WAVELENGTH nm 



No. I8A 



FT-9 





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■■ 


















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■■■■■*_ 






















■■ 
















mmum 


■■■■■■L 




















i 


!H. 












«■■■■ 


■■■■■■L 






















!! k 










iH 


!■■■■■■. 




















s 


i 


■ 


-h- 


^l 


■■■■■■■U^Z^J. 






■■■■■I 



600 700 

WAVELENGTH nm 



No. I8B 

Although transmissions above 480 nm are shown in the graphs for Nos. 
18A and 18B filters, the transmission figures are not given in the tables 
owing to the large fluctuations which can occur in the red and infra-red 
regions. 



Nos. 87, 87C, 
88A, 89B 



1 


















i 




















































- 






























































1 










































! 














































~v 




A 87C 
























1! \ 
























\ \ 87 


























L 88A\ 
















- 










\89E 


V \ 




















I 


















_J 



















600 700 



800 900 



WAVELENGTH nm 



TRANSMISSION TABLES 

The following tables give wavelength/transmission figures for the 
nine filters. In addition (for the Nos. 2 A, 2B and 2E) are given the total 
visual transmission factors, expressed as percentages, for the standard 
illuminants 'A' (2854 K), and 'C (mixture of sunlight and skylight, and 
approximately similar to the light from a 6500 K source), as adopted 
by the Commission Internationale de l'Eclairage (C.I.E.). 



FT-9 



WAVELENGTH 
nm 


PERCENTAGE TRANSMISSION 


2A 


2B 


2E 


390 




0.63 




400 


— 


19.0 


— 


10 


4.0 


48.0 


— 


20 


42.0 


67.0 


8.7 


30 


74.0 


75.3 


51.1 


40 


82.7 


80.0 


75.8 


450 


85.6 


83.0 


82.2 


60 


87.0 


85.2 


84.8 


70 


88.1 


86.7 


86.4 


80 


88.8 


88.1 


87.6 


90 


89.4 


88.8 


88.4 


500 


89.7 


89.5 


89.0 


10 


90.0 


89.9 


89.4 


20 


90.2 


90.3 


89.7 


30 


90.3 


90.5 


89.9 


40 


90.4 


90.6 


90.1 


550 


90.5 


90.7 


90.2 


60 


90.6 


90.8 


90.4 


70 


90.6 


90.9 


90.5 


80 


90.7 


90.9 


90.6 


90 


90.7 


91.0 


90.6 


600 


90.8 


91.1 


90.7 


10 


90.8 


91.2 


90.8 


20 


90.9 


91.3 


90.9 


30 


90.9 


91.3 


90.9 


40 


90.9 


91.4 


91.0 


650 


91.0 


91.4 


91.0 


60 


91.0 


91.5 


91.1 


70 


91.0 


91.5 


91.2 


80 


91.1 


91.6 


91.3 


90 


91.1 


91.7 


91.4 


700 


91.1 


91.8 


91.4 


Total Transmission 








CLE. Standard 'A' 

(2854 K) 
CLE. Standard 'C 

(6500 K) 


90.5 
90.3 


90.8 
90.5 


90.3 
89.9 



FT-9 



WAVELENGTH 


PERCENTAGE TRANSMISSION 


nm 


I8A 


I8B 


220 


— 


— 


30 


— 


2.5 


40 


— 


16.2 


250 


— 


42.9 


60 


— 


58.0 


70 


— 


68.7 


80 


— 


75.6 


90 


0.65 


81.8 


300 


2.5 


84.8 


10 


7.6 


86.2 


20 


14.5 


86.8 


30 


25.6 


87.1 


40 


37.2 


87.5 


350 


47.9 


87.3 


60 


52.5 


86.2 


70 


44.7 


82.5 


80 


31.6 


67.6 


90 


4.5 


46.0 


400 


— 


25.0 


10 


— 


13.8 


20 


— 


7.0 


30 


— 


3.8 


40 


— 


2.3 


450 


— 


2.0 


60 


— 


1.6 


70 


— 


1.3 


80 


— 


I.I 


90 


— 


— 


500 


— 


— 



FT-9 



WAVELENGTH 


PERCENTAGE TRANSMISSION 


n m 


87 


87C 


88A 


89B 


700 








11.2 


10 


— 


— 


— 


32.4 


20 


— 


— 


— 


57.6 


30 


— 


— 


7.40 


69.1 


40 


0.10 


— 


32.8 


77.6 


750 


2.19 


— 


56.3 


83.1 


60 


7.95 


— 


69.2 


85.0 


70 


17.4 


— 


74.2 


86.1 


80 


31.6 


— 


77.6 


87.0 


90 


43.7 


— 


79.7 


87.7 


800 


53.8 


0.32 


81.4 


88.1 


10 


61.7 


3.20 


82.6 


88.4 


20 


69.2 


8.90 


83.7 


88.6 


30 


74.1 


17.8 


84.7 


88.8 


40 


77.7 


28.2 


85.5 


89.0 


850 


81.4 


41.0 


86.1 


89.2 


60 


84.0 


53.8 


86.6 


89-4 


70 


85.4 


61.6 


87.2 


89.6 


80 


86.8 


69.2 


87.5 


89-8 


90 


87.8 


74.1 


87.8 


89.9 


900 


88.4 


78.5 


88.0 


90.0 


10 


88.8 


81.5 


88.2 


90.1 


20 


89.1 


83.6 


88.4 


90.2 


30 


89.1 


85.1 


88.6 


90.3 


40 


89.1 


86.0 


88.8 


90.4 


950 


89.1 


87.0 


89.0 


90.5 



FT-9 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 
WRATTEN 



Kodak Data Sheet KODAK LIMITED LONDON 

FT-9 

PDFT-9/xWPI 1/9-71 



KODAK 'EKTALUX' FILTERS 



KODAK 'EKTALUX' FILTERS 

Kodak 'Ektalux' Filters are produced to spectrophotometric standards 
similar to those of Kodak ' Wratten' Filters. 'Ektalux' filters may be used 
wherever a 'Wratten' filter of the same number is recommended. 

The filter material is a specially cast, semi-rigid, thermosetting resin, 
with excellent optical qualities (similar to those of Motion Picture quality 
glass, but at a fraction of the weight). The filters are heat and moisture 
resistant and show better resistance to chemicals and breakage than 
filters cemented between glass. 

As these filters are much thinner than filters cemented between Motion 
Picture quality glass (2 mm and 4.5 mm thick, approximately, instead of 
7-14 mm thick), no focusing or weight difficulties are experienced when 
they are used in front of camera lenses. If these filters are used between 
the lens and film, some re-focusing will be necessary. 

COMPARISON CHART (Other filter types to 'Ektalux') 



PHYSICAL 
CHARACTERISTICS 


FILTER TYPE 




Gelatin 


Cemented 


'Ektalux' 


Optical Quality .... 
Colour Permanence . . 
Combination Usage* . . 

Breakage 

Climatic Conditions . . 

Cleaning 


Good/Excellent 

Good 

Excellent 

Excellent 

Poor 

Poor 

Poor 


Good/Excellent 

Good 

Poor 

Poor 

Good 

Excellent 

Excellent 


Good/Excellent 

Good 

Excellent 

Excellent 

Excellent 

Fair 

Good 



* It is sometimes necessary to use two or more filters of different characteristics, for example, a 
colour-correcting filter together with a neutral-density filter. 

CHARACTERISTICS OF BASE MATERIAL AND DYES 

Base Material 

Clarity: The cast resin has optical qualities comparable to those of 
optical glass. The surfaces are cast to a lustre, smoothness and degree 
of parallelism at least equal to Motion Picture Quality Optical Glass. 
Refractive Index: This is similar to crown glass, although the refractive 
index of 'Ektalux' filters may vary very slightly owing to the method of 
manufacture; it is normally 1.50. 

Stability of Optical Properties: The material used maintains its optical 
properties throughout a wide yariety of different environments and 
conditions of use. It does not crack internally (check) or at the surface 
(craze) as a result of age, stress, or contact with solvents. It possesses 



Issue A 



Kodak Data Sheet 
FT- 10 



excellent photo-elasticity exhibiting no permanent loss in optical proper- 
ties resulting from strain. 

Resistance to Abrasion : This may be up to 30 to 40 times that of acrylic 
plastics according to conditions. Impact resistance is also very good, 
especially at very low temperatures. 

Chemical and Solvent Resistance: Although the base material is immune 
to the effects of most solvents, including acetone and benzene, and to 
most chemicals, other than highly oxydizing acids, the organic dyes used 
to give the spectrophotometric characteristics required may not be so 
immune. 

Gamma Irradiation Resistance: Filters used in some specialist application 
may be subject to gamma irradiation. The transmittance loss of the base 
material alone is of the order of 5 per cent after 100 million roentgens 
exposure. 

Temperature and Humidity Resistance: Filters produced in this material 
give excellent permanence at temperatures up to 80°C (176°F) and good 
permanence when used intermittently at temperatures up to 150°C 
(334°F). Thus, 'Ektalux' filters are entirely suitable for tropical use. 

Humidity has no effect on these filters except by changing the degree to 
which a static charge is built up. (The lower the humidity the more 
static is to be expected). A high static charge on a material will cause 
particles of dust, etc., to cling to the surface, thus making cleaning difficult. 
Raindrops, spray, etc., can simply be wiped off these filters without 
leaving watermarks. 

Dyes 

Most 'Ektalux' filters are prepared using organic dyes. The dyes are 
obtained from a number of sources, and many have been specially syn- 
thesized. Dyes used in filters, like other dyes, may in time change. 
Filters cannot therefore be replaced or otherwise guaranteed against 
changes in transmittance. 

CARE OF 'EKTALUX' FILTERS 

Filters are clean when packed for distribution. With reasonable care 
they can be used indefinitely. If for any reason an 'Ektalux' filter becomes 
so dirty that it cannot be cleaned by simply polishing after breathing on 
it, or by using a soft cloth moistened by a little 'Kodak' Lens Cleaner, the 
use of a soft cloth and a little Perspex Polish No. 2A* is advised. Care 
must be taken to ensure that the cloths used do not contain any grit or 
other matter likely to damage the filter. 

Filters are supplied in metal rims or frames, and are packed in such a 
way as to minimize any possibility of damage. Although these filters 
are highly resistant to finger printing and to abrasion, it is recommended 
that they be stored in the same way as supplied or in a similar fashion (so 
that the filter surface is not in contact with any other surface). 

*Obtaindble from G. H. Bloore Limited, 480 Honeypot Lane, Stanmore, 
Middlesex, HA1 1JT. 

FT-10 2 



'EKTALUX' 85 FILTER 

This is a conversion filter (for use on camera lenses) which is amber in 
colour, and is used for exposing Type A and L colour materials in day- 
light. 

This filter may be used wherever a 'Wratten' 85 filter is recommended. 
The 'Wratten' 85 and 'Ektalux' 85 filters, although similar, have slightly 
different characteristics, but in normal photographic practice, the results 
are indistinguishable one from the other. However, to obtain the most 
consistent colour balance in cine or motion-picture work, use one or the 
other throughout, as, under some unusual conditions, the change may 
possibly be noticed. 



SPECTROPHOTOMETRY DATA AND ABSORPTION CURVES 



WAVELENGTH (nm)* 


DENSITY 


TRANSMISSION 


400 


1.01 


9.8 


410 


0.62 


28.8 


420 


0.50 


31.6 


430 


0.45 


35.6 


440 


0.42 


37.9 


450 


0.40 


39.4 


460 


0.38 


41.5 


470 


0.36 


43.3 


480 


0.35 


45.0 


490 


0.34 


45.5 


500 


0.32 


47.3 


510 


0.30 


50.1 


520 


0.29 


51.2 


530 


0.27 


53.8 


540 


0.24 


57.0 


550 


0.21 


61.6 


560 


0.19 


64.5 


570 


0.18 


66.5 


580 


0.16 


69.1 


590 


0.10 


79.7 


600 


0.08 


82.6 


610 


0.06 


87.8 


620 


0.06 


87.8 


630 


0.06 


87.8 


640 


0.06 


87.8 


650 


0.06 


87.8 


660 


0.06 


87.8 


670 


0.06 


87.8 


680 


0.06 


87.8 


690 


0.06 


87.8 


700 


0.06 


87.8 



* Wavelength is given in nanometers (nm), I nm = lm[J.. 



FT- 10 



































^.l 
































































1.0 
































0.8 






























































0.6 






























































n 4 
































































0.2 






























































































n 













400 



500 



600 



700 



Wavelength (nm) 



Degree of Conversion 

The 'Ektalux' 85 filter is used on the camera lens to enable films de- 
signed for use in artificial light, of approximately 3400K, to be used with 
daylight approximately 5500K. In the Motion Picture field it is often 
used with films balanced to artificial light of 3200K, with further correction 
introduced on printing. 

FILTER FACTOR 

Increase exposure by 2/3 stop. This figure is approximate, for critical 
work a practical test should be made especially if more than one filter is to 
be used. Certain films are packed with an instruction sheet which gives a 
meter setting for that film with a 'Wratten' 85 filter; the same meter 
setting may also be used for the same film with an 'Ektalux' 85 filter. 

MIRED SHIFT VALUE 

Although the 'Ektalux' filter is not intended for photometric use, an 
approximate mired shift value of + 1 12 can be used for most other practical 
purposes. 



Kokak Data Sheet 
FT- 10 



Kodak, Ektalux and Wratten are trade marks. 

KODAK LIMITED LONDON 

FT-IO/xWP9»/9-7l 



KODAK 'POLA' SCREEN 



A Tola' screen is a polarizing medium in sheet form, resembling a 
photographic light filter, but its primary effect is not that of colour absorp- 
tion, but of selective control over reflections. It contains countless, 
minute, rod-like crystals, all parallel to each other, which have the power of 
polarizing light, and, thus, of controlling the brightness of light that is 
already polarized. 

The vibration of light waves is in a plane at right angles to the direction 
of the ray, and usually in all possible directions, that is, up and down, 
sideways, etc. When a ray of light is plane-polarized, it vibrates only in 
one plane; for example, in a horizontal ray, only the vibrations in a vertical 
plane might be left. The crystals in the Tola' screen may be likened to the 
optical equivalent of a mechanical slit, which transmits only light vibrating 
in the plane of that slit. 

The intensity of light already polarized can be controlled by rotation of a 
Tola' screen in its path. The beam is cut off when the vibration plane of 
the polarized light and that of the Tola' screen are at right angles to each 
other, or "crossed", and transmitted to the maximum extent when the 
vibration planes are parallel. 

There are two common sources of polarized light in nature: 

1 Light reflected from a non-metallic surface, such as glass, water, 
polished wood, or glossy paint. The maximum degree of polarization 
occurs when the incident light makes an angle of approximately 35° with 
the plane of the reflector; at greater or lesser angles the effect diminishes, 
until it disappears entirely at 0° and 90°. 

2 Light from a clear blue sky at right angles to the direction of the rays 
from the sun is also strongly polarized; at other angles polarization is 
incomplete, and vanishes at 0° and 180° from the sun. 

Reflected light is composed of two parts, known as the specular and the 
diffuse components. A large proportion of the light reflected from a glossy 
surface is specular, while practically all light reflected from a matt surface, 
such as chalk, is diffuse. Specular reflection may produce glare or un- 
desirable highlight areas that are often objectionable in photographic work, 
and difficult to overcome. 

By rotating a Tola' screen in front of the camera lens, the polarized 
portion of the reflection from a glossy non-metallic surface can be dimin- 
ished or eliminated entirely according to the degree of rotation of the 
screen, and the angle at which light is being reflected through the lens of 
the camera. The effect can be judged by viewing the scene through a 
Tola' screen, rotating it until the maximum or the desired effect is 
obtained, then placing it, with the same orientation, over the camera lens. 

Applications 

I In colour photography, a Tola' screen offers the only known means of 
modifying the sky brightness without affecting the other component 
parts of the picture. A clear blue sky can be darkened to about the 

Issue C Kodak Data Sheet 

FT- 1 1 



same degree as by the use of a 'Wratten' Filter No. 25 (red), without 
affecting the colour rendering of the remainder of the scene. This effect 
cannot be produced, however, when pointing the camera directly towards 
the sun or directly away from it, because light from these directions is not 
polarized. This filter will also reduce the blue cast caused by excess 
ultra-violet radiation or by haze. 

2 Reflections from glass or water can be subdued to show detail beyond or 
below the surface. In a similar way reflections from non-metallic light or 
high-key backgrounds can be effectively subdued to show surface detail or 
texture. This is of the greatest importance when photographs must be 
taken of people wearing spectacles, of shop windows or pictures under 
glass, offish or plants behind glass or under the surface of water, of highly 
polished furniture, lacquered details of machines, shining skin, pathological 
specimens, wet objects, etc. In a studio, when using artificial lighting, the 
Tola' screen can be used to reduce the reflections from light sources or 
bright backgrounds, or to emphasise the texture of the grain in wood, lino, 
fabrics, leather, glazed or unglazed ceramics, painted or lacquered 
objects, etc. 

3 With a Tola' screen over the camera lens, and with Polaroid sheet 
material over the lamps, complete control of reflections may be obtained 
in studios when photographing either metallic or non-metallic objects, 
or when photographing any surfaces, e.g., glassware, showing specular 
or other troublesome reflections. 



All Tola' screens are marked to indicate the polarizing axis. They are 
physically similar to Kodak 'Wratten' filters, and should not be subjected 
to excessive heat which might cause damage; they may be used in standard 
filter holders which permit them to be rotated in front of the camera lens 
through an angle of 180°. 

The colour of Tola' screens is a neutral grey having a density of approxi- 
mately 0.4, necessitating an exposure increase of approximately 1| stops; 
they absorb in the ultra-violet, and transmit freely and without polarization 
in the infra-red. 

APPENDIX 

The Tola' screen is supplied by Kodak Limited in acetate form in 
sizes 50x50 mm, 75x75 mm and 100 X 100 mm or cemented in glass in 
the same forms as Kodak 'Wratten' Filters (see Data sheet FT-1), in any 
size up to and including 100 mm diameter or square. If larger material 
than this is required, for example, for use over lamps, the following 
Company provides Polaroid sheet material in larger sizes : — 
Polarizers (United Kingdom) Ltd. 
Cressex Estate, 
Lincoln Road, 

High Wycombe, 

Buckinghamshire. 

Kodak, Pola, and Wratten are trade marks 

Kodak Data Sheet KODAK LIMITED LONDON 

FT- 1 I 

PDFT-ll/xWPI0/8-7l 



Kodak Data Book 



List of Sections in the five volumes 



1 



Index 
RF Reference 
GN General Technique 
AV Audiovisual 
FT Filters and Equipment 













2 


XR 


Radiography 




MD 


Medical Applications 






IN 


Industrial Applications 






SC 


Scientific Applications 






DC 


Document Copying 











CL Colour 
PR Processing 
FY Formulary 



SE Sensitized Materials 
PL Plates 
PP Papers 



FM Films 



TO CLOSE - Squeeze UPPER LEVERS together 



TO OPEN 



Use LOWER LEVERS 




Twist first 



then squeeze 



RADIOGRAPHY 



CONTENTS EDITION 

XR.-2 Penumbra! Unsharpness — 

XR-3 Localisation in Radiography Issue A 

XR-4 Intensifying Screens Issue E 

XR-5 The Storage of X-ray Films and Radiographs Issue A 

XR-6 Processing X-ray Films Issue £ 

XR-7 Faults in Processing X-ray Films — 

XR-8 Tropical Processing of 'Kodak' X-ray Films Issue C 



Associated Data Sheets in this or other volumes or sections 

I, RF-I I Stains Appearing on Stored Monochrome Negatives and 
Prints 

1, GN-2 Copying Radiographs and Other Transparencies 

2, MD-5 Tomography 

2, IN- 12 Contact Microradiography 

2, IN- 14 The Radiography of Light Alloys 

2, IN- 1 5 Weld Radiography 

2, IN- 1 6 Gamma-Radiography 

2, SC-IO Autoradiography 

2, SC-15 The Photographic Aspects of X-ray Crystallography 



Kodak is a trade mark KODAK LIMITED LONDON 

YI265PDDB-38/xWP9i/4-72 



PENUMBRAL UNSHARPNESS 



The influence of the focal-spot size and the focus-to-film and object-to-film 
distances on the definition in a radiograph is determined by the size of the 
penumbra (p) whose formation is illustrated diagrammatically in Figure 1. 



OBJECT - 



According to this diagram : 

p : b = / : (a - b) 

f X b 

or p = 

a — b 

The curves overleaf (Figure 2) give the width of the penumbra (j>) in 
millimetres at various object-to-film distances for a focal-spot diameter of 
one millimetre and focus-to-film distances of 60, 100, and 200 cm. 

The object : film distances are plotted on the abscissa and the penumbra 
width as the ordinate. In order to find the width of penumbra for other 
than a 1-mm focal-spot diameter, the values found on the ordinate of 
Figure 2 are multiplied by the diameter in millimetres of the focal-spot 
concerned. (Example : To find the width of the penumbra when the focal- 
spot diameter = 3 mm, the object-to-film distance 20 cm, and focus-to- 
film distance is 100 cm : according to Figure 2, the width of the penumbra 
is 0.25 mm at the given distances, but this value is valid for a focal-spot 
diameter of 1 mm. For a given diameter of 3 mm, it is 0.25 mm X 
3=0.75 mm) 

In practice it is found that the actual width of penumbra is not quite 
as wide as the calculated figure, but the relative proportion of the size of 
penumbra under various conditions agrees with that of the calculated 
values of Figure 2. This effect is illustrated in Figure 3, from which it 

Kodak Data Sheet 
XR-2 



10 



0-9 



£ 0-6 



0-5 



0-4 



0-2 















60 cm 
































































































100 cm 
















































200 cm 





















10 15 20 25 

OBJECT-TO-FILM DISTANCES IN cm 

Figure 2 



can be seen that only the region to the left of A receives the total radiation 
emitted by the target, whereas to the right of A, the amount of radiation 
is gradually decreasing, as the target area, which contributes to the image 
formation, becomes gradually smaller. 

When the object is smaller than the focal-spot size special aspects apply. 
If the object-to-film distance is comparatively great, no true shadow of a 
relatively small object will be projected on to the film plane; this is shown 



XR-2 



m 



Figure 4. The image formed will be produced principally by the 
penumbra and by a pseudo half-shadow and this image may differ appre- 
ciably from its expected shape. It follows that the best conditions for 
image formation are a short object-to-film distance, a long focus-to-film 
distance and a relatively small focal-spot size. 



TARGET 



Edge of object 




PENUMBRA 



mm: 




MM 



Figure 3 Density distribution of penumbra image at edge of object 
3 



XR-2 



Figure 4 Projection of 
object smaller than the 
focal-spot diameter 




-4-FILM PLANE 



Kodak is a trade mark 



Kodak Data Sheet 
XR-2 



KODAK LIMITED LONDON 



PDXR-2/r3WPIi/6-7l 



LOCALISATION IN RADIOGRAPHY 



It is frequently important to find the positions of foreign bodies in patients, 
or defects in castings or welds, which have been detected radiographically. 
Apart from the stereoradiographic method in which their position may be 
assessed visually, suitable radiographs allow calculation of the depth of 
foreign bodies or defects, by measurements made on a second radiograph 
obtained by the tube-shift method, in which two exposures are made on 
the same film with the X-ray tube in two positions. The resultant radio- 
graph exhibits a double image and the separation of the two images of the 
foreign body or defect is the important factor. 

Method I 

This technique is readily applicable where the object can be laid directly 
on the film or its cassette and the X-ray tube can be moved through a 
known distance of a few inches. The layout of the apparatus is shown in 
Figure 1 where A and P are the two positions of the X-ray tube. The full 
lines AC, PQ show the beams which are effective with respect to the 
defect B. 




By proportion, 



from which 



D-d 



s 
D 



X s 



t + s 

Suitable values for D and t will 
depend on individual circum- 
stances, usual values being: 

t = 12 inches (30 cm) 
and D = 36 inches (90 cm) 



Figure 



It is essential to measure the image shift along a line parallel to the 
original X-ray tube displacement. 

Where the foreign body or inclusion is linear the tube shift should always 
be in a direction at right angles to the length of the defect. 

It should be noted that this method gives the distance between the 
foreign body or defect and the film, which includes object-to-film distance 
for which allowance must be made in assessing the position of the defect 
within the subject. 

Method 2 

Two small lead markers, preferably wires, are used, one in contact with 
the upper surface of the object and the other on its base, which need not 
be in contact with the film or cassette. The tube-shift in this method is 
again a few inches but this distance need not be measured accurately. 



Issue A 



Kodak Data Sheet 
XR-3 



References to Figures 2 and 3 will show that the displacement of the 
image of the defect will lie between the displacements of the upper and 
lower markers, i.e. between x x and x 2 . If lead wires are used as reference 
markers they should be placed parallel to the major axis of the defect. The 
tube shift should again be perpendicular to this axis. The position of the 
defect above the lower surface can be determined from a graph in which 
the depth of the defect is plotted against the displacement of its image using 
the displacement of the upper and lower surface marks as reference data. 





Figure 2 



Figure 3 



DISTANCE 

OF DEFECT 

FROM LOWER 

SURFACE 

(INCHES) 




DISPLACEMENT OF IMAGE (INCHES) 



Figure 4 

In a typical example, when radiographing a specimen 2 inches thick, 
it was found that the displacements of the images of the upper and 
lower lead markers were 1.0 inch and 0.3 inch respectively. On plotting 
the distance of the defect from the lower surface (in inches) against the 
displacement of the image (in inches) a straight-line graph (Figure 4) is 
obtained from which it is seen that an image displacement of 0.8 inch 
corresponds to a defect 1.43 inches from the base of the object. 



XR-3 



The distance (d) of the defect above the lower surface of the specimen 
can also be calculated from the following formula: 

where T= thickness of specimen 
S t = defect image shift 
S 2 = bottom marker image shift 
5 3 =top marker image shift 

Substituting the figures from the previous example in the formula : 

0.8 - 0.3 

d=Z 2 X 1.0 - 0.3 incheS 
= 1.43 inches 

It is of interest to note that the measurements required in this method 
are those on the radiograph and the thickness of the object; consequently 
no great care is required in setting up the apparatus as long as the vertical 
distance between the tube and the plane of the film is constant and the 
displacement of the tube is relatively small compared with the focus-to- 
film distance. 

Method 3 

A somewhat similar method makes use of a localiser having holes at 
regular intervals which, in the double-exposure technique, provide a ref- 
erence scale of image displacement. The method is generally applicable. 

As will be seen from Figure 5, the localiser is of simple construction, 
consisting essentially of a metal plate, containing the regularly spaced holes, 
supported at a fixed angle to the cassette by means of a suitable frame. 

The localiser is so constructed that the holes are 1, 2, 3, etc., cm or inches 
from the base, as illustrated in Figure 6. The furthest hole from the base 
should be at a distance equal to or greater than the thickness of the speci- 
men to be examined. By making the base CA twice the length of AB the 
one localiser provides two ranges according to whether AB or AC is 
considered as the base. 




Figure 5 Figure 6 

XR-3 



In use, the localiser is placed with the base on the cassette with the 
specimen and a double exposure is made with the tube-shift parallel to 
PQ in Figure 5, i.e., at right angles to the line joining the holes. 

The resulting image displacement of the inclusion, blow hole, or other 
fault is then compared with the image displacements of the holes in the 
localiser. Clearly the distance of the fault from that part of the object in 
contact with the cassette is equal to that of the hole in the localiser which 
gives the same image displacement. 

When the specimen cannot be in immediate contact with the cassette the 
distance of separation should be deducted from that value given by the 
localiser. 



Accurate localisation 

Owing to the geometric distortion in the radiographic image due to the 
fact that the X-ray beam consists of diverging rays, the actual position of 
the defect relative to nearby landmarks is not immediately obtainable from 
the radiograph. The above methods therefore only define the plane in 
which the defect lies. For accurate localisation in this plane two metal 
cross-wires may be mounted on the front of the cassette, dividing the front 
into four equal rectangles. The position of the body relative to the cross- 
wires is marked by inking the wires, which are pressed into contact with 
the body in such a way that their intersection is as far as possible just over 
or under the foreign body or defect. 

The tube is then displaced from the intersection parallel to one of the 
cross-wires over a distance equal to half of that of the usual tube-shift 
distance and the first exposure is made. The tube is then displaced 
parallel to the same cross-wire as before so that it is now centred over a 
point on the otherside of the intersection, this point again being distant 
from the intersection by an amount equal to half the usual tube-shift : the 
second exposure is then made. 

The resulting radiograph will ap- 
pear as in Figure 7 where C and D 
represent identical points on the 
two shadows of the same defect. 
As described above, the depth of 
the plane in which the defect lies 
is given by the separation of the 
images CD. If the tube was moved 
parallel to the wire PQ so that A 
and B are the two points over which 
the tube was centred, then the 
intersection of AD and BC will 
give the position of the defect 
relative to the intersection of the 
cross-wires in the plane defined by 
Figure 7 the distance CD. 



!a- 



CROSS 
' WIRES 



XR-3 



References of industrial interest 

W. Watson, Simple Triangulation and Localisation, Radiography, 6, 1940, 
p. 107 (geometry of localisation). 

J. Scott, A Simple Localiser, Radiography, 6, 1940, p. 143 (article on the 
localiser mentioned under Method 3: see also addendum in Radio- 
graphy, 6, 1940, p. 177). 

References of medical interest 

J. F. Brailsford, Simple Radiographic Methods for the Localisation of 
Foreign Bodies, Brit. J. Radiol., 6, 1939, p. 65. 

D. B. McGrigor, Selected Methods of Foreign Body Localisation adaptable 
to Radiology in Wartime, Brit. J. Radiol., 5, 1939, p. 619. 

W. Watson, Simple Triangulation and Localisation, Radiography, 6, 1940, 
p. 107 (geometry of localisation). 

J. Scott, A Simple Localiser, Radiography, 6, 1940, p. 143 (article on the 
localiser mentioned under Method 3: see also addendum in Radio- 
graphy, 6, 1940, p. 177). 



XR-3 



KODAK 

is a trade mark 



Kodak Data Sheet KODAK LIMITED LONDON 

XR-3 

PDXR-3/r4WPIi/6-7l 



INTENSIFYING SCREENS 



When an X-ray beam strikes a photographic emulsion, usually less than 
1 per cent of the X-ray energy is effective in producing a latent image. 
So that a higher efficiency can be obtained, intensifying screens may be 
used with radiographic films. 

These screens are of two distinct types, each having a different applica- 
tion and intensifying E.ction, and are known respectively as lead intensifying 
screens and fluorescent-salt intensifying screens. 

LEAD INTENSIFYING SCREENS 

Lead intensifying screens are widely used in industrial radiography 
because they minimize the effects of scattered radiation on the image, and 
can simultaneously intensify without adding to the radiographic unsharp- 
ness. This latter feature is of particular value in radiography with 
high-voltage X-rays and short-wave gamma-rays, in conjunction with 
fine-grain, high-contrast, direct-type X-ray films. 

Lead screens in contact with the film during exposure have two principal 
effects. Firstly, they intensify the X-ray image on the film, mainly by 
the emission of elections from the lead under X-ray excitation and, to a 
smaller extent, by the emission of secondary X-rays. Since the intensifi- 
cation is greater the shorter the wavelength of the radiation, it follows 
that this differential intensification results in the initial primary beam 
being intensified more than the longer wavelength radiation, some of 
which is scattered radiation. In addition, lead screens provide differen- 
tial filtration, the longer wavelength scattered radiation being absorbed 
more readily than the shorter wavelength primary X-rays which have 
passed through the object and are, therefore, true image-forming rays. 
The reduction in the effect of scattered radiation on the image results in 
greater contrast and clarity in the radiographic image. This reduction in 
the scattered radiatbn decreases the total intensity of the radiation 
reaching the film and, in addition, the absorption of the front lead screen 
also diminishes the to:al amount of radiation reaching the film. For these 
reasons, no intensifying effect is observed unless the X-radiation is 
generated above 120- ] 40 kV. At about 250-300 kV, the intensifying effect 
of the lead screens ca:i be most marked, reducing the exposure required to 
between one-third and one-quarter of that without screens. With gamma- 
rays and million or multi-million volt X-rays, the intensification produced 
by lead screens may reduce the exposure required to approximately 
one-third. If the incident radiation is not sufficiently energetic, i.e., is 
generated below about 120 kV, absorption may more than counterbalance 
the intensification, and the exposure required will be even greater than 
without screens. Often, however, this increase in exposure can be 
justified as the absorption of scattered radiation produces a much clearer 
radiographic image. 

The intensification from lead screens depends upon the film, the kilo- 
voltage, and the thickness and kind of metal through which the rays have 

Issue E Kodak Data Sheet 

XR-4 



passed; additionally, the type of circuit used in the X-ray unit will have 
an effect. 

Lead screens are particularly valuable in reducing the scatter which 
undercuts the object when primary rays strike the portions of the film 
holder or cassette outside the area covered by the object. In practice, 
the lead-screen technique may be applied to advantage in the radiography 
of thick, light-alloy components which produce serious scatter owing to 
their complex shape, despite the fact that the kilovoltage may be too low 
to produce any intensification. 

Sometimes, with fluorescent-salt intensifying screen exposures, a lead 
screen 0.10 or 0.15 mm (0.004 or 0.006 inch) thick is used as a filter. 
When placed between the front of the cassette and the front salt inten- 
sifying screen, such a filter helps to reduce scattered radiation, without 
any serious loss of speed. 

Since lead screens are radiographically grainless, the advantages 
mentioned above are obtained without any loss in definition, provided 
that the screens are held in close and uniform contact with the film 
during the exposure. This feature, and the others already mentioned, 
render the lead-screen technique ideal for the radiography of heavy-metal 
specimens, particularly where very fine defects such as cracks must be 
detected. 

It should be noted that very deep scratches on the lead will show on the 
X-ray film. Dust, grease, and fluff are also detrimental to a good image 
and should be avoided by periodic cleaning. 

For maximum contrast and highest speed, lead intensifying screens 
should be used with "non-screen" or direct-type X-ray films. 

Recommended film for use with lead screens 

Kodak 'Industrex' M, A and C Films for very fine detail work. Their 
high contrast and fine grain make these films ideal for gamma-radiography 
and for use with X-rays of 1 MV and above, as well as for radiography 
using X-ray energies below these values. 'Industrex' M film gives a finer 
grain result than 'Industrex' C film which in turn gives finer grain than 
'Industrex' A film. However 'Industrex' C film is 5-6 times as fast, and 
'Industrex' A film 4-5 times as fast as 'Industrex' M film. These films 
are recommended for all lead-screen exposures in which the finest details 
must be revealed (see Data Sheets FM-25, 26 and 28). 

Kodak 'Industrex' D film for high contrast combined with medium 
grain (see Data Sheet FM-27). 

'Kodirex' X-ray Film for the fastest exposures with lead screens. 
Medium-high contrast, and a speed at least twice that of 'Industrex' D 
Film (see Data Sheet FM-17). 

FLUORESCENT-SALT INTENSIFYING SCREENS 

Certain chemical salts have the property of fluorescence; under the 
excitation of X-rays, they will emit light. This property is utilized in 
radiography by placing an X-ray film between two screens coated with 

xr-4 2 



fine crystals of one of these salts; on exposure to X-rays, the crystals 
glow and the light emitted affects the film. Some photographic emulsions 
are much more sensitive to light than to X-rays, and thus the salt screens 
intensify the radiographic effect, allowing a shorter exposure time, or a 
lower kilovoltage to be used. The intensity of the light emitted depends 
on the intensity of the X-ray beam, on the kilovoltage in use, and on any 
filtration of the beam. 

A compound which is commonly used in intensifying screens is the 
white crystalline salt, calcium tungstate. The double salt barium lead 
sulphate is also used under certain conditions. In the manufacture of 
salt screens, the crystals of the salt are finely powdered, mixed with a 
suitable binder, and coated in a thin, smooth layer on a thin sheet material 
support. The front screen, that is the one placed on the X-ray tube 
side of the film, has a thinner layer of crystals than the back screen. In 
use, an X-ray film, usually one specially sensitized to respond to the 
light emitted, is sandwiched tightly between the two screens in a rigid 
metal cassette or film holder which will ensure overall contact between 
screens and film. The photographic effect on the film is then the sum 
of the effects of the X-rays and of the light emitted by the screens, the 
latter generally having by far the greater effect. 

The light from any individual crystal spreads out beyond the confines 
of the original X-ray beam which excites the crystal to fluorescence. 
These areas of light overlap and give rise to blurring of the detail in a 
radiograph; furthermore, the light tends to spread within the emulsion 
layer. These effects combine to cause poorer definition in radiographs 
made with salt screens; the smaller the crystals in the screen, the better is 
the definition. 

'Kodak' intensifying screens 

Three types of 'Kodak' intensifying screens using calcium tungstate 
crystals coated on a cardboard support are available, namely High Speed 
Intensifying Screens, Regular Intensifying Screens and Fine Grain 
Intensifying Screens. 

The Fine Grain Screens have smaller crystals than the Regular, or 
High Speed Screens and consequently give better definition, but they 
have an intensifying factor that is approximately half that of the Regular 
Screens and one quarter that of the High Speed Screens. 

The intensifying factor of Fine Grain Screens using X-rays generated 
at around 150 kV is approximately 225. As the X-ray generating voltage 
increases, this factor reduces until with gamma rays from Cobalt 60, for 
example, it may become negligible. 

Recommended film for use with fluorescent-salt intensifying screens 

Kodak 'Royal Blue' and 'Blue Brand' Medical X-ray Films are suitable 
for use with these screens. 



XR-4 



The following product names appearing 
in this Data Sheet are trade marks 



KODAK 
INDUSTREX 

KODIREX 
BLUE BRAND 



Kodak Data Sheet KODAK LIMITED LONDON 

XR-4 

YI233 PDXR-4/xWP 1 0/2-72 



THE STORAGE OF X-RAY FILMS 
AND RADIOGRAPHS 



For many years, 'Kodak' X-ray films have been coated on safety bases. 
'Estar' polyester safety base (as now used) and cellulose ester safety base 
(as previously used), whether as unprocessed films or as radiographs, 
present no greater a fire hazard than an equivalent quantity of paper 
records; see British Standard 850: 1955, Definition of Cinematograph 
Safety Film. 

Radiographs on cellulose nitrate base which do present a serious fire 
risk may still be held in old files; the storage of these films demands 
special precautions, and Kodak Limited will gladly give advice. As a 
guide in deciding whether old radiographs are on a safety or on nitrate 
base, all 'Kodak' X-ray films manufactured after December 1940 were 
coated on safety bases. 



X-ray films 

Unprocessed X-ray films, like all other sensitized materials, slowly 
deteriorate in quality. The first sign of such fall in quality is shown as a 
higher fog. Accordingly, keep the stock of film to a minimum, de- 
pendent on the ease with which fresh stock is obtainable. This minimum 
stock should be such as to withstand any sudden demand, as well as 
possible delay in delivery beyond the control of the distributor. 

The store personnel should record the date of receipt of all X-ray films, 
and ensure that the oldest materials are issued first. Tests should always 
be made prior to the use of out-dated material or material suspect through 
knowledge of previous storage conditions. 

Unless controlled storage conditions of the type described below are 
available, it is recommended that the stock should not exceed 6 months' 
supply. When it is required to store unexposed films for a longer period 
than this, it is recommended that in addition to the precautions mentioned 
below, they should be kept at a temperature of 10°C (50°F) in an atmos- 
phere of which the relative humidity is within the range 40-60 per cent. 

To avoid possible pressure marks on the films, due to folds in the packing 
materials, store boxes standing on edge, so that they are side by side and 
not stacked horizontally one on top of another. 

Store X-ray films at as great a distance as possible from any source of 
X-rays or gamma rays and, if necessary, protect adequately by a suitable 
thickness of lead or other radiation-absorbent material. 

Store all films in a cool, dry place away from any possibility of exposure 
to any harmful gases, such as formaldehyde, hydrogen sulphide, sulphur 
dioxide, ammonia, coal gas, industrial gases, motor exhausts, mercury 
vapour and vapours of solvents and cleaners. 

Kodak Data Sheet 
Issue A XR-5 



Radiographs 

The images of radiographs may be considered to be reasonably perman- 
ent provided that both fixing and washing are carried out thoroughly, as 
recommended by the manufacturers. As previously stated, all 'Kodak' 
X-ray films are now coated on safety film base, and fire security need be 
no greater than that with paper records. 

When radiographs are to be kept for any appreciable length of time, it 
is necessary that their fixing and washing be carried out thoroughly. Full 
details are given in Data Sheet XR-6, and in the Data Sheets describing 
individual X-ray films. 

The room or store in which radiographs are kept should ideally be cool, 
dry and well ventilated. These ideal conditions are represented by a 
temperature of 15°-27°C (59°-81°F) and a relative humidity of 40-50 per 
cent. From the financial aspect, however, this would be unneces- 
sarily ambitious unless the radiographs were regarded as rare examples of 
diseases in medical radiography or faults in industrial radiography, or 
unless there was other good reason for keeping radiographs for a pro- 
tracted period. In these cases, as with unprocessed X-ray films, avoid 
contact with all harmful gases, such as formaldehyde, hydrogen sulphide, 
sulphur dioxide, ammonia, coal gas, industrial gases, motor exhausts, 
mercury vapour and vapours of solvents and cleaners. When planning 
an archival store of this nature, make provision for all incoming air to be 
filtered before being passed in. 

In a number of cases, the maintenance of the conditions described 
in the preceding paragraph will be impossible or undesirable; they should 
be relaxed according to the estimated length of time for which the radio- 
graphs concerned are required to be kept. Keep the temperature below 
27°C (81°F); its constancy is more important than its actual level. Relative 
humidities of 25-60 per cent are permissible. 



Kodak and Estar are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

XR-5 

PDXR-5/xWPI3/4-69 



PROCESSING X-RAY FILMS 



An X-ray film consists of a transparent flexible support coated on both 
sides with an emulsion of silver halide (e.g., bromide or iodide) suspended 
in gelatin, the silver halide being distributed throughout the emulsion 
as minute crystals. Exposure to X-rays, gamma rays or light alters these 
crystals in such a way as to produce a latent (i.e., invisible) image. 

The correct exposure might be defined as that which produces an ideal 
radiograph when the film is processed as recommended. As there are 
so many variables in making a radiograph, it is helpful if as many factors 
as possible are kept fixed. Standardized X-ray processing is achieved 
by following the developing time and temperature table on page 6 and with 
consistent agitation. Such constant developing conditions form the basis 
for the standardization of exposure conditions that enables an exposure 
chart to be made. 

As with conventional monochrome negatives, chemical processing is 
necessary to make the film of practical use. It is treated first with a 
developing solution which renders the latent image visible, and next 
with a fixing solution which dissolves away the unexposed silver halide. 
It is then washed in water to remove the fixing solution and by-products, 
and finally dried. Maximum diagnostic value in a radiograph is only 
attained if every stage is carried out carefully in proper working conditions. 

DARKROOM ILLUMINATION 

X-ray film is sensitive to X-rays, gamma rays and blue light, and until 
the film is fixed, it must be handled in light from which blue is absent. 
'Kodak' safelight filters of a suitable colour filter out the blue rays while 
passing the maximum amount of that part of the visible spectrum to 
which the film is relatively insensitive. A general and uniform illumination 
of the room can be obtained with white or light-coloured walls and ceilings 
and by using a combination of indirect and direct safelighting with one or 
more 'Kodak' Universal Safelamps. Fit a 'Kodak' Safelight Filter No. 
6BR (light brown) to the top aperture and a 'Kodak' Safelight Filter 
No. 6B (brown) to the lower aperture of each safelamp and use a 25 watt 
pearl lamp. For localized illumination, use a 'Kodak' Beehive Safelamp 
fitted with a 'Kodak' Safelight Filter No. 6B (brown) and a 25 watt 
pearl lamp. The light from a Universal Safelamp is preferable, as 
it allows a higher level of general illumination in the darkroom, making 
for greater ease in working. 

Unwrapped film should not be handled nearer than 4 feet (1.2 metres) 
from the direct light of the safelamps, but at that distance film may be 
exposed for the normal handling time without risk of fogging. Keep the 
supply of film covered whenever possible. 

Safelight test 

X-ray film which bears a latent image is more sensitive to darkroom 
illumination than unexposed film. Therefore, any safelight test should 
show the effects of prolonged exposure to the safelighting, both before 

Issue E Kodak Data Booklet 

XR-6 



and after the X-ray exposure, and at the times for which the material can 
be exposed to the safelight without risk. 

If the two following tests are not done for each grade of film in use, 
they should be made on the fastest film. If the safe time is less than 
the normal handling time (allowing sufficient handling time for the 
maximum number of films likely at one time) then : 

(a) the safelamps should be inspected for leaks of white light. 

(b) the safelight filters should be inspected for damage of any kind. 

(c) the lamp fitted in the safelamps should not be more than 25 watts. 

(d) move the safelamps further away. 

(e) protect the films from the safelight rays by suitable shielding or by 
turning out localized lighting. 

Test 2-Screen-type Film: For this test, select the fastest screen-type film 
in current use. In total darkness cut an 8 X 10 inch sheet of the chosen 
material in half, lengthways; return one half to its original packing, 
and load the other half into a cassette. Give a flash exposure to X-rays. 
If Kodak 'Blue Brand' Medical X-ray Film ('Estar' Base) is being 
used in conjunction with medium speed screens, the following exposure 
conditions will prove adequate for the flash exposure — 2.5 mAs, 60 kV, 
focus-to-film distance 1.5 metres (5 feet). 

Still in total darkness, remove the exposed film from the cassette and 
place it along with the unexposed half on the darkroom bench, beneath the 
safelamp(s) to be tested, and at the closest working distance (not less than 
1.2 metres (4 feet)). Place a mask, such as a piece of opaque card or 
paper which is larger than the sheet of film, so as to cover a 25 mm (1 inch) 
strip of the exposed and unexposed halves. Arrange five pairs of small 
opaque objects e.g., coins, on the uncovered parts of both the exposed 
and unexposed halves of the film in two lines with equal spacing between 
them. Switch on the safelamps(s) to be tested and expose the test films to 
the safelighting. Advance the mask in steps, to cover successive pairs of 
opaque objects at 30 second intervals {\, 1, 1J, 2 and 2\ minutes, re- 
spectively) so providing steps of progressively increased exposure. 
Switch off the safelamps and process the films in the normal way. Ex- 
amination will reveal the safe limits for both exposed and unexposed films. 

Even within these safe limits, it is unwise to leave exposed or unexposed 
X-ray film lying around in a darkroom under safelighting conditions. 
If it is inconvenient to process a film immediately after exposure, it should 
be placed in a light-tight drawer or box. 

Test 2-Non-Screen or Direct Type Film: With the safelamps switched on, 
load a film into a cassette or exposure holder at the nearest point on the 
bench to the safelamp for normal working. Work at normal speed. 
Give the cassette and film a flash exposure to either X-rays or gamma 
rays to give an overall and even density of about 0.5. 

Switch out the safelamps and unload the film. Lay it on the bench 
at the nearest working point to the safelamps. Cover up a strip of the 
film with a piece of opaque card or paper which is larger than the film and 
place four small objects, e.g., coins, along the length of the rest of the 
film. Switch on all the safelamps in normal use. After 1 minute, move 
the card to cover up one coin. After a total time of 2 minutes cover up 
another coin. Continue to cover further coins at 4 and 8 minutes. 

XR-6 2 



Switch off the safelamps and process the film in the normal way. 

Examine the film carefully to see which outlines of the coins are visable 
in their respective steps. These indicate an unacceptably long exposure 
to the safelighting. The next step to those visible, indicates the longest 
time that the film may be exposed to the safelighting after the X-ray or 
gamma-ray exposure, assuming always that the handling of the film in 
safelighting during the loading of the cassette does not take longer than 
in the test. It is more important to protect the film from excessive 
safelight exposure after the X-ray or gamma-ray exposure than before it. 

AUTOMATIC PROCESSING WITH THE KODAK 'X-OMAT' SYSTEM 

Using this system the radiograph is processed and dried automatically, 
ready for inspection and interpretation in as little as 90 seconds (medical) 
or 10| minutes (industrial). 'X-Omat' Processors will process sheet and 
roll film up to a maximum width of 432 mm (17 inches), and in any 
length. Illustrations of two models are shown in Figures 1 and 2. 

The film is removed from its cassette, fed into the processor on a film- 
feeding tray and conveyed through the processor by a system of rollers. 
These are arranged to pass the film through developer, fixer, wash, and 
dryer sections completely automatically. The rollers are mounted in 
racks which are immersed in deep tanks of solutions; recirculation 
pumps together with the rotation of the rollers produce vigorous and 
uniform agitation. Development and replenishment is automatic using 
the chemicals which have been specifically designed for use with the 
'X-Omat' system. These factors, together with the relatively high 
temperatures used in 'X-Omat' processing, account for the short pro- 
cessing time, the reduction in wastage due to film damage, and the very 
high quality that is consistently achieved. 





Fieure I Kodak RP 'X-Omat' Pro- Figure 1 Kodak 'X-Omat' Processor, 



cessor, Model M6A-N 



Industrial Model 2 



XR-6 



MANUAL PROCESSING 

Manual processing of X-ray film is carried out in deep tanks in which 
the films are suspended by film hangers. This method of processing 
enables a number of radiographs to be processed simultaneously and 
simplifies the problem of standardized treatment. Figure 3 shows the 
'Kodak' Processing Unit P3 which is a compact processing unit specifically 
designed for manual processing. 




Figure 3 'Kodak' Processing Unit P3 

Loading film into hangers 

When the exposed film is removed from the cassette or envelope, 
risk of damage can be reduced to a minimum by immediately placing the 
film into a suitable type of hanger and leaving it in this throughout the 
whole of the processing operations. There are two types of 'Kodak' 
film hanger: tension-clip type and the channel type. Films loaded 
in tension hangers may be left in them during drying. Special pre- 



XR-6 



cautions therefore are not necessary for avoiding damage to the wet 
film at any time during processing and drying. After processing in 
channel hangers, films should be transferred to 'Kodak' Film Hanger 
Bars and further Hanger Bars or clips should be attached to the bottom 
edges of the films to act as weights and to prevent curling. Care should 
be taken to prevent the wet films from touching one another. 

Development 

All X-ray developers contain four essential constituents in solution : 

1 The developing agents (e.g., 'Elon', hydroquinone, or 'Phenidone') — 
which convert the silver halide grains affected by the exposure to black 
metallic silver. 

2 The accelerator (e.g., sodium hydroxide or sodium carbonate) — 
an alkali which makes the developing agent function more efficiently. 

3 The preservative (e.g., sodium sulphite) which retards the rate of 
oxidation of the developing agents, and stabilizes their oxidation products, 
thus minimizing the loss in developing properties. 

4 The restrainer (e.g., potassium bromide) — which ensures that the 
developer reduces only the exposed silver halide grains, i.e., it prevents 
chemical fog. 

In addition to these main constituents, X-ray developers often contain 
small quantities of other substances — such as sequestering agents — added 
for special purposes. 

Two developers are recommended : 
'Kodak' DX-80 Developer — supplied as a concentrated liquid. 
'Kodak' D-19 Developer — supplied as a packed developer powder or 
made up according to the formula given in Data Sheet FY-2. 

The corresponding replenishers for these developers are : 
'Kodak' DX-80R Replenisher — supplied as a concentrated liquid. 
'Kodak' D-19R Replenisher — supplied as a packed replenisher powder 
or made up according to the formula given in Data Sheet FY-2. 

'Kodak' X-ray films are, in general, designed to give the optimum 
result when developed in 'Kodak' DX-80 Developer (diluted 1+4) for 

4 minutes or in 'Kodak' D-19 Developer (undiluted) for 5 minutes at 
20°C (68°F) with intermittent agitation. 

Generally speaking, nothing is to be gained by "juggling" with the 
development conditions in an attempt to correct for faulty exposure 
technique in the ordinary run of work. Once the conditions have 
been decided upon they should be adhered to for all subsequent work. 
Only by standardizing in this way can an efficient check be kept on the 
accuracy of the X-ray exposures. 

It may not always be convenient to maintain the darkroom at a uniform 
temperature and accordingly it is usual to control the temperature of the 
developing tank by means of a water jacket. Although it is a comparatively 
simple matter to raise the temperature of this jacket in cold weather by 
an immersion heater or equivalent means, in hot weather it may be 
impracticable to keep the developer temperature as low as the recom- 
mended level of 20°C (68°F). It is then permissible to compensate for 
a higher working temperature by reducing the development time in 

5 XR-6 



accordance with the values given in the time-temperature on page 6. If the 
temperature of the developer is much above 32°C (90°F) the emulsion on 
the film may become so swollen that it is easily damaged or it may wrinkle 
up into a fine network of lines ("reticulation"), when transferred into the 
stop bath or wash, particularly if a non-hardening fixer is being used (see 
Data Sheet XR-7, Figure 8). If the temperature of the developer is 
above 24°C (75°F), refer to Data Sheet XR-8, Tropical Processing of 
'Kodak' X-ray Films where recommendations are given for the tempera- 
ture range 24-32°C (75-90°F). 

The 'Kodak' Processing Unit P3 has a thermostatically controlled 
water jacket round the processing tanks, thus ensuring uniform processing 
temperatures. 

Time-temperature table : The developing times at various temperatures 
corresponding to 4 minutes for DX-80 Developer and 5 minutes for D-19 
Developer at 20°C (68°F) are shown. Development should be between 
18 and 24°C (64 and 75°F) and preferably at 20°C (68°F). Development 
should not be undertaken at above 24°C (75°F) without special pre- 
cautions (see preceding section), or, owing to the inactivity of the de- 
veloper, below 18°C (64°F). 



TEMPERATURE 


DEVELOPING 


TIME (minutes) 


°C 


°F 


DX-80 


D-19 


24 


75 




H 


22 


72 


3 


4 


21 


70 


H 


4J- 


20 


68 


4 


5 


19 


66 


4i 


5i 


18 


64 


H 


6 



Uniformity of development : If an exposed film is suspended in a still 
tank of developer and left undisturbed throughout the whole of the period 
of development, the resulting radiograph will be unevenly developed 
and may show so-called bromide flow-marks or "bromide streamers". 
These flow-marks show up as light areas below very dense images or 
as dark areas below very light regions in the image. (An example of 
uneven development is shown in Figure 14 in Data Sheet XR-7.) 

When the films are first immersed in the developer, they should be 
vigorously agitated up-and-down and to-and-fro for a few seconds to re- 
move air bubbles, (vigorous lateral movements of the film should be 
avoided or the film may escape from the hanger, especially with some types 
of channel hangers). Thereafter, this brief agitation should be repeated 
every minute until development is complete. 

The degree of agitation affects the rate of development and once a 
satisfactory procedure has been established it should be adhered to. 
Obviously, if any of these methods are to be of value the developer must 
be free from sediment and particles of dirt, otherwise these may find their 
way on to the surface of the emulsion. 



XR-6 



Replenishment 

Normally, a large number of films may be developed in a tank of solution, 
and every film uses up some of the active chemicals. At the same time 
soluble halides accumulate and, in time, will noticeably retard develop- 
ment. As each film leaves the developer, it carries a little liquid with it 
and the level in the tank gradually falls. If, however, the tank is replen- 
ished at regular intervals, the activity of the developer is maintained; 
the replenisher is so compounded that it re-activates the developer. Do 
not top up with water or alter the processing procedure to compensate 
for loss of activity of the developer. 

Provided that the correct replenishment is being used, the developer 
may be used to the extent of at least 100 per cent replenishment, i.e., 
a total volume of replenisher equal to that of the original working-strength 
developer may be added before the solution need be discarded. In any 
case, the developer should be discarded after two months. 

Control strips (step wedges) can be produced* and then used to test 
the developer at intervals. If one is processed when the developer is 
fresh, a standard for comparison of future tests can be established. The 
later tests can then be compared with the original test either visually or, 
more accurately, using a densitometer. 

Methods of Replenishment : The function of developer replenishment is 
two-fold : (a) to maintain the developer at the initial state of activity, and 
(b) to replace the solution lost by carry over. 

Two systems of developer replenishment are currently used with DX-80 
developer and one with D-19 developer and these are: 

I Replenishment of DX-80 developer by volume related to type of radiograph 
and draining time : Replenishment should be carried out as often as 
necessary to keep up the level of the developer. The strength of the 
DX-80R replenisher to be used depends on: 

(a) the average density of the radiographs, and 

(b) the amount of solution carried over, i.e., the draining-back time. 
Where radiographs are drained back for 5 to 10 seconds, the strength 
of the replenisher as related to average density is given in the following 
table : 



AVERAGE DENSITY 


STRENGTH OF REPLENISHER 


Less than 1 


l+4± 


Between 1 and 2 


1+4 


Between 2 and 3 


\+H 


Over 3 


1+3 



Where no draining back is practised, it may be necessary to dilute the 
replenisher further. 

2 Replenishment of DX-80 and D-19 developers by volume related to 
area processed : With this method the radiographs should have a consistent 

* Consult the appropriate Sales Department of Kodak Limited. 

7 XR-6 



density and a record must be kept of the area of film processed. Re- 
plenishment should be carried out at a predetermined square footage 
whether or not the level has dropped significantly. 

Using DX-80R replenisher, it may be necessary to remove some of the 
developer to accommodate the required quantity of replenisher made up 
1 + 4. Replenish at a rate of 1 fluid ounce per square foot of film pro- 
cessed (approx. 300 ml per square metre). Alternatively instead of 
removing developer to make room for replenisher, the replenisher may 
be made up to 1 + 3 or 1 + 3|. This gives the necessary quantity of 
replenisher concentrate. 

D-19R replenisher is a normal-strength replenisher, therefore the 
method of varying the strength of the solution cannot be utilized. It 
will be necessary in most cases where thorough draining-back is practised 
to remove some solution before adding the replenisher. Replenishment 
by topping up to the predetermined level is not really satisfactory unless 
the drop in level allows just the right amount of replenisher to be added. 
Use the replenisher solution undiluted, at the rate of 1.5 fluid ounces 
per square foot of film processed (460 ml per square metre). 

Stop bath or rinse 

Before the film is transferred to the fixing bath it should be rinsed in a 
solution of 'Kodak' Indicator Stop Bath, or individually in either running 
water or a spray rinse. Rinsing may also be carried out in an acid stop 
bath, such as a solution made up to Kodak formula SB-1 (for formula 
see Data Sheet FY-4), but the stop bath must be renewed periodically 
in accordance with the number and size of films to be rinsed. The 
'Kodak' Processing Unit P3 is fitted with a rinse compartment which may 
be located to suit the desired working arrangement (rinsing is carried 
out using the "running rinse" principle). 

Fixing 

After development is completed, the undeveloped, but still light- 
sensitive, silver halide crystals remaining in the emulsion must be 
removed in order to prevent them from darkening as a result of light 
action, and so obscuring the image. Fixing is accomplished by immersing 
the film in a solution containing either sodium thiosulphate (hypo) or 
ammonium thiosulphate, both of which form soluble compounds with 
the silver halide. 

Besides the fixing agent, an X-ray fixing bath usually contains an acid, 
such as acetic acid, a preservative such as sodium sulphite, and a hardening 
agent such as potassium alum. The acid is added to neutralize the alkali 
in the developer carried over in the emulsion. The sodium sulphite is 
necessary to prevent the fixer from being decomposed to sulphur by the 
acid. The alum is added to harden the gelatin of the emulsion in order to 
prevent softening in the wash water or when drying by heat. The 
hardened film is not only mechanically stronger, but dries more quickly 
than unhardened films. 

To ensure complete fixing and efficient hardening, it is necessary at 
normal temperatures to fix the materials for at least 3 minutes with a 
rapid liquid fixer, or 5 minutes with fixing powders. 

XR-6 8 



The fixing bath becomes exhausted, as the number of films put through 
increases, for one or more of the following reasons : 

1 The concentration of the fixing agent becomes reduced by the carry 
over of stop bath or rinse water into the fixing bath. 

2 The developer carried over by the film gradually neutralizes the acid 
in the fixing bath. This may produce a sludge of insoluble aluminium 
compounds which will, in time, render the bath useless. It also leads to 
the eventual loss in the hardening properties of the bath. 

3 The by-product of fixing is the formation of silver complexes, the 
concentration of which determines the life of the fixer. 

The usual criterion of exhaustion of the fixer is the time taken to 
clear the emulsion of all milkiness. When this has doubled over the 
time taken in the fixing bath when fresh, then the fixing bath is regarded 
as exhausted. 

It should also be noted that if the concentration of the silver complexes 
in the fixer becomes too high, it will not be possible to wash them out 
of the emulsion completely. 

The use of 'Kodak' FX-40 X-ray Liquid Fixer with 'Kodak' HX-40 
X-ray Liquid Hardener is recommended when radiographs are required 
very quickly; this may be used just to clear the film which may be re-fixed 
subsequently if it is required to be kept. To prepare a working-strength 
solution, dilute the FX-40 fixer and add the HX-40 Hardener. 

Kodak 'Unifix' Powder is an acid hardening fixer available as a packed 
chemical in single-powder form. Make up a working strength solution 
according to the instructions packed with it. 

Radiographers who prefer to make up their own fixing bath should 
use Kodak formula F-5 (see Data Sheet FY-4). 

Time and temperature of fixing : For the best results and the most efficient 
fixing, use two successive fixing baths. Clear the film of all milkiness 
in the first bath, and drain back for 10 seconds. Then fix in the second 
bath for the same time as was needed in the first, and drain back for 10 
seconds. When the first bath fails to clear the film in twice the time taken 
to clear in a fresh bath, replace the first bath with the second bath, and 
make up a fresh second bath. Repeat this procedure until the first bath 
has been replaced four times, i.e., five sets of first and second baths have 
been used to their capacity. Then discard both baths and restart with a 
fresh pair of baths. 

If a single fixing bath is used, fix for twice the time taken to clear. 
Discard any fixing bath when it fails to clear the film in less than twice the 
time taken to clear in a fresh bath. 

The clearing time depends on whether the sodium or the ammonium 
thiosulphate is used as the fixing agent, its concentration, the temperature 
of the solution and the amount of use. 

It is desirable to maintain the fixer at approximately the same tempera- 
ture as the developer, preferably within the range 18-24°C (64-75°F). 
In the 'Kodak' Processing Unit P3 the solutions are, of course, housed 
within tempered water jackets. 

9 XR-6 



Washing 

After all the undeveloped silver halide has been removed, the emulsion 
is still saturated with the chemicals of the fixing bath and other by-products 
of processing. If the fixer were allowed to remain, it would slowly 
decompose and attack the image, causing it to become discoloured and 
faded. To prevent this, the fixer and by-products must be removed by 
washing. 

For moderate-term storage requirements — up to approximately 10 years 
— the radiograph should be washed for 10 minutes at not less than 10°C 
(50°F), in running water which is being changed at a minimum rate of 
4 changes per hour. Under the same conditions, radiographs which are 
required to be kept for longer storage periods should be washed for 
20 minutes. At lower temperatures, or with less efficient washing equip- 
ment, these times may have to be increased considerably. When a low 
degree of permanence is acceptable, e.g., when the radiograph is to be 
kept for only a very short period, these times may be reduced. Full details 
of recommendations necessary to ensure permanence may be found in 
Data Sheet XR-5. 

The risk of drying marks may be obviated and drying hastened, 
by rinsing for 30 seconds in Kodak 'Photo-Flo' solution, at the dilution 
recommended. 

Drying 

Drying has an important bearing on the quality of the finished radio- 
graph. It should be done without causing any mechanical damage to the 
emulsion or marks from uneven drying, and without exposing the moist 
emulsion to dust or lint which, once attached, is practically impossible to 
remove. 

The film should be hung up to dry in a dust-free atmosphere. Nothing 
must touch the emulsion surface until it is entirely dry. When it is 
wet, or even damp, the surface is delicate and easily marked. After 
drying has started, the film should not be moved or shaken, since water 
drops shaken from the film hanger on to the partly dry emulsion are 
almost certain to cause drying marks. Heat can be used to hasten drying 
when there is provision for a rapid flow of clean air across the emulsion 
surface, as in the 'Kodak' Drying Cabinet Model B, Series 2. 

Where films are removed from hangers for drying and are hung up 
from the corners or from one end — a common practice — sufficient room 
must be left between them to avoid any risk of the films touching each 
other as a result of curling which may take place during this method 
of drying. The use of 'Kodak' Film Hanger Bars is recommended 
under these circumstances. 

Cleaning developer hangers and tanks 

The quality of the result depends so much on the cleanliness of the 
work that the following cleaning formulae for hangers and tanks should be 
noted. 

For hangers and clips use a solution of 6 fluid ounces of 80 per cent 
acetic acid in sufficient water to make 80 fluid ounces (75 ml to make 1 litre) 

XR-6 10 



of solution. Soak the articles in this for one hour and scrub in clean 
water. 

Deep tanks should be scrubbed thoroughly with clean water, preferably 
by means of a double-sided brush, which should be reserved for this 
purpose. It is advisable to sterilize the developer tanks occasionally, 
especially during warm weather, in order to prevent bacterial growth. 
Bacteria may cause sulphite to change to sulphide, which will then fog 
undeveloped film. The tanks may also be cleansed with a solution of 
sodium hypochlorite, or household bleaching solutions may be used. 
Tanks which have been sterilized must be thoroughly washed before use. 

SILVER RECOVERY AND FIXER REGENERATION 
Manual processing 

An exhausted X-ray fixing bath may contain approximately 1 to 1.5 
troy ounces of silver per gallon (6 to 10 grammes per litre), depending 
upon the maximum clearing time that can be tolerated. The high price 
of silver makes its recovery worth while. However, apart from the 
economic reason, the silver content of the fixer should be kept at a mini- 
mum to give permanence to the radiographs on storage. 

The useful life of the fixing bath may be extended by the practice of 
fixer regeneration — full details of this and methods of silver recovery are 
given in Data Sheet PR-9. 

Automatic processing 

The fixing section in the 'X-Omat' Processors employs a fixer and 
replenisher system, the spent fixer running to waste. Therefore, fixer 
regeneration is not employed and a destructive method of silver recovery, 
such as the steel-wool method, is favoured, as it is undesirable to re-use the 
fixer. For further details see Data Sheet PR-9 and Fundamentals of 
Radiographic Photography, Book 5. 



This Data Booklet does no more than summarize what is believed to be 
the best procedure at each stage and, if fuller information is required on 
any of the photographic aspects of radiography, enquiry should be made 
of Professional, Commercial and Industrial Markets or Medical Markets 
of, Kodak Limited, London. 



BIBLIOGRAPHY 

Industrial Radiography, Kodak, 1965. 

D. H. O. John, Radiographic Processing, Focal Press, 1967. 

Fundamentals of Radiographic Photography, Kodak, 1968. 

Glossary of Terms used in Radiographic Photography, Kodak, 1968. 

D. N. & M. O. C. Chesney, Radiographic Photography, Blackwell, 1969. 

1 1 XR-6 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

BLUE BRAND 

INDUSTREX 

PHOTO-FLO 

ELON 

X-OMAT 

UNIFIX 



Kodak Data Booklet KODAK LIMITED LONDON 

XR-6 

PDXR-6/xWP I 1/3-71 



FAULTS IN PROCESSING X-RAY FILMS 



It is not always an easy matter to determine what is the cause of blemishes 
or artifacts on a radiograph. Very often the X-ray film is held responsible 
for faults which are, in fact, due to incorrect processing procedures. 

To assist radiographers in identifying such adventitious images, com- 
monly occurring defects produced during handling or processing are 
illustrated in this Data Sheet. All these defects have been deliberately 
produced on radiographs of the same subject, as being less confusing than 
would be a similar series collected on different occasions. It must be 
emphasised, however, that although many of the defects are strikingly 
obvious, the causes listed under each are frequently unsuspected by 
operators new to the practice of radiography. The illustration below is 
made from a properly processed radiograph of a magnesium-alloy casting 
and can be used as a standard when examining the subsequent illustrations . 




FIGURE I. NORMAL RADIOGRAPH of a light alloy casting. 



Kodak Data Sheet 
XR-7 




FIGURE 2. "WHITE" PRESSURE MARKS (i.e. locally desensitized areas) can be produced by 
pressure on, or buckling of, X-ray film before exposure; large sheets of film are more likely to 
be buckled by careless handling than the smaller sizes. "Black" pressure marks can be produced 
by pressure or buckling after exposure (see Figure 3). 




FIGURE 3. "BLACK" PRESSURE MARKS. Pressure or buckling of X-ray film after exposure 
and before processing sometimes results in the affected area developing to a higher density than 
the surround (see also Figure 2). 



XR-7 




FIGURE 4. CRACKS, SCRATCHES AND SPOTS IN THE INTENSIFYING SCREEN 
interfere with the fluorescent light emission of the screen and will be recorded on the film as 
reduced density at the points corresponding to these regions (indicated by arrows). 




FIGURE 5. PRINTED PAPER BETWEEN SCREEN AND FILM DURING EXPOSURE. 
Any substance or material (a paper leaflet in the example shown) lying between the screen and 
film absorbs the light emitted by the screen. In the above radiograph the light from the screen 
is absorbed by the black letters, whereas it was partly transmitted by the paper. The image of 
dust particles between the screen and the film will often record on the film for the same reason. 

5 XR-7 




FIGURE 6. GREASY FINGER MARKS BEFORE PROCESSING. If the film is touched by 
greasy fingers before processings the developer will penetrate the greasy patches relatively slowly 
and these areas will be under-developed and therefore appear bright in the radiograph. 




FIGURE 7. PREVIOUS EXPOSURE TO X-RAYS. Overall fog and images other than that given 
by the specimen maybe superimposed on the radiographic image if a film is exposed accidentally 
to X-rays. It sometimes happens that films are accidentally placed too near to the X-ray plant 
or to a source of gamma-rays and spurious images appear on the films. The accumulated effect 
of several exposures may result in an image on a film even when it is kept at a considerable 
distance from the X-ray source. 



XR-7 




FIGURE 8. RETICULATION. A net-like structure which is generally caused by differences 
in temperature between the processing baths, the rinsing or the washing water. Serious reticu- 
lation shows as a roughening of the surface of the emulsion. Often, however, it appears only 
as a microscopically fine structure and the image then appears "grainy". Its appearance under 
a low-power magnifying glass is, however, quite typical. 




FIGURE 9. EXPOSURE TO FAULTY SAFELIGHT causes general fog. If the film is fogged 
when lying on a reflecting material an image of this material may record on the film as a result of 
light passing through the film and being reflected back (cf. Reflex Printing). Safelight lamps should 
be examined periodically to check that the safelight and its housing do not transmit any unsafe 
light. Deliberate exposure of a piece of film, part of which is protected by black paper, for 
1 minute at 3 ft from the safelight is the simplest test: fogging of the exposed area of the film 
indicates unsafe safelighting. (Data Sheet XR-6). 



XR-7 







BR 


1 


I 




1 


















*PPr 






IlilLs. 




H^^^^H 




^^^^^^^^^Bfl 






WfP^T, , .;• * . 




^^^^^B 


■ 


















|||a|||j| 


BH^H 


IB 






HHItlfl 




^^■■H 
























Jk 


.*-• 












U. 


• 

fflHHlL„ 


1 



FIGURE 10. SPLASHES OF DEVELOPER BEFORE DEVELOPMENT OF WHOLE FILM 
BEGINS. Splashes of developer on an exposed film will start development at the points affected 
and these will show up as darker areas on the final image. 




FIGURE II. WATER DROPS ON DRY FILM AND ACCIDENTAL EXPOSURE TO 
LIGHT BEFORE PROCESSING. If water drops on to a dry film after exposure, but before 
processing, it is advisable to bathe the whole film in water, in order to wet it uniformly, other- 
wise the water droplets will result in weaker images at these points. If the film is exposed to 
white light while covered with the water droplets these will act as lenses and produce contour lines 
as shown in the illustration. 



XR-7 




FIGURE 12. SPLASHES OF FIXER BEFORE DEVELOPMENT OF FILM BEGINS. Films 
should be always handled on a dry bench whilst loading and unloading cassettes. Splashes of fix- 
ing solution on the dry film cause clear spots on the film. Exposed and unexposed silver bromide 
is dissolved by the fixing solution and no image will develop on these particular areas. 




FIGURE 13. SILVER REDUCTION THROUGH CONTAMINATION BY METAL FIL- 
INGS IN THE DEVELOPER. Metals in the form of dust or filings should not be allowed to 
fall in the developing tanks, as they may lead to silver precipitation in the emulsion during 
processing. 



XR-7 




FIGURE 14. UNEVEN DEVELOPMENT, 
agitation development is uneven. 



If films are developed in a tank without adequate 




FIGURE 15. SOLARISATION. Prolonged exposure to a faulty safelight during development 
sometimes produces an actual reversal of the image tones; in addition, this film has been 
splashed with developer prior to development. The lighter streaks below dense areas (indicated 
by arrows) are caused by the liberation of soluble bromide which by flowing down from the 
fully exposed regions restrains development locally. It is clear that the left-hand portion of the 
radiograph was at the top of the tank. 



Kodak Data Sheet 
XR-7 



KODAK LIMITED LONDON 

PDXR-7/rIWP2/l2-70 



TROPICAL PROCESSING 
OF 'KODAK' X-RAY FILMS 



X-ray processing techniques used for normal temperatures may, with 
'Kodak' materials and formulae, be used with safety at temperatures up to 
24°C (75°F). The recommendations outlined below, however, are 
intended as a guide to the techniques found, by practical tests in the 
laboratory and in the tropics, to be most suitable for the temperature 
range 24°-32°C (75°-90°F). 

Under such conditions, it is still possible to obtain results of the highest 
quality, provided the development time is adjusted to give the correct 
degree of contrast and methods are adopted for minimizing the degree of 
swelling and softening of the emulsion on the film. This can best be 
achieved by the addition of a fairly high concentration of a neutral chemical 
(such as sodium sulphate) to the developer. At the same time, a reduction 
in the time for which the film is subjected to the various processes, particu- 
larly development and washing, is advantageous for preventing undue 
swelling. The various solutions and the times for which they should be 
used, are given below. 

The recommendations given in this Data Sheet should be used only 
when it is impracticable to cool the solutions and to maintain them at a 
more normal level of temperature. 

Recommendations for other aspects of photographic work in the tropics 
will be found in Data Booklet GN-5. 



PROCESSING TEMPERATURE RANGE: 24°— 32°C (75°— 90°F) 

Development: The standard ranges of developing times for X-ray films 
in normal (non-sulphated) D-19 developer at 20°C (68 C F) are given 
below : 



Tndustrex' Type D 5 min 



'Crystallex' 
'Microtex' 



5-10 min 
5-15 min 



'Kodirex' 
'Royal Blue' 
'Blue Brand' 
Standard 



► 5 min 



For the higher temperatures, sodium sulphate should be added to the 
developer, whether it be D-19 or DA- 19b (the equivalent of D-19 
specially packed for the tropics), in the proportions shown in the following 
table. The developer solution should be stirred continuously while the 
sodium sulphate is being added and until it is completely dissolved. 



Issue C 



Kodak Data Sheet 
XR-8 



RANGE OF 
TEMPERATURES 


QUANTITY OF SODIUM SULPHATE 
(anhydrous)* 




Per 80 fluid ounces 


Per litre 


24°-27°C (75°-80°F) 
27°-29°C (80°-85°F) 
29°-32°C (85°-90°F) 


4 ounces 
6 ounces 
8 ounces 


50 grammes 
75 grammes 
100 grammes 



* If crystalline sodium sulphate (decahydrate) is used in place of anhydrous, multiply the weights given 
by2i. 

The required developing time in the unsulphated developer being 
known for a temperature of 20°C (68°F), the times required for sulphated 
D-19 or DA-19b at temperatures of 24°-32°C (75°-90°F) may be found 
in the body of the table below. 



DEVELOPING 

TIME (MINUTES) 

IN NON- 

SULPHATED 

D-19 OR DA-I9b 

AT 20°C (68°F) 


CALCULATED DEVELOPING TIME (MINUTES) 
IN SULPHATED D-19 OR DA- 19b 


24°C (7S°F) 


27°C (80°F) 


29°C (85°F) 


32°C (?0°F) 


5 

7 

8 

12 


6 

H 
14 


4* 

7 
I0i 


3 

4f 

7 


2* 



Stop bath: The use of a hardening stop bath, made up according to 
Kodak formula SB-4 (see Data Sheet FY-4), is recommended between 
developing and fixing, particularly in the range 29°-32°C (85°-90°F). The 
film should be immersed for 3 minutes; for the first 30-45 seconds, it 
should be agitated vigorously, otherwise streakiness may result. After the 
equivalent of seven 14 x 17 inch films per gallon (six 35.6x43.2 cm films 
per 4 litres) have been treated, the bath should be replaced, otherwise 
scum markings will result. 

If excessive swelling is noticed, the stop bath may be prepared in more 
concentrated form by using only 75 per cent of the quantity of water stated 
in the formula. 

Fixing and washing: The following 'Kodak' fixers are recommended — 
FX-40 X-ray Liquid Fixer with HX-40 X-ray Liquid Hardener, 'Unifix' 
Powder, or a solution made up to Kodak formula F-5 or F-6 (see Data 
Sheet FY-4). At the above temperatures, all types of film should be 
fixed for not less than 10 minutes, and washed for 30 minutes. 

To prevent the formation of mould growth, the film may be rinsed for 
3 minutes, after washing, in an aqueous solution of |-1 per cent zinc 



XR-8 



fluosilicate*, and dried without wiping. To aid rapid and even drying, 
and to obviate drying marks, Kodak 'Photo-Flo' solution may be added 
to this solution in the dilution normally recommended — the resultant 
solution will not be clear but its properties will not be impaired. 

*Zinc fluosilicate is a poison which may be fatal if swallowed even in 
dilute solution. The dust or spray of this chemical should not be inhaled, 
and the hands should be thoroughly washed after each contact with it. 



XR-8 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

KODIREX 

BLUE BRAND 

CRYSTALLEX 

INDUSTREX 

MICROTEX 

PHOTO-FLO 

UNIFIX 
ROYAL BLUE 



Kodak Data Sheet KODAK LIMITED LONDON 

XR-8 

PDXR-8/rlWP2i/l-70 



MEDICAL APPLICATIONS 



CONTENTS EDITION 

MD-2 Infra-Red Photograph/ in Medicine Issue 8 

MD-3 Photographing Pathological Specimens Issue C 

MD-4 Cine-Fluorography, Spot Filming and Kinescopy Issue D 

MD-5 Tomography Issue B 



Associated Data Sheets in this or other volumes or sections 

1, GN-2 Copying Radiographs and Other Transparencies 

2, XR-2 Penumbral Unsharpness 

2, XR-3 Localisation in Radiography 

2, XR-5 The Storage of X-ray Films and Radiographs 

2, XR-6 Processing X-ray Films 

2, XR-7 Faults in Processing X-ray Films 

2, XR-8 Tropical Processing of 'Kodak' X-ray Films 

2, IN-12 Contact Microradiography 

2, SC-6 Recording Thin-Layer Chromatograms 

2, SC-7 Infra-Red Photography 

2, SC-8 16 mm Cine-Micrography 

2, SC-IO Autoradiography 

3, CL-7 Problems in Colour Photography 

3, CL-8 Colour Photography by Artificial Light 

3, CL-9 Colour Photography and the Human Eye 



Kodak is a trade mark KODAK LIMITED LONDON 

PDDB-31/xWP9±/IO-7l 



INFRA-RED PHOTOGRAPHY IN MEDICINE 

Revised by Raymond J. Lunnon, A.I.B.P., F.R.P.S. 



Applications of infra-red photography in medicine were first reported in 
1933 by Haxthausen of Copenhagen, who had found it of value in the 
study of dermatology. 

Since that date research has broadened the scope of medical infra-red 
photography and it has become a useful diagnostic technique. 

The following applications are dealt with in greater detail in Clark's 
Photography by Infrared and Gibson's Photography of Patients (see 
Bibliography). Both publications give a comprehensive survey of the 
applications and techniques of this type of photography, together with 
extensive references. 

The technique of general infra-red photography is dealt with in Data 
Sheet SC-7. 

For full details of the applications and techniques of infra-red photo- 
graphy in medicine, the Eastman Kodak Data Booklet No. N-l entitled 
"Medical Infrared Photography" may be obtained from Kodak Limited. 

Some applications 

The Superficial Venous System: This is revealed by infra-red photo- 
graphy, which will demonstrate : — 

1 The characteristic changes in the venous network of varicose conditions. 

2 The marked dilation of the superficial veins of the breast due to chronic 
cardiac compression. 

3 The development and retrogression of the superficial mammary and 
abdominal venous circulation in human pregnancy. 

Dermatology: Diseases of the skin, hidden by scab, are revealed by infra- 
red photography which, among other applications, will reveal the progress 
of treatment in eczema and lupus. 




Photograph of chest on panchromatic 
material 

Issue B 



Same subject photographed on infra-red 
plate by infra-red rays 

Kodak Data Sheet 
MD-2 



Infra-red Photography of the Eye: This offers the opportunity of examin- 
ing the iris through an opaque cornea (as in keratitis parenchymatosa) 
when the state of the pupil, the presence of synechiae and the existence of 
any defects in the iris, either congenital or operative, are revealed. 

If atrophy begins in the iris, resulting in destruction of the pigment and 
its replacement by greyish white tissue, a photograph made by infra-red 
shows this region of atrophy as darker than the normal tissue of the iris. 

Infra-red photography has also proved of value in measuring the size of 
the pupil in the study of dark adaptation, since infra-red radiation has no 
apparent effect on the pupillary diameter. 

Infra-red Photography of Gross Specimens: This has been used in studies 
of tumour in the stomach and of silicotic areas in the lungs. Details of 
the technique are given in Data Sheet MD-3— "Photographing Patholog- 
ical Specimens". 

Recommended materials 

1 Kodak 'Ektachrome' Infrared Film for infra-red colour photography 
(see Data Sheet FM-IH). 

2 'Kodak' Spectroscopic Plate Type I-N and Type I-Z (see Data Booklet 
SE-3). 

3 'Kodak' Infrared Film (35mm) and 'Kodak' High Speed Infrared 
Film (sheet and 35mm) for black-and-white infra-red photography. 
Storage Recommendations: Details on the storage of these materials and 
methods of improving their shelf-life, are given in Data Sheet RF-6. 

Recommended apparatus 

I 'Kodak' Specialist Camera, or other suitable technical camera, and 
Photoflood lamps. 





Normal photograph of leg with 
•varicose veins 



Infra-red photograph of same leg 



MD-2 



2 'Wratten' Filters No. 87 (transmit from 740 nm) and No. 88A (trans- 
mits from 720 nm). 

3 Flashbulbs may be required for certain applications, such as close-up 
infra-red work. Suitable infra-red coating techniques for clear flash- 
bulbs are given in the first reference in the Bibliography. 

Bibliography 

R. B. Morris and D. A. Spencer, Dazzle-free Photoflash Photography, 

Brit. J. Phot., 14 June 1940. 
H. Haxthausen, " Infrarotes" Photographieren in der Dermatologie, Derm. 

Wschr., 97, 1933, p. 1289. 
H. Haxthausen, Infra-red Photography of Subcutaneous Veins : Demonstra- 
tion of Concealed Varices in Ulcer and Eczema of Leg, Brit. J. Dermat., 

45, Dec. 1933, pp. 506-511. 
L. C. Massopust, Infra-red Photographic Study of the Changing Pattern of 

the Superficial Veins in a Case of Human Pregnancy, Surg. Gynec. and 

Obstet., 63, July 1936, pp. 86-89. 
L. C. Massopust, Infra-Red Photography, J. Biol. Photogr. Ass., 13, Mar. 

1945, pp. 139, 145. 
H. L. Gibson, Infrared Photography of Patients, Radiogr. Clin. Photogr. 

(Rochester, N.Y., U.S.A.), 1945, 21, p. 72. 
W. Clark, Photography by Infrared, Chapman & Hall, 2nd edition, 1946. 
L. C. Massopust, Infra-red Photographic Study of the Superficial Veins of 

the Thorax in Relation to Breast Tumours, Surg. Gynec. and Obstet., 

86, Jan. 1948, pp. 54-58. 
K. Bowes, Clinical Aspects of Infra-Red Photography, Photogr. J., 90B, 

May-June 1950, pp. 63-65. 
L. C. Massopust and W. D. Gardner, Infra-red Phlebogram in the Diagnosis 

of Breast Complaints, Surg. Gynec. and Obstet., 97, Nov. 1953, pp. 

619-626. 
C. E. Engel, Present day materials for Infra-red Photography, Med. Biol. 

Illus., 8, 1958, pp. 89. 
H. L. Gibson, Photography of Patients, Charles C. Thomas, (Springfield, 

Illinois, U.S.A.), 2nd edition, 1960, pp. 165-184. 
P. Hansell and R. Ollerenshaw, Longmore's Medical Photography, Focal 

Press, 7th edition, 1962, pp. 334-337. 
H. L. Gibson, W. R. Buckley and K. E. Whitmore, New Vistas in Infrared 

Photography for Biological Surveys, J. Biol. Photogr. Ass., 33, No. 1, 

Feb. 1965, pp. 1-33. 
H. L. Gibson, Further Data on the Use of Infrared Color Film, J. Biol. 

Photogr. Ass., 33, No. 4, 1965, pp. 155-156. 



MD-2 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

W RATTEN 

EKTACHROME 



Kodak Data Sheet KODAK LIMITED LONDON 

MD-2 

PDMD-2/xWPI0/9-7l 



PHOTOGRAPHING PATHOLOGICAL SPECIMENS 

By courtesy of Norman K. Harrison, F.I. I. P., F.R.P.S. 



The photography of pathological specimens is often a routine procedure in 
departments of medical photography, and various methods have been evol- 
ved to meet the demands of the pathologist who desires to have a permanent 
record of the specimens with which he is constantly called upon to deal. 

In photographing medical specimens, it is essential that there should 
be a plain delineation of structure, and of any growths or malformations 
for which reason the specimen was removed from the body. However 
good the result may be from a photographic point of view, it is useless 
unless it shows just what the pathologist requires. 

In those departments where specimen photography is a routine, it is 
advisable to standardize the equipment and method so that the greatest 
amount of work may be done with the least effort. Experience has shown 
that the great majority of specimens lend themselves to photography by 




Figure 



Issue C 



Kodak Data Sheet 
MD-3 



a more or less standard technique; accordingly, these can be rapidly 
photographed and disposed of, and attention then concentrated on those 
which call for more time and detailed treatment. 

It is now generally accepted that a photograph of a pathological speci- 
men, of whatever size, should show full detail of the subject, but should 
not be marred by obtrusive background, or its shape confused by shadow 
casts. To obtain this shadowless background, some workers 1 have pinned 
or fastened a specimen straight from the fixing solution on to a board, 
and after it has been photographed the negative has been blocked-out. 
A less time-consuming and better result may be obtained by trans- 
illumination, so that the shadowless background is obtained without any 
need for afterwork on the negative. 

Some quite elaborate pieces of apparatus have been made for specimen 
photography, and some very simple improvisations have proved successful. 
Thus a transparency illuminator laid on its back — Figure 1 — will provide 
adequate trans-illumination for small specimens, while a whitened box 
fitted with rheostat-controlled Photoflood lamps in the corners, and with 
larger Photofloods to illuminate the specimen, has also been used. 2 Many 
of these improvisations fail when confronted with a specimen which is 
out of the ordinary, and for a department catering for the needs of a 
general hospital it is advisable to have a piece of apparatus which will 
cover all possible requirements. 




Figure 2 



MD-3 



Such a piece of apparatus is the specimen photography table as shown 
in Figure 2; it is simple to construct from Dexion angle material and can 
easily be adapted to provide coloured backgrounds, should colour photo- 
graphy of fresh or fixed specimens be undertaken. It is advisable for the 
table to be of such size that the longest bone in the body can be photo- 
graphed without loss of background illumination at the bone ends, and 
to avoid background retouching. An ideal size of table would be 42 x 30 
inches, for this would allow a femur or a full-length spine to be photo- 
graphed without trouble. A table of such a size would also allow large 
internal organs, such as the complete colon, from ileo-caecal valve to 
start of rectum, or the stomach, with other organs and mesentery attached, 
to be photographed without afterwork on the negative. The blocking- 
out of negatives should, if possible, be avoided. 

In all cases of specimen photography it is advisable to include some 
form of scale so that the size of the specimen may easily be assessed, 
whether viewed as a print, of any size, or as a projected image. This 
scale should be clear and bold, and its zero should be in line with the 
left-hand edge of the specimen, so that no calculations are needed to 
determine the specimen size. In scientific work it is usual to use metric 
measurements. The inclusion of a familiar object, such as a matchbox, 
as an indication of size is out of place in a scientific photograph, however 
desirable it may be 
in an illustration for a 
popular journal. For 
trans-illuminated work 
transparent scales may 
be used, but for some 
coloured work it may 
be necessary to use a 
black scale with white 
figuring. Care should 
be taken to see that the 
scale is placed at the 
level of critical focus — 
a point which may be 
overlooked when 
photographing a 
specimen which on 
account of its thick- 
ness, or uneven sur- 
face, demands the 
maximum depth of 
field. To hold the 
scale above the surface 

of the table and at r .o rr a 

the level of critical jjl ~ 
focus, a small retort ' ' ' ' ' 
stand and clamp will 
be found effective, 
for the clamp jaws Figure 3 




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4.12 3 4 3 6 7 I 



llll|llll|llll|lllljllll|llll|llll|lllllllll|lllllllll|lllljllll| 



lllll|lllllllll|lllljll 



MD-3 



^3 



fSfH 



•>*^ji 



*r»j 



s^rf* 




li|:i|:::il|llll ,,|il :n:' !!!M. 



Figure 4 



iiiiiii|iiii|iiii| 



will grip the scale by 
its edge and need 
not appear in the 
final print, although 
they are shown, by 
way of illustration, 
in Figure 3. 

When photo- 
graphing a number 
of specimens which 
are very similar in 
appearance, it is a 
good plan to include 
in the negative area 
a small card on 
which can be written 
the name or number 
of the patient. This 
is not included when 
the final print is 

made, but its presence on the negative allows easy identification of the 
specimen and it cannot be mislaid; this also is illustrated in Figure 3. 

Lighting should be such that full detail is revealed, and dense, detail- 
less shadows avoided. Two 500 watt Photopearl (3200K) lamps, 
or two No. 2 Photoflood lamps, one at each end of the table, are sufficient 
for the great majority of specimens, and it should be possible to raise 
the lamps to light any undulations in a more or less flat surface, without 
edge shadows. A spotlight is a useful accessory to pick out any detail 
or to light up a shadowed area. Owing to the difference in lighting 
value between the top lighting and the lighting below the specimen, it 
may be necessary to increase the exposure time of the background lighting 
to ensure that a pure white background is achieved. Once this ratio 
of front to back lighting is worked out, exposure on the great majority of 
specimen work can become a matter of routine. Despite what might 
be expected, light-coloured specimens photograph admirably against the 
trans-illuminated background, and even brain slices as illustrated in 
Figure 4, for which some workers use a black background, are better 
photographed by trans-illumination, and, owing to the lower overall 
contrast, will reproduce much better this way. 

Specular reflections may cause some difficulty, and to what extent they 
may be permitted is often a matter of personal opinion. While a certain 
amount may give a more natural appearance, too many reflections can 
conceal detail and mar the general appearance. Many workers have given 
considerable thought to this problem, and the use of 'Pola'-screens, 
immersion in water or other fluid, and the use of enclosing screens to 
obtain diffusion of illumination, are among methods suggested. Martinsen 3 
has reviewed a number of these techniques. 

Infra-red photography of a specimen will sometimes show details 
which other photographic emulsions fail to reveal. Mills 4 has shown the 



MD-3 



value of infra-red in demonstrating silicotic nodules in lung tissue, and 
Clark 5 has reviewed the field of infra-red in this connection. 

While the photography of a fixed specimen is commonly undertaken 
with a monochrome material, it is highly desirable, in fact almost impera- 
tive, that fresh specimens, straight from the operating theatre or post- 
mortem room, should be photographed in colour. The required coloured 
background can be obtained either by placing the specimen on a coloured 
surface, such as a sheet of glass over a sheet of blotting paper of the 
appropriate hue, or direct on to a piece of coloured material, or, when 
using the specimen table, by interposing a sheet of transparent coloured 
glass or other material between the diffusing screen and the support on 
which the specimen rests. The choice may be determined by the method 
of top lighting used. 

Combination of specimen and radiograph 

In this technique it is usually required to show the specimen alongside 
its image — or superimposed over its image — on a pre-operative radio- 
graph, and the use of the specimen table makes this easily possible. The 
radiograph is laid on the table, over it is placed a thin sheet of clear glass, 
and on this is placed the specimen in the appropriate position. The 
radiograph is trans-illuminated and the specimen is lit by the usual top 
lighting. It may be necessary to vary the lower or top lighting to produce 
a balanced negative. 

References 

1 J. Hunt, An Introduction to Medical Photography, Staples Press, 1950. 

2 W. L. Brosius and C. C. Birkelo, Visual Correlation of the Clinical, 
Radiologic, and Pathologic Services (Gross- Specimen Photographs), 
Med. radiogr. Photogr., 25, No. 1, 1949, pp. 9-17. 

3 W. L. M. Martinsen, Gross Specimen Photography, Med. biol. Illust- 
ration, II, No. 3, July 1952, pp. 179-190. 

4 G. Mills, Infra-Red Photography of Gross Specimens, Radiogr. clin. 
Photogr. (Rochester, N.Y., U.S.A.), 13, No. 1, April 1937, pp. 12-13. 

5 W. Clark, Photography by Infrared, Chapman & Hall, 2nd edition, 
1946. 

Bibliography 

Photography of Gross Specimens Based on the Use of the Kodak Precision 
Enlarger, Radiogr. clin. Photogr. (Rochester, N.Y., U.S.A.), 18, 
No. 2, 1942, pp. 36-43. 

J. J. Beiter and M. G. Bohrod, Kodachrome Medical Photography Using 
Transilluminated Colored Backgrounds, Radiogr. clin. Photogr. 
(Rochester, N.Y., U.S.A.), 20, No. 2, 1944, pp. 34-39. 

Special Problems in Scientific Photography {Gross- Specimen Photography), 
Med. radiogr. Photogr., 25, No. 2, 1949, pp. 44-47. 

H. L. Gibson, Catch Lights on Gross Specimens, Med. radiogr. Photogr., 
25, No. 4, 1949, pp. 100-101. 

S MD-3 



H. L. Gibson, A Good Kodachrome Transparency for Teaching, Med. 
radiogr. Photogr., 26, No. 2, 1950, p. 85. 

N. K. Harrison, Photographing Pathological Specimens, Funct. Photogr., I, 
No. 10, July 1950, pp. 22-23. 

C. E. Peterson and H. L. Gibson, Photographing Fluorescent Objects in 
Color, Med. radiogr. Photogr., 27, No. 1, 1951, pp. 14-17. 

E. M. S. Breckenbridge and B. Halpert, The Photography of Gross 
Specimens, J. biol. photogr. Ass., 21, No. 1, Feb. 1953, pp. 1-4. 

A Technique for Presenting Small Specimens, Med. biol. Illustration, III, 
No. 3, July 1953, p. 158. 

J. Halsman, Standards in Gross Photography, J. biol. photogr. Ass., 23, 
Nos. 2 & 3, May- Aug. 1955, pp. 119-125. 

T. N. Salthouse, The Photography of Gross Specimens with Fluorescent 
Lighting, Med. biol. Illustration, V, No. 2, April 1955, pp. 75-84. 

E. Schalow, Transillumination in Biological Photography, Med. biol. 
Illustration, V, No. 3, July 1955, pp. 143-147. 

R. Marshall, Photographic Background Control, Med. biol. Illustration, VII, 
No. 1, Jan. 1957, pp. 13-21. 

P. Hansell and R. Ollerenshaw (editors), Longmore's Medical Photography, 
Focal Press, 7th edition, 1962, pp. 329-333. 



MD-3 



APPENDIX 

Suitable films for specimen photography 

Further details of the films listed below may be found on reference 
to the appropriate Data Sheets, the numbers of which are given after the 
title of each material. 



FILMS 


FORMS 


REMARKS 


Panchromatic 
'Panatomic-X' (FM-47 and FM-51) 

'Plus-X Pan (FM-52) 

'Plus-X' Pan Professional (FM-36 
and FM-48) 


Roll or 
miniature 

Miniature 
Sheet or roll 


\ Fine-grain, general- 
f purpose 

1 Fine-grain. Higher 
)-speed than 
J 'Panatomic-X' 


Tri-X' Pan (FM-53) 

Tri-X' Pan Professional (FM-37 
and FM-46) 


Miniature 
Sheet or roll 


1 When high speed 
Ms required 


Orthochromatic 

Commercial Ortho (FM-34) . . 
Tri-X' Ortho (FM-35) .... 


Sheet 
Sheet 


"| When it is 
[necessary to 
[stress the blood 

J and render it as black 


Colour-reversal 
'Kodachrome' II (FM-2A) . . . 


Miniature 




'Ektachrome-X' (FM-IE) .... 
'Ektachrome' — Process E-3 

(FM-ID) 

High-Speed 'Ektachrome' (FM-IB) 


Miniature 

Sheet or roll 
Roll or miniature 


~| Higher speed than 
('Kodachrome' II. 
TFor processing by 

J the user 


Colour-negative 

'Kodacolor-X' (FM-4A) .... 

'Ektacolor' Professional (FM-3) . . 


Miniature 
Sheet or roll 


\ When colour prints 
J are required 



The slower films are normally to be preferred because of the need 
for high resolution and the necessity to record fine detail. 

With monochrome films, various filters may be required to produce 
differentiation of colours; details of these may be found in Data Sheet 
FT-1, or, in more detail, in the book "Kodak Wratten Filters". When 
using tungsten lighting with panchromatic films, the Kodak 'Wratten' 
Filter No. 11 (XI) gives correct rendering of colours (Data Sheet FT-8). 



MD-3 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

KODACHROME 

KODACOLOR-X 

EKTACHROME 

EKTACHROME-X 

EKTACOLOR 

WRATTEN 

PANATOMIC-X 

PLUS-X 

TRI-X 

POLA 



Kodak Data Sheet KODAK LIMITED LONDON 

MD-3 

PDMD-3/xWPI 1/2-70 



CINE-FLUOROGRAPHY, SPOT FILMING 
and KINESCOPY 



The image intensifier 

The image intensifier was first introduced to medical radiology during 
the 1950s. It was realized that the image intensifier enabled not only 
conventional fluoroscopic examinations to be undertaken at brightness 
levels that did not require a dark adaptation, and with a reduction of 
the radiation dose rate to patients, but also extended the range of examina- 
tions and control procedures that could be undertaken. 

The equipment consists of an evacuated glass tube with a fluorescent 
screen at one end, normally 230 or 152 mm (9 or 6 inches) in diameter, 
often known as the "input phosphor", and bonded to this is a photo- 
cathode. Some types of tube have the input phosphor and the photo- 
cathode separated by a glass membrane. 

When an incident X-ray beam strikes the input phosphor, a conven- 
tional fluoroscopic image is formed. The emitted light, which is in 
proportion to the X-ray quanta absorbed, activates the photo-cathode 
and electrons are emitted. These electrons are accelerated by the 
application of a high voltage potential, normally 25 kV, across the tube 
and also electrostatically focused on to the output phosphor. This 
is a second fluorescent screen, usually 25 mm (1 inch) in diameter, which 
emits light proportional to the flux of electrons striking it. The combina- 
tion of these two factors — acceleration and reduction — results in increased 
brightness of the image by a factor of approximately 5000 times. 

Another type of intensifier employs an Orthicon or Isocon tube in 
place of the conventional image-intensifier tube. The light from the 
fluorescent screen is directed by an optical system on to the face of the 
tube, which incorporates a photo-cathode. This type of tube does not 
have an output phosphor so the image must be viewed on a TV monitor 
and recorded by kinescopy or a video tape system. 

Viewing systems 

The original image intensifiers were fitted with monocular or binocular 
devices which viewed the output phosphor. This meant that only one 
person at a time could view the intensified image; this situation was 
unsatisfactory and mirror viewing systems were soon introduced. It is 
now normal for a TV camera to be attached to the output phosphor 
and for the image to be viewed on TV monitors, which can be viewed 
under normal room-lighting conditions. Monitors can also be located 
remote from the X-ray room. 

In order to use recording as well as viewing devices, an image dis- 
tributor is normally fitted to the output phosphor. This consists of a 
lens, to convert the diverging light rays from the output phosphor into 
a parallel beam, and a number of semi-silvered mirrors, depending on 
the light outputs required. The semi-silvered mirror allows a percentage 

Issue D Kodak Data Sheet 

MD-4 



of the light to pass through the mirror for viewing, and the remainder 
is reflected for recording. 

Photo-recording methods employed in conjunction with image 
intensifiers are given in the following paragraphs. 




i 

UJ 
CD 



MD-4 




MD-4 



CINE-FLUOROGRAPHY 

This is the ideal recording medium for dynamic studies and for teaching 
purposes. Most cine cameras used are professional models adapted 
for use with the image intensifier. Either a 16 mm or 35 mm cine camera 
can be used; the choice of film size is often influenced by facilities 
available for film processing and projection. Although many factors 
influence the quality of the final image in cine-fluorography, it is generally 
true that a higher quality result can be obtained with 35 mm systems 
than with 16 mm. 

Camera speeds of up to 50 frames per second are suitable for most 
examinations, but for certain specialized investigations such as angio- 
cardiography, a camera capable of frame speeds in excess of 100 frames 
per second is usually demanded. 

The choice of the focal length of the camera lens should be considered 
in conjunction with the lens in front of the output phosphor. Variation 
of focal length of one or both lenses will produce reduction or enlarge- 
ment of the image size on the film. Each lens is located at a distance 
equal to its focal length from the output phosphor and the film frame, 
respectively, and the two lenses should be as close to each other as the 
mounts will permit. 

The high gain-factor of modern image intensifiers means that optimum 
density of the film can be obtained with low X-ray exposure values. 
Although this results in low patient dosage, a point is reached where 
quantum mottle, which simulates granularity, degrades the information 
content of the recorded image. 

Films 

A full range of Kodak films suitable for all types of cine-fluorographic 
examination is available. 

35 mm Films: 

Kodak 'Double-X' Negative Film S222, 200 feet on U Type core 
„ „ „ „ „ 400 feet on U Type core 

Kodak 'Plus-X' Negative Film 4231, 200 feet on U Type core 
,, „ „ „ „ 400 feet on U Type core 

Eastman '4-X' Negative Film 5224, 200 feet on U Type core 

'Kodak' 5498 RAR Film, 200 feet on U Type core 

'Double-X' Negative Film 5222 is generally the preferred f ' *i for 35 mm 
cine-fluorography in view of its high speed and relative. ^ fine grain. 
'4-X' Negative Film 5224 is suitable where the highest possible speed is 
required, and 'Plus-X' Negative Film 4231 is recommended for tech- 
niques requiring the finest possible grain. 

16 mm Films: 

Kodak 'Plus-X' Negative Film 7231, 100 feet on Daylight loading spool. 
Kodak 'Double-X' Negative Film 7222, 100 feet on Daylight loading 

spool. 
Kodak '4-X' Negative Film 7224, 100 feet on Daylight loading spool. 
Kodak 'Tri-X' Reversal Film 7278, 100 feet on Daylight loading spool. 
Kodak 'Plus-X' Reversal Film 7276, 100 feet on Daylight loading spool. 

MD-4 



The fine-grain properties of 'Plus-X* Negative Film 7231, make it very 
suitable for 16 mm cine-fluorography. '4-X' and 'Double-X' Negative 
Films 7224 and 7222 are suitable when higher film speeds are required. 
All the above films are supplied with perforations on both edges and 
wound emulsion side in. Other windings and perforations are available, 
although some specifications can only be supplied against a special order 
which may be subject to a minimum-order quantity. 

Processing 

Various methods can be used for processing 16 mm and 35 mm cine 
film; the selection of the method will depend on image quality required, 
convenience of operation, cost, and, not least, on the speed with which 
the film must be available for viewing after exposure. 

If only short lengths of film are involved, they may be processed 
conveniently by winding the film, emulsion side out, in vertical loops 
round an X-ray film hanger and using conventional X-ray processing 
tanks. Spiral processing units capable of processing up to 100 feet of film, 
some incorporating take-up and drying devices, are also available. 

If the film record is intended primarily for immediate diagnostic 
purposes, it is generally desirable to process the film to a high contrast 
using a fresh solution of 'Kodak' DX-80 Developer (diluted 1 + 4) for 
4-6 minutes at 20°C (68°F). If the film is required for projection to 
large audiences, then a finer grain and somewhat lower contrast is prefer- 
able. In these circumstances, 'Kodak' D-76 Developer is recommended 
with a processing time of 12-16 minutes at 20° C (68°F). The times 
given assume thorough agitation for 5 seconds every minute. 

Certain films can be processed through the Kodak RP 'X-Omat' 
90 second processor. Full information on the films considered suitable 
for automatic processing can be obtained from the Medical Markets 
Division of Kodak Limited. 

All ICodak films suitable for cine-fluorography should be handled and 
processed in total darkness owing to their speed and panchromatic 
sensitivity. 

If the film record is not required soon after exposure, or if it is not 
practical for the film to be processed in the hospital, it can be sent for 
processing to one of the many commercial cine processing laboratories. 

Projection 

The projector used for viewing cine-fluorographic film should have 
facilities for forward and reverse running over a range of frame speeds, 
usually 1 to 24 frames per second. The projected image should be free 
from flicker and the film gate should be efficiently cooled so that a single 
frame can be viewed for some time without damage to the film. There 
are only a few 35 mm projectors available with these facilities and for 
this reason 35 mm films are usually printed down on to 16 mm stock for 
projection purposes. If only a few people intend to view the film at a 
given time, a projector /viewer, such as the Acmade "High Definition 
Analysing Projector", or the Tagarno 35 Projector, may be employed. 

5 MD-4 



SPOT FILMING 

This technique is the single-exposure recording of the output phosphor 
producing individual fluorographic records. These records can be 
produced in rapid succession, up to 6 frames per second. A number 
of film widths and formats are employed, including sheet films, but in 
the UK 70 mm roll film seems to be the most popular size. 

Film 

70 mm Kodak RP 'X-Omat' Flurospot film is specifically intended for 
all spot filming techniques. 

Processing 

Kodak 'Flurospot' Film is designed for processing in a 90 second 
processor. The film should be taped to an X-ray film which acts 
as a leader. A suitable tape to use is Scotch Brand Silver Tape Type 850. 
The film should be fed into the processor emulsion side down. 

Safelighting 

Kodak 'Flurospot' Film has orthochromatic sensitivity and should 
not be handled under normal X-ray safelighting. It can be handled 
under a safelamp fitted with a 'Kodak' Safelight Filter No. 2 (dark red) 
and a 25 watt pearl lamp at not less than 1.2 metres (4 feet) from the 
film, or in total darkness. 

Storage 

Card envelopes, with cut-out centres for viewing, are available for 
storage of the processed 70 mm spot film. These are available from 
suppliers of X-ray sundries. 

Viewing 

Spot films may be inspected by the light of an X-ray illuminator or 
using an overhead projector, projected on to a screen for viewing by a 
larger audience. 

KINESCOPY 

Kinescopy is the cine-recording of an image shown on a TV monitor 
during TV fluoroscopy. It may also be used to film the diagnostically 
significant parts recorded on a video tape of a fluoroscopic examination 
made at an earlier date. 

A 16 mm camera is usually employed and this should be synchronized 
to the TV scan time-base or incorporate a special shutter in order to 
overcome the problem of "black bars" moving down the picture area. 

Films 

'Plus-X' Negative Film 7231 is recommended for kinescopy because of 
its fine grain and high-definition characteristics. 

Kodak, Double-X, 4-X, Tri-X, Plus-X and Eastman are trade marks 

Kodak Data Sheet KODAK LIMITED LONDON 

MD-4 

PDMD-4/xWPI0/3-7l 



TOMOGRAPHY 



PRINCIPLES 

In a radiograph, the images of other structures obscure and complicate 
the images of the region of interest. Tomography simplifies radiographic 
appearances by giving a sharp image of any selected plane within the 
patient; the images of planes above and below that selected are blurred. 
This is achieved by causing the images of unwanted planes to move across 
the film during exposure, whereas the image of the selected plane remains 
stationary on the film. The degree of unsharpness in the images of planes 
immediately above and below that selected is small and these planes also 
appear sharp in the tomogram, so that, in practice, the tomogram records 
a layer of the patient rather than a plane. The thickness of the layer or 
"cut" can be controlled within limits. Essentially, the tomogram is a 
sharp image of the chosen layer superimposed on a diffuse background 
made up of the blurred images of all other layers of the body part. 

Various techniques have been devised and various names used, such as 
tomography, stratigraphy, planigraphy, laminagraphy, layer radiography, 
planar radiography, and body-section radiography. In all these tech- 
niques, the basic principle is the same. 

The equipment (Figure 1) consists of a moveable X-ray tube R con- 
nected by a rod C to a film carriage F (usually the cassette tray of the 
Potter-Bucky diaphragm). The rod C is telescopic so that the vertical 
distance of the tube focal spot from the film plane remains the same at all 
tube positions. 

A pivot H is provided about which rod C turns, so that when the tube 
moves in one direction the film is moved synchronously, but in the 
opposite direction. The position of the pivot H is adjustable. 




Issue B 



Kodak Data Sheet 
MD-5 



Figure 2 illustrates the principle of tomography and shows the X-ray 
tube R in three positions. The broken line indicates the path along which 
the tube focal spot moves during exposure. The film plane is shown at F, 
and P is a point in the body on the plane to be recorded. The pivot is 
adjusted to occupy the same plane as the point P. A is a point in the body 
lying in the plane remote from P. 

The images of points P and A formed in the three tube positions are 
shown at P 1} P 2 , and P 3 , and A v A%, and A s in the lower part of the figure. 
Point P appears at the same position on the film for all tube positions : the 
image of point P will therefore be sharp. Similarly, the images of all other 
points on the same plane as P will also be sharp. The images of point A 
appear at different positions on the film for each tube position and, since in 
practice the movement of the tube and film is continuous during exposure, 
the image of point A will be a continuous blur extending between A x and 
A 3 in the diagram. This applies to the images of all points lying outside 
the selected plane, and the further the points are from the selected plane 
the greater will be the blurring of their images in the tomogram. As 
already stated, the position of the pivot can be adjusted so that any plane 
in the body can be selected for recording. 



in TUBE POSITION 
START OF EXPOSURE 




2»» TUBE POSITION 
R 



3«» TUBE POSITION 
END OF EXPOSURE 




P,4P 2 »i *2 






Figure 2 



EQUIPMENT 

The various types of tomographic equipment differ mainly in the 
mechanics of tube and film movement. Equipment has been designed to 
give spiral or sinusoidal movements instead of the more common recti- 



MD-S 



linear movement. The advantages of such complex motions are not usually 
considered sufficient to justify the mechanical complications involved. 

The X-ray tube, connecting rod, and film are usually moved during 
exposure by an electric motor, or by a powerful spring. Switches are 
usually provided to ensure that the X-ray exposure starts after the tube 
has commenced to move, and terminates before movement stops. In 
some equipment, the switches are arranged so that the angle through which 
the tube moves can be varied at will from about 30 to 60 degrees. This 
gives control over the thickness of the sharply recorded layer since the 
greater the angular movement the thinner will be the sharply recorded 
layer. It is usually possible to control the speed of tube movement to 
suit the exposure time used. 

Some equipment is designed solely or principally for tomography, but 
tomographic attachments which can be fitted to a normal X-ray couch 
are in general use. The attachments are usually designed to operate with 
the patient in the horizontal position, but equipment is available for use 
with the patient upright. 

The focus-film distance can usually be varied from about 30 to 40 inches ; 
less commonly, distances of up to 72 inches are possible. 



TRANSVERSE BODY-LAYER TOMOGRAPHY 

The conventional tomographic equipment records a layer in the 
longitudinal plane of the patient. However, equipment is also available for 
horizontal (transverse) layer radiography; in this, the position of the tube 
is fixed, and patient and film rotate synchronously about vertical axes. 
The X-ray beam is limited by a slit diaphragm. 

SIMULTANEOUS MULTI-LAYER TOMOGRAPHY 

In 1947, D'Abreu introduced an important advance in tomography. 
This method is now generally known as Simultaneous Multi-section or 
Multi-layer Tomography. The object of the technique is to produce, 
by one exposure only, a series of tomograms each recording a separate 
body layer. This is done by substituting for the cassette used in normal 
tomography, a special magazine containing several films. 

Advantages 

The principal advantage claimed for simultaneous multi-layer tomo- 
graphy is that with suitable intensifying screens the radiation dose to 
the patient is less than that required to produce the same number of 
tomograms by conventional methods. Furthermore, all layers are 
recorded with the same degree of enlargement and in precisely the same 
physiological phase, a point of considerable importance in tomography of 
mobile organs such as the lungs. The simultaneous method saves time 
and labour in the X-ray room. 

Most normal tomographic equipment can be adapted for the simul- 
taneous multi-layer technique by removing the tray of the Potter-Bucky 
diaphragm and substituting a suitable support for the magazine. 

3 MD-5 



Principles 

In normal tomography, the body layer in the same plane as the pivot is 
sharply recorded on a film placed in the plane of the pin joining the connect- 
ing rod to the film carriage (Bucky tray). In multi-layer tomography, the 
first film in the magazine is situated at the level of this pin and records 
the body layer at pivot level. The other films in the magazine are placed 
at successively lower levels and record layers of the body below that at 
pivot level. 

Figure 3 is similar to the diagram used to explain conventional tomo- 
graphy (Figure 2). But in Figure 3 an additional film is shown at a lower 
level than that in Figure 2. During exposure this lower film moves 
simultaneously with the upper film. In Figure 3 (as in Figure 2) the 
images of point P fall on the same place on Film 1 for all three tube 
positions, and each tube position gives a separate image of point A on 
Film 1. Point P will be sharp on Film 1 but point A will be unsharp. 
On Film 2, each tube position gives a separate image of point P, but the 
image of point A falls on the same place for all tube positions. Thus, on 
Film 1, all detail lying in the same plane as P will be sharply recorded; 
detail in other planes will be blurred. On Film 2, only detail in the same 
plane as A will be sharply recorded. 

In practice, more than two films are exposed simultaneously and the 
films are separated in the magazine by spacers of some material having a 
very low absorption of X-rays. Since intensifying screens are generally 



1ST TU BE POSITION 
START OF EXPOSURE 



2»" TUBE POSITION 



3«° TUBE POSITION 
END OF EXPOSURE 







P, 


Ai 




P, 






• 




FILM 1 




• 
Hi 





i <^ "f' FILM I 

P,P;P, A, A2/Aj 
!■■■ *-l FILM 1 



p, p, p. 


A|A 2 A, 


P.PIPJ 

• 






• • • 
A, A, A, 




Figure 3 



MD-S 



used, the spacers must also give uniform screen-film contact. Sheets of 
balsa wood or polyester foam of suitable thickness can be used as spacers. 

Choice of intensifying screens 

Since intensifying screens absorb some X-radiation, the second and 
subsequent films receive less radiation than the first; additionally, the 
second and subsequent films are further from the tube than the first, and 
will receive progressively less radiation for this reason. It is possible to 
compensate for the effects of absorption and distance by using intensifying 
screens of successively higher speed from top (nearest tube) to bottom of 
the magazine. The best combination of screens will depend on the 
kilovoltage used and on the film separation, but suggested combinations 
are given in the tables below : 



SIMULTANEOUS EXPOSURE OF 3 LAYERS 


Film Position 


Type and Number of 'Kodak' Intensifying Screens 


1st Film (nearest tube) .... 


High-Speed "Front" Screen only 


2nd Film 


Pair of Fine-Grain Screens 




Pair of Regular Screens 






SIMULTANEOUS EXPOSURE OF 5 LAYERS 


Film Position 


Type and Number of 'Kodak' Intensifying Screens 


1st Film (nearest tube) .... 


Fine-Grain "Front" Screen only 




Regular "Back" Screen only 




3rd Film 


Pair of Fine-Grain Screens 








Regular "Front" Screen as Front 

Screen, and Regular "Front" Screen 

as Back Screen 




5th Film 


Pair of High-Speed Screens 



MD-S 



The screen combinations given in these tables have been found satis- 
factory at kilovoltages between about 70 and 90, and with film separations 
of up to 2 cm. The same type of film should be used for all layers, and the 
variation in density from film to film is within acceptable limits. By 
taking advantage of the development latitude of 'Kodak' X-ray film, it is 
possible to produce closely matched tomograms by appropriate adjustment 
of the development time for each film. 

The exposure required for the 3-layer method is approximately twice 
that normally given for the part in question when using a pair of 'Kodak' 
Regular Intensifying Screens; in the 5-layer technique, the exposure is 
about 3 times the normal. 



Spacing of the body layers 

The spacing between the layers of the body which are sharply recorded 
is less than the distance between the films in the magazine. When the 
film separation is known, the separation of the body layers can be cal- 
culated from the following expression: — 

Alternatively, the film separation needed to give the desired amount of 
body-layer separation can be found from the equation : — 



*-<>+b) 



In both expressions : — 

Sl = separation of body layers 

Sf = separation of films 

D = Focus to pivot distance 

d = Distance of pivot to 1st film 



CONVENTIONAL AND SIMULTANEOUS MULTI-LAYER TOMOGRAPHY 
IN PRACTICE 

Tomography is used to locate structures and lesions and to determine 
their extent. In addition, lesions which are invisible or difficult to discern 
in the normal radiograph may be revealed by tomography. Tomography 
finds its greatest application in radiography of" the lungs but is by no means 
confined to this region of the body. 

Positioning in tomography 

It is convenient when positioning the patient for tomography to place 
the X-ray tube and film carriage in the mid-point position; that is, with 
the connecting rod vertical or horizontal. The body part can then be 
centered in the normal way. The position of the patient in relation to the 

MD-5 6 



direction of tube movement is important since the maximum blurring 
occurs in structures lying at right angles to the direction of movement. 
For instance, the outline of a long bone will be sharp if its length is 
parallel to the direction of movement, and structures above or below the 
bone will not be well demonstrated in the tomogram. If the long bone 
is at right angles to the direction of travel, then its outline will be blurred, 
and underlying or overlying structures will be shown in the tomogram. 
Thus, in tomography of the lungs, movement of the tube in a direction 
parallel to the spine, and at right angles to the ribs, successfully blurs the 
latter structures. 

Tomography is a useful method of demonstrating the sternum and 
sterno-clavicular joints. This, however, involves a difficulty in that if the 
direction of tube travel is parallel to the spine, that structure is not 
adequately blurred, and if movement is at right angles to the spine then the 
ribs will interfere with the tomographic image. This difficulty is over- 
come by placing the patient in an oblique position so that the spine is 
projected clear of the sternum, the tube movement being in a direction 
parallel to the spine. Alternatively an anterior -posterior projection can 
be made with the patient placed so that the sternum is at an angle of 
about 70° to the direction of tube travel. In this way, both ribs and 
spine are adequately blurred. 

The above examples should illustrate the principle to be applied when 
examining other parts of the body where a similar problem arises. 



Use of Potter-Bucky diaphragm and cones 

A Potter-Bucky diaphragm is nearly always used for tomography not 
only because the Bucky tray forms a convenient film carriage, but because 
in tomography the mass of tissue exposed to radiation is greater than that 
in normal radiography. This results in the production of a correspond- 
ingly greater amount of scattered radiation which must be eliminated to 
obtain adequate contrast. 

In tomography, it is essential to use a cone or preferably a multi-leaf 
diaphragm which strictly limits the X-ray beam to the required region. 
This ensures that the minimum amount of radiation is applied to the 
patient, and helps to reduce the amount of scattered radiation produced. 



Pivot setting 

After the patient has been placed on the couch, the pivot can be set at 
the required height. The pivot setting depends on the distance from the 
couch top of the region to be demonstrated. This distance may be 
measurable on the patient or may be known from conventional radio- 
graphs. Frequently, however, tomography is used to investigate a lesion 
giving an indefinite shadow of low contrast in a conventional radiograph. 
In such a case, the pivot must be fixed at a height above that of the sus- 
pected lesion for the first tomogram. A series of tomograms must then 
be taken, the pivot height being decreased progressively for each exposure. 
Sufficient tomograms must be taken to include the whole of the lesion and 
related anatomical features. 

7 MD-5 



KODAK 

is a trade mark 



Kodak Data Sheet KODAK LIMITED LONDON 

MD-5 

PDMD-5/r3WPIi/5-70 



direction of tube movement is important since the maximum blurring 
occurs in structures lying at right angles to the direction of movement. 
For instance, the outline of a long bone will be sharp if its length is 
parallel to the direction of movement, and structures above or below the 
bone will not be well demonstrated in the tomogram. If the long bone 
is at right angles to the direction of travel, then its outline will be blurred, 
and underlying or overlying structures will be shown in the tomogram. 
Thus, in tomography of the lungs, movement of the tube in a direction 
parallel to the spine, and at right angles to the ribs, successfully blurs the 
latter structures. 

Tomography is a useful method of demonstrating the sternum and 
sterno-clavicular joints. This, however, involves a difficulty in that if the 
direction of tube travel is parallel to the spine, that structure is not 
adequately blurred, and if movement is at right angles to the spine then the 
ribs will interfere with the tomographic image. This difficulty is over- 
come by placing the patient in an oblique position so that the spine is 
projected clear of the sternum, the tube movement being in a direction 
parallel to the spine. Alternatively an anterior -posterior projection can 
be made with the patient placed so that the sternum is at an angle of 
about 70° to the direction of tube travel. In this way, both ribs and 
spine are adequately blurred. 

The above examples should illustrate the principle to be applied when 
examining other parts of the body where a similar problem arises. 

Use of Potter-Bucky diaphragm and cones 

A Potter-Bucky diaphragm is nearly always used for tomography not 
only because the Bucky tray forms a convenient film carriage, but because 
in tomography the mass of tissue exposed to radiation is greater than that 
in normal radiography. This results in the production of a correspond- 
ingly greater amount of scattered radiation which must be eliminated to 
obtain adequate contrast. 

In tomography, it is essential to use a cone or preferably a multi-leaf 
diaphragm which strictly limits the X-ray beam to the required region. 
This ensures that the minimum amount of radiation is applied to the 
patient, and helps to reduce the amount of scattered radiation produced. 

Pivot setting 

After the patient has been placed on the couch, the pivot can be set at 
the required height. The pivot setting depends on the distance from the 
couch top of the region to be demonstrated. This distance may be 
measurable on the patient or may be known from conventional radio- 
graphs. Frequently, however, tomography is used to investigate a lesion 
giving an indefinite shadow of low contrast in a conventional radiograph. 
In such a case, the pivot must be fixed at a height above that of the sus- 
pected lesion for the first tomogram. A series of tomograms must then 
be taken, the pivot height being decreased progressively for each exposure. 
Sufficient tomograms must be taken to include the whole of the lesion and 
related anatomical features. 

7 MD-5 



In simultaneous multi-layer tomography, the pivot height must be set 
so that the top film records a body layer above the lesion or structure of 
interest; the lower films will then record body layers successively below 
the first. Sufficient films must be taken to include the relevant structures. 

Separation of body layers 

In conventional tomography, the pivot height is usually adjusted for 
each exposure so that the recorded body layers are separated by a distance 
of about 1 cm. In multi-layer tomography, the film separation is usually 
selected to record body layers about 1 cm apart. 

Ideally, the greatest amount of information would be obtained by 
making the tube and film move through a very large angle during exposure, 
thus recording a very thin layer of the object. However, this would entail 
the use of a large number of films with a consequent heavy dosage to the 
patient, and the contrast obtained in the tomogram might be inadequate 
when the body layer is very thin. When large angles are used, the X-ray 
beam strikes the film very obliquely and this gives rise to complications. 
For these reasons, the maximum angle of movement is usually restricted 
to about 60°. 

Identification 

Each film must be marked so as to identify the body layer recorded. 
This is best done by placing a suitable scale on the couch adjacent to the 
patient so that it can be recorded on the tomogram. The scale should 
carry a series of radiopaque marks of identifiable height above the couch 
top. The location of the body layer is then found by examining the image 
of the scale on the tomogram. This method has the great advantage 
of being independent of errors in setting the pivot height, and of mechanical 
inaccuracies of the apparatus. The method applies to both conventional 
and simultaneous techniques. 

Where the above method is impracticable in conventional tomography, 
an appropriate lead marker should be placed on the front of each cassette 
to identify the body layer. In simultaneous multi-layer tomography, the 
layers are best identified by making suitable marks on each of the intensi- 
fying screens used. As an additional precaution, each film should be 
numbered before it is placed in the magazine. 

Exposure 

In conventional tomography, the exposure required is generally the 
same as that given for the particular body region in ordinary radiography. 
However, due account must be taken of possible changes in focus-film 
distance, and the use of a Potter-Bucky diaphragm. 

In simultaneous multi-layer tomography, the exposure depends on the 
number of layers recorded and on the screen combination used. The 
3-layer combination given in the table on page 5 requires about twice 
the normal exposure for the part in question when using a pair of 'Kodak' 
Regular Intensifying Screens; the 5-layer combination requires about 3 
times the normal exposure. 

md-S 8 



With some tomographic apparatus, the exposure time is fixed at about 
1 second and cannot be varied. In such cases, the milliamperage must be 
adjusted to give the required miUiampere-seconds in a 1 second exposure. 
This may not be possible because of the restricted choice of millia- 
amperage available; in such a case, the kilovoltage must be adjusted to give 
the required density. It is a common practice to over-expose tomograms 
and to correct for this by under-development. This may be permissible 
if the development latitude of the film is sufficient to give adequate radio- 
graphic quality. However, severe under-development results in a re- 
duction of contrast and this is particularly undesirable in tomography. 



Processing 

Where possible all tomograms of a particular patient should be pro- 
cessed at the same time to ensure an identical degree of development for 
all films and to avoid changes in contrast which might make interpretation 
of the results more difficult. Details are given in Data Sheet XR-6 and 
in the Data Sheets appropriate to the particular X-ray films in use. 



BIBLIOGRAPHY 

J. Grossman, Brit.J.Radiol., 8, 1935, p.733. 

J. B. McDougall, Tubercle(London), 17, 1935-36, p. 452. 

V. E. Pullin, Radiography — An Aspect of Non-Destructive Testing, J.Inst. 
Elect.Eng., 84, May 1939., 

J. B. McDougall, Tomography, Lewis, 1940. 

W. Watson, Differential Radiography, Radiography, V, 1939, pp. 81-88 
VI, 1940, pp. 161-172; and IX, 1943, pp. 33-38. 

M. d'Abreu, Theory & Technique of Simultaneous Tomography, Amer.J 
Roentgenol., 60, 1948, pp. 668-674. 

D. W. Crombie and P. M. Andrus, Vertical Tomography of the Thorax. 
Amer.Rev.Tuberculosis, 62, Aug. 1950. 

A. Vallebona, Axial Transverse Laminagraphy, Radiology, 55, Aug. 1950 
pp. 271-273. 

S. Baudry, Masks for Making Simultaneous Tomograms, Med. Radiogr. 
Photogr., 26, No. 2, 1950, pp. 54-56. 

E. B. Kennedy, Factors Determining the Thickness of Cut in Tomography. 
Radiography, XVII, No. 201, Sept. 1951, pp. 190-192. 

W. Watson, Simultaneous Midtisection Radiography, Radiography, XVII 
No. 203, Nov. 1951, pp. 221-228. 

J. W. McLaren (editor), Modern Trends in Diagnostic Radiology, (Second 
Series, Chapter 2) Butterworth, 1953. 

C. Esser, Body-Section Radiography of the Bronchial Tree, Med. 
Radiogr. Photogr., 36, No. 2, 1960, pp. 38-44. 

9 MD-5 



KODAK 

is a trade mark 



Kodak Data Sheet KODAK LIMITED LONDON 

MD-S 

PDMD-5/r3WPI±/5-70 



INDUSTRIAL APPLICATIONS 



CONTENTS EDITION 

IN-I Photography Applied to Flow Visualization Issue A 

IN-2 The Photography of High-Speed Events Issue E 

IN-5 Photography in the Drawing Office Issue G 

IN-7 Photographic Techniques in Work Study Issue D 

IN-8 Recording Temperature Distribution Issue 8 

IN- 1 Photography of the Macrostructure of Metals Issue C 

IN-I I Metallography Issue C 

IN- 1 2 Contact Microradiography Issue 8 

IN-14 The Radiography of Light Alloys Issue E 

IN- 1 5 Weld Radiography Issue F 

IN-16 Gamma-Radiography Issue £ 



Associated Data Sheets in this or other volumes or sections 

The Dimensional Stability of Photographic Films and Plates 

KODAK 'Wratten' Filters for Scientific and Industrial 

Purposes 

All Radiography Section 

Photo-Elastic Stress Analysis 

Ultra-Violet Photography in Science and Industry 

Ultra-Violet Photomicrography 

Infra-Red Photography 

16 mm Cine-Micrography 

Autoradiography 

Photomacrography 

Photomicrography: Centring and Adjustment of Apparatus 

Exposure in Photomicrography 

The Photographic Aspects of X-ray Crystallography 

Photographic Copying of Documents 

Stabilization Processing Techniques 

The Diffusion-Transfer Process using KODAK 'Instafax' CT 
Materials 

Continued overleaf 



1, 


RF-IO 


1, 


FT-3 


2, 


XR 


2, 


SC-I 


2, 


SC-3 


2, 


SC-4 


2, 


SC-7 


2, 


SC-8 


2, 


SC-IO 


2, 


SC-II 


2, 


SC-I 2 


2, 


SC-I 3 


2, 


SC-I 5 


2, 


DC-I 


2, 


DC-2 


2, 


DC-4 



3, CL-7 Problems in Colour Photography 

3, CL-8 Colour Photography by Artificial Light 

3, CL-9 Colour Photography and the Human Eye 

4, SE-3 'Kodak' Scientific Plates and Films 

4, SE-5 'Kodak' Photographic Materials for Electron Micrography 

4, SE-9 'Kodak' Photo-Sensitive Resists in Industry 



Kodak, Wrotten, ond Instafax ore trade marks KODAK LIMITED LONDON 

Y 1 275PDDB-30/xWP9i /4-72 



PHOTOGRAPHY APPLIED 
TO FLOW VISUALIZATION 



There are many processes in industry and science where the flow around 
bodies in gases and liquids, and also the flow of the liquids themselves, 
need to be studied. This Data Sheet gives a few of the ways in which 
photography can be used. 

The problems that arise for study are of two main types; those which are 
visible to the eye, and those which require special techniques to make them 
visible. Even where the subject is visible, photography may make the 
measurement or assessment of the subject very much easier. The most 
important attribute of photography is that, normally, it does not affect or 
distort the subject or experiment; mechanical flow-meters, for example, 
introduce eddies or flowchanges. 

It is important to remember in this field that the full information often 
may only be obtained by using more than one photographic technique; one 
aspect may best be measured by one technique, whilst another aspect may 
be shown best by a second technique. Photographic techniques, used in 
conjunction with physical, instrumentation or chemical techniques, can 
often contribute to the final answer more than can be achieved by any 
single discipline or technique. 

METHODS FOR THE STUDY OF SURFACE DISTORTIONS 

Where flow is occurring in a liquid, information may be required about 
either the surface or internal flow patterns. This section discusses those 
subjects where the flow or level changes at the surface are to be studied. 

The use of floats and floating material 

To study surface movement and flow patterns, small particles of material 
(for example, white expanded polystyrene, polystyrene beads or aluminium 
paint) can be made to float on the water. Photographs can then be taken 
at suitable intervals and measurements taken either straight from the 
negative or from a projected image or print. Dependent on the model or 
experiment size and on the flow rate expected, it may be possible to use 
larger floats which may even contain a small light. Analysis of flow pat- 
terns is aided if the photographs are taken at regular time intervals, as 
velocity can then be easily determined. To make the measurement of 
velocity even simpler, and to give a subjective overall picture more 
quickly, a variation of the memomotion techniques described in Data 
Sheet IN-7 can be utilized. 

When using beads or paint as a flow tracer, the result will be a series of 
dots or streaks if the ambient light is kept low and a strobe-flash lighting 
unit used, with the camera shutter kept open for a relatively long period. 
The length of the traces and their distance apart, together with the known 
flashing rate will give velocity. 

Using floats with a light built into them and maintaining a very low 
ambient light level enables the path of the float to be recorded as a long 

Issue A Kodak Data Sheet 

IN-I 



streak tracing the flow patterns and vortices. The velocity can be ana- 
lysed by placing a fan or rotating shutter in front of the lens and rotating this 
at a known speed. The direction of flow even where vortices give rapidly 
reversing flow can be shown by incorporating a small slot in the leading 
edge of one blade to give a dot-dash effect to the trace. The dot will be 
in the leading edge of the trace, thus indicating direction; the length of 
the trace or of each space gives the velocity. 



y g^ii—i | 





^ 



r ^y 



^\ i 



w 



Figure I (a) Diagram of rotor blade : R- 
K x — slot cut in leading edge of 1 blade ; L— 

(b) Diagram of arrangement : M — motor ; 

(c) Typical track produced. 



—rotor blade, usually 3 or 5 blades; 

-lens. 

G — reduction gearbox ; C — camera. 



"Starry Sky" technique 

If the problem is to see not horizontal movement, but vertical movement, 
such as swells or waves on the water surface, then a different approach 
should be used. If a regular grid or pattern of small lights is mounted 
above the surface to be studied, the reflection of these points of light can be 
photographed. With a perfectly still surface the regular grid pattern will 
be maintained in the reflected image. This technique is illustrated in 
Figure 2 on page 3. If the water surface is moving or is disturbed in 
a vertical direction then the reflected images will be moved relative to each 
other. In the disturbed areas, dependent on exposure time the record 
will show displaced points as streaks and circles. This system gives areas 
and amount of disturbance at the surface. Measurement is by conven- 
tional optical geometry. 

Point-source technique 

If the experiment can be carried out in complete darkness, the following 
technique may be useful in assessing surface deformation. This technique 
requires the liquid to be clear, and either the liquid must be photographi- 
cally virtually inert or contained in a clear glass cell. If the film or plate is 



IN-I 




Figure 2 "Starry Sky" Technique. This photograph is Crown copyright. 

put below the surface and a point-source of light is flashed, switched or 
shuttered for a short time, and if no surface deformation is present, even 
fogging will result. If a low wave is present at the surface, the light from 
this point-source will then be refracted at a different angle to that from a 
flat surface. The result, a pattern of density differences can be difficult to 
analyse, but with suitable calibration and comparison the simplicity of the 
equipment required may make the method useful. 



IN-I 



FLOW WITHIN THE BODY OF THE LIQUID 
The use of floats and dye streamers 

The use of floats and floating material is again one possible method 
although here the particles must be chosen with particular regard to their 
buoyancy. To give acceptable results, many materials including poly- 
styrene beads or even fish scales can be used providing they have a neutral 
buoyancy. Size of particle should be kept to a minimum capable of being 
resolved by the particular optical or photographic system used, if the 
particle is to follow the flow exactly; smaller particles will introduce less 
error due to their inertia than will larger particles. Dye streamers may 
also be used, or even particles of materials such as Acid Fuchsin, which as 
they move are also dissolving, leaving a fine trace behind them. Potassium 
permanganate particles can also be used; they give a broader more diffuse 
line. 

Most dye streamer techniques use a solution released through a fine 
needle, at a slow enough rate not to introduce its own flow patterns and so 
distort the experiment. Release of dye should take place far enough up- 
stream of the area being studied to ensure minimal effect on the flow from 
turbulence introduced by the presence of the needle. 

Basically the same techniques are applicable in gas as in liquids, although 
the material used as a tracer will be different. Various chemical or oil 
smokes have been used; water vapour can also be used under suitable 
circumstances. 

Multiple streamer techniques are useful. A needle or tube is used, at 
right-angles to the flow, having a series of regularly spaced holes to give 
parallel streams of dye or smoke to show flow over objects in the fluid. A 
record from this technique will also show areas of turbulence. 

By selecting materials that have a slightly positive or slightly negative 
buoyancy in a particular liquid, they can be made to settle on and show 
interfaces between two liquids or gases, for example, the use of dyes or 
smoke to show temperature inversions. Alternatively, an interface can be 
shown by introducing a chemical, into one phase, that will change colour 
on contact with another having a different chemical constituent. One 
example of this technique is the addition of Bromothymol Blue, giving a 
yellow colour, to water and a liquid or gas interface which contains, for 
example, ammonia; this will cause a change in coloration to blue at the 
point of contact where mixing or mass transfer occurs. 

Photo-optical techniques 

Often, direct photographic techniques, as described in the earlier 
sections, are not suitable, for example, where density differences exist but 
are not visible to the eye. The difficulty most often encountered is that of 
sensitivity; the photographic system on its own being unable to adequately 
record the very small differences (e.g., in density) required. However, 
when photographic techniques are allied to optical techniques, a powerful 
and unique tool is available. 

Shadowgraph : Most of the optical techniques suitable for this type of 
work require a system based on parallel light. If one observes the patch 

IN-I a 



of sunlight on the floor, it is often possible to see shadowgraphs of the hot 
air rising from a cooker or radiator; this is because the light-source, in this 
case the sun, can be considered as being at infinity, thus giving rays 
which are virtually parallel. It follows therefore that if a light-source 
is placed behind a lens, at a distance equal to the focal length of the 
lens, the same effect can be observed in the resultant parallel beam, 
as again a parallel beam can be considered as being from infinity. The 
shadowgraph produced can be viewed directly on a screen or, if a piece 
of sensitized material is placed in the beam, a permanent record can be 
made. 

Whilst a simple shadowgraph can show and record some information not 
easily seen by eye, a few simple refinements of the system can make it much 
more sensitive. As with all optical systems detecting density changes by 
refraction of light rays, the light-source should preferably be monochro- 
matic and as near a point-source as possible. Greater definition is achieved 
with monochromatic lighting, as the diffusion of the image, from the e.g., 
red and blue components of the light being affected to different degrees, is 
no longer present. In practice, a truly monochromatic light-source is an 




f <SU> s 



(b) 



Figure 3 (a) Shadowgraph schematic diagram: S — light-source; — object; 
L x — lens ; Fm — film or viewing screen; Dj — distance, equal to focal length of L x ; 
D 2 and D 3 — distances, not critical. 

(b) One method of achieving a suitable light-source; F — filament; L 3 — lenses to 
focus F on to S to form SI; SI — slit. 




Figure 4 Focused shadow : S — light-source ; — object ; L x and L 2 — lenses ; Fm — film 
or viewing screen ; x — focal point of rays from L x ; D x — distance arranged so that x is 
coincident with principal nodal point of L 2 ; D 2 — distance as short as possible to give 
largest useful working area within cone of light ; D 2 + D 3 — the greater this distance, the 
better the sensitivity ; D 3 + D 4 — this distance will depend on focal length of L 2 , but O 
should be positioned to give at Fm a focused image of O which is giving rise to the effect 
to be studied. The image should be within the cone of light from L x . 



IN-I 



improbability; even a laser beam has a finite band width. For most 
practical applications, a green filter, isolating a single emission line from a 
mercury light source, will be adequate. 

The sensitivity of a shadow system can also be increased by focusing the 
system and by increasing the distance D 3 in Figure 3. 

Focused Shadow : Use a monochromatic point-source of light and a lens, 
but instead of producing parallel light produce a convergent cone of light. 
If, in addition to this, the point at which the converging rays meet is 
arranged to coincide with the principal nodal point of a second lens, a 
condition known as focused shadow is produced (Figure 4). If its subject 
is placed close to the lens, as illustrated, any rays which are refracted, by 
higher or lower densities in the subject, will be further refracted by the 
second lens, resulting in greater sensitivity. 

Schlieren: A more precise, more flexible and much more sensitive system 
than those previously described in this Data Sheet is that system known as 
schlieren. Many years ago, Dr. Toepler used this system to show strain 



Li 

A- 








U 




Ds 


ftj 


1 









I 




D 4 


1^" 

■* — 


. 2! .|~- 


D ; 


1 
1 

T" 


D 3 


—1— 



Figure 5 Basic schlieren diagram: S — light-source; — object; L 1 and L 2 — lenses 
(not necessarily or the same focal length) ; Fm — film or viewing screen; x 2 — focal point 
of rays from L % (image of source); K — limiter or knife edge; D t — distance, equal to 
focal length of L± ; D 2 — distance, not critical ; D 3 — locate O, which gives rise to the effect 
being studied, to give a sharp image at Fm. (Note — the object giving rise to the 
schlieren effect is focusable although the effect itself is not) ; D 4 — determined by and 
equal to the focal length of L 2 ; D 5 — distance, not critical but see Note under D 3 . 

or schlier in glass, hence the name. Basically, the system is merely an 
extension of the shadowgraph system described at the beginning of this 
section on photo-optical techniques. It is, however, capable of showing 
the presence of much smaller changes in density (refractive index) than the 
techniques already discussed. 

Starting from a point source, a parallel beam of light is achieved by 
placing a lens at a distance equal to its focal length from the light-source. 
This distance need not necessarily be known or calculated. A card should 
be placed close to the lens so that the light from the source shines through 
the lens, giving a circle of illumination on the card. The card can easily 
be marked with the diameter of that circle. The card should then be 
moved some long distance from the lens, but so that the circle of illumina- 
tion still impinges on it. The lens to point-source distance is then ad- 
justed until the circle of light projected on to the card is the same size as the 
original marked circle. This whole operation should then be repeated and 

IN-I 6 



checked. This then is a practical method of obtaining parallel light; the 
deviation from parallel is reduced the further the card is from the lens 
when checking the diameter. 

Having produced a parallel beam, which forms the working section, a 
second lens is used to bring the beam back to a focus. The second lens 
focuses all the rays from the parallel beam to a common focal point; the 
rays will then diverge again. A viewing screen or a film placed anywhere 
along and within this beam (beyond the focal point) will be evenly illu- 
minated. If an object of greater or lower density is introduced into the 
working section, the rays refracted and deviated from the parallel will no 
longer pass through the focal point. With a system using good-quality 
lenses and a monochromatic light-source, very small differences in density 
can be easily detected and recorded. A quite unsophisticated system can 
show the difference between air warmed by passing over a human hand 
and air at ambient temperature. 

The differences in density, produce refracted rays, which are shown as 
patches of greater or lesser intensity on an otherwise evenly illuminated 
field. Improved results can be achieved by the addition of a "limiter" or 
knife-edge, positioned so that it is just outside the beam at the focal point. 
This can be either a straight edge or a slit or even a pinhole. The edges 
must be "clean" and sharp, however, otherwise spurious diffraction effects 
can confuse the analysis . A suitable straight edge or slit is easily made. A 
new razor blade makes an ideal straight edge, whilst two placed near each 
other make a very good slit. If two razor blades are used to make a slit, 
hold them up to the light and adjust one in relation to the other to obtain 




Figure 6 Explanation and diagrams of schlieren principles : with no object (0) in the 
beam there is an evenly illuminated field. If an object refracts rays from the normal 
path, either one of two types of record will result. 

(a) Where a limiter or knife-edge (K) is not used or is not effective, the illumination, 
at the point the ray would have reached, will be less bright (— ) than the remainder of 
the field. That point of the field where the deviated ray does strike will show an 
increase (+) in brightness. 

(b) Use the limiter or knife-edge (K) to reduce or cut-off the deviated ray. This 
eases the analysis of the records produced, by reducing the number of increased ( +) 
brightness points. 



IN-I 



centimetre field. It should be borne in mind, however, that although 
the presence of such small particles can be shown, the image of these 
points is not necessarily a direct quantitative record of their size. 

Interferometry : When it is required to make a more quantitative assessment 
of the density changes in, for example, a gas flow, then yet another system 
may be employed. 

If a beam of monochromatic light originating from a single point-source 
is equally divided by some convenient optical system, two distinct wave 
trains identical in character will be produced. If, at a later point, these 
two beams are recombined, and providing that each beam has travelled 
exactly the same path length, the original composite beam can be recon- 
structed unchanged. This is the principle used in the setting up and 
operation of interferometers. 

In a system built as shown in Figure 9, the object should be placed in 
the parallel part of the system, which now consists of two slightly dis- 
placed beams. Exact recombination will not be possible because of 
the phase change introduced by the density gradient of the object. 
Destructive or constructive interference will occur in the recombined 
beam. Where for example the wave train is completely out of phase 
(half a wavelength), total destructive interference will occur, resulting in no 
light being transmitted, and where the light is in phase then an increased 
brilliance will be reconstructed. 





Figure 9 A schlieren-interferometer system : Pj and P 2 — polarizing filters (P 2 is 
often referred to as the analyzer) ; W x and W 2 — Wollaston prisms ; other symbols are as 
shown under Figure 5. 



This Data Sheet gives only some of the more common techniques as a 
guide and does not pretend to be comprehensive. Many variations on 
those described and much more advanced techniques are available; 
holography and allied techniques, for example, are not included in this 
Data Sheet as there is so much published in current literature. 



Kodak Data Sheet 
IN-I 



KODAK LIMITED LONDON 

PDIN-l/xWPI 1/3-71 



checked. This then is a practical method of obtaining parallel light; the 
deviation from parallel is reduced the further the card is from the lens 
when checking the diameter. 

Having produced a parallel beam, which forms the working section, a 
second lens is used to bring the beam back to a focus. The second lens 
focuses all the rays from the parallel beam to a common focal point; the 
rays will then diverge again. A viewing screen or a film placed anywhere 
along and within this beam (beyond the focal point) will be evenly illu- 
minated. If an object of greater or lower density is introduced into the 
working section, the rays refracted and deviated from the parallel will no 
longer pass through the focal point. With a system using good-quality 
lenses and a monochromatic light-source, very small differences in density 
can be easily detected and recorded. A quite unsophisticated system can 
show the difference between air warmed by passing over a human hand 
and air at ambient temperature. 

The differences in density, produce refracted rays, which are shown as 
patches of greater or lesser intensity on an otherwise evenly illuminated 
field. Improved results can be achieved by the addition of a "limiter" or 
knife-edge, positioned so that it is just outside the beam at the focal point. 
This can be either a straight edge or a slit or even a pinhole. The edges 
must be "clean" and sharp, however, otherwise spurious diffraction effects 
can confuse the analysis. A suitable straight edge or slit is easily made. A 
new razor blade makes an ideal straight edge, whilst two placed near each 
other make a very good slit. If two razor blades are used to make a slit, 
hold them up to the light and adjust one in relation to the other to obtain 




Figure 6 Explanation and diagrams of schlieren principles : with no object (0) in the 
beam there is an evenly illuminated field. If an object refracts rays from the normal 
path, either one of two types of record will result. 

(a) Where a limiter or knife-edge (K) is not used or is not effective, the illumination, 
at the point the ray would have reached, will be less bright ( — ) than the remainder of 
the field. That point of the field where the deviated ray does strike will show an 
increase (+) in brightness. 

(b) Use the limiter or knife-edge (K) to reduce or cut-off the deviated ray. This 
eases the analysis of the records produced, by reducing the number of increased (+) 
brightness points. 



IN-I 



the minimum parallel slit visible, then clamp them in position. Two to 
three thousandths of an inch wide slits are quite easily made in this way. 
Slits of this type are useful not only for limiters in the schlieren system but 
also as a means of producing a point-source of light (see Figure 3b). 

Variations on Basic Schlieren Techniques : The limits of the working area are 
restricted in this system to the diameter of the parallel beam. Obtaining a 
larger area can be very expensive with conventional lenses, however, 
mirrors can be used wherever the requirement is for larger working areas 
(see Figure 7). A further advantage of the mirror system is that the 
optical path can be folded to conserve room space; this also makes the 
use of longer focal length feasible, thus giving greater sensitivity. 




Figure 7 Folded-path schlieren, using mirrors : to avoid distortion, angle ^ should 
equal angle 2 y these angles should be as small as possible consistent with S and x 2 being 
outside the parallel section : other symbols are as shown under Figure 5. 

Dark-ground Schlieren : This variation is used if it is required to show, for 
example, the presence of very small particles (less than 5 microns) in a 
relatively large area or volume. This is a standard schlieren set up, as 
shown in Figures 5 and 7. The only modification is that the limiter or 
knife-edge is adjusted differently. 

If the limiter or knife-edge in a normal schlieren system is adjusted or 
moved so that it begins to intrude into the light beam, the screen will (if the 
optical system is correctly set up) darken evenly; if the knife-edge is then 
left in the position where the image of the light-source is just obscured 
(screen only just darkened), this condition is known as dark-ground 
schlieren. This technique also uses the "Mie" effect, that is the forward 
diffraction of light round small particles. In dark-ground schlieren, 
undeviated rays are cut off by the limiter whilst only those diffracted or 
refracted from their normal path are recorded. 



IN- 





ft 



4 



(a) Normal diffuse back lighting 



(b) Focused shadow 



4k 




(c) Schlieren 

Figure 8 Examples of four techniques. 



(d) Dark-ground schlieren 
These photographs are Crown copyright. 



Figure 8 shows the different types of results on a common subject with 
the same experimental conditions, that can be achieved by four of the 
various techniques discussed. 

The subject of the photographs is gas being bubbled into liquid. The 
most striking difference perhaps is the large number of small bubbles 
visible by dark-ground schlieren illumination (d), but not visible in the 
other photographs, although they are present in all. By this technique, 
particles down to a few micrometres in diameter can be seen in a 15 

9 IN-I 



centimetre field. It should be borne in mind, however, that although 
the presence of such small particles can be shown, the image of these 
points is not necessarily a direct quantitative record of their size. 

Interferometry : When it is required to make a more quantitative assessment 
of the density changes in, for example, a gas flow, then yet another system 
may be employed. 

If a beam of monochromatic light originating from a single point-source 
is equally divided by some convenient optical system, two distinct wave 
trains identical in character will be produced. If, at a later point, these 
two beams are recombined, and providing that each beam has travelled 
exactly the same path length, the original composite beam can be recon- 
structed unchanged. This is the principle used in the setting up and 
operation of interferometers. 

In a system built as shown in Figure 9, the object should be placed in 
the parallel part of the system, which now consists of two slightly dis- 
placed beams. Exact recombination will not be possible because of 
the phase change introduced by the density gradient of the object. 
Destructive or constructive interference will occur in the recombined 
beam. Where for example the wave train is completely out of phase 
(half a wavelength), total destructive interference will occur, resulting in no 
light being transmitted, and where the light is in phase then an increased 
brilliance will be reconstructed. 





Figure 9 A schlieren-interferometer system : Pj and P 2 — polarizing filters (P 2 is 
often referred to as the analyzer) ; W t and W 2 — Wollaston prisms ; other symbols are as 
shown under Figure 5. 



This Data Sheet gives only some of the more common techniques as a 
guide and does not pretend to be comprehensive. Many variations on 
those described and much more advanced techniques are available; 
holography and allied techniques, for example, are not included in this 
Data Sheet as there is so much published in current literature. 



Kodak Data Sheet 
IN-I 



KODAK LIMITED LONDON 

PDIN-l/xWPI 1/3-71 



THE PHOTOGRAPHY OF HIGH-SPEED EVENTS 



High-speed photography is a useful tool in many branches of scientific 
and technical work and is being increasingly applied in industrial problems 
of all types. Not only does the method allow the recording of phenomena 
too rapid for the human eye to follow, but precise analyses of the various 
phases of action can be obtained for study at leisure if a series of images are 
recorded in rapid succession, together with a simultaneous record from 
some type of precision chronograph to form a time base. 

The method adopted for the photography of high-speed events depends 
principally on three factors : 

1 Whether a single picture only is required, or whether it is desired to 
obtain a complete set of images at known intervals of time. Although a 
single picture is often of use as a sample to show the exact conditions 
prevailing at any known instant, a complete analysis with respect to time 
can only be obtained by consideration of a series of images taken at known 
time intervals or by means of some special form of continuous record. 
Pictures in the ordinary sense are sometimes not necessary, for example, in 
some cases where symmetry may be assumed, it is sufficient to place a slit 
across an image of the object, and to scan this slit along a film at a known 
rate. In this way, the motion of the light-emitting object may be accu- 
rately measured without taking a picture or series of pictures of the whole 
object. 

2 The displacement, speed, and duration of the phenomenon to be 
examined. These determine the length of exposure required for each 
picture and, if a sequence is required, the frequency of exposures, the rate 
of travel of the film and the length of film required to record the whole 
action. If the relative velocity of movement between the image of the 
subject and the film is great, owing either to the movement of the subject 
or the film, the exposure time must be correspondingly short in order to 
avoid blurring of the record. If, during exposure on cine film, the image 
travels more than 25|Jm (0.001 inch) across the film, noticeable loss of 
definition will be produced when the result is analysed or projected though 
the actual figure which can be tolerated depends on the subject and the 
accuracy of analysis required. In still photographs which are not enlarged, 
blurring of 250nm (0.0 1 inch) or even more may not be objectionable. In 
certain cases, it may be preferable to use a high shutter speed with relatively 
low picture frequency, while in others it is necessary to use a high picture 
frequency in order to record the motion effectively. For example, an event 
recorded at say 1600 f.p.s. and projected at 16 f.p.s. gives an apparent 
decrease in speed, in the motion to be studied, of 100 times. It is not 
possible in general to state an overriding rule as to the correct camera speed 
to be used and it is necessary to consider each case separately. 

3 Whether the subject is self-luminous or requires to be illuminated. 
Some subjects may be highly self-luminous, such as flames, electric sparks, 
shock waves, or explosions, and it may be sufficient to use the light emitted 
by the phenomenon for taking the required picture. On the other hand, 

Issue E Kodak Data Sheet 

IN-2 



some subjects are completely non-self-luminous and will require to be 
illuminated by one or more external light-sources. Occasionally, where, 
for example, a non-luminous particulate matter such as a powder is 
present in a flame, direct lighting of the particles may have to be balanced 
with the self-luminous flame. If the phenomenon has a total duration in 
the range 100 microseconds to 1 millisecond, then one of the following 
illuminants will be required — a spark gap, a discharge tube, a pulsed laser, 
or a shock wave produced by a small explosion moving through a gas, such 
as argon, contained in a disposable case with a transparent end window. If 
the total duration of the phenomenon is much longer than this, i.e., of the 
order of 1 second, then fairly normal projection lamps may be used; if 
necessary overrun for a short time to produce the required amount of light. 
In general, it may be stated that the methods of high-speed photography 
fall under the following main headings : 

1 Normal high-speed cine cameras. 

2 Flash systems. 

3 Streak cameras. 

4 Framing cameras. 

5 Single-shot and short-exposure cameras. 

6 Image-dissection cameras. 

7 Flash X-ray methods. 






Figure la 



Figure lb 



Figure la. Shows the well-known 2 f.p.s. to 500 f.p.s. register pin intermittent 
camera from D. B. Milliken (courtesy of Telford Products Limited, Greenford, who 
are the Milliken agents in this country). The Milliken DB-54 illustrated has 
a 400 foot internal capacity and will accept a 1200 feet external magazine. The 
exposure range can be varied from 1/5 second to 1/19 000 second 

Figure I b. Shows three consecutive frames of a film taken at 500 f.p.s. on a Milliken 

intermittent motion camera and is shown by courtesy of The Bifurcated and Tubular 

Rivet Company. The film was taken by The Central Unit for Scientific Photography 

to confirm the accuracy and correct functioning of the machine at high speeds 



IN-2 



I High-speed cine cameras, recording on standard cine film, form the 
type of camera most commonly used in this field. In the main, these are 
16 mm, although 8, 35 and even 70 mm cameras are available and are used 
where appropriate. The choice of format is dependent on the number of 
image points per unit area to be recorded, and the mechanical limitations 
imposed by the use of that format. The use of the 35 mm format at 
2000 frames per second requires a speed of travel or throughput of film of at 
least 125 feet (38.1 m) per second; whilst 16 mm film at the same framing 
rate requires a throughput of only 50 feet (15.24 m) per second; the power 
required to accelerate film and the consequent stress on the film tends, 
therefore, to set practical limits on the equipment. 

Two main types of high-speed cine cameras are available, those having 
intermittent film movement and those having a continuous film movement. 
Intermittent cameras, usually fitted with a register pin or pins for increased 
picture stability, normally operate in the speed range of up to 600 frames 
per second with 16 mm film, although a 1000 frame per second 16 mm 
intermittent camera design was reported at the 1970 High Speed Photo- 
graphy Conference at Denver. 



SECOND FIELD 
LENS 



SECOND PRISM 

SEGMENTED SHUTTER 




EYEPIECE OR 

OSCILLOSCOPE FINDER 

LENS prism 



APERTURE 

MASK 

(FIDUCIAL) 



FILM 
SPROCKET 



FIRST FIELD LENS 



Figure 2. Diagram showing the optical layout of a modern rotating prism camera — 
the Red Lake Laboratories 'Hycam' (courtesy of J. Hadland (PI) Ltd) 

High-speed rotating prism cine cameras are used perhaps more fre- 
quently than high-speed intermittent cameras. Such cameras may be 
run at speeds of up to about 10 000 (full 16 mm frame) or 40 000 (normal 
16 mm frame width 2 mm high) frames per second, although they are 
more frequently used at somewhat lower speeds, i.e., in the range 1000 to 
5000 frames per second. 



IN-2 



At all these framing rates, when continuous motion of the film is essential, 
shuttering may be achieved by the use of a rotating shutter placed between 
the lens and the film, and the relative motion of the film and the image 
compensated to a large degree by means of a rotating block of glass, usually 
integrated with the shutter. With care in design, the degree of compen- 
sation for the image motion may be made so good that high picture defini- 
tion may be obtained. At the highest speeds or where optical and 
mechanical simplicity is required, the separate shutter is discarded and the 
edges of the compensating block are capped and act as drum shutter. 

In order to measure the rate at which the film is moving or to measure 
the rate at which the pictures are being taken, a time base is frequently 
impressed upon the edge of the film; this usually takes the form of short- 
exposure sparks which are running at a known rate, governed by a tuning 
fork or, more commonly, a crystal-controlled oscillator or a multi-vibrator 
may be used to govern flashes from a neon or light-emitting diode. An 
image of the sparks or neon or light-emitting diode is projected on to the 
edge of the film and is recorded as a series of marks. 

2 Flash Systems. It is possible to dispense with the rotating shutter 
of a rotating prism camera, and with the optical compensating block, if 
the illumination of the object is done by short-duration flashes of light 
occurring at the rate at which pictures are required, and having enough 
intensity to illuminate the object which it is required to photograph. It is 
important to remember however that the duration of the flash is even more 
important than the interval between the flashes. The flash should be of 
sufficiently short duration to overcome relative image-to-film movement. 
Obviously, this form of high-speed camera is applicable only to non-self- 
luminous objects, and where the ambient light is low enough not to give 
enough light to form an image. 

3 The principle of the streak camera has already been touched upon in an 
earlier section. Most rotating prism cameras can be used as streak 
cameras by removing the shutter and image compensating block. Alter- 
natively, it may consist of a mirror which is rotating at a high speed 
and which scans an image along a strip of film which is arranged as an arc of 
a circle centred on the centre of rotation of the mirror. The object to be 
examined is imaged by a lens on to a slit, and the light which passes through 
the slit is focused by a lens on to the film, after reflection from the rotating 
mirror. The image of the slit on the film is arranged to be at right-angles 
to the direction of scan along the film when the mirror rotates. Using 
such a camera, the motion along the length of the slit of the light emitted 
by the object may be recorded on the film, and if the rate of scanning along 
the film is known, then the velocity of movement of a light-front along the 
slit may be derived by the measurement of an angle on the film. One of 
the limitations of this method is that it gives information about the motion 
of the light-front only in one direction, i.e., along the slit. It can be 
assumed in some cases that symmetry exists and it can therefore be postu- 
lated that motion of a light front along the slit applies to the motion of a 
light front in any other direction, but this postulate may not always be 
justified. 

Many such cameras have been designed and built, using either a turbine 
drive for the mirror or a high-frequency electric drive. For the lower 

IN-2 4 




Figure 3. The essential features of a Streak Camera 

speeds, it is often sufficient to use a more or less conventional electric motor, 
with a belt drive to give an increased speed of rotation of the mirror shaft. 
For the higher speeds, as air turbulence causes mirror erosion and optical 
distortion, it is necessary that the mirror should be rotating in a vacuum, 
reduced pressure, or in helium to remove the decelerating effects of air tur- 
bulence. These cameras have been successfully operated at mirror rota- 
tional rates of up to about 300 000 revolutions per minute, giving speeds 
of scan along film of the order of centimetres per microsecond, and time 
resolutions of the order of nanoseconds. In general, this method is applic- 
able mainly to subjects which are highly self-luminous, as the aperture of the 
system is usually fairly small and a large amount of light is required to 
obtain a satisfactory record. 

4 Framing cameras are in many ways similar to streak cameras in that 
they employ a high-speed rotating mirror and a film arranged along an 
arc of a circle. However, the main difference is that the framing camera 
takes a series of discrete pictures of the whole object and produces a result 
looking like a short length of cine film. This is achieved by forming an 
image of the object to be recorded on the surface of the rotating mirror. 
The light reflected from the mirror is then imaged by a series of small sub- 
sidiary lenses on to the film. The duration of the exposure in each of the 
subsidiary images is governed by the time which it takes for the light 
reflected from the rotating mirror to pass across each subsidiary lens. 
The number of pictures is determined by the number of subsidiary lenses 
and is usually in the range 30-100. The picture size is usually fairly small 
but good definition may be obtained. 

With mirrors rotating at the same sort of rotational speeds as those in the 
streak camera, picture frame-rates of up to about 10 7 per second have been 
successfully obtained, the exposure in each picture being about 0.1 micro- 
second or less. Again, for the higher speeds, the mirror needs to be con- 
tained in a vacuum or similar, and pictures may be obtained only if the sub- 
ject is highly luminous or is illuminated by a very intense light-source. 

In the case of both the streak camera and the framing camera, it is 



IN-2 




Figure 4. Barr and Stroud CP-5 Framing Camera 

usually necessary to synchronize the occurrence of the event to be studied 
with the position of the rotating mirror to a high degree of accuracy. 
This is a considerable limitation as there are many subjects the initiation of 
which may not be accurately synchronized. Some streak and framing 
cameras have been designed with continuous access, in other words, no 
matter when the event occurs, records will be obtained, but this leads to 
considerable complications in the design of the camera and in general is 
uneconomic in both cost and light. 



TRANSFER LENSES 




SECONDARY LENSES 



MAIN LENS 

Figure 5. Principle of rotating-mirror framing camera with diaphragm 



IN-2 



One further difficulty with the use of streak and framing cameras is 
that if the total duration of light emission from the object is longer than the 
time for one half-revolution of the mirror, then a second set of images or 
streaks will tend to be recorded on top of the first set which have already 
been recorded. To prevent this, some form of capping shutter must be 
employed, and several successful designs have been developed. These 
capping shutters are required to effectively close the camera within times of 
the order of 10 microseconds. For objects which remain highly luminous 
for much longer periods, an ordinary mechanical shutter may be required 
as well as capping shutter. 

5 Single-shot cameras are usually of the Kerr-cell or image-tube variety. 
The Kerr-cell consists essentially of a small vessel filled with nitro- 
benzene placed between two polarizers whose planes of polarization are set 
at right-angles to each other and at 45° to the electrical field. In this 
condition, no light may pass through the system. When an electrical stress 
is applied to the nitro-benzene, its birefringent properties may be altered 
in such a way that light may pass through the second polarizer, and the 
cell may then be used as a shutter, through which the duration of exposure 
is governed by the duration of the electrical stress on the nitro-benzene. 
Using such a system with a lens and a film, exposures down to a few nan- 
seconds have been recorded, with good image quality. 

Both the Kerr-cell shutter and the image-tube may be accurately 
triggered from an event, and the delay in operation after the reception of a 
triggering pulse may be kept quite short, i.e., a fraction of a microsecond. 
The main difference between the Kerr-cell shutter and the image-tube 
shutter may be summarized as follows : 

The Kerr-cell shutter can in general be expected to give somewhat better 
images quality, but can also be expected to be less sensitive than the image- 
tube shutter, i.e., it requires more light to obtain a satisfactory picture. 
This is due to two reasons; firstly, the Kerr-cell shutter contains two 
polarizing screens and nitro-benzene, all of which will absorb some light, 
and, secondly, it has no actual gain. The Kerr-cell is also not in general 
satisfactory for operation with wide-aperture lenses . The image-convertor 
camera can be used with any lenses which can be obtained and can in fact 
be arranged to give a light gain within itself rather than a light loss. Its 
picture will however suffer from electron-optical distortions, though with 
care these can be made small. 

Commercially available image converter cameras originally made use of 
grid shuttering tubes. Such systems, although highly developed have 
severe shortcomings. The sinusoidally shuttered image tubes pioneered 
by the United Kingdom Atomic Energy Authority gave the oppor- 
tunity for the development of a unique image converter system free from 
the shortcomings associated with the earlier tubes. The later system 
retains the features of fast triggering, high optical aperture, high record- 
ing speed, and the versatility of the system is considerably increased as 
sinusoidally shuttered tubes have flat cathode areas. 

The sinusoidally shuttered image tube has three pairs of deflector plates 
in the drift space between anode and screen. The first pair of plates act as 

7 in-2 



shutter plates and, when a sinusoidal oscillation is applied to them, deflect 
the electron beam up and down across an aperture slit. The electron 
beam can only get through the plate when it is crossing this narrow slit 
and this gives repetitive shuttering. However, this electron beam is 
moving as it passes the slit and, without this, correction would produce 
blurred pictures on the phosphor. To arrest this blurring movement, a 
second sinusoid of the same frequency and amplitude, but of different 
phase, is applied to a second pair of deflection plates, known as the com- 
pensating plates, on the other side of the aperture plate. As shuttering 
takes place each time the sine wave passes through zero voltage, there are 
two exposures per cycle. Images are therefore produced in pairs at the 
phosphor. To separate the superimposed pairs of pictures, a staircase volt- 
age is applied to a third set of deflectors called shift plates, which are 
positioned in a plane normal to the electron beam and at right angles to 
the plane of the shuttering plates. The staircase is based on the same 
sinosoid and is therefore synchronized so that its steps occur between 
alternate exposures. Thus, two rows of pictures can be produced, the 
framing rate being twice the frequency of the applied sinusoids and the 
number of pictures twice the number of steps on the staircase. 



PHOT0CATH0DE 



ANODE 




SHUTTER COMPENSATING 
PLATES PLATES 




Figure 6. Principles of the Image Converter Camera 



IN-2 



The advantage of this system is that the changing of sinusoids and 
staircases is simply produced by plug-in passive, tuned circuits. A 
potentiometer in each plug-in unit can be used to vary the number of 
frames from 6 to 20. 

Substitution of a plug-in unit which provides a switched even ramp 
voltage of selected gradients to the final deflector plates, and keeps the 
other deflectors at zero voltage, provides a simple and highly efficient 
system of making selected speed streak images. In both streak and fram- 
ing operation, the electronic beam is guillotined when maximum deflection 
of the electron beam has occurred. The tube is thus cut off and no light 
break through can occur. 

Two triggering systems are available with framing plug-in units. The 
standard system is a triggered system which awaits the trigger pulse 
before commencing the sinusoid shutter deflection, and it is the first step of 
the staircase which brings the first pair of pictures on to the phosphor. 
Another system, known as "Two Frame Standby", requires two trigger 
pulses, the first prior to the event starting the sinusoid shuttering, and the 
second at event time zero, starting the staircase. In this system the 
staircase bias is usually set so that the first pair of pictures is already on 
the phosphor, thus recording the event before event time zero. 






Figure 7. The best known image converter camera of the type described is the Ima-con 
made by John Hadland (PI) Ltd. 



IN-2 



The technique of gated picture ranging, previously used with nano- 
second pulses has recently been extended to the picosecond range, with 
a resolution of about 1 cm being demonstrated. This was done with a 
camera developed by "The Bell Telephone Laboratory"; this camera 
gives a 10 picosecond frame interval. An appreciation of this time can 
be gained by considering that light itself will only have moved approxi- 
mately 3 mm in 1 picosecond. 

6 Image-dissection devices have been used to record a series of pictures 
of objects which are changing rapidly in their configuration. In principle, 
an image-dissection device operates by forming the image as a series of 
small dots. These are separated by distances large compared with the dot 
size, but the number of dots per image is large enough to allow of reason- 
able definition. Since most of the picture consists of space where no dots 
occur, then by a slight movement it is possible to record a second picture 
and indeed many pictures before there is any possibility of overlapping. 
The final result will consist of a composite of all the pictures obtained, and 
any one picture may be unscrambled only by re-projection through a 
system similar to that with which the picture was obtained. 

The image dissection has been performed in the past in two main ways — 
by the lenticular plate, and by the use of an image tube, the photo-cathode 
of which consists of a mosaic of small photo-electrically emitting areas on 
an otherwise inert glass surface. Both these methods enable a sequence of 
pictures to be obtained with reasonable definition for many purposes, and 
the lenticular-plate system has the advantage of relative simplicity and 
cheapness. 

7 In some cases, the events to be studied are occurring behind a screen 
which would prevent light from passing to the camera; in this case X-rays 
may be used to obtain a picture in the form of a shadowgraph. If a short 
duration flash of X-rays is produced, then the result will be a short- 
exposure X-ray picture of the event. The obscuring screen may either be 
a solid object, for example, when recording the flow of materials inside a 
hopper, or it may be a cloud of obscuring smoke such as that occurring 
during an explosion. The main problem in this technique is to produce a 
short-duration, high-intensity burst of X-rays. There is a fairly extensive 
literature on the subject and exposures in the region of 10" 8 second have 
been recorded. Short picture sequences are possible by using either a 
separate source for each picture or by repeated flashing of a single X-ray 
tube, up to 10 5 pictures per second. The X-ray picture is produced on 
normal X-ray film sandwiched between intensifying screens, or by filming 
the X-ray image on a normal fluoroscopic screen. The use of a fluoro- 
scopic screen has the advantage of simultaneous viewing of the screen by 
the research worker; but because of the low light output of these screens 
some form of image intensification is normally required for photography 
using high-speed cameras. 

Special techniques 

A number of subsidiary techniques may be used in conjunction with 
high-speed photography to render visible the passage of, for example, 
shock waves. The shadowgraph and schlieren techniques both utilize the 

IN-2 10 



refraction of light, in a medium of changing density, to render visible on a 
photographic emulsion regions in which the density of the medium has 
changed. Interferometric techniques use the variation of optical path- 
lengths in a medium of varying density in order to show up the outlines of 
regions of varying density by the movement of interference fringes. These 
subsidiary techniques may in general be used with any of the previously 
mentioned methods for high-speed photography. 

Data Sheet IN-1 gives in more detail some of these techniques, as used 
in the study of fluid flow. 

Emulsions 

In general, it may be said that the speed of an emulsion for high-speed 
photography is indicated roughly by the speed rating for normal use, al- 
though the difference between emulsions may not be so great as this sug- 
gests. Some work is being done to measure the relative speeds under 
short-exposure conditions, see pages 379-382 and 388-392 of the Pro- 
ceedings of the Sixth International Congress on High-Speed Photography 
(see Bibliography). 

Frequently, it is not possible to decide in advance which emulsion gives 
the optimum results — too fast an emulsion introduces graininess, while 
too slow an emulsion gives either a very weak image or none at all. The 
measurement of the light intensity on an absolute basis for short intervals of 
time is difficult, and more work is needed on this aspect of the subject. 

Special developing techniques and special developers are often used in 
this field to give increased effective film speed, details of a few of the more 
common methods are given in Data Sheet GN-7. 

Applications 

High-speed photography is being widely used by industry, by Govern- 
ment departments, and by universities for a wide range of problems. The 
subjects which have been studied by high-speed photography include the 
observation of the behaviour of machinery at high speeds; the functioning 
of electrical relays; the flow of metals during punching operations; the 
behaviour of high-speed weaving and knitting machinery; welding; the 
flow and burning of fuel and air in petrol and diesel engines; the shattering 
of glass under impact; a large number of problems associated with the 
design and stability of aircraft; the aerodynamic behaviour of a wide range 
of objects such as street decorations, television aerials, motor-cars, suspen- 
sion bridges, chimneys, and boiler-tubes; the measurements of blood-cell 
velocity in living animals; cavitation in hydraulic machines; boundary- 
layer flow on screw propellers; nucleate boiling of liquids; the motion of 
live biological specimens; and the motion of the human vocal chords 
emitting different sounds. 

High-speed photography has also been extensively used to record the 
behaviour of explosives, and is proving extremely useful in research on 
thermo-nuclear reactions. This list of applications is not intended to be 
exhaustive, but is merely indicative of the sort of problems which have 
been studied by means of high-speed photography. Reference to the 
literature on the subject will produce many more examples in these and 
other fields. 

II IN-2 



Bibliography 

W. D. Chesterman, The Photographic Study of Rapid Events, Clarendon 
Press, Oxford, 1951. 

P. Naslin and J. Vivie (editors), Photographie et Cinematographie Ultra- 
Rapides {Proceedings of the Second International Congress on High-Speed 
Photography and Cinematography, Paris, 1954), Dunod, 1956. 

R. B. Collins (editor), Proceedings of the Third International Congress on 
High-Speed Photography {London, 1956), Butterworths, 1957. 

J. S. Courtney-Pratt, A Review of the Methods of High-Speed Photography, 
Reports on Progress in Physics, 20, pp. 379-432, 1957. (This review 
contains a large number of references up to about 1957). 

E. L. Garvin (compiler), Bibliography on High Speed Photography, 
Eastman Kodak Company, Rochester, New York, U.S.A., 1960. (This 
contains references up to about the end of 1959). 

Kurzzeitphotographie {Proceedings of the Fourth International Congress on 
High-Speed Photography, Cologne, 1958), Helwich, 1959. 

J. S. Courtney-Pratt (editor), Proceedings of the Fifth International Congress 
on High-Speed Photography, New York, 1960, Society of Motion Picture 
and Television Engineers, 1962. (This contains over 100 papers on 
aspects of high-speed photography). 

W. G. Hyzer, Engineering and Scientific High-Speed Photography, Mac- 
millan, 1962. 

J. G. A. de Graaf and P. Tegelaar (editors), Proceedings of the Sixth Inter- 
national Congress on High-Speed Photography, The Hague, 1962, Tjeenk 
Willink (Haarlem), 1963. 

E. W. Tapia (compiler), Bibliography on High-Speed Photography, 1960-64, 
Eastman Kodak Company, Rochester, New York, U.S.A., 1965. 

G. H. Lunn, HSP7, Perspective, 8, No. 4, 1966, pp. 5-17. (A review of 
the Seventh International Congress on High-Speed Photography, 
Zurich, 1965). 

R. F. Saxe, High Speed Photography, Focal Press, 1966. 

E. W. Kraus, Current Bibliography on High Speed Photography, 1964- 
1970, from proceedings 9th Int. Conr. High Speed Photography 1970. 
Entries in this are classified under the headings — general, cameras, light- 
ing, oscillograph photography, Schlieren photography, technical and 
techniques, X-ray. 

M. A. Duguay and A. T. Mattick (Bell Telephone Laboratory, Murrey 
Hill, N.J., U.S.A.), Applied Optics, 10, No. 9, 1971, pp. 2162-70. 



Kodak Data Sheet KODAK LIMITED LONDON 

IN-2 

Y 1 223PDIN-2/XWPI 0/2-72 



PHOTOGRAPHY IN THE DRAWING OFFICE 



Photography plays an important role in the reproduction of drawings 
and tracings produced by engineers and architects, both at full scale, as 
duplicate working plans, or on a reduced scale, e.g. for ease of storage and 
reference. The two broad categories of reproduction are by "Contact 
Copying," and "Projection Copying." Both methods can provide 
"same-size" copies, while projection copying, which entails the use of 
equipment incorporating a lens system, can also provide reduced or 
enlarged copies. 

CONTACT COPYING 

KODAK 'Instafax' CT process 

This diffusion-transfer process provides a quick, easy, and relatively 
inexpensive means of reproducing documents. The process is extremely 
versatile in use and with the appropriate materials and chemicals, it is 
possible to make satisfactory copies of a wide range of very different 
originals. 

Kodak 'Instafax' CT materials are suitable for all copiers using the 
diffusion transfer method. These materials provide an ideal means of 
making one or two copies, air-mail copies, double-sided copies and 
translucent intermediates for dye-line printing. Full details of the 
'Kodak' diffusion-transfer process are given in Data Sheet DC-4 or may 
be obtained from the Instafax Sales Department, Kodak Limited, P.O. 
Box 66, Kodak House, Hemel Hempstead, Herts. 

KODAGRAPH 'Autopositive' papers 

Photographic materials which are of special interest in the drawing 
office are the Kodagraph 'Autopositive' papers. They provide a means of 
producing a direct positive copy from an original by contact printing and 
normal development. They are of suitable speed for exposure in a dye- 
line machine, or in a contact-printing device having high-intensity 
illumination. Regardless of the type of illumination employed, 'Koda- 
graph' Sheeting, yellow must be used. The filter may be placed anywhere 
between the light-source and the sandwich of the original and the printing 
paper, all other light having been excluded. 

The contrast attainable in the image produced on 'Autopositive' papers 
is exceedingly high; it is thus possible to produce copies of greater 
legibility than the original. 

'Kodak' Auto-Processor, Model Q33J84 : This is a surface-application 
processor for the automatic processing of copies of engineering drawings, 
etc., up to 84 cm (33 inches) wide, at the rate of 3m (10 feet) of paper per 
minute. It is designed to process Kodagraph 'Autopositive' papers and 
'Kodagraph' Q papers. 

Further details of these papers and their methods of use may be found 
in Data Sheet DC-1. 

Issue G Kodak Data Sheet 

IN-5 



'Kodak' negative papers 

Slow-speed 'Kodagraph' contact papers are suitable for making reflex 
or transmission negative copies of drawings and plans. These can be 
handled in subdued room lighting. The copy thus obtained will be a 
mirror-image negative, which must be printed by transmission on to 
another sheet of paper to obtain a positive reproduction of the original, 
or, if dye-line prints are required, on to one of the series of 'Kodagraph' 
materials made for use as intermediates in the dye-line process. See 
"Duplicate intermediates for dye-line printing". 

Originals may be copied on a contact printer which incorporates the 
'Kodagraph' Sheeting, yellow, necessary for the making of optimum- 
quality negatives. An additional requirement, when copying large 
originals, is that the printer should be equipped with a vacuum blanket 
to ensure good all-over contact between the sensitized material and the 
original, and thus avoid loss of definition. 

'Kodagraph' contact and 'Autopositive' papers are often used to make 
additional copies of dye-line prints. The sheeting described above 
helps to produce excellent copies from dye-line prints, using the reflex 
printing technique. (Further detailed information on both the reflex and 
the transmission printing techniques will be found in Data Sheet DC-1.) 

Duplicate intermediates for dye-line printing 

Copies of original tracings, etc., are often required to serve as inter- 
mediates for the production of dye-line copies for the following reasons. 

1 The originals themselves may be valuable. 

2 The originals may not be robust enough to withstand the wear and tear 
involved in being passed repeatedly through a dye-line machine. 

3 The originals may not be sufficiently high in contrast to produce satis- 
factory dye-line prints direct. 

4 When more than one master is required, e.g., for sending to branches, 
or when a great number of dye-line prints is required and more than one 
intermediate would facilitate their production. 

Intermediates can be made from the original on to Kodagraph 'Auto- 
positive' Intermediate Paper, AI or on to micro-thin, ultra-thin or trans- 
lucentized papers. 

Transmission negatives can also be made from original tracings on 
to 'Kodagraph' contact papers, and positive intermediates can then be 
made from these negatives. A 'Kodagraph' translucent paper and a 
'Kodagraph' contact film have sufficient transparency and toughness for 
repeated use in a dye-line machine. 

PROJECTION COPYING 
Camera copying 

Drawings and other documents can be photographed with almost any 
commercial or copying camera. The negatives produced can then be 
enlarged on to one of the special projection document papers or film. 

The choice of negative material is dependent largely on the type of 
original, and suggestions are classified in a table given in Data Sheet GN-1. 

IN-5 2 



Sensitized materials 

Papers are available in a variety of base thicknesses and surfaces which 
make them suitable for a wide range of purposes. Some of them have 
developer-incorporated emulsions which enable them to be stabilisation 
processed in automatic processing machines. Such papers are, for 
example, 'Kodagraph' Projection Paper, PI; 'Kodagraph' Projection Print 
Paper, PP and 'Kodagraph' Projection Q Paper, Rough Single Weight, 
PRQ5. 

A translucent paper, 'Kodagraph' Projection Waterproof Translucent 
Paper, PWT 89 and a film, 'Kodagraph' Projection Film 2691 ('Estar' 
Base), are also available. 

'Statfile' recording 

The 'Statfile' system is of particular value in saving storage space occupied 
by drawings or other large documents. Originals of any size up to 
approximately 1 X 1.5 m (40 X 60 inches) are reduced down on to relatively 
small film negatives. These negatives, on safety film, can be stored very 
easily in a small space and are more accessible than the originals. 

When using the 'Statfile' Recorder No. 3, the original is placed in the 
easel and, according to its size, the camera trolley is locked on the bed at 
the appropriate reduction stop and the lens focused by lining up a pointer 
to the corresponding pre-set mark on the focusing scale. Negatives are 
made on 'Kodagraph' Ortho Film K05, a fine-grain, orthochromatic, 




Figure 



'Statfile' Recorder No. 3 



IN-5 



sheet-film material, 12.1 x 16.5 cm (4f X 6| inches) in size; the originals 
may be of any size up to 1 X 1.5 m (40 X 60 inches). The films are 
loaded into standard double film-holders or, where large quantities of 
work are being handled, a special roll-holder may be used, taking a roll 
which can accommodate up to 300 exposures. 

The 'Statfile' Recorder No. 3 (see Figure 1) can quickly be converted 
into an enlarger by means of which the negatives may be enlarged back 
to the original or any intermediate size. This is done by replacing the 
camera-back with an illuminating head and negative carrier. By making 
enlargements direct on to very-thin or translucent-base materials, trans- 
lucent copies can be produced photographically from original drawings 
for subsequent diazo printing. This completely eliminates any need for 
checking and thereby gives a great saving of time. 

Further details of the range of 'Kodak' and 'Kodagraph' materials 
suitable for drawing reproduction and of 'Statfile' equipment are available 
from Industrial Photo-Methods Sales, Kodak Limited, P.O. Box 66, 
Kodak House, Hemel Hempstead, Herts. 

'Recordak' copying 

In this process the originals are recorded by means of special microfilm 
machines on to 16 mm or 35 mm film. An example is shown in Figure 2. 

Several readers and printers are available for viewing the microfilm 
images so produced. 




Figure 1 Recordak 'Micro-File' Machine, Model HMRG-1 



IN-5 



The compact, automatic Record ak 'Prostar' processor processes 16 mm 
and 35 mm film at 5 or 10 feet per minute (1.52 or 3.04 m per minute). 

Further details are given in Data Sheet DC-1, or may be obtained from 
the Recordak Sales Department, Kodak Limited, 246 High Holborn, 
London, W.C.I. 



IN-S 



The following product names appearing 
in this publication are trade marks 

KODAK 

AUTOPOSITIVE 

ESTAR 

KODAGRAPH 

MICRO-FILE 

PROSTAR 

RECORDAK 

STATFILE 



Kodak Data Sheet KODAK LIMITED LONDON 

IN-5 

YI257PDIN-5/xWPI0/4-72 



PHOTOGRAPHIC TECHNIQUES IN WORK STUDY 



Work study is the analytical investigation of operational movements and 
the development of efficiency in all its ramifications. There are four 
photographic techniques available to the work-study practitioner. These 
are record photography, chronocyclegraph study, micromotion study, and 
memomotion study. Record photography is placed first on this list 
because of its relative importance; it is an extremely valuable method 
in both method and time study. The other three techniques are used, 
principally, as tools of method study. 



RECORD PHOTOGRAPHY 

Still photography can be used to advantage in almost every investi- 
gation involved in work study. It is a very versatile technique and, 
fortunately, it needs only a minimum of both photographic equipment 
and technical knowledge. 

Photographs, taken in a few seconds, can easily and accurately record 
current practices and layouts. As a means of reporting, photographs 
indicating, for example, a badly utilised stores area, will have a much 
greater effect on a remote management than the most detailed description. 

Two photographs taken at different times, from exactly the same view- 
point, of for example racks of steel tubing, will if superimposed one on the 
other, quickly show those items which have or have not moved. From 
this sort of study, better work flow systems can be instituted. 

For the time-study engineer, a photograph showing an accurate record 
of layout and conditions would make clear, at any time in the future, 
any changes which might have occurred; it could be difficult to detect 
these from a standard-practice write-up alone. 

A further valuable use of photographs, taken originally for record 
purposes alone, is in the training of personnel on particular operations 
and in demonstrating techniques and methods. 

An important point is to record only what is required to appear in the 
final print — the viewfinder should be filled, as far as possible, with the 
subject matter. 

Cine photography is sometimes a must for obtaining records — parti- 
cularly of handling operations. It can be used to record existing methods 
e.g. loading a vehicle. It is also likely to be more effective than a detailed 
report on, for example, a demonstration of mechanical handling equipment. 

Equipment 

With the high sensitivity of films now available it is unnecessary to 
use an expensive camera. With the aid of flash almost any camera is 
suitable, at least for a large proportion of the work to be done. However, 
if a range of slow shutter speeds is available, with a time-exposure setting, 
all types of record photography can be undertaken. 

Issue D Kodak Data Sheet 

IN-7 



Film 

The use of colour film, such as 'Kodachrome' II or 'Kodachrome-X' 
(see Data Sheet FM-2A or FM-2B, respectively), in a miniature camera 
and using flash illumination allows colour pictures to be produced 
more easily than can monochrome pictures; the resulting colour trans- 
parencies, when projected, are of the greatest value for close study. 
Records in colour show details even better than fine-grain monochrome 
film, the colour very usefully differentiating the various components of 
the subject. 

For demonstrational and educational purposes especially, colour film 
is the ideal recording medium, and the ability to project the small slides 
to almost any size, without any significant loss of detail, allows them to 
be shown satisfactorily to the largest audience. 

'Kodak' High-Speed 'Ektachrome' Film (see Data Sheet FM-1B) 
which has a sensitivity higher than that of many monochrome films, can 
be even more useful to the work-study engineer. Another colour 
material which can be very useful is 'Kodacolor-X' Film (see Data 
Sheet FM-4A) which gives a colour negative from which can be obtained 
as many colour prints or enlargements as are required. These can be 
used easily and efficiently to illustrate reports. 

When monochrome results are required the most suitable films are 
those with a slow or medium-speed emulsion, such as 'Panatomic-X' 
(see Data Sheets FM-47 and FM-51), 'Plus-X' Pan (see Data Sheets 
FM-48 and FM-52), or ' Verichrome' Pan (see Data Sheet FM-49). Prints 
or enlargements should be made on glossy paper of about postcard size, 
3|x5 inches; these are large enough for the first examination or for 
including in reports. 

CHRONOCYCLEGRAPH STUDY 

The chronocyclegraph is a means by which the path of a movement 
made by an operator's hands, or other parts of the body, is presented 
pictorially. It is obtained by affixing, to the operator, small pea-lamps 
which are made to flash on and off at a known frequency. The photo- 
graphic record is then produced by making a time exposure of a single 
cycle of the operation. This enables the whole path of the movement 
to appear as a trace on the photograph. A second exposure, by flash, may 
be given on the same frame in order to establish the position of the 
operator relative to the work. Figure 1 shows a simple chronocyclegraph 
illustrating the folding of towels. To avoid too many tracks being super- 
imposed one on another and thus making interpretation and analysis more 
difficult, the study may have to be broken down into convenient sections ; 
dependent on the size and complexity of the operation being studied. 

Equipment 

The camera for taking chronocyclegraphs should have the following 
features : — 

A focusing lens, a viewfinder which compensates for parallax, and a 
shutter capable of being re-set without winding on the film and which has 
a setting for time or brief-time (T or B) exposures. 

IN-7 2 




Figure I 

The instrument which controls the flashing pea-lamps should be 
designed so that they reach their brightest intensity quickly and then 
fade out gradually, thus giving each lamp, when moving, the appearance 
of a meteorite, with the pointed end leading. The film image of each 
lamp has a pointed end, and this always shows the direction of movement 
in a particular path; this greatly assists in the analysis of the record. 
When the frequency of the flashes is known, this provides a ready time- 
base which can be used simply by counting the streaks. 

Portable dark screens are very useful in this work as the photographic 
technique depends on the brightness contrast between the lamps on the 
operator and the general room or factory-floor lighting. In well-lit work 
places the screens may be placed around the operator to reduce the level 
of general illumination. Any alteration in the working environment (to 
ambient lighting or the fitting of lights to the operator for chronocyclo- 
graphic studies), will initially affect the operator's behaviour pattern. 
Sufficient time must be allowed for the operator to cease to be conscious 
of the difference and of the presence of the camera and any observers. It 
is also a good idea to leave the camera running for some time with no film 
in it before the actual take, to accustom the operator to any slight noise the 
equipment may make. 

Film 

Any continuous -tone negative monochrome film may be used for 
these studies but a relatively high-contrast film is frequently more useful 
than one having high sensitivity. 



IN-7 



In this technique, as in record photography, the use of colour can help 
greatly in the analysis and interpretation of results. 'Kodachrome' and 
'Ektachrome' films are excellent for this purpose when it is required to 
differentiate between the separate paths, for example, of an operator's 
two hands. Colour-negative films, such as 'Kodacolor-X' Film (see 
Data Sheet FM-4A), are also suitable. Experiments have shown that red 
and yellow pea-lamps are the best colours to use in this application, and 
there is no difficulty in distinguishing between the paths of movement on 
the subsequent colour picture. The lamps can be coloured by wrapping 
pieces of gelatine filter around them — 'Wratten' Filters No. 25 (red) and 
No. 15 (yellow) are quite suitable. 

An advantage in the use of reversal colour film is that the processed 
transparencies, as slides, can directly be projected for analysis, inter- 
pretation, or for demonstration purposes; this avoids the need for sub- 
sequently preparing positive slides, as is the case when using negative 
film. 

MICROMOTION STUDY 

Micromotion study is probably the most widely known of the tech- 
niques which Frank Gilbreth* devised at around the turn of the century. 
A cine camera is used to make a cine record of the relevant operation and 
this is studied frame-by-frame, allowing a detailed analysis to be made 
of the smallest movements of, for example, the hands. It is used when 
it is desired to analyse broad movements into their elemental constituents. 
To a lay observer, the movements employed by an operator at work may 
appear to be quite simple and necessary to the performance of the task, 
whereas, in fact, they are all complex, and many of them on analysis are 
found to be inefficient or unessential. The speed at which a skilled 
operator performs various movements may make visual observation an 
impracticable technique, and it is in such cases that this application of 
photography proves its value. 

Equipment 

Normally, 16 mm apparatus is used as there is a wider range of films 
available for this size. Double 8 mm and Super 8 equipment is also used 
and has the advantage of being very much cheaper. Whichever format is 
chosen, the equipment should be as versatile as possible. It should be 
fitted with a lens of large aperture and should accept reasonably large 
capacity spools or magazines of film (100-foot spools of 16 mm film at 
16 pictures per second give 250 seconds of recording time, other running 
times for 16 mm, Double 8 and Super 8 are given in Data Sheet AV-3). 
Cameras should be capable of operating at a range of speeds from 64 frames 
per second down to single frame pulse operation. Other features which are 
desirable, but not essential, are the fitting of motors capable of giving long 
uninterrupted runs at constant speed, the ability to use interchangeable 
lenses, and in conditions where the light level is not easily controlled auto- 
iris control is a great advantage. Camera stability is very important and 
the use of a rigid tripod or mounting is essential. 

*An account of the work of Frank Gilbreth may be found in the fourth reference in the Bibliography. 

IN-7 4 



Film 

A medium-speed fine-grain emulsion is preferred for this purpose and 
Kodak 'Plus-X' Reversal Film 7276 (see Data Sheet FM-12) is very 
suitable. It gives a very bright and well-defined image, and is capable of 
recording very fine detail. 

Analysis 

The analysis of the subsequent record is undertaken by projecting the 
film. Many types of projector can be used but only those having a 
single-frame viewing device will allow the required frame-by-frame 
analysis to be made. As an alternative, the viewer of a film editor or a 
'Recordak' Microfilm Reader can be used. 

The film should be projected several times so that the key points 
become firmly established before commencing the frame-by-frame 
examination and analysis. The basic elemental movements are then 
recorded in an analytical fashion on what is known as a Simo chart. 
From a study of this, improved methods may be devised; such a chart is 
illustrated in Figure 2. Full details on the preparation and use of these 
charts may be found in any of the books listed in the Bibliography. 

MEMOMOTION STUDY 

This work study technique records the interrelated activities of groups of 
people working together, such as queues, customer congestion, or transport 
congestion. A cine camera is set up in a suitable position to record simul- 
taneously the activities, within a given area, of all those people or objects 
concerned, and a single-frame exposure is made at intervals of 1 or more 
seconds. The actual time chosen, being dependent on the subject being 
analysed, and the factor by which the time is to be extended. For example 
using the normal 16 mm film projection speed of 16 pictures per second, 
pictures taken at 1 second intervals will give an apparent slowing of the 
motion by x 16, while pictures taken at 10 second intervals give a factor of 
X160. 

Equipment and film 

Possibly the most important requirement is that the camera should have 
a high standard of picture steadiness, as a film with "picture jump" or 
"float" can be difficult to analyse. 

Cameras which have a single-frame release can be manually operated 
using a stop watch as the time control. On lengthy operations, however, 
it would be necessary to have an automatic timing device, and this can be 
fitted to most cine cameras. 

A high-speed monochrome film may be used, such as Kodak 'Tri-X' 
Reversal Film 7278 (see Data Sheet FM-11) or one of the high-speed 
colour films, such as High Speed 'Ektachrome' (see Data Sheet FM-1B). 

Filming technique and analysis 

The procedure for this method is not quite so simple as for micromotion 
study; lighting is the main problem as workshop lighting is not usually 
sufficient and must be supplemented as necessary. Care should be taken 
when setting up the camera to ensure that the whole of the relevant 

5 IN-7 



working area can be recorded and that the people concerned do not walk 
outside the picture area. Usually a high viewpoint is required for this 
type of work; a wide-angle lens may help to include large areas at relatively 
close distances. Care is however required in the use of wide-angle lenses 
as they do give some perspective distortion, which can make subsequent 
analysis more difficult. 

SIMO CHART 
BOLT & WASHER ASSEMBLY 



OLD METHOD 



REACH TO 

BOLT 

GRASP 

MOVE TO 

FRONT 

POSITION 



MOV 
A5SE 
TO 
RELEASE 




NUMBER OF FRAMES 
PER SECOND 



REACH TO 
1st WASHER 
GRASP 



NEW METHOD 

\ LH RH 



POSITION 
WAIT 



ASSEMBLE 
30 1st WASHER 
TO BOLT 

REACH TO 
40 2nd WASHER 
GRASP 

MOVE TO BOLT 

POSITION 

ASSEMBLE 
60 REACH TO 

3rd WASHER 

GRASP 
7 MOVE TO BOLT 

POSITION 



ASSEMBLE 



Figure 2 




REACH TO 
1st WASHER 



MOVE TO 
NEST 



REACH TO 
2nd WASHER 

MOVE 

POSITION 

REACH TO 
3rd WASHER 



REACH 
TO BOLT 
GRASP 
MOVE TO 
WASHERS 
IN NEST 

WAIT-WHILE 
L.H. BOLT IS 
POSITIONED 
POSITION 
BOLT 

ASSEMBLE 
BOLT TO 
WASHERS 

REGRASP 
MOVE TO 
CHUTE 
RELEASE 



2 OFF 



The projecting of the film at normal projection speed is frequently 
all that is necessary to reveal inconsistencies in the operation or move- 
ments being studied. Further detailed analysis, if required, is done by 
means of a simplified Simo chart (see Figure 2). 

8-mm DOUBLE AND SUPER 8 FILM AS AN ALTERNATIVE 

For micromotion and memomotion study it has generally been accepted 
that 16-mm equipment and film is necessary but it has been shown that 
8-mm equipment and film can be used very successfully for many types of 
work. It is, of course, considerably cheaper both in the buying of the 
original equipment and in the operating costs. With 'Kodachrome' II 



1N-7 



Film, the 8-mm gauge can be used with confidence even for quite de- 
tailed studies; very large scale magnifications can be produced with no 
perceptible loss of detail. 

BIBLIOGRAPHY 

M. Delfosse, The Film Applied to Work Study, Science and Film, 2, 

No. 3, Sept. 1953, pp. 21-27. 
M. Delfosse, Methods of Work Study, Including the Film, in Repetitive 

Industrial Tasks, Science and Film, 4, Mar. 1955, pp. 19-32. 
J. W. Hendry, Manual of Time and Motion Study, Pitman, 5th edition, 

1957. 
A. G. Shaw, The Purpose and Practice of Motion Study, Columbine Press, 

2nd edition, 1960. 
M. E. Mundel, Motion and Time Study : Principles and Practice, Prentice 

Hall, 3rd edition, 1960. 
H. Pierce, How to Use Photography in Work Study, Kodak, 1963. 
R. M. Barnes, Motion and Time Study, Wiley, 5th edition, 1963. 



IN-7 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

WRATTEN 



Kodak Data Sheet KODAK LIMITED LONDON 

IN-7 

PDIN-7/xWP 1 1/7-71 



RECORDING TEMPERATURE DISTRIBUTION 



DIRECT RECORDING 

If an object reflecting or emitting light is photographed on a pan- 
chromatic film, the negative is a record of the distribution of brightness 
over the surface. If suitable precautions are taken, the actual brightness at 
different points on the surface of the object can be determined quantita- 
tively. Similarly, if the infra-red radiation emitted by hot objects is 
recorded on an infra-red sensitive film or plate, some idea of the distribu- 
tion of infra-red emissivity, which is related to the temperature of the 
surface, may be obtained. 

Infra-red photography is applicable to the study of the distribution of 
the temperature of surfaces from about 350°C to the temperature at which 
visible radiation is emitted, approximately 550°C. Above this latter 
temperature it is simpler to use ordinary panchromatic films, and below 
about 350°C the exposure times are too long. 

In order to be able to interpret infra-red exposures of hot bodies 
quantitatively, it is necessary to employ the precautions used in photo- 
graphic photometry. The most important of these is to include on the 
negative a series of exposures to a standard hot body maintained at known 
temperatures. This can be done by photographing a small heated metallic 
object, the temperature of which can be measured by physical means, or a 
triangular piece of metal foil through which an electric current is passed. 
Such a foil will vary in temperature according to its width and can be 
calibrated with a pyrometer or thermocouple. 

The temperature range which can conveniently be covered by any one 
exposure is about 60-120°C, the actual position of this range on the 
temperature scale determining the exposure required. If the temperature 
variations over the surface of the body are greater than 120°C then the 
density range on the film or plate will not be so easily translatable into 
accurate temperature measurements. When the record is confined to a 
range of 60°C or less, temperature differences of 15°C are easily 
recorded. 



Recommended sensitized materials 

High Speed Infrared Film* (meter settings in Data Sheet SC-7), for 
minimum exposure. 

Infrared Film (35 mm) (Data Sheet SC-7), for better differentiation of 
moderate temperature differences. 

Spectroscopic Plate Type I Classes N and Z (Data Booklet SE-3), for 
sharp differentiation of small temperature differences. 

'Panchro-Royal' Sheet Film ('Estar' Base) (Data Sheet FM-38), for 
temperatures above about 550°C. 

^Available to special order only. 

Issue B Kodak Data Sheet 

IN-8 



Exposures obviously depend on the surface temperature and must be 
determined by experiment in any particular case, but the following data 
will act as a guide. The upper curve is for 'Panchro Royal' film, the 
lower for Infrared Film. This should only be used as an initial guide, 
for maldng the first test exposures under actual operating conditions. 



800 
750 
700 
650 

600 i 



1050 










- 












- 


950 










- 










- 












- 






\^ 






- 












- 


700 










- 








\^ 


- 


600 













10 100 1000 10000 

Time of exposure (seconds) at f/4.5 

Recommended filters 

'Wratten' Filter No. 29— transmitting from 600 nm (Data Sheet FT-6) 
„ „ „ 70 „ „ 650 nm 

„ „ „ 88A „ „ 720 nm \ (Data Sheet 

» „ 87 » » 740 nm J* FT-9) 

INDIRECT RECORDING 

There are several paint-like preparations, available commercially, 
which will change colour when heated to a specific temperature. These 
colour changes are normally irreversible, and individual preparations may 
exhibit as many as four different changes at successive temperatures. 
By applying one of these substances to a hot body it is possible to produce 
on its surfaces a visible representation of the temperature distribution; 
this may be photographed in colour or monochrome if a record is required. 

INFRA-RED SCANNING CAMERAS 

The use of infra-red scanning equipment is probably the most versatile 
method of recording temperature distribution. The system normally 
consists of a camera unit (scanner), control and a CRT display unit. The 
scene is scanned vertically and horizontally by a reflecting optical system. 
The infra-red radiation of the object is focused on to a detector (usually 
liquid nitrogen cooled indium-antimonide). After amplification the signal 
from the detector is connected to the intensity grid of a cathode ray tube, 



IN-8 



the beam displacement of which is synchronized with the scanning 
motion. The image on the CRT is then either assessed visually or is 
recorded on conventional photographic materials using an oscilloscope 
camera. The thermal resolution depends on the temperature range 
selected but on some commercial units, variations as slow as 0.1 to 0.2°C 
can be distinguished at 30°C. 

At the present time most commercial units have a scan time of J second; 
when using a camera to record the CRT display an exposure equal to 
the scan time or to multiples thereof should be used to avoid recording 
partial scans. 

APPLICATIONS 

These techniques have been applied to tracing heat losses in furnaces 
due to weaknesses in the insulation, hot metal ingots, cylinder head and 
exhaust manifolds of internal combustion engines, temperatures of 
furnace walls, metallic welding operations and distribution of surface 
temperature in many kinds of electrical heating appliances and radio valves. 
Infra-red photographs of superheated steam lines, showing the loss of heat 
in non-insulated parts, have been used effectively in the advertisements 
of manufacturers of insulating materials. 

BIBLIOGRAPHY 

W. Clark, Photography by Infrared, Chapman and Hall, 2nd edition, 
1946, pp. 325-327. 

L. Beral, Photographic Techniques in Combustion Research, Photogr.J., 
89B, 1949, pp. 98-107. 

H. J. Merrill (editor), Light and Heat Sensing, AGARDograph 71, 
Pergamon, 1963, Chapter 12, The Study of Time and Space Variable 
Surface Temperatures of Self-luminous Bodies and other Brightness 
Parameters by Colour Densitometry by I. Overington, pp. 151-181. 

D. R. Howard, A Photographic Technique for the Measurement of Transient 
High Temperatures, Engineer, 215, 15 Mar. 1963, pp. 474-475. 

H. E. Whipple (editor), Thermography and its Clinical Applications, Ann. 
New York Acad. Sci., 121, 1964, pp. 1-304. 

W. O. Hamlin, Infrared Temperature Measurements, Electronics World, 
1968, pp. 34-36. 

Applied Infrared Photography (Eastman Kodak Technical Publication 

M-28), Kodak, 1968. 
I. Overington, Photographic Detectors IV, Photography Pyrometry, 

J. Photogr. Sci., 16, No. 5, Sept./Oct. 1968, pp. 199-205. 



IN-8 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

W RATTEN 

PANCHRO-ROYAL 



Kodak Data Sheet KODAK LIMITED LONDON 

IN-8 

PDIN-8/xWPI 1/8-71 



PHOTOGRAPHY OF THE 
MACROSTRUCTURE OF METALS 



The macrostructure of a metal refers to those features of its surface which 
are seen by the unaided eye in colour or relief, usually after rough polishing 
and etching, and which are related to the history of the specimen, such as 
the fusion zone in a weld, or the crystallization of an ingot. 

The recording of these superficial features by photography demands 
skill in the use of both oblique and vertical illumination and in the choice 
of the appropriate filter to exaggerate small but significant colour 
differences over the area to be photographed (see Data Sheets FT-1 
and FT-3). 

Apparatus 

A camera taking 4x5 inch sheet film, and with double extension 
bellows and a full range of movements, will be the most useful. Certain 
types of photomicrographic equipment can also be used for the making 
of photomacrographs 

The lens focal lengths given on the following page are recommended 
by the American Society for Testing and Materials as giving maximum 
resolution at various magnifications. 




Cross section of high-speed steel drill showing carbide segregation at centre. 
Courtesy of Ford Motor Co. Ltd. 



Issue C 



Kodak Data Sheet 
IN-IO 



LINEAR MAGNIFICATION 


APPROXIMATE FOCAL LENGTH OF 


REQUIRED 


LENS 


1— 3 


6 in 


3—10 


72 mm 


10—20 


40 mm 


20—30 


32 mm 



Lenses of these focal lengths are not all readily available in the United 
Kingdom but it should be realized that some considerable deviation from 
the A.S.T.M. recommendations can be made without seriously impairing 
the quality of the results obtained. 

Illumination 

Photoflood lamps, spotlights, microscope lamps, or ring flash, form 
convenient light sources for macrographic work. The methods of illumin- 
ation usually employed are similar to those familiar, on a smaller scale, in 
micrography (see Data Sheet IN-11). 

Vertical illumination is obtained by inserting a sheet of plane glass 
between the lens and the surface of the specimen, at 45° to the axis of the 
lens : it is possible to do this because of the greater distance between the 
lens and the specimen than is obtained in micrographic work. 

A condenser lens of large diameter is placed as close as possible to the 
plane glass reflector. It should be of such a focal length that an image of 
the light-source will be projected into the aperture of the photographic lens ; 
the light passes from condenser to photographic lens by reflection at the 
plane glass reflector and again at the surface of the specimen. Further 
information will be found in the book by Bergner, Gelbke, and Mehliss, 
listed in the bibliography. 

Oblique illumination is obtained by directing a substantially parallel 
beam of light on to the subject from one side. The degree of inclination 
between the light beam and the normal to the specimen should be adjusted 
according to the nature of the surface of the specimen. A specimen with 
a relatively smooth surface demands a much larger angle of incidence than 
would one with a rough surface. 

Oblique illumination from two sides is frequently used if the surface of 
the specimen is a fracture or has some other form of very irregular surface. 
Two light-sources of different intensities are used, one on each side, the 
weaker source serving to lighten the deep shadows cast by the projections 
on the surface. 

Shadows can be eliminated by moving the light-source round the speci- 
men by hand during the entire time of exposure. 

Where light reflections from the surface prove objectionable they can 
often be eliminated by the use of a 'Pola'-screen in front of the lens, the 
screen being rotated until the best result is obtained on the focusing screen 
of the camera (See Data Sheet FT-1 1). In some cases it may be necessary 
to use a second 'Pola'-screen between the light-source and the specimen. 

IN-IO 2 



Exposure 

It is difficult to standardize exposures since every specimen presents its 
own lighting and filtering problem and, although a photo-electric exposure 
meter is useful, trial exposures are normally the easiest route to the 
optimum result when a new type of specimen is to be examined. A series 
of trial exposures can be made on one sheet of film by first withdrawing 
the sheath completely, and then replacing it an inch or so at a time, so 
arranging that each step receives twice the exposure of the one before. 
For example, if the whole sheet of film is first exposed for 5 seconds, then 
the sheath is inserted 1 inch at a time in successive steps of 5, 10, 20 
seconds, etc., the resulting series of exposures is 5, 10, 20, 40 seconds, etc. 

Exposure meters are available which enable accurate exposure 
measurements to be made in the image plane. 

Recommended materials 

For most macrographic work, Commercial Ortho Sheet Film 4180 
(Data Sheet FM-34) and 'Tri-X' Ortho Sheet Film 4163 (Data Sheet 
FM-35) are suitable. Where the specimens are coloured (e.g., brass, 
copper), 'Plus-X' Pan Professional Sheet Film 4147 (Data Sheet FM-36) is 
recommended. White, smooth, glossy bromide paper (Data Sheet PP-9) 
is most suitable for printing or enlarging from the negatives. 

When results are required to be recorded in colour, either reversal or 
negative colour materials may be used; the latter type has an advantage in 
that colour prints, suitable for illustrating reports, etc., can more easily be 
obtained. See Data Sheets FM-1B, ID, IE, 2A, and 2B for details of rever- 
sal colour films, and Data Sheets FM-3 and FM-4A for negative materials. 

Filters are usually required to emphasize small colour differences. The 
most suitable one for any given purpose is best found by experiment. 
The range available, together with full transmission and other data, is 
given in the book "Kodak Wratten Filters", obtainable from Kodak 
Limited. See also Data Sheets FT-1, FT-3, and FT-8. 



IN-10 



Bibliography 

C. H. Desch, Metallography, Longman, 4th edition, 1939. 

Luck, Rogers, and Cattaneo, New Methods for the Valuation and Recording 

of Piston-skirt Deposits, Soc. Auto. Eng. J. (Trans.), 51, February, 1943, 

pp. 38-44, 63. 
Kehl, Principles of Metallographic Laboratory Practice, McGraw-Hill 

(New York), 1949. 
J. H. Hammond, Macro-Photography and a Field Macro Camera, Brit. J. 

Phot., 101, No. 4930, 12 Nov. 1954, pp. 574-575. 
R. H. Greaves and H. Wrighton, Practical Microscopical Metallography, 

Chapman and Hall, 4th edition, 1960. 
Standard Methods of Preparation of Micrographs of Metals and Alloys, 

A.S.T.M. Designation E2-62, American Society for Testing and 

Materials, 1962. 
J. Bergner, E. Gelbke, W. Mehliss, Practical Photomicrography, Focal 

Press, 1966. 
C. J. Smithells (editor), Metals Reference Book, Vol. 1, Butterworths, 

4th edition, 1967. 
J. Morgan, Texture Lighting by Electronic Ring Flash, Brit. J. Phot., 

1 16, No. 5677, 9 May 1969, pp. 450-451. 



Kodak, Plus-X, Pola, Tri-X and Wratten 
are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

IN-10 

PDIN-IO/xWPIO/IO-69 



METALLOGRAPHY 



Certain properties of metals and alloys are influenced by their micro- 
structure. It is not surprising therefore that with the growth of metal- 
lurgy as a science, increasing attention has been paid both to improving 
the methods of recording the microstructure of a specimen, and to 
improving the quality of that record. 

Photomicrography is the method most widely used in metallurgy for 
recording microstructure, whereas electron microscopy is increasingly 
used for examining and recording the ultra-fine structure of specimens. 

The general quality of published photomicrographs has risen con- 
siderably in recent years. This improvement does not arise from notable 
advances in microscopy itself, but rather from a better appreciation of 
what constitutes a correctly prepared metal surface combined with good 
photographic technique. Hence, any discussion on metallography must 
include a consideration of modern methods of preparing metal surfaces. 

Specimen preparation techniques 

Small or awkwardly shaped specimens can be handled more easily 
during preparation if they are embedded in a suitable material. The 
simplest technique for mounting specimens is a mechanical clamp made 
of similar material to the specimen, and designed so that the clamp jaws 
and specimen surface can be prepared together. Other well-known 
methods include the use of thermo-plastic or thermo-setting synthetic 
resins in a metallurgical mounting press. These materials invariably 
require heating to a temperature in excess of 100°C (212°F), and in some 
cases this can alter the specimen features. In such cases commercially 
available polyester or epoxy resins may be successfully used. These 
resins set hard at low temperatures, and although an exothermic reaction 
heats the specimen very slightly during setting, it is not usually sufficient 
to cause any structural changes. 

It is occasionally necessary to preserve the edge of the specimen to allow 
detailed examination of features such as fracture characteristics, surface 
scale, and corrosion products. Here it is often an advantage to use 
additional techniques such as the electro-plating of a metal on to the edges 
to be preserved. When examining scale or corrosion products which 
tend to be friable and porous, it is often necessary to impregnate the 
surface with resin under vacuum prior to mounting. 

After mounting, the specimen surface is ground or filed, and then 
polished to reach the desired mirror finish. This finish must be free 
from surface deformation, and hence it is essential that the techniques 
used must remove material by a cutting rather than a buffing action. 

Issue C Kodak Data Sheet 

IN-II 



The conventional method of achieving a mirror finish can be divided 
into two stages. In the first stage the specimen is ground, preferably on 
waterproof abrasive papers over which a stream of water is allowed to 
flow. This gives a very rapid grinding action because the papers are kept 
tree from grindings, which would otherwise clog the papers and tend to 
cause a rubbing rather than a cutting action. The water also reduces the 
effect of the high temperatures generated during abrasion. 

The grinding is carried out through a series of progressively finer 
grades of abrasive papers, finishing on a 600 grit size. On changing 
from one grade to the next, the specimen should be rotated so that the 
fresh scratches run at right angles to the previous ones. This assists the 
operator in deciding when the deformation caused by the previous paper 
has been completely removed. 

After the application of the final abrasive paper, the associated deforma- 
tion is removed in the second stage by mechanical polishing. This is 
usually done on a lap or rotating wheel covered with a suitable cloth 
impregnated with an abrasive. Samuels 1 has shown that to remove 
deformation produced during the abrasion stage the first polishing opera- 
tion should have a high polishing rate. This implies that it is necessary 
to have at least two stages of final polishing to obtain a good surface 
finish. 

In recent years diamond abrasives have become the most widely used 
polishing media, although chromic oxide, alumina, and calcined magnesia 
are also used. 

Having obtained the required mirror finish, the microstructure of the 
specimen is revealed by swabbing with, or immersing in, a suitable solu- 
tion. Numerous etching solutions have been developed to reveal the 
differences between metallic phases in alloys. In general, etchants either 
attack the grain boundaries or interfaces between constituents, or stain 
the various constituents present. The exact choice of etchant depends 
upon its chemical relationship with the metal or alloy. 

Alternatively, this polishing may be carried out electrolytically. The 
specimen is made the anode in a suitable electrolyte and is polished 
by dissolution of the metal surface when current is passed through the 
cell. The choice of method used depends on a number of factors. 1 
Electrolytic polishing is, however, extensively used for polishing very 
soft metals. Electrolytic etching may be carried out in the same bath, 
but with a lower voltage and current. 

Recording the specimen 

As metals are opaque, the finished specimen is examined by reflected 
light. If much metallographic work is to be done, the most satisfactory 
solution to the equipment problem is the acquisition of one of the pieces of 
specially designed metallographic equipment which are available on the 
market. The microscope is often of the inverted type (see opposite) and, 
although this type of apparatus is designed for examining opaque speci- 
mens by reflected light, there is generally some arrangement for examining 

IN-ll , 



transparent specimens by transmitted light. The camera for recording the 
image is an integral part of the apparatus. This equipment, however, is 
expensive and when only a small amount of work is to be carried out, an 
ordinary microscope, with suitable illumination attachments which are 
available commercially, together with almost any type of standard camera, 
may be used satisfactorily. This type if arrangement is obviously not as 
convenient as the specially designed metallographic equipment. 

The American Society for Testing and Materials recommends 2 that all 
photomicrographs of metals and alloys be made and reproduced in papers 
and journals at one of the following standard magnifications : x 1, X 5, 
X25, x50, x75, xlOO, x 150, x200, x250, x500, x750, x 1000, 
X1500, X2000. 



CONDENSER 
LENS \ 



LIGHT- 



SOURCE 



^^ SAMPLE 

OBJECTIVE 

i 
FIELD IRIS i 

1 
^KGLASS SLIP 

COLLIMATING 
LENS 



LAMP IRIS 




EYEPIECE OR 
ZOOM LENS 



MIRROR 

Typical layout of a projection microscope 




Lenses 

The lenses recommended by them for maximum resolution at various 
magnifications are as follows : 

(Magnification up to 30 diameters is best obtained in the camera without 
the use of a microscope; the techniques involved are similar to those 
employed in photomacrography, see Data Sheet SC-11.) 



IN-II 



LINEAR 
MAGNIFICA- 
TION 



TYPE OF 
LENS 



25 

50 

75 

100 

150 

200 

250 

500 
750 



1000 

1500 
2000 



Achromatic 



Achromatic or 
Apochromatic 



Apochromatic 
preferred 



FOCAL 

LENGTH OF 

OBJECTIVE 

(APPROX) 



32 or 48 mm 

32 mm 

25 mm 

16 or 25 mm 

16 mm 

8 or 10 mm 

8 mm 

4 or 6 mm 
4 mm or oil 
immersion 

oil immersion 



OCULAR 



Huygens x5 

x5, x6, or x7.5 

X5 

x5 or x7.5 

X7.5 

x5 or x7.5 

Compensating x5or x7.5 



x7.5 

X7.5 or x 10 






High-power non-immersion lenses should be specially corrected for use without a cover glass. 

Illumination 

Vertical illumination may be secured by introducing a plane glass disc, 
at an angle of 45° to the microscope axis, in the microscope body tube 
immediately behind the objective (see diagram on page 3). When the 
objective is of long working distance, the plane glass reflector can with 
advantage be placed between the objective and the object. 

This type of illumination is suitable for the examination and photo- 
graphy of all polished metal specimens, and all specimens should be 
examined first in vertical illumination. A valuable asset is the ability to 
control the angular extent of the cone of illumination; by this means low 
contrast detail that would otherwise be lost can often be brought out. On 
the other hand, too serious a reduction of the angular extent of the cone 
of illumination may bury fine detail and cause apparent thickening of the 
detail still evident. 

Etched specimens, especially those which are very dark, may appear 
veiled when examined in vertical illumination; examination by oblique 
illumination, polarized light, or dark-field illumination may bring out 
details obscured by these conditions. 

Oblique illumination can be secured by de-centring the diaphragms 
normally used for controlling the angular extent of the cone of illumination. 

An alternative technique, not recommended when the objective has a 
focal length less than 8 mm, is that of introducing between the objective 
and eyepiece, near the objective, a totally reflecting prism or a mirror 
which covers up half the aperture of the objective. Although such a 
reflector will greatly increase the brightness of the specimen, the resolving 



IN-II 



power of the objective will not be as great as with the plane glass reflector 
used for vertical illumination. This will result in a loss of fine detail on 
the specimen. 

Polarized lighting can be used with either vertical or oblique illumination 
by introducing a polarizing device between the light source and the reflect- 
ing device used and an analysing device between the objective and the eye. 
Nicol prisms are usually employed in microscopy although Tola' screens 
(Data Sheet FT-11) are suitable for low-magnification work. 

The polarizing device should be rotated without using the analyser until 
observation shows the specimen to be at its brightest; this means that the 
plane of vibration of the polarized light will be perpendicular to its plane 
of incidence on the reflector. The analyser is then placed in the optical 
system, between the object and the eye, and rotated until its plane of 
polarization is perpendicular to that of the first polarizer. All specular 
reflection, i.e., surface glare from the specimen, will thus be suppressed. 
The use of polarized light in this way will usually also make the actual 
grains visible in cases where there exists a change in orientation from grain 
to grain; inclusions will be easily classifiable as to their possible nature. 

Dark-field illumination may be secured with a microscope objective by 
surrounding it with a beam of light concentrated on the specimen in such 
a manner that no light can be specularly reflected from the specimen and 
enter the objective; special apparatus for this purpose has been made 
commercially available. 

In an examination by dark-field illumination, highly reflecting surfaces 
are not visible, yet the smallest pits or the thinnest lines stand out as bright 
spots or lines. 

Filters 

Filters are used in photomicrography for several purposes : 

1 To control the contrast of coloured objects or to enable greater detail to be 
seen. This technique, which is of greatest importance in biological photo- 
micrography, is usually only applicable in metallography where objects 
such as copper or rusty iron have to be photographed; here a red filter will 
give more detail. The general rule is to use a filter of complementary 
colour if maximum contrast of the coloured object against the background 
is required, and one of like colour if the maximum detail in the object is 
wanted. 

2 To convert the quality of the light to that required for correct tone rendering 
by the photographic material. The filter required for this purpose will 
depend both on the quality of the illuminant and on the spectral sensitivity 
of the photographic material. 

For black-and-white pictures when tungsten illumination is employed, 
a 'Wratten' Filter No. 11 (XI) should be used with a panchromatic 
material. 

For colour transparencies, any reversal colour film may be used, but 
'Kodachrome' II Professional Film, Type A (Data Sheet FM-2A) is very 

5 IN-II 



suitable as this film is balanced for use with Photoflood lamps, and may 
also be used without a filter with projection lamps; for other suitable 
sources Colour-Compensating filters are required (Data Sheet CL-3). 
Such filters can only be recommended for light-sources having a continuous 
spectrum, as it is not possible to make satisfactory colour pictures with 
illumination from a non-continuous source such as a mercury-vapour lamp 
nor with a mixture of two sources of different quality such as tungsten and 
arc-light. Recording in colour frequently assists interpretation of the 
photographic record; for instance, the dezincification of brass is graphically 
revealed when recorded in colour. 

3 To restrict the illuminant to that portion of the spectrum with which the 
objective gives the best results. Since metallographic specimens are 
frequently uncoloured, this becomes the most common use for filters. 
Achromatic microscope objectives are corrected under the assumption that 
only a narrow band of the spectrum is to be used; they are usually designed 
so that an image formed by yellow-green light has the minimum optical 
defects. This condition can be secured by the use of a 'Wratten' Filter 
No. 15 (G) with an orthochromatic material, such as 'Kodak' Commercial 
Ortho Film ('Estar' Thick Base), or a panchromatic material used with a 
'Wratten' Filter No. 58. 

With apochromatic objectives, there is an aberration minimum in the 
blue as well as in the yellow-green; advantage may be taken of the fact that 
the resolving power of a microscope is greater as the wavelength of the 
illumination used decreases, and a blue filter, such as the 'Wratten' Filter 
No. 47B may be employed, unless materials sensitive only to blue are used. 

Photographic materials 

Choice of the type of film or plate is chiefly determined by the colour of 
the illumination in use; sensitivity to other colours merely limits the 
allowable illumination in the darkroom. As explained above, many 
microscope objectives are most fully corrected for yellow-green light and 
consequently orthochromatic materials are generally used in metallographic 
work. A suitable material is Commercial Ortho Film, which has a high 
green and yellow sensitivity. Little speed is therefore lost when working 
with a green filter or with an orange filter such as the 'Wratten' Filter No. 
15 (G). When using apochromatic objectives for highest resolving power, 
a blue-sensitive material such as the 'Kodak' B.10 Plate (Data Sheet 
PL-2) or 'Kodak' Process Sheet Film (Data Sheet FM-33) should be used. 

The following sheet films are suitable: 'Kodalith' Ortho Film, Type 3 
(Data Sheet FM-30) or Kodalith 'Royal' Ortho Film (Data Sheet FM- 
42A) developed, with continuous agitation, for approximately 2 minutes in 
'Kodak' Soft-Gradation Developer, or in a developer made up according to 
Kodak formula D-165, diluted one part to three parts of water at a tem- 
perature of 20°C (68°F). A comparable panchromatic material, which 

IN-II 6 



should be processed similarly, is 'Kodalith' Pan Film (Data Sheet FM- 
30A); Kodak 'Plus-X' Pan Sheet Film (Data Sheet FM-36) is also 
suitable, but the maximum contrast will not be as high as is obtainable 
with the 'Kodalith' films. 

Judging exposure 

The best results can only be obtained from a correctly exposed plate or 
film. A number of modern projection microscopes have automatic 
exposure devices incorporated and will therefore give correctly exposed 
negatives. Where such devices are not fitted the metallographer has 
to judge the correct exposure. 

The variables influencing the exposure are the light-source, lens 
apertures, camera extension, light filters, objective and ocular powers, 
the reflectivity of the specimen surface, and the speed of the photographic 
material. It is convenient to draw up an exposure chart for each individual 
apparatus in which the actual exposure under varying conditions is deter- 
mined by exposing a film or plate in steps by withdrawing the dark-slide 
sheath completely and then replacing it an inch or so each time, so 
arranging the exposures that each step receives twice the exposure of the 
one before. For example, if the whole film or plate is first exposed for 
5 seconds, then the sheath is inserted 1 inch at a time in successive steps 
of 5, 10, 20 seconds, etc., respectively, the resulting series of exposures 
is 5, 10, 20, 40 seconds, etc. 

Further information may be found in Data Sheet SC-13. 

Processing 

Apart from the 'Kodalith' films, for which development recommenda- 
tions are given above, the remaining materials should be processed, for a 
high contrast, in accordance with the recommendations given in their 
respective Data Sheets. 

Development times given are intended only as a guide; variations may 
be found necessary to get the best results from particular specimens. 

Use of ultra-violet 

The use of ultra-violet in place of visual light as an illuminant yields 
increased resolution in the photograph and so permits crisp, brilliant 
images of metallurgical specimens to be obtained at magnifications as high 
as 5000 to 6000 diameters. 3 B.10 plates (Data Sheet PL-2) are recom- 
mended for this purpose. (See Data Sheet SC-4 on Ultra- Violet Photo- 
micrography.) 

References 

1 L. E. Samuels, A Critical Comparison between Mechanical and Electro- 
lytic Methods of Metallographic Polishing, Metallurgia, LXVI, No. 396, 
Oct. 1962, p. 187. 

2 Standard Methods of Preparation of Micrographs of Metals and 
Alloys, A.S.T.M. Designation E2-62, American Society for Testing 
and Materials, 1962. 

3 J. Smiles and H. Wrighton, The Micrography of Metals in Ultra-Violet 
Light, Proc. R. Soc. A., 158, 1937, pp. 671-681. 

7 IN-II 



Bibliography 

C. P. Shillaber, Photomicrography in Theory and Practice, Wiley, 1944. 

R. P. Loveland, Metallography in Colour, Metal Industry, 10, 17, and 
24 Aug. 1945, pp. 82-85, 87, 98-100, 119-120. 

R. H. Greaves and H. Wrighton, Practical Microscopical Metallography, 
Chapman and Hall, 4th edition, 1960. 

D. F. Lawson, The Technique of Photomicrography, George Newnes, 1960. 

J. Bergner, E. Gelbke and W. Mehliss, Practical Photomicrography, 
Focal Press, 1966. 

Photomicrography of Metals (Eastman Kodak Technical Publication P-39), 
Kodak, 1966. 

C. J. Smithells (editor), Metals Reference Book, Volume 1, Butterworths, 
4th edition, 1967. 



Kodak, Kodalith, and product names quoted thus — ' Wratten' — are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

IN-II 

PDIN-II/xWPIO/IO-69 



CONTACT MICRORADIOGRAPHY 



Contact microradiography or X-ray micrography provides radiographs 
showing the gross structure of a thin section of material, and is to some 
extent complementary to photomicrography. The principle of the 
technique was reported by Goby 1 as early as 1913, but the method was 
not developed for many years owing mainly to the absence of suitable 
photographic materials which would permit the image magnification 
necessary. 

x-rays 



lead — 
plate i t^W?^ — specimen 

Basically the technique is simple. The specimen, generally in the form 
of a thin slice less than 1 mm thick, is placed in contact with the photo- 
graphic emulsion and a radiograph is made, usually with long wave-length 
X-rays. Subsequent to processing, the radiograph is examined under a 
microscope, or projected, or printed as an enlarged image on to bromide 
paper. The magnification, at times, may be greater than x 200. 

The major difficulty lies in the preparation of the specimen section, 
which needs considerable care. Full details will be found in the various 
original papers listed below and overleaf. 

The photographic material must clearly permit the very high image 
magnifications necessary to reveal the finer points of the image. Origin- 
ally, Lippmann-type emulsions were utilised, but these have been replaced 
by ultra-fine-grain, high-contrast, materials, such as the H-R 'Kodak' 
High Resolution Plate (Data Sheet SE-3). 

The choice of the quality of X-radiation depends on the nature of the 
specimen and the relative X-ray absorption of its various component parts. 
Where these differ appreciably in absorption, low-kilovoltage radiations 
may be used: for example, Clark 2 has reported the use of 5 kV X-rays 
for copper-aluminium alloys. Alternatively, the use of characteristic 
X-rays enhances contrast and often permits the identification of elements 
and alloys in the specimen. Betteridge 3 , for instance, has reported the 
use of characteristic X-rays for the identification of inclusions in steels. 

References 

1 P. Goby, Compt. Rend., 156, 686, 1913. 

2 G. L. Clark, X-ray Photomicrography, Photo Technique, I, Dec. 
1939, pp. 19-20. 

3 W. Betteridge and R. S. Sharpe, The Study of Segregations and 
Inclusions in Steel by Microradiography, J. Iron and Steel Inst., 158, 
Feb. 1948, pp. 185-191. 

Issue B Kodak Data Sheet 

IN-12 



Bibliography 

F. W. Von Batchelder, Microradiography, Iron Age, 160, 11 Dec. 1947, 
pp. 94-97. 

J. J. Trillat, Electronic Radiography and Microradiography, J. App. 
Physics, 19, Sept. 1948, pp. 844-852. 

S. Goldspiel and F. Bernstein, Some Industrial Applications of Micro- 
radiography, Non-Dest. Testing, 1 1, No. 5, 1953, pp. 15-20. 

G. A. G. Mitchell, An Evaluation of Microradiography in Biology, J. 
Photogr. Sci., 2, No. 4, July/ Aug. 1954, pp. 113-118. 

R. V. Ely, Instrumentation in Microradiography, J. Photogr. Sci., 2, No. 4, 
July/Aug. 1954, pp. 119-124. 

V. E. Cosslett, Microscopy with X-rays, J. Photogr. Sci., 2, No. 4, July/ 
Aug. 1954, pp. 125-130. 

V. E. Cosslett (editor), X-ray Microscopy and Microradiography {Proceed- 
ings of a Symposium held at Cambridge 1956) Academic Press, 1957. 

B. Combee and A. Recourt, A Simple Apparatus for Contact Microradio- 
graphy, Philips Technical Review, 19, No. 7-8, 10 Feb. 1958, pp. 221- 
233. 

N. M. Blackett, The Resolution Obtainable with a Commercially Available 
Microradiographic Unit, Brit. J. Radiol., 31, July 1958, pp. 368-371. 

V. E. Cosslett and W. C. Nixon, X-ray Microscopy, Cambridge University 
Press, 1960. 

V. E. Cosslett, X-ray Microscopy — Retrospect and Prospect, Brit. J. Radiol., 
XXXIV, No. 397, Jan. 1961, pp. 1-20. 



Kodak is a trade mark 



Kodak Data Sheet KODAK LIMITED LONDON 

IN-12 

PDIN-l2/xWPII/l-7l 



THE RADIOGRAPHY OF LIGHT ALLOYS 



The inherent advantages of light alloys in general engineering and in 
aircraft construction are well established. The relative transparency of 
light-alloy welds and castings to X-rays offers further advantages because 
they can be readily examined for internal soundness. In practice, this 
means that lower safety factors can be applied to stressed regions with 
confidence, permitting an additional weight saving over that inherent in 
the alloys. 

The value of radiography for the inspection of light-alloy castings is 
illustrated by the insistence of the Aeronautical Quality Assurance 
Directorate on the X-ray inspection of the stressed portions of all important 
aircraft castings. In addition, the growing use of radiography for the 
routine inspection, at frequent intervals, of both military and civil aircraft 
demonstrates the quality, speed, simplicity, and economy of the radio- 
graphic method of examination. 

The radiographic inspection of light alloys is a specialized technique, 
differing in important aspects from the examination of ferrous and other 
heavy-metal castings and welds. In particular, considerable care is neces- 
sary in the choice of the X-ray equipment, of the X-ray films, and of the 
radiographic technique to provide the ideal conditions for the detection of 
the defects characteristic of light alloys. 

Both high contrast and fine detail are essential features of the X-ray 
image of light alloys, because their characteristic defects are frequently 
typified by fine details, which are essential to the correct interpretation of 
the image, but which produce only small differences in the X-ray beam 
intensity. 

Apparatus factors 

Because image contrast falls off as kilovoltage increases, it is usual to 
make a radiograph with the lowest kilovoltage X-ray beam capable of 
penetrating the specimen and of producing a radiograph in an economic 
time. A point of some importance is that the inherent filtration of the 
X-ray beam by the X-ray tube window must be as small as possible. 
High inherent filtration tends to absorb more of the longer wave-length 
component of the radiation when the X-ray tube is run at its lower kilo- 
voltage settings; this produces lower image-contrast than might be ex- 
pected for a given kilovoltage. Generally, the higher the maximum 
kilovoltage rating of the tube, the greater is the inherent nitration. For 
this reason, and since light alloys are readily penetrated by low-kilovoltage 
radiation, 140-150 kV tubes are generally used for light-alloy radio- 
graphy; gamma-rays are generally considered unsuitable. 

A further merit of equipment in the medium to low kV range is the 
relatively small effective focal spot, which minimizes the effect of 
penumbral unsharpness on the image. Tubes, with outputs varying from 
3 to 5 mA, usually have effective focal spots ranging from 0.5 (or even less) 
to 2.5 mm square, and are particularly suitable for detecting fine defects, 

Issue E Kodak Data Sheet 

IN-14 



e.g., microporosity. Usually the greater the maximum tube current, the 
larger the focal spot, so that tubes of low milliamperage output are usually 
the most effective where fine image definition is required. An exception 
occurs in low kV tubes, fitted with a beryllium window, and operating 
between 5 and 50 kV. These can often have an output of up to 30 mA; 
such equipment yields high quality results for thin specimens and welds in 
thin plate. Such tubes also have small focal spots. The effect of the focal- 
spot size on definition can, of course, be reduced by adjusting the focus- 
film distance to give an acceptably small geometric penumbra (see Data 
Sheet XR-2, "Penumbral Unsharpness"). A generally accepted value 
for the maximum width of the penumbra is 0.25 mm (0.010 inch) when 
the radiographs are to be viewed with the unaided eye from a distance of 
about 25 cm (10 inches). When examination for extremely small defects 
is called for, it is desirable to work to a smaller value, i.e., 0.13 mm (0.005 
inch), to allow for inspection of the image using a magnifier. However, 
focus-film distances greater than about 1.5 metres (5 feet) are seldom 
used as the increase in exposure time, varying with the square of the 
distance, becomes unpractical. Practical recommendations relevant to 
welds are given in references 1 and 2; most of these recommendations also 
provide a useful guide to the radiography of light-alloy castings. 

Photographic factors 

For optimum definition and sensitivity of fault detection, fine-grain 
direct-type films should be used for the radiography of light alloys. 
Kodak Tndustrex' C Film (Data Sheet FM-28) is ideal for most light- 
alloy radiography as it is capable of producing fine-grain, high-contrast 
radiographs, and is at the same time fast enough for use in production 
departments where exposure times must necessarily be fairly short. When 
the most critical radiographic inspection is required, Kodak Tndustrex' 
M Film (Data Sheet FM-25) will give radiographs having the finest 
grain and the highest contrast possible, revealing extremely small defects. 

Tndustrex' D Film (Data Sheet FM-27), is recommended for the 
radiography of thick light alloys. Although its grain is not quite as 
fine as that of Tndustrex' C Film, it is 2-3 times faster, and gives 
radiographs of high contrast and good definition. Tndustrex' D Film 
is particularly useful in departments where the X-ray unit may not be 
powerful enough to give satisfactory penetration of heavier sections when 
using Tndustrex' C Film. 

For best results in the radiography of castings having various thick- 
nesses, each thickness should be radiographed separately using the most 
suitable kilovoltage and film for each section. (The maximum kilovoltages 
for various combinations of thicknesses and films are given in a table 
in the Appendix). Alternatively, a "double-film" or "sandwich" tech- 
nique can be used, wherein, say, a sheet of Tndustrex' C Film and a sheet 
of Tndustrex' M Film are enclosed in the same cassette or film holder, and 
exposed simultaneously. The thicker sections of the specimen will be 
recorded on the faster Tndustrex' C Film, while the thinner sections will 
be accommodated by the slower Tndustrex' M Film. Careful selection of 
the kilovoltage and exposure is essential in order to obtain maximum 
value from such a technique. 

IN-14 2 



When only one film can be used, it will often be necessary to employ a 
higher kilovoltage to lower the contrast between the various sections, thus 
enabling all the thicknesses to be recorded on one film. It is essential 
that the kilovoltage chosen should produce a radiograph, on any given 
radiographic film, in which the density range is of practical use. The radio- 
graphic image of the thickest section should have sufficient density to 
achieve adequate sensitivity, while the density of the image of the thinnest 
section should not be greater than is reasonable to permit comfortable 
viewing on an illuminator. 

This useful density range will be influenced by the illuminator used; 
for example, when using the Kodak 'Industrex' Illuminator, Model 2, a 
density range of 1.5 to 3.0 is recommended for the most critical radio- 
graphic inspection, whereas a density range of 0.75 to 3.5 might be accept- 
able for routine work. For effective interpretation of the denser portions of 
the image, care should always be taken to avoid dazzle from low-density 
areas of the illuminated radiograph; the Kodak 'Industrex' High-Intensity 
Illuminator is ideal for this purpose. 

As an alternative to the lower-contrast technique given by the use of 
increased kilovoltage, additional filtration at the tube window can be used 
(1 or 2 mm of copper for example); in this instance, longer exposure times 
will be required to compensate for the increased absorption. 

Both these techniques, however, lead to poorer sensitivity of flaw 
detection than does the individual exposure of each thickness at the most 
suitable kilovoltage. 

For the examination of very thick specimens, where scattered radiation 
may degrade the quality of the image, all these films may be used 
between lead intensifying screens, which effectively minimize the effects 
of the scattered rays without affecting definition. The use of lead intensi- 
fying screens may enable the exposure time to be reduced to as little as 
one-third provided the kilovoltage is greater than 120-140 (see Data 
Sheet XR-4). 

Whenever possible, when using the films mentioned above, the image 
density should be as high as viewing conditions permit, as image contrast 
increases with film density, and the sensitivity of fault detection is thereby 
improved. 

Direct-type radiographic films are available folder-wrapped for dark- 
room loading into exposure holders or cassettes, and also wrapped 
individually in sealed envelopes ready for use. 

Additionally, 'Industrex' C, M and D Films are available in 'Ready-Pack' 
rolls. A 'Ready- Pack' roll consists of a long, continuous length of film 
sandwiched between two lengths of yellow-black duplex paper and ren- 
dered light-tight by sealing along both edges : they are available with or 
without lead intensifying screens incorporated. Any desired length of 
film can be cut from a 'Ready-Pack' roll without the need for a darkroom, 
provided that the ends are taped to exclude light. The use of radio- 
graphic film in this form has many advantages over the established tech- 
nique (i.e., the use of many separate sheets of film, overlapped to ensure 
continuity) for the radiography of long or circumferential objects, e.g., 
joints in aircraft fuselages. Wastage of film due to overlapping is 
eliminated; cassettes and darkroom-loading facilities are rendered 

3 IN-14 



superfluous; it becomes unnecessary to identify the sheets individually 
and to affix them separately to the object; and errors caused by placing 
the radiographs in the wrong sequence for inspection are thus avoided. 

Lengths of film not exceeding 48 cm (19 inches) can be processed using 
film clips or hangers and conventional tanks or processing units; 70 mm 
film in longer lengths can often be processed in spiral frame photographic 
processing units. Also, whilst other widths and lengths can be cut into 
manageable lengths for tank processing, they are best processed in roller- 
type automatic processors suchas the Kodak Industrial' X-omat' Processors. 

Further details of the range of sizes and packings in which 'Kodak' 
radiographic films are available, and of the viewing and processing 
equipment mentioned in this section, are available on application to 
Industrial Radiographic Sales, P.O. Box 66, Kodak House, Hemel Hemp- 
stead, Herts. 

Conclusion 

For the reliable X-ray inspection of light alloys (and particularly of 
magnesium alloys) it is absolutely necessary to use a suitable film having 
carefully controlled properties, to use a radiographic technique giving 
optimum conditions for flaw detection, and to process the film by a 
standardized and reliable technique (see Data Sheet XR-6). More de- 
tailed information on light-alloy radiography will be found in the literature. 

The exposure chart given in the Appendix will provide a useful starting 
point for assessing the exposures required. It should be noted, however, 
that the exposure depends largely on the type of X-ray set and the other 
conditions of use. The curves shown are, therefore, no substitute for an 
exposure chart produced using the particular equipment installed in the 
department. Methods of deriving exposure charts for X-ray units are 
described in reference 3. 

The interpretation of radiographs calls for considerable experience. 
Guidance in the identification of defects in castings is given in reference 4. 
Classified radiographs showing defects in aluminium welds are given in 
reference 5. 

References 

1 Recommendations for the X-ray Examination of Fusion Welded Joints 
in Light Alloys, Brit. Weld. J., 5, No. 2, Nov. 1958, pp. 489-491. 

2 Methods of Testing Fusion Welds in Aluminium and Aluminium Alloys, 
British Standard 3451:1962, British Standards Institution. 

3 Industrial Radiography, Kodak, 1965. 

4 Terminology of Internal Defects in Castings as Revealed by Radiography, 
British Standard 2737:1956, British Standards Institution. 

5 Classified Radiographs for Defects in Aluminium Fusion Welds, British 
Welding Research Association, 1963. 

Bibliography 

E. J. Tunnicliffe, X-rays and Light Metallurgy (in 3 parts), Light Metals, 

April 1942; Sept. 1942; Jan. 1943. 
W. E. Schall, X-rays — Their Origin, Dosage, and Practical Application, 

Wright, 8th edition, 1961. 

IN-14 4 



J. C. Rockley, An Introduction to Industrial Radiology, Butterworth, 1964. 

Welding Terms and Symbols, Part 3 — Terminology of and Abbreviations 
for Fusion Weld Imperfections as Revealed by Radiography, British 
Standard 499: Part 3: 1965, British Standards Institution. 

R. Halmshaw — Industrial Radiology Techniques, Wykeham Publications, 
1971. 



APPENDIX 

The curves below act as a guide to the exposure required to produce a 
density of 2 for thicknesses of aluminium up to 50 mm (approx. 2 inches). 
The following conditions apply : — 

Film: 'Industrex' C Film. 

Development: 4 minutes at 20°C (68°F) in DX-80 Developer. 

Focus-to-film distance : 75 cm (approx. 30 inches). 
For 'Industrex' D Film, the exposure should be multiplied by f and for 
'Industrex' M Film, by 6. 



Aluminium thickness in inches 



< 
B 



0.5 



~W 



~kT 



~W 



II 







































































































































































$ 








If 


^ 







































































































































































10 15 20 35 30 35 40 
Aluminium thickness in millimetres 



45 50 



■o 
c 
o 
w 

12 <% 



NOTE : This is only a typical exposure chart, since X-ray sets will vary 
considerably depending upon their circuitry, output and other factors. 
Ideally, an exposure chart should be made for each individual X-ray set. 



IN-14 



Most of the following data are given in British Standard 3451:1962 
(reference 2) and are reproduced here by permission of the British Standards 
Institution. 

When radiographing welds in aluminium alloys using pulsating X-ray 
generation circuits, the tube kilovoltage should not exceed the values 
given in the following table; the kilovoltage should be chosen so that the 
exposure is not less than 8 mA minutes for techniques employing medium- 
speed film (e.g., 'Industrex' D Film) or 15 mA minutes for techniques 
employing fine-grain or ultra-fine-grain film (e.g., 'Industrex' C or M 
Film). With constant potential, the kilovoltages quoted in the table 
should be reduced by 10 per cent. For magnesium alloys, lower kilo- 
voltages will apply. 



MATERIAL 
THICKNESS 



MAXIMUM KILOVOLTAGE 



Ultra-fine-groin 
film (e.g., 'Indust- 
rex 1 M Film) 



Fine-grain film 

(e.g., 'Industrex' 

C Film) 



Medium-speed film 

(e.g., 'Industrex' 

D Film) 



Up to £ in (6.4 mm) 
£--j in (6.4-12.7 mm) 
if in (12.7-19.1 mm) 
J- 1 in (19.1-25.4 mm) 



70 
80 
95 
105 



60 
70 
80 
90 



50 
55 
60 
65 



Kodak, Industrex, and X-Omat, are trade marks 



Kodak Data Sheet 
IN-14 



KODAK LIMITED LONDON 

YI254PDIN-l4/xWP 10/4-72 



WELD RADIOGRAPHY 



Since the early thirties, radiography has been mandatory in the approval 
procedure for fusion- welded Class I pressure vessels. The proven 
value of this method of non-destructive examination has led to its use for 
the examination of welds in other grades of pressure vessels 1 ' 2 , in ships' 
structures, in gas-holders and storage tanks 3 , in oil-lines and refinery 
plant 4 ' 6 , and in bridges. In addition, radiography is successfully used 
for the inspection of spot welds, and for welds in aluminium 6 ' 7 , and 
thin- walled stainless-steel specimens. 

The value of the technique is not limited solely to inspection, but it also 
offers an important aid in the training of welders 8 , because it reveals the 
quality of the trainees' work. 

As a research method, radiography has provided information on the 
effects on the weld of different welding speeds and of the size and coating 
of welding rods. Metal drop formation in welding has also been investi- 
gated by cine-radiography. 

Initially, only X-rays were available for weld radiography and its scope 
was thereby limited. But with the current list of available sources of 
gamma rays to supplement X-rays, there are few fusion welds which 
cannot be radiographed. The following notes, except where otherwise 
indicated, apply to the examination of welds both by X-rays and gamma 
rays, but for clarity only X-rays are generally mentioned. 

Both X-rays and gamma rays are dangerous to personnel, hence great 
care must be taken in the works, or on the site, to protect the operators and 
others in the vicinity. Reference should be made to the 1969 statutory 
regulations 9 , under the Factories Acts, relating to the protection of 
personnel engaged in radiography. International recommendations have 
been made by the International Commission on Radiological Protection 10 , 
and a simple explanation of the hazards involved, together with useful 
practical guidance, has been published by H.M. Stationery Office. 11 
Useful information may also be derived from the Code of Practice pre- 
pared by the Department of Health. 12 

RADIOGRAPHIC TECHNIQUE 

The valid interpretation of the resulting radiographs, whether used for 
inspection or research, depends fundamentally on accurate technique at 
every stage from the setting up of the specimen to the final inspection of 
the radiograph. 

It is important that every length of weld radiographed should be easily 
and accurately identifiable with its appropriate radiograph. This is 
essential when inspecting welded high-pressure vessels, oil lines, ships' 
structures and other large welded assemblies. Accurate and permanent 
identification can be achieved by using a system of serial numbers which 
are stamped (where this is permissible) or painted on each section, the 
particulars being reproduced on the corresponding radiograph by lead 
markers stuck to the weld section prior to the exposure and which there- 
Issue F Kodak Data Sheet 

IN-15 



fore appear as images on the radiograph. To avoid confusion arising 
from the images cast by an uneven weld metal surface, the surfaces of the 
weld should, if possible, be ground smooth. 

For the inspection of long welded seams, there are two possible methods : 

1 Examination in successive sections 

2 Examination using long strips of film 

In the first method, the weld is marked out into suitable lengths, 
arranging adequate overlaps of the films so that no section of the weld is 
missed. Typically, the weld might be divided into one-foot lengths and 
each section covered by a film 15 inches in length. Exceptions might 
occur when the curvature of circumferential seams restricts the length 
which may satisfactorily be covered by one exposure. Guidance on 
the lengths which may be covered in various circumstances is given in 
British Standards 13 ' 14 , and radiographers should familiarize themselves 
with these recommendations, particularly if they are involved in the 
critical inspection of welds for high-duty service. 

For the second method, 'Industrex' M, A, C and D Films are available 
in 'Ready-Pack' continuous rolls, with or without lead intensifying 
screens. These films are packed in a continuous light-tight sleeve, 
and any convenient length may be cut from the roll, under any lighting 
conditions. The continuous length of film may then be wrapped along 
or around the weld seam. Continuity of inspection is assured more 
simply; numbering and marking out are reduced to a minimum; film 
wastage owing to overlap is avoided, and cassette loading time is eliminated. 

The radiographic image is a " shadow picture " of the internal structure 
of the weld. For geometrical reasons, the successful interpretation of the 
resulting radiograph depends upon the accurate alignment of the X-ray 
beam. In general, the beam should be normal to the plane of the face of 
the weld. Where lack of fusion between parent and weld metal is being 
sought, the beam should be aligned along the plane in which lack of fusion 
is suspected. Consequently, three exposures might be necessary for a 
" V"-type weld, one directed along each arm of the "V" and one directed 
at right angles to the plane of the plate to check the quality of the root. 
In a "U"-type weld, both arms can, however, be satisfactorily examined 
by a single exposure made normal to the metal surface, if the focus-film 
distance is reasonably great. In some cases, the angle of projection 
of the X-ray beam with respect to the weld will also depend on the 
surrounding structure, and here experience is necessary when deciding on 
the best projection and in interpreting the resulting radiograph. 

The efficiency with which the eye can detect differing densities in two 
neighbouring regions (and therefore the sensitivity) depends on the sharp- 
ness of the line of demarcation between the regions. The sharper this 
line, the more readily will the eye detect this difference. This is illustrated 
in Figure 1, which shows, on an enlarged scale, two regions of different 
density, in one case separated by a diffuse edge and in the other by a sharp 
edge, the extremes of density in each case being identical. Although the 
contrast is actually the same, the lower strip, owing to the diffuse boundary, 
appears to have lower contrast than the upper strip. The two diagrams 

IIM-15 2 




— B 



IDEAL 
DEFINITION 




— B 



POOR 
DEFINITION 



Figure I 

on the right show, graphically, the variations in density along the sections 
AB. 

From geometrical considerations, it is obvious that the finest definition 
in the resulting radiograph will be achieved only when a point source 
of radiation is used. This is not, of course, practically possible, but 
every effort should be made to minimize unsharpness in the radio- 
graphic shadow by using an X-ray tube with as small a focal spot as is 
consistent with reasonable exposure times, or a gamma-ray source of small 
dimensions. Loss of definition due to the finite size of the focal spot or 
source is reduced with increasing focus-to-film or source-to-film distance 
but, as the necessary exposure increases as the square of the distance, a 
practical limit is determined by the necessity for keeping the exposure 
time within acceptable limits. The optimum focus-to-film distance will 
depend on the thickness of the specimen being radiographed, and on the 
focal-spot size, the usual distance being 2 to 3 feet (0.6 to 0.9 m). Recom- 
mendations for ratios of focus-to-film and source-to-film distance to 
throat thickness of weld are given in references 5, 13 and 14. 

It is important that the object-to-film distance should be as short as 
possible. Close contact between the cassette and the surface of the 
specimen should be maintained. Appropriately curved cassettes (film 
holders) or flexible cassettes are therefore essential when radiographing 
circumferential, welded seams; alternatively, 'Ready-Pack' film may be 
used. 

RADIOGRAPHIC FILM AND ITS CHOICE 

Radiographic films have been designed for the various types of engineer- 
ing radiography and the choice of the appropriate film for the work being 
undertaken is of utmost importance. Some of these films are made 
specially for use with fluorescent-salt intensifying screens; some have 
higher contrast than others. The higher the contrast of the film, the greater 
will be the differentiation in the image between areas corresponding to 



IN-IS 



slightly different degrees of X-ray absorption. On the other hand, as the 
contrast of the film increases, so its exposure latitude decreases. The grain 
size of films is a further factor of importance, as the finer grained the image 
the better its detail. Unfortunately, the finer the grain size of a film the 
lower is its speed. The various types of radiographic films available repre- 
sent a compromise between fineness of grain, speed, contrast, and latitude, 
appropriate to the type of work for which they are designed. Consequently 
they should be chosen with care in relation to the job. 

The films available for weld radiography can be broadly divided into 
two groups, namely: 

1 "Screen-type" films for exposing between fluorescent-salt screens 

2 "Direct-type" (non-screen) films for exposing between metal in- 
tensifying screens, or without screens 

These films are available in a wide range of speed and grain size, the finest- 
grained being the slowest. 

For the best results in weld radiography, the film should have the finest 
grain and highest contrast consistent with a practicable exposure time. 
The density should be as high as possible, and certainly not less than 
2.0 when using lead intensifying screens, described later, or a density of 
between 1.3 and 2.3 for films exposed with fluorescent-salt screens. 13 ' 14 
When working with high densities, it is essential to use X-ray illuminators 
(such as the Kodak Tndustrex' X-ray Illuminator, Model 2, or the 
'Industrex' High Intensity Illuminator) which give adequate brightness to 
ensure ready interpretation of the radiographs. 

'Kodak' Blue Brand Medical X-ray Film (Data Sheet FM-18) is designed 
for use with fluorescent-salt intensifying screens. Whilst this film can be 
used with High Speed Intensifying Screens to yield maximum speed, it is 
usually used only with High Definition Screens for weld examination; 
this latter combination is the only type recommended in most codes and 
standards. 6, 13 However, the use of the fluorescent-salt screen is being 
steadily replaced in such codes and standards by the lead screen described 
in the next section. 

The choice of direct type radiographic film for any particular type of weld 
examination depends on the nature of the job, and on the defect sensitivity 
required. Ideally, the technique should be as sensitive as is practicable. 
For light-alloy welds (see Data Sheet IN- 14) and welds in steel plate, the 
very fine-grained 'Industrex' M Film (Data Sheet FM-25) will provide 
the most critical technique, whether exposed with or without lead in- 
tensifying screens. Where the very long exposures involved can be 
tolerated, this film is undoubtedly the best for gamma-radiography. As 
this film is rather slow, the compromise of higher speed and fine grain of 
'Industrex' C or A Films (Data Sheets FM-26, 28) makes them ideal 
choices both for X-ray and gamma ray exposures whenever optimum fault 
sensitivity is required. These films are used extensively in the inspection of 
welds in light alloys and in ferrous materials, usually with lead intensifying 
screens in the case of ferrous metals. Such a combination is favoured for 
radiographs of stainless-steel welds. For the thinner section welds, 
'Industrex' C film can, of course, be used without screens. 

IN-15 A 



Where higher speed is necessary, 'Industrex' D Film (Data Sheet 
FM-27), is the obvious choice for all types of weld, and its high contrast 
is particularly valuable. It is usually exposed between lead intensifying 
screens but may be used without screens for light-alloy welds and thin 
steel welds. 

For the shortest exposure, 'Kodirex' X-ray Film (Data Sheet FM-17) 
represents the optimum combination of speed, contrast, and grain size. 
However, there is some loss of definition, and the use of this film is often 
not recommended. 5 ' 6 ' 13 ' 14 

Careful handling and processing of films are of paramount importance in 
weld radiography (Data Sheets XR-6 and XR-7). The greatest care must 
be taken to ensure that no chemical stains, liquid splashes, pressure 
marks, or other adventitious markings appear on the film, because such 
marks seriously handicap, even if they do not entirely prevent, accurate 
interpretation. 

INTENSIFYING SCREENS 

Fluorescent-salt intensifying screens of calcium tungstate, as sometimes 
used in weld radiography, permit economic exposure times with low- 
powered portable X-ray units, at some expense of definition; fine-grain 
salt (tungstate) screens, as such 'Kodak' Fine-Grain Intensifying Screens, 
are recommended so as to minimize the unsharpness caused by such 
screens. Lead foil screens are, however, finding increasing favour in 
weld radiography, particularly where high-kilovoltage radiation is used 
and when fine details, such as cracks, are being sought. These lead 
screens do not allow so great a reduction in exposure as salt screens but 
possess the advantage of being grainless and therefore do not affect defini- 
tion provided that there is good contact between the screens and film. 
Moreover, lead screens assist in the absorption of scattered radiation 
arising from the specimen. 

Both salt and lead intensifying screens should be treated with great care 
and should be kept free from dust, stains, and scratches. Similarly, care 
must be taken to avoid scratching or rubbing the screens or films when 
loading them into cassettes. 

EXPOSURE 

The exposure conditions should be obtained from an appropriate 
exposure chart and, in general, the lowest kilovoltage consistent with 
adequate penetration and reasonable exposure time should be chosen to 
ensure high radiographic contrast in the resulting radiograph. When 
gamma rays are used, the choice of the type, size, and activity of the source 
is important (see Data Sheet IN- 16). Detailed guidance on exposure is 
given in British Standards. 13 ' 14 

SENSITIVITY 

The sensitivity of fault detection is usually expressed as the smallest per- 
centage variation in the total thickness of the plate which is discernible in 
the radiograph. Thus the smaller the value of the percentage quoted as 
sensitivity, the higher is the efficiency of fault detection. Faults corres- 

5 IN-15 



ponding to less than 2 per cent of the thickness of the weld should be 
readily shown in an average radiograph made under the best routine 
conditions. This value will, however, depend on such factors as, for 
X-rays : the kilovoltage, the filtration in the X-ray beam, the focal-spot size, 
and the focus-to-film distance; for gamma-rays : the radioactive isotope, its 
geometric size, and the source-to-film distance. Additionally, the 
following factors will also determine the sensitivity — the object-to-film 
distance, the type of intensifying screen and radiographic film, the 
processing of the film, and the viewing conditions. 

Image-quality indicators (previously known as penetrameters, and now 
usually known by their initials I.Q.I.) should always be used in weld 
radiography to indicate that effective penetration of the weld by the 
radiation has been achieved and to serve as a gauge of the quality of the 
radiographic technique. For this latter reason, the image quality 
indicator (or I.Q.I.) should be of the same material as that being 
examined. It is usually in the form of a thin step- wedge of the metal, or 
of wires of increasing thickness. 

Of the various types of I.Q.I, that have been designed, the step-hole 
type has probably been most commonly used in Great Britain. The 
wire-type, however, is now rapidly gaining favour. Details of suitable 
designs are published by the British Standards Institution. 15 

As the imperfections in the specimen may be situated at any depth, 
it is customary to place the I.Q.I, on the side of the job remote from the 
film, because the further the defect from the film, the less clearly it is 
revealed. Accordingly, the sensitivity determined by the I.Q.I, represents, 
as it should, the worst conditions rather than the best. Note that an I.Q.I. 
is essentially an instrument to indicate effective penetration, and as a check 
on the quality of the radiographic technique used. It should not be used as 
a definite criterion for determining the magnitude of internal flaws. It will 
be obvious that the I.Q.I, should be placed so that its image does not 
interfere with that of the region being inspected; for this reason the 
step-hole type is usually placed parallel to and slightly away from the weld. 
The wire type, however, is placed so that its wires are transverse to the 
length of the weld and across the weld itself. 

The actual figure recorded as the I.Q.I, sensitivity depends not only on 
the radiographic technique but also on the type of I.Q.I, and the way in 
which the sensitivity figure is assessed from its image. 15 

INTERPRETATION OF RADIOGRAPHS 

The radiographs should be very carefully scrutinized and compared with 
the portion of the plate radiographed in order that surface markings may 
be identified with the shadows on the radiograph produced by them. All 
other shadows on the radiograph should then receive consideration and 
interpretation. The films should be viewed on a specially designed X-ray 
film illuminator of sufficient brightness, with masking diaphragms to 
limit the illuminated area to the size of the film; this ensures optimum con- 
ditions for the detection of the important but subtle density differences 
in the image. 

IN-15 6 




Figure 2. Radiograph revealing uniform porosity in \-inch steel weld. 

Radiography, both by X-rays and gamma rays, is usually capable of 
revealing all the important defects likely to arise in welding, such as : 

1 Porosity and other gaseous defects 

2 Inclusions of all types 

3 Incomplete root penetration 

4 Lack of root fusion 

5 Cracks 

A full list of the weld defects which may be detected radiographically, 
together with illustrations and descriptions of the corresponding radio- 
graphic images, are given in references 16 and 17. 

Porosity, for instance, is revealed in the radiograph by circular spots, 
denser than the surrounding image and occurring either in groups or 
chains within the image of the weld. A typical radiographic image of 
uniform porosity in a weld is shown in Figure 2. 

Inclusions, particularly of slag, are also characterized by denser regions 
in the radiograph, but these have an angular appearance. Linear 
inclusions are revealed by a dark ribbon-like shadow with irregular edges, 
parallel to the length of the weld, as shown in Figure 3. 

Incomplete root penetration is indicated by a dark continuous or inter- 
mittent band parallel to the length of the weld and generally coinciding 
with its centre line: usually, at least one side is straight. 

Lack of root fusion is indicated by a fine, straight, dark line along or 
near the centre of the weld image. 

Cracks in weld metal usually occur in a plane normal to the surface 
of the plate and thus are favourably placed for detection by X-rays. They 
appear in the radiograph as fine, dark, tortuous lines or as fine dark 
wavy lines which are sharp when the X-ray beam is passing along the plane 
of the crack, and more diffuse and less dense as the angle between the 
plane of the crack and the X-ray beam increases. They may therefore be 

7 IN-15 



•"*■ 



■I11111 






^^^^m 



Extent of weld 



5W"»* 




CM® 



■BsSfwsSSF 




Figu re 3. 7op — radiograph revealing linear inclusions in weld root. 

Bottom — section through weld at point indicated by line A in 

radiograph above. 

recorded as a series of cracks which are apparently unconnected. For the 
same reason cracks which occur parallel to the surface of the plate or 
approximately so will not be recorded by radiography. Where cracks are 
suspected from the image, further exposures with the beam at slightly 
different angles from the first often assist in revealing whether the defect 
is a crack or is due to some other cause : the image of the crack varies 
appreciably with slight changes in beam direction. 

Where flaws are shown to exist in any section of a weld of sufficient 
importance to justify the cutting out and re-welding of that section, radio- 



IN-15 



graphic inspection should be critically applied to the re-welded section. 
In certain cases it is desirable to locate the position of a particular defect 
in order to estimate its likely effect on the strength of the weld. This 
may be achieved by stereoscopy or by one of the usual localisation methods 
(see Data Sheet XR-3). 



REFERENCES 

1 Fusion Welded Pressure Vessels for Use in the Chemical, Petroleum and 
Allied Industries, Part 1, Carbon and Low Alloy Steels, British Standard 
1500:1958, British Standards Institution. 

2 Specification for Fusion Welded Pressure Vessels (Advanced Design and 
Construction) for Use in the Chemical, Petroleum, and Allied Industries, 
Part 1, Carbon and Ferritic Alloy Steels, British Standard 1515:1965. 
British Standards Institution. 

3 Specifications for Vertical Mild Steel Welded Storage Tanks with Butt- 
Welded Shells, for the Petroleum Industry, Part 2, Site Erection, Inspection 
and Testing, British Standard 2654:1961, British Standards Institution. 

4 Piping Systems for Petroleum Refineries and Petrochemical Plants, 
British Standard 3351:1971, British Standards Institution. 

5 Specification for Field Welding of Carbon Steel Pipelines, British 
Standard 4515: 1969, British Standards Institution. 

6 Fusion Welded Pressure Vessels for Use in the Chemical, Petroleum 
and Allied Industries, Part 3, Aluminium, British Standard 1500:1965, 
British Standards Institution. 

7 Methods of Testing Fusion Welds in Aluminium and Aluminium Alloys, 
British Standard 3451:1962, British Standards Institution. 

8 Tests for Use in the Training of Welders, British Standard 1295:1959, 
British Standards Institution. 

9 The Ionising Radiations (Sealed Sources) Regulations, 1969, Statutory 
Instrument No. 808, H.M. Stationery Office, 1969. 

1 Report of Committee III on Protection against X-rays up to Energies of 
3 MeV and Beta and Gamma Rays from Sealed Sources, Pergamon Press, 
1960. 

9 IN-15 



1 1 Ionising Radiations : Precautions for Industrial Users, Ministry of 
Employment and Productivity, H.M. Stationery Office. 

12 Code of Practice for the Protection of Persons Exposed to Ionizing 
Radiations, Department of Health and Social Security, H.M. Stationery 
Office. 

1 3 General Recommendations for the Radiographic Examination of Fusion 
Welded Butt Joints in Steel, British Standard 2600:1962, British Standards 
Institution. 

1 4 General Recommendations for the Radiographic Examination of Fusion 
Welded Circumferential Butt Joints in Steel Pipes, British Standard 
2910:1965, British Standards Institution. 

1 5 Specification for Image Quality Indicators for Radiography and Recom- 
mendations for their Use, British Standard 3971: 1966. British Standards 
Institution. 

1 6 Welding Terms and Symbols, Part 3, Terminology of and Abbreviations 
for Fusion Weld Imperfections as Revealed by Radiography, British 
Standard 499 -.Part 3:1965, British Standards Institution. 

1 7 Classified Radiographs for Defects in Aluminium Fusion Welds, British 
Welding Research Association, 1958. 



BIBLIOGRAPHY 

J. F. Hinsley, Non-Destructive Testing, Macdonald and Evans, 1959. 
J. C. Rockley, An Introduction to Industrial Radiography, Butterworth, 1964. 
Industrial Radiography, Kodak, 1965. 

M. D. Jackson, Welding Methods and Metallurgy, Charles Griffin 1967. 
R. Halmshaw, Physics of Industrial Radiology, Heywood Books, 1966. 
R. H. Herz, The Photographic Action of Ionizing Radiations, Wiley 
Interscience, 1969. 



Kodak, Industrex and Kodirex are trade names 



Kodak Data Sheet KODAK LIMITED LONDON 

IN-IS 

YI253PDIN-I5/XWPI0/4-72 



GAMMA-RADIOGRAPHY 



The scope of non-destructive inspection by radiography has been extended 
considerably by the use of gamma rays in addition to X-rays. In recent 
years, radioactive isotopes have become readily available and have almost 
entirely replaced radium or radon, previously the only suitable sources 
generally available. 

The great penetration of the gamma rays from most of these sources, 
which is comparable with that of X-rays generated from about 500 to 
2000 kV depending upon the radioactive source, makes such sources 
particularly valuable where the thickness or density of the specimen is 
beyond the range of the available X-ray equipment. Where X-rays of 
sufficient penetration are available, however, their use is generally to be 
preferred since better radiographic sensitivity and shorter exposure times 
may be achieved. 

The relatively small size of the equipment necessary frequently makes 
gamma ray sources ideal for radiography on sites inaccessible to bulky 
X-ray apparatus. Additionally, these sources may be suitable for work 
where the higher initial cost of X-ray equipment is not warranted. 

In earlier days, gamma-radiography was undertaken with the natural 
radioactive element radium 1 , or with radon 2 , the radioactive gas emitted 
by radium; these sources are still available but, as mentioned above, they 
have been superseded by radioisotopes, which have led to more effective 
techniques of gamma-radiography. The most commonly used are 
cobalt-60 ( 60 Co), caesium-134 ( 134 Cs), caesium-137 ( 137 Cs), iridium-192 
( 192 Ir), and thulium-170 ( 170 Tm); these sources are obtainable from the 
Radiochemical Centre, Amersham, Buckinghamshire, England, from 
which full details of price, availability, size, and other data should be 
obtained. 

CHARACTERISTICS OF GAMMA RADIATION 
Energy 

The energy of gamma radiation depends upon its wavelength; the 
shorter the wavelength, the greater the energy or penetrating power. 
Energy is usually expressed in "electron volts" and the commonly used 
unit is that of 1 MeV (1 million electron volts). 1 MeV is roughly compar- 
able with 1 MV X-rays. 

Rate of decay 

Different radio-active sources decay at different rates and this decay is 
exponential. Thus, the total life of a source is an infinite time but the 
time taken to decay to one half of the initial gamma ray intensity is a 
fixed and finite time for any given source. This value is known as the 
"half-life" and may be taken as a useful measure of the rate of decay. 

Unit of radio-activity 

The activity or strength of a radio-active source is usually expressed in 
curies (lCi=3.7x 10 10 atomic transformations per second). The 
sub-multiple of the curie is the millicurie (mCi), and the multiple, the 
kilocurie (kCi). 

Issue E Kodak Data Booklet 

IN-16 



ARTIFICIAL RADIOISOTOPES 

Cobalt-60 3 emits gamma rays having a penetration approximating 
to that of radium and radon, i.e., equivalent to X-rays of about 1000- 
2000 kV: its half-life is 5.3 years. Caesium-134 has a half-life of 
2.1 years and caesium-137 a much longer half-life of 30 years. Both 
these sources are roughly equivalent to 750-800 kV X-rays, but caesium- 
134 has the advantage of a greater gamma ray output for comparable 
source sizes. Iridium- 192 has fairly similar properties, although of 
somewhat longer wavelengths, approximating to 500 kV X-rays; the 
half-life of iridium- 192 is 74.4 days but the longer wavelengths give 
slightly higher contrast. Thulium- 170 has the longest wavelength of all 
these sources and emits radiation of about the same quality as 180 kV 
X-rays; its half-life is 127 days. 

The activity of the sources depends, in the case of cobalt-60, iridium- 
192, and thulium- 170, on their initial activation in the nuclear reactor as 
well as on their size. They are therefore available in a fairly wide range 
of sizes and activities. Caesium-137 is a fission product and activity is 
more directly related to the source volume. The table below shows 
typical source sizes and activities. 



RADIOISOTOPE 


ACTIVE 
MATERIAL 


DIMENSIONS— 
(millimetre) 


MAX. 
ACTIVITY (Ci) 


Cobalt-60 


Metal cylinder 


1 X 1 

2 X 2 

3 x 3 

4 x 4 


0.9 

5 
14 
30 


Caesium-134 


Cs glass 


2x2 

3 x 3 

4 x 4 


0.9 
4.5 
10 


Caesium-137 


Cs glass 
Cs glass 
Cs glass 
CsCI pellet 
CsCI pellet 


dia. 6 

dia. 6 

dia. 6 

6 x 6 

6 x 6 


1 

2 

3 

5 

10 


lridium-192 


Metal cylinder 


0.5 x 0.5 

1 X 1 
1.3 x 1.3 

2 x 2 

3 x 3 

4 x 4 
6 x 6 


1 

6.5 

12 

30 

65 

110 

250 


Thulium-170 


Tm 2 3 pellet 


0.5 x 0.5 
1 X 1 
2x2 
3 x 3 


0.6 

5 
15 
35 



SCOPE OF GAMMA RAY SOURCES 

The general uses of the above named sources may be quoted as follows, 
but it must be realised that these limits are only approximate. Greater 
thicknesses can be penetrated but the exposure times may be very lengthy. 
The lower limits are restricted by considerations of sensitivity of flaw 



IN-16 



detection. Provided the user is satisfied that adequate sensitivity for the 
purpose is being achieved, then the lower limits may be reduced. 



SOURCE 



Cobalt-60 
Caesium- 1 34\ 
Caesium-137 J 
lridium-192 
Thulium-170 



POSSIBLE 
THICKNESS RANGE 



5 - 20 cm (2 - 8 inch) steel 

2.5- I0cm(l -4inch)steel 

0.6 -9 cm (0.25 -3.5 inch) steel 

0.8 -3.8 cm (0.3- I.Sinch) 

aluminium 



OPTIMUM 
THICKNESS RANGE 



7. 5-15 cm (3-6 inch) steel 
4.5-7.5cm(l.75-3inch)steel 
2.5 -4.5 cm (I - 1.75 inch)steel 



SAFETY PRECAUTIONS 

Owing to the dangerous character of gamma rays, the sources are 
generally used shrouded in heavy metal containers, of lead or of tungsten 
alloy 4 ; spent or depleted uranium has also been used recently. Various 
types of containers are available commercially which usually incor- 
porate a conical opening, limiting the radiation to a well-defined divergent 
beam, and a hinged or screwed cover to close the aperture when the 
source is not in use. In addition, most containers provide for the 
removal of the radio-active source on the end of a long rod or cable, 
so that the source may be removed and placed in a confined space or 
positioned for work where radiation over an angle of 360° may be required 
(Figures 1 and 2). Many large containers for highly active or kilocurie 
sources are operated by remote control, thus providing further safety 
for the operator. 

Considerable care must be exercised when handling and using gamma 
ray sources and it must be emphasised that the use in industry of such 
sources is covered by statutory regulations 5 and the Radio-Active 
Substances Act, 1949. The effects of gamma-radiation on the human 
body can be highly dangerous and operators concerned with the work 
should be constantly aware of the dangers and should take every possible 
precaution. In work-places covered by the Factories Act, the regulations 
referred to above 5 must be applied, and further guidance can be obtained 
from other sources. 6 ' 78 

MAKING THE RADIOGRAPH 

If the source is in a heavy metal container with outlet port, the actual 
set-up for the exposure (Figure 3) is similar to that used in X-radiography, 
with the obvious substitution of the gamma ray source for the X-ray tube. 
When using an unshrouded source, emitting full intensity in all directions, 
several exposures may be made at the same time by arranging the speci- 
mens around the source (Figure 1). This technique is particularly valuable 
for the inspection of cylindrical specimens ; for example, circumferential 
butt welds in pipes 9 , and pressure vessels 9 ' 10, where the gamma ray source 
may be placed at the centre of curvature when the source-to-film distance 
is sufficiently small to give a reasonable exposure time (Figure 2). This 
technique can usefully be employed for vessels and pipes up to about 1 
metre or 3 feet in diameter. Above this diameter, the exposure time may 
become unduly long owing to the increased source-to-film distance, but this 



IN-16 





Figure 



Figure 2. Films in cassettes or a continuous 
strip of 'Ready-Pack' film. 




FILM IN HOLDER (FILM CASSETTE) - 




Figure 3 



FRONT OF 
FILM HOLDER 



FRONT 
INTENSIFYING SCREEN 



BACK 

INTENSIFYING SCREEN 



BACK OF 
FILM HOLDER 



will depend on the activity of the source. Due regard must of course be paid 
in all these techniques to the requirements of good geometry of image 
formation; the source size, source-to-film distance, and object-to-film 
distance, must be adjusted to give satisfactory geometry 9 . 10 . 11 ; these 
principles are described in Data Sheet XR-2. 

Gamma-radiographs are normally made on direct-type radiographic 
films such as 'Kodirex', or one of the 'Industrex' range of films, exposed 
between lead intensifying screens (see Data Sheet XR-4). Gamma- 
radiography of circumferential welds in vessels or pipes may be facilitated 
by the use of 'Ready-Pack' continuous rolls, which incorporate lead 
screens and film in a light-tight sleeve. Any convenient length may be 
cut from the roll in any lighting conditions and the continuous length of 
film may then be wrapped around the weld seam. Continuity of inspection 
is assured more simply; numbering and marking out of the specimen is 
reduced to a minimum; film wastage through overlap is avoided; and 
cassette-loading and handling time is eliminated. The use of a screen-type 
radiographic film in conjunction with salt intensifying screens is not 
favoured 9 ' 10 ' n , because of the inherent unsharpness arising from the 
use of such screens; consequently, the sensitivity of flaw detection is likely 
to be poor. 

The lead intensifying screen technique is generally preferred since these 
screens give superior definition which materially offsets the low image 
contrast due to the penetrating nature of the radiation. In general, 
standard lead intensifying screens — front screen 0.10 mm (0.004 inch) 



IN-16 



thick, back screen — 0.15 mm (0.006 inch) thick can be used with iridium- 
192 and caesium-137, but a slight advantage may be gained by exposing the 
film between two "back" screens when using cobalt-60. Lead screens do 
not offer any advantage with thulium- 170, unless the front screen is very 
thin. Where the image must reveal very fine details, e.g., fine cracks, the 
fine-grain, high-contrast, direct-type ' Industrex' M, T, A and C films are re- 
commended. For slightly less critical work, ' Industrex' D film gives adequate 
exposures in about half the time required for 'Industrex' C film. 'Kodirex' 
X-ray film gives the fastest exposures, using lead intensifying screens, but 
the use of this film is only recommended when it is known to be adequate 
for the degree of sensitivity of flaw detection required. For the gamma- 
radiography of welds, the use of 'Kodirex' film is not normally recom- 
mended. 9 ' 10 ' u All these radiographic films, exposed between lead 
intensifying screens, are eminently satisfactory for gamma-radiography: 
their range of grain, speed, and contrast covers all the requirements. 
The best compromise between radiographic sensitivity of flaw detection 
and speed is undoubtedly given with 'Industrex' C film. 

Where a specimen has large thickness variations, a "sandwich" technique 
may be useful in avoiding the need for two or more separate exposures. 
This technique consists of using in the same cassette films, or film-screen 
combinations, of different speeds, thus exposing for a thin section with the 
slower film and for the thicker section with the faster film. 

In the case of 'Industrex' M, A and C films, higher speed and contrast 
can also be achieved by prolonging development time to the maximum 
recommended for each film; the decrease in sharpness is not significant, 
and this practice can be regarded as standard when using 'Industrex' M 
film in this type of work. With 'Industrex' D and 'Kodirex' films, this 
practice is not normally recommended. 

The intensifying factors of the screens mentioned above depend upon 
various considerations, including the quality of the gamma rays, and the 
filtration due to the specimen. Usually, an intensifying factor of 2 may 
be assumed for all types of film when using lead intensifying screens. 

EXPOSURE 

The exposure times required depend on many variables such as the 
material and thickness of the specimens, the source-to-film distance and the 
activity of the source. As a general rule, exposures may run into hours 
and the correct exposure is best found by reference to exposure charts or 
special slide-rules evolved for the purpose. 12 Both exposure charts and 
slide-rule scales are dependent on the speed of the film used. 

In the Appendix to this Data Sheet, exposure charts are shown giving 
typical exposures for various sources. These exposure charts will usually 
prove reliable in practice, but many possible causes of variation exist and 
practical trial may indicate necessary changes. 

Corrections for variations from the source-to-film distance given in the 
exposure charts may be made by utilising the inverse-square law, whether 
films are used with or without lead screens. Gamma-radiographs are 
normally made with direct-type films with which contrast increases with 
film density up to very high densities. It is therefore advisable to take 
advantage of this characteristic by exposing to the highest available film 
density; a minimum density of 2.0 is recommended. 9 - 1011 

5 IN-16 



INTERPRETATION OF GAMMA-RADIOGRAPHS 

In castings, any imperfections are revealed, on the radiograph, by 
images which are usually darker than the surrounding image, although 
there is the possibility of lighter images occurring as, for instance, when 
segregation or inclusion of a heavier component is present. In weld 
inspection, the aim is to detect any internal imperfections such as cracks, 
inclusions, gas pores, lack of fusion and incomplete penetration. 

The clues to the cause of these images are given by their shape, contrast, 
size, and position, but accurate interpretation calls for both long experience 
and a sound knowledge of the job being examined, and of its potential 
defects. Great caution is necessary in differentiating between these 
images and those due to surface marks on the job or fortuitous images 
which can arise from faulty handling, exposing, or processing of the film. 

The form of images of defects in welds and castings has been described 
in certain British Standards. 13 ' 14 

The interpretation of gamma-radiographs is similar to that of radio- 
graphs made with X-rays, but generally somewhat more difficult because 
of:— 

1 The low image-contrast due to the penetrating nature of the radiation; 

2 The use of short source-to-film distances, are sometimes used unwisely to 
offset the longer exposure times, leading to greater penumbral effects 
and more image magnification. 

The low image contrast is of marked value in the inspection of speci- 
mens having wide variations in thickness, e.g., assemblies, since the whole 
of the specimen may be recorded on one film. It is important to note, 
however, that the sensitivity of fault detection suffers with such reduction 
in image contrast. 

REFERENCES 

1 V. E. Pullin, Engineering Radiography, Bell, 1934, pp. 103-113. 

2 J. A. T. Dawson, Radon, Its Properties and Preparation for Industrial 
Radiography, J. Sci. Instr., 23, No. 7, July 1946, pp. 138-44. 

3 Radiation Sources for Industry and Research, Radiochemical Centre, 
Amersham, Buckinghamshire. 

4 Specification for Gamma Radiography Exposure Containers for Industrial 
Purposes, and their Source Holders, British Standard 4097: 1966, British 
Standards Institution. 

5 The Ionising Radiations {Sealed Sources) Regulations, 1969, Statutory 
Instrument No. 808, H.M. Stationery Office. 

6 Ionising Radiations : Precautions for Industrial Users. Safety, Health 
and Welfare Booklets, New Series No. 13, Dept. of Employment and 
Productivity. H.M. Stationery Office, 1969. 

7 Report of Committee III on Protection against X-rays up to Energies of 
3 MeV and Beta and Gamma Rays from Sealed Sources, Pergamon Press, 
1960. 

8 Recommendation for Data on Shielding from Ionizing Radiation, Part 1, 
Shielding from Gamma Radiation, British Standard 4094: Part 1: 1966, 
British Standards Institution. 

IN-16 6 



9 General Recommendations for the Radiographic Examination of Fusion 
Welded Circumferential Butt Joints in Steel Pipes, British Standard 2910: 
1965, British Standards Institution. 

1 General Recommendations for the Radiographic Examination of Fusion 
Welded Butt Joints in Steel, British Standard 2600 : 1962, British Standards 
Institution. 

1 1 Methods for Non-Destructive Testing of Steel Castings, British Standard 
4080: 1966, British Standards Institution. 

12 Exposure Calculator for Gamma-Radiography, Steel Casting Research 
and Trade Association. 

1 3 Welding Terms and Symbols, Part 3 Terminology of and Abbreviations 
for Fusion Weld Imperfections as Revealed by Radiography, British Standard 
499: Part 3: 1965, British Standards Institution. 

14 Terminology of Internal Defects in Castings as Revealed by Radiography, 
British Standard 2737: 1956, British Standards Institution. 



BIBLIOGRAPHY 

J. F. Hinsley, Non-Destructive Testing, Macdonald and Evans, 1959. 

J. C. Rockley, An Introduction to Industrial Radiology, Butterworth, 
1964. 

Industrial Radiography, Kodak, 1965. 

R. Halmshaw (editor), Physics of Industrial Radiology, Heywood Books, 
1966. 

B. J. Wilson (editor), The Radiochemical Manual, second edition, The 
Radiochemical Centre, Amersham, 1966. 

R. Halmshaw, Industrial Radiology Techniques, Wykeham Publications, 
1971. 

R. Langley, Gamma Radiology — Review 10, The Radiochemical Centre, 
Amersham, 1971. 



APPENDIX 

LIST OF EQUIPMENT MANUFACTURERS 

The following is a list of some of the manufacturers of gamma ray 
exposing devices in this country; it should not, however, be regarded as 
comprehensive. Details of the equipment available should be obtained 
direct: — 

CSW Engineering Maxted Road, Hemel Hemsptead, 

Hertfordshire. 
Exal Telford Road, Houndsmills 

Estate, Basingstoke, Hampshire. 
Gamma Rays Limited Mucklow Hill, Halesowen, 

Worcestershire. 

7 IN-16 



Gammax Limited 



45-51 Wharfdale Road, London, 

Nl 9SG. 

Equipment Division, Billington 

Road, Leighton Buzzard, Bedford- 
shire. 

103-105 Oaklands Road, London, 

NW2 6DF. 

8-12 Rickett Street, London, 

SW6. 

Marshgate Drive, Hertford, 

Hertfordshire. 

Blackhorse Road, Letchworth, 

Hertfordshire. 
Photographic equipment for gamma-radiography is available from 
Kodak Limited. Further information may be obtained from Industrial 
Radiography Sales Department at Kodak House, Hemel Hempstead, 
Hertfordshire. 



Industrial Testing Limited 



Inspection Equipment Limited 



Pantatron Limited 



Vitosonics Limited 



Wells-Krautkramer Limited 



EXPOSURE CHARTS 

On the following pages, typical exposure charts are given for the more 
commonly used sources, using 'Industrex' C film in the radiography of 
steel. For exposures using other 'Kodak' radiographic films or for testing 
other materials, the following approximate conversion factors may be 
applied : — 

Conversion factors for other 'Kodak' radiographic films 



RADIOGRAPHIC FILM 


RELATIVE EXPOSURE REQUIRED 


'Kodirex' 
'Industrex' D 
'Industrex' C 
'Industrex' A 
'Industrex' T 
'Industrex' M 


r 

3 
2 

T 
1 

4 

3 
6 



Conversion factors for other test materials 



MATERIAL 


THICKNESS EQUIVALENT 
TO 1 UNIT OF STEEL 


Bronze, brass 


0.9 


Steel 


1.0 


Cast iron 


I.I 


Aluminium 


2.9 


Concrete 


3.6 



IN-16 



TYPICAL EXPOSURE CURVES WITH 'INDUSTREX' C FILM 

Source: CAESIUM- 1 34 Material: STEEL 

Source-to-Film Distance: Im (39 inches) Lead Intensifying Screens 

Development: 4 minutes in DX-80 at 20C (68°F) 



100 - 

90 

80 

« 70 
^ £ 60 

° 1 

S= 50 

«> ~ 

J £ 40 

.a c 

f" 30 
20 
10 

I 



4 t-f/ -$/"*/ 

Y^jfyJy 



10 50 

Exposure in curie-hours 



100 



500 



Source: CAESIUM-137 Material: STEEL 

Source-to-Film Distance: Im (39 inches) Lead Intensifying Screens 

Development: 4 minutes in DX-80 at 20°C (68°F) 



100 
90 




' 














1 ! 
j y 












-4 


80 


i : ; 






















70 




























3 


at 

i 60 






~\<y 


^y 










\ 




















K*y, 
















£ 40 





— - 




" 








^ &%S<\y/ 








\ 










c 


r /^ 




- 






















































-1 


10 














^ i 
































i 


| 




i 


i 

























10 50 100 

Exposure in curie - hours 



500 



IN-16 



TYPICAL EXPOSURE CURVES WITH 'IKDUSTREX* C FILM 



Source: COBALT-60 Material: STEEL 

Source-to-Film Distance: Im (39 inches) Lead Intensifying Screens 

Development: 4 minutes in DX-80 at 20°C(68°F) 



160 
140 
120 

Si a> 

" £100 

S= 80 
I E 
~.E60 

40 

20 



















/ 




















\? 


y< 
















































































S^y 







































































































10 50 

Exposure in curie-hours 



100 



4 S 
3 S = 

i.= 



500 



Source: IRIDIUM-192 Material: STEEL 

Source-to-Film Distance: lm(39 inches) Lead Intensifying Screens 

Development: 4 minutes in DX-80 at 20°C(68°F) 




10 50 

Exposure in curie -hours 



100 



500 



IN-16 



10 



Suggested film factors for use with the B.S.C.R.A. (S.C.R.A.T.A.) 
gamma ray slide rule for alternative processing conditions are given 
below : — 



RADIOGRAPHIC 
FILM 


PROCESSING 
DX-80 : 4 min 


CONDITIONS AT 20°C (68°F) 
DX-80 : 8 min DX-80 : 10 min 


'X-Omat'* 


'Kodirex' . . . 
'Industrex' D . . 


10 
20 


t 

t 


t 
t 


t 
t 


'Industrex' C . . 


30 


20 


t 


20 


'Industrex' A . . 


35 


30 


t 


30 


'Industrex' T . . 


95 


t 


t 


70 


'Industrex' M . . 


200 


t 


100 


140 



t Processing under these conditions is not recommended. 
*Under normal processing conditions. 



IN-16 



The following product names appearing 

in this Data Sheet are trade marks 

KODAK 

INDUSTREX 

KODIREX 



Kodak Data Booklet KODAK LIMITED LONDON 

IN-16 

YI252PDIN-l6/xWPI0/4-72 



SCIENTIFIC APPLICATIONS 



CONTENTS EDITION 

SC-I Photo-Elastic Stress Analysis Issue D 

SC-3 Ultra-Violet Photography in Science and Industry Issue D 

SC-4 Ultra-Violet Photomicrography Issue B 

SC-6 Recording Thin-Layer Chromatograms Issue A 

SC-7 Infra-Red Photography Issue D 

SC-8 16 mm Cine-Micrography Issue A 

SC-IO Autoradiography Issue F 

SC-I I Photomacrography Issue C 

SC-12 Photomicrography: Centring and Adjustment of Issue A 
Apparatus 

SC-13 Exposure in Photomicrography Issue 8 

SC-I 5 The Photographic Aspects of X-ray Issue 8 
Crystallography 



Associated Data Sheets in this or other volumes or sections 

The Dimensional Stability of Photographic Films and Plates 

KODAK 'Wratten' Filters for Scientific and Industrial 
Purposes 

Photography Applied to Flow Visualization 

The Photography of High-Speed Events 

Recording Temperature Distribution 

Photography of the Macrostructure of Metals 

Metallography 

Contact Microradiography 

Problems in Colour Photography 

Colour Photography by Artificial Light 

Colour Photography and the Human Eye 

Uniform Development of Scientific Plates 

'Kodak' Scientific Films and Plates 

'Kodak' Photographic Materials for Electron Micrography 

'Kodak' Photosensitive Resists in Industry 



Kodak and Wratten are trade marks KODAK LIMITED 

Printed in England 

Y 1 325PDDB-36/xWP 1 0/5-73 



1, 


RF-10 


1, 


FT-3 


2, 


IN-I 


2, 


IN-2 


2, 


IN-8 


2, 


IN-10 


2, 


IN-II 


2, 


IN-12 


3, 


CL-7 


3, 


CL-8 


3, 


CL-9 


3, 


PR-5 


4, 


SE-3 


4, 


SE-S 


4, 


SE-9 




PHOTO-ELASTIC STRESS ANALYSIS 



Photo-elastic analysis is one of the most effective methods available to the 
engineer for solving problems of stress distribution. In simple cases it 
can be used either alone or as a check on mathematical solutions. 
Reliable information can be obtained on problems which are insoluble 
mathematically, or at least involve complicated and tedious calculations. 
Examples include the stresses round notches and holes in bars, in riveted 
joints, spoked wheels, gear teeth, frameworks with welded joints or 
redundant members, pressed metal work and the stress distribution in the 
threads of bolts and in machine tools while working. More ambitious 
investigations have included pressure vessels, diesel engine frames, steel 
converters, nuclear reactor vessels. 

A scale model is made of the object to be tested, a suitable trans- 
parent material being used. Loads proportional to those acting on the 
actual component to be investigated are applied to the model and, if it is 
viewed in a suitable polariscope with monochromatic polarized light, a 
pattern of light and dark bands is seen that can be recorded photo- 
graphically. Typical patterns obtained are shown in Figure 1. In a model 
made of flat sheet, the stress condition at any point can be denned by the 
magnitude and inclination of the two "principal stresses", and it is then 





Figure I (a). Stress pattern 
obtained in circularly-polar- 
ized light with model loaded 
as shown in Figure 2. The 
isochromatic lines only are 
recorded. 



Figure I (b). Stress pattern 
of the same model as in (a) 
obtained in plane-polarized 
light. Both isochromatic and 
isoclinic lines are recorded. 



Issue D 



Kodak Data Sheet 
SC-I 



possible to determine the stress condition at all points of the model, that 
is its stress distribution, from observed patterns as in Figure 1. 

The stress distribution will be the same in the actual component and 
in the model, regardless of the material of which the model is made, 
provided that only elastic stresses are considered and that the materials of 
the actual component and of the model are homogeneous. The values 
obtained, therefore, apply directly to the actual component constructed of 
steel, concrete or other material. 

Two types of lines are observed, the isochromatic lines or "fringes", 
which are coloured when white light is used and from which the magnitude 
of the difference between the two principal stresses is deduced, and the 
isoclinics, which are always black and which give the inclination of the 
principal stresses relative to the planes of polarization (see Figure 2). 

Optical theory 

The phenomenon depends on the fact that the transparent material of 
which the model is constructed becomes birefringent when it is stressed. 
Plane-polarized light passing into a material of this type is split into two 
components vibrating in the directions of the principal stresses at any 
given point of the model and travelling through the material at different 
velocities (Figure 2). If, after emerging from the model, these two 
components are re-combined by passing the light through an analyser, 
they interfere if they are out of phase and produce the isochromatic lines 
observed. The extent to which the two components are out of phase 
when emerging from any point of a model of given thickness depends on 
their difference in velocity at that point, this in turn depending upon the 
magnitude of the two principal stresses at the point. When the plane of 



RETARDATION 



LIGHT 
SOURCE 




POLARIZER 
Figure 2. 



ANALYSER 

LOADED 
MODEL 

Principle of the plane polariscope. 



SC-I 



the polarized light entering the model coincides with the direction of one 
of the principal stresses, only the component vibrating in the direction of 
that principal stress passes straight through the model and is then 
cut out by the analyser (the plane of polarization of which is at right 
angles to that of the polarizer, i.e., "crossed"). A black isoclinic line or 
region is thus formed. Frequently, it is easier to examine the isochromatic 
lines if the isoclinic lines are removed, and this may be done by using a 
quarter-wave retardation plate on either side of the model, between the 
polarizer and analyser. The light passing through the model is then 
circularly polarized and the isoclinic lines disappear, owing to the non- 
directional character of the circularly polarized light. 

When quantitative results are required, it is normal practice to use 
monochromatic light. With this type of lighting the isochromatic lines 
appear black, and it has been used for the patterns illustrated in Figure 1. 
The isochromatic lines are then so clear that it is possible to record stress 
magnitudes which are sufficiently great to produce lines of the 12th or 
15th order, this order being near the limit of elastic failure of the model. 
With a white light-source, however, the coloured fines become indistinct 
above the 5th or 6th order; nevertheless, white light is most useful for 
quantitative work with small stresses, for distinguishing between the 
isochromatic and isoclinic lines, for counting the line orders correctly, 
and particularly for demonstration work. 

Apparatus 

Schematic diagrams of polariscopes suitable for photographing or 
observing photo-elastic patterns are shown in Figure 3. 

For black-and-white photography of the fringes, and for recording 
high stresses, a monochromatic light-source should be used at L. For 
colour photography with "tungsten" colour films a 3200 K lamp should be 
used, but for 'Kodachrome' II Professional Film (Type A) a photo- 
lamp, 3400 K is required. Green fight from a mercury lamp is com- 
monly used in monochromatic work, a ' Wratten' Filter No. 47 at F cutting 
out unwanted parts of the spectrum. Alternatively, a 'Wratten' Filter 
No. 22 will isolate the yellow band in the mercury spectrum. A sodium 
lamp can be used without a filter. 

The polarizer, P, and analyser, A, which are "crossed" so that no light 
passes through the system when the model is removed or remains 
unstressed, are conveniently made of Polaroid plastic sheet. Nicol prisms 
may be used but since these are only available in small sizes, they must 
be placed outside the lenses where the light beam is of small diameter. 
Any stresses in the lenses will then produce an unevenly illuminated field. 

Q x and Q 2 are the quarter-wave plates, usually made of stressed plastic 
selected for freedom from flaws, which are placed in position when it is 
desired to remove the isoclinic lines. Each must be orientated in the 
correct way, which can be determined by trial. When both are inserted in 
their correct positions the isochromatic fines remain unchanged in position 
and colour but the isoclinic lines vanish. 

The double condenser, C v should be greater in diameter than the height 
of the largest model to be examined unless it is proposed to scan various 

3 SC-I 



L F C, P Q, M 

U M 





Figure 3. Typical polariscopes used for stress analysis. 
(Top) Polariscope with concentrated light-source and lenses, suitable for accurate work 
and for observation on a screen. 

(Bottom) Polariscope with diffuse light-source and without lenses, suitable for large 
models and for direct observation. 

parts of the model in turn. The focal length of this condenser is im- 
material but it must be mounted to produce a parallel beam of light 
through the model, M, to the second condenser, C 2 . This second con- 
denser converges the light, so that it may pass into the camera lens, and 
at the same time acts as a supplementary lens to enable the camera, H, to 
focus on the model at as short a distance as possible. It should have 
about the same focal length as the camera lens and should be mounted 
truly perpendicular to the axis of the polariscope. If these points are 
overlooked, the aberrations introduced will interfere with the quality 
of the photographic record. Alternatively the pattern may be observed 
on a screen, J (usually a ground-glass plate), from which sketches may be 
taken. 

Diffuse-light polariscopes (Figure 3 bottom) are useful for general 
industrial applications where optical accuracy is not of paramount 
importance and where large models are to be observed and scanned. A 

SC-I 4 



large light-source, L (sodium lamps or mercury sources with filter for 
monochromatic light, strip lighting or banks of ordinary tungsten bulbs 
for white light), illuminates a diffuser, D (matt glass plate), which gives 
uniform light over a large area. The light then traverses similar com- 
ponents as in the lens polariscope and the pattern is photographed directly 
at PH. Diffuse light polariscopes are generally cheaper than lens polari- 
scopes, particularly for large sizes above 6 to 8 inches diameter. 

A large viewing field is desirable both for direct examination and for the 
convenience of visual inspection during the setting up of either type of 
polariscope and during the subsequent loading of the model. A 4 x 5 
sheet-film camera is suitable. Provision should be made for considerable 
extension between the lens and the film in order to obtain as large a 
photographic record as possible. Use a lens of the type employed for 
process and copying work. A miniature camera with extension collars 
or bellows may be used, but it is almost essential that the camera permits 
the image to be examined on a screen in order that the pattern may be 
observed while the load is being applied. 

Photo-elastic coating technique 

This technique is used to show surface strain. Unlike the photo-elastic 
model techniques, this technique does not require the construction of a 
complete model, as the coating can be applied directly to parts of an 
existing structure. Coatings can be applied extensively over actual 
structures, almost regardless of shape and size of material, and may often 
be used under the actual operating conditions for the part or structure 
being examined. 

The changes in strain distribution are examined or recorded by reflecting 
polarized light from the surface of a stressed part to which a photo-elastic 
(birefringent) coating has previously been applied. 

LIGHT SOURCE 

y 

STRESSED 
PART, COATED 





PHOTO ELASTIC 
COATING 
(a) (b) 

Figure 4. Photo-elastic Coating Technique. 

(a) Simplified schematic diagram of the optical system. 

(b) At every point, where P and A are parallel to the principal strains in the coating 
a black line is seen. 

(c) Where P and A are not parallel to the principal strains, light is transmitted 
through the analyser and colours are observed in white light. 



SC-I 



Three-dimensional analysis 

When certain materials are stressed at elevated temperatures and very 
slowly cooled while still under stress, the patterns are frozen into the model 
and remain even if it is cut into slices. Appreciable heat must not be 
generated during the slicing. These slices may then be examined in the 
ordinary way to give the stress distribution in selected planes of the 
original three-dimensional model which may be cast in the required shape 
or machined from a block in a suitable material. 

A technique for using light scattered and polarized inside a three- 
dimensional model that need not be heated and sliced has also been 
devised (see Bibliography). 

Materials for stress analysis 

For most work with sheet or castings of moderate thickness, epoxy 
resin, such as Araldite CT 200 with Hardener HT 901 in the ratio of 
100 to 30 by weight, is suitable; for heavy castings use Hardener 907 
instead of 901 and a ratio of 100 to 53. Polyurethane rubber, CR-39 allyl 
diglycol carbonate resin, and other materials are suitable for certain 
techniques. More information can be obtained from the suppliers listed 
in the Appendix and from the Bibliography. 

Photographic materials 

For monochrome work with continuous or line spectrum light-sources, 
KODAK 'Tri-X' Pan Professional Film 4164 (ESTAR Thick Base) and 
KODAK 'Plus-X' Pan Professional Film 4147 (ESTAR Thick Base, are 
recommended; KODAK 'Royal-X' Pan Film 4166 (ESTAR Thick Base) 
can be used when short exposure times are required. If the 546 nm mercury 
line is being used, KODAK 'Tri-X' Ortho Film 4163 (ESTAR Thick Base) 
and Commercial Ortho Film 4180 (ESTAR Thick Base) are recommended, 
as they can be handled under safe-light illumination. For 35 mm work, 
KODAK 'Panatomic-X', 'Plus-X' Pan and 'Tri-X' Pan Films are recom- 
mended. Develop the negatives fully in order to obtain high contrast 
between the lines and the background. Adjust the exposure to give almost 
transparent lines in the negative; the background should then be relatively 
dense. Make the prints on the appropriate contrast grade of white smooth 
glossy 'Kodak' Bromide Paper. 

For records in colour, KODAK 'Ektachrome' Film 61 16, Type B (Process 
E-3), or 35 mm 'Kodachrome' II Professional Film (Type A) is recom- 
mended. The correct exposure may be determined by comparison with 
a known standard negative film, and it is advisable to include one exposure 
on a simple test object, such as a bar under uniform bending moment, 
with each batch of colour film, for comparison purposes. Some plastic 
materials are rather yellowish in colour but if this colour is objectionable 
in a colour photograph it may be partially removed by placing a suitable 
pale-blue filter over the light-source or camera lens during exposure 
(Data Sheet CL-3). 

Analysis of the records obtained 

Photographs may be used to obtain the following information: 

SC-I 6 



1 The quality of the stress distribution over the model from a general 
examination. 

2 The magnitude of the difference between the two principal stresses, at 
any point, from the isochromatic lines. 

3 The magnitude of the tangential principal stresses at any free (unloaded) 
boundary. 

4 The directions of the principal stresses from the isoclinic lines. 

5 The maximum shear stress equal to half the difference between the 
principal stresses. 

In the general examination the isochromatic lines may be regarded as 
contours of the maximum shear stress. Just as crossing the contours of an 
ordinary map indicates going up or down a slope, so crossing the iso- 
chromatic lines indicates moving from a region of low maximum shear 
stress to one of higher maximum shear stress, or vice versa. Where many 
lines are crowded together in one region, whilst next to it the lines are 
widely spaced, it follows that the material is probably not being used to 
carry the applied load in the most economical way. Note however that 
this applies only to the maximum shear stress or to the difference between 
the principal stresses. A region of sparse lines or a region of low fringe 
order does not in itself indicate a lowly stressed region because both 
principal stresses may be high and their difference small. 

However, at a free boundary the principal stress normal to the boundary 
is zero so that at such a boundary the photo-elastic pattern directly indicates 
the maximum existing stress. In Figure 1(a), the stress concentrations 
round the notches are seen. The lines are crowding together at the root 
of the notch and it is here, at the point where the line of highest order 
appears at the boundary, that the component is most highly loaded and 
will eventually fail. The photo-elastic technique is convenient for com- 
paring the effects of slight modifications of the shape of such notches. 
General comparisons of the concentrations of stress in several alternative 
designs may be made without further analysis. The most favourable 
design, giving the lowest value of the highest order at a free boundary, 
may be found for specified conditions. 

At every point on any one isochromatic line, the magnitude of the 
difference between the values of the principal stresses is constant. By 
watching the model as the load is applied it is easy to determine the "order" 
of any line. If attention is focused on a given point, then this point will 
lie in a black region when the model is unloaded (zero order). As load is 
slowly applied, the point will first brighten up, then appear again in a black 
region (first order) and continue to alternate between white and black, 
each consecutive black line passing through the point being one order 
higher than the preceding one. Alternatively, if a point can be found that 
from theoretical considerations remains unstressed or carries equal 
principal stresses under any load (zero order), then the orders can be found 
by counting the black lines from that point, provided care is taken in 
counting in the correct sequence (observation in white light will help in 
counting correctly). The correctly counted orders of the lines are essential 
for any quantitative interpretation, and no photographic record can be 
regarded as complete unless the most important orders have been marked 

7 SC-l 



on it (a line is said to be of the nth order if it is the nth line to have passed 
through the point observed). Each isochromatic line represents a definite 
magnitude of principal stress difference which may be determined by 
loading, under uniform tension, a strip of the same sheet from which the 
model is cut and by noting the stress necessary to produce a change from 
black through white to the next black appearance, as the load is gradually 
increased. For instance, if 1138 kgf/cm 2 (80 lbf per inch 2 ) are needed to 
produce a change from black to the next black appearance in this tension 
test, the principal stress difference along a 4th order line in the model will 
be 1 138 x 4=4552 kgf/cm 2 (320 lbf/in 2 ). The maximum shear stress, S max , 
along this 4th order line in that model will be half the magnitude. 

The principal stress differences also give the maximum stresses at the 
unloaded boundaries of the model, since one of the principal stresses will 
be zero at such a boundary. 

The direction of the principal stresses can be determined from the 
isoclinic lines. The directions stresses are constant along each of these 
lines and are parallel or perpendicular to the direction of the plane of 
polarization of the polarizer. If the polarizer and analyser are rotated 
together and kept crossed at right angles to each other, these lines move 
across the model, and a series of photographs taken at known degrees of 
rotation thus enables the directions of the principal stresses to be deter- 
mined at every point in the model. 

Various techniques are available for determining the sum of the 
principal stresses at any point in the model. In conjunction with the 
differences obtained from the isochromatics, this allows the separate 
magnitudes of the principal stresses to be found all over the model. 
Methods of performing this separation are either by evaluation of the 
isochromatic and isoclinic lines or from the principal stress sum and 
difference described in the Bibliography. 

Acknowledgements 

The revised data in this Data Sheet is in the main due to the help and 
assistance given by Professor M. L. Meyer and Mr. V. F. Bignell of the 
Department of Mechanical Engineering, The City University, London, 
and to Mr. K. Sharpies of Sharpies Photomechanics Limited, and the 
Strain Measurements and Equipment Division of Welwyn Electric 
Limited. 



SC-I 



Bibliography 
Books 

E. G. Coker and L. N. G. Filon, A Treatise on Photoelasticity, 
Cambridge University Press, 1957. 

This fundamental classical work in the English language on theory and 
practice of photoelasticity is important for experts in the art. 

M. M. Frocht, Photoelasticity, Vols. 1 and 2, Wiley, 1948. 

This book is probably the best reference text for those who wish to 
become thoroughly acquainted with all aspects. Its presentation is 
excellent but many advances have been made since its publication. 

H. T. Jessop and F. C. Harris, Photoelasticity; Principles and Methods, 
Cleaver Hume, 1949. 

A condensed and concise but not an easy presentation of the whole 
subject. 

A. W. Hendry, Elements of Experimental Stress Analysis, Pergamon 
Press, 1964. 
An introduction for beginners. 

Durelli and Riley, Introduction to Photomechanics, Prentice Hall, 1965. 
A fairly recent book giving a comprehensive survey on theory and 
practice and including many modern methods. 

R. B. Heywood, Photoelasticity for Designers, Pergamon Press, 1969. 
A book mainly on the practice of photoelasticity as applied to engineer- 
ing, with extensive descriptions of equipment, materials and techniques, 
and with a very comprehensive list of 1134 references up to its date of 
publication. 

A. J. Durelli, Applied Stress Analysis, Prentice Hall, 1967. 

Examples of practical applications to engineering with lessons to be 
drawn from each such application. 

Journals 

Research in photo-elastic stress analysis is still making rapid progress, 
accelerated by the use of laser light-sources. Hence it is necessary to 
consult journals in order to keep up to date. Some important journals 
in this field are : 

Experimental Mechanics, Journal of the Society of Experimental Stress 
Analysis (U.S.A.). 

Journal of Strain Analysis, Institution of Mechanical Engineers, 
London. 

British Journal of Applied Physics, Institute of Physics, London. 

Strain, British Society for Strain Measurement, Newcastle upon Tyne. 

Many other journals devoted to mechanical, aeronautical and structural 
engineering bring articles on photoelasticity. In addition, regular confer- 
ences held on stress analysis and on applied mechanics publish conference 
proceedings with articles on photoelasticity. The list given here is by no 
means comprehensive and is intended only to give an introduction from 
which the reader will be able to find his own way to references of particular 
interest to him. 

9 SC-l 



APPENDIX 

The following list of suppliers in the United Kingdom is intended 
only as a guide, and should not be regarded as comprehensive. 

POLARISCOPES 
Transmission polariscopes 

The Hummel Optical Co. Ltd. 
Norwood Instruments Ltd. 
Sharpies Photomechanics Ltd. 
Tecquipment Ltd. 
Stress Engineering Services Ltd. 

Reflection polariscopes 

Automation Industries U.K. 
Stress Engineering Services Ltd. 

MODEL MATERIALS 

CIBA-GEIGY (U.K.) Ltd. 
Norwood Instruments Ltd. 
Sharpies Photomechanics Ltd. 
Stress Engineering Services Ltd. 

ADDRESSES 

CIBA-GEIGY (U.K.) Ltd., Plastics Division, Duxford, Cambridge 

CB2 4QA 
Norwood Instruments Ltd., New Mill Road, Honley, Nr. Huddersfield 

HD7 2QD 
Sharpies Photomechanics Ltd., Europa Works, Wesley Street, Bamber 

Bridge, Preston PR5 4PB 
Tecquipment Ltd., Hooton Street, Carlton Road, Nottingham NG3 2NJ. 
The Hummel Optical Co. Ltd., 268, High Street, Rochester, Kent. 
Stress Engineering Services Ltd., Sigma Works, The Island, Midsomer 

Norton. 



Kodak and product names quoted thus — 'Wratten' — are trade marks 



KODAK LIMITED 

Kodak Data Sheet „ . . . . c , . 

Printed in England 

$ C_ ' YI320PDSC-l/xWPI2/4-73 




ULTRA-VIOLET PHOTOGRAPHY 
IN SCIENCE AND INDUSTRY 



Ultra-violet radiation is employed in forensic science, in the examination 
of works of art and for several specialised industrial techniques. Many 
materials, appearing similar to the eye, can be distinguished by their 
different fluorescence under ultra-violet rays, and this may be recorded 
photographically. Apart from this, however, all photographic materials 
are sensitive to part of the ultra-violet portion of the spectrum and direct 
records can therefore be made by the use of these rays instead of white 
light; this can be of considerable value in cases where materials which 
have identical reflection and absorption characteristics in white light have 
different characteristics in the ultra-violet. 

LUMINESCENCE 

When certain materials (solids, liquids, or gases) are subjected to short 
wave electromagnetic radiation, they will emit another radiation, of 
longer wavelength and very often in the visible spectrum. The exciting 
radiations may be X-rays, gamma rays, electrons, ultra-violet, or even 
some visible wavelengths. This phenomenon of induced light emission 
is called luminescence and there are two distinct types, known as fluorescence 
and phosphorescence. 

Fluorescence 

If the luminescence ceases within a very short time (10~ s second) 
after the triggering or exciting radiation is removed, the phenomenon is 
called fluorescence. Although fluorescence is commonly produced by 
excitation with ultra-violet light, other radiations can also be used in 
some applications. 

There are many thousands of materials which exhibit the phenomenon 
of fluorescence, and fluorescence photography has numerous applications 
because it will provide information that cannot be obtained by other 
photographic methods. 

The fact that a substance will fluoresce is an important characteristic. 
The particular radiation that triggers fluorescence and the specific 
position of that fluorescence in the visible spectrum can be clues to the 
identity of a substance. Also, contrast between the elements of a material 
can often be produced by fluorescence, even when they appear similar 
otherwise. 

Phosphorescence 

Although fluorescence ceases almost immediately after the triggering 
radiation is removed, there are some substances which continue to emit 
luminescence for some time, even hours, after removal of the triggering 
stimulus. This phenomenon is called phosphorescence and is produced 
in compounds called phosphors. Phosphorescence, like fluorescence, is 
stimulated by many radiations, but in fewer substances. 

Issue D Kodak Data Booklet 

SC-3 



Bioluminescence 

Another phenomenon of general interest, is the emission of light by 
living organisms. It is called bioluminescence, and is created by an oxidative 
reaction of a light-emitting molecule called luciferin. It differs in this 
respect from the previous types of luminescence which are generated by 
electromagnetic radiation stimuli. 

Bioluminescent organisms are more common in a marine environment 
than on land, and are especially abundant in the deep layers of the ocean. 
The simplest organisms that exhibit bioluminescence, however, are 
bacteria, which accounts for the glow observed on decaying fish or meat. 
Certain fungi also exhibit this phenomenon. A common example of 
bioluminescence is that produced by a firefly or glow-worm. 

All the energy emitted in bioluminescence falls within the visible 
spectrum and is usually shown as a blue or blue-green colour. 

Bioluminescence is a special case of chemiluminescence, since light 
emission results from the decay of a molecule brought to the state of 
excitation by a chemical reaction. 

Both bioluminescence and chemiluminescence can be photographed, 
but since the brightness level is quite low, a darkened room or other dark 
environment is necessary. Any external illumination will be brighter 
than either type of luminescence and will predominate the exposure in 
photography. Very fast photographic materials are necessary. 

EXCITATION SOURCES 

The most common radiations used to trigger fluorescence are the long 
ultra-violet wavelengths, and many of the radiation sources used for 
ultra-violet photography or micrography can also be used for fluorescence 
recording. Short and medium wave ultra-violet are sometimes applicable, 
such as in photographing chromatograms or certain minerals. Some 
shorter visible wavelengths are used occasionally to produce fluorescence, 
either at longer visible wavelengths, or in the infra-red. 

Sunlight 

Although it would be possible to use sunlight as a source of ultra- 
violet or visual light to produce fluorescence, it is not a practical procedure. 
Since all light except the triggering radiation must be excluded, a com- 
pletely light-tight enclosure would be necessary. The technique would 
be further complicated because the position of the sun relative to the 
earth is not constant, and because sunlight is a source of variable intensity 
due to atmospheric conditions. Artificial radiation sources are preferable 
because they are constant, easily procurable, and convenient to use. 

Mercury vapour lamps 

Mercury-vapour lamps, both high-pressure and low-pressure, have 
application in fluorescence photography. All mercury-vapour lamps, 
however, emit long-wave ultra-violet, and if the tube is made of quartz, 
then the shorter waves of ultra-violet may also be emitted. 

SC-3 2 



The tubular type of low-pressure mercury-vapour lamp provides an 
efficient source of long- wave ultra-violet for many applications. A lamp 
of this type can be obtained either with integral filter material in the 
glass of the tube, or with tubular filters which fit over, and can be fastened 
to, the tube. The latter technique allows a wider choice in the selection 
of the filter, such as when the exclusion of all visible light is desirable. 
Since tubular lamps are often available in different lengths, one or more 
can be selected to suit the size of the subject. Some firms also supply 
these lamps mounted in suitable reflectors. 





65 


































435 

1 












31 


2 


4 


1 




546 






| 


3 


!4 


































' 


V 


k- 


V. 


\)\ 













WAVELENGTH (nm) 

Figure I. Spectral emission lines of high-pressure mercury arc. 

A high-pressure mercury arc lamp emits a high output of long-wave 
ultra-violet with a corresponding result of intense fluorescence, particularly 
in subjects of small area. These lamps require transformers to provide the 
high voltage necessary for operation. A source of this type can be obtained 
either as a clear, quartz capillary tube or enveloped by a special filter glass 
which transmits ultra-violet and absorbs all, or most, of the visible light. 

Electronic Flash 

Electronic flash lamps are suitable for ultra-violet photography since they 
emit long-wave ultra-violet. They can also be used for recording fluores- 
cence, triggered by ultra-violet, in close-up applications such as photo- 
graphing dermatological conditions or fingerprints dusted with fluorescent 
powder. A flash-tube with high intensity output should be obtained for 
this purpose. One of the difficulties encountered in using electronic flash is 
that resulting fluorescence is not visible during the short flash interval. 
A continuous ultra-violet source is often necessary for preliminary 
inspection to ascertain the presence of fluorescence. 



SC-3 



Illumination 

One of the main factors influencing the brightness of fluorescence is 
the intensity of the exciting radiation. Fluorescence brightness is 
generally of very low order compared with image brightness in other 
types of photography. It is important, therefore, that the radiation 
source be as close to the subject as possible, while giving even illumina- 
tion over the area to be photographed. Ensure, however, that no direct 
light from the source is "seen" by the camera. The illumination of 
the subject should consist only of the radiation needed to trigger 
fluorescence. All ambient illumination (room lights) and all other 
illumination from the source must be excluded from the subject. Fluore- 
scence photography is most often accomplished either in a darkened 
room or in a light-tight enclosure. 



RADIATION 
•--\ SOURCE 

n s' \ (EMITS UV) 




Figure 2. Typical set-up for fluorescence photography using ultra-violet exitation. 



FILTERS 

At least two distinct types of filters are used in a fluorescence photo- 
graphy system. The first, called a transmitting filter, is placed between 
the subject and the radiation source. The second, an absorbing filter, is 
placed in front of the camera lens (or somewhere behind the objective lens 
in a microscope). 

Other filters, such as colour compensating filters, may be used occasion- 
ally along with the absorbing filter for special effects, particularly when 
colour films are to be exposed. 



Transmitting filter 

The filter used with the radiation source is called a transmitting filter, 
and its purpose is to transmit the triggering radiation efficiently and absorb 
all, or almost all, of the other radiations emitted from the source. When 



SC-3 



ultra-violet is the radiation used to trigger fluorescence, the transmitting 
filter should pass a high percentage of the ultra-violet radiated from the 
source. 

Fluorescence brightness, as previously stated, is usually of low intensity, 
and if any other than the exciting fluorescence radiations almost certainly 
are incident on the subject, they will be higher in brightness and may 
mask the fluorescence. A typical filter for this purpose is one such as 
Wood's Glass (available from Chance Pilkington Optical Works, Pilkington 
Bros. Ltd., Glascold Road, St. Asaph, Flintshire, as glass No. 0X1). 

Some ultra-violet sources intended for fluorescence work include 
exciter filters, either incorporated as a colouring agent in the glass en- 
velope or attached to the reflector or the lamphouse. This filter must be 
used, even when some visible blue light is transmitted. If the illuminator 
is not equipped with a filter, however, then a more efficient one can be 
selected. For example, if a high-pressure mercury arc is used to provide 
long-wave ultra-violet, either a Kodak 'Wratten' Filter No. 18A or 
Corning Glass No. 5840 (Filter No. CS 7-60), mounted in front of the 
source, will screen out all radiations except the long-wave ultra-violet. 
These filters have very similar transmission, passing about 70 per cent 
of incident ultra-violet at 365 nm. Similar filters are also available from 
other firms. 

Some fluorescence applications require the use of short-wave ultra- 
violet. Certain minerals, for example, will fluoresce only with short-wave 
excitation. The identification of certain materials by fluorescence in 
chromatography requires short ultra-violet irradiation. The exciter 
filter must transmit the necessary short radiations in order to produce 
the desired fluorescence. Corning Glass No. 9863 (Filter No. CS 7-54) 
transmits ultra-violet in the long, medium and short-wave regions. This 
glass filter can be placed in front of the radiation source as a transmission 
filter. It has a high percentage transmission of all ultra-violet, down to 
260 nm, and about 40 per cent transmission at 254 nm. The source must 
necessarily provide these short radiations. 

Barrier filter 

The transmission filter in front of the light-source transmits the radiation 
necessary to excite fluorescence. Not all this radiation is used, however, 
and some residual radiation still exists— reflected from, or transmitted 
through, the subject. If this residual radiation is not removed, it will 
record on film. Since it is usually of higher brightness than the fluore- 
scence, it will cause more exposure than the fluorescence. Another 
filter must be used, usually in front of the camera lens, to prevent the 
residual exciting radiation from causing exposure. This filter absorbs 
the exciting radiation, and is logically called an absorbing filter. An 
efficient absorbing filter absorbs all radiation transmitted by the trans- 
mitting filter, and transmits only the wavelengths of visible light evident 
as fluorescence. If ultra-violet is used to excite fluorescence, then the 
absorbing filter must absorb ultra-violet. If the transmitting filter passes 
both ultra-violet and some short visual blue, then the absorbing filter 
must absorb both ultra-violet and blue. 

c SC-3 



The selection of the absorbing filter also can depend upon the fluores- 
cence wavelengths produced. If blue fluorescence is achieved in the 
subject, the absorbing filter should transmit this blue light. This situation 
can present a problem if the wavelength of the blue fluorescence is the same 
as, or similar to, the wavelength of the blue light transmitted by the 
transmitting filter. The only solution is to substitute a transmitting filter 
which has no blue transmittance. If, however, the exciter filter transmits 
blue up to about 420 nm and blue fluorescence occurs at a longer wave- 
length in the blue, then an absorbing filter— pale yellow — is necessary 
to absorb all wavelengths below about 425 nm and to transmit all longer 
wavelengths. If no blue fluorescence occurs, then the problem is simplified. 
Any yellow filter which absorbs ultra-violet can be used, as long as the 
fluorescence wavelengths are transmitted. 

Another problem which can occur, however, is fluorescence of the 
absorbing filter itself. The colouring material in the filter may show a 
bright fluorescence when irradiated with ultra-violet. Some yellow filters 
exhibit this effect. The result can be a "fogging" of the film; the desired 
fluorescence record may be degraded and can appear hazy. There are 
two possible solutions to this problem: (1) A filter which absorbs only 
ultra-violet— such as a Kodak 'Wratten' Filter No. 2B or 2A— can be 
placed in front of the absorbing filter to prevent its fluorescence. 
(2) Another absorbing filter can be selected, one which does not fluoresce 
but has similar absorption. The possible fluorescence of a proposed 
absorbing filter can be determined beforehand by holding it in the beam of 
a filtered source which emits ultra-violet light. If the filter does fluoresce, 
it will appear to glow. 

It is quite possible, however, to examine the transmission curve for 
the intended transmitting filter and to select an efficient absorbing filter 
from the transmission-absorption curves for all possible absorbing filters. 

If no blue fluorescence occurs, or if it occurs but its record is not wanted, 
the absorbing filter can be one which has complete absorption of blue and 
ultra-violet. Kodak 'Wratten' Filters No. 12 (often called a "minus 
blue" filter) and No. 15 are efficient blue and ultra-violet absorbers. 
They transmit green, yellow, orange, and red freely. If these are the 
only colours produced as fluorescence, then the filter can be a complete 
blue absorber. If some desired blue fluorescence occurs, however, the 
selection of a filter is more exacting. The spectrophotometric curves in 
the "Kodak Filter Book" for niters 2B, 2A, 2E, 3, 4, 8(K2), 9, 12 and 
15(G) show the transmittance and absorption of 'Kodak' Filters suggested 
as possible absorbing filters. They all absorb ultra-violet but differ in 
regard to blue absorption. If the transmitting filter transmits ultra-violet 
only, Kodak 'Wratten' Filter No. 2A, an efficient absorbing filter, is 
often adequate. The Kodak 'Wratten' Filter No. 87 is an efficient 
absorbing filter for recording infra-red luminescence on infra-red sensitive 
film. It transmits infra-red and absorbs all visible wavelengths. 

COLOUR FILMS 

All photographic emulsions are inherently sensitive to blue and ultra- 
violet. This is why all blue and ultra-violet transmitted by the transmitting 

SC-3 ,- 



filter must be absorbed by the barrier filter. Otherwise, the film will 
be exposed to these radiations, which may cause greater photographic 
effect than the fluorescence. If a colour film is used, any ultra-violet 
reaching the film will record as blue, seriously degrading the record of 
fluorescence colours. Similarly, any unwanted blue light passing through 
the absorbing filter will degrade the fluorescence record. 

Colour film, of course, presents the greatest advantage in recording 
fluorescence colours. Daylight-type colour film is especially recom- 
mended because of its balanced sensitivity to the blue, green, and red 
regions of the visible spectrum. Colour film balanced for tungsten 
illumination is seldom recommended, since it has higher blue sensitivity 
than the daylight type. It could, however, be used efficiently for record- 
ing blue fluorescence. 

Since fluorescence colours are usually of low brightness, a high-speed 
colour film is especially recommended in order to minimize exposure 
time. When a 35 mm film is needed, Kodak High Speed 'Ektachrome' 
Film, Daylight Type, is suggested. It is possible, however, that some 
fluorescence colours will record more efficiently on another, slower film. 
In this case, a longer exposure time may be tolerated if the record on 
colour film has better fidelity. 'Kodachrome-X,' Kodak 'Ektachrome-X' 
and 'Kodachrome IP Film (all colour reversal films balanced for day- 
light) are suggested for fluorescence photography if the high-speed film 
does not record a specific fluorescence colour satisfactorily. If a colour 
reversal film in sheet size is desirable, Kodak 'Ektachrome' Film, Day- 
light Type, is recommended. This film is not processed by Kodak 
laboratories. It must be processed either by the user or by a local 
laboratory. 

'Kodacolor-X' Film and 'Ektacolor' Professional Film 6102, Type L, 
can also be used in fluorescence photography. Colour negatives are 
obtained by exposure on these films. Although daylight-type exposure 
conditions are normally recommended for this film, it is not a daylight- 
type film. It is balanced for a colour temperature of 3800 K, and therefore 
has higher blue sensitivity than a true daylight film. Its blue sensitivity 
can be subdued in fluorescence photography either by a barrier filter 
with sufficient blue absorption or by a yellow colour-compensating filter 
along with the barrier filter. The exact filter for this purpose must be 
determined by test exposures. 

Roll colour films, especially in 35 mm size, are usually recommended 
for recording fluorescence because they have the highest speeds, are more 
readily available, are less expensive, and are more conveniently handled 
and processed than sheet colour films. 

MONOCHROME FILMS 

When using the normal fluorescence method, it is recommended that a 
panchromatic film be used, so that the fluorescent radiations of all 
colours can be recorded. Orthochromatic films, however, may be 
used satisfactorily when the colour of the fluorescence is blue or green. 

One of the problems encountered in using black-and-white film is that 
all colours are recorded as grey tones. If differentiation is necessary, a 

7 SC-3 



filter can be used with the absorbing filter. For example, two fluorescence 
colours, red and green, may be evident in a subject. If the colours have 
equal or similar brightness, they may record as grey tones of the same 
density; one could not be distinguished from the other. If a pale-green 
filter were used with the absorbing filter, however, the green fluorescence 
colour would be transmitted freely and the red partially absorbed. Con- 
trast would then be achieved between the fluorescence colours in the 
photographic record. If the two colours differ in regard to fluorescence 
brightness, the extra filter may not be necessary. If the difference in 
brightness is considerable, however, a filter may be necessary to partially 
absorb the colour of highest brightness. 

SUITABLE MATERIALS 

The following table lists some of the films suitable for ultra-violet 
fluorescence, together with their Data Sheet numbers, for further details. 
Because of the comparatively low inherent contrast of most fluorescent 
radiations, it is recommended, for monochrome films, that development be 
extended to 50 per cent more than that considered satisfactory in normal 
photography. 



'KODAK' FILMS 



DATA 

SHEET 

NUMBER 



Sheet films 

'Royal-X' Pan 4166 

'Plus-X' Pan Professional 

'Tri-X' Ortho4l63 

Commercial Ortho 4180 

'Ektachrome', Daylight Type (Process E-3) 

'Ektachrome', Type B (Process E-3) 

'Ektacolor' Professional, Type L 

Roll films 

'Royal-X' Pan 

'Plus-X' Pan Professional 

High-Speed 'Ektachrome', Daylight Type ... 

High-Speed 'Ektachrome', Type B 

'Ektachrome' Professional, Daylight Type (Process E-3) 

Miniature films 

2475 Recording ('Estar-AH' Base) 

Tri-X' Pan 

'Plus-X' Pan 

High-Speed 'Ektachrome', Daylight Type ... 

High-Speed 'Ektachrome', Type B 

'Kodachrome' II, for Daylight 

'Kodachrome' II Professional, Type A 



FM-44 
FM-36 
FM-35 
FM-34 
FM-ID 
FM-ID 
FM-3 



FM-50 
FM-48 
FM-IB 
FM-IB 
FM-ID 



FM-5S 
FM-53 
FM-S2 
FM-IB 
FM-IB 
FM-2A 
FM-2A 



EXPOSURE DETERMINATION 

Because of the very low brightness of fluorescence, the most practical 
method of determining exposure is by test. The beginner should make 
several exposures, increasing time, at a constant lens aperture, by a factor 
of 2, in successive steps, over a wide range. Lens apertures could also be 



SC-3 



varied by using a constant time, but this technique would cause a variation 
in depth of field that might not be desirable. Once the exposure time has 
been determined, however, the lens aperture can be changed to achieve 
the appropriate depth of field. As in all other photography, if lens 
aperture is changed, exposure time must be changed in inverse proportion. 
When a constant source, such as a mercury arc lamp, is used, exposure 
time will be several seconds, or even minutes if the fluorescence is ex- 
tremely low in brightness. Extremely long exposures result when large 
subjects are to be photographed and illumination is spread over a large 
area. Extremely long exposures can also result when image size is greater 
than object size, as in photomacrography. 

It is seldom possible to use an ordinary exposure meter to read fluores- 
cence brightness, but an extremely sensitive meter can be used. If one 
is available, its cell should be protected with a barrier filter which absorbs 
ultra-violet. Otherwise, the meter will indicate ultra-violet rather than 
fluorescence brightness. Ultra-violet reflected from, or transmitted 
through, the subject will be much higher in brightness than fluorescence, 
so an erroneous indication of exposure time will be obtained. 

When electronic flash is to be used (as in close-up fluorescence photo- 
graphy), an experimental guide number can be determined for a specific 
subject, flash unit, and film. If the subject is changed, however, the 
guide number might or might not apply, since fluorescence brightness 
might change. In this case, exposures should be bracketed. Exposure 
time will be constant, so changing the lens aperture is the only practical 
means of varying exposure. 

No matter how exposure is determined, it is a good idea to make a 
record of all exposure conditions for future reference. These conditions 
include the subject, the radiation source, the exciter filter, the barrier 
filter, the position of the source, the film, the exposure time and lens 
aperture, and any other details pertinent to fluorescence photography. 

Reciprocity effect 

When exposure time becomes excessively long because of very low 
levels of subject brightness, a loss in film speed occurs. This is called 
the reciprocity effect, or failure of the law of reciprocity. Exposure 
in photography is normally equal to the product of intensity and time 
(E=It). Under normal conditions of subject brightness, as in outdoor 
photography, exposure times are reasonably short (1/25 second, 1/50 
second, 1/100 second, etc.). As brightness decreases, exposure times 
must be decreased proportionally. Throughout a normal subject 
brightness range, the reciprocal relationship of E=It holds true, but 
when brightness is extremely low or high, it does not. 

In fluorescence photography, long exposure times of several seconds, 
or even minutes, are not uncommon, because of very low fluorescence 
brightness. Effective film speed is usually much lower than the rated 
speed, which is derived for normal conditions. When monochrome 
film is used, an increase in exposure time is necessary to compensate for 
the lesser effective film speed. This is no problem, since fluorescence 
colours are only recorded as grey tones. In fluorescence photography 

o SC-3 



with colour films, however, the problem is more acute. A colour-reversal 
film contains three emulsion layers. The reciprocity characteristics of 
one layer can be different than the other two, and all three can be different 
from each other. The result is a speed loss, which can vary with each 
layer of emulsion. If the speed loss is not the same in all three layers, 
a change in colour balance occurs. 

With most colour-reversal films a noticeable colour shift occurs when 
exposure time is 1 second or longer. The effect can be compensated 
to a large degree, however, with appropriate 'Kodak' Colour Compensating 
Filters. 

The filter for compensation of reciprocity effect, however, may differ 
in fluorescence photography because this is not normal use of colour film. 
It is possible that more colour shift might occur, and a different filter 
might be more appropriate. The exact filter usually would have to be 
determined by test exposures. The length of exposure time and the 
particular colour, or colours, to be reproduced must be taken into con- 
sideration in such test exposures. 

Focus 

When fluorescence occurs in the visible spectrum there is no problem 
involved in obtaining correct focus. It can be achieved by a distance 
setting on the camera, by means of a rangefinder, or by adjustment on 
a ground glass screen (as in a view-camera). 

Recording infra-red luminescence, however, involves an invisible 
image, and lens focal length is longer for infra-red than for visible light. 
The use of a small lens aperture is a practical means of obtaining correct 
focus. Focus the lens using visible light; set the aperture to at least two 
stops below fully open, place the transmitting filter in front of the lens 
and make the first trial exposure. The exact lens aperture would be 
determined by the depth of field necessary to record a satisfactory image. 

APPLICATIONS 

An important application of this method to industry is a specialised 
technique which is used to record cracks and porosity of metals. The 
specimen under examination is bathed in a solution of highly fluorescent 
material dissolved in a volatile solvent. This solution creeps into the 
cracks or areas of porosity, the solvent evaporates, and the fluorescent 
material is left. The metal is then washed in the solvent alone to remove 
the fluorescent material from the external areas and is photographed by the 
fluorescence method. In addition, a little ordinary white light may be 
used to illuminate the whole subject; the object of this is to record, in 
relation to the specimen, the position of the crack, or the area of porosity 
(Figure 3). 

Another application is in testing the efficiency of methods of de-oiling 
or de-greasing machine parts (Figure 4) and in detecting the presence of 
oils on fabrics. As most oils and greases fluoresce strongly in ultra-violet 
radiation, their presence may easily be detected. A little white light may 
also be used here, as above, to position the areas under examination. 



SC-3 



10 







Courtesy Colloidal Research Laboratories Ltd. 

Figure 3. Fluorescence photograph showing fine grinding 
cracks on the centre boss of a sintered carbide cutter. 

Other uses include the examination of samples of insulating materials 
which have been subjected to life tests. Any deteriorated areas and the 
presence of certain contaminants, invisible to white light, may be revealed. 
Fluorescent testing is being increasingly used for the identification of raw 
materials, particularly those of an organic nature, and for the quality 
control of ore separation techniques. 




Courtesy De Havilland Aircraft Co., Ltd. 

Figure 4. Photograph of the fluorescence produced by ultra-violet radiation in 

the grease remaining on the surface of a series of samples of sheet metal after 

degreasing treatment. 

Often it is the comparison between a subject illuminated by one light- 
source and when illuminated by another which yields the most data. 

1 1 SCO 



An example of a photograph taken by normal tungsten lighting (a) and 
ultra-violet fluorescence (b) is given in Figure 5. This particular example 
depicts a capping material attached to a section of human tooth. It 
shows not only differences in rendering, thus making visible the clumping 
of certain elements within the material, but the change from a sharp line 
to an unsharp line at the join of the two materials. This shows that 
some molecules of the capping material have migrated into the tooth 
section, thus illustrating that a proper bond has been achieved. 




Crozvn Copyright Reserved 

Figure 5a. Tooth section by normal Figure 5b. Tooth section by ultra-violet 
tungsten lighting. radiation exited fluorescence. 

DIRECT RECORDING OF ULTRA-VIOLET 

The main purpose of ultra-violet photography is to provide information 
about an object or material which cannot be obtained by other photo- 
graphic methods. Obviously, if differentiation between two substances 
is produced in photography with visible light or infra-red radiation, there 
is little need to resort to ultra-violet photography. If these methods fail, 
however, there is always the possibility that ultra-violet photography 
might succeed. In many cases, it is worth a try. 

Direct ultra-violet photography is accomplished by reflected radiation, 
and depends upon the premise that two (or more) elements of an object 
will reflect or absorb ultra-violet to different degrees. 

Some materials will absorb ultra-violet, while others will reflect these 
radiations. Some have partial absorption and partial reflection. These 
effects can be recorded photographically. 



SC-3 



If it is desired to take photographs by ultra-violet radiation alone 
in order to record invisible writing and other subjects which depend upon 
differences in reflectivity under ultra-violet illumination, it is necessary 
to use an ultra-violet transmitting filter over the lens of the camera. 
However, if such a filter is used instead over a light-source which emits 
other than ultra-violet radiation or if no filter is used (as in the case of a 
light-source emitting only ultra-violet), then both reflected ultra-violet 
and fluorescence will be recorded. This result can differ markedly from 
that obtained by the use of ultra-violet alone, and a combination or 
comparison of these techniques may produce a more informative photo- 
graph. 

No filter to prevent ultra-violet radiation entering the lens must be used. 
Ordinary optical glass does not transmit radiation much below 350 nm 
and if shorter wavelengths are to be used quartz must be employed instead 
for lenses and filters. However, much useful work can be carried out by 
using the region 350 to 400 nm which is transmitted by glass, and is 
emitted strongly by the ultra-violet sources mentioned below. Under 
these conditions, any standard type of camera equipment is suitable, 
though a lens should be chosen which does not appear yellowish when 
held against a white background. 

A most suitable and convenient light-source is a lamp of the mercury- 
vapour type, which requires little or no attention, and radiates the 365 nm 
mercury line strongly. Another possible source is the closed carbon arc 
lamp which emits radiations of 350 to 400 nm, but this requires more 
attention. Ordinary electric lamps radiate very little ultra-violet, whilst 
even sunlight contains so small a proportion as to render its use impractic- 
able. 

For use over the lens, the 'Wratten' Filter No. 18A (see Data Sheet 
FT-9) is recommended. The transmission band of this filter in the ultra- 
violet region extends from 285 to 395 nm, and although it transmits 
also in the infra-red region this need not concern those who use it with 
the recommended materials, which are insensitive to infra-red. Where the 
light-sources are to be screened instead of the lens, Wood's Glass will prove 
suitable. Filters for medium wave and short wave ultra-violet transmittance 
are usually of the interference type — that is, evaporative coatings of suitable 
materials on an appropriate substrate (transmitting medium). 

The most suitable material to use for photography in the 350-400 nm 
region is a high-contrast material, such as Process Sheet Film ('Estar' 
Thick Base) (Data Sheet FM-33). When it is desired to record wavelengths 
down to 210 nm, the 'Kodak' Spectrum Analysis Plate, No. 1, is recom- 
mended. If it is required to use wavelength shorter than 210 nm, special 
sensitizers are available — see Data Booklet SE-3. 'Kodak' SWR (Short 
Wave Radiation) Plates and ultra-violet sensitive Spectroscopic Plates are 
recommended for use in the ultra-violet region for wavelength less than 
220 nm. Lines down to 7.5 nm have been recorded on SWR Plates. 
This point is made to show that the optics are the limiting factor not 
the range of sensitized materials. 



13 SC-3 



Product names quoted thus 

'KODAK' 

are trade marks 



Kodak Data Booklet 
SC-3 



KODAK LIMITED LONDON 

Y 1 237PDSC-3/X WP 1 0/4-72 



ULTRA-VIOLET PHOTOMICROGRAPHY 



The primary use of ultra-violet radiation in photomicrography is to give 
finer resolution of detail, but there are a number of other important appli- 
cations including the elimination of artifacts in the photography of living 
cells, the optical sectioning of materials and the differentiation of structure 
by fluorescence. 

The use of short-wavelength ultra-violet radiation enables photomicro- 
graphs to be taken in which resolution is about twice as great as with the 
shortest wavelength used for visual purposes. This has been applied to 
the study of structure of certain biological specimens, some colloidal 
particles, the nature of pigments and fillers and the mechanism of filtration 
and adsorption. 

Many organic substances absorb ultra-violet rays while appearing quite 
transparent to the eye. Thus structure may be brought out without 
staining the specimen. Living matter has been studied in this way since 
most cells are comparatively unaffected by exposure to radiations of 
wavelength 275-257 nm. Ultra-violet rays will induce fluorescence in 
practically all unpigmented animal and plant cells and tissues and many 
mineralogical specimens, thus enabling unprepared specimens to be photo- 
graphed on 'Ektachrome' or 'Kodachrome' colour films with the produc- 
tion of pronounced colour differentiation. These two methods have made 
possible the production of photographs of living tissues which cannot 
otherwise be studied because their structure is not visible to the eye. 

As the depth of field with ultra-violet radiation is extremely small, it is 
possible to focus on any selected plane in the specimen, and thus "optical 
sections" may be taken. Sections on planes approximately 60 nm apart 
are possible. 

Apparatus and materials 

One of the principal functions of the optical microscope is to resolve the 
fine detail which may occur in a specimen. The resolving power of an 
optical microscope varies with the wavelength of radiation employed in 
forming the image; the shorter the wavelength, the greater will be the 
resolving power. Conventional glass optics will transmit radiation down 
to about 320 nm. Either quartz optics or reflecting (catadioptric) optics 
must be employed to allow the use of shorter wavelengths — down to about 
254 nm, if an even higher resolving power is required. 

The following table shows the relationship between wavelength and the 
resolving power of the optical system. Values of resolving power (RP) 

have been calculated from the formula RP= — ^ — '- where the resolving 

K 
power RP is in micrometres ([J.m), X is the wavelength of the incident 
radiation (also in ^.m), and N.A. is the numerical aperture of the objective 
lens. For the particular values quoted, the N.A. is taken to be 1 .30, which 
is typical for a high-magnification, oil-immersion, apochromatic, objective 
lens. 

Issue B Kodak Data Sheet 

SC-4 



Wavelength * ((im) 


0.546 


0.435 


0.365 


0.254 


Resolving Power (|j.m) 


0.21 


0.17 


0.14 


0.1 Of 



* Wavelengths indicated are the predominant lines of the mercury-vapour spectrum. Figures are given 
in micrometres (u.m) as these are equal to the previously preferred and widely used term micron ([x). 
One micrometre equals 10-6 metres and is easily converted to nanometres (nm), the term in which 
radiation wavelengths are now normally given, as I nm equals IO -9 metres. 

t A resolving power of 0.10 fxm is equivalent to 5000 lines per mm. These figures apply only to the opti- 
cal system and will be further modified by the choice of recording material and process used. 

Recommended materials 

Image contrast decreases as the wavelength used becomes shorter. It is 
advised, therefore, that a higher contrast film be used for ultra-violet work 
than is recommended for use with visible light. Kodak 'Plus-X' Pan Film 
is recommended for visible light photomicrography but the films in the 
following table will give a more acceptable contrast with ultra-violet. 
Where wavelengths shorter than 220 nm are to be recorded, 'Kodak' SWR 
(Short Wave Radiation) Plates and Films or 'Kodak' Spectroscopic Plates 
should be used — see Data Booklet SE-3. 

The developing times are for dish development at 20°C (68°F), with 
continuous agitation. The safelight recommended for all these films is the 
'Kodak' Safelight Filter No. 0B. 



FILM 




DEVELOPER* 
& DILUTION 


TIME IN 
MINUTES 


CONTRAST! 
INDEX 


Sheet Film 










'Kodalith' Contact 2571 
('Estar' Base) 


{ 


D-163 (1+3) 
DPC (1+9) 


2± 
21-3 


3.3 
3.2-3.3 


'Kodaline' Standard 2698 
('Estar' Base)— Data Sheet FM-31 


i 


D-163 (l + l) 
DPC (1+4) 
D-163 (1+3) 
DPC (1+9) 


If 3 
If 3 
2f3 
2f3 


2.1-2.4 

2.3 
1 .8-2. 1 

2.0 


'Kodak' Process 4181 / 
('Estar' Thick Base)— Data Sheet FM-33 \ 


DPC (1+9) 
D-163 (1+3) 


2f3 
2f3 


1.4 
1.3-1.4 


35 mm Films 

'Kodak' Fine Grain Positive — 
Data Sheet FM-36 


{ 


D-163 (l + l) 
D-163 (1+3) 
DPC (1+4) 
DPC (1+9) 


If 3 

2± 

If 3 

2f3 


1.4-1.5 
1.4 
1.3 
1.3 



* Developers. 

'Kodak' D-163 Developer (liquid or powder). 

'Kodak' DPC Developer (liquid). 

A wide range of contrast is available by selecting the optimum film/developer/dilution combination. 

t Contrast Index — See Data Sheet SE-IA 

Illumination 

High-pressure mercury-vapour lamps are efficient ultra-violet light- 
sources and are used extensively in the study of fluorescence phenomena 
and in ultra-violet photomicrography. 

Ultra-violet iluminators containing mercury-vapour lamps are available 
from most microscope manufacturers. These illuminators emit very 
bright line spectra — see figure on page 3 — and can be regarded as excellent 
sources of monochromatic radiation when the appropriate line (in either 
the visible or ultra-violet regions) is isolated by using the correct 



SC-4 



Kodak ' Wratten' Filter. Details of 'Wratten' Filters can be found in the 
FT section of the Data Book or in the 'Kodak' Publication "Kodak 
Wratten Filters". 

High-pressure mercury-vapour lamps consist of small, tubular, quartz 
envelopes, in which mercury vapour is produced under a pressure of 
several atmospheres. These lamps require high electrical current and, 
normally, a special transformer for operation; a warm-up period of several 
minutes is necessary to achieve maximum brightness. 

They emit useful quantities of the middle and short-wave ultra-violet 
regions and have a considerable output of long-wave ultra-violet radiation. 
Mercury-vapour lamps are particularly advantageous for illuminating 
reasonably small areas with a high intensity of radiation. Special mercury 
vapour lamps of this type, and of high wattage, are of particular interest in 
both ultra-violet photomicrography and ultra-violet spectrography. 

The xenon arc is another source of ultra-violet radiation. It is a high- 
pressure device which produces a continuous source of radiation from 
200 nm to the infra-red, giving a spectral energy distribution close to that 
of sunlight. 




500 
WAVELEKGTH (nm) 

Spectral emission lines of high-pressure mercury arc. 



To make a long-wave ultra-violet micrograph, the microscope and 
illuminator are set up and adjusted for Kohler illumination with visible 
light. Apochromatic objectives are recommended. The image is 
focused either on the ground glass of the camera or through a beam- 
splitter device. Monochromatic green or blue light may be used, with a 
narrow transmitting filter in the illumination beam. A 'Wratten' Filter 
No. 77 or 77A will freely transmit the green at 546 nanometres; if the 
435 nm blue of the mercury spectrum is to be used, the correct filter is a 



SC-4 



'Wratten' Filter No. 47 or 47B. When the image is sharply focused, the 
setting of the fine focus adjustment on the microscope is noted. (This 
adjustment is usually calibrated.) 

An ultra-violet transmitting filter, such as the 'Wratten' Filter No. 18A, 
is then substituted for the visible-light filter. Next, the focus position is 
changed on the fine-focus adjustment by the amount determined by a 
previous trial, and the exposure is made with ultra-violet. Both focus and 
exposure tests should be made beforehand. The direction of focus change 
will depend upon whether the microscope stage position or objective posi- 
tion is moved for focusing. This condition varies with different types of 
microscopes. The amount of focus change depends upon the focal length 
(or magnifying power) of the objective. 

The use of ultra-violet micrography is also of value in showing differ- 
ences in structure by selective absorption of ultra-violet radiation in the 
various elements of an unstained micro-specimen. Sharper images of 
stained specimens may also be obtained with ultra-violet than with visible 
light — provided, of course, that the stains exhibit differential absorption of 
ultra-violet, so that some contrast will result. The transparency of stains 
varies considerably under ultra-violet. Some stains transmit this radia- 
tion freely, some have partial absorption, and some show a marked absorp- 
tion of ultra-violet. The absorption of ultra-violet by various stains also 
varies with radiation wavelength. Much higher absorption is achieved 
with short-wave ultra-violet radiation than with long-wave. 



Bibliography 

R. M. Allen, Photomicrography, 2nd edition, D. Van Nostrand, 1958. 

Current Topics : Ultrascope, New Aid to Medical and Industrial Research, 
J. Franklin Inst., 267, April 1959, p. 316. 

D. F. Lawson, The Technique of Photomicrography, George Newnes, 1960. 

J. Bergner, E. Gelbke, W. Mehliss, Practical Photomicrography, Focal 
Press, 1966. 

L. E. Janicek, G. Svichla, Ultraviolet Micrography in Biological Research, 
J. Biol, Photogr. Assoc, 36, No. 2, May 1968, pp. 59-66. 

R. P. Loveland, Photomicrography, Wiley, 1970. 



Kodak and product names quoted thus — 'Kodachrome' — are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

PDSC-4/axWPI 1/2-71 



RECORDING THIN-LAYER CHROMATOGRAMS 



Thin-Layer chromatography, using such materials as Eastman 'Chroma- 
gram' Sheet, has become a valuable and widely adopted method in 
chemical analysis. Photographic recording of the chromatograms is 
desirable for several reasons: 

1 Colour changes may occur during storage owing to the instability or 
decomposition of the components of the mixture being separated. 

2 Descriptions of the colours of the chromatogram spots are subjective 
and may vary from observer to observer. 

3 The chromatogram spots may only be visible when viewed by ultra- 
violet radiation, either owing to their reflectance of this radiation or 
because it excites them to fluoresce. Alternatively, the spots may only 
be detectable if the components of the mixture have been "labelled" 
radioactively. 

4 Copies of the chromatogram may be required for inclusion in reports. 

5 Storing original glass chromatograms in notebooks or laboratory records 
is inconvenient and risks damaging the chromatogram. This factor is less 
significant when using 'Chromagram' Sheet which is a pre-coated flexible 
material for thin-layer chromatography. 

This Data Sheet is intended as a brief guide to the application of various 
photographic techniques to different types of specimen. 

COLOUR PHOTOGRAPHY 

This offers wide scope for recording chromatograms owing to its 

ability to reproduce the actual colours involved. The following 'Kodak' 

materials are suitable; general technical data on them may be found in 

their respective Data Sheets, the numbers of which are given in brackets : 

High-Speed 'Ektachrome' Films, Daylight Type and Type B (FM-1B) 

'Ektachrome' Films, Daylight Type and Type B — Process E-3 (FM-1D) 

'Ektachrome-X' Film, Daylight Type (FM-1E) 

'Kodachrome' II Films, Daylight Type and Type A (FM-2A) 

'Kodachrome-X' Film, Daylight Type (FM-2B) 

'Ektacolor' Professional Films, Type S and Type L (FM-3) 

'Kodacolor-X' Colour-Negative Film (FM-4A) 

By white light 

In general, chromatograms are best photographed against a matt black 
background, such as a black cloth. When using colour-negative films 
which are to be printed on automatic colour printers, leave a black border 
all round which is approximately J the area of the chromatogram: this 
is to ensure that the negative is printed at about the optimum density. 

In all colour photographs, and especially where the negatives are to be 
printed with manual selection of the printing filters, it is desirable to 
include a colour standard of some sort in the picture area. The 'Kodak' 
Colour-Separation Guides are suggested for this purpose; they include a 
calibrated grey scale and a set of colour patches. 

Issue A Kodak Data Sheet 

SC-6 



Almost any light-source can be used to illuminate the chromatograms 
provided that it is matched to the type of film in use, if necessary by 
using filters over the camera lens (see the Data Sheets on individual films). 
However, a standard lighting arrangement is desirable for reproducible 
results, and flash (either bulb or electronic) is ideal. 

By ultra-violet radiation 

Direct Method: As the radiation-source is usually monochromatic, it is 
not worth using colour materials which would only record the spots as 
dark areas against a blue background. 

Fluorescence Method : In this method, the spots on the chromatogram are 
made to fluoresce under ultra-violet excitation. As the fluorescence is 
usually faint, it is essential to subdue the visible lighting so that the 
fluorescence becomes visible in the darkness. Also, an ultra-violet- 
absorbing filter should be used over the camera lens to prevent the exciting 
radiation from reaching the film and swamping the fluorescence. For 
further information, see Data Sheet SC-3. 

MONOCHROME PHOTOGRAPHY 

Colour photography is not always necessary or practicable. Mono- 
chrome materials can be used advantageously in many ways. 

By white light 

Little need be said of the direct photography of chromatograms because 
it is straightforward close-up photography. As with direct colour 
photography, a grey scale can usefully be included in the picture area. 
Normal panchromatic materials can be used, a medium-speed film such 
as Tlus-X' Pan sheet, roll, or miniature film (Data Sheet FM-36, 48, or 
52, respectively) being a useful choice. 

Rough records of chromatograms can be made by contact printing the 
chromatogram on to a high-contrast document-copying paper, such as one 
of the 'Kodagraph' papers, or those used in the Kodak 'Readyprint' and 
'Verifax' processes and the chemical-transfer process. The adsorbent 
side of the chromatogram should be placed in contact with the emulsion 
side of the paper. 

By ultra-violet radiation 

Direct Method: Full information is given in Data Sheet SC-3. The 
contact-printing technique using document-copying papers as suggested 
above can be simply adapted by substituting an ultra-violet source for the 
normal white light-source. 

Fluorescence Method : The requirements are essentially the same as when 
using colour materials for this purpose. More information will be found 
in Data Sheet SC-3. 

An ingenious method of recording fluorescent spots by contact printing 
has been suggested.* It involves sandwiching a thin gelatin ultra-violet- 
absorbing filter (such as the 'Wratten' Gelatin Filter No. 2B) between the 
emulsion side of a sheet of photographic paper and the adsorbent side of 

*D. Abelson, Nature, 188, No. 4753, 3 Dec. 1960, pp. 850-851. 

SC-6 2 



the chromatogram. By exposing through the back of the chromatogram, 
the ultra-violet radiation is able to excite the spots to fluoresce and is then 
absorbed by the filter; the visible fluorescence is not absorbed by the 
filter and, hence, exposes the paper. For this method a contrasty grade of 
enlarging paper, or a document-copying paper, should be used. 

AUTORADIOGRAPHY 

With some separations, one or other of the components may only be 
detectable if it is "labelled" radioactively. In these cases, the chromato- 
gram is placed in close contact with a photographic emulsion and the 
radioactive areas allowed to expose it. After exposure and processing, 
this gives a visible record of the distribution of the labelled component. 
Suitable materials for this purpose are the range of 'Kodak' direct-type 
X-ray films (see Data Sheets FM-17, FM-25, FM-27, and FM-28) 
and 'Kodak' X-ray Paper. The latter material is very suitable for 
chromatograms containing 3 H-labelled substances, and 'Kodirex' X-ray 
Film (Data Sheet FM-17) is the most generally useful of the X-ray-film 
range. 



Further details of Eastman 'Chromagram' Sheet can be obtained from 
the Research Chemicals Sales Department, Kodak Limited, Kirkby, 
Liverpool, England. 



SC-6 



The following product names appearing 
in this Data Sheet are trade marks 

KODAK 

KODAGRAPH 

EASTMAN 

CHROMAGRAM 

VERIFAX 

WRATTEN 



Kodak Data Sheet KODAK LIMITED LONDON 

SC-6 

PDPL-SC-6/HWP2/9-69 



INFRA-RED PHOTOGRAPHY 



Infra-red photography is basically the photographic recording of 
infra-red images. Generally, the methods employed are as simple as 
those for ordinary photography, but the nature of infra-red radiation 
necessitates the adoption of some special photographic techniques. 

The properties of electromagnetic radiations depend on their wave- 
length. Thus, wavelengths between about 400 nm (blue-violet) and 
700 nm (deep red) are visible to the unaided eye. Extending out in- 
definitely from 700 nm there are invisible radiations, known as infra-red, 
which can be detected by a specially sensitized photographic material. 
As their wavelength increases, these radiations merge into heat waves, and 
finally into radar and radio waves. Direct photography can be used to 
record wavelengths as long as 1350 nm, but the range principally dealt 
with in this Data Sheet is from about 700 nm to 900 nm. 

Photographic emulsions are sensitized to record only the near infra-red 
spectrum. Beyond this region, storage and use of film would be im- 
practical as it would be fogged even by heat from the body. Temperature 
differences are detected by types of thermal recording, not by direct 
photography. 

RECORDING INFRA-RED RADIATION 

There are six principal methods of photographically recording infra-red 
radiation, two are direct and four are indirect. Because the other methods 
are somewhat complex and specialized in their applications and methods 
of use, this Data Sheet deals chiefly with one of the direct methods, that 
concerning the use of specially sensitized photographic emulsions. Brief 
notes and references are, however, included as a guide to the other 
methods. 

Indirect methods 

1 Evaporography 1 ' 2 : This method depends on the volatilization of a 
thin layer of material when warmed by exposure to infra-red radiation. 
Basically, a thin membrane is coated on one side with a thin layer of a 
volatile substance, such as camphor or naphthalene, and on the other side 
with a black material, such as lampblack. Any infra-red radiation falling 
on the black side is absorbed and raises its temperature, causing the 
volatile substance to sublime away from the warm parts and deposit on 
the cooler unexposed places. Thus, the parts of the coating on which 
the radiation falls become thinner. However, they remain as they are 
after exposure ceases, provided that the volatile side is kept in an enclosed 
space saturated with the vapour of the material used for the coating. 
This is due to the fact that a steady state is provided by a substance in 
equilibrium with its vapour; the image formed on the membrane by the 
volatilization may then be photographed normally by reflected light. 

2 Phosphorophotography 1 - 2 : Infra-red radiation has the property of 
extinguishing or "quenching" the phosphorescence of substances excited 

Issue D Kodak Data Sheet 

SC-7 



by suitable radiation. Thus, a record of the infra-red radiation may be 
obtained by photographing the image resulting from focusing the radiation 
on to a phosphorescent surface. 

3 The Use of Electronic Image-Converters 1 ' 2, : An electronic image- 
converter consists of an evacuated glass tube containing a photo-cathode 
at one end which emits electrons when "illuminated" by ultra-violet, 
visible, or infra-red radiation. The number of electrons emitted at any 
one point from the photo-cathode is proportional to the intensity of the 
radiation incident on that point. An electron image is therefore pro- 
duced on the surface of the photo-cathode. These electrons are acceler- 
ated to high speed by the application of an external high voltage between 
the photo-cathode and the open anode at the other end of the tube, 
The electron image is not only accelerated, it is also focused on a fluorescent 
screen (contained within the anode) at the end of the tube. The image 
on the fluorescent screen can either be viewed direct or photographed. 
As the brightness of the image obtained is determined by the characteris- 
tics of the electrical circuits and of the fluorescent screen, it is possible to 
make it much brighter than the original infra-red image. The principal 
difficulty with this method is that the resolution capabilities of image- 
converters are rather low. 

4 Scanning Devices 3 '*- 5 : In these devices, an infra-red sensitive photo- 
electric cell is made to scan the area under observation in a series of 
horizontal lines. By amplifying the output from the photo-electric cell, 
a line image of the infra-red emission of the subject can be produced on 
electrochemical paper or displayed on a television screen, which can be 
photographed if necessary. 

Direct methods 

1 Destruction of the Latent Image by Infra-red Radiation — the Herschel 
effect 1 : A latent image produced by exposing a photographic material to 
light of a shorter wavelength can be destroyed by subsequent exposure to 
light of a longer wavelength. This effect is called the Herschel effect, 
after its discoverer. Thus, by uniformly pre-fogging an emulsion, an 
infra-red record can be made by allowing the infra-red radiation to 
selectively destroy the latent image. In practice, this effect has been 
applied mainly in infra-red spectrography, although it also has several 
useful applications, such as producing direct positives in the camera and 
direct-positive copies of documents. 

2 The use of Specially Sensitized Photographic Emulsions : This is the 
principal method of recording infra-red radiation. Emulsions which are 
dye-sensitized to the region 700-880 nm are the most generally useful, 
but for special purposes the sensitivity can be extended to a maximum of 
about 1350 nm. 1 Whilst it might be possible to produce sensitizing dyes 
which would extend the sensitivity beyond this limit, two factors render 
direct photography impracticable. Water vapour in the atmosphere 
strongly absorbs radiation of wavelengths between about 1400 nm and 
1500 nm. Beyond 1500 nm, the amount of ambient heat in the surround- 
ings, or "black-body radiation" as it is sometimes called, would quickly 
fog the plates or films. 1 

SC-7 2 



Black-and-white infra-red photography 

This can be defined as the technique of using a camera lens to focus an 
infra-red image on to an emulsion sensitized to infra-red radiation so as 
to obtain a black-and-white negative record, and subsequently a positive 
print. The subject producing the image reflects or transmits varying 
amounts of the infra-red radiation falling on it, or the subject emits lumin- 
escence in the infra-red region when it is illuminated with visible light. 

Infra-red emulsions are sensitive to violet, blue and red light as well 
as to infra-red radiation. Therefore, a filter must be placed over the 
camera lens (or sometimes the light-source) to pass infra-red radiation 
and exclude visible light and ultra-violet radiation. To remove re- 
flected infra-red from a luminescing specimen, it is necessary to hold 
back infra-red from the light-source by means of an infra-red absorbing 
filter. In this way, it is ensured that any infra-red radiation arising from 
the subject can only be due to luminescence. It is also necessary to place 
over the lens, a filter which excludes visible light and transmits infra-red. 

Colour infra-red photography 

An infra-red colour film has three layers, as a normal colour film has, but 
the layers are sensitive to green, red and infra-red, instead of the usual 
blue, green and red. For filter details of the principles of infra-red colour 
film, see Data Sheet FM-1H. The main advantage of using a colour film 
to record infra-red radiation is that the usable infra-red band of the 
spectrum is as wide as that from green to red so there is potentially a 
wide range of distinguishable infra-red "colours". An infra-red colour 
film translates the various infra-red wavelengths into visible colour differ- 
ences on a transparency or print. A table of the rendering of some colours 
is given in Data Sheet FM-1H. 

APPLICATIONS 

There are many applications of infra-red photography, both black-and- 
white and colour. These are probably best classified by dividing them 
into groups, each of which utilizes a particular property of infra-red 
radiation. Some of the uses are briefly described below, but there are 
many more beyond the scope of this Data Sheet. 

I Infra-red radiation is less easily scattered than visible light. The 

haze which obscures the detail of a distant landscape, the surface layers 
of the skin and a large variety of dark pigments, all transmit infra-red rays 
and so permit the photographer to record detail invisible to the eye or the 
normal photographic emulsion. 

Typical applications which depend on the penetrating power of infra-red 
include aerial mapping 16 - 9 and long-distance landscape photography 1 ; 
the study of conditions inside burning furnaces which contain a haze of 
dust; the recording of stars hidden by the luminous haze of nebulae; the 
penetration of thin coverings of rust on tin plates in order to study the 
porosity of the plating. The size and distribution of particles have been 
studied by their varying power to scatter the rays. 10 

Infra-red photography is an established technique in clinical work for 
it permits a record to be made of subcutaneous conditions. 1 This is of 

3 SC-7 



value in the study of varicose veins and lupus (see Data Sheet MD-2.) 
Photography of the fundus of the eye is possible even when the cornea is 
visually opaque with cataract. Since infra-red radiation penetrates the 
surface layers of paintings it is of assistance in the study of the painter's 
technique. 

2 Infra-red radiation is frequently reflected or transmitted by coloured 
objects in a manner which has no connection with their visible colour. 

As a result, obliterated, over-written and charred documents have been 
deciphered, the authenticity of paintings, and in some cases the presence 
of underlying work on the same canvas, have been determined. Inks, 
pigments and other materials that appear identical to the eye are frequently 
rendered quite differently by an infra-red photograph. Documents 
charred by fire or blackened by age, dirt or stains can often be deciphered 
on an infra-red print. For works of art, infra-red photography can 
sometimes be of use for detecting the presence of over-painting and altera- 
tions, as the varnish or medium used usually differs in its infra-red trans- 
parency according to its age. In criminology, the presence of blood 
stains and gunshot-powder burns on garments can be detected, and infra- 
red photography assists in the examination of cloth, fibres and hair which 
have been dyed. 

Under the microscope 1 , detail in visually opaque sections of chitinous 
or silver-stained biological specimens and in various petrological slides 
can be recorded. 

Infra-red photography is of great use in plant pathology, ecology, 
hydrology, geology, animal studies and archaeology. 
Plant Pathology : Many plants under stress from disease or insects can be 
detected by infra-red photography because there is usually a loss of infra- 
red reflectance from affected verdue. Aerial surveys can often quickly 
detect a few affected trees in a forest or orchards, and the disease may 
therefore be prevented from spreading. 

Ecology: Features of the landscape can be distinguished by infra-red 
aerial photography. For example, different kinds of trees produce 
different colours, and damp areas show up darker than dry ones. 
Hydrology : Hydrological surveys show that even a few inches of clear 
water photograph very dark on infra-red film. On infra-red colour film, 
clear water shows black; water suffused with algae, red; water with a low 
dissolved-oxygen level, milky. Thus infra-red photography aids in 
detecting the sources and the extent of polluted water. Aerial mapping 
can also show drainage, overgrown shorelines and areas of floating plants. 
Geology : Some rocks give distinct infra-red "colours"; location of springs 
from a great height is possible; and alluvial drifts may be detected. 
Animal Studies : Some naturally camouflaged animals may be revealed by 
infra-red photography. 

Archaeology : Many crop and soil marks which are indiscernible to the 
unaided eye or which fail to record on a panchromatic film may show on 
an infra-red film. Some startling features have been revealed by the use 
of both black-and-white and colour infra-red photography. 

Other applications which depend on this characteristic of infra-red 

SC-7 4 



radiation include camouflage detection 9 , the preparation of the "black 
printer" in four-colour photomechanical work, and the study of carbon 
deposits in lubricating oils, made possible by the fact that carbon is opaque 
to infra-red. 

Infra-red photography can also produce "moonlight" or other dramatic 
effects in black-and-white pictures. 

3 Infra-red radiation is emitted by hot bodies at a lower temperature 
than that at which visible light is emitted. Bodies at temperatures as 
low as 350°C can be photographed by means of the infra-red radiation 
they emit. A very prolonged exposure is necessary in such cases but a 
relatively short exposure is sufficient to yield a photographic record of 
the heat gradient in boiler plates, cylinder heads, furnace walls, welds, 
and other very hot bodies (see Data Sheet IN-8). Another method of 
recording temperature distribution relies on coating the body to be heated 
with a thermo-sensitive paint or crayon, which exhibits known colour 
changes at specific temperatures, and photographing the result on normal 
colour film. 

4 Infra-red radiation, being invisible, enables photographs to be made 
in darkness. As the eye is not sensitive to infra-red radiation, it is possible 
to take photographs in complete darkness by screening flashbulbs, elec- 
tronic flash, or tungsten lamps with infra-red filters which absorb the 
visible light. 1819 It is thus possible to take unsuspected shots ; this method 
has been employed in criminal-detection devices, and psychical research 
workers have used it at seances. This technique is also useful in "candid- 
camera" work for non-dazzling and inconspicuous flash shots at close 
quarters. Although useful for "news" work, this technique is not 
recommended for conventional portraiture, since the tone rendering is 
falsified for the reason given in I on page 3. 

GENERAL MANIPULATION OF INFRA-RED MATERIAL 

1 Apparatus. No additional apparatus is needed for infra-red photo- 
graphy except a suitable filter. There are, however, a few precautions to 
be observed. As some materials used in camera construction and in 
darkroom shutters are transparent to infra-red rays, the apparatus used 
should be tested. In general, most artificial bellows compositions, 
vulcanites, and woods are transparent, while leather, metal*, and black 
papers and paints containing carbon are opaque. 

2 Focus. Infra-red rays normally come to focus at a greater distance 
from the lens than the visual focus. The actual difference between infra- 
red and visual focus differs with different types of lens, and the lens-to- 
film distance should be increased by between 1/400 and 1/100 of the focal 
length of the lens. For optimum definition at large apertures it may be 
necessary to determine the position of sharp focus by experiment. At 
apertures smaller than// 11, the normal depth of focus of the lens will 
usually permit neglect of this difference. 

3 Filters. All black-and-white infra-red emulsions are additionally 
sensitive to white light, and to confine the record to the infra-red a 
visually opaque filter must be used, either over the light-source (flash- 

* A lining of tin or other metal foil is a convenient temporary expedient for making camera bellows 
infra-red tight. 

5 SC-7 



light work 18 ) or over the camera lens. However, much work can be 
done using both red light and infra-red radiation, and the first three 
filters mentioned below do transmit both. 

Maximum working speed of these emulsions is obtained by using a 
'Wratten' 25 filter (red) : this is chiefly of interest in long-distance land- 
scape photography and non-dazzling flashlight work; the 'Wratten' 29 
(deep red) and 70 (very deep red) filters also fall into this general category. 
For a solely infra-red record yielding maximum rendering of distant 
detail and general use in the other applications listed, including "invisible" 
flashlight work, the 'Wratten' 88A filter, transmitting from 730 nm, is 
recommended. The working speed of an emulsion through the 'Wratten' 
88A filter is about half that through the 25, which transmits from 590 nm. 
The 'Wratten' 87 filter, which transmits from 740 nm, and the 'Wratten' 
87C filter, which transmits from 800 nm, are sometimes used in forensic 
and photomicrographic work, and for other special purposes. 

For flashlight work it may be preferable to coat the flashbulb with a 
suitably dyed lacquer — see references 18 and 19. 

All three layers of a colour infra-red emulsion are sensitive to blue 
light and a 'Wratten' 12 (deep yellow) filter should therefore always be 
placed over the camera lens. For fuller detail on the use of filters with 
infra-red colour film see Data Sheet FM-1H. 

RECOMMENDED MATERIALS 
Black-and-White Films 

'Kodak' Infrared Film : This is a moderately high contrast 35 mm film. 
'Kodak' High Speed Infrared Film : This is a high-speed moderately high- 
contrast film. The 35 mm size has a 0.004 inch (0.010 mm) 'Estar' Base. 
The sheet film has a 0.007 inch (0.018 mm) 'Estar' Thick Base. 

Plates 

'Kodak' Spectroscopic Plate Type I-N or Type I-Z are recommended 
for applications requiring infra-red sensitization. 

For details of the above materials see Data Sheet SE-3. 

Colour Film 

For details of Kodak 'Ektachrome' Infrared Film see Data Sheet 
FM-1H. 

Other materials 

Certain other special materials for aerial photography, and for astro- 
nomical and spectrographic work, may be available. If it appears that 
the requirements of a specific technique may not be met by one of the 
materials mentioned above, application is invited to Kodak Limited, 
P.O. Box 66, Kodak House, Station Road, Hemel Hempstead, Herts. 

STORING INFRA-RED MATERIALS 

Particular care should be taken in storing all unprocessed infra-red 
materials; owing to the amount of ambient black-body radiation, they 
have relatively poor keeping qualities. All materials should be kept in a 

SC-7 6 



refrigerator at a temperature range of 4-10°C (39-50°F) and with a relative 
humidity of 40-60 per cent, if they are to retain their true working 
speed and freedom from fog for any length of time. In any case, infra- 
red materials should not be stored at temperatures exceeding 18°C (64°F). 
To avoid moisture condensing on the cold surfaces, packages of 
material removed from cold storage should be allowed several hours to 
warm up to room temperature before being opened. 



REFERENCES 

1 W. Clark, Photography by Infrared, Chapman and Hall, 2nd edition, 
1946. 

2 C. E. Engel, Infra-Red Recording Today, Brit. J.Phot, 105, No. 5099, 
7th Feb. 1958, pp. 68-71 and 73. 

3 P. Delius, Seeing by Heat — The Pyroscan Electronic Heat Camera, 
Brit. J.Phot., 1 1 1, No. 5412, 10th Apr. 1964, pp. 278-283 and 290. 

4 K. Lloyd-Williams, The "Heat Camera" in Medicine, New Scientist, 
No. 400, 16th July 1964, pp. 162-164. 

5 C. M. Cade, The Industrial Potential of the "Heat Camera", ibid., 
pp. 165-167. 

6 G. C. Brock, Infra-Red Air Photography, Photogr. J., 90B, July-Aug. 
1950, pp. 114-117. 

7 S. Charter, An Introduction to Infra-Red Aerial Photography in 
Agriculture, Agriculture and Food Chemistry, 7, Aug. 1959, pp. 536- 
539. 

8 H. K. Meir, Uses of Infrared Emulsions for Photogrammetric Purposes, 
Soc. Photogr. Instr. Eng., I, Oct.-Nov. 1962, pp. 4-8. 

9 R. G. Tarkington and A. L. Sorem, Color and False-color Films for 
Aerial Photography, Photogramm. Engng., 22, Jan. 1963, pp. 88-95. 

10 Infra-Red and the Distribution of Particle Size, Brit. J.Phot., 86, 10th 
Feb. 1939, p.88. 

11 F. C. Bawden, Infra-Red Photography and Plant Virus Diseases, 
Nature, 132, 1933, p. 168. 

12 J. Eggert, VerofF. wiss. Zentral Lab Agfa, 4, 1935, pp. 101-118. 

7 SC-7 



13 A. Babel, Infrarot — Photographie im Pflanzenschutz, Angew. Bot., 17, 
1935, pp. 43-53. 

14 B. M. Duggar, Biological Effects of Radiation, McGraw-Hill, 1936. 

15 G. R. van Atta, Filters for the Separation of Living and Dead Leaves 
in Monochrome Photography, J.Biol. Photogr. Assoc, 4, No. 4, 1936, 
pp. 177-191. 

1 6 W. R. G. Atkins, The Transmission of Light and Total Radiation by 
Leaves, Proc. Roy. Soc. B., 122, 1937, pp. 26-29. 

17 R. Jackson, Detection of Plant Disease Symptoms by Infrared, J.Biol. 
Photogr. Assoc, 32, No. 2, May 1964, pp. 45-58. 

18 R. B. Morris and D. A. Spencer, Dazzle-free Photoflash Photography, 
Brit. J.Phot., 87, 14th June 1940, pp. 288-289. 

19 R. Graham and J. Webster, Infra-red Photographic Techniques for 
Industry, Ind. and Comml. Photogr., II, No. 9, September 1971 pp. 90-96. 



BIBLIOGRAPHY 

W. Clark, Photography by Infrared, Chapman and Hall, 2nd edition, 1946. 
Infrared, A Bibliography, Technical Information Division, The Library 

of Congress, Washington, U.S.A., 1957. 
H. L. Hackforth, Infrared Radiation, McGraw-Hill, 1960. 
C. E. Engel, Medical Photography in Practice, Fountain Press, 1961. 
A. Tyrell, Pictures by Heat, Perspective, 7, No.l, 1965, pp. 28-46. 
H. L. Gibson, W. R. Buddy, and K. E. Whitmore, New Vistas in Infrared 

Photography for Biological Surveys, J. Biol. Photogr. Assoc, 33, 

No. 1, Feb. 1965, pp. 1-33. 

I. Simon, Infrared Radiation, D. Van Nostrand, 1966. 

S. K. Matthews, Photography in Archaeology and Art, John Baker, 1968. 

Focal Encyclopaedia of Photography, Focal Press, 2nd edition, 1969. 

Applied Infrared Photography, Publication No. M-28, Eastman Kodak 
Company, 1970. Available from Kodak Limited. 



Kodak and Wratten are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

SC-7 

PDSC-7/XWPI0/I0-7I 



16 mm CINE-MICROGRAPHY 



By courtesy of R. McV. Weston, M.A., F.R.P.S., F.I.I. P., F.R.M.S., F.B.K.S. 

The combination of the cinematograph camera with the microscope 
constitutes a powerful and versatile tool adaptable to many branches 
of research. 

The most valuable features of this technique are : 

1 Complete control over the apparent speed of the object. 

2 Permanent records are obtained. 

3 Time is saved, as the apparatus can be made automatic in operation. 

As commercial apparatus is available from a number of manufacturers, 
it is not necessary for the user to construct his own. 

Apparent speed of object 

It is well-known that unless an object moves within a comparatively 
small range of speeds, it is very difficult, and often quite impossible, to 
observe its movements visually. The speed may be either too fast or 
too slow. In either case the use of the cinematograph camera is the only 
known method of making the apparent speed of the object suitable for 
detailed examination. In the first case, the motion can be analysed, 
using cinematography, by running the camera faster than the normal 
speed of the projector (16 or 24 frames per second), giving what is known 
as "slow motion", whereby the object appears to move more slowly than 



APPROX. TIME OF 
TAKING 100 FEET 
(16mm ) 





























































































































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!±i | N0RMAL~~~> l 

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VE SPEED 
STER 








































































































































































































































































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1000 










































































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CAMERA-TAKING 
SPEED 



Issue A 



Jar film projeaed ar U> frawes per second 
for film projcoietl m 24 frames per second 

Kodak Data Sheet 
SC-8 



normal (see Data Sheet IN-2), and in the second case, the motion can be 
synthesised by running the camera more slowly than the normal speed 
of the projector. This is known as "time-lapse" cinematography, and 
the object appears to move more rapidly than normal. 

The diagram shows the relationship between camera speed and the 
apparent speed of the object on projection of the film, for the range of 
camera speeds from one frame per 500 seconds (over 8 minutes), to 1000 
frames per second. It also shows the longest time that a 16 mm camera 
can be run for this range of speeds when using 100 feet of film. 

In addition, when using the microscope, the apparent rate of move- 
ment of an object is dependent upon the magnification, and therefore the 
final rate of movement on projection will depend upon both the magni- 
fication and the camera speed. Consequently, the camera speed should 
be increased if the magnification is increased, unless an increase in 
apparent speed is specifically required. 



Illuminants 

The illuminants most suitable for this work are tabulated below: 



ELECTRIC 
SUPPLY 


ILLUMINANT 


TYPE OF SPECTRUM 

AND RADIATION 

PRESENT 


PARTICULARLY 

SUITABLE 

FOR: 


1 D.C. 


100 candle-power 
Pointolite 


Continuous spectrum — 

ultra-violet, visible, and 

infra-red 


Low, medium, and high 
powers with trans- 
mitted light and dark- 
ground illumination. 
Camera speeds up to 
64 frames per second 


1 A.C. 


6-V 18-A ribbon- 
filament lamp 


Continuous spectrum — 
visible and i.r. 


3 A.C. 


Coiled-filament 
lamp 


4 D.C. 


Carbon arc 


Continuous spectrum — 
u.v., visible, and i.r. 


High powers with 
dark-ground illumina- 
tion 


5 A.C. 


2S0-W compact- 
source mercury- 
vapour lamp 


Line spectrum — u.v., 

blue, green, yellow, 

and i.r. 


Phase-contrast work 


6 D.C. 


Xenon arc 


Continuous spectrum — 
u.v., visible, and i.r. 


Colour films 


7 — 


Sun (heliostat 
required) 


Continuous spectrum — 
u.v., visible, and i.r. 


High camera speeds 
with dar k-gr ou nd 
illumination 



With filament lamps, particular care is required to obtain a perfectly 
even field of illumination. The carbon arc cannot usually be employed 
owing to its liability to flicker and to its limited time of run. 



SC-8 



Illuminating system 

The Kohler system of illumination is recommended for all classes of 
work. Diffusing screens of ground glass should be avoided as they 
inevitably lead to loss of contrast and may easily introduce glare. 

Filters 

Filters will be necessary according to the following table : 



TYPE OF FILTER 


PURPOSE 


Neutral-density 


Reduction of illumination to correct value for exposure. 

The sub-stage iris diaphragm should never be used for 

this purpose. 


Colour 


For phase-contrast work the mercury green line is 

generally used. Use the mercury lamp with 'Wratten' 

Filter No. 77. 


Colour-Compensating 


To correct colour temperature with colour films (see 
Data Sheet CL-3). Illuminants 1, 2, and 3 are all deficient 
in blue. With 4, 6, and 7, colour films balanced for day- 
light should be used. 


Heat-absorbing 


A water cooling trough or an efficient heat-absorbing 
filter should always be used. 


U.V. absorbing 


A filter opaque to u.v., such as the 'Wratten' No. 2B, 
should always be used. 



Protective shutter 

Most living biological material is adversely affected by light. Infra- 
red and ultra-violet radiation are particularly harmful and therefore a 
protective light shutter should always be employed in order to keep the 
preparation in darkness, except when an exposure is to be made, or when 
it is necessary to check focus and the like. 

Microscope 

Almost any good microscope is suitable, but the use of a rotating stage 
has much to commend it. Most microscope images have neither "top" 
nor "bottom", nevertheless it is often very desirable so to orientate the 
preparation that the 16 mm frame is employed to the best advantage. 
Needless to say, the highest quality of optical components (sub-stage 
condenser, objectives, and eyepieces), should always be used. 

Photography on to the small 16 mm frame (approximate dimensions 
10x7 mm) is somewhat different from ordinary photomicrography using 
larger sensitive material. In the latter case, fine detail has to be recorded 
for subsequent visual examination (with or without a small degree of 
enlargement). In cinemicrography, however, a very large degree of 
enlargement is inherent in the projection of the finished film. If the 
projected picture is only four feet wide, this magnification is of the order 



SC-8 



of x 120, and for a 6-foot-wide picture, x 180. This calls for the best 
possible negative, free from grain and focusing errors, and containing 
very fine detail which may be too fine to see with the unaided eye. Errors 
of exposure cannot be tolerated. In order to obtain such a small, high- 
quality negative, the image formed by the combination of microscope 
and camera must be the best possible. This may demand the use of 
medium or low-power objectives of very high quality and large numerical 
apertures. 

Incubator 

For most biological material (warm blooded), the preparation must be 
maintained at 38°C (100°F). While warm stages of various types are 
quite satisfactory for visual observation they are not so suitable for 
cinemicrography. One reason is that there is an unknown amount of 
cooling from the microscope stage and objective, and the use of an 
efficient incubator has much to commend it. The whole microscope is 
then maintained at the proper temperature and if the incubator is properly 
controlled, there is much less likelihood of the preparation going out of 
focus. 

Watching eyepiece 

The watching eyepiece is, perhaps, the most important part of the 
entire equipment. It should furnish an image of high quality and pref- 
erably be fitted with a graticule showing the size of the 16 mm frame. 
The field of view should be somewhat larger than the field photographed, 
as it is then possible to see if any unwanted object is likely to come into 
the field. Watching eyepieces are made bv a number of firms such as 
Wild. 

The Wild instrument has much to commend it as it contains two 
beam-splitting prisms, either of which may be used as occasion demands : 
one of these diverts only 5 per cent of the light to the eye, with the 
remaining 95 per cent going to the camera, while the other divides the 
fight equally between the eye and the camera. In addition, this accessory 
contains a small photo-electric cell which can be used (with a suitable 
external microammeter) as a most useful guide to correct exposure. 

This watching eyepiece has another useful function; it can be fitted 
with a projection tube, whereby images (such as a pointer, numbers, or 
simple wording) can be superimposed on the microscope image and 
recorded by the camera at the instant that the film is made. 

Camera 

Any good 16 mm camera can be used, provided it is capable of taking 
single instantaneous or time exposures. A very suitable camera is that 
made by W. Vinten Ltd. — The Vinten Scientific Camera, Mark III; 
this has an internal electric drive and is almost vibrationless in action. 
For speeds up to 200 frames per second, if this type of work has to be 
undertaken, a special type of camera is also available — the Vinten RC250 
Camera. In addition, 200 feet of 1 6 mm film (approximately 8000 pictures) 
can be accommodated, which is a great advantage in some classes of work. 

SC-8 4 



Camera stand 

A rigid stand is required to support the camera, and suitable com- 
mercial apparatus is available. W. Watson make a pillar stand, and 
Wild manufacture a stand which is available in two forms, one for use 
on a table, and the other for wall mounting. The actual camera bracket 
also has about four inches of vertical travel by means of a rack and 
pinion drive. Wild also supply an anti-vibration plate, to support the 
microscope, which suppresses camera vibration and also that caused by 
persons moving about the laboratory. 

Time-lapse equipment 

Some sort of timer and camera control is also required and here again 
commercial equipment is available. 

Wild manufacture an electronic interval timer and camera control 
expressly for Bolex cameras, and Vinten supply an electro-mechanical 
arrangement for their camera which has the great advantage of simplicity. 

Emulsions 

For general work in monochrome, a fast panchromatic reversal emul- 
sion, such as 'Plus-X' Reversal Film, Type 7276 (Data Sheet FM-12), is 
recommended. Faster emulsions, such as 'Tri-X' Reversal Film, Type 
7278 (Data Sheet FM-11), should be reserved for cases in which the use of 
a very fast emulsion is absolutely essential. 

For certain phase-contrast work, it may be desirable to use an emulsion 
of higher contrast and then 'Kodak' High-Contrast Negative Film, Type 
7457 (Data Sheet FM-9) should be used. Unlike the two films above, this 
is a negative film which is processed by the user. 

Test exposures 

Owing to the large number of variable factors in this work, test exposures 
should always be made before starting a run with a new preparation. 
It is convenient if one film chamber is always kept ready for this purpose. 

If the object is coloured, a colour film can be used. As the method 
of test exposures is not always suitable for this type of film, an accurate 
method of exposure estimation should be used; the photo-electric cell 
in the Wild watching eyepiece proves very useful for this purpose. 

Complete apparatus 

Several commercial cine-micrographic outfits are available which are 
complete and ready to use. Such equipment is available from Wild, 
Zeiss, and Prior. The latter uses an inverted microscope which has 
advantages for certain classes of work. 

Bibliography 

R. W. Gooding, An Apparatus for Cinemicrography, J. Photogr. Sci., 6, 
May/June 1958, pp. 81-82. 

5 SC-8 



D. McNish and R. E. Trotman, A General-Purpose Electronic Timer — 

particularly suitable for Time-Lapse Kinemicrography, J. Sci. Instr., 

35, Aug. 1958, pp. 309-310. 
A. T. Brice, Instrumentation for Cinemicrography, Photogr. Sci. and Eng., 

3, No. 4, July/ Aug. 1959, pp. 186-191. 
W. Pybus, Adaptation of the Vinten 16 mm Scientific Mk. 1 Camera for 

Time-Lapse Cine-photomicrography using an Electromechanical Timer, 

J. Roy. Micro. Soc, 79, Part 4, 1959-60 (published Feb. 1961), pp. 

369-375. 
G. G. Rose, Cinematography in Cell Biology, Academic Press, 1963. 
A. T. Brice, Cinematography in Cell Biology, Society of Photo-Optical 

Instrumentation Engineers Journal, 4, No. 4, 1966, pp. 165-168. 

APPENDIX 

List of equipment manufacturers 

The following is a list of some of the manufacturers of cine-micrographic 
apparatus and equipment; it should not be regarded as comprehensive. 
Details should be obtained direct. 

W. Vinten Ltd., Western Way, Bury St. Edmunds, Suffolk. 

W. Watson & Sons Ltd., Bells Hill, Barnet, Hertfordshire. 

Wild Heerbrugg (U.K.) Ltd., 51 Church Street, Maidstone, Kent. 



Kodak, Wratten, Plus-X, and Tri-X are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

SC-8 

PDSC-8/rlWPi/l2-70 



AUTORADIOGRAPHY 



In recent years, striking progress has been made in utilizing and improving 
the sensitivity of photographic emulsions to charged atomic particles, such 
as electrons, mesons, protons, and alpha particles. Photographic materials 
are available that are capable of recording the paths of charged panicles 
of any energy, and the use of these materials led to fundamental dis- 
coveries in nuclear physics and cosmic-ray research. Also, they are 
intensively employed to trace the paths of small amounts of radioactive 
substances in metabolic studies of plants, animals, and humans, in metal- 
lurgy, and in several other fields of scientific interest. 

The chief means of tracing the paths of radioactive isotopes are the 
electronic counters and the photographic emulsion. The basis of the photo- 
graphic technique is the placing of a sample, such as a botanical, histo- 
logical, or metallurgical section containing a radioactive material, in 
contact with a suitable photographic emulsion. After exposure and 
processing, the photographic layer reveals the location of the radioactive 
material within the sample. The image thus obtained is called an auto- 
radiograph. 

One of the simplest applications of the technique is the autoradiography 
of a relatively large specimen such as an ash-tree seedling. The root of 
the seedling is first placed for a few hours in a weak aqueous solution 
containing radioactive phosphorus ( 32 P). After the plant, nourished by 
this solution, has taken up some of the radioactive phosphorus, 
it is placed in contact with 
a fast X-ray film (pre- 
ferably in a vacuum cassette 1 ) 
for a one-day exposure. The 
radioactive phosphorus decays 
with the emission of high- 
speed electrons and this 
causes ionization of some of 
the silver-halide grains of the 
emulsion and renders them 
developable. After process- 
ing, the autoradiograph 
reveals the distribution of the 
radioactive phosphorus with- 
in the leaves, the younger 
leaves being more intensively 
fed than the older ones — 
Figure 1. This application is | 

used extensively to study the 1 i 

fate of labelled ("tagged") I i 

atoms within the macro- 
structure of animal or plant Rgure ,. Autoradiograph of ash-tree seedling 
tissues. using **P. 




Issue F 



Kodak Data Booklet 
SC-IO 



A different application concerns the investigation of microstructures, 
in particular the distribution of radioactive tracers within histological, 
sections. Since the final record must be viewed under the microscope, 
this work also involves the further problem of achieving a high degree 
of resolution combined with high sensitivity of the photographic material 
to charged particles. The problem has been solved by the use of photo- 
graphic materials that have been designed specifically to record nuclear 
particles. 2 In this Data Sheet is described the use of 'Kodak' Fine Grain 
Autoradiographic Stripping Plate AR.10. 

PHOTOGRAPHIC MATERIAL 

The photographic emulsions used for the recording of nuclear-particle 
tracks are characterized by high intrinsic sensitivity, fine grain, and close 
packing of the grains. The achievement of this latter characteristic 
requires an extremely high concentration of silver halide in gelatin. 
An emulsion of this type is particularly suitable for the autoradiography 
of microsections since it provides high resolution combined with high 
sensitivity to charged atomic particles. Because of the divergence of 
charged particles originating in the specimen, and because of their 
scattering within the specimen, optimum resolution is obtained only if 
the emulsion layer and the specimen are very thin, and both are in very 
close contact. It has been calculated 3 that an emulsion thickness of 5(xm 
or less is needed for optimum resolution. 

Various techniques have been suggested for the autoradiography of 
microsections. According to one investigator, the specimen may be 
floated on to the photographic emulsion layer 4 , while others have painted 
a thin layer of emulsion on to the specimen. 5 Probably the most con- 
venient method that has been suggested so far involves the use of a 
stripping film or stripping plate as described in the literature. 6 ' 7 ' 8 

With these materials, an emulsion layer (usually attached to a thin 
gelatin supporting layer to facilitate handling) is stripped from its 
temporary glass support and transferred to the specimen — see Figure 2. 
This technique allows the emulsion to be placed in permanent and 
intimate contact with the specimen as the processing solutions can per- 
meate the layer. Subsequent examination can be undertaken with the 
knowledge that the specimen and the autoradiograph are in perfect 
register. 

Kodak Limited manufacture a plate of this type — 

'Kodak' Fine Grain Autoradiographic Stripping Plate AR.10. 

This plate has a fine-grain emulsion of high silver-halide/gelatin 
ratio ; the emulsion layer of 5(Jtm is reinforced by a gelatin layer lOjxm thick. 
The relative speed obtainable with this plate depends entirely on the 
radioactive isotope in use, i.e., on the energy of electrons or alpha-particles 
emitted. 

Safelighting 

The plate, and the transferred emulsion layer, should be handled and 
processed by the fight from a safelamp fitted with a 'Kodak' Safelight 
Filter, No. 1 (red) and a 25 watt lamp, at a minimum distance of 1.2 metres 
(4 feet). 

SC-IO 2 



When using the plate for grain-counting techniques, as little light as 
possible should be allowed to fall on the emulsion until processing is 
completed. 

STRIPPING-FILM TECHNIQUE 
Mounting the specimen 

The glass slides on which the specimen sections are to be mounted 
should preferably be "subbed" (i.e., coated with a layer of gelatin) to 
ensure good wet-adhesion of the emulsion when the autoradiographs are 
processed. The following method (from Wall's Photographic Emulsions, 
Chapman and Hall, 1929) should prove satisfactory : 

1 Clean the slides by soaking them in the following solution until they can 
be wetted perfectly by tap water: 

Potassium dichromatef 100 grammes 

Sulphuric acid (cone.)* 100 ml 

Water to make 1 litre 

Dissolve the potassium dichromate in three quarters of the total volume 
of water, then add the sulphuric acid to the solution very gradually and 
with constant stirring. Make up to total volume of one litre. 

2 Wash the slides and then dip them bodily in the following solution at 
about 20°C(68°F): 

Gelatin 5 grammes 

Chrome alumf f 0.5 gramme 

Water to make 1 litre 

Without further treatment, place the slides in a rack to drain and dry. 
It will probably prove convenient to treat larger sheets of glass and cut 

them down to the required size, usually 1x3 inches, for use. Mount 

the specimen sections direct on these "subbed" slides. 

Preparation for exposure 

The procedure involved in using 'Kodak' Fine Grain Autoradiographic 
Stripping Plates is illustrated in Figure 2. Cut through the stripping layer, 
with a sharp blade, around an area sufficient to cover the entire specimen, 
with a margin of at least 6mm (0.25 inch) all round. Place the micro- 
scope slide bearing the specimen on the bottom of a glass dish filled to a 
depth of at least 25mm (1 inch) with distilled or filtered water. The 
water-bath should be at room temperature — preferably between 16 and 
21°C (61 and 70°F). Using the tip of the blade, remove the section of 
stripping film from the glass; then turn it over and place it on the surface 
of the water with the emulsion side underneath, facing the specimen. 
As it swells, the stripped layer first crumples and then stretches out tight 
and flat. Allow it to swell for 2 or 3 minutes more and then lift it 
from the water by raising the slide underneath it. If the slide 
is held at about 30° from the horizontal, so that one edge touches the 
emulsion first, the emulsion will drape itself snugly over the specimen and 

t CAUTION: Irritant. Avoid contact with skin and eyes. Avoid breathing dust. In case of contact, 
flush with plenty of water; for eyes flush for at least 15 minutes and get medical attention. If swallowed 
get medical attention immediately. 

* WARNING: Corrosive — causesburns. Avoid contact with skin, eyes and clothing. In case of contact, 
flush immediately with plenty of water; for eyes flush for at least 15 minutes and get medical attention. 
If swallowed, give milk or water. GET MEDICAL ATTENTION. 
ft Prolonged or repeated skin contact should be avoided. 

3 SC-10 



stripping emulsion 
glass support 




■ emulsion 
-gelatin 

■ glass 



(greatly enlarged) 



Cut off the area of 
emulsion required to 
cover specimen. 



(a) Place microscope slide 
with specimen on bottom 
of dish filled with distilled 
or filtered water. 



slide and (b) Turn emulsion downwards 
specimen and float on surface of water 
for approximately 5 minutes. 




Figure 2. 



Lift specimen to contact 
emulsion. 



Procedure involved in autoradiographic technique when using stripping 
plates. 



most of the water will drain away as the slide is gradually lifted clear of the 
water. 

Cleanliness of the water, particularly of the surface, is most important, 
as floating particles or scum will tend to become trapped between the 
emulsion and the specimen. Very long floating times should be avoided 
as there is some evidence that they promote an increase in background 
fog by leaching out some of the emulsion constituents. 

Alternatively, when reproducible working is important, when especially 
low background counts are required, or exposures longer than 2 weeks are 
expected, the transfer of the emulsion is better effected by floating the 
stripped emulsion layer on a solution of controlled bromide concentration, 
such as that described and claimed in the complete specification of UK 
Patent Application 43206/68 9 . Such a solution may be prepared from the 
following stock solution — 



SC-IO 



STOCK SOLUTION 
Sucrose (white granulated sugar) 200 grammes 
Potassium bromide 0.1 gramme 

(or 10 per cent solution) (1 ml) 

Water to make 1 litre 

For use, dilute 1 volume with 9 volumes of water and mix thoroughly. 
Use at room temperature — preferably between 16 and 23°C (61 and 
73°F) — in the same manner as the plain water bath. Allow the emulsion 
layer to float for at least 2 minutes; equilibrium will effectively be reached 
within this time and no change of emulsion properties should result from 
longer floating times. To avoid results being spoiled by micro- 
organisms, use a fresh diluted solution every day. Discard the stock 
solution as soon as any cloudiness is observed. 

Dry the specimen with its superimposed emulsion layer in a 
stream of cold air and place in a light-tight box for exposure. The tempera- 
ture within the box should not exceed 21°C (70°F). 

When photographic emulsions are applied and processed in direct 
contact with the specimen, several unwanted effects may occur. Firstly, 
radioactive materials may be lost if they are soluble in water or in the 
processing solutions; secondly, spurious photographic images may be 
produced by chemical interaction of the specimen and the emulsion; and, 
thirdly, the specimen may undergo changes owing to reaction with the 
processing solutions. Various methods of avoiding these effects have 
been investigated including the interposition of an inert layer between the 
specimen and the emulsion 10 , n , 12 , the use of freeze-dried specimen 
sections 13 , 14 , 15 , and the use of a non-aqueous bath for floating the strip- 
ping film. 16 

Exposure 

As a rough guide, a content of 1 microcurie per gramme of tissue 
would require about 20 days' exposure. 

For optimum results however, so many factors operate that the usual 
practice is to prepare a large batch of slides and process a few slides at 
intervals suggested by calculations or previous experience. With the 
tendency to use long half-life isotopes and specimens of low mass, some 
workers expose for up to 6 months. 

PROCESSING 

During and after exposure, the emulsion layer remains in contact with 
the specimen, and the composite preparation is immersed in the various 
processing solutions. Being in permanent contact, proper register is 
maintained. 

Developing 

The recommended developer for this emulsion is 'Kodak' D-19 
Developer Powder, stock solution used undiluted; the formula is given 
in Data Sheet FY-2. 

If sufficient exposure has been given, optimum results will be 
obtained with this emulsion by developing for not longer than 5 minutes 
at a temperature of 20°C (68°F). However, when the adequacy of the 
exposure is doubtful, longer developing times may be needed to increase 

5 SC-10 



the effective emulsion speed. Prolonged development, however, increases 
the background and is inadvisable for grain-counting procedures. 

Rinsing 

To remove any residual developer, immerse the specimen and attached 
emulsion, for not less than 30 seconds, in a bath of clean water at 
18-21°C(64-70°F). 

Fixing 

Fix the composite preparation, at 18-21°C (64-70°F), for twice the 
clearing time in a solution of Kodak 'Metafix' Powder or a solution made 
up according to Kodak formula F-24. In areas having soft water supplies, 
some users have found it necessary to use an acid hardening fixer, such as 
Kodak 'Unifix' Powder or a solution made up according to Kodak 
formula F-5. (The F-5 and F-24 formulae are given in Data Sheet 
FY-4). 

Washing and drying 

Wash the preparation in gently running water for 5 minutes, and dry in 
a dust-free atmosphere. 

STAINING PROCEDURE 

At a London hospital, good results were obtained, with this emulsion, 
by staining rat thyroid through the gelatin layer with Ehrlich's acid 
baematoxylin for 15-20 minutes, and differentiating in 1 per cent aqueous 
hydrochloric acid. Further information on staining is given in references 
17 and 18. 

II = tl U S II i tt g 11 t u 

'Th 's us -sms. i»sm ««» *•• ««• **• ;«• 

•*o „-„ »s>, «*« ;»- ,- • »• •;• ?•• 5t5 

* ' *«* Sfttf 

' m V ; , mmwm **♦ 

* « «* * & w mm 

mtit 



s 


II 


= II 


II 


r 


M = 


= 


it 


r ii 


= 


•i 


Z 11 


II 


s 


•i = 


^© 


ii 


= ii 


II 


~ 


ii = 


~ 


ii 


= ii 


II 


£ 


ii = 



• ••* " : « * « 



ma* 
sua* 

• ■• » 
a w*« 



= ii =ji ii r ii : •••• •• 




II a II w M II « If 1 A M tf M ^B_ ^t ^K & 

'""■ * ■ *— * ■ I I «M 1 1 «MI 

Figure 3. Test chart enlarged from Figure 4. Autoradiograph of radio- 

a 'Kodak' Maximum-Resolution Plate, active test chart on emulsion of 'Kodak' 

this has now been replaced by the Fine Grain Autoradiographic Strip- 

'Kodak' High Resolution Plate. ping Plate AR.10. 

SC-10 < 



S 11 Z If 
II S it z 

S 11 s n 



M if m 

* m m * 






',*'' < ~ 



|xm 3 [J.m 10 f*m 

Figure 5. Effect of distance between test chart and emulsion. 



RESOLUTION 

One of the early difficulties in autoradiography was the practical 
assessment of the obtainable resolution. There has been described an 
ingenious method for the objective measurement of resolution. 19 A test 
chart, such as that used for deternuning the resolution of photographic 
lenses, is reduced photographically on to a 'Kodak' High Resolution Plate. 
Under suitable conditions this material permits a resolution of better than 
2000 lines per millimetre. The test chart shown in Figure 3 is an actual 
enlargement of a silver image, 0.5 x 0.35 millimetre in size, on the earlier 



1*1 






Esp 



ft*;; 



Figure 6. 35 S in bean-root chromosomes, probably synthesized into proteins. Distri- 
bution of 36 5 follows constant pattern. Left — phase-contrast photomicrograph. 
Right — same field, without phase-contrast, showing autoradiograph on AR.10 emulsion. 
Courtesy of A. Howard and S. R. Pelc, Ciba Foundation Conference on Isotopes in 
Chemistry, published by J. and A. Churchill, Ltd. 



SC-IO 



Maximum-Resolution Plate which had a resolution of better than 1500 
times per millimetre. The silver image was then reconverted into a silver- 
halide image and "toned" with radioactive iodine ( 131 I). Figure 4 shows 
a similar enlargement of an autoradiograph of the small radioactive test 
chart. From the known separation of the lines, the resolution given by 
this plate was found to be better than 2.5um. Greatly inferior resolution 
was found when the radioactive test chart was separated from the emulsion 
by as little as 3um — Figure 5. The resolution also depends greatly on the 
thickness of the specimen, since particles emitted at greater distances from 
the emulsion will show greater divergence. Resolution of the order 
mentioned can be attained only with thicknesses of specimen not exceeding 
5[xm. 

In addition, the resolution obviously depends on other conditions such 
as the range of electrons applied, the distance between the emulsion and 
the specimen, the thickness and structure of the specimen, and on the 
thickness of the emulsion. 



-# 






w * 











• If J?*' 






_ * 


* id 


1 ■ . J*. 








■'** '■ 


Mf- , 




'I , 


r^±0'" J 






" **w * 




1KfSflKBS> 



Figure 7. Autoradiograph of thyroid of 
rat, injected with 131 I and stained with 
haematoxylin and Celestin blue, made on 
the emulsion of a 'Kodak' Fine Grain 
Autoradiographic Stripping Plate AR.10. 
Courtesy of I. Doniach and S. R. Pelc, 
and The British Journal of Radiology. 



QUANTITATIVE EVALUATION 

For a quantitative estimation of 
the amount of radioactive sub- 
stance within a given volume of a 
section of specimen, itis convenient 
to express the sensitivity in terms 
of grain yield — the number of 
photographic silver-halide grains 
rendered developable per incident 
electron. 20, 21 This grain yield has 
been estimated to be of the order 
of unity for radioactive iodine and 
phosphorus. If the exposure of 
the autoradiograph is chosen so 
that the number of developed 
grains below a given area of the 
specimen can be counted, an esti- 
mate of the activity of the specimen 
can be obtained. The number of 
grains rendered developable with- 
out exposure, i.e., the number of 
fog grains, has to be determined 
also with an unexposed but 
developed emulsion as control. 
The number of fog grains has to 
be subtracted from the total 
number of developed grains in 
order to obtain an estimate of the 
number of incident electrons. 



SC-10 



INTERPRETATION OF RESULTS 

Great care must be taken in the interpretation of autoradiographs. 
Information on possible pseudo-photographic effects encountered in this 
kind of work may be found in references 22 and 23. Many chemical 
reactions are known which lead to the formation of latent images in photo- 
graphic materials in contact with the reacting compounds. Oxidizing 
agents have an opposite effect, as they tend to cause destruction of the 
latent image. Therefore, whenever an autoradiograph is made, it is 
advisable also to make as a control an autoradiograph of the specimen 
which contains no radioactive material. As mentioned earlier, some 
precaution may be necessary to preclude effects due to chemical fogging. 

AUTORADIOGRAPHY WITH OTHER MATERIALS 

The method of track autoradiography 15 offers advantages in some cir- 
cumstances. Details of suitable sensitized materials may be found in the 
booklet "Kodak Materials for Nuclear Physics and Autoradiography" 
(P-64), available on application. 

With improvements in sensitized materials, it is now possible to work at 
the levels of magnification given by the electron microscope 24 , 25 , 26 , 27 
and this technique offers great advantages in the field of cytology. 

REFERENCES 

1 H. F. Sherwood, Vacuum Exposure Holder for Microradiography, 
Rev. scient. Instrum., 18, Feb. 1947, pp. 80-83. 

2 R. W. Berriman, R. H. Herz and G. W. W. Stevens, A New Photo- 
graphic Material — A High Resolution Emulsion for Autoradiography, 
Br. J. Radiol., XXIII, 272, Aug. 1950, pp. 472-477. 

3 I. Doniach and S. R. Pelc, Autoradiograph Technique, Br. J. Radiol., 
XXIII, 267, Mar. 1950, pp. 184-192. 

4 T. C. Evans, Radioautographs in which the Tissue is Mounted Directly 
on the Photographic Plate, Proc. Soc. exp. Biol. Med., 64, 1947, pp. 313-315. 

5 L. F. Belanger and C. P. Le Blond, A Method for Locating Elements 
in Tissues by Covering Histological Sections with a Photographic Emulsion, 
Endocrinology, 39, July 1946, pp. 8-13. 

6 S. R. Pelc, Autoradiograph Technique, Nature, 160, 29, Nov. 1947, 
pp. 749-750. 

7 A. M. McDonald, J. Cobb and A. K. Solomon, Radioautograph 
Technique with C u , Science, 107, 21, May 1948, pp. 550-552. 

8 G. A. Boyd and A. I. Williams, Stripping-film Technics for Histological 
Autoradiographs, Proc. Soc. exp. Biol. Med., 69, 1948, pp. 225-232. 

9 C. O'Callaghan, G. W. W. Stevens and J. F. Wood, Suppression of 
Background on Long Exposure of Autoradiographic Stripping Film, Br. J. 
Radiol, 42 November 1969, pp. 862-863. 

10 C. Chapman-Andresen, C.r. Lab. Trav. Carlsberg, Ser. Chim., 28, 
No. 22-23, 1953, p. 529. 

9 SC-10 



1 1 M. Randaccio and G. Cortesina, Autoradiography of Histological 
Sections Protected with Collodion, Z. wiss Mikrosk., 66, No. 4, 1964, pp. 
201-209. 

12 W. Sawicki and Z. Darzynkiewicz, Folia Histochem. Cytochem., I, 
1964, p. 283. 

13 P. J. Fitzgerald, M. G. Ord, and L. A. Stocken, A "Dry" Mounting 
Autoradiographic Technique for the Localization of Water-soluble Com- 
pounds, Nature, 189, No. 4758, 7 Jan. 1961, pp. 55-56. 

14 T. C. Appleton, Autoradiography of Soluble Labelled Compounds, 
J. R. microsc. Soc, 83, Part 3, Sep. 1964, pp. 277-281. 

15 A. W. Rogers, Techniques of Autoradiography, Elsevier, 1967. 

16 M. J. Canny, High-Resolution Autoradiography of Water-soluble 
Substances, Nature, 175, No. 4663, 14 May 1955, pp. 857-858. 

17 S. R. Pelc, The Stripping Film Technique of Autoradiography, Int. 
J. appl. Radiat. Isotopes, I, No. 3, Nov. 1956, pp. 172-177. 

18 L. F. Belanger, Staining Processed Radioautographs, Stain Tech- 
nology, 36, No. 5, Sep. 1961, pp. 313-317. 

19 G. W. W. Stevens, Resolution Testing in Autoradiography, Nature, 161, 
20, Mar. 1948, pp. 432-433 and Br. J. Radiol., XXXIII, Dec. 1950, pp. 
723-730. 

20 A. Howard and S. R. Pelc, Isotopes in Medicine, Br. med. Bull., 8, 
No. 2-3, 1952, p. 132. 

21 G. L. Ada and others, Correlation of Grain Counts with Radio- 
activity ( 125 I and Tritium) in Autoradiography, Exptl. Cell. Res., 41, 
1966, pp. 557-572. 

22 G. A. Boyd and F. A. Board, A Preliminary Report on Histochemo- 
graphy, Science, 1 10, 2, Dec. 1949, pp. 586-588. 

23 H. Yagoda, Radioactive Measurements with Nuclear Emulsions, 
Chapman and Hall, 1949. 

24 S. R. Pelc, Theory of Electron Autoradiography, Journal R. microsc. 
Soc, 8 1 , Parts 3 and 4, Mar. 1963, pp. 131-139. 

25 M. M. Salpeter and L. Bachmann, Autoradiography with the Electron 
Microscope, J. Cell Biol., 22, No. 2, 1964, pp. 469-477. 

26 P. Granboulan and R. Audran, Application of Lippmann-type Emul- 
sions to Autoradiography with an Electron Microscope (in French), C. r. 
hebd Seanc. Acad. Sci., Paris, 259, 9 Nov. 1964, pp. 3201-3204. 

27 L. Bachmann and M. Salpeter, Absolute Sensitivity of Electron 
Microscope Autoradiography, J. Cell Biol., 33, May 1967, pp. 299-305- 



sc-io 10 



BIBLIOGRAPHY 

L. F. Lamerton and E. B. Harriss, Resolution and Sensitivity Considerations 
in Autoradiography, J. photogr. Sci., 2, No. 4, July/Aug. 1954, 
pp. 135-144. 

G. A. Boyd, Autoradiography in Biology and Medicine, Academic Press 
(New York), 1955. 

M. J. Canny, High-Resolution Autoradiography of Water-soluble Sub- 
stances, Nature, 175, No. 4663, 14 May 1955, pp. 857-858. 

G. Oster and A. W. Pollister (editors), Physical Techniques in Biological 
Research, Vol. Ill, Chapter 11, Autoradiography at the Cellular 
Level (by J. H. Taylor), Academic Press, 1956, pp. 545-576. 

G. Glawitsch, The Applications of Radioisotopes to Metallurgical Problems 
{Autoradiography), Z. Metallk., 47, No. 3, 1956, pp. 199-202. 

S. R. Pelc, The Stripping Film Technique of Autoradiography, Int. J. 
appl. Radiat. Isotopes, I, No. 3, Nov. 1956, pp. 172-177. 

E. B. Simmel, Notes on Technic; The use of a Past, Coarse-Grain Strip- 
ping Film for Radioautography, Stain Technology, 32, No. 6, Nov. 
1957, pp. 299-300. 

R. H. Herz, Methods to Improve the Performance of Stripping Emulsions, 
Lab. Invest., 8, No. 1, Jan./Feb. 1959, pp. 71-81. 

H. Levi and A. Nielson, Quantitative Evaluation of Autoradiograms on 
the Basis of Track or Grain Counting, ibid., pp. 82-93. 

S. R. Pelc, On the Question of Automatic or Visual Grain Counting, ibid., 
pp. 127-130. 

D. L. Joftes, Liquid Emulsion Autoradiography with Tritium, ibid., pp. 131- 

138. 
R. H. Herz, Physics and Technique of Autoradiography, Proceedings of 

IXth International Congress of Radiology (Munich 1959), 

Georg Thieme, Stuttgart, 1960. 
G. S. Park, An Autoradiographic Method Based on Tritium for Locating 

Resin Finish in Textiles, J. Soc. Dyers Colour., 76, No. 11, Nov. 

1960, pp. 624-629. 

B. M. Kopriwa and C. P. LeBlond, Improvements in the Coating Technique 

of Radioautography, J. Histochem. Cytochem, 1 0, No. 3, May 1962, 
pp. 269-284. 

C. Leymonie, Radioactive Tracers in Physical Metallurgy, Chapman and 

Hall, 1963. 

N. Bianchi, A. Lima-de-Faria and H. Jaworska, A Technique for Removing 
Silver Grains and Gelatin from Tritium Autoradiographs of Human 
Chromosomes, Hereditas, 51, 1964, pp. 208-211. 

A. W. Rogers, Techniques of Autoradiography, Elsevier, 1967. 

R. Barer and V. E. Cosslett (editors), Advances in Optical and Electron 
Microscopy, Volume 2, Chapter-Autoradiography and the Photo- 
graphic Process (by S. R. Pelc and M. G. E. Welton), Academic 
Press, 1968, pp. 151-166; Volume 3, Chapter — Assessment of 
Electron Microscope Autoradiograph (by M. A. Williams) 1969, 
pp. 219-272; Academic Press. Continued over 

II SC-10 



R. F. Bunshah (editor), Techniques of Metals Research, Volume II, Part 2, 
Chapter 20, Autoradiographic Techniques in Metallurgical Research 
(by R. H. Condit), Interscience Publishers 1969, pp. 877-952. 

M. G. E. Welton, Some Factors Affecting the Results obtained with 'Kodak' 
AR.10 Stripping Film in Autoradiography (Conditions for Develop- 
ment, and Latent Image Fading), J. Photogr. Sci., 17, 1969, pp. 157- 
161. 

P. B. Gahan (editor), Autoradiography for Biologists, Academic Press, 1972. 



Kodak Metafix, and Unifix are trade marks 



KODAK LIMITED 

Kodak Data Booklet Printed in England 

SC-10 YI3I9PDSC-I0/XWPI3/5-73 




PHOTOMACROGRAPHY 



Photomacrography covers work done at low magnification (less than 
approximately x 50), and is distinguished from photomicrography by the 
fact that, instead of a microscope, a single lens is used to obtain the mag- 
nification by working with a lens-to-film distance which is greater than 
twice the focal length of the lens. 

Since an appropriate photographic lens and a camera with a long bellows 
or suitable extension tubes are the basic units needed, no microscope is 
required. If desired, however, a microscope can be converted for this 
use by removing the eye-piece, and using a short-focus camera lens in 
place of the conventional objective. 

In any case, the following equipment is desirable for the most satis- 
factory work : a camera with a ground-glass focusing screen; a lens having 
a focal length considerably shorter than the maximum camera extension; 
some means of holding the specimen — preferably a focusing stage; and, 
for transparent subject, a focused light-source. 

MAGNIFICATION 

Since the final magnification m is dependent upon the lens and camera 
extension only, it can be calculated simply from this formula : 

v-f 
m =—jr 

where v is the lens-to-film distance; and/, the focal length of the lens. 
Thus, with a 2 inch lens and a 42 inch bellows draw, a magnification of 
x 20 is obtained. 

Most photographic lenses, when used in this technique, should be placed 
on the camera "reversed", that is, with their front elements facing the 
sensitized material. This can be done conveniently either with a camera 
which has a lens panel or an interchangeable-lens 35 mm camera may be 
used with a "reversing-ring" fitted. A high-quality enlarging lens is also 
very suitable for this work, and, again should be used "reversed" to 
obtain the best image quality. This position generally provides the best 
resolution, since the optical conditions are more nearly like those for 
which the lenses were designed. Lenses with symmetrical elements or 
lenses designed for photomacrography, such as Micro Summars, are 
exceptions and should be mounted in the normal manner. 

The lens-to-film distance — v — should be set for the required magnifica- 
tion and, if possible, locked in position. It is preferable not to alter this 
setting and to obtain the final focus by moving the specimen, or, the 
camera as a whole. This is possible when a movable, focusing stage or 
special camera-support-attachment is employed and this is particularly 
important when working in the vicinity of unit magnification (1:1). 

ILLUMINATION 

Proper control of the illumination is one of the most important factors 
affecting the quality of the photomacrograph. Tungsten-filament lamps 

Issue C Kodak Data Sheet 

SC-II 



are generally most convenient, and it is desirable to have a voltmeter and 
variable resistance, or some similar means, for controlling the intensity 
of the illumination to permit reproducible results in monochrome work; 
neutral-density filters should be used to control intensity for colour work, 
as the colour temperature of a lamp changes with the applied voltage. 

Reflected light 

Photomacrographs can also be made by reflected light of small objects, 
or small, complex, industrial mechanisms. In this case, however, normal 
photographic lighting can be used at close range, but many workers prefer to 
use one of the many forms of ring illuminant to allow for the magnification. 

Modified microscope 

The usual sub-stage condenser, even one of comparatively long focal 
length, does not provide even illumination over a large enough field for 
the average subject. Fortunately, it is usually a comparatively simple 
matter to set up a suitable illumination system, using simple condenser 
lenses. An arrangement using a single condenser lens about 4 inches 
(10 cm) in diameter is capable of producing excellent results with most 
subjects. In some cases, however, it may be desirable to use a more 
elaborate and precise system, such as that introduced by Kohler. 

The procedure outlined in the following steps is based on the use of the 
simple arrangement. 

1 The specimen is centred on the stage, and the lamp is aligned so that 
the image can be roughly orientated and focused on the ground-glass 
screen. At this point, the size and focus of the illuminating beam are 
immaterial. A mirror set up behind the focusing screen is a great help in 
this step, since the reflection of the screen can be observed from the other 
end of the equipment, from where adjustments are made most conveni- 
ently. 

2 The camera lens is stopped down completely, the specimen slide is 
temporarily removed, and the position of the lamp is adjusted until a sharp 
image of the filament is focused on the lens-diaphragm leaves; the slide is 
then replaced. The diameter of the beam should be large enough for the 
colour fringes at its periphery to be outside the limits of the field. Moving 
the condenser lens closer to, or further from, the slide makes the beam 
larger or smaller. With each movement of the condenser, the lamp posi- 
tion must be adjusted to re-focus the filament. 

3 The lens aperture is opened up partially, and the aperture that yields 
the required depth of field and resolution is found. (This may require 
some preliminary test exposures.) The use of a magnifier at the ground 
glass is of great help, and the fact that the image is very bright makes 
focusing possible at the aperture to be used. This eliminates a possible 
shift in focus that might occur if the lens were focused wide open and then 
stopped down. The procedure also permits the location of important 
details of the specimen within the limits of the depth of field. The 
desired aperture is set and then left undisturbed. 

4 By means of the procedure in Step 2, the size of the filament image is 
made just large enough to fill completely the aperture determined in Step 3. 

SC-ll 2 



At this point, it is likely that lamp adjustments alone will serve. When 
the correct illumination is achieved, the focusing screen will be of even 
brightness all over, and this can be checked with a photometer. No 
colour fringes should be apparent in the corners of the focusing screen. 

Some condensers used with the light-source may produce a greenish cast 
in records made on colour films. When this occurs, the transparencies 
made in the first test should be viewed through magenta Colour- Compen- 
sating filters to determine, approximately, the one to use to offset the green 
cast. Any specific arrangement must be calibrated by test to confirm the 
best filter to use, and also the optimum voltage and exposure. The 
methods of exposure determination described in Data Sheet SC-13 apply 
equally well in these techniques. 

BIBLIOGRAPHY 

J. H. Hammond, Macro-Photography and a Field Macro-Camera, Brit. J. 
Photogr., 101, No. 4930, 12 Nov. 1954, pp. 574-575. 

H. L. Gibson, Photomicrography of Insects, Phot. Soc. Amer. J., 25, No. 7, 
June 1959, pp. 32-37. 

D. F. Lawson, The Technique of Photomicrography, George Newnes, 

1960. 

H. L. Gibson, Magnification and Depth of Detail in Photomacrography, 
J. Photogr. Soc. Amer., 26, June 1960, pp. 34-47. 

E. J. Moynahan and C. E. Engel, Photomacrography of the Normal Skin, 

Med. Biol. Illustr., 12, No. 2, Apr. 1962, pp. 72-82. 

J. Fluegge, Photomacrography: Depth of Field Nomogram, Indust. Photogr. 
(New York), 17, No. 4, Apr. 1968, pp. 28, 29, 78-80, 82. 

H. L. Gibson, Medical Photomacrography, Med. Radiogr. Photogr., 45, 
No. 2, 1969, pp. 40-45. 

R. P. Loveland, Photomicrography, Wiley, 1970. 



SC-II 



KODAK 

is a trade mark 



Kodak Data Sheet KODAK LIMITED LONDON 

SC-II 

YI228PDSC-I l/xWPIO/4-72 



PHOTOMICROGRAPHY : CENTRING AND 
ADJUSTMENT OF APPARATUS 



It is a great advantage in photomicrography to have the apparatus 
arranged on a permanently aligned optical bench, although it is only 
necessary that the apparatus be rigid. If the base of the microscope 
can be clamped to an aligning plate, it can be removed for other work, 
and readily returned into alignment. 

Greater care must be taken in the centring and adjustment of the 
apparatus than may be necessary for routine visual inspection, as illumina- 
tion defects, such as uneven lighting, are more evident in photomicro- 
graphy. 

The exact technique of centring a photomicrographic system depends 
somewhat on the particular equipment in use, especially whether or not 
each optical unit can be separately removed and centred. A technique is 
described in detail below for the setting up of a microscope having a 
vertical axis. This system may be modified to suit individual conditions 
but careful procedure throughout the various steps should result in 
satisfactory illumination. The setting up of a horizontal arrangement is 
described on page 3. 

Centring of illuminant 

Considering the frequent situation where the light source itself and its 
condenser are carried together in a housing, it is best whenever possible 
first to centre the light source to the lens and to ensure that the plane of 
the source is perpendicular to the optical axis. This is most easily done 
by lining up, from the rear of the lamp-house, the source itself and its 
images formed by the surfaces of the lens, using a neutral-density filter to 
reduce the light intensity. Since it is not possible to see through the source 
itself, it is necessary to line up the images first horizontally and then 
vertically, or vice versa. These images can easily be differentiated from 
that formed by the glass bulb of a tungsten lamp by moving the lens. In 
case this method is impossible, the best substitute is to place a piece of 
paper against the front of the lamp condenser, focus the source on it as 
nearly as possible, and then centre this image to the lens aperture. In 
either case, turn and tilt the lamp so that the light beam falls squarely on 
the microscope mirror, and focus the beam on the plane of the sub-stage 
diaphragm. 

With the microscope, the first step is to determine its optical axis, 
usually from its mechanical axis, by determining two points on it, prefer- 
ably at its two extremes. A pinhole centring eye-piece used in place of 
the usual ocular is invaluable for determining the upper point (and also for 
other uses as discussed below) and can be obtained from the manu- 
facturers of microscopes. The determination of the lower reference point 
on the optical axis will depend on the type of microscope. If the sub- 
stage iris diaphragm is separately mounted and centred (as it is in the case 

Issue A Kodak Data Sheet 

SO 1 2 



of the so-called swing-out condensers), it forms a good reference aperture 
when closed down as far as possible. If the sub-stage diaphragm cannot 
be used alone or is centrable with the condenser and if the objectives are 
fixed in position as with a revolving nosepiece, then make this determina- 
tion of a lower reference point on the optical axis by focusing on a suitable 
test object, centring it with respect to the objective, then leaving it un- 
touched during the subsequent centring procedure. This test slide should 
contain a point recognizable at both low and high powers. The most 
convenient is a centring slide, obtainable from microscope manufacturers, 
which consists of a fine cross in the centre of several concentric circles. 

In either case, with the lower axial reference point in position, remove all 
lenses from the optical axis of the microscope. Put in the pinhole eye- 
piece which now determines the axis. Ensure that the mirror bar is in its 
central position, then twist the mirror so that the bright round image of the 
lamp condenser is centrally located with respect to the test object or by 
closing the sub-stage diaphragm around it. The correct angular tilt of 
the lamp, both vertical and horizontal, can now be accurately adjusted by 
ensuring that the image remains symmetrical as the lamp condenser is 
focused back and forth. By focusing the lamp condenser back so that the 
source of light is in focus through the pinhole eye-piece, it can be finally 
and accurately centred with respect to the lens, if it could not be done from 
the rear of the lamp-house. 

If the source of light is not mounted in a unit with a condenser, set it up 
alone and tilt the mirror at the proper angle to centre it before interposing 
the bull's-eye lens. The work will be much easier if a small hole in a 
sheet of cardboard or metal is held close to the centre of the light source if 
the latter is extended or does not form a sharp image. The correct tilt of 
the lens can be determined by equalizing the appearance of all the edges of 
the aperture image. This is most easily accomplished by placing a thin 
piece of paper or, better, a piece of ground glass in the sub-stage plane and 
observing it by looking down the microscope through the pinhole eye- 
piece. If the mirror is untouched, after centring the source, the lens will 
be centred when the image is again central. Unless an optical bench is in 
use, one type of movement of the bull's-eye lens affects all the others so 
that it may take considerable experimenting to obtain correct alignment. 

The light beam should now be focused again in the lower focal plane of 
the sub-stage condenser, which can be assumed to be that usually occupied 
by the iris diaphragm. Seen through the microscope pinhole eye-piece, it 
should be a uniformly bright disk centrally located. 

At this point the procedure will differ according to the type of micros- 
cope in use. 

Centring of objective and sub-stage condenser 

(1) Put on the stage a simple test object, such as previously described, 
unless it has already been done, or possibly the slide to be photographed if 
it is suitable for testing centring. If the microscope objectives are 
centrable, centre the test object into the optical axis as seen through the 
pinhole without an objective. 

(2) Put in a low-power objective and a low-power eye-piece. Focus on 

SC-12 2 



the test object. Centre the objective if it is centrable. Otherwise, bring 
the test point into the centre of the visual field by moving the slide. If a 
fixed condenser iris and a fixed objective do not align with the pinhole eye- 
piece, it is best to centre the test slide into the visual field. 

(3) Insert the sub-stage condenser without disturbing the mirror, if 
possible, and move it up until the disk of light is the smallest. 

(4) If the mirror has been undisturbed, centre the condenser (if possible) 
until this disk of light is central with respect to the test object. 

(5) If it was necessary to tilt the mirror in inserting the condenser, re- 
tilt it approximately correctly and close down the sub-stage diaphragm. 
Substitute the pinhole eye-piece for the ocular, and focus on the edge of 
the iris aperture as seen through the objective. Centre this aperture with 
respect to the back lens of the objective, repeatedly re-tilting the mirror to 
give better central illumination, if necessary. 

Replace the low-power ocular and use a lower-power objective than is 
to be employed later. Centre the light disk by adjusting the mirror. All 
colour fringes should be symmetrical. 

Centring of medium and high-power objectives 

(6) If objectives are centrable, substitute them without touching the 
test slide, and ensure that the centre point is in the middle of the visual 
field. In centring these, it is probably easier to centre them first in a 
preliminary way, with the pinhole ocular in the tube and the objective 
slightly above its normal focus, so that the test object can be observed. 

With fixed objectives, the higher-power objective may not have the same 
centre as the other if they were not purchased with the microscope stand. 
In such case, centre the test point (cross) with respect to the high-power 
objective by moving the test slide. Swing back the lower-power objective 
without disturbing the slide, and centre the system around this point by re- 
adjusting the mirror to centre the disk of light. If the difference is great, 
the objectives should be brought to the same mutual axis by the centring 
screws which are found on almost all revolving objective holders. 

After the specimen is on the stage and the field to be photographed has 
been selected, it is often simplest to insert the pinhole eye-piece and set the 
camera over the microscope so that the spot of light is in the centre of the 
ground glass. 

Centring of horizontal bench 

If the apparatus is of a standard commercial type obtained complete 
from one manufacturer, the simplest and easiest directions will be found 
in the pamphlet supplied by the manufacturer. 

If the camera is not attached to an optical bench, one can proceed as 
previously described but moving the whole microscope into alignment 
instead of tilting the mirror. Then the camera can be added into this 
optical axis by centring the focusing screen to the beam from the pinhole 
eye-piece as described above. 

If the apparatus is mounted on an optical bench, the bench itself should 
be carefully levelled, as should the plate on which the microscope is to be 

3 SC-12 



clamped, then centre the light-source, so that the beam of light is parallel 
and central with the bench and at the right height above it, and then inter- 
pose the microscope into this optical axis. There is usually some centred, 
unadjustable point, either the illuminant itself, or possibly the crossed 
lines in the centre of the focusing screen of the camera, which serves as a 
point of reference together with the line (and plane) formed by the optical 
bench. Some manufacturers provide a centring gauge for their hori- 
zontal apparatus. If this is not available, it is convenient to have made 
two vertical pointers on a stand fitting the bench and preferably with their 
tips in line with the horizontal optical axis. Each should have a double 
elbow with a horizontal portion extending in the opposite direction. The 
beam of light from the illuminating unit is then set into the correct vertical 
plane with the aid of the pointers or gauge. The lamp should be tilted to 
give a level light beam by ensuring that the centre of the beam is at equal 
heights from the bench at the lamp and at the other end of the bench, and 
then the beam can also be adjusted to the correct height. When interpos- 
ing the microscope, proceed as described previously for the vertical micro- 
scope, but move the whole microscope to align, since the mirror is not 
used, and centre the image or light spot on the focusing screen instead of 
looking directly through the tube. For example, when possible first put 
in the microscope with no lenses in it and align with regard to the sub- 
stage iris and pinhole eye-piece. It is far easier to align into the beam 
alternately, first the closed aperture of the sub-stage diaphragm and then 
that of the pinhole ocular, than to attempt to do both at once. 

Focusing the sub-stage condenser 

Having aligned the optical system, and with the slide to be photo- 
graphed on the stage, the next step in obtaining efficient illumination is to 
focus the condenser correctly. For this purpose, insert a low or medium- 
power objective and place a cardboard pointer against the front lens of the 
lamp condenser, or close the lamp diaphragm if it is very close to the lens. 
Ensure that the illuminant is focused in the plane of the sub-stage dia- 
phragm. Then focus the sub-stage condenser until the edge of the card- 
board or diaphragm is in focus in the microscope together with the image 
of the object. If the illuminated field is too small, substitute a longer focal 
length sub-stage condenser or unscrew the top lens of the one in use. If 
it is necessary to use a condenser of too short focal length, it is better to 
have the specimen inside the focus. 

Testing illumination and adjusting the sub-stage diaphragm 

Now insert the objective to be used and focus it. Replace the ocular 
with the pinhole eye-piece, and look down the tube at the back lens of the 
objective with the sub-stage diaphragm wide open. Unless the objective 
is an oil-immersion type, or has a greater numerical aperture than the con- 
denser in use, the back lens of the objective should be completely filled with 
light and appear as a round, evenly illuminated disk. If the objective is 
an oil-immersion type, then it is necessary to fill the space between the 
sub-stage condenser and the object slide with immersion oil to fill the 
aperture of the objective. If there are any irregularities from a perfectly 

SC-12 4 



illuminated disk, the whole arrangement should be re-examined, including 
the cover-glass thickness and tube length of the microscope. 

A somewhat unevenly illuminated disk may be obtained at wide aper- 
tures if an ordinary insufficiently corrected Abbe condenser is used, since 
all the light transmitted by it cannot be brought into focus in the same 
plane because of its great spherical error. An aplanatic condenser is 
corrected for such aberrations. 

Strictly parallel light coming from directly behind an object, as it does 
with a very small aperture in the sub-stage diaphragm, gives a pure 
silhouette effect; the image is dark and the background is bright. On the 
other hand, when the illumination comes at a high obliquity from wide 
condenser apertures, much light is diffracted and refracted from the object 
detail and sent into the objective, as in dark-ground illumination; this 
tends to make image details bright and the background dark and obviously 
reduces the contrast compared with bright-ground lighting. This effect 
is enhanced by the greater proportion of the light that is totally reflected or 
scattered by the under-side of the cover glass at high obliquities. For 
bright-ground work the aperture of the condenser should be no greater 
than that of the objective. As the sub-stage diaphragm is closed down 
beyond the maximum aperture of the objective, the component of this 
diffracted dark-ground type image beam decreases, and the bright-ground 
contrast of the image increases; at the same time, object points are repre- 
sented in the image by brighter and larger diffraction disks, so that resolu- 
tion of detail decreases. The nature of the object, and the particular 
purpose, will determine how far the diaphragm must be closed to obtain 
sufficient contrast or how far it may be closed and still resolve required 
detail. 

With this in mind the actual procedure is as follows : 

Gradually close down the diaphragm until its edges can be seen cutting 
down the diameter of the disk of light at the back of the objective. This is 
the maximum allowable aperture. Re-insert the ocular to be used and 
examine the image. Then close down the diaphragm until the necessary 
contrast is achieved, but no further. In photomicrography, some contrast 
can be gained in the photographic process. 

Removing residual flare 

Any residual flare remaining after the above adjustments have been made 
should be dealt with as follows : remove the ocular and inspect the inside 
of the microscope tube. If any reflections are seen (apart from the upper 
part of the tube covered by the ocular), these should be reduced by cover- 
ing with a matt-black surface. Velvet is excellent, and coffin paper, if 
care is taken to remove particles that sometimes fall from it on to the back 
lens of the objective. 

For best results, only the field of the specimen used in the image should 
be illuminated, since the light scattered by the object from external and 
uselessly lighted portions of the object degrades the definition in the used 
field of the image. Therefore a "field diaphragm", placed close to the 
front surface of the lamp condenser and of just sufficient aperture for its 

5 SC-12 



image to clear the field that is to be photographed, is much to be recom- 
mended. 

Correction for short ocular-film distance 

Microscope objectives are calculated to be used at a definite working 
distance, which is obtained in visual use with the real image distance at 
infinity. When used in photomicrography to project a real image at short 
distances, this working distance is increased, and there is a decrease in the 
spherical correction, known as under-correction, which is most marked 
with objectives of large aperture when used with low-power eye-pieces. 
To remedy this, first focus visually through the microscope, and then 
bring the image into focus on the ground glass by extending the tube (or 
pulling out the ocular), possibly leaving the final small adjustment for the 
fine-focus screw. The ideal adjustment, in order to focus on a close image 
plane, is to move out only the eye lens of the ocular, and with certain 
oculars this can be done. 



Kodak Data Sheet KODAK LIMITED LONDON 

SC-12 

PDSC-l2/r5WPI/l2-70 



EXPOSURE IN PHOTOMICROGRAPHY 

When a photomicrographic arrangement is put into use, it is necessary to 
make some preliminary tests to determine the correct exposure time for 
the particular type of subject being handled. A whole series of test 
exposures can be made on to one film by a normal test procedure. 

Criteria for judging exposure 

There are two criteria for judging the correctness of exposures in 
photomicrography. The better one to use in any particular case depends 
primarily on the type of film being used and, to some extent, on the 
nature of the subject. 

In general, when working with negative films, the exposure should be 
controlled to provide the best rendering of the details in the darker 
parts of the subject. This is the "minimum-brightness" criterion which 
is normally used in making negatives by either transmitted or reflected 
light. 

When reversal colour film, such as 'Ektachrome' or 'Kodachrome' film, 
is used, the exposure time should be selected to give the best rendering of 
the brightest parts of the subject. When this is done, the lightest areas of 
the resulting photomicrograph will be neither too dense nor too thin and 
the rendering of the darker details will be generally satisfactory. This is 
the "maximum-brightness" criterion. It is also useful for some black- 
and-white photomicrography by transmitted light, such as for samples of 
dust, pigments, etc., when a fixed or constant background density is 
desired in the negatives. 

The relationship between the effective sensitivity of the various photo- 
graphic materials differs somewhat, depending on which of these criteria 
is used for judging the exposure. 

In the case of the medium-contrast and low-contrast monochrome films 
or colour-negative films, the normally recommended speed can be used 
in photomicrography for those subjects for which the minimum-brightness 
criterion method of exposure determination applies. 

In the case of reversal materials, such as 'Ektachrome' and 'Kodachrome' 
films, the normal speeds are based on highlight rendering and so apply 
also when the maximum-brightness criterion is used in photomicrography. 
When the maximum-brightness criterion is used with a negative material, 
the exposure required will depend on the background density desired, and 
the gamma value to which the negative is developed, as well as on the 
sensitivity of the material. As the degree of development is increased, 
less exposure is required to produce the desired background density. 

Calculation of exposure time for different conditions 

Once the correct exposure time has been found for a particular set of 
conditions, the times for subsequent exposures of similar types of subjects 
made with the same arrangement can be calculated by taking into account 
any differences in magnification, and in numerical aperture (N.A.) of the 
objectives used, as well as changes in sensitized material or filters. 

Issue B Kodak Data Sheet 

SC-13 



The exposure time varies inversely as the square of the numerical 
aperture that is filled with light. 

The exposure varies as the square of the magnification, which depends 
on the power of the objective, the power of the ocular, and the distance 
from the ocular to the focal plane. If any of these is changed, the mag- 
nification will be changed, and this should be taken into account in 
calculating the exposure time. 

If a filter is used, it will absorb some of the light; the exposure time 
should be multiplied by the appropriate filter factor. If a different 
photographic material is used, the exposure time should be adjusted 
according to the relative speed of this material. 

If the conditions for which the exposure time was originally determined 
by test are called "standard", they can be combined with the "new" 
conditions to find the "new" exposure time as follows — 

New exposure _ i Standard N.A. \ 2 i New magnification \ 2 
Standard exposure V New N.A. I \ Standard magnification! 

The application of this formula is illustrated by the following example. 
Under the conditions discussed above as standard, a photomicrograph was 
obtained on 'Panatomic-X' Film with a 1 -second exposure at a 
magnification of 210 times, using an 8 mm, N.A.0.50 objective. A 
magnification of 430 times is desired, however, and this requires the use 
of a 4 mm, N.A.0.65 objective. The exposure time under these condi- 
tions is found as follows — 

New exposure /0.50\ 2 /430\ 2 , „ _ 
i = \0fi5 I X \9Tfi/ = a PP roxtmaie 'y 2-5 seconds 

If a filter is used, the exposure time must be multiplied by the appropri- 
ate filter factor for the film used. 



Exposure meters 

There are available many exposure meter devices designed for the 
determination of exposures in photomicrography, such as that made by 
Zeiss. In addition there are specialist automatic-exposure cameras made 
by such companies as Leitz. 



Bibliography 

New Products : Universal Exposure Meter for Photomicrography, J. Biol. 
Phot. Assoc, 21, No. 4, Nov. 1953, p. 40. 

A. C. Johnstone & E. V. Willmott, A Photoelectric Exposure Meter for 
Photomicrography, Med. Biol. Illustr., 4, Jan. 1954, pp. 20-23. 

P. Machovicz & E. W. Powell, Sensitive Inexpensive Light Meter for 
Photomicrography, Science, 120, 3 Sept. 1954, p. 394. 

SC-13 2 



R. Schenk, Methods of Determining Exposure Time in Photomicrography, 
Rontgen u. Laboratoriums Praxis, 8, Aug. 1955, pp. 205-211. 

K. E. Gibson, Some Problems of Colour-Photomicrography, The Micro- 
scope, 12, No. 6, Jan.-Feb. 1960, pp. 155-159. 

New Products — Exposure Meter for Photomicrography, J. Biol. Phot. 
Assoc, 28, No. 3, Aug. 1960, p. 127. 

G. W. White, The Visual Determination of Exposure Time in Photo- 
micrography, The Microscope, 14, Part 1, No. 1, July- Aug. 1963, 
pp. 34-36; Part 2, No. 2, Sept.-Oct. 1963, pp. 55-58. 

E. L. Tchacarof and V. Ch. Stomonyakov, Consideration of Certain 
Problems in the Determination of Exposure Times in Photomicrography, 
Mikroscopie, 18, No. 9/10, Jan. 1964, pp. 263-269. 

E. Hanhart, New Aspects of Exposure Measurement in Photomicrography, 
The Microscope, 14, No. 7, 1964, pp. 286-291. 



SC-13 



The following product names appearing 
in this Data Sheet are trade marks 

EKTACHROME 
KODACHROME 
PAN ATOM IC-X 



Kodak Data Sheet KODAK LIMITED LONDON 

SC-13 

PDSC-l3/rlWPI/l2-70 



THE PHOTOGRAPHIC ASPECTS OF 
X-RAY CRYSTALLOGRAPHY 



X-ray crystallography is of considerable value in pure and applied 
research, for by its use compounds can be identified, crystalline structures 
determined, and the effect on metals of cold working and annealing 
studied. This technique has nothing in common with the shadow- 
picture method usually referred to as radiography. 

A crystal is made up of a definite geometric arrangement of atoms, and 
the sets of regular atomic planes thus established have the property of 
diffracting X-rays. The rays are deviated from their original path and 
will form a pattern on a film suitably positioned to detect them. The 
character of this pattern is determined by the arrangement of the atoms 
within the crystal, or crystals if the specimen is polycrystalline. If a 
change is brought about in the crystalline state of a metal, by heat treat- 
ment or cold working, the change will be registered in the diffraction 
pattern. Although X-rays of all wavelengths could be diffracted by the 
crystal structure, provided the basic physical equations are satisfied, 
monochromatic radiation is generally used because this simplifies the 
diffraction patterns obtained. Moreover, the phenomenon is more 
readily understood by considering X-rays of a single wavelength; more 
complex techniques using heterogeneous radiation are then a logical 
development of the basic theory. 

Suppose that a parallel beam of monochromatic X-rays of wavelength 
A strikes a series of atomic planes, at a distance d apart, set at an angle 
9 to the beam (as in Figure 1). 




Figure 



Issue B 



Kodak Data Sheet 
SC-IS 



Consider a ray AB, reflected at B along BC, and a second ray PQ, 
reflected at Q along QBC. SB is a plane wave-front of the beam, and 
unless the path difference SQ+QB, between the two rays, is equal to a 
whole number of wavelengths, the rays will interfere at B. If, however, 

SQ+QB=n\ 
where n is a small whole number which is usually 1, the rays will reinforce 
each other at B, and a strong beam will emerge in the direction BC. 
This reinforcement will be all the greater due to the reflections from the 
underlying planes. It can be readily shown that 

SQ+QB=2dsind 
so that the condition for reinforcement is that 

n\=2dsin 8 

This equation is known as the Bragg equation, and the angle 6 
is sometimes referred to as the Bragg angle. Since all the other factors 
are known from the conditions of the experiment, the separation d of the 
diffracting planes can be calculated. The value of d is a function of the 
crystal structure, and is the separation of only one set of atomic planes. 
Other planes lying at different angles will also give diffracted beams. 
From a knowledge of the form of the crystal structure, the orientation of 
the diffracting planes can be deduced and, ultimately, the dimensions of 
the atomic lattice making up the crystal. 

Even apart from making measurements, the types of diffraction patterns 
obtained reveal much about the internal conditions, and consequently 
some techniques of crystal analysis do not go beyond the qualitative 
stage. 

METHODS OF X-RAY CRYSTALLOGRAPHY 

Laue method 

In this method, which applies essentially to the study of single crystals, 
a narrow beam of X-rays of heterogenous wavelength incident on a 




SC-15 



crystal emerges as a pattern of beams in well-defined directions relative 
to the crystal (see Figure 2); the places where these beams impinge on 
the film are revealed as diffraction spots on the developed image. The 
position of the spots is determined by the Bragg equation. Owing to the 
limitation on the value of and the constant value of d in the Bragg 
equation, it would be a matter of chance to obtain diffractions using 
monochromatic radiation. However, by using the "white", or hetero- 
geneous, radiation from an X-ray tube with a tungsten target, the crystal 
will give diffractions for all those wavelengths which satisfy the Bragg 
equation. 

Figure 2 shows the principle of the Laue method. The X-rays are 
collimated by a pinhole system into a fine beam of nearly parallel rays. 



• • ' • . • • • 

• *.•••» ' "" % •* - 

/.'• : ''. : A9'4V -• - : ?f: - 



• * * # • 
• •• . • 



Figure 3. X-ray Laue patterns. Left — silicon carbide. Right — bent lithium fluoride. 
By courtesy of the Hirst Research Centre of The General Electric Company Limited. 

This method does not lend itself readily to calculations, but useful 
qualitative information may be elicited from the diffraction patterns 
obtained. 

Rotation method 

Since a crystal is a regular arrangement of atoms in space, there are 
many atomic planes at different angles. In this method, the crystal is 
rotated at uniform speed about a vertical axis through its centre. Alterna- 
tively, it may be given a rotary oscillation about this axis; in this case 
the angle of rotation is usually limited to between 5° and 15°, and the 
angular speed is kept constant between reversals. 

Figure 4 is a diagram of a rotation camera. A beam of monochromatic 
X-rays is collimated and impinges on the rotating specimen. The 
pattern produced is usually recorded on a film held on the inside surface 
of a cylindrical cassette having its vertical axis through the centre of the 
crystal. Alternatively, a sheet of film may be placed behind the specimen, 
but it will record fewer reflections. 

3 SC-15 




Figure 4 



Powder method 

The methods so far mentioned are often qualitative and are also used 
in accurate evaluations of crystal lattice constants, but the necessity for 
always having a single crystal is a severe limitation when single crystals 
of suitable size are not available as, for example, in the study of metals, 
or when the specimen is available only in polycrystalline form. 

The Debye-Scherrer or powder-camera method overcomes these 
difficulties by using a small quantity of the sample in the form of fine 
filings or a powder. The sample is mounted in a fine glass capillary, 
or may be bonded to a fibre or flat ribbon of material transparent to 
X-rays, such as a human hair. A beam of monochromatic X-rays, 
collimated by a pinhole system, is directed at the specimen which is 
usually rotated continuously about its axis during the exposure. A camera, 
similar in construction to the type used in the Laue method (see Figure 2), 
having a flat cassette, is suitable for recording rays diffracted at Bragg 
angles (0) up to about 20°. However, greater values of 6 are often 
necessary and a cylindrical cassette or film holder is then to be preferred. 
Unlike the cylindrical holder used in the rotation method, the film and 
holder used for powder work usually takes the form of a collar or hoop 
formed of a strip of film, usually 35 mm wide and between 28 and 36 cm 
long. Figure 6 shows the construction of this type of camera; the 
specimen is arranged along the axis of the cylindrical holder. Below 
this diagram is shown an example of the type of pattern obtained on 
the film after processing. 

The powder specimen consists of randomly orientated crystals and, 
by rotating it during the exposure, reflections from a greater number 
of crystals may be utilized. As all orientations of the lattice planes 



SC-15 



Q^: 



Figure 5. Single-crystal rotation pattern about the "a" crystal axis of ethylene 

diamine tartrate. The interval between the horizontal lines of spots is a function of 

the structure-cell dimension along the axis of rotation. By courtesy of the 

Hirst Research Centre of The General Electric Company Limited. 

are possible, the diffracted rays will form cones of semi-vertical angle 
26, where 6 will have various values according to the Bragg equation. 
These cones of rays will meet the film in arcs, and for any one cone 
the distance between the intersections on opposite sides of the incident 
beam will be 4r9, where r is the radius of curvature of the film. 
The values of 6 for different fines can thus be obtained by measure- 
ments on the film. As the characteristic wavelengths of the incident 
radiation are known, the distance between the various sets of planes 
can be deduced, and hence the structure of the crystal. 

Information on many aspects of polycrystalline specimens can be 
obtained by this method. For example : — 

1 The average size of the crystals or crystallites. 

2 The degree of cold working (in metallic specimens). 

3 Phase relations in inorganic solid solutions. 

4 Structural imperfections. 




A ^ B 

)) i (ton i (( i 



Figure 6 



SC-15 



I 



■ .JHN 



\Wm 



Figure 7. Portions of X-ray powder patterns comparing iron powders of different 
ultimate crystal sizes. Top — 10 000 A. Centre — 300 A. Bottom — 50 A. By 
courtesy of the Hirst Research Centre of The General Electric Company Limited. 

Back-reflection method 

With the increasing importance of correlating X-ray examinations with 
measurements of other properties on the same or similar polycrystalline 
specimens, it became necessary to make X-ray diffraction studies of 
specimens too thick to permit the use of the previous methods, even if it 
were possible to resolve the resulting complex diffraction patterns at all 
readily. Accordingly, the back-reflection method, which is illustrated 
in Figure 8, has found considerable practical application. 

A collimated X-ray beam falls on the specimen, and the back-reflected 
cones of rays are intercepted by the film, showing after development as 
rings concentric with the primary beam. 

This method has been used for the determination of strain within a 
specimen and for crystal-size assessments, as in studies on fatigue. 

FILMS 

Direct-type X-ray films are normally used for X-ray diffraction investi- 
gations. The choice of a specific film for a particular problem will 
depend on the relative importance of film speed, contrast, and graininess. 
The following table lists those 'Kodak' X-ray films most suited for 
crystallographic use. For most work, 'Kodirex' X-ray film is recom- 
mended because it has a high X-ray speed. Where fine detail must be 
revealed, e.g., diffraction-line profiles, the separation of fine adjacent 
lines, etc., or where the image must be examined with a micro-densito- 
meter, 'Crystallex' X-ray film is recommended. This is a fine-grain film 
suitable for all work where grain size must be at a minimum, consistent 
with reasonable speed. 'Industrex' X-ray film, Type D, is intermediate 
in its characteristics between 'Kodirex' and 'Crystallex' films. 



'KODAK' FILMS FOR X-RAY CRYSTALLOGRAPHY 



X-ray Film 


Relative 
Speed 


Speed Increase 
for 7 minutes' 
Development 


Maximum Density 
to which Density- 
Exposure Relationship 
is Linear 


'Industrex' Type D ... 
'Crystallex' 


400 
200 
100 


15 per cent 
IS per cent 
35 per cent 


3.2 above fog 
3.5 above fog 
3.S above fog 



NOTE: The data contained in this table are for the average product. They should not be assumed to 
be strictly quantitative: minor deviations may be found in individual cases owing to various causes. 
For accurate work, data should be determined under the actual working conditions. 



SC-15 




Figure 8 

The film speeds quoted are based on 4 minutes' development in 'Kodak' 
DX-80 Developer (made up as recommended) at 20°C (68°F) with 
intermittent agitation (thorough agitation for 5 seconds at 1 minute 
intervals). An arbitrary speed of 100 has been assigned to 'Crystallex' 
film, and the other speeds given are relative to this figure. Also given 
in the table are the percentage increase in speed obtained by prolonging 
development to 7 minutes, and the maximum density to which the 
density-exposure relationship is linear, for each type of film. The films 
are listed in descending order of graininess. 

The diffracted X-ray beams are usually of low intensity, and lengthy 
exposures are often required even with fast films and the best technique 
unless the output of the X-ray set is high. 

In making quantitative studies of diffraction patterns it is often 
necessary to derive the relative intensities of the diffracted X-ray beams. 
It is convenient that there exists a linear proportionality between density 
and exposure (i.e., intensity) which will be seen from the table to hold 
for the films quoted up to a density of at least 3.2 above the fog level. 
However, the extent of this proportionality will vary according to the 
developing conditions and should, therefore, be determined. 

Several workers have reported that the shape of the density-exposure 
curve is independent of wavelength, at least over the range of 0.186- 
1.54A. This independence of the wavelength of the X-rays employed 
is of practical advantage in the preparation of a calibration curve for 
quantitative work, because it is unnecessary to use strictly monochromatic 
radiation for the calibration. 

Safelighting and handling 

The films listed in the previous section should be handled and processed 
by the light from a safelamp fitted with a 25 watt pearl lamp and a 'Kodak' 
Safelight Filter No. 6B (brown) for direct lighting, or a 'Kodak' 
Safelight Filter No. 6BR (fight brown) for indirect lighting. 



SC-IS 



It is often necessary to provide the film with a light-tight envelope to 
facilitate loading and operating the crystallographic camera in normal 
room fighting, where the film must be protected from light. This 
envelope must be made from a thin material of low atomic number, to 
keep X-ray absorption to a minimum, and have no marked structure. 
A gelatin filter which transmits little visible radiation may be used. 
An infra-red filter, such as the 'Wratten' No. 87, will be suitable provided 
that it is used under subdued lighting. Two thicknesses of this filter 
will be needed to ensure maximum light-tightness with the fastest films 
under subdued fighting, but this may increase the exposure required 
to an undesirable degree. Gelatin filters in large sizes are expensive and 
need careful handling if they are to remain in good condition for long. 
Black wrapping paper is usually unsuitable for this purpose because it 
often suffers from pinholes, which could give rise to spurious images on 
the film; furthermore, its structure becomes visible under soft X-radi- 
ation. Duplex paper is also likely to suffer from the latter disadvantage. 

Some sheet plastics materials, e.g., polyvinyl chloride (PVC), are 
compounds of chlorine and should not, therefore, be used for crystal- 
lographic film holders because their absorption of soft X-rays is likely 
to be high. 

The primary disadvantage of using any protective material round the 
film is that the material will absorb soft X-rays to some extent, and this 
will necessitate undesirable increases in exposure. The table below 
shows the approximate percentage increase on the exposure for un- 
protected film necessitated by the use of various protective materials. 



MATERIAL 


INCREASE IN EXPOSURE 
(APPROX.) 


'Wratten' Gelatin Filter No. 87 

Two thicknesses of 'Wratten' Gelatin Filter No. 87 


25 per cent 
70 per cent 



Because of the low intensity of the diffracted X-ray beams encountered 
in crystallography, exposures are necessarily lengthy, and increases of the 
order given above are highly inconvenient. If, however, the equipment 
is operated under the conditions of safelighting previously mentioned, 
instead of by normal room lighting, exposures can be kept to a minimum, 
because the film does not then need to be kept in a light-tight envelope. 
The use of safelighting need not hamper the operation of the apparatus 
or cause any other inconvenience. A light-tight booth of lead or some 
other protective material may be built around the X-ray set. This will 
enable the rest of the room or laboratory to be lit and used normally 
during the period of exposure. 

Sizes of film 

The British Standard sizes of X-ray film for crystallography, as laid 
down in British Standard 3490:1962, are:— 

3.5 x 28.0 cm; 3.5 X 35.6 cm; 12.5 X 17.5 cm 



SC-15 



8 



Some 'Kodak' X-ray films are supplied in some of these sizes (full 
details are available on application to the Industrial Radiography Sales 
Department of Kodak Limited at P.O. Box 66, Kodak House, Station Road, 
Hemel Hempstead, Herts.); other sizes may be required for different 
equipment. 

When a film is not stocked in one of the standard sizes, it is usually 
more convenient to obtain the film in a suitable stock size, and to cut 
this down to the required size. For example, when the required size is 
3.5x35.6 cm, sheets of film in the stock size 35x43 cm will each 
yield twelve strips. The cutting operation may be undertaken, quite 
satisfactorily, by using a rotary trimmer or an automatic or guillotine 
trimmer which has been properly adjusted for the thickness of 'Estar' base. 
A jig may be fitted to the trimmer to facilitate accurate positioning of 
the film before cutting. In order to obtain a clean edge, the film should 
be held and cut within the paper folder in which it is supplied. Great 
care is required in this operation in order to avoid kinking the film; 
this is likely to show as light or dark marks after processing. 

Processing 

Processing film used for crystallography presents no important prob- 
lems except that film-processing hangers are not made in the special 
crystallographic film sizes. However, the film may be held instead on a 
'Kodak' No. 9 Hanger Bar or a 'Kodak' Film Hanger Bar. In the 
absence of suitable photographic processing tanks, laboratory measuring 
cylinders of suitable size will serve as adequate substitutes when processing 
the long powder-camera films. If measuring cylinders are used, fresh 
developer may be used for each piece of film, thus helping to ensure 
uniform processing. 

Normally, all the X-ray films mentioned should be developed for 
4 minutes in 'Kodak' DX-80 Developer (available as a concentrated 
liquid, and made up as recommended), or for 5 minutes in undiluted 
'Kodak' D-19 (available as a packed chemical: formula in Data Sheet 
FY-2) at a temperature of 20°C (68°F) with intermittent agitation 
(thorough agitation for 5 seconds at 1 minute intervals). However, it 
may be desirable to modify these developing times or temperatures to 
suit the requirements of a particular technique (see Data Sheet XR-6). 

After development, the film should be rinsed in a solution of 'Kodak' 
Indicator Stop Bath, a solution made up according to Kodak formula 
SB-1 (see Data Sheet FY-4), or in water, and fixed at a temperature 
of 18-25°C (64-77°F) in 'Kodak' FX-40 X-ray Liquid Fixer with 
HX-40 X-ray Liquid Hardener. Alternatively, the packed chemical 
Kodak 'Unifix' Powder may be used, or a solution made up according 
to Kodak formula F-5 (see Data Sheet FY-4). 

For the best results and the most efficient fixing, use two successive 
fixing baths. Clear the film of all milkiness in the first bath, and drain 
back for 5 seconds. Then fix in the second bath for the same time as 
was needed in the first, and drain back for 5 seconds. When the first bath 
fails to clear the film in less than twice the time taken to clear in a fresh 
bath, replace the first bath with the second bath, and make up a fresh 
second bath. Repeat this procedure until the first bath has been replaced 
four times, i.e., 5 sets of first and second baths have been used to their 

9 SC-IS 



capacity. Then discard both baths and restart with a fresh pair of baths. 

If a single fixing bath is used, fix for twice the time taken to clear. 
Discard any fixing bath when it fails to clear the film in less than twice 
the time taken to clear in a fresh bath. 

For moderate-term storage requirements — up to approximately 10 years 
— the processed film should be washed for 10 minutes at 18-24°C (64- 
75°F), in running water which is being changed at a minimum rate of 
4 changes per hour. Under the same conditions, films which are required 
to be kept for longer storage periods should be washed for 20 minutes. 
At lower temperatures, or with less efficient washing equipment, these 
times may have to be increased considerably. When a low degree of 
permanence is acceptable, e.g., when the film is to be kept for only a 
very short period, these times may be reduced; under these circumstances, 
only a brief rinse may be adequate. Full details of the recommendations 
necessary to ensure permanence may be found in Data Sheet XR-5. 

The risk of drying marks may be obviated, and drying hastened, by 
rinsing for approximately 30 seconds in Kodak 'Photo-Flo' solution, at 
the dilution recommended. The film should then be hung to dry in a 
dust-free atmosphere. It is important that dimensional changes due 
to processing be determined, since such changes could have a marked 
effect on the results of quantitative analyses. Most powder methods 
incorporate self-calibration to facilitate correction for such changes. 
'Estar' base has a high dimensional stability, and a detailed account of 
the dimensional stability of photographic film is given in Data Sheet 
RF-10. 

ELIMINATION OF IMAGE PARALLAX EFFECTS 
ON DOUBLE-COATED X-RAY FILM 

The films described on page 6 are all double-coated X-ray films. The 
parallax associated with an image on such a film is valuable in some 
applications of X-ray crystallography, e.g., tests on the degree of annealing 
of metals, but in many cases this effect can be objectionable. In these 
latter cases it is necessary to use only the image in one of the emulsion 
layers, usually that which was towards the incident radiation. There are 
two basic techniques for eliminating one of the images. Either one 
emulsion layer may be removed after processing, or one layer may be 
protected from developer action and subsequently fixed out. 

Removal of one emulsion layer from double-coated film 

This technique is best employed after the film has been processed; 
the film may be either wet or dry. The emulsion layer to be removed 
is usually that which was away from the incident radiation because it 
contains the weaker image. 

A small quantity of a 10 per cent solution of sodium hydroxide (caustic 
soda) should be poured into a flat-bottomed dish. A clean piece of lint- 
free blotting paper, such as 'Fotonic' Photographic Paper, somewhat 
larger than the piece of film, should be lowered on to the solution. The 
quantity of solution should be just sufficient to moisten the blotting paper 
thoroughly and leave a thin film of excess solution on its surface. The 
piece of film should then be lowered carefully on to the blotting paper 
from one end, allowing the liquid meniscus to travel along the film 

SC-15 10 



without the formation of air bells. Should any air bells be formed, the 
film should be raised and lowered gently as before; it is essential that 
the emulsion surface to be removed is evenly wetted all over by the alkaline 
solution. Provided that the quantity of solution is not excessive, there 
will be no tendency for the solution to creep on to the emulsion layer 
which is to be retained. However, with films having a central punched 
hole, such as those employed in the back-reflection method and some 
powder methods, it is advisable to cover the hole with a piece of water- 
proof adhesive tape on the top side of the film to ensure that seepage 
does not occur. 

Once the film has been laid down on the blotting paper it should be 
left in order to allow the alkaline solution to attack the gelatin of the 
emulsion; this will take at least 10 minutes and may take longer. The 
exact time taken for the emulsion layer to disintegrate will depend on the 
inherent hardness of the emulsion and on whether or not a hardening- 
fixing bath was used. The emulsion of wet film will disintegrate more 
quickly than that of dry film, because more rapid diffusion of the alkali 
into the emulsion is thereby facilitated. It is important that the film be 
left for long enough at this stage, and should not be disturbed. A little 
practice using scrap film will indicate the correct duration of this step. 

The disintegration of the unwanted emulsion layer can easily be 
recognised because the black image breaks down and diffuses throughout 
the emulsion rather in the same manner as a drop of ink which has fallen 
into water. The corner of the film is then gently raised with a spatula 
or knife blade and the whole film raised in the same manner as it was 
lowered. Most of the image will remain on the blotting paper, and that 
remaining can be swabbed off in running water. The film should be 
rinsed carefully until it no longer feels soapy to the touch, although a 
more reliable method is to neutralise any remaining alkali by immersing 
the film in an acid stop bath or an acid fixing bath which should then be 
discarded. If a non-hardening fixing bath was used initially, in order 
to facilitate the removal of one emulsion layer, it is desirable to immerse 
the film in an acid hardening-fixing bath to toughen the remaining 
emulsion. The film should then be washed according to the recom- 
mendations given on page 10. 

An alternative to the use of the above method is to fix the film to a 
sheet of glass with waterproof adhesive tape and to swab off the emulsion 
with cotton-wool saturated with the alkaline solution. However, this 
method cannot readily be employed when the image completely fills the 
film area. 

A 2.8 per cent solution of potassium hydroxide (caustic potash) may 
be used instead of sodium hydroxide. Both these chemicals are caustic 
alkalis and care should be taken to prevent them from coming in contact 
with bare skin or clothing. However, their use is preferred to that of 
sodium hypochlorite because the latter is more harmful to the skin, smells 
unpleasant, and is messy to use. 

The only disadvantage of this technique is that removal of one emulsion 
layer is liable to cause the film to curl. Whilst the degree of curling is 
relatively small with small pieces of film, it may be undesirable with 
larger films. 

II SC-15 



Prevention of developer action on one side of 
double-coated film 

The techniques described below have the advantage of not giving rise 
to excessive curling of the film after treatment. 

Procedures for Large Films : The film to be processed should be fixed on 
to a supporting sheet, by means of waterproof adhesive tape, with the 
unwanted emulsion layer in contact with the sheet. The supporting sheet 
may be a discarded piece of film or a glass sheet, and should be the same 
size as, or larger than, the film to be processed. Alternatively, when 
several sheets of film are to be processed, it may be preferable to tape 
them together in pairs with the unwanted sides together. The processing 
procedure is then carried out normally, and after the outside layers have 
been cleared in the fixer, the sandwich can be separated by stripping off 
the tape or cutting the films apart. Fixing is then continued until both 
sides of the film are properly fixed. The film should then be washed 
and dried as described on page 10. 

These procedures are suitable where image areas are small by com- 
parison with the size of the film used; they are unsuitable when the 
image area completely fills the film. 

Procedure for Small, Narrow Films : The side carrying the unwanted image 
may be protected from the developer by covering it with waterproof 
adhesive tape of sufficient width. 

BIBLIOGRAPHY 

K. Lonsdale, Crystals and X-rays, Bell, 1948. 

A. Guinier, X-ray Crystallographic Technology, K. Lonsdale (editor), 

Hilger and Watts, 1952. 
H. P. Klug and L. E. Alexander, X-ray Diffraction Procedures, Wiley, 

1954. 
A. Guinier, Theorie et Technique de la Radio-Cristallographie, Dunod, 

Paris, 2nd edition, 1956. 
H. S. Peiser, H. P. Rooksby, and A. J. C. Wilson (editors), X-ray Dif- 
fraction by Polycrystalline Materials, Chapman and Hall, 1960. 
R. W. M. D'Eye and E. Wait, X-ray Powder Photography in Inorganic 

Chemistry, Butterworth, 1960. 
N. F. M. Henry, H. Lipson, and W. A. Wooster, The Interpretation of 

X-ray Diffraction Photographs, Macmillan, 2nd edition, 1960. 
C. W. Bunn, Chemical Crystallography, Oxford, 2nd edition, 1961. 
A. Taylor, X-ray Metallography, Wiley, 1961. 
W: H. Bragg and W. L. Bragg (editors), The Crystalline State, Bell, 

Volume I, 1962; Volume II, 1962; Volume III, 2nd edition, 1957. 
Ionising Radiations : Precautions for Industrial Users, Department of 

Employment and Productivity, H.M. Stationery Office, 1969. 
Code of Practice for the Protection of Persons Exposed to Ionising Radiations, 

Department of Health and Social Security, H.M. Stationery Office. 



Kodak, and product names quoted thus — 'Unifix' — are trade marks 



Kodak Data Sheet KODAK LIMITED LONDON 

SC-15 

PDSC-l5/xWP9i/9-7l 



DOCUMENT COPYING 



CONTENTS EDITION 

DC-I Photographic Copying of Documents Issue H 

DC-2 Stabilization Processing Techniques Issue C 

DC-4 The Diffusion-Transfer Process using KODAK Issue C 
'Instafax' CT Materials 

DC-5 'Instafax' Offset Materials Issue 6 



Associated Data Sheets in this or other volumes or sections 

1, GN-I Copying Photographs and other Illustrations 

2, IN-5 Photography in the Drawing Office 



Kodak and Instafax are trade marks KODAK LIMITED LONDON 

YI276PDDB-23/xWP9i/4-72 



PHOTOGRAPHIC COPYING OF DOCUMENTS 



Photographic methods for the reproduction of documents interest 
industrial, commercial, government, medical, and research organizations, 
including offices, and every type of library, whether university, public, 
business or private. The methods available fall under two main headings 
— Contact Copying and Camera Copying, and these are described separ- 
ately in this Data Sheet. Information concerning document copying with 
'Kodak' copiers may be found in Data Sheet IN-5, Photography in the 
Drawing Office. 

CONTACT-COPYING METHODS 
Transmission printing 

The method of printing by transmission is similar to that of making a 
simple contact print. The original is held in contact with the document 
paper and the combination is exposed in such a way as to allow the light 
to penetrate to the document paper after it has passed through the original. 
Translucent originals may be copied provided they are printed or written 
only on one side of the paper. 

NOTE : Both methods of transmission printing described below can also 
be used to produce direct positives when using 'Autopositive' paper 
(see page 3). 

Preparation of Negative Copies : By the correct arrangement of original and 
document paper, there can be obtained either a right-reading negative 
copy, (as in Figures 1 or 2, according to the thickness of the document 
being copied), or a laterally reversed negative copy, of superior definition, 
from which positive prints can later be taken. The laterally reversed 
negative is made by using the order shown in Figure 2, but with the 
document paper reversed, i.e., with the emulsion of the document paper 
in contact with the face of the original. In Figures 1 and 2, the shading 
indicates the emulsion side of the paper. 



DOCUMENT PAPER 

L 



DOCUMENT PAPER 




DIRECT READING y 
NEGATIVE COPY ' 




DIRECT READING 
NEGATIVE COPY 



Figure I Arrangement when original 
is thinner than document paper 



Figure 2 Arrangement when original 
is thicker than document paper 



Preparation of Positive Copies from Master Negative: This procedure is 
merely one of simple contact printing, in which there is no necessity to 



Issue H 



Kodak Data Sheet 
DC- 1 



use a yellow screen. The emulsion side of the mirror-image master 
negative is placed in contact with the emulsion side of a sheet of document 
paper and the exposure is made through the negative. This produces, 
upon processing, a right-reading positive copy of the original, which will 
be sharper than the right-reading negative copies. 

Reflex printing 

The technique of reflex printing can be used with any type of original 
whether opaque or translucent, single-sided or double-sided, and is 
indeed the only contact-copying method applicable to opaque or double- 
sided originals. 

The original to be copied is brought into contact with the sheet of 
document paper and is exposed through the back of this paper, as shown 
in Figure 3. The light is reflected back from that part of the surface of 
the original which is white, or light in colour, but is absorbed by those 
parts which are black — little light is reflected from these; see figure 4. An 
image is thus produced which should vary from very light-grey to a dense 
black. 



DOCUMENT PAPER 




Figure 3 Arrangement for reflex copying Figure 4 Principle of reflex copying 

The reflex copy, when taken direct from the original, will be laterally 
reversed, and this mirror-image negative is normally used to provide 
positive right-reading copies simply by placing its surface in contact 
with another sheet of document paper, and printing and processing as 
described above under "Preparation of Positive Copies from Master 
Negative". The copy then produced is similar to the original in tone, is 
direct reading, is sharp, and is, of course, the same size. 

It is also possible to produce direct positives by the use of Kodagraph 
'Autopositive' papers (see below). The normal reflex method produces a 
laterally reversed positive which has to be reprinted on another sheet of 
'Autopositive' paper to give a right-reading positive. However, right- 
reading positives can be made in one stage by the following method, 
using 'Autopositive' paper on a micro-thin, ultra-thin or translucent base. 
A 'Kodak' Flexible Filter S00/1.D (white opal)* is essential for best 
results. The filter, the document paper, and the original are placed 
in the printer in the following order, with the filter nearest to the light- 
source : 

* When this filter is used on a printer which does not incorporate a yellow screen, it is necessary 
to use the 'Kodagraph' Sheeting, yellow in addition. 



DC- 1 



1 Flexible Filter SOO/l.D (white opal). 

2 A sheet of 'Autopositive' paper with its emulsion side towards the 
light-source. 

3 The original with the side to be copied facing the light-source. 

All three items are held in close contact during exposure. This method 
has the advantage that the exposure time for documents of similar 
colour is independent of the thickness of the document. It gives slightly 
lower contrast and is, therefore, recommended for copying documents in 
which character density varies greatly, e.g., black type with pencil 
annotations. 

Direct-positive printing 

The preparation of positive copies without the need for an inter- 
mediate negative stage can be accomplished by the use of 'Autopositive' 
paper. This paper is manufactured in such a way that subsequent 
exposure to yellow light, instead of producing a density, has a lightening 
effect and indeed, if a sufficient exposure is given, no density will be 
visible upon development of the paper. A sheet of 'Autopositive' 
paper taken straight from a packet under the appropriate lighting con- 
ditions, and developed without any exposure having been given, will 
produce a heavy black uniform density and, conversely, a uniform and 
sufficient exposure to yellow light prior to development will show a mini- 
mum density when the paper is developed. It will be seen, therefore, 
that by the use of 'Autopositive' papers exposed through 'Kodagraph' 
Sheeting, yellow, positive copies can be made direct from originals, by 
either the transmission or reflex method, and this paper is strongly 
recommended when only comparatively few copies are required from one 
original. 'Autopositive' papers are also suitable for making positive 
"intermediates" for the production of further positive copies on dye-line 
paper. 

'Autopositive' papers are inherently slow, being considerably slower 
than the 'Kodagraph' contact papers previously mentioned, and can be 
used in normal room fighting. Care should be taken to ensure that the 
exposure is sufficient : over-exposure produces too light a result, while 
under-exposure produces too dark a result. This inversion of the normal 
factors governing exposure should be borne in mind when initially assess- 
ing the exposure by trial. 

'Autopositive' and 'Kodagraph' papers may be dish processed. How- 
ever, these papers are equally suitable for processing in automatic machines 
which are particularly to be recommended where time and space are 
important factors. There are two basic types of automatic processor — 
the immersion type and the surface-application type. In the former type, 
the paper is automatically passed through developing and stabilizing 
baths, and then through a pair of rollers which squeegee the print dry. 
Papers on a micro-thin base are not recommended for use with immersion- 
type processors. With surface-application processors, e.g., the 'Kodak' 
Auto-Processors, rapid treatment is possible. Because the processing 
solutions are spread in a very thin film only on the emulsion surface, the 
paper base is not saturated with solution, and the print dries more quickly. 

3 DC- 1 



Papers on a micro-thin base are suitable for processing in this type of 
equipment. 

Two Kodagraph Papers, 'Super-K' Contact Paper KC5 and 
'Super-K' Projection Paper KP5, have been specially designed for 
processing in immersion processors of the develop/fix type, such as the 
Kodak 'Supermatic' Processor, Model 242. 

Sensitized materials and equipment 

Photographic document papers, suitable for contact copying, should have 
light weight and a high light transmission. The emulsion should be of 
fine grain and high contrast, and preferably should be suitably sensitized to 
allow the use of yellow printing screens in some techniques, such as 
the copying of old or yellowed originals. There are several 'Kodagraph' 
papers of various speeds, bases and surfaces, and one 'Kodagraph' film 
especially for contact copying. Both papers and film may be handled 
under bright yellow safelighting. Another series of papers manu- 
factured specifically for document copying are the Kodagraph 'Auto- 
positive' papers. Details of these papers and their use may be found 
on page 3 under the heading "Direct-positive printing". 

There are available many commercial items of equipment suitable for 
exposing document copying materials. They consist essentially of a box 
containin