From the collection of the
z n
z ._ m
o Prelinger
v jjibrary
t
San Francisco, California
2007
JOURNAL <?
OF THE SOCIETY OF
MOTION PICTURE ENGINEERS
INDEX VOLUME XIV
CLASSIFIED INDEX, VOL. XIV
Absorption, Optical. (See OBJECTIVES.)
Absorption of Sound. (See ACOUSTICS.)
Acoustics, Studios.
Acoustic Control of Recording for Talking Motion Pictures, J. P. MAXFIELD,
p. 85.
Acoustics, Theaters.
Some New Aspects of Reverberation, KDWARD W. KELLOGG, p. 96.
Theater Acoustics for Sound Reproduction, S. K. WOLF, p. 151.
Apertures.
Camera and Projector Apertures in Relation to Sound-on-Film Pictures, LESTER
COWAN, p. 108.
The Aperture Effect, ELLSWORTH D. COOK, p. 650.
Arcs, Projection.
Characteristics of High Intensity Arcs, D. B. JOY and A. C. DOWNES, p. 291.
Arcs, Studio. (See ILLUMINATION IN PHOTOGRAPHY.)
Artistic Considerations.
Rectangle Proportions in Pictorial Composition, LOYD A. JONES, p. 32.
Art and Science in Sound Film Production, JOE W. COFFMAN, p. 172.
Blooping Patches. (See SPLICING.)
Camera Accessories.
Film Numbering Device for Cameras and Recorders, M. W. PALMER, p. 327.
Cameras and Camera Mechanisms.
Camera and Projector Apertures in Relation to Sound-on-Film Pictures,
LESTER COWAN, p. 108.
Camera Mechanism, Ancient and Modern, ARTHUR S. NEWMAN, p. 534.
Committee Reports.
Report of Standards and Nomenclature Committee, October, 1929, p. 122.
Progress in the Motion Picture Industry. Report of the Progress Committee,
p. 222.
Theater Lighting, Report of Theater Lighting Committee, November, 1929,
p. 441.
Report of Projection Committee, October, 1929, p. 444.
Annual Report of the Treasurer of the Society, p. 578.
Development of Motion Picture Film.
A Quick Test for Determining the Degree of Exhaustion of Developers, MERLE
L. DUNDON, G. H. BROWN, and J. G. CAPSTAFF, p. 389.
Electrical Machinery and Equipment.
Elimination of Commutator Ripple from Direct Current Generators, O. K.
BUCK and J. C. ALBERT, p. 399.
1
2 INDEX
Filters, Electrical. (See ELECTRICAL MACHINERY AND EQUIPMENT.)
Fixing of Motion Picture Film.
A Method of Testing for the Presence of Sodium Thiosulfate in Motion Picture
Films, J. I. CRABTREE and J. F. Ross, p. 419.
Some Properties of Chrome Alum Stop Baths and Fixing Baths, J. I. CRAB-
TREE and H. D. RUSSELL, Part I, p. 483; Part II, p. 667.
General.
A Milestone, p. 2.
Our New Journal, p. 7.
The Sound Film Situation in Europe, N. D. GOLDEN, p. 11.
The Human Equation in Sound Picture Production, TERRY RAMS AYE, p. 219.
A Year of Sound, HAROLD B. FRANKLIN, p. 302.
The Academy of Motion Picture Arts and Sciences and Its Service as a Forum
for the Industry, FRANK WOODS, p. 436.
Historical.
The Early History of Wide Films, CARL Louis GREGORY, p. 27.
Camera Mechanism, Ancient and Modern, ARTHUR S. NEWMAN, p. 534.
Home Motion Picture Equipment. (See SIXTEEN MILLIMETER EQUIPMENT.)
Illumination in Photography. (See also INCANDESCENT LAMPS PHOTOMETRY.)
Radiation Characteristics of Two Mercury Arcs, FRANK BENFORD, p. 404.
Illumination, Projectors. (See PROJECTION.)
Illumination, Theaters. (See also PHOTOMETRY.)
Theater Lighting, Report of Lighting Committee, November, 1929, p. 441.
Incandescent Lamps for Photography.
Water Cooling of Incandescent Lamps, N. T. GORDON, p. 332.
Loud Speakers.
Loud Speakers for Use in Theaters, D. G. BLATTNER and L. BOSTWICK, p. 161.
Loud Speakers and Theater Sound Reproduction, Louis M ALTER, p. 611.
Lubrication of Motion Picture Film.
The Surface Treatment of Sound Film, J. I. CRABTREE, OTTO SANDVIK, and
C. E. IVES, p. 275.
Mazda Lamps and Lighting. (See INCANDESCENT LAMPS.)
Mechanical Accessories.
Flexible Drive Shafts Their Application to Sound Pictures, J. C. SMACK,
p. 384.
Medical Photography.
Sound Films for Surgical Instruction, P. E. TRUESDALE, p. 513.
Miniatures. (See also TRICK PHOTOGRAPHY.)
Dimensional Analysis as an Aid to Miniature Cinematography, C. F. HUTCHINS,
p. 377.
Narrow Width Film. (See SIXTEEN MILLIMETER EQUIPMENT.)
News Reel.
The Modern News Reel, HARRY W. JONES, p. 204.
INDEX 3
Objectives.
Measuring the Effective Illumination of Photographic Objectives, J. HRDLICKA,
p. 531.
Optics. (See also OBJECTIVES.)
The Optical Problems of Wide Film Motion Pictures, W. B. RAYTON, p. 50.
The Optics of Motion Picture Projectors, ARTHUR C. HARDY, p. 309.
Perforation.
Film Perforation and Its Measurement, WALTER H. CARSON, p. 209.
Photometry.
A Light Intensity Meter, J. L. McCoY, p. 357.
Printers.
Curved Gates in Optical Printers, WILLIAM S. VAUGHN and FORDYCE TUTTLE,
p. 663.
Processing of Film. (See DEVELOPMENT FIXING LUBRICATION.)
Progress.
Progress in the Motion Picture Industry, Report of the Progress Committee,
October, 1929, p. 222.
Projection, General Information.
Camera and Projector Apertures in Relation to Sound-on-Film Pictures,
LESTER COWAN, p. 108.
The Optics of Motion Picture Projectors, ARTHUR C. HARDY, p. 309.
Report of Projection Committee, p. 444.
Projectors, Continuous.
Apparatus Developed to Simplify Manufacture of Lens Wheels for Continuous
Projectors, ARTHUR J. HOLMAN, p. 623.
Projectors, Special Type. (See SIXTEEN MILLIMETER EQUIPMENT.)
Secretary, Reports.
Report of the Secretary, October, 1928, to October, 1929, p. 466.
Sensitometry, Methods and Instruments.
Photographic Characteristics of Sound Recording Film, LOYD A. JONES and
OTTO SANDVIK, p. 180.
A Quick Test for Determining the Degree of Exhaustion of Developers, MERLE
L. DUNDON, G. H. BROWN, and J. G. CAPSTAFF, p. 389.
Sixteen Millimeter Equipment.
A New Sixteen Millimeter Motion Picture Camera, JOSEPH A. DUBRAY, p. 427.
Sound Reproduction, Disk.
A New Synchronizing Apparatus for 16 Mm. Films with Disk Records, WM.
H. BRISTOL, p. 361.
Sound Reproduction, General Information Concerning.
Photographic Characteristics of Sound Recording Film, LOYD A. JONES and
OTTO SANVIK, p. 180.
Multiple Exposure Cinematography in Sound Pictures, WILLIAM STULL,
p. 318.
The Illusion of Sound and Picture, JOHN L. CASS, p. 323.
A New Method of Blocking Out Splices in Sound Film, J. I. CRABTREE and
C. E. IVES, p. 349.
4 INDEX
Some Aspects of a Western Electric Sound Recording System, S. S. A. WATKINS
and C. H. FETTER, p. 520.
The Aperture Effect, ELLSWORTH D. COOK, p. 650.
Sound Reproduction by Variable Width.
The Photographic Treatment of Variable Area Sound Films, J. A. MAURER,
p. 636.
Sound Studio Equipment.
Some Aspects of a Western Electric Sound Recording System, S. S. A. WATKINS
and C. H. FETTER, p. 520.
Splicing.
A New Method of Blocking Out Splices in Sound Film, J. I. CRABTREE and
C. E. IvBS, p. 349.
Spot Lights. (See ARCS, PROJECTION.)
Standardization.
Some Practical Aspects of and Recommendations on Wide Film Standards,
A. S. HOWELL and J. A. DUBRAY, p. 59.
Standards and Nomenclature.
Report of Standards and Nomenclature Committee, October, 1929, p. 122.
Standards Adopted by the Society of Motion Picture Engineers, p. 545.
Studio Equipment. (See ELECTRICAL MACHINERY AND EQUIPMENT ILLUMINA-
TION IN PHOTOGRAPHY SOUND REPRODUCTION.)
Studio Lighting. (See ILLUMINATION IN PHOTOGRAPHY.)
Synchronization.
A New Synchronizing Apparatus for 16 Mm. Films with Disk Records, WM.
H. BRISTOL, p. 361.
Television and Telephonic Transmission of Pictures.
The Development of Television and Radiomovies to Date, C. FRANCIS JENKINS,
p. 344.
Theater Design and Equipment. (See ACOUSTICS, THEATERS ILLUMINATION,
THEATERS.)
Theater Lighting. (See ILLUMINATION, THEATERS.)
Treasurer's Report.
Annual Report of the Treasurer of the Society of Motion Picture Engineers,
September, 1928, to October, 1929, p. 578.
Trick Photography. (See also MINIATURES.)
Multiple Exposure Cinematography in Sound Pictures, WILLIAM STULL, p. 318.
Tungsten Lamps. (See INCANDESCENT LAMPS.)
Waxing. (See LUBRICATION.)
Wide Pictures.
The Early History of Wide Films, CARL Louis GREGORY, p. 27.
Ki ctangle Proportions in Pictorial Composition, LOYD A. JONES, p. 32.
The Optical Problems of Wide Film Motion Pictures, W. B. RAYTON, p. 50.
Some Practical Aspects and Recommendations on Wide Film Standards.
A. S. HOWELL and J. A. DUBRAY, p. 59.
AUTHOR INDEX, VOLUME XIV
, J. C.
(and O. K. BUCK)
BENFORD, FRANK
BLATTNER, D. G.
(and L. G. BOSTWICK)
BOSTWICK, L. G.
(and D. G. BLATTNER)
BRISTOL, WM. H.
BROWN, G. H.
(and MERLE L. DUN-
DON and J. G. CAP-
STAFF)
BUCK, O. K.
(and J. C. ALBERT)
CAPSTAFF, J. G.
(and MERLE L. DUN-
DON and G. H. BROWN)
CARSON, WALTER H.
CASS, JOHN L.
COFFMAN, JOE W.
COOK, ELLSWORTH D.
COWAN, LESTER
CRABTREE, J. I.
(and C. E. IVES)
(and J. F. Ross)
(and OTTO SANDVIK
and C. E. IVES)
(and H. D. RUSSELL)
DOWNES, A. C.
(and D. B. JOY)
DUBRAY, J. A.
(and A. S. Ho WELL)
Elimination of Commutator Ripple from
Direct Current Generators
Radiation Characteristics of Two Mercury
Arcs
Loud Speakers for Use in Theaters
Loud Speakers for Use in Theaters
A New Synchronizing Apparatus for 16
Mm. Films with Disk Records
A Quick Test for Determining the Degree
of Exhaustion of Developers
Elimination of Commutator Ripple from
Direct Current Generators
A Quick Test for Determining the Degree of
Exhaustion of Developers
Film Perforation and Its Measurement
The Illusion of Sound and Picture
Art and Science in Sound Film Production
The Aperture Effect
Camera and Projector Apertures in Re-
lation to Sound-on-Film Pictures
A New Method of Blocking Out Splices in
Sound Film
A Method of Testing for the Presence of
Sodium Thiosulfate in Motion Picture
Films
The Surface Treatment of Sound Film
Some Properties of Chrome Alum Stop
Baths and Fixing Baths, Part I
Part II
Characteristics of High Intensity Arcs
A New Sixteen Millimeter Motion Picture
Camera
Some Practical Aspects of and Recommen-
dations on Wide Film Standards
6
INDEX
DUNDON, MERLE L.
(and G. H. BROWN and
J. G. CAPSTAFF)
FETTER, C. H.
(and S. S. A. WATKINS)
FRANKLIN, HAROLD B.
GOLDEN, N. D.
GORDON, N. T.
GREGORY, CARL Louis
HARDY, ARTHUR C.
HOLMAN, ARTHUR J.
HOWELL, A. S.
(and J. A. DUBRAY)
HRDLICKA, J.
HUTCHINS, G. F.
IVBS, C. E.
(and J. I. CRABTREE)
(and J. I. CRABTREE
and OTTO SANDVIK)
JENKINS, C. FRANCIS
JONES, HARRY W.
JONES, LOYD A.
(and OTTO SANDVIK)
JOY, D. B.
(and A. C. DOWNES)
KELLOGG, EDWARD W.
MALTER, Louis
MAURER, J. A.
MAXFIELD, J. P.
McCoY, J. L.
NEWMAN, ARTHUR S.
PALMER, M. W.
RAMSAYE, TERRY
RAYTON, W. B.
Ross, J. F.
A Quick Test for Determining the Degree
of Exhaustion of Developers
Some Aspects of a Western Electric Sound
Recording System
A Year of Sound
The Sound Film Situation in Europe
Water Cooling of Incandescent Lamps
The Early History of Wide Films
The Optics of Motion Picture Projectors
Apparatus Developed to Simplify Manu-
facture of Lens Wheels for Continuous
Projectors
Some Practical Aspects of and Recommen-
dations on Wide Film Standards
Measuring the Effective Illumination of
Photographic Objectives
Dimensional Analysis as an Aid to Minia-
ture Cinematography
A New Method of Blocking Out Splices in
Sound Film
The Surface Treatment of Sound Film
The Development of Television and Radio-
movies to Date
The Modern News Reel
Rectangle Proportions in Pictorial Compo-
sition
Photographic Characteristics of Sound Re-
cording Film
Characteristics of High Intensity Arcs
Some New Aspects of Reverberation
Loudspeakers and Theater Sound Repro-
duction
The Photographic Treatment of Variable
Area Sound Films
Acoustic Control of Recording for Talking
Motion Pictures
A Light Intensity Meter
Camera Mechanism, Ancient and Modern
Film Numbering Device for Cameras and
Recorders
The Human Equation in Sound Picture
Production
The Optical Problems of Wide Film Motion
Pictures
A Method of Testing for the Presence of
INDEX
(and J. I. CRABTREE)
RUSSELL, H. D.
(and J. I. CRABTREE)
SANDVIK, OTTO
(and J. I. CRABTREE
and C. B. IVES)
(and LOYD A. JONES)
SMACK, J. C.
STULL, WILLIAM
TRUESDALE, P. E.
TuTTLE, FORDYCE
(and WM. S. VAUGHN)
VAUGHN, WM. S.
(and FORDYCE TUTTLE)
WATKINS, S. S. A.
(and C. H. FETTER)
WOLF, S. K.
WOODS, FRANK
Sodium Thiosulfate in Motion Picture
Films 419
Some Properties of Chrome Alum Stop
Baths and Fixing Baths, Part I 483
Part II 667
The Surface Treatment of Sound Film 275
Photographic Characteristics of Sound Re-
cording Film 180
Flexible Drive Shafts Their Application
to Sound Pictures 384
Multiple Exposure Cinematography it
Sound Pictures 318
Sound Films for Surgical Instruction 513
Curved Gates in Optical Printers 663
Curved Gates in Optical Printers 663
Some Aspects of a Western Electric Sound
Recording System 520
Theater Acoustics for Sound Reproduction 151
The Academy of Motion Picture Arts and
Sciences and Its Service as a Forum for
the Industry 436
7OL. XIV NO - 1
JOURNAL
OF THE SOCIETY OF
MOTION PICTURE ENGINEERS
JANUARY, 1930
3 UBLISHED MONTHLY, AT EASTON, PA., BY THE
SOCIETY OF MOTION PICTURE ENGINEERS
The Society of Motion Picture Engineers
Its Aims and Accomplishments
The Society was founded in 1916, its purpose as expressed in its
constitution being, "advancement in the theory and practice of mo-
tion picture engineering and the allied arts and sciences, the standard-
ization of the mechanisms and practices employed therein, and the
maintenance of a high professional standing among its members."
The Society is composed of the best technical experts in the
various research laboratories and other engineering branches of the
industry in the country, as well as executives in the manufacturing
and producing ends of the business. The commercial interests also
are represented by associate membership in the Society.
The Society holds two conventions a year, one in the spring and one
in the fall, the meetings being generally of four days' duration each,
and being held at various places. At these meetings papers are pre-
sented and discussed on all phases of the industry, theoretical, tech-
nical, and practical. Demonstrations of new equipment and methods
are often given. A wide range of subjects is covered, and many of the
authors are the highest authorities in their distinctive lines.
Papers presented at conventions, together with discussions,
contributed articles, translations and reprints, abstracts and abridge-
ments, and other material of interest to the motion picture engineer
are published in the Journal of the Society.
The publications of the Society constitute the most complete ex-
isting technical library for the motion picture industry.
JOURNAL
OF THE SOCIETY OF
MOTION PICTURE ENGINEERS
LOYD A. JONES, EDITOR pro tern.
Associate Editors
G. L. CHANIER P. MOI,E S. E. SHEPPARD
O. M. GLUNT W. B. RAYTON J. L. SPENCB
A. C. HARDY P. E. SABINB L. T. TROLAND
Volume XIV JANUARY, 1930 Number 1
CONTENTS
Page
A Milestone J. I. CRABTREE 3
Our New Journal LOYD A. JONES 7
The Sound Film Situation in Europe N. D. GOLDEN 11
Barly History of Motion Picture Cameras for Film Wider than 35
mm CARL Louis GREGORY 27
Rectangle Proportions in Pictorial Composition . . LOYD A. JONES 32
The Optical Problems of Wide Film Motion Pictures
W. B. RAYTON 50
Some Practical Aspects of and Recommendations on Wide Film
Standards A. S. HowELL AND J. A. DUBRAY 59
Acoustic Control of Recording for Talking Motion Pictures ....
J. P. MAXFIELD 85
Some New Aspects of Reverberation EDWARD W. KELLOGG 96
Camera and Projector Apertures in Relation to Sound-on-Film
Pictures LKSTER COWAN 108
Report of Standards and Nomenclature Committee 122
Abstracts 138
Book Reviews 142
Officers 144
Committees . . 145
Published Monthly by the
SOCIETY OF MOTION PICTURE ENGINEERS
20th & Northampton Sts., Easton, Pa.
Editorial Office: 343 State St., Rochester, N. Y.
Subscription to non-members $12.00 per year, single copies $1.50. Order from
the Secretary of the Society of Motion Picture Engineers, 5th & Sussex Streets,
Harrison, N. J.
Copyright
BY THE SOCIETY OF
MOTION PICTURE ENGINEERS
PERMANENT MAILING ADDRESS OF THE SOCIETY
Engineering Societies Building
29 West 39th Street
New York, N. Y.
Papers or abstracts may be reprinted if credit is given to the Journal of the
Society of Motion Picture Engineers.
The Society is not responsible for statements made by authors.
Application pending for entry as second-class matter at the Post Office at
Easton, Pa.
A MILESTONE
The Society of Motion Picture Engineers was founded in the
year 1916 by Mr. C. Francis Jenkins for the purpose, as expressed
in the Constitution, of "advancement in the theory and practice
of motion picture engineering and the allied arts and sciences, the
standardization of the mechanisms and practices employed therein,
and the dissemination of scientific knowledge by publication." From
its inception, the activities of the Society, including the proceedings
at the semi-annual conventions, have been recorded in the Trans-
actions. The initial amount of published scientific data was of very
modest dimensions, in 1920 the size of the Transactions had increased
to 240 pages; in 1924 to 508 pages; in 1927 to 768 pages; and in
1928 to 1200 pages. Up to this period, the engineer had been re-
garded by many motion picture executives as a being very much
apart from the industry and, in fact, one of the outstanding execu-
tives admitted at a banquet tendered by the Academy of Motion
Picture Arts and Sciences to the Society in Hollywood in 1928, that
previous to that occasion he had not even heard of the Society of
Motion Picture Engineers.
The engineers had been working diligently, however, and in 1927
presented to the industry a new medium for expression, namely,
sound, which when wedded to the silent motion picture gave birth
to a new art form which, if it has not already done so, is destined
to overshadow the stage, the novel, and the short story.
Although it is little more than a year ago that the first all -talking
picture was exhibited before the Society, since that time the entire
industry has been revolutionized. Old studios have been replaced
by those having the desired acoustical properties and have been
equipped with expensive recording apparatus, while in the theater
old projectors have been scrapped for the newer sound reproducing
equipment and the "operators" of a few years ago have been re-
placed by projection engineers upon whose technical knowledge and
skill the excellence of the theater entertainment now largely depends.
It is also encouraging to note that the motion picture technician
has at last been given the spotlight and is receiving some of the
recognition which he deserves. The motion picture producers, most
3
4 A MILESTONE [j. s. M. P. E.
of whom are now also exhibitors, fully realize that the future success
of their business lies to a great extent in the hands of the technician
and are welcoming advice from scientific societies and the various
universities.
The Society of Motion Picture Engineers has contributed in no
small way to the successful accomplishment of this transition. Our
Transactions have contained the first published accounts of the
various systems of sound recording and reproducing. These papers
and the accompanying discussions have not only been a means of
educating the motion picture technician but have served as a stimulus
for new ideas.
With this new order of events, the Board of Governors of the
Society realized that by retaining the existing method of publica-
tion, the Society would not be rendering a maximum service to the
industry. In many cases, the Transactions have not been issued
until four or five months after the conventions and, owing to the fact
that the "transactions" of a society are, strictly speaking, a record
of the proceedings at the society's meetings, it has not been possible
to publish the many valuable technical papers and articles which
have appeared from time to time in the foreign press and other
scientific journals at home. Valuable technical information is being
recorded by the Deutsche Kinotechnische Gesellschaft in the
Kinotechnik, by the Societe Francaise de Photographic in the bulletin
of the society, and by the Royal Photographic Society in their
journal.
It has long been the dream of the Board of Governors to publish
a monthly journal and this dream has finally been realized in this
the first issue of the JOURNAL OF THE SOCIETY OF MOTION PICTURE
ENGINEERS. The planning of this was largely a result of the efforts of
the Journal Committee under the chairmanship of Past President
L. A. Jones, whose report is presented elsewhere in this issue. Mr.
Jones has also consented to act as temporary editor until a perma-
nent editor is appointed. The editor will be assisted by a Board
of Associate Editors but the general policy of the JOURNAL will be
determined by the Journal Committee which, in turn, is responsible
to the Board of Governors. By means of this new mouthpiece,
a minimum of time will elapse before the technical papers presented
at the conventions are available, while the reader will be kept more
closely in touch with progress in the motion picture engineering
field both at home and abroad. Moreover, since the JOURNAL is
Jan., 1930] A MILESTONE 5
available to non-members at a very nominal sum, the scientific in-
formation which it contains will be more widely distributed among
the many technical workers in the industry. Although the make-
up of this, the initial issue, is very much along the lines of the Trans-
actions, bigger and better Journals are in store.
An important matter upon which the success of the JOURNAL, will
largely depend is the securing of the necessary income to provide
a permanent editor who will also act as assistant secretary and treas-
urer with permanent headquarters in New York City. To date, the
routine work attached to the various offices such as Secretary, Treas-
urer, Chairman of Publications Committee, etc., has been a labor
of love and the burden has been valiantly carried by a few loyal indi-
viduals and firms. In order to give the various firms and corpora-
tions an opportunity to share the expense of carrying on the routine
business of the Society and the publication of the JOURNAL, the Board
of Governors has established three classes of sustaining memberships,
the subscriptions for which are $1000, $500, and $100. The various
companies will be approached by the chairman of the Solicitations
Committee, Mri B. P. Curtis, and I urge every member to use his
influence to prevail upon his company to take up one or more sustain-
ing memberships.
The motion picture engineer has a Herculean task to perform for
the future. The quality of sound reproduction must be improved
if the sound motion picture is to maintain its hold on the public
as an entertainment medium. The scope for technical advance
in the field of color motion picture photography is almost unlimited.
For the immediate future, the definition or sharpness of color motion
pictures must be made at least equal to that of the black and white
picture if the public is to remain interested. Also, few of the many
problems in connection with the enlarged motion picture screen are
as yet solved. Will a wide film be ultimately necessary for the suc-
cessful showing of a large screen picture? This question can only
be answered by extensive research. Moreover, to date, no truly
stereoscopic motion pictures have been projected without the use
either of auxiliary devices by the observer or of apparatus too com-
plicated to be practical. The three-dimensional picture will probably
not emanate from one man's brain but will be the result of a combi-
nation of effort on the part of many workers.
The new JOURNAL OF THE SOCIETY OF MOTION PICTURE ENGINEERS
is destined to play a very important part in the solution of these and
6 A MILESTONE
other problems if only by virtue of the resulting stimulation of ideas
among its readers and the greater facilities which it will provide for
cooperative effort. Its publication represents an important mile-
stone in the progress of the Society.
J. I. CRABTREE, President
OUR MONTHLY JOURNAL
At various times during the past six or eight years it has been
suggested that the Society of Motion Picture Engineers should
publish a monthly journal in lieu of its semi-annual or quarterly
Transactions. The Board of Governors has discussed this proposal
from time to time but not until recently has it seemed wise to commit
the Society to an undertaking involving the necessarily increased
financial burden. Within the last year or so, however, the member-
ship has increased to such an extent that the Society's income is
appreciably enhanced. About a year ago, President Porter appointed
a committee to consider the desirability and feasibility of the Society
undertaking the publication of a monthly journal. The committee
was instructed to report its findings to the Board of Governors in
order that that body might take some definite action on this subject.
The personnel of the committee appointed was as follows: Messrs.
P. M. Abbott, J. W. Coffman, W. B. Cook, W. C. Hubbard, P. A.
McGuire, H. T. Cowling, and L. A. Jones, Chairman.
After making an analysis of the expense involved in the publica-
tion of a monthly journal, the Society's present and probable future
income, the desirable results to be obtained by the publication of a
monthly journal instead of its present quarterly Transactions, and
of methods which might be adopted for providing the required in-
crease in the Society's annual income, this committee prepared a
report, with definite recommendations, which was presented to the
Board of Governors at their meeting during the Toronto convention,
October 7 to 10, 1929. This report was given careful consideration
by the Board of Governors and the recommendations made by the
Journal Committee were accepted, with slight modifications. These
final recommendations are as follows:
1. That the Society undertake the publication of a monthly journal beginning
January, 1930. It is understood that this journal will replace the present Trans-
actions.
2. That the name of the journal be
THE JOURNAL
of the
SOCIETY OF MOTION PICTURE ENGINEERS
8 OUR MONTHLY JOURNAL [j. S. M. P. B.
3. That the size of the journal be the same as that of our present Transactions,
namely, 6 inches by 9 inches.
4. That the type of journal be strictly scientific or technical, carrying only
articles of the highest scientific, technical, and engineering quality, and that it
shall be kept free from semi-popular, commercial, trade, and advertising types of
articles.
5. That the contents shall consist in general of the following categories of
material:
(a) Papers read and discussed at the semi-annual meetings of the parent
society which have received the approval of the Chairman of the Papers Com-
mittee.
(b) Papers read at meetings of the local sections which have received the
approval of the authorized individual or body.
(c) Other papers offered for publication which have received the approval
of the authorized individual or body.
(d) Reprints of papers of special value and interest, these to be selected by
the editorial management from both domestic and foreign sources, including
probably translations of the outstanding contributions from foreign countries.
These papers are to be approved by the authorized individual or body.
(e) Abstracts of current scientific literature of direct interest to the motion
picture engineers.
(/) Book reviews of current publications of interest in this field.
(g) Selected patent notes (possibly).
(k) Society business, committee reports, notices of meetings, etc.
6. That editorial services be obtained to take charge of the work involved in
the publication of this journal.
7. That a class of Sustaining Memberships be established to provide the re-
quired additional income.
The present issue, No. 1, Vol. XIV, January, 1930, of the JOURNAL
OF THE SOCIETY OF MOTION PICTURE ENGINEERS is the direct result
of the Board of Governors' acceptance of these recommendations
and of its subsequent action in setting up the machinery for the
publication of this JOURNAL. The recommendations of the com-
mittee contain in condensed form fairly complete information as to
the style and character of the JOURNAL, of which this is the first issue.
However, it may not be out of place at this time to enlarge somewhat
upon these rather concise and formal statements in order that the
membership as a whole may have a more definite conception of the
ideals which exist in the minds of the Board of Governors as to the
future quality and character of this publication.
While the Transactions of the Society as they have appeared
during the past fifteen years have served admirably as a medium
for the publication of papers presented at our semi-annual conven-
Jan., 1930] OUR MONTHLY JOURNAL 9
tion, there is little doubt that the great majority of members will
agree that the decision to publish a monthly journal represents a
distinct step forward in the growth and evolution of our organization.
It seems quite certain that a publication reaching the membership
at regular monthly intervals will be more valuable and will better
serve to keep alive the interests of the members of the Society in
its welfare than issues of Transactions appearing at more or less
irregular intervals. It should be remembered also that so long as
our publications were appearing under the title Transactions, we
could not logically include in these publications any papers which
were not presented, or business which was not transacted at one of
our semi-annual meetings. A monthly journal suffers no such
limitation. The subject matter which can be brought to the atten-
tion of Society members and non-member subscribers through such
a medium is at once increased in its scope. We feel, therefore, that
the JOURNAL when fully developed will be of immensely greater
value and interest.
There has been considerable discussion relative to the most de-
sirable size in which to publish this new JOURNAL. The final decision
to adopt the dimensions 6 inches by 9 inches was reached from a
consideration of two factors. Our old Transactions were of this size
and doubtless many members have preserved these in the form
of bound volumes. Future volumes of the JOURNAL can therefore
be bound uniformly with the Transactions and thus retain continuity
of external appearance. Moreover, by far the greater number of
purely technical and scientific journals appear in sizes of approxi-
mately these dimensions. It seemed to the committee, therefore,
that the publication of the JOURNAL in this size will tend to identify
it as a purely technical journal and to set it apart, in physical ap-
pearance, from the more commercial or trade journal type of publica-
tions.
The fourth item of the committee's recommendations is a general
statement as to the type of subject matter to be published. The
committee and the Board of Governors are unanimous in agreeing
that every effort must be made to keep the JOURNAL on the highest
possible technical plane. The Society of Motion Picture Engineers
has, during the past years, earned the respect and esteem of the
motion picture industry largely through the high quality of its
Transactions and its freedom from any taint of commercialism. Our
new JOURNAL must be in harmony with this reputation, for this
10 OUR MONTHLY JOURNAL
reputation is one of our most valuable assets and must be safeguarded
at all costs.
In the fifth item of the recommendations an attempt has been
made to outline the content of this JOURNAL. These statements
seem to be adequate and need no further explanation.
We cannot, of course, expect this JOURNAL to appear fully grown
and developed in its initial issues. It will take considerable time
and a great deal of hard work on the part of the editorial staff to
bring it into a fully developed form. Moreover, it probably will not
be found advisable to fix rigidly the relative proportion of the various
types of material in each issue. For instance, it may be desirable
in the issues appearing simultaneously with and soon after each of
our semi-annual conventions to devote by far the largest percentage
of space to the publication of convention papers. As this source of
material is exhausted more space can be given in subsequent issues
to contributed material, translations of foreign papers, abstracts,
book reviews, etc. This problem of proportioning space to the
various departments, which it is hoped will become regular features
of the JOURNAL, is one which will have to be worked out as time
goes on.
It will be noted that the seventh item relates to the provision of
additional income to meet the financial burden of publishing the
monthly JOURNAL. The Board of Governors at the present time is
giving this matter attention. The outcome of the effort to increase
the income of the Society will determine whether it will be feasible
to secure part-time or full-time editorial services for the JOURNAL.
In the meantime the Chairman of the Journal Committee has
agreed to act as editor pro tern. Every effort will be made to publish
this JOURNAL in a manner creditable to the Society. Suggestions,
advice, and constructive criticism will be welcomed.
LOYD A. JONES, Chairman of Journal Committee,
Editor pro tern.
SOUND MOTION PICTURES IN EUROPE
NATHAN D. GOLDEN*
In selecting this subject I may be taking many of you over familiar
territory. Nevertheless I have chosen "Sound Motion Pictures in
Europe," because I regard it as the outstanding problem confronting
American exporters of motion pictures today.
The advent of sound pictures has given rise to many conjectures
as to how American made sound and talking pictures are being
received in foreign countries, how the talkie will affect our export
markets, and how the language problems abroad will be solved.
An attempt to answer these questions is the purpose of this paper.
Before going into that phase of the subject, however, it might be
well to give you an idea of our exports for the first six months of 1929
and the corresponding, period for 1928.
During the first six months' period for 1929, exports of American
motion pictures to all countries amounted to over 121,000,000 linear
feet as compared to 112,000,000 linear feet in 1928. This increase
of over 9,000,000 linear feet of American motion pictures indicates
pretty fairly that sound or talking pictures have not curtailed our
exports in this commodity, at least not up to the present time.
My first observation is that Europe still remains our most impor-
tant market and offers the greatest potentialities for sound and
dialog films, dependent, of course, upon the rapidity of sound
installations. Such installations have not been made as commonly
as might have been expected, owing to the fact that European
theater owners are confronted with the financial burden necessary
for installing the required apparatus. Relief along this line seems
to be approaching, with the recent announcement by certain large
American electric companies of a smaller apparatus and facilities for
the financing of it. This smaller apparatus, comparable with the
best makes in Europe, will serve well in the smaller theaters which
literally dot Europe.
With approximately 27,000 theaters in Europe seating about
* Assistant Chief Motion Picture Division, Bureau of Foreign and Domestic
Commerce.
11
12 NATHAN D. GOLDEN [j. s. M. P. K.
12,000,000 people, only 19 have a seating capacity of over 3000;
23 seat from 2500 to 3000; only 84 have from 2000 to 2500 seats;
267 have a seating capacity from 1500 to 2000, and 1250 from 1000
to 1500 seats each. There are more than 18,000 theaters with less
than 500 seats each. A good proportion of these barely qualify as
motion picture theaters. The average cinema capacity in Europe
is less than 480.
Let us now discuss briefly sound film conditions in the more
important European markets, beginning with Germany where the
more technical aspects of sound film production have received more
attention than in the others.
GERMAN SOUND FILM PRODUCTION
The first German sound film appeared in Germany seven years
ago as an experiment. Three years ago, the Tri-Ergon system was
much spoken of, but owing to lack of German capital its company
was compelled to exploit the patents in Switzerland.
Only in 1928, spurred by the increasing success of American sound
film activities, did Germany turn to furthering, organizing, and
financing its domestic sound film industry. The Tonbild-Syndikat
A. G. (Tobis) was then established.
The Tonbild-Syndikat was later joined by a number of smaller
companies holding various sound patents; then the leading German
electric concerns, A. E. G. and Siemens-Halske, which had worked
out a number of useful processes and had even produced some
experimental pictures, entered into action. Together with Poly-
phon-Werke A. G., they founded the Klangfilm G. m. b. H. After
several months of competition and patent war, Tobis and Klangfilm
joined their interests, Klangfilm dealing with the production and
sale of reproduction apparatus under the patent of A. E. G. and
Siemens, and Tobis producing recording apparatus under its own
patents, of which it possesses about 500, and awarding licenses for
the production of sound pictures. It has already signed a contract
to this effect with Ufa, and is preparing to exploit the same licenses
in other German speaking countries.
Agreement between Klangfilm and Ufa. The German sound film pro-
duction was actually started April 8, 1929, when an important con-
tract was signed between Klangfilm and Ufa. Under this contract
Klangfilm-Tobis is to furnish recording equipment for four large sound
studios, which are being built by Ufa in Neubabelsberg, Berlin.
Jan., 1930] SOUND PICTURES IN EUROPE 13
Ufa is now producing its first sound film in the Klangfilm studios,
and it is planning to release 22 talkies during the 1929-30 season,
under the Klangfilm system. It seems that the wiring of theaters
is keeping pace with production, for by May 1, 30 German theaters
were equipped with Tobis apparatus. The present monthly output
of Klangfilm is said to amount to 20 such installations, and it is
expected that this output will later reach 80 monthly.
Latest prices announced in Germany for Klangfilm-Tobis sound
apparatus for theaters run from approximately $3200 to $15,000,
according to the size of the installation.
German Theaters Suitable for Installation of Sound Equipment. Of
the 5200 German motion picture theaters, only a few are large
enough to install sound equipment at the present time. It may be
roughly estimated that 193 theaters with seating capacities over
1000 and approximately 700 theaters with seating capacities from
500 to 1000 offer an early market for reproducing apparatus.
One American company had installed its apparatus in five Berlin
theaters, but a permanent injunction handed down against it forced
the withdrawal of this apparatus and of the company in question
from the German market. However, negotiations are in progress
between German and American electrical concerns to bring about a
combine which will end all patent suits of the parties concerned.
German feature film production has slumped badly in recent
months. This is due to the German inability, so far, to turn out
sound films, and the native industry's fear of producing too many
silent films. Exhibit demand is irregular, and spot-booking is sought
more now than formerly, since cinema owners are afraid to contract
too far in advance for silent production. Feature imports are also
necessarily lower than last year because of the "kontingent" limita-
tions. But while some slump was due in view of the sound film
departure, a general depression was in no way expected.
Sound Film Production in Germany during 1928-29. During the
year from July 1, 1928, to June 30, 1929, the German sound film
industry produced and submitted to censorship 75 short sound
pictures totaling 17,814 meters in length, making the average length
of each sound picture about 235 meters, which comprised short
speeches, musical scenes, and similar sound experiments. Dur-
ing the same period two foreign sound features and three shorts
were censored in Germany.
The production industry is at present in a state of defense against
14 NATHAN D. GOLDEN [J. s. M. P. B.
any foreign talkie invasion. The producer is today faced with
lack of capital and because of the talkies, the possibility of marketing
German films abroad, especially in England and America, has almost
collapsed.
German producers are losing no time, however, in solving the
language problem. One producer in cooperation with an English
company, is now producing a bi-lingual talkie in England.
Censorship of Sound Pictures. Much space is devoted by the
German press to the question of sound film censorship in so far as
sound shorts are concerned. Sound features are subject to contingent
regulations and are treated as silent films. A number of American
sound shorts have already been brought on the German market
without any import restrictions. One American company, how-
ever, has recently registered 20 more short sound pictures to be
imported into Germany; but since the Foreign Trade Committee
claims that the existing regulations do not include provisions for
sound shorts, it has refused to grant an import permit for them.
At present there is under consideration by the German govern-
ment a proposal to establish a special contingent for talking pictures.
The proposal is drastic. It will allow the importation of only one
foreign talkie to every German talkie shown. Moreover, the Reichs-
rat, the governing committee representing the German States, has
recently adopted new amendments to the German cinema law.
Although these amendments are contrary to the ruling of German
courts, they subject all dialog of sound film to censorship.
All pictures disparaging Germany abroad will be banned for
exhibition, even if the German censors have passed the picture after
deleting the objectionable scenes.
It is not likely that all the new rules will become law, for they
will have to be considered by the Reichstag in about four to five
months' time.
Italian Interests in German Sound Films. It is extremely interest-
ing to follow the international aspect of the German sound film in-
dustry. It appears that Ufa's first sound pictures will be synchro-
nized musical films, intended for world distribution. As a matter
of fact, by a sound film agreement between Ufa and the Italian Ente
Nazionale per la Cinematografia, the latter's product will be released
in Germany and exhibited in all theaters equipped with Klangfilm
apparatus. On the other hand, the Ente Nazionale is reported to
have acquired the entire Ufa sound production for 1929-30, with
Jan., 1930] SOUND PICTURES IN EUROPE 15
a view to showing these pictures in properly equipped Italian theaters.
Relations with Other Countries. The German industry has a double
tie-up with Great Britain; the British Union Corporation, Ltd..
has an important share in the Polyphon Werke A. G., which is one
of the founders of the Klangfilm, and the British Photophone, Ltd.,
has a financial interest in the Tobis. There is, moreover, a Ger-
man coalition with Russia. In fact, a contract is said to have been
concluded in April between the German Prometheus A. G., the Brit-
ish Photophone, and the Russian Meschrabpon-Film, for joint
production and distribution of sound pictures, and the sale of German
and British sound apparatus for Russian theaters.
For the exploitation in other countries, a company is now being es-
tablished in the Netherlands by Dutch financial companies with Tobis
reported to be having a 25 per cent share in the capital and profits.
German sound film interests were furthered recently with the
creation of the International Talking Screen Production, Ltd., a
registered British company which acquired the entire capital of the
Filmwerke Staaken A. G. (German) and Derussa (German-Russian),
and 51 per cent of an American company.
These German sound film developments and international tie-ups
show the German industry still to be in a rapidly evolving stage, but
there does exist a possibility of such a well organized and efficiently
conducted program as to overcome the present difficulties in the
film industry, and to acquire a domination of the Continental sound
film market.
GREAT BRITAIN
In proportion to the number of theaters, sound motion pictures in
this country are progressing as rapidly as in the United States. It
is estimated that there are over 4000 theaters in Great Britain, of
which 680 have a seating capacity over 1000 and 2231 with seating
capacity ranging between 500 and 1000.
At the present time there are about 400 sound reproducing installa-
tions in the theaters of Great Britain. While this figure is small as
compared with the 6000 or more installations in the United States,
other theaters are being equipped as rapidly as the apparatus can
be received in Great Britain.
The advent of sound pictures has brought about a situation in the
quota system, unlooked for at the time of its framing. It is under-
stood that there is a movement afoot in Great Britain to repeal the
Film Act, the promulgation of which, 18 months ago, led to the
16 NATHAN D. GOLDEN [j. s. M. P. E.
formation of a number of British film companies with the object of
producing a large part of Great Britain's requirements. Had the
trade developed along expected lines, the formation of these com-
panies would have been justified, and the British industry would
have been in a thriving condition. But nobody dreamed that in
the short space of twelve months the demand for pictures would be
reduced from 700 features to 300 or 400 per year. The leading
theaters in the country have gone in for the talkies almost exclusively,
and the silent picture is fast disappearing from the British market.
Producers in Great Britain are losing no time in reorganizing their
studios and reshaping their production schedules to cope with a
situation similar to the one that existed in the United States 18
months ago, when all the producers began laying plans for the pro-
duction of sound pictures on a large scale. At the British Inter-
national Studios, at Elstree, there are ten pictures in production.
First International Pictures, a newly formed company, also has
under production its first sound picture. Gainsborough Pictures,
Nettlefold, and various other companies have sound feature films
under actual production. The Blattner sound system, which
operates differently from all others, the sound being recorded on a
metal tape, is to be used by Max Rhinehart in all his feature stage
shows. Rhinehart intends to include scenes in sound and color film
in these productions, the first of which is now in the process of pro-
duction. A new company has recently been formed to turn silent
films into synchronized form, probably with dialog. This firm has
secured a studio within easy reach of London, for which a complete
American recording apparatus has been ordered. A large number
of British and other films which are now being offered as silent fea-
tures, will thus be available in sound and talking form.
Production of talking pictures in several languages is taking on
large proportions. British press reports indicate that at the Twinck-
enham Studios ambitious plans for the making of two 100 per cent
talking pictures will shortly be under way. They will be made in
English, French, and German, the English version by an English
director, the French by a French director, and the German by a well
known German. Another press report informs us of the extensive
plans of another producer for the creation of an international talkie
studio, which is to have twenty stages, to be built near London with
the latest devices and manned by the best technicians that Great
Britain and the world can supply. It is the plan of this multi-lingual
Jan., 1930] SOUND PICTURES IN EUROPE 17
film center to produce the English version of the picture with the
the continental producers present, with whom arrangements for co-
operation are to be made. When the English version is completed
the first of these producers will bring over his native stars and make
the talking version for that country. He in turn will be followed by
another continental producer, and so on. In this way talkies for
France, Italy, Spain, Sweden, and other continental nations will be
made. By using the same story, sets, costumes, etc., and with each
of these continental producers paying his share of the expenditure,
it is felt that the cost of production of the first version will be from
30 to 40 per cent lower than for a picture made for Great Britain
and Empire distribution only; and at the same time the continental
versions will have been produced at correspondingly lower costs.
Sound Equipment. The number of British sound reproducing
apparatuses at present on the market are too numerous to mention.
Several of them have proven their interchangeability with American
sound pictures, but opinion of those in the trade is that they do
not have the quality of tonal reproduction credited to our American
devices. Prices for the various English made synchronizers range
anywhere from 195 to 3000 pounds.
FRANCE
The development of sound film in France has been at a standstill
owing to the protracted delay in settling the regulations for the
administration of the French Film Control Decree for the film release
season 1929-30. Coupled with the decision of American distributors
to withhold contracts for the 1929-30 product in view of the un-
certainty of the number of films which could be imported into the
country under the terms of the new French film regulations, the
leading American sound film equipment manufacturers, last March,
ceased making contracts for the delivery of either recording systems
or reproducing apparatus.
Demand for Sound Picture Apparatus. The fundamental demand
expressed by the theater goers themselves has already forced three
of the Boulevard first-run theaters to install sound equipment. Con-
cerning the potential demand for this equipment, however, it is safe
to predict that it will be several years before there will be as many
sound installations in France as there are in the United States at
present, in proportion to the population or to the number of thea-
ters. The majority of French exhibitors are either too conserva-
18 NATHAN D. GOLDEN [j. s. M. P. E.
live to try out this invention before their public advises them to
do so, or else the investment looks larger to them than it really is.
As regards the potentiality of reproducing equipment sales, it is
believed by those well versed in French film circles that the wiring
of a great many houses other than the so-called first-runs, will depend
upon the supply of French dialog films. Foreign talkies, either in
part or full, or the sound synchronized films, will not induce the
owners of these neighborhood and small town cinemas to invest in
expensive house wiring. Exhibition leaders in France are out-
spoken in their claims that the provincial cinema going public
generally will not tolerate the substitution of synchronized sound for
orchestral music; nor will they be expected to absorb foreign dialog
films. American super productions, however, with short dialog
sequences and box office names, and those strictly sound synchronized
in manufacture, will continue for a long while to attract capacity
audiences in French first-runs. At the present time there are about
ten theaters in France wired for showing sound pictures, and it is
estimated that there are close to 350 theaters in France with a seating
capacity over 1000, and 1300 theaters with a capacity from 500 to
1000 which are potential talkie houses.
Sound Studios. There are at present but two French studios
equipped to record sound films. These are the Menchen studio at
Epinay, just outside Paris, which is controlled by Les Films Sonores
Tobis, the French subsidiary of the Tonbild Syndikat of Germany
(Tobis) ; and the Gaumont studio in Paris.
Although it is said that plans are under way to equip for sound
film purposes the studios at Billancourt and at Neuilly, immediately
adjacent to Paris, the information is not authentic.
Recording Processes in France. While no American recording equip-
ments have been delivered in France to date, it is felt certain that,
with the settlement of the French film controversy and the re-
sumption of trade activities of American interests, several orders
for recording equipment will be placed with American companies.
The only equipment announced as available for purchase in France
is Tobis- Klangfilm. This recording apparatus is installed at the
Menchen studio, but so far nothing from this studio has been ex-
hibited. The Petersen-Poulsen system, a Scandinavian invention,
which is being fostered in France by the Gaumont Company, has
been used more extensively for short films. One feature is also
known to have been released. In this system, sound is recorded on
Jan., 1930] SOUND PICTURES IN EUROPE 19
a second film, similar to that of British Acoustics. The results have
not been satisfactory, according to the trade, and little hope is held
that the system will be much in favor. The Cinevox process is being
sponsored by a well known French producer and distributor, but
little is said about this system, except that it is for sound on the film.
It should offer no real competition for American outfits.
In view of the unsatisfactory credit conditions in film circles, and
the heavy demands made on sales of recording equipments, it is
probable that only the few larger producers will be able to contract
for the expensive American installations. So far as the numerous
smaller producers are concerned, they will be obliged either to rent
space in equipped studios or to confine their activities to silent
film production as in the past.
Reproducing Equipment. Several American companies and repre-
sentatives of Tobis, Petersen-Poulsen, Cinevox, and Melovox are in
the French market for sales of reproduction equipment. The
Thomson-Houston Company is advertising a non-synchronous re-
production device. Companies selling the Boma apparatus, Ampli-
phonaubert, Survox, Brkaphototone, and Synchrophone are reported
to be in the formative stage.
ITALY
Sound and talking movies have been introduced into this market,
and, with the exception of the language difficulties, have been well
received. Italy with more than 2000 theaters, 155 of which have
a seating capacity of 750, should offer a very fertile field for American
sound installations.
Production. Production in Italy is limited. The Ente Nazionale, a
concern aided by the government, and the Pittaluga Company are the
chief producers. The Ente, which has adopted British talking picture
apparatus, has already taken the exterior sets of their first Italian
talking picture. The making of this film has aroused considerable
interest in Italy, since it marks the government's entry into a new
field. Of all Italian producers, Pittaluga has announced the most
ambitious production schedule. Six features with sound are sched-
uled, and twenty-six shorts are under contemplation.
The progress that has been made in the United States in the
development of sound pictures has prompted various persons in the
moving picture industry in Italy to consider the possibility of utilizing
them for the production of Italian grand opera. In the making of
20 NATHAN D. GOLDEN [j. s. M. P. B.
the silent picture, Italy has had little success but sound pictures
should offer Italy an opportunity in this regard.
AUSTRIA
The prospects for sound films in Austria are not very promising,
owing to the number of small theaters. There are but 19 theaters
with a seating capacity over 750, and 53 with seating capacities
between 500 and 750, which may lend themselves to sound installa-
tions. But it is estimated that even the five largest cinemas in
Austria could not afford to pay more than $2000 to $4000 for com-
plete sound equipment and installation.
No cinema in Austria has yet been wired for sound films, but it is
planned to equip a small theater in Vienna at an early date. The
Filmton Ges. claims that it has Austrian patents on a sound film
system similar to an American system which can be fitted to any
type of apparatus with practically no difficulty or loss of time.
The Marconi-Gefra system was recently presented in Vienna; the
prices of this device range from $1500 to $4000.
Austrian interest in sound films has increased enormously within
the past few months. Already one company, Astra Film A. G. near
Vienna, has begun the manufacture of sound films on an American
system, using the disk method. Another company, Filmton Ges.
I. G., has recently been formed and production is expected to start
during the next twelve months. Back of the Filmton Ges. I. G. are
Gefra, the leading radio concern of Vienna, and the Marconi people.
Reproduction sets are at present made by Astra Film A. G., while
Gefra, which is interested in Filmton Ges. I. G., claims that it is
already making recording apparatus.
HUNGARY
Hungary has approximately 450 motion picture houses, 93 of which
are located in Budapest. Only five houses in the entire country are
capable of accommodating over 750 people, the average seating
capacity being about 300. Plans are under way in Budapest to
equip the three largest theaters in that city with reproduction sets.
With the exception of the Ufa theater, which will have a Tobis
installation, the others will be wired with American equipment.
With the scarcity of large houses, the prevailing limitations for
the immediate installation of sound equipment in Hungary are very
evident. Important as this feature may be it is not the only ob-
stacle in the way of sound pictures in Hungary. The Hungarian
Jan., 1930] SOUND PICTURES IN EUROPE 21
language is the only one spoken in this country, and this, quite
naturally, would eliminate talking pictures unless produced in the
native tongue. Sound accompanied pictures may find a market in
Hungary after installations are made in theaters with reproducing
apparatus, and leaders in the Hungarian industry feel that sound
synchronized pictures will prove popular.
At the present time none of the Hungarian studios are equipped
for the production of sound films; neither has Hungary manu-
factured any type of recording or reproduction apparatus. Owing
to the scarcity of capital, it is doubtful whether the necessary funds
could be obtained at this time to acquire or manufacture recording
apparatus in Hungary.
SPAIN
The development of sound motion pictures for the present is not
very promising in Spain. English speaking films will naturally be
barred because they would not be understood by the Spaniards.
But synchronized pictures, such as those reproducing musical scores
and sound effects, will have a future in this country. It is suggested
that as theaters in Spanish speaking countries are adapted to sound
films, there might be an opportunity for Spanish producers to supply
Spanish speaking films to those markets.
Equipment now offered in Spain is considered to be expensive,
running as high as $18,000; it is felt by those in the trade that if
these prices were brought down within reach of the Spanish exhibitors,
there would probably be room for five installations in Madrid this
year, three in Barcelona, with a possibility of one each in Bilgao,
Zaragoza, Valencia, and Seville.
Spain, with more than 2000 theaters, has nearly 300 with a seating
capacity of over 1000; 600 seating from 750 to 1000; and 450 with
a seating capacity of from 500 to 750, which should lend themselves
to sound reproduction installations. So far only one theater is wired
for the reproduction of sound films, but two others will be wired in
the near future.
None of the Spanish studios are as yet equipped for the recording
of sound pictures, and no such apparatus has been manufactured
in Spain.
CZECHOSLOVAKIA
At present five motion picture theaters in Czechoslovakia, repre-
senting a total seating capacity of 4500, are equipped with sound
22 NATHAN D. GOLDEN [j. s. M. P. E.
reproduction sets. All of these are in Prague. Two of these theaters
have American apparatus, two have German "Klangfilm" equip-
ment, and the fifth has installed a Dutch reproduction set. There
are some 40 theaters in this country seating over 750, and 368 theaters
seating from 500 to 750, which could be wired for sound pictures.
The distribution of talking films will be very limited, since the
Czechoslovak theater goers will come two or three times out of
curiosity to see and hear a talking film whose language they do not
understand, but are unlikely to attend regularly. German dialog
pictures might find a fair distribution in the territory close to the
German and Austrian frontiers inhabited by German speaking
people, provided theater owners equip their houses with reproducing
equipment.
It seems improbable that dialog films could be produced in this
country under present circumstances, since domestic production
of motion pictures suffers from lack of capital and will not be able
to afford the purchase of expensive recording apparatus. In addition,
the domestic market is rather small, and there are no export possi-
bilities for Czech talkies.
The sound film proper has better prospects, according to leaders in
the industry. It is reported that motion picture producers of
Czechoslovakia contemplate making sound films with the coopera-
tion of foreign producers, whose sound recording studios could be
used for this purpose. The Blekta Film Company is now taking
Czech sound pictures in a studio in Vienna for a film which is partly
sound synchronized.
Czechoslovakian film distributors are rather skeptical as to the
lucrativeness of the distribution of sound films in their country,
maintaining that the expensiveness of the reproducing equipment
will permit only a limited number of theaters to install the necessary
apparatus. Thus the circulation of sound films will be very restricted
and their price very high.
POLAND
No theaters as yet have been wired for the reproduction of sound
films in Poland. The situation is causing considerable perplexity
among cinema owners. They have been experiencing poor business
for the past six months and are reported to be in a very poor financial
state. Their ability to go into the sound film field, therefore, depends
chiefly on the willingness of the banks or other financiers to aid in the
Jan., 1930] SOUND PICTURES IN EUROPE 23
wiring of their theaters. If this financial backing can be secured,
probably fifty cinema owners in the large cities of Poland may
arrange for the installation of sound reproducing apparatus when
they can satisfy themselves as to how the Polish public will accept
sound pictures in a foreign tongue.
SWEDEN
According to reports sound motion pictures have met with the
approval of the Swedish cinema goer, and several additional theaters
will be wired in the near future. Sound pictures have been shown
in Stockholm since May 2, 1929, and the attendance has been un-
usually high. While there is considerable adverse criticism regarding
the talking picture, there are strong indications, at least in Stockholm,
that the public prefers the sound film to the silent. Talkies have
been limited to a few short length news reels with the exception of
one American feature. However, a great number of features have
been shown using sound effects, music, and singing.
It is estimated that there are about 1500 motion picture theaters
throughout Sweden, 25 of which have a seating capacity over 750,
but at present there are only 7 theaters in Sweden equipped for
showing sound pictures, 6 of which are located in Stockholm and
the other in Malmo. Six of these installations are of American
manufacture, while the other one is the invention of a Swedish engi-
neer. The prospects for the sale of sound equipment in Sweden
depends, to a large extent, on the initial cost and whether or not the
apparatus can be used with both American and European sound films.
Production. Sound pictures have not yet been produced in Sweden
but it is reported that the Svensk Film Industri of Stockholm intends
to produce two sound pictures during the current year. Neither
recording nor reproducing sets have been manufactured in Sweden.
The German Klangfilm sound reproducing equipment is being in-
stalled in one theater in Stockholm and in another in Gothenburg.
The Svensk Film Industri is contemplating using this system in a
number of theaters which it operates.
DENMARK
Denmark has only 270 theaters, thirty of which have a seating
capacity over 500, so it is evident that sound installations will be
comparatively limited. A few of the larger theaters have already
been wired, and it is understood that apparatus will be installed in
several more of the leading theaters later in the year. Leaders in
24 NATHAN D. GOLDEN [j. s. M. P. E.
the motion picture industry in Copenhagen feel that immediate
prospects for the general sound development are very good.
The old company, "Nordisk Film," has completely discontinued
operations, because of heavy competition with American and German
made pictures . A new company, ' ' Nordisk Tone-Film, ' ' has now been
organized. It has been producing one reel sound pictures, running
not more than from five to eight minutes in length and composed
chiefly of singing or short talks, the cast consisting entirely of local
artists.
The recording process now in use is the Petersen-Poulsen system
of Danish make. This system differs greatly from that of the
American recording process, the picture being made on one film and
the sound on another, but they are so arranged that the result is
perfect synchronization. With the present apparatus it would be
impossible to use sound films of any other process, owing to the fact
that two separate sets of apparatus are required. This device is
the only type of recording apparatus and reproduction set used in
the Danish motion picture industry.
The Nordisk Tone -Film company is in close contact with British
Acoustic, Ltd., and the strong Gaumont company of France, and in
this way keeps in touch with the trend of the trade and the types
of pictures demanded by the public.
NORWAY
At present there are no studios equipped for sound film production
in Norway. Neither is there any local manufacture of reproduction
sets or recording apparatus. There are approximately 10 theaters
in Norway having a seating capacity over 750 and 20 others ranging
in seating capacity between 500 and 750, which should lend them-
selves to wiring for sound pictures.
In Oslo the theaters are owned and operated by the Commune.
One independent theater outside the city with a large modern
building seating 2000 has been in negotiation with an American
company for the installation of sound film equipment. The Com-
mune has also been in touch with the same company for the wiring
of its theaters. In addition, one other downtown Oslo theater is
expected to be wired in the near future. If sound films prove popular,
three or four other installations may follow soon after. The larger
houses in Bergen, Trondhjam, and Stavanger will also undoubtedly
be interested in the new development.
Jan., 1930] SOUND PICTURES IN EUROPE 25
It may therefore be said that the immediate prospects for sound
film development in Norway are very good, and once the equipment
is installed, sound films should be as popular in Norway as anywhere
else.
SWITZERLAND
At the present time, three theaters in Switzerland have been wired
for sound pictures, all three installations being American reproducing
units. It is felt that at the end of this year the larger Swiss cities,
with the exception of Berne, will have at least one theater each
equipped to handle talkies. Out of total of 300 motion picture thea-
ters in Switzerland, 25 have a seating capacity over 750. These
theaters are potential purchasers of sound equipment.
This country has no moving picture industry, except for very
small concerns, each turning out a few reels per year. Thus, prac-
tically all films must be imported. At present, all silent films are
provided with subtitles in two languages, either French and German,
or French and Italian. Possibly the greatest handicap for sound
pictures is the very heavy expense involved in the original installa-
tion. The Swiss cinema field is at present reported to be greatly
overcrowded, and theaters are constantly reported to be in difficulties.
The American system of sound projection is almost universally
favored. It is regarded as very much better than the German
systems, but is also about ten times as expensive. Once the problem
of installing such expensive apparatus is solved, it is probable that
the language difficulties will be overcome in much the same way as
is the case now in Paris theaters, in which the music only is regis-
tered, while on the screen the subtitles remain in two languages.
The extensive use of sound films is a thing of the future, however,
and will not be realized in Switzerland for some years to come.
CONCLUSION
I hope I have made clear to you, from the foregoing, that the
introduction of dialog and sound synchronized films will, within the
next few years, create an entirely different situation in the field of
motion pictures in Europe. Beyond a doubt, this new invention has
been received abroad as enthusiastically as Americans have wel-
comed it. Time alone will solve the problem of language difficulties
at present encountered in foreign markets where English is not the
predominating language. However, production of American dialog
26 NATHAN D. GOLDEN
pictures in more than one language should not meet with serious
handicaps.
Inasmuch as it will undoubtedly be at least two years before the
total sound installations abroad will equal or even approach the
number in the United States, it is safe to assume that exports of
American motion pictures should continue to maintain the same
high level as in the past. Those theaters abroad not equipped to
present sound pictures will continue to show silent versions of pic-
tures. Recently published production schedules of American pro-
ducers indicate that there will be a sufficient number of silent ver-
sions of sound pictures to meet the requirements of those theaters
in this country as well as abroad.
The American silent film and the sound film without dialog should
continue to dominate the foreign field from a qualitative standpoint.
Whether films of this type of manufacture can actually maintain
America's prestige abroad, rests entirely on the upkeep of quality
and the production of a sufficient number to meet European demand.
On this score there should be slight uneasiness.
I desire to express my thanks to C. J. North, Chief of the Motion
Picture Division, for his cooperation and capable assistance in the
preparation of this paper. My thanks are also extended to George
R. Canty, Motion Picture Trade Commissioner to Europe, and
other European representatives of the Bureau of Foreign and Domes-
tic Commerce for their valuable reports, which have made this paper
possible.
THE EARLY HISTORY OF WIDE FILMS
CARL LOUIS GREGORY*
It has been claimed that there is only one standard of measure-
ment which is common to all nations of the earth. That measurement
is the width of a piece of standard theatrical size motion picture film.
Many persons actively engaged in the industry seem to be unaware
that other widths and dimensions of film were ever used and some
even believe that the use of wide film is a recent invention.
History moves in cycles and recent events in the use of wide film
of various gauges show that we are in the midst of a repetition of the
unstandardized efforts and struggles that marked the work of so
many of the early pioneers of the industry.
To those who have never had occasion to refer to the early history
of the motion picture it may come as a surprise that scores of scien-
tists, mechanics, and inventors in nearly every civilized country were
working simultaneously during the 90 's to perfect a system for taking
and showing motion pictures. While they were all, in the main,
working along the same lines, yet each adopted whatever width of
film seemed to him to be best suited for his experiments.
That the 35 mm. width of film came to be the measurement which
survived and eventually became standardized is, so far as the writer
has been able to ascertain, a coincidence. It was not foresight that
caused Mr. Edison in this country and Lumiere Freres in France to
select film widths that were so nearly the same that they were prac-
tically interchangeable. It was pure chance, also, that these two
firms happened to be the most powerful commercially in their re-
spective countries.
Edison selected ! 3 / 8 inches as the width of film best suited for his
Kinetoscope only after a long series of experiments with films in
cylinders, disks, and narrow ribbon form run horizontally instead
of vertically.
This measurement coincides within l / m of an inch with the 35 mm.
width selected by Lumiere and, while Lumiere used only one round
* 76 Echo Ave., New Rochelle, N. Y.
27
28 CARL Louis GREGORY [J. S. M. P. E.
perforation on each side of the film and Edison used four rectangular
ones, it was possible, by altering sprockets or by reperforating the
Lumiere film, to use them interchangeably. Lumiere later reluc-
tantly abandoned the two-hole perforation and copied the Edison
standard in order to sell film to users of Edison machines.
In the early days France led the rest of the world in production,
and many a pioneer film man in this country profited by pirating and
duping French films for distribution in the Nickelodeons here.
It is a difficult and almost impossible task to locate chronologically
all the different sizes of films. Often the details of perforations and
frame size are entirely omitted in the records which have been pre-
served.
An advertisement in Hopwood's Living Pictures, edition of 1899,
offers the "Prestwich" specialties for animated photography "nine
different models of cameras and projectors in three sizes for y 2 in.,
l 3 /s in., and 2 3 /s in. width of film." Half a dozen other advertisers
in the same book offer "cinematographs" for sale and, while the illus-
trations show machines for films obviously of narrow or wide gauge,
no mention is made of the size of the film.
During 1899 there were in England and on the Continent Muto-
graph films 2 3 / 4 inches wide, Demeny Chronophotographs 60 mm.
wide, Skladowsky film 65 mm. wide, Prestwich wide film 2 3 /s inches
wide, Birtac film n /i6 inch wide, Junior Prestwich y 2 inch wide,
besides the present standard established by Paul, Edison, and
Lumiere.
Henry V. Hopwood in 1899 described more than fifty different
models of projectors made by different manufacturers and gave the
names of about seventy more. Curiously enough the size of film
used in the various machines is mentioned only in two or three in-
stances. It is probable that most of them used the Edison standard,
although it is obvious from the descriptions that many of them used
other sizes.
Probably the first example of motion picture "film" as it is photo-
graphed today was a scene taken in the Champs filyse*es in Paris
in 1886 by Dr. E. J. Marey. Although the "film" was paper, sensi-
tized celluloid not being available until a year or two later, and
cine projectors having not yet been invented, this paper negative could
be printed as a positive film and run as a Fox Grandeur film today.
In May, 1889, William Friese-Greene, 92 Piccadilly, London, made
a motion picture negative of a scene on the Esplanade, Brighton,
Jan., 1930] EARLY HISTORY Otf WlDE FlI,MS 29
England, using paper film negative with frames 2 x /2 inches wide and
iy 2 inches high. Later in the same year he used celluloid film dis-
placing the paper used earlier.
One of the first to project successfully upon a large sized screen
was Mr. Woodville Latham, inventor of the Latham Coop which
caused much patent litigation in the early days. Latham called his
machine the Eidoloscope and used film 2 inches wide with frames
3 /4 inch high by l x /2 inches long.
In the fall of 1897, Enoch J. Rector, an inventor and promoter,
showed pictures of the Corbett-Fitzsimmons prize fight in the
Academy of Music on 14th Street in New York City. His apparatus
was called the Veriscope and the same mechanism used to show the
pictures was employed in the camera with which 11,000 feet of film
were taken at Carson City, Nevada, March 17, 1897. Thereafter
about twenty machines for projecting this large size film were manu-
factured and these fight films were exhibited all over the country.
In the late 90 's the motion picture was regarded as a great novelty
which would soon die out. Conditions were chaotic and everyone
who went into the business worked with frantic eagerness to reap
the rich harvest before the fickle interest of the public should pass
on to some new fancy. Just as there was no standard of film size,
no rate of frames per second was established and the taking rate
varied from 8 per second to 60 per second among the different sys-
tems, each of which was distinguished by some fantastic and poly-
syllabic name. Out of the hundreds of such coined trade names
only a few, such as Kinetoscope, Vitagraph, Biograph, and Muto-
scope, are remembered today.
Subjects were confined almost entirely to news events, prize-
fights, short scenic shots, and theatrical or spectacular bits many
of which were considered very risque in those conservative days.
The May Irwin Kiss, Little Egypt, Loie Fuller's Fire Dance, Bridget
Serves Salad Undressed, and many others brought gasps of amaze-
ment at their audacity.
On November 3, 1899, the Jeffries-Sharkey fight was held at
Coney Island at night. Wm. A. Brady, now well known in the
theatrical and motion picture world, and a promoter named O'Rourke
sponsored the bout and induced the American Mutoscope and Bio-
graph Company to film the fight. Wm. Bitzer, a cinematographer
still on the staff of D. W. Griffith, had charge of the photography.
Four hundred arc lights were hung over the ring. The film used
30 CARL Louis GREGORY [j. s. M. B. P.
was 2 3 / 4 inches wide and each frame was 2*/4 inches high. Three
hundred and twenty feet of this wide film were used per minute, the
perforations being made in the camera at the instant of taking.
The fight lasted for twenty-five rounds of three minutes each, and
more than seven miles of film were exposed. Four cameras were
on the job so as to obtain a continuous record. Buckling of the
film in the cameras was frequent although the film could be watched
through a red glass peep-hole by the light of a small ruby lamp
inside the camera box. The perforations in the large Biogra,ph
film were used in printing, but not in projecting. The projector
pulled the film down by means of a set of mutilated rubber rollers
and the projectionist had to watch the frame continuously to prevent
creeping of the frame line on the screen.
Oscar B. Depue, a member of this Society and partner of Burton
Holmes, in 1897 purchased a machine in Paris from Leon Gaumont
for taking 60 mm. wide film, then put up in one hundred foot lengths.
It was a darkroom model, not a daylight proposition. Unwinding
and rewinding were done inside the camera on aluminum spools.
This machine he took to Italy and the first motion picture turned
out on the machine was of St. Peter's Cathedral with the fountain
playing in the foreground and a flock of goats passing by the machine.
He then took other pictures of Rome and from there visited Venice,
making pictures of the canal and Doges Palace and the waterfront
along the canal with views of feeding the pigeons at St. Marks with
the great cathedral in the background. From there he went to
Milan for a scene of the Plaza in front of the Milan Cathedral;
thence to Paris where pictures of the Place de la Concord with its
interesting traffic and horse drawn busses, fountains, obelisks,
statues, bicycles, wagons, trucks, and carriages were made. These
negatives are still in his possession although the prints from them
have long since been lost on account of our having changed from that
size of picture to the standard size. This Gaumont wide film camera
was used for five years by Mr. Depue and most of the negatives,
many of which are of great historical value, are still in good con-
dition, so that either full size or standard sized reduction prints can
still be made from them.
During the first few years of the new century all of the sizes of
wide film died out or changed to the Edison standard and, until
the present vogue for sound pictures caused a revolution in the cine-
matographic world, the Edison standard with very slight modifica-
Jan., 1930] EARLY HISTORY OF WIDE FILMS 31
tions seemed to be so well established that nothing could shake its
supremacy. During these quiet years a few inventors cried aloud
in the wilderness that they had worked out larger and better methods
for making cinematograph films, but their pleas fell, for the most
part, upon deaf ears. Spoor and Bergren have worked for more
than ten years upon a 63 mm. film called Natural Vision pictures.
Widescope sponsored a double frame picture on standard film. After
that an Italian patent was acquired in which a film about 2*/4 inches
wide is held in cylindrical form about the axis of rotation of a revolving
lens so that each frame is photographed using the same principle as
a panoramic still camera. Unfortunately this method of taking
pictures introduces the same curvilinear distortion often noticed
in panoramic still photographs.
Pox Grandeur pictures are 70 mm. in width with a frame 48 mm.
by 22.5 mm., leaving space available for a sound track about 10 mm.
wide. Lorenzo Del Riccio, a member of this Society, is perfecting
the Magnafilm for Paramount. This film is 56 mm. wide and the
frames are 19V2 mm. high. Several other sizes of wide film are
being used experimentally and other new sizes are being advocated
but these are current and not early history and do not properly
belong in this chronicle.
We have been looking back over; the years since 1886 when Dr.
E. J. Marey, of Paris, made the first paper band of negative on the
same principle as motion pictures are made today. We shall look
forward over the years to come with a strong conviction that the
vSociety of Motion Picture Engineers will bring the sponsors of these
new film sizes together to work out standards which will prevent a
repetition of the chaotic conditions which hampered the industry
in its early days.
DISCUSSION
MR. TAYLOR: It strikes me as strange that some one with an historical mind
has not accumulated a library of old film. Such a hobby would not cost very
much or take up much space. Here are fifty types of machines with no record
of the film. The Society might well give this some consideration and appoint a
committee to look into the matter.
MR. GREGORY: I agree with the speaker. I know of a tremendous collection
of that kind of material in the possession of Mr. Jean A. LeRoy. I should like
to have this matter presented to the Society at the proper time.
RECTANGLE PROPORTIONS IN PICTORIAL
COMPOSITION*
LOYD A. JONES
Since the birth of the motion picture some thirty years ago there
have been discussions from time to time concerning the most satis-
factory shape of the picture area. In the early stages of develop-
ment several different shapes and sizes were proposed and tried
experimentally. Using the ratio of .width to height as a specifica-
tion of the shape of the rectangle, we find among the very early pro-
ductions values of this ratio varying all the way from 1.25 up to 2.0.
Practice finally crystallized, however, and a rectangle having a width
of four units and a height of three units (R = 1.33) was adopted as
standard. This continued as almost universal practice until the
advent of sound which, in the case of sound-on-film positives,
necessitated the narrowing of the available picture area in order to
provide space for the photographic sound record. If the height of
the positive image is maintained at its old value, that is, four per-
forations less the necessary allowance for frame line, the resultant
positive picture area has a ratio of approximately 1.15.
Even under the old conditions where the 4 to 3 ratio (R = 1.33)
obtained, many individuals, including motion picture directors, art
directors, scenario writers, camera men, etc., felt that the resultant
picture was too "fat," that is, too narrow relative to its height, for
most pleasing and satisfactory results. The subtraction of the area
required for the sound track has served to make available picture
area on the positive film even more nearly square. It is almost uni-
versally agreed among those who have given this problem careful
consideration that this change in shape of the projected picture is
in the wrong direction and gives an area of which the proportions
are extremely unsatisfactory from the standpoint of both pictorial
composition and practical utility. This situation has served, there-
fore to focus attention again on the question of picture shape, and
* Communication No. 410 from the Kodak Research Laboratories.
32
RECTANGLE PROPORTIONS IN COMPOSITION 33
during the past months the merits and demerits of various proposed
shapes have been vigorously discussed.
Motion picture technic cannot be classified as belonging entirely
to either the realm of art or that of science but is made up of many
factors that fall within the category of applied science and many
that are of an artistic nature. In a discussion of picture shape
there are many mechanical arid optical requirements that should be
considered but no attempt will be made to deal with these at this
time. It is desired rather to call attention to one or two aspects
of the problem which may be classified as artistic, or, since they are
dealt with by a method of mathematical analysis, the term pseudo-
artistic might be more appropriate.
DYNAMIC AND STATIC SYMMETRY
A search through the literature of art shows that the question of
rectangle proportions is one which has occupied the attention of
many artists and that most exhaustive studies have been made in
an effort to determine the rectangle shapes which may be considered
satisfactory from the standpoint of pictorial composition and design.
The literature on the subject is voluminous and it will be possible
in this paper to give only a very brief summary of the conclusions
reached by a number of eminent authorities in this field.
From the standpoint of pictorial composition and design, rectangles
may be classified as of two general types, namely, (a) those exhibiting
static symmetry, and (b) those exhibiting dynamic symmetry.
Rectangles of the former class may be analyzed into series of squares.
For instance, a rectangle having a height of 2 units and a width of
3 units may be analyzed into 6 equal square areas, while one having
a height of 3 units and a width of 4 units may be analyzed into 12
equal squares. Such areas are considered by the artist to be more
formal and of less merit from the aesthetic point of view than rec-
tangles of dynamic symmetry type.
The proportion of the motion picture on standard 35 mm. film
previous to the introduction of sound on film was 4 wide by 3 high.
This is a rectangle belonging definitely to the static symmetry
classification. Even previous to the introduction of sound and
when the usual projected picture had the ratio of 1.33, many observers
of artistic training had criticized the shape as not being particularly
pleasing or well adapted to the requirements of best pictorial com-
position.
34
LOYD A. JONES
[J. S. M. P. E.
Rectangles of the dynamic symmetry type are based almost
entirely on two general proportion principles. 1 One of the series
of these rectangles is referred to as the square root series, while the
other group is termed the whirling square series. In the former
group are found rectangles for which the ratio values are equivalent
to the square roots of whole numbers, as, for instance,
R = \/2 = 1.414 R = \/4 = 2.000
j R = : V 7 3 == 1.732 R = V5 = 2.236
From these basic rectangles many other more complicated rectangles
can be derived all of which have the characteristics of dynamic
symmetry. Those based directly on the whole number roots repre-
sent the simplest forms and, perhaps as a consequence of this sim-
plicity, are considered to possess greater strength than the more
\ /'
>Tv
V
P E
i
i
x
i
\
i
\
.
/
\
!/
(a)
FIG. 1. (a) Method of constructing the root rectangles. (&) Method of
constructing the whirling square rectangle.
complicated derived proportions. It will be noted that the third
member of the series above can be analyzed directly into a series
of squares, and therefore belongs also to the static symmetry classi-
fication. This rectangle is considered by authorities on this subject
to be the weakest and least desirable of the various root rectangles.
Of this series it appears that the first two represent the strongest
and most desirable members from the standpoint of pictorial com-
position, while the fourth member has many virtues when considered
from the standpoint of conventional design and decoration. Addi-
tional members may be added to this series by using the square
roots of higher numbers, for instance, \/6, \/7> etc>, but these are
of minor importance and less suitable to the requirements of average
pictorial composition than those already mentioned.
In Fig. 1 at (a) is shown a method of constructing the root rec-
1 "The Diagonal," I, 1919-20. Yale University Press.
Jan., 1930] RECTANGLE PROPORTIONS IN COMPOSITION
35
tangles. The line OB' is the diagonal of the square OAB'H. As
indicated by the dotted construction the line OB is equal in length
to the diagonal OB' and the rectangle constructed on the base OB
is the root two rectangle. Likewise, the rectangle constructed on
the base OC is the root three rectangle, that on the base line OD is
the root four rectangle, and that on base line OB is the root five rec-
tangle.
Dynamic symmetry Static symmetry
FIG. 2. A series of rectangles exhibiting dynamic symmetry and static
symmetry.
36 LOYD A. JONES [J. S. M. P. B.
The whirling square rectangle is illustrated at (b) in Fig. 1. The
construction of this rectangle is shown by the dotted lines. BDA'C
is a square, the point O being located at the middle of the base line
BC. The diagonal OA' rotated about O establishes the point A.
The line BA then becomes the base of this rectangle, one side of the
basic square BD being the altitude. The rectangle ABDF has the
ratio 1.618 and is the famous whirling square rectangle so intimately
connected with classical Greek art. Many of the finest compositions
in Greek architecture, sculpture, painting, mural design, and pottery
can be broken down into this rectangle which, in the opinion of many
artists, exhibits the characteristics of dynamic symmetry to the
most marked extent.
In Fig. 2 are shown series of rectangles representing both the
dynamic and the static symmetry types. The top of the left-hand
column is the root two rectangle. Immediately below this is the
root three rectangle, and at the bottom of this column the root five
rectangle. In the right-hand column are shown a few examples
of rectangles exhibiting static symmetry; that at the top having a
ratio of 4 to 3 (1.33), the proportions of the present standard motion
picture positive. Below this is the 3 to 2 rectangle (1.5), the next
in the series being the 7 to 4 rectangle (1.75). At the bottom of this
column is the 2 to 1 rectangle which is also the root four rectangle
sometimes placed in the dynamic series. There seems to be little
doubt, however, that this rectangle exhibits static characteristics
much more strongly than dynamic. It is only when used in a treat-
ment combined with the whirling square rectangle or one of the other
root rectangles that it can be said to exhibit satisfactorily dynamic
symmetry characteristics. It seems better, therefore, in a simple
classification such as that in which we are interested, to place it
specifically in the static class.
RECTANGLE PROPORTIONS IN ART
In a consideration of the rectangle proportions adapted to the
requirements of pictorial composition, it seems reasonable to assume
that some valuable information may be obtained by a study of what
has been done by the master artists during the past three or four
centuries. While it may be true that we are not justified in drawing
definite conclusions as to the most satisfactory rectangle shape for
motion picture purposes from data based upon artistic compositions
which necessarily are of static character, it seems probable that a
Jan., 1930] RECTANGLE PROPORTIONS IN COMPOSITION
37
knowledge of what has been done in this field may prove interesting
and may give some indication of what is most desirable in motion
picture practice. A rather superficial study has been made of the
rectangle proportions used by artists in the creation of their pictures.
It has been found, as was to be expected, that a very great variety
of picture shapes has been used by the masters in this field. Hence,
to make the results of such analyses conclusive and convincing, an
enormous number of examples should be studied and the final con-
clusion based upon the statistical averages. Unfortunately, time
has not been available to carry this analysis to the point where the
20-
Z.O
RATIO WTO H
FIG. 3.
Ratio -frequency curve of some two hundred and fifty paintings by
about fifty well known artists.
results may be considered representative of the whole field. It
may be of interest, however, to present a few of the preliminary
values obtained in this manner.
As an initial step the width to height ratio of some two hundred
and fifty paintings by about fifty well known artists was determined.
The artists represented include not only old masters but some of the
more modern painters. Since it seems fairly certain that the rec-
tangle shape most satisfactory for motion picture technic must be
wider than it is high, it was decided to exclude from this group all
pictures with the ratio of width to height less than unity. The very
38 LOYD A. JONES [J. S. M. P. E.
nature of the subject matter which it is desirable to include in the
average motion picture composition seems to necessitate horizontal
dimensions greater than the vertical. It is obvious, of course, that
no one rectangle proportion can be best adapted to every composition
that may possibly be desired and that, in choosing a rectangle pro-
portion, compromises must be made with specific requirements
and some value chosen fitting as closely as possible the average re-
quirements.
It should be remembered also that in making any classification
of rectangle proportions used in pictorial composition some considera-
tion must be given to the subject type and picture content before
any final conclusion can be drawn. In this preliminary study,
however, this factor has been neglected and the ratio-frequency
curve obtained applies to a group of paintings embracing practically
the entire gamut of pictorial composition, with the exception of all
vertical types. The results of this analysis may be shown graphically
by plotting the number of compositions as a function of the width
to height ratio. The curve obtained in this manner is shown in
Fig. 3. It will be noted that a maximum exists at R = 1.3, another
maximum at R = 1.4, with a suggestion of a third maximum at R =
1.5. Relatively few examples were found for which the ratio value
is less than 1.2. Likewise, relatively few compositions in this par-
ticular group have a ratio value greater than 1.6.
The same line of thought has been carried further and a rather
complete study of the work of one of the old masters has been ana-
lyzed from the standpoint of rectangle proportions. In any sta-
tistical study it is desirable to base conclusions on a large number
of observations and in a given group to include all available examples
without the arbitrary exclusion of any which may apparently be
unusual. From a monograph on the work of Rubens 1 containing
authentic reproductions of the entire work of this master, the rec-
tangle proportion for each of his compositions was determined. An
attempt was made to classify these pictures from a standpoint of
motion picture technic. As a matter of fact, the work of this artist
seems particularly adapted to this purpose. The majority of his
compositions represent situations which might very conceivably
fit into a motion picture practice, representing as they do movement,
action, dramatic situations, emotional expression, etc. The usual
1 Adolf Rosenberg, "The Work of Rubens," Brentanos, 1913.
Jan., 1930] RECTANGLE PROPORTIONS IN COMPOSITION 39
classification of pictures into portrait, landscape, genre, still life,
etc., does not seem to fit the requirements of this analysis. The
author has therefore attempted to make a classification which is
interpretable more directly into terms of motion picture technic,
and while it is admittedly far from complete, it does seem to permit
the classification of paintings into groups having some significance
from the standpoint of our current motion picture practice. The
classification is based largely on the number of human figures in-
cluded, further modified by a consideration of whether the picture
is a close-up, semi-close-up, medium, or long shot representation.
For instance, among the pictures including a single human figure,
representing of course the portrait class, may be found those in which
only the face or head is shown, while others include the bust, half
length, three-quarter length, or full length representation. Most of
these may be classed as close-up compositions although in the case
of the three-quarter or full length representations they become
analogous to semi-close-up or even medium distance shots. In the
case of compositions including two figures it seems satisfactory to
make but two subdivisions, those which may be considered semi-
close-up, the figure being shown as somewhat less than full length,
and a medium distance shot where the two figures are shown in full
length. The same is true of those compositions including from
three to five figures, while in the case of larger groups the sub-
division may be made most advantageously in terms of medium
distance shots, semi-long shot, and long shot groupings. Among
the works of Rubens we find but few landscapes, and in practically
all these, figures occupy a position of subordinate importance.
These can quite conceivably be compared with certain types of
motion picture technic, exterior shots either of semi- or long shot
characteristics including figures representing either static or dynamic
action. On the whole, the works of Rubens seem to be particularly
adapted to an analogous motion picture technic classification. The
groups into which his works have been classified are as follows:
Single-figure compositions
(a) Head only, close-up type
(&) Head and shoulders, close-up type
(c) Half length figure, close-up type
(d) Three-quarter length figure, semi-close-up type
(e) Full length figure, semi-close-up type
II. Two-figure compositions
40 LOYD A. JONES [j. s. M. P. E.
(a) Less than full length, semi-close-up type
(6) Full length figures, medium distance type
III. Three- to five-figure compositions
(a) Less than full length, semi-close-up type
(b) Full length figures, medium distance type
IV. Six- to ten-figure compositions
(a) Full lengths, medium distance type
V. Ten- to twenty-five-figure compositions
(a) Medium distance type
(6) Semi-long shot type
VI. More than twenty-five-figure compositions
(a) Medium distance type
(6) Long shot type
VII. Landscape, exterior long shots with architectural element or figure
group, and compositions of miscellaneous character in which human figures are
entirely absent or occupy subordinate or inconspicuous positions, generally of the
semi-long shot or long shot type.
In Table I are shown the values of ratio for the compositions
which fall in the subdivisions of the single-figure compositions. At
the bottom of each column is given the mean value and below that
the number of compositions in the group. The number of observa-
tions in each of these groups is insufficient to warrant the plotting
of a frequency curve. While theoretically the use of the arithmetical
mean in work of this kind is not a particularly satisfactory way of
arriving at a definite conclusion as to the predominant characteristic
of the group, it seems to be the only method available where the
number of observations is so limited. In case there is more than
one maximum in the frequency distribution this effect will be masked
by taking the arithmetical mean. For instance, it is evident from
an inspection of Fig. 3 that had a straight arithmetical average been
made the true distribution of frequency as a function of ratio would
have been obscured. The use of the arithmetical mean, however,
in the case of rather homogeneous groups, such as are obtained by
the classification of compositions into distinct types, seems to be a
fairly satisfactory method of obtaining some idea as to the pre-
dominant shape factor. It will be noted that the ratio decreases
from the I (a) toward the I (c) grouping. This of course is a logical
consequence when composition factors are considered.
In Table II are given the ratio values obtained for the two-figure
compositions and the three- to five-figure compositions. The values
obtained for the II (a) group are fairly homogeneous and a single
arithmetical mean seems to be a satisfactory indication of character-
Jan., 1930]
1
RECTANGLE PROPORTIONS IN COMPOSITION
41
Ratio of Width to Height for Single-Figure Compositions
Classification
I (a)
I (6)
I (c)
I (<0
I ()
0.72
0.64
0.66
0.58
0.35
0.77
0.71
0.74
0.68
0.35
0.80
0.73
0.74
0.69
0.36
0.81
0.73
0.74
0.70
0.36
0.85
0.74
0.75
0.71
0.38
0.91
0.74
0.75
0.72
0.38
1.04
0.75
0.75
0.72
0.45
1.15
0.75
0.76
0.73
0.45
0.76
0.78
0.74
0.47
0.77
0.78
0.74
0.47
0.77
0.78
0.74
0.48
0.77
0.79
0.75
0.48
0.77
0.79
0.76
0.52
0.78
0.79
0.76
0.55
0.79
0.79
0.76
0.55
0.79
0.79
0.76
0.59
0.79
0.79
0.77
0.59
0.79
0.79
0.77
0.62
0.79
0.79
0.78
0.62
0.80
0.79
0.78
0.63
0.80
0.80
0.78
0.65
0.80-
0.81
0.78
0.66
0.81
0.81
0.79
0.67
0.82
0.82
0.79
0.67
0.82
1.17
0.79
0.70
0.82
0.79
0.70
- '"
0.84
0.79
0.71
0.84
0.79
0.74
0.85
0.80
0.76
0.85
0.80
0.82
0.86
0.80
0.85
0.86
0.81
0.86
0.83
1.02
0.84
1.17
0.84
0.85
0.85
0.88
Mean ratio
0.88
0.81
0.79
0.77
0.57
Number of
pictures
8
35
25
38
31
TABUS II
Ratio of Width to Height for Two -Figure Compositions and the Three- to Five- Figure
Compositions
Classification
II (a)
II
R< 1
(
R > 1
in
R < 1
(a)
R > 1
in (
R < 1
h)
R > l
0.59
0.58
.26
0.66
1.02
0.69
1.01
0.65
0.59
.26
0.70
1.07
0.74
1.02
0.75
0.63
.26
0.70
1.09
0.74
1.04
0.75
0.68
.31
0.70
1.09
0.74
1.05
0.77
0.72
.33
0.71
1.28
0.76
1.05
0.78
0.72
.33
0.72
1.30
0.76
1.05
0.79
0.74
.33
0.72
1.31
0.78
1.05
0.84
0.74
1.37
0.73
1.31
0.78
1.07
0.92
0.74
1.38
0.73
1.45
0.79
1.07
0.76
1.43
0.73
1.89
0.79
1.12
0.77
1.45
0.74
0.79
1.13
0.78
1.45
0.74
0.79
1.13
0.78
0.75
0.79
1.16
0.78
0.76
(10)
0.83
1.19
0.79
0.76
0.83
1.21
0.79
0.77
0.84
1.22
0.82
0.79
0.85
1.22
0.90
0.79
0.85
1.25
0.98
0.79
0.87
1.28
0.79
0.93
1.31
0.79
0.94
1.31
0.80
0.96
1.33
0.81
0.96
1.33
0.82
1.33
0.83
1.35
0.83
1.35
0.84
1.37
0.84
1.37
0.85
1.37
0.85
1.38
0.86
1.38
0.86
1.39
0.88
1.41
0.88
1.41
0.97
1.41
1.43
1.45
1.45
1.45
1.47
1.51
1.54
1.56
1.59
1.64
1.64
1.66
1.72
1.95
1.95
1.97
Mean ratio
0.76
0.75
1.35
0.78
1.28
0.81
1.48
Number of
pictures
9
19
12
34
10
23
50
TABUS III
Ratio of Width to Height for the Six- to Ten- Figure Compositions and the Ten- to
Twenty- Five- Figure Compositions
Classification
IV
R < 1
(a)
R > 1
V (a)
V
R < 1
(b)
R > 1
0.65
1.04
.28
0.69
1.11
0.65
1.04
.30
0.70
1.20
0.68
1.06
.33
0.74
1.22
0.70
.07
.38
0.74
1.25
0.72
.10
.45
0.76
1.25
0.75
.11
.47
0.76
1.25
0.75
.11
.60
1.25
0.76v
.15
.64
1.28
0.77
.16
1.66
1.28
0.78
.16
1.38
0.79
1.20
1.39
0.80
1.20
1.44
0.82
1.20
1.45
0.83
1.22
1.45
0.85
1.23
.47
0.91
1.28
.47
0.99
1.30
.47
0.99
1.30
.56
1.31
.61
1.31
1.79
1.31
2.32
1.31
2.77
1.33
1.35
1.35
1.37
1.37
1.37
1.38
1.39
1.42
1.43
1.43
1.47
1.47
1.48
1.49
1.49
1.54
1.54
1.54
1.54
1.54
1.56
1.56
1.58
1.59
1.66
1.75
1.92
Mean ratio
0.79
1.36
1.46
0.73
1.49
Number of
pictures
18
49
9
6
22
44 LOYD A. JONES [j. s. M. P. E.
istic mode. An inspection of values applying to those compositions
which are put into the II (6) class shows two distinct groups, for
one of which R is less than unity and for the other greater. These
values have therefore been split into two groups on the basis of an
evident marked difference in character. After this secondary classi-
fication within the group has been made, two groups of values, each
relatively homogeneous in character, are obtained, one of which
represents vertical compositions (R less than unity) and the other
horizontal compositions.
A similar state of affairs was found in the case of the III (a) class,
the ratio values being rather definitely divided into groups greater
than and less than unity.
In class III (b) it was again found necessary to separate the vertical
from the horizontal types of compositions in order to obtain homo-
geneous groups of ratio values. It is interesting to note that in the
case of two-figure compositions (classes II (a) and II (&)) the number
of vertical type compositions is very much in excess of the horizontal
type. This is also true in the case of three- to five-figure com-
positions falling within the III (a) class and including those com-
positions where the figures are shown as somewhat less than full
length and in a semi-close-up rendition. In the III (b) class, also
including three- to five-figure compositions, but where the distance
is increased to correspond to a medium distance type, this condition
is reversed and compositions for which the ratio value is greater than
unity exceed the number of those of the vertical type for which R
is less than unity.
In Table III are given the data relative to the six- to ten-figure
compositions and the ten- to twenty-five-figure compositions. In the
case of class IV it seemed to be impossible to further subdivide the
compositions on the basis of the distance from point of view. Prac-
tically all these may be classified as medium distance types. Here
again, a small, fairly homogeneous group of vertical compositions is
obtained and a much more numerous group, also relatively homo-
geneous in ratio value, of the horizontal composition type.
In class V (a) all the compositions are of the horizontal type
although this group is limited in number. In group V (b) it was
necessary to subdivide again in order to obtain homogeneous group-
ings. Those of the vertical type are few in number, while those of
the horizontal type are relatively numerous and the mean value of
ratio relatively great. Among the compositions including many
Jan., 1930] RECTANGLE PROPORTIONS IN COMPOSITION
45
figures (this term "many" is defined as applying to all figure group-
ings containing more than twenty-five members) none of the vertical
type are found and the ratio values in the case of both subdivisions
of this group are relatively high. Those compositions falling within
the last subdivision, VII, are also fairly homogeneous with respect
to their ratio values. No vertical compositions appear and the mean
value for R is relatively high.
The results of this statistical analysis are summarized in Table V.
As shown by the total at the bottom of the second column 460 com-
positions are included. Columns 3 to 7 give information as to
the character of the groups used in this classification. In the columns
"Min." and "Max." are the minimum and maximum values of R
TABLE IV
Ratio of Width to Height for Composition Including Many Figures, and for
Landscapes
Classification
VI (a)
VI (&)
VII
1.35
1.33
1.30
1.50
1.33
1.35
1.51
.35
1.37
1.51
.41
.41
1.53
.53
.43
1.61
.56
.45
1.61
.57
.45
1.61
.66
.49
1.66
.66
.51
1.72
.72
.51
1.81
.81
.54
1.88
.81
.54
.88
.56
.88
.56
.96
.56
.57
.61
.64
.66
.69
.72
.75
.78
.88
.96
Mean ratio
1.61
1.63
1.57
Number of pictures
12
18
25
46
LOYD A. JONES
[j. S. M. P.
for each of the classes. In the case of the first six classes these are
of some significance since the compositions included within these
classes are relatively similar in shape. For those classes which
contain both vertical and horizontal compositions these maximum
and minimum values are of little significance since they represent
the extremes of a distribution containing two definite maxima.
For these groups no value of the mean ratio is shown. In the last
two columns, however, are given the mean value for the vertical
compositions and the mean value for the horizontal compositions.
It is interesting to note the progressive manner in which the rect-
angle shape changes as the number of figures included in the com-
TABLE V
Summary of Statistical Analysis of IfiO Compositions
Class
No.
Min. R
Max. R
Mean R
R < l
R > 1
I (a)
8
0.72
1.15
0.88
0.88
(P)
35
0.64
1.17
0.81
0.81
w
25
0.66
1.17
0.79
0.79
CD
38
0.58
0.88
0.77
0.77
()
31
0.35
0.85
0.57
0.57
II (a)
9
0.59
0.92
0.76
0.76
(*)
31
0.58
1.45
0.75
1.35
III (a)
44
0.66
1.89
0.78
1.28
(V)
73
0.69
1.64
0.81
1.48
IV (a)
67
0.65
1.92
0.79
1.36
V(a)
9
1.28
1.66
1.46
1.46
(b)
35
0.69
2.77
0.73
1.49
VI (a)
12
1.35
1.88
1.61
1.61
0)
15
1.33
1.96
1.63
1.63
VII (a)
26
1.30
1.88
1.57
1.57
Total
460
position increases. For instance, for single-figure compositions the
ratio value remains below unity and with the exception of the full
length compositions is fairly constant at a value of approximately
0.80. As we progress into the two-figure compositions there is an
immediate subdivision into horizontal and vertical types. This
persists throughout the three to five, six to ten, and ten to twenty-
five classes, the relative number of vertical compositions steadily
decreasing as the number of figures in the composition increases.
Where more than twenty-five figures are included, the vertical type
disappears entirely and the same is true for class VII including
landscape compositions, either with or without figure groupings.
Jan., 1930] RECTANGLE PROPORTIONS IN COMPOSITION 47
In considering the requirements of our modern motion picture
technic, it seems probable that, because of the presence of movement
and action of a given number of figures within the composition, a
somewhat greater dimension in the horizontal direction than that
used in static composition is desirable. It is quite evident that in
the consideration of the most desirable shape for the motion picture
screen many factors other than those of pictorial composition as
applying to still pictures must be considered. The author feels,
therefore, that a study of this subject is of some interest and sig-
nificance.
DISCUSSION
MR. COFFMAN: I think this paper is a most unusual example of the ways in
which the scientific mind and the artistic complement each other. I believe that
the basis of both art and science are similar in a great many respects. It is certain
that they come together in insisting on general symmetry, at any rate, and this
paper, illustrating the service which science can render to art, deserves a place
in the classics of the motion picture engineers.
There are several features in connection with the material that Mr. Jones has
presented that deserve consideration. Rubens, as Mr. Jones stated, is probably
nearer to the motion picture director than any of the other classic masters. He
could work in a little sex appeal in his paintings, and sometimes he went in for
commercialism rather than for the highest possible artistic standards.
We should, however, keep in mind that his paintings of figures do rarely recog-
nize the architectural features of the background. In dramatic composition the
architectural set must have considerable recognition. If we take a static moment
as is usually presented in the still picture painted or photographed, it is not neces-
sary for us to recognize much of the architectural background, but in the dramatic
composition it is hovering over the characters and must complement their actions.
It is probable that the ultimate proportions of the motion picture frame will be
different from those needed by any single dramatic composition that can be pro-
posed, because you can't establish a background and its dominance of the scene
by a static scene.
MR. FARNHAM: The fact that the projection room is usually located at an ele-
vation above the screen results in projection at an angle. Distortion of the pic-
ture shape makes the screen more nearly square. A recommendation as to the
most desirable picture proportion should specify the picture as it appears on the
screen. A conversion factor based on projection angle will have to be obtained to
determine the projector aperture proportions.
MR. RICHARDSON: Projection angle has in some cases resulted in square pic-
tures; in others, the height has been greater than the width.
DR. HICKMAN: I should like to join Mr. Coff man's tribute to Mr. Jones if I
might. I think this is an extraordinarily stimulating paper.
There are one or two points that occur to me. When an amateur photographer
or artist makes a close-up he afterwards trims the picture to the size he likes best.
The director achieves the same object by vignetting the sides, so that he is chang-
48 LOYD A. JONES [j. s. M. P. B.
ing the effective area to suit his needs. We need the picture which will house the
largest thing we have to photograph, provided the frame lines of which the eye is
always conscious are not offensive. I find a very wide picture an offensive shape.
In looking at the group on the left of Fig. 2 one might be able to choose the most
pleasing shape. I don't know whether the assembly would be interested in ex-
pressing their opinions. I believe the top and the third are the most pleasing for
the normal type of subject.
MR. TAYLOR: I think we want not one proportion for the motion picture
rectangle but that this should be variable with the subject material. Can Mr.
Jones tell us what is called the "Golden Rule" in proportion?
MR. JONES: The "Golden Rule" in proportion is stated as follows, "Height is
to length as length is to the sum of height and length." Mathematically ex-
pressed, this gives a ratio of length to height equal to 1.62. This is the same as the
Whirling Square rectangle ratio.
MR. RICHARDSON: I have received in the past ten or fifteen years four or five
hundred styles of projection apertures sent me by projectionists.
MR. COFFMAN: I believe that regardless of the possibilities of vignetting or
using a mask, at all times you subconsciously work with the proportions of the
whole picture. This will dominate in the composition of the thing as you see it.
MR. JONES: I want to add one or two words. I want to call your attention to
the fact that this paper is a study of one particular factor. There are many others
if you want to extend this into a complete discussion of the best possible solution
of this problem. I have not attempted to deal with other factors. Mr. Farn-
ham's and Mr. Richardson's points are well taken. I did not attempt to consider
them; I was talking specifically about a rather abstract thing.
I want to agree with Mr. Coffman in his opinion that you cannot change the
rectangle proportion by masking. The artist can do a great deal by concentrating
attention on the proportion. He can use displeasing or pleasing compositions
to fill in, but I believe the rectangle proportion will predominate, and it is im-
portant for this to be right.
MR. BALL: One of the great merits of the wide picture is that the borderline
can be removed from consciousness, and that is the reason for the pseudo-stereo-
scopic effect, which is very real and important.
I should like to ask Mr. Jones about the angle and size and shape of that por-
tion of the field of vision which is mostly used. I believe there is a small area of
the retina upon which an image must fall if we are to see with any degree of acuity.
Beyond that limiting angle we are not aware of objects.
MR. JONES: The fovea is relatively small, subtending an angle of about one
degree. It is on this area of the retina that most acute vision is obtained and it is
the spot upon which the image of any object, to which we are giving direct atten-
tion, falls. We are, however, aware of objects well outside of this area and I do
not believe that the angular size of the fovea can play a dominant roll in the
determination of the most pleasing rectangle proportions in pictorial composition.
While things which fall on the peripheral area are not seen as sharply and are
subject to aberrations, they are certainly present in consciousness and do con-
tribute very profoundly to our general impression of the whole visual field. It is
probable that the general shape of the entire visual binocular field has more
influence on the most desirable rectangle proportion than the angular dimensions
Jan., 1930] RECTANGLE PROPORTIONS IN COMPOSITION 43
of the area of acute vision. At an average viewing distance from the screen, it is
probable that an area not more than 2 feet in diameter covers the entire f ovea and
it is obvious that a picture of that size would not be either of pleasing size or of
pleasing shape.
There are many other factors to be considered and I am not prepared at this
time to make a more complete analysis. I should like to emphasize the fact that
the whole discussion presented in this paper relates to the rectangle proportion
and not to the most desirable angular size of picture.
MR. PALMER: I should like to have Dr. Hickman's suggestion carried out
that we have a vote on which of the four proportions (left column, Fig. 2) we like
best.
MR. JONES: Before doing that, I should like to point out that I do not consider
this is a fair test, because you have a rectangle within a rectangle here. If you
want to take any such vote as that, a group of lantern slides should be prepared
and shown one at a time with no contributing distracting surroundings. I have
no objection to your going ahead, but it will not mean anything because you can't
exclude from your judgment the effect of the other things.
MR. PALMER: I agree with Mr. Jones that it would be better to do as he sug-
gests.
MR. ELMS: I think the projection of motion pictures of different proportions
will give you what you want.
DR. HICKMAN: I think one cannot judge without information about the
dimensions of the theater.
MR. JONES: I do not agree entirely with Dr. Hickman. While there are un-
doubtedly extraneous factors in the theater which influence our perception of the
picture, they are in general of a much lower brightness and hence have much less
weight in building up the total visual impression than the picture area itself which
is illuminated to a relatively high level. For instance, in an average theater we
may take it that the screen surface itself has a brightness of approximately
10 apparent foot candles. The illumination on areas outside of the picture is
seldom higher than 0.1 apparent foot candles and when it is considered that the
screen surface is of high reflecting power and the surrounding objects of rela-
tively low reflecting power, it will be seen that the screen surface itself is probably
one thousand times brighter than the surrounding objects. This certainly will
serve to suppress the importance of objects outside of the picture area, and I be-
lieve that under such conditions it would be possible to make a more reliable
judgment as to the most pleasing rectangle proportions. In this room at present
we do not have such conditions and I doubt if our estimates would be of much
value.
THE OPTICAL PROBLEMS OF WIDE FILM MOTION
PICTURES
W. B. RAYTON*
The employment of film wider than the standard 35 mm. seems
imminent. No one can say whether we will have to deal with one
size or several, but, however that question may be settled, the diffi-
culties encountered in designing adequate optical systems are of the
same kind in all cases but differ in degree with the variations in width
of film and size of projected image. It seems probable that they are
of sufficient interest to this Society to justify a brief statement of
them and of the degree to which we have been able to meet the
requirements.
It will probably not be out of place first to set forth the reasons
which are impelling the industry to take a step involving such
drastic changes in equipment while it is still struggling with conver-
sion of equipment to permit sound pictures to be made and repro-
duced. While there may be other reasons, there are two, at least,
discoverable by a brief consideration of sound pictures. The first
rests on the fact that in the sound-on-film processes part of the
area formerly available for the picture now has to be given up for
the sound track. The second reason rests on the possibilities in-
herent in sound pictures which were lacking in the silent pictures of
presenting entertainment more of the nature of spoken drama of the
stage. Although the second of these conditions leads to a demand
for a larger picture area, the first results in an actual decrease in
picture area.
As soon as speech was added to the picture it was found that the
picture area did not allow enough characters to be included in a
scene if the projected images were to appear large enough to be
commensurate with a sufficient volume of sound. The effect of a
series of conversations between two or three characters appearing
in a small, practically square frame in the remote distance is dis-
* Scientific Bureau, Bausch & Lomb Optical Co.
60
PROBLEMS OF WIDE FILM PICTURES 51
tinctly not entertaining after the novelty has worn off. Further,
the producers are ambitious to attempt to record the stage settings
as well as the music of opera and musical comedies.
To meet the situation it is necessary to project a picture in which
the figures remain of a sufficiently large size but which includes
more of them. This means, obviously, a wider included angular
field of view and a larger projected picture.
To accomplish this, two methods of attack occur at once. One
.
method would consist in moving the camera farther from the set
or in using lenses of shorter focal length thereby reducing the size
of the images of the individual components of the set and permitting
more of them to be included. Now, if this picture is projected
through a projection lens of sufficient power to restore the figures to
the customary size on the screen, a much larger total picture size
will result. It will be larger in height as well as in width. Since
we are only infrequently interested in any great amount of space
above the heads of the human figures in the set we would be embar-
rassed with this superfluous space, in general. It would be possible,
however, to reduce the frame height, let us say, to the point where
its relation to the height of the human figures was restored to some-
thing like what we have been accustomed to. Now this all sounds
very good. Several more frames, possibly twice as many, could be
recorded on a foot of film; film consumption would be decreased
and film magazines reduced in size or else hold a much longer record.
This procedure, however, is impractical, first because the resolving
power of photographic emulsions of adequate speed is insufficient to
permit a satisfactory screen image to be obtained by such a process.
Graininess would be very pronounced and detail would be lost.
It would, furthermore, be impractical in the present state of develop-
ment of the optical systems employed in the sound-on-film processes
since it would be impossible to get a satisfactory reproduction of
sound because of the loss of high frequencies. Finally, it is not at
all sure that such a picture could be projected with anything like a
satisfactory degree of brightness.
A modification of this solution was demonstrated at the meeting
of the Optical Society of America at its meeting in Washington in
November, 1928, which is interesting enough to justify examination.
You have probably all observed that if you hold a telescope of any
kind before your eye in a reversed position all objects seen through
it are apparently reduced in size and look more remote. If you hold
52
W. B. RAYTON
[J. S. M. P. E.
a telescope before the lens of your camera you will be able to observe
the same effect on the ground glass. If the telescope be held before
the camera lens in its ordinary operative condition the image on the
ground glass will be larger than the image formed by the camera
objective alone. To be more specific, if we hold a 2X Galilean tele-
scope in front of the camera lens with the objective lens of the
telescope facing the camera as shown in Fig. 1 the size of all the
individual details in the image on the ground glass will be just half
as large as they are without the telescope. If you try this experi-
ment do not be surprised, however, if the total image fails to cover
the whole ground glass area; the ordinary Galilean telescope optics
serve only to demonstrate the principle but will not give results of
any value. Provided, however, the optical system was satisfactory
we would have achieved a result identical with the result we might
FILM
CAMERA LENS
fcx GALILEAN TELESCOPE
FIG. 1. A photographic lens to which a 2X Galilean
telescope is added to reduce the focal length to half of its
original value.
have obtained with a new camera objective of just half the focal
length of the original. You will remember that this is one of the
expedients mentioned a moment ago for increasing the angular field
of view. The proposal under examination, however, is unique in
that instead of lenses with spherical surfaces it employs lenses with
cylindrical surfaces so that the added telescope, if we may still call
it such, has magnifying power in one direction only, while in the
direction at right angles it has no optical effect at all. If such a
system be added to a camera lens it will have the effect of apparently
altering the focal length of the latter in one diameter while having
no effect on focal length in a second diameter perpendicular to the
first. If the added system be located such that its active plane is
horizontal we would be in effect taking a picture through a lens of,
Jan., 1930]
PROBLEMS OF WIDE FILM PICTURES
53
let us say, two inches in the vertical plane and one inch in the hori-
zontal. The result would be that all vertical lines would be brought
closer together and more space could be covered in the horizontal
plane while the height of the figures would be normal for a 2 in. lens.
The image on the film would be a very unusual looking image but
projected through a projection lens with a similar added cylindrical
system it will be restored to normal proportions and theoretically
the projected picture would give no indication that it has been sub-
jected to such unusual treatment.
If an optical system of this type could be designed to work satis-
factorily in respect to speed and image quality, a task bristling with
difficulties, it would overcome the difficulty mentioned earlier of
poor sound reproduction and it would probably be somewhat easier
FIG. 2. Illustrating the meaning of the expression
"angular field of view." AO// equals tangent of one-
half of angular field of view.
from the illumination standpoint. From the standpoint of image
quality, however, even neglecting the effect of aberrations in the
added system itself it is not obvious that we would obtain results
of any better quality than we would secure by photographing with
an ordinary photographic lens of correspondingly short focus and
projecting with correspondingly higher magnification.
We would, to be sure, have the great reduction in photography
and the extraordinary magnification in projection in the horizontal
plane only instead of in all directions but it does not seem likely
that this would reduce in any appreciable degree the difficulties due
to grain and limited resolving power of the film.
The successful application of the methods previously outlined
imposes problems on both the lens designer and on the emulsion
54
W. B. RAYTON
[J. S. M. P. K.
maker. There is one possibility, however, which leaves the film
manufacturer free from embarrassment in so far as his emulsions are
concerned but which still depends for its success on the lens designer.
The method referred to consists in enlarging the picture area without
changing the focal length of the lenses. This, translated in optical
language, calls for both photographic and projection lenses of larger
field of view. For the sake of any who may be unfamiliar with the
meaning of the term field of view it may be well to explain that the
quotient of half the diagonal of the picture area divided by the
focal length of the lens is the tangent of half the angular field of view.
AO *w
Referring to Fig. 2, = tan where / is the focal length of the
/ 2
lens and w is the angular field of view.
The commonly used focal lengths in motion picture practice run
from 40 mm. to 150 mm. Lenses both shorter and longer are used
on occasion but not frequently. The following table presents the
values of the angular fields of view demanded by three different
picture areas for lenses within these limits.
Table of Angular Field of View
Focal Length
of I/ens
19 X 25 Mm.
Picture Area
18 X 36 Mm.
23 X 46 Mm.
40 mm.
42 52'
53 24'
65 28'
50
34 52
43 50
54 26
75
23 38
30 02
37 50
100
17 50
22 46
28 50
Beyond doubt the most popular lens in motion picture photography
is the 50 mm. lens. On standard film the field of view covered is
slightly less than 35. For the 23 X 46 mm. picture area the field
covered is practically 54V2. This is not by any means an unheard-
of angle in lenses of relative aperture of //4.5 or even//3.5 but no
photographic lens appeared to be available with sufficient speed
and satisfactorily sharp definition to cover a picture size 23 X 46 mm.
at the time this size was first attempted. I am happy, however, to an-
nounce that I have been able to design a 50 mm. lens of a relative
aperture of //2.3 which covers this area very satisfactorily. An
attempt has been made in Fig. 3 to indicate the quality of its per-
formance. To cover the field with lenses of longer focal length is a
task of less difficulty, but here one must guard against a deteriora-
Jan., 1930]
PROBLEMS OF WIDE FILM PICTURES
55
tion of general definition due to residual aberrations which become
the more noticeable the longer the focal length.
Now, it would not be strictly necessary for the production of the
wide film pictures to have lenses as short as 50 mm. in focal length.
If the distance from camera to set could be chosen at will, any given
area which can be photographed with the desired reduction on a
film of given size can be photographed at the same scale of reduc-
tion on a film of the same size with a longer focus lens. Two ob-
stacles present themselves however; first, the distance from camera
to set becomes too great involving excessive expense in studio space
and, second, the perspective of the view becomes flatter. The latter
might be overcome by a different arrangement of the set but this
FIG. 3.
Reproduction of 23 mm. X 46 mm. shot made with 50 mm.,//2.2
Raytar lens.
again involves increased expense as compared with the possibility
of varying perspective by the simple process of selecting the camera
lens of most appropriate focal length.
After the pictures have been taken the problem of projection offers
difficulties in illumination and in finding a projection lens competent
to project them with satisfactory definition.
It is obvious that if the same amount of light which passes through
the aperture of the film gate in an ordinary projector be spread over
a screen area twice as large the illumination of the screen image will
be only half as great. If a pair of ordinary 4 x /2 in. condensers and
high intensity arc be employed in their usual adjustment it will be
found impossible to illuminate an area 23 X 46 mm. The illuminated
56
W. B. RAYTON
[J. S. M. P. E.
area in the plane of the film is not large enough. The size of the
illuminated area can be increased, however, by reducing the distance
from arc to condenser. An adjustment can be found in which the
spot at the film gate will be large enough to circumscribe the 23 X
46 mm. rectangle. Such a condition is represented in Fig. 4. It is
obvious that much light will be intercepted by the film gate, but
still the illumination will be greater than we might expect as a result
of comparison of screen image sizes. In reducing the distance from
arc to condenser we have increased the amount of light picked up by
the condenser and we are not limited entirely to the light flux which
FIG. 4. Ordinary round spot projected on the
plane of the film showing great loss of light for
pictures of 1:2 ratio of height to width.
passed through the aperture in the film gate while we were projecting
ordinary 35 mm. film.
The old 4*/2 in. diameter condensers with the high intensity arc,
however, did not exhaust the possibilities of the projection lens in
respect to its angular aperture. One obvious means of increasing
illumination, therefore, lay in employing condensers of larger con-
verging angle. Since the approach of the arc to the condenser can-
not be carried on indefinitely this led at once to larger condensers.
We found it possible to obtain a marked increase in angle with
condensers of 6 in. diameter with aspheric surfaces, of course. A
substantial increase in illumination resulted.
Jan., 1930]
PROBLEMS OF WIDE FILM PICTURES
57
Some additional illumination, however, is possible by using an
astigmatic condenser, one whose focal length in one meridian is shorter
than its focal length in the other principal meridian. Such a con-
denser can be realized by employing one cylindrical surface, as we
have done for several years in one of our ophthalmic instruments,
or by employing a toric surface. Such a condenser will yield a spot
of light in the plane of the film such as is shown in Fig. 5. A pre-
liminary investigation subject to possible correction indicates a
gain of something like 25 per cent obtainable in this manner.
If, now, the arc be run at something like 150 amperes with con-
densers as described above a satisfactory illumination will be found
possible. It still remains a question as to just what degree of illumi-
nation will be required. It is possible that the relatively enormous
FIG. 5. Elliptical spot of light results in less loss by
interception than in the case of a round spot.
picture on the screen may prove more satisfactory at a level of
brightness lower than we have been accustomed to in the smaller
picture. Certainly, a projected picture of, say, 23 X 46 feet illumi-
nated as brightly as some of the' news reels we see might be expected
to raise the general illumination of the theater to an undesirable
level.
For the projection of the pictures ordinary projection lenses are
entirely out of question except in the longest focal lengths because
of objectionable curvature of field. It happened that I had been
working on an improved form of lens for the shorter focal lengths
for the projection of ordinary film when the demand came for lenses
to project the large pictures. The design had progressed to the point
where it was possible to offer lenses of 4 in. equivalent focal length
58 W. B. RAYTON
and of a speed of f/2.2 which projected a picture 23 X 46 mm. with
satisfactory results. Since then it has been found entirely possible
with lenses of 3 in. focal length. These lenses are, of course, an-
as tigmats.
For the benefit of those who may have seen the demonstrations,
I might say that both the Grandeur Film shown at the Gaiety Theater
in New York and the earlier demonstration by Paramount Famous
Lasky were for the most part accomplished with the aid of the
optical developments described above.
SOME PRACTICAL ASPECTS OF AND RECOMMENDATIONS
ON WIDE FILM STANDARDS
A. S. HO WELL AND J. A. DUBRAY*
THE DESIRABILITY OF WIDER FILM
Modern motion pictures, and especially motion pictures syn-
chronized with sound, have of late brought about a new problem
bearing within itself as far reaching consequences as any problem
the industry has had to face since its advent. We refer to the
obviously insistent demand for a complete departure from old
established standards and the creation and establishment of picture
images of more appropriate size and proportions.
The problems which are a consequence of such a change are, in
our estimation, so vast and so vital that we consider it essential
to present to this Society an analysis of the principal factors in-
volved psychological, artistic, technical, and economical, and to
propose a definite recommendation on the course which, in our
estimation, it is the most logical to follow.
Sound pictures of the sound-on-film systems have altered the size
and shape of the screen. From a rectangle whose sides were in the
ratio of 3 to 4, the screen image has become almost square. It has
assumed a shape which not only presents no advantage whatsoever
over the rectangular shape, but which imposes doleful aesthetic
limitations upon the artisans of the screen. The natural conse-
quence of this situation is retrogression in artistic expression and
rebellion on the part of the final judge, the public.
We purposely use the expression, "rebellion," because it is sup-
ported by the fact that, for perhaps the first time in the history of
motion pictures, a number of exhibitors and at least one of the
greatest distributing and exhibiting organizations in America have
taken matters into their own hands and have reduced the height
of the projector aperture. They have considered it essential
to maintain the rectangular form of the screen even at the risk of
* Bell and Howell Camera Co., Chicago, 111.
59
60 A. S. HOWELL AND J. A. DUBRAY [J. S. M. P. B.
cutting off parts of the heads of the performers, or some detail
at the lower part of the picture area essential to the story and part
of the general scheme of composition. Such procedure is rebellion
and, what is more important, it is, seemingly, justifiable.
We do not want to impose upon you a long dissertation on the
reasons which sustain the preference accorded the rectangular
shape of picture in pictorial representations. Volumes have been
written on this subject. The psychological, metaphysical, and
physiological effects and influences that a certain form may have
upon the mind and eye have been analyzed and discussed from
the point of purely aesthetic considerations following complete
and detailed investigations based upon undeniable scientific axioms.
The deductions derived from such analyses have been invoked not
only as proof that a rectangular form is the most logical to adopt
for pictorial representations, but also have led to the establishment
of a definite ratio of 3 to 5 as the dynamic ratio between the sides
of the rectangle. This ratio has been called the "Golden Rule"
of design proportion. It is pertinent to this Society to consider
the influence exerted by these conclusions and their applications
to the motion picture screen.
The main function of motion pictures is to give a faithful repro-
duction of life. It is true that incidents are dramatized, that more
emphasis is given to details, that outdoor scenes are selected with an
eye to scenic beauty, and that interiors are always chosen, dressed
and decorated in accord with the general theme of the story and the
personalities of the characters which are the human elements repre-
senting what we would call an exaltation of emotions. However
the exposition of this essence of life through motion pictures de-
mands truth of presentation and naturalness in even its most minute
details.
An ideal motion picture production is one which causes the on-
looker to forget his own personality and make him live with the
characters of the story and in their ambient. If this psychological
effect is not reached, the picture is classed as indifferent, if not
entirely bad.
One of the most important reasons which make us declare the
square form of the screen objectionable is the fact that the eye iri
its continual horizontal motion is constantly and unnaturally ar-
rested by the black nothingness at each side of the screen. This
barrier, which abruptly arrests the natural horizontal sweep of the
Jan., 1930]
WIDE FII.IV; STANDARDS
61
eye, has an effect entirely opposite to that which the motion picture
artist strives for, and is much more disturbing than the arresting of
vision which takes place in the vertical direction.
Motion pictures are portrayals of life which can be analytically
expressed as figures in an ambient and in which the figure plays the
most important part.
A study of our artistic heritage left to us by the masters of design
will vividly bring forth the proof of the care taken by the artists
to stress the points of interest in a horizontal area. We have se-
lected for demonstration only two sketches, taken at random from
\\rn
J3
FIG. 1. "The Colonel," a pen and
ink sketch in which the center of
interest is contained in a 3 by 5
rectangle.
the illustrations of a work on figure composition by the Honorable
Richard Hatton. A sketch is usually most representative of the
inspiration of the artist since it is executed without taking care of
the minute technic usually displayed in a more finished work.
Fig. 1 shows a pen sketch, the title of which is "The Colonel."
The artist has placed the entire emphasis on the head of the subject.
The shoulders have been given less attention and the rest of the figure
is merely outlined. The whole is extremely pleasing and uncon-
ventional and our attention is forcibly brought to the upper part of
the sketch. If we trace an imaginary line joining the points A and
62
A. S. HOWEU, AND J. A. DUBRAY [J. S. M. P. E.
B, we find that the center of interest is composed within a rectangle
whose sides bear to each other the ratio 3 to 5.
Art has no age and we find that even at the very time when the
world was emerging from the retrograding influence of the Dark
Ages, the psychological influence of the horizontal sweep was recog-
nized by the masters of the epoch, as is strikingly proven by the
etching by Hans Burgmair, illustrated in Fig. 2. Here the artist
has grouped his figures in as compact a group and in as limited
space as the subject and his conception of it would permit; but
through a remarkably fine arrangement of the lances which forces the
eye to follow a natural horizontal sweep, he injected into its compo-
FIG. 2.
An etching by Hans Burgmair which illustrates
a natural horizontal sweep for the eye.
sition that intangible something which spells Space, Breath, Move-
ment, Life.
These two examples have been chosen for their apparent contra-
diction between the nature of the subjects and their relation to a
rectangular frame form. We could multiply these examples ad
infinitum, but we should then lead our minds too far from our sub-
ject, Motion Pictures. It will be sufficient to remark that since,
in life, motion usually takes place in a horizontal direction, our
sense of vision is much more accustomed to a horizontal than to a
vertical sweep.
Since motion pictures are a true representation of motion, it is
essential to provide a sufficient and adequate horizontal breadth
to the screen, image in order to approach more nearly the condition
Jan., 1930] WlDE FlLM STANDARDS 63
that the human eye meets in real life. It is only when this condition
is satisfied that pictures of life and action will be presented in their
most natural form.
No definite reason can be traced which will explain why the
present 3 to 4 ratio has been chosen as the standard for the motion
picture frame size. Perhaps space consideration in the small theaters
which were exhibiting motion pictures in the early days was the
deciding factor in the matter.
Since the time when motion pictures emerged from their chrysalis
and made serious attempts at art, the artisans of the screen have
constantly been striving to make the best out of a rather irregular
situation. One of their constant cares has been to fill the fore-
ground. The era of silhouetted objects in the foreground arrived.
A piece of furniture in an interior, a pile of stones, a hedge or fence
in an exterior, served the purpose which can, at the end, be analyzed
as an effort to elongate the screen in a horizontal direction. Dark,
heavy masses across the lower part of the screen will force the eye
away from them and limit its field of vision within the brilliant area
of interest, usually covering approximately two-thirds of the upper
part of the screen.
These expedients were very cleverly resorted to and at times taken
advantage of with characteristic boldness and very fine results.
They were, nevertheless, expedients, and when talking pictures came
to annihilate the already scanty resources which were at the dis-
posal of the artists of the screen, a cry of protest arose, especially
from cinematographers and art directors, who were most affected
by the new state of things.
Directors and producers felt keenly on the subject and sympa-
thized with cinematographers and art directors. Directors needed
a greater freedom of action and new means through which they
could tell the story in a much more natural way by properly de-
veloping the new technic of talking pictures and arranging the
balanced distribution of dramatic points of interest. Producers
realized the fact that motion pictures cannot survive if not presented
to the public under the most favorable conditions of technical and
dramatic perfection.
Other factors besides the psychological and artistic considerations
thus far expressed must be taken into consideration.
We are convinced that everyone having some knowledge of the
technicalities of motion pictures agrees with the fact that a change
64 A. S. HowEUv AND J. A. DUBRAY [J. S. M. P. B.
in screen size and proportions cannot be satisfactorily brought
about by reduction of the picture area, but involves, on the con-
trary, its increase. It would perhaps require too much time and be
too tedious to enumerate here all the quite obvious technical reasons
which lead to this conclusion.
What is perhaps less well known are the problems that the di-
rectors of photography encounter in that all-important phase of their
work which relates to the lighting of motion picture sets. The
square, or nearly square, shape of the picture area has been the
cause of building sets of height disproportionate with their width
and depth. The back lighting effects, which are so essential to a
rendition of pleasing roundness and relief in the finished picture,
and which are obtained by placing spotlights at strategical points
high up on the set, have always presented serious problems to the
cinematographer, due to the excessive height of the sets themselves.
On many occasions the so-called back lightings are nothing less than
top lightings which have to be corrected with painstaking and difficult
manipulations of the floor lighting system. The architects of the
screen are also confronted with serious and, we might say, unnecessary
problems in the design of the composition of the decorative schemes.
And so on down the line through the legion of those responsible
for the artistic presentation of pictures, the square shape of the screen
is considered as a stifling curse which limits the possibilities of
expressing beauty and harmony.
The demand for a change in the proportions of the screen is not a
mere desire to give the public a "bigger show," as has been stated
at times, but is, in our estimation, one of the most striking and
significant steps in the evolution of the motion picture art.
PROPOSED FILM DIMENSIONS AND PROBLEMS PERTAINING TO THEIR
ADOPTION
It is very obvious that an alteration in the proportion and size
of the motion picture image creates complex problems which involve
all branches of the motion picture industry and which are of such
nature that they demand the close attention and cooperation of
all allied industries. The reaching of definite conclusions in regard
to this new development must follow a very definite plan, worked
out in complete detail as to the technical problems involved, and
with a perfect understanding of the economic condition created.
It is necessary that the plan can be met not only by the motion
picture industry as a producing unit, but also by the exhibitors
Jan., 1930]
WIDE
3TANDARDS
65
of motion pictures, in such manner as to insure the endorsement
of the public.
It is in consideration of these factors that the Bell & Howell
Company, conscious of the responsibilities of the motion picture
industry toward itself and toward the public, has conducted a pains-
taking investigation of this vital question. It has derived from it
some definite conclusions which have led to the presenting of three
dimensional proposals.
Departing from the commonly accepted routine, we shall first
m
te
ts-
T r
FIG. 3. Proposed dimensions of wide films compared with the 35 mm.
standard. (A) 35 mm. film. (B) "Economic." (C) "Spectacular." (D)
"Extreme."
present our recommendations and afterward detail the reasons which
have led to them. To facilitate the discussion, we shall distinguish
the proposed dimensions as follows: (A) the "Economic;" (B) the
"Spectacular," and (C) the "Extreme."
The "Economic" has been so named because its adoption would
involve a minimum of expenditure of both time and capital for the
necessary alterations and developments of the apparatus in use
throughout the motion picture industry.
The "Spectacular" is so called because it presents greater possi-
66 A. S. HowELL AND J. A. DUBRAY [j. s. M. P. E.
bilities than the "Economic" in the matter of refinement of execu-
tion, and lends itself to a more spectacular presentation of pictures.
The expenditure involved in the adoption of this dimension as
standard would be far greater, perhaps three times the expenditure
necessitated by the adoption of the "Economic."
The "Extreme" is so designated because its adoption would in-
volve extreme expenditure of time and money in its development.
It would require perhaps four to five times the expenditure involved
in the "Economic," and it would present extreme, perhaps excessive
abuses in exploitation without accomplishing any great advantage
over the "Economic."
Fig. 3 shows, in one illustration, for the purpose of comparison,
the three dimensions and their characteristics together with the
standard film in use today. The most apparent features which
are common to each of the three proposed dimensions are:
1. The sides of the rectangular images are in all instances in the
ratio of 3 to 5 in opposition to the 3 to 4 ratio in force according to
the present standards, and also in opposition to the 3 to 3.5 ratio of
the present standard 35 mm. sound-on-film pictures.
2. The position of the sound record is outside of the film perfora-
tions.
3. The dimensions of the perforations are the same for the three
proposed dimensions and are equal to those of the standards in force.
4. The rectangular perforation with rounded corners is recom-
mended for both negative and positive films.
The proposed dimensions differ from the existing standards
in that the over-all width of the films and of the picture frames is
greater than the same dimensions adopted for the standard 35 mm.
film. In the case of the "Spectacular" and the "Extreme," the
height of the image is increased so as to answer the condition of
the 3 to 5 ratio between the sides of the image area. These di-
mensions will be analyzed in detail later on in the course of this
paper.
It will be noticed that the pitch and all other dimensions of the
film perforation have been kept equal to the standard 35 mm. in
force at the present time. This feature permits reducing to a
minimum the problem of sprocket design for all motion picture
machinery and permits the industry to take full advantage of the
knowledge it possesses of the behavior of film in regard to shrinkage.
This laboriously acquired knowledge has formed the basis of long,
Jan., 1930] WlDE FlIvM STANDARDS 67
painstaking, and complete investigation, upon which the shape,
thickness, diameters, and gauges of sprockets and teeth design
have been based.
We do not believe that the increased width of the film, at least
for two of the proposed sizes, will demand an increase in its thick-
ness. This thickness should remain according to the adopted
standards of 0.006 in. or 0.1524 mm., since the proposed dimensions
are within the accepted tolerances pertaining to the relation existing
between critical width, critical length, and critical thickness of the
film.
This is an all-important consideration, not only because of the
fact that an increase in film thickness would necessitate a long and
exhaustive research on its shrinkage characteristics, but also be-
cause of the fact that an increase in thickness would present serious
problems for the correct registering of the sound record on film,
because of the more pronounced and extended halation fringes
which would be produced by the inevitable reflections of light from
the back surface of the film base. These characteristic halation
fringes have proven at times to be the cause of distortions in the
reproduction of sound, even when using the 35 mm. film of standard
thickness.
The recommended form of perforation is the rectangular with
rounded corners, for both negative and positive film, because it
will permit the marginal guiding of the film (which, incidentally,
will take place on the sound record side) to be controlled at the
lateral faces of the perforations independently of the edges of the
film.
This perforation control is to be preferred to the edge control used
today because it will greatly reduce the possibilities of even the
slightest error in registration. The guiding of the film by the
perforation faces will permit what we may call a "unit control" for
all machinery used in perforating, photographing, printing, splicing,
and projecting. This control will be practically independent of the
shrinkage that the film surfers during the laboratory processing
operations. The advantages of such control are quite obvious.
We would mention that it would prove invaluable in color processes
and that in sound printing and reproducing it would afford a more
assured control of the possible side motion of the sound record.
A change in film size would necessarily involve mechanical re-
construction of all motion picture apparatus. Therefore, a com-
68
A. S. HOWELL AND J. A. DUBRAY [J. S. M. P. E.
plete change in the standard shape of the perforation could be made
without extraordinary inconvenience to the industry.
The sound record is located, for all proposed dimensions, outside
of the perforations, because it may be found advisable in future
times, for economical and mechanical reasons, to use in the photo-
graphic camera negative films of a width narrower than that of the
finished prints a width sufficient to include only the picture record
to the exclusion of the additional width of the sound record. This
would be in accordance with the practice of photographing the sound
record independently and with different apparatus than that used
for photographing the picture record.
The placing of the sound record outside of the perforations has
also the important effect of reducing to a minimum the distance
between perforations and guide control rails, thereby providing
better support for both the picture and the sound records.
d
d
a
d
a
q
a
FIG. 4. Film support in regard to position of perforations.
Fig. 4 represents such a condition. Where the perforations
are situated near the edge of the film, the film itself is unsupported
for a greater length, as shown in the section, than is the case where
the perforations are located nearer each other. It is quite obvious
that the greater the gap between the two supporting points, the
greater are the possibilities for the film to bend or curl out of the
position of essential flatness, which must necessarily be kept within
extremely small tolerances.
Up to the time of writing of this paper, it was quite evident that
the sound engineers engaged in research and development activities
were quite undecided and reluctant about expressing themselves
with regard to the best arrangement for the sound record. This
was evidently due to the complexities and the large number of
factors involved in the problems which were presented to them for
solution. It seems logical, however, to reach the conclusion that
a longer sound record per picture area would permit the recording
Jan., 1930]
WIDE FILM STANDARDS
69
of higher frequencies than is possible on the present standard sound
record length. It is also quite apparent that a wider sound record
would permit an increase in the volume of sound during reproduction.
Increases in the length and the width of the sound record in-
volve, indeed, many problems and considerations which we hope
will be brought to the attention of this Society. We may, never-
theless, mention that the advisability of separating the sound record
from the picture record, not only during the process of recording
but also during that of reproducing in order to record higher fre-
DIA. OF CIRCLE DIA. OF CIRCLE DIA OF CIRCLE
30.03 MM - 1.1823" 35 20 MM - 1.386" 43.74 MM -1.722 "
AREA OF CIRCLE AREA OF CIRCLE AREA OF CIRCLE
7.083 CM 2 9.736 CM 2 15.03 CM 2
1.098 SQ.IN. 1. 509 SQ. IN. 2.329SQ INI.
PROJECTOR APERTURE PROJECTOR APERTURE PROJECTOR APERTURE
22.99 MM X 17.26 MM 28.76 MM X 17.26 MM 35.53 MM X 21.31 MM
.906"X .6795" 1.1325" X.6795" 1.3987" X.6392"
DIA. OF CIRCLE
53. 42 MM - 2.103"
AREAOFCIRCLE
22.41 CM 2
3.474 SQ.IN.
PROJECTOR APERTURE
43. 31 MM X 26 MM
1.705" X 1.0236"
FIG. 5. (1) Area of aberrationless covering power of photographic lenses
required for 35 mm. and larger area films. (2) Focal lengths required to
cover larger images compared to a 50 mm. lens with 35 mm. film image.
quencies than those which are obtained today, has been expounded
and supported by arguments of both technical and economical
nature.
In considering the changes of Dimensions in the sound record,
Bell & Howell engineers have kept present in their minds the possi-
bility of new developments. The proposed new dimensions and
position of the sound record offer the advantage that such altera-
tions, in either the direction of expansion or contraction, would
require but little, if any, mechanical modifications in the apparatus
constructed according to the new proposed standards.
70 A. S. HowEUv AND J. A. DUBRAY [j. s. M. p. E.
Since we are at the present time in the field of generalities, it may
be appropriate to survey the problems pertaining to the photo-
graphic and projection optical systems.
In Fig. 5 (1) are shown at B, C, and D, the areas of aberrationless
covering power that a photographic objective must possess for the
three proposed new dimensions, and, at A, for the 18 X 24 mm.
image dimension, which is the standard in force for the 35 mm. film.
Both camera and projector apertures have been traced.
Photographic Objective. In Fig. 5 (2) the photographic objective
is represented in its simplest expression, with the point N repre-
senting a system in which the two nodal points coincide.
If we consider a lens of 50 mm. focal length, focused at infinity
as the standard, since such a lens is the most used in actual practice
for an image size of 24 mm. width, we find that:
A 62.* mm. (2 l / 2 ") lens will embrace the same object space width
for the image size of 30.76 mm. width of the "Economic" dimension.
A 77.2 mm. (3") lens will embrace the same object space width
for the image size of 35.33 mm. width of the "Spectacular."
A 94.1 mm. (3 3 //) lens will embrace the same object space width
for the image size of 46.31 width of the "Extreme" dimension.
If we now take as a point of departure a 35 mm. lens as the shortest
focal length lens used in actual studio practice, we find that in order to
cover the same object space width we shall use, for the "Economic"
dimension, a lens of a focal length of approximately 45 mm., one of
approximately 55 mm. focal length for the "Spectacular," and one of
approximately 67 mm. for the "Extreme."
This brings to our attention the fact that for the same distance
from object to camera, and in order to photograph the same object
space width, the wider area film would require the use of lenses
of longer focal length than those in use today with the 35 mm.
standard film.
This phase of the question is important in regard to the depth
perspective of the sets photographed. There is no question in
our minds that the use of lenses of extremely short focal length,
such as 35 mm., introduces a noticeable and disturbing distortion
in the perspective depth rendition of the average motion picture set.
It is our belief that the use of, say, a 47 mm. lens, instead of a 35
mm., would tend to add to the beauty and naturalness of the picture.
It is well known that studio practice requires that all scenes
pertaining to one single sequence of a talking picture be photo-
Jan., 1930] WlDK FlLM STANDARDS 71
graphed simultaneously with a battery of cameras, equipped with
lenses of different focal lengths. This arrangement permits the
taking of all long shots and close-ups with a single setting of micro-
phones and simultaneously synchronizes all the picture records on a
single sound record.
The cameras equipped with the shorter focal length lenses which
are used for the photographing of the "long shots" are more con-
cerned with the width of the object than with its height. Vice
versa, the cameras equipped with the lenses of longer focal length
and used for the taking of the close-ups are more concerned with the
height than with the width of the object. In other words, the long
shot cameras photograph the ambient, while the close-up cameras
photograph the performers.
For the long shots, and for reasons previously expressed, lenses of
a focal length greater than those in use for the 35 mm. standard
will prove more adaptable in the photographing on larger area
films, since they produce better perspective and a better relation
between the size of the figures and the ambient. On the other hand,
it must be borne in mind that the height of the proposed wide films
is either the same as that of the standard 35 mm. film or not increased
proportionately to the increase of their width. Therefore, in the
photographing of close-ups, where only the height of the subject
is to be considered, practically to the exclusion of its width, and
where the height is to be determined only by a sense of pictorial
composition, lenses of the same, or nearly the same, focal length
as those in use with 35 mm. film will answer the cinematographer's
requirements.
The practical range of focal lengths used with the standard 35 mm.
film varies from 35 mm. to 150 mm. In order to obtain the same
image width in the long shot and the same composition of figures
in regard to height in the close-ups, lenses of the following approxi-
mate range of focal lengths will be used for the larger area images:
47 mm. to 150 mm. for the "Economic"
55 mm. to 190 mm. for the "Spectacular"
70 mm. to 233 mm. for the "Extreme"
The advantages derived from the use of a smaller range of focal
lengths in photographing the different scenes pertaining to the same
sequence are too obvious to be enumerated in detail. We may,
however, remark that^the smaller the range of focal lengths, the
72
A. S. HowELL AND J. A. DUBRAY [J. S. M. P. E:
less noticeable will be the differences in depth of focus, a character-
istic of photographic objectives too well known to warrant discussion
in this paper. We may also mention that the constant use of an
extremely large range of focal lengths imposed upon the cinematog-
rapher by the technic of sound and picture synchronization has
been one of the causes which have justified general severe criticisms
on the photographic quality of talking pictures.
It may prove of interest here to give some consideration to the
covering power of the photographic objectives in use today and to
consider their adaptability to the proposed new dimensions. Let
FIG. 6. Covering power of an//2.5, 47 mm. lens.
us take, as an example, a 47 mm. lens and its adaptability to the
"Economic" dimensions.
Fig. 6 shows the full area covered by an//2.5, 47 mm. focal length
Taylor-Hobson Cooke lens. The actual diameter of the object was
10 ft. and the camera was set 8 ft. 8 in. away from it. The subject was
so prepared and photographed that the rectangle traced in the
center of the circle was reduced on the photographic plate to the size
of the camera aperture for the "Economic." The 8 ft. 8 in. distance
from the lens to the object was decided upon for convenience in
manipulation, with due consideration to the fact that the diameter
of the image area would be only slightly increased over the diameter
Jan., 1930] WlDE FlLM STANDARDS 73
which would have been obtained if the lens had been focused upon
an object at infinity. It is quite logical to conclude that the lenses
of longer focal length which will be used for the "Spectacular"
and the "Extreme" dimensions will also answer the requirements
of sufficient aberrationless covering power.
Although we are aware of the fact that opticians have been de-
signing lenses for motion picture photography with a reasonable
disregard of the aberrations outside of the image portion which is
limited by the size of the motion picture camera frame, we also
believe that the adoption of any one of the three proposed dimensions
would involve no radical change in the present stage of development
of motion picture photographic objectives.
The above brief exposition of the use of photographic objectives
for film of a greater area than the one used as standard today is,
of course, far from being a complete dissertation on the subject.
We have merely introduced in this paper this phase of the new de-
velopment with consideration to studio practice as a corollary to
this survey of the wide film situation.
Projection Problems. The average size of the screen in large audi-
toriums is 18 X 24 feet. This size involves, for the standard full aper-
ture of the 35 mm. film, a 320 times linear magnification and ap-
proximately a 100,000 times magnification in area. The size of the
screen image for this magnification and proposed dimensions would
be*18 X 30 ft. for the "Economic," 22 X 36 ft. for the "Spectacular,"
and 27 X 45 ft. for the "Extreme."
We would mention here that the 320 times linear magnification
has been increased approximately 10 per cent, without apparent
loss of photographic quality, by a number of exhibitors who have
reduced the height of the projector aperture in order to maintain
the 3X4 screen dimensional ratio, and have magnified the 21 mm.
width of the sound-on-film aperture to the 24 foot screen width.
We do believe that this magnification could be increased still
further perhaps up to 400 times, after appropriate projection optical
systems and the light source apparatus have been developed, without
unduly impairing the appearance of the screen image for the optimum
viewing point of the auditorium.
The increase of 25 per cent in magnification would bring the
screen image to 22.5 X 37.5 ft. for the "Economic," 27.5 X 45 ft.
for the "Spectacular," and 33.75 X 56.25 ft. for the "Extreme."
We shall consider this magnification as reaching the extreme per-
74 A. S. HOWELL AND J. A. DUBRAY [j. s. M. P. E.
missible limits which can be attained without undue loss in image
quality, and we shall rapidly survey the factors involved.
It is our first thought that a screen greater in width than 37 feet
would be quite distracting to the intimate character of most of the
scenes which form the average story telling photoplay.
There is no question in our minds, however, but that some pictures
of an exceptionally spectacular nature would be shown to better
advantage on the 45 foot screen corresponding to the "Spectacular"
dimension. This film width, however, involves a picture height of
27.5 feet, which may be found to be excessive because of the great
effort imposed upon the eye by its eagerness to cover rapidly such a
large span in a direction opposite to its normal sweep. A reduction
in this height of the image would defeat the 3 to 5 ratio between
the image sides and would give rise to a hybrid shape, in most cases
unpleasant to the eye and difficult to manage artistically, as well
as mechanically.
We find ourselves also facing other problems of a more technical
nature, which we shall rapidly survey.
Although a greater screen image, as well as the diffusing surfaces
of the screens used in the projection of talking motion pictures,
broaden the viewing angle in regard to correct distribution of illu-
mination, they also increase the distance of the optimum viewpoint
from the screen.
Without entering into a long discussion of this phase of our survey,
we shall mention that these factors considerably reduce the number
of seats in the front part of the auditorium from which the screen
can be viewed under acceptable conditions of good visibility in
regard to light distribution of the screen surface and picture per-
spective. These factors assume serious proportions, especially if
we take into consideration the great number of small auditoriums
disseminated throughout the country. Furthermore, the greater
the increase in size of the film image, the more complex are the
problems involved in the design of the appropriate optical system
for the projection apparatus.
It is quite obvious that a greater film image area demands a
greater condenser magnification. Although we believe that the
"Economic" dimension would permit the use of existing condensers,
we want to suggest that image sizes greater than this, and especially
those as great or greater than the "Extreme" dimension, would
demand not only a complete redesigning of the condenser system,
Jan., 1930] WlDE FlLM STANDARDS 75
f
but would even require a greater area of the cathode spot of the pro-
jection carbon lamp in order to have the condenser system suffi-
ciently filled by the rays of light emitted by it. This alteration
would necessarily require the discarding of all carbon lamps and
lamp houses of the projection apparatus in use today.
The above briefly outlined considerations seem to confirm the
inadvisability of taking into consideration extremely large film
sizes as well as extremely large screen image areas, and seem to
suggest a reduction in the accepted image magnification in preference
to its increase for the film image of an area greater than the "Eco-
nomic" or the "Spectacular."
If this course should be decided upon, we would indeed obtain
better projection in regard to photographic rendition and screen
illumination, and at the same time reduce the problems pertaining
to the development of projection optical systems. We wish, how-
ever, to state that we do not consider these advantages of sufficient
magnitude and importance to warrant the great expenditure of time
and capital which would be necessary to bring about the mechanical
developments necessitated by the adoption as a standard of any
too great film image area.
In further consideration of the optical system of the projector,
we may mention that since projection lenses are usually of the Petzval
type, and that since the standard picture area of the 35 mm. film
is approaching the limit of its aberrationless covering power, the
adoption of larger image areas would probably mean a complete
departure from the present practice of projection lens design and
would demand the development by opticians of projection lenses
of the anastigmatic type.
This apparently inevitable development in projection optics
applies to any image area greater than the standard area of the 35
mm. film, but would involve only a minor economical consideration,
in view of the greatness of the present movement in favor of wider
area films.
MECHANICAL OPERATIONS INVOLVED IN THE ADOPTION OF NEW STANDARDS
In the third and last part of this paper we shall consider more in
detail the dimensional characteristics of the three proposed picture
areas. We shall, in so doing, invert the progression of presentation
and consider the three sizes in the following order, first, the "Ex-
treme," second, the "Spectacular," and third, the "Economic."
76
A. S. HOWELL AND J. A. DUBRAY [J. S. M. P. E.
Fig. 7 illustrates the dimensions of the "Extreme." The pro-
posed height of the picture is 27.79 mm. for the camera aperture
and 26 mm. for the projector aperture. The height of the camera
aperture corresponds to the sum of the pitch of six perforations
less a dividing space between picture frames 0.71 mm. in width.
The proposed width of the picture is 46.31 mm. for the camera
aperture and 43.31 mm. for the projector aperture. The width
of the space available for the sound record is 5.08 mm. or double
the width available in today's 35 mm. standard film for the same
purpose. The over-all width of the film is 61.31 mm.
CK1II W0^CTt
m*T-JKC APBMTUK
FIG. 7. Dimensions for the "Extreme."
If we consider a speed of 24 pictures per second as the standard,
the length of sound record recorded per second would be 684 mm.
as compared with 456 mm. for the 35 mm. standard film, or an
increase of 1.5 times. It is apparently the consensus of opinion
that the frequency which it is possible to record is proportional to
the running speed and, therefore, to the length of the sound record.
Considering this as a true expression, it appears logical to suggest
that the high frequencies which it would be possible to record with
the "Extreme" dimension would enhance the quality of sound
reproduction.
Jan., 1930]
WIDE FILM STANDARDS
77
The possibility of varying the width of the sound record, if future
developments in this field should so require, is apparent, as the
sound record is placed outside of the film perforations.
With the "Extreme" dimensions here presented, the picture area
would be nearly three times the picture area of the 18 X 21 mm.
sound standard in use today.
The dimensions of the "Spectacular" film size are illustrated
in Fig. 8. It is seen that the proposed height of the picture is
22.8 mm. for the camera aperture and 21.31 mm. for the projector
CAMER* ^ PWOoB-CTOfr 79 nil A '
MwruiB\ *rmi*ru*' jOs" "~Sy
P05ITIVI FILM
tMjLsiON UP- PICTURE RI&MT SIDE UP
NEGATIVE FILM
EMULSION DOWN -PICTURE Rl&HT SIDE UP.
FIG. 8. Dimensions for the "Spectacular."
aperture. The dimension of the camera aperture corresponds
to the sum of the pitch of five standard perforations less a dividing
space between picture frames 0.95 mm. in width. The proposed
width of the picture is 38 mm. for the camera aperture and 35.53 mm.
for the projector aperture. The space available for the sound
record has a width of 3.25 mm., or a little over 25 per cent more
than that of the sound record as used today in the 35 mm. standard
film. The over-all width of the film is 52 mm.
Again, the position of the sound record is outside of the perfora-
78 A. S. HOWELL AND J. A. DUBRAY [J. S. M. P. E.
%
tions, and if we consider a speed of 24 pictures per second as the
standard, the length of sound record registered per second would
be 570 mm. as compared with 456 mm. for the standard film*of 35 mm.
width, or an increase of 1.25 times.
Again, the possibility of varying the width of the sound record
for further possible developments is apparent.
Both these dimensions, "Extreme" and "Spectacular," and
especially the first, would involve, if accepted, considerable expense
due to the necessity of bringing about entirely new developments
in the different apparatus in use in motion picture production,
film processing, and exhibition.
This reconstruction of apparatus would involve complete re-
designing of perforators, cameras, printers, developing machines
splicers, and all other minor laboratory apparatus, as well as re-
quire a reconstruction of projectors, involving extreme develop-
ments which could not be devised and put into execution before a
considerable length of time.
The "Extreme" proposed dimension, especially, would also
present not a little difficulty in the solving of the problems per-
taining to film shrinkage and to the evident necessity of maintaining
the films in a perfectly flat position at the critical operating point,
or area, in all motion picture apparatus.
We would suggest that unless the "Extreme" dimension per-
fectly meets the sound recording and reproducing requirements
not only at the present stage of development, but with due con-
sideration to future possible developments, it should be considered
only with a good deal of caution and forethought.
The "Spectacular" dimension, though requiring considerable
mechanical engineering development, would nevertheless present
some distinct advantages which may compensate for the expense of
time and capital involved.
We shall now review the dimensions of the "Economic" proposal
which are shown in Fig. 9.
The proposed height of the picture is 18.29 mm. for the camera
aperture and 17.26 mm. for the projector aperture. The height
of camera aperture is equal to the same dimension standardized for
the 35 mm. film and corresponds, therefore, to the sum of the pitch
of four perforations less a dividing space 0.71 mm. in width. The
proposed width of the camera aperture is 30.76 mm. and the pro-
posed width of the projector aperture, 28.76 mm. For the same
Jan., 1930]
WIDE FILM STANDARDS
79
picture height the new dimension is nearly 1.5 times greater in
width than the standard film in use today. The space available
for the sound record is 5.08 mm. or double the space available for
the sound record in the standard 35 mm. film. The over-all width
of the film is 46 mm., and the width of the silent film may be re-
duced to 41.16 mm., should the decision be taken to eliminate the
sound record space in the taking of the picture records.
The position of the sound record is, as in the other two proposed
dimensions, outside of the perforations, and offers the same ad-
IIS-"""
FIG. 9. Dimensions for the "Economic."
vantages in regard to expansion or contraction of its width, as well
as to the possibility of its severance from the picture record.
The length of the sound record is, according to this proposed
dimension, and always considering a speed of 24 pictures per second,
equal to the length of the sound record standardized for the 35 mm.
film.
If we are willing to concede that the limits of perfection are near
enough at hand in the present system of sound recording on film,
then it is safe to say that in order to record faithfully all desirable
80 A. S. HOWEXL AND J. A. DUBRAY [J. S. M. P. E.
frequencies of the sound scale, it would perhaps be necessary to !
increase the running speed of the film to perhaps three, or possibly
four, times the speed at which it would be practical or correct to
run the picture.
If this difference actually exists, it would appear that any attempt
in the direction of enlarging the film size sufficiently to do full justice
to the adequate running speed of the film sound record would necessi-
tate an even greater enlargement of the picture area than the en-
largement proposed for the "Extreme" dimension.
At this point of the survey we find it necessary to bring up the
points of financial and commercial consideration involved in the
question which has formed the subject matter of this paper. Al-
though we do fully realize that commercial considerations are quite
incompatible with the work conducted by a scientific and technical
society, we, nevertheless, consider that a change in motion picture
standards is of such consequence and import that the financial side
of the question cannot be overlooked.
We do not think that we would be very far from the truth if we
would mention the fact that the partial reconstruction of machinery,
in order to adapt it to the "Economic," would represent an approxi-
mate investment equal to from 40 to 60 per cent of the value of
the apparatus in use, while the "Spectacular" dimension, which
would call for duplication of all apparatus already manufactured,
would involve an expenditure which we estimate at over 150 per
cent of the investment by the industry for the apparatus in exist-
ence.
The "Extreme" dimension, due to the engineering developments
which would be required, would bring the investment to a figure
which we conservatively estimate would be equal to approximately
200 to 300 per cent of the present investment. These figures,
which, we hasten to say, are only approximate, are dictated by
our own experience in cinematographic matters, and although not
based upon actual statistics, we do not hesitate in presenting them
for your consideration, since we consider them as nearly an ex-
pression of the facts as can be roughly estimated.
Alteration of machinery for the "Spectacular" and especially for
the "Extreme" dimensions would mean a complete scrapping of all
apparatus in existence. It would involve change of dimensions
of all parts, which would necessitate as a consequence the redesigning
and remaking of all tools necessary to their production. The
Jan., 1930] WlDE FlLM STANDARDS 81
"Economic" would involve increases of dimensions in one direction,
width only, which would permit a salvage of approximately 40 to
60 per cent of machinery parts in existence, and permit the use of
most of the tools accumulated through the years by machinery
manufacturers.
Finally, we wish to bring to your attention the fact that the
"Economic" dimension would represent a time saving in getting
under way, which we estimate at 50 per cent of the time required to
complete the adaptation of the "Spectacular" and 75 per cent for
the adaptation of the "Extreme." Engineering developments
in motion picture machinery are necessarily slow, due to the re-
search necessary to arrive at perfection of design and manufacture
as is required by the extremely reduced tolerances permissible.
We estimate the engineering development, necessitated by the
"Economic" dimension, could be completed in approximately four
to six months. Those for the "Spectacular" would demand from
six months to one year, and the "Extreme" would require not less
than from eight to eighteen months. This estimate of the time
element is expressed only in regard to the engineering develop-
ment, and not in regard to the time which would be required for a
complete change-over within the industry from the present to the
new standards. The industry itself will, of necessity, be called upon
to determine this factor.
An improvement as radical as a change in dimensional standards
must of necessity be brought about with a broad visualization of
future possibilities and so completely that it will present a reasonable
guarantee of stability for years to come. It also demands that its
adoption should not bring a halt or a reduction in the activities
of either the production or the exhibition fields.
It is our opinion that the production end of the industry is more
concerned with the technical and the spectacular advantages which
are to be obtained through the introduction of a new standard,
than with the expenditure involved. It is not illogical to consider
that the change would handicap and perhaps meet with strong
opposition from the exhibitors, especially from those who confine
their activities to small theaters. Furthermore, the time element
involved in the complete change-over is of special interest to both
producers and exhibitors.
It will undoubtedly be found necessary to have recourse to a
system of interchangeability between the standards in force and
82 A. S. HowEUv AND J. A. DUBRAY [J. S. M. P. E.
those which will be adopted. It is difficult to foresee to what extent
this problem of interchangeability will be solved. It may be possible
that some arrangement be devised in the projection apparatus
whereby one machine could be made to be interchangeably adaptable
to run both sizes of film, or some arrangement by which one pro-
jector could be changed for another of different size with reasonable
celerity whenever the program of the show demanded it.
Arrangements of this type would be in order during the time in
which the production end of the industry would effect the change-
over, and during the time for which 35 mm. films would be distributed.
The complete change-over in the exhibition end will necessarily
be a much slower process and will present obstacles the overcoming
of which may appear too great a task to many less aware than we
are of the resourcefulness of the engineers of the screen.
We venture to say that the solution of these problems may lie
in the development of optical reduction printing processes in order
to make possible the distribution of films to small theaters. As
an example we may mention that if the "Spectacular" dimension
should be chosen as standard, the negative image could be so re-
duced in the prints as to include four perforations only in its height.
This reduction of the image height would call for a 25 per cent
reduction of the sound record, which seems at first thought to possess
possibilities of execution.
CONCLUSION
In consideration of all the factors of an artistic, technical, and
economic nature pertaining to a change in film dimensional standards
which have been merely outlined in this paper; in consideration
of the fact that a change of film dimensional standards is conceded
by the industry to be a necessity for the fitting survival of motion
pictures; and also in consideration of the fact that such change
will affect all branches of the industry in America as well as abroad ;
we consider it the duty of this Society to take upon its shoulders the
responsibility of standardizing development.
We propose that a special standing committee, which would
include representative members of all branches of the motion picture
industry, as well as members of all recognized technical and business
associations within the industry, be immediately formed, and be
given power and authority to discuss and make definite decisions
in regard to the creation and adoption of a new standard.
Jan., 1930] WlDK FlLM STANDARDS 83
Further, the Bell & Howell Company is prepared to present to
such a committee, and in a comparatively short period, a finished film
of any standard which may be agreed upon, so that a visual presenta-
tion to, and further discussion with, producers and exhibitors may
be possible.
It would be pertinent for this committee to devise the means by
which the financial burden of the investigation could be equitably
distributed within the motion picture industry as a whole. We
feel sure that such a committee would be in position to secure all
the necessary moral and material cooperation that would be needed
because of the far reaching importance of this subject, upon which
depends the stability and longevity of the motion picture industry
throughout the world.
DISCUSSION
MR. HEISLER: (Communicated.) There seems to be no objection to placing
a sound record track outside of the sprocket holes, when considering only the mak-
ing of sound records and pictures. It may be well, however, to consider this pro-
posed location of the sound record track with respect to reproducing sound.
When a film passes through a combined picture projecting and sound repro-
ducing machine, each sprocket hole comes into active engagement with sprocket
teeth perhaps no fewer than four times. This may be repeated in theater ser-
vice several times daily. Consequently, the relatively soft and very thin film
edges in the sprocket holes soon suffer mutilation and wear, and many times are
torn, particularly when the picture aperture gate pressure is not properly adjusted.
The thin perforation contact edges frequently are burred or lifted several mils
above the plane surface of the film. Old films often have several holes torn out in
the sprocket hole path. Frequently the narrow film border outside of the holes is
notched, cut, or torn away.
The periphery spacing between the teeth on sprocket rollers is usually milled
below the film contact circumference, but often not. Sometimes this surface is
too high, consequently it can never be used as a film supporting surface. Because
of this, the only support for the sound record track on the proposed wide film
standard is the very narrow film surface at its extreme outer edge and that dis-
posed directly inside of the sprocket holes and outside of the picture frames. The
consequence is an objectionably excessive unsupported overhang for the sound
track when an imperfect outer edge does not provide a proper support.
Since films often crack from sprocket holes outward, the sound track of the pro-
posed arrangement would not only be mutilated but would also be improperly
supported.
To correctly reproduce sound, it is absolutely essential not only to provide
perfectly uniform motion of the film lengthwise, but we must also prevent the
slightest film movement in a direction perpendicular to its surface as well as a
weaving movement edgewise. The latter should be held within two mils and
there should be no perpendicular movement exceeding one-half mil, preferably
much less.
84 A. S. HOWELL AND J. A. DUBRAY
Even with the present 35 mm. film having the sound track disposed inside the
sprocket holes, and relatively well protected and supported, much difficulty is
experienced in obtaining the necessary degree of refinement in the motion of the
film through a microscopic light beam. Careful consideration should therefore
be given any proposed change of sound track location which will not provide
equally ample or better means for proper support and safeguard against the
slightest mutilation and irregularity of motion. This is now possible on correctly
designed sound reproducing machines when locating the sound track inside the
sprocket holes. If, however, the track were located outside of the sprocket holes,
it would be impossible for reasons given. We would therefore be taking a step
backward in the development of such machines.
Because of the foregoing, perhaps it would be well to hesitate in changing the
location of the sound path from the inside to the outside of the sprocket holes.
There seems to be no possibility of trouble coming from a slightly wider spacing
of the sprocket hole path.
MR. DUBRAY: (Communicated.) Mr. Heisler is apparently justified in ob-
jecting to the arrangement of the sound record outside of the perforations.
We wish, however, to remark that Mr. Heisler's contentions are mainly based
upon the performance of existing apparatus, while the adoption of a new standard
in film dimensions would necessarily call for a complete redesigning of the pro-
jection machine. This would give the mechanical engineers the opportunity
of devising adequate means for the proper support and registration of the sound
record.
We wish also to state that we do not quite agree with Mr. Heisler's statement
that with the sound track inside the perforation, as in the present practice, all
the objectionable points are entirely eliminated. The mutilation of the perfora-
tion due to excessive pressure on the sprocket tooth is nearly always equal in
both directions and tends to mar the sound record, regardless of which side of
the perforation it happens to be on.
It seems that in order to provide a reasonable degree of protection for the
sound record on the film, it would be necessary to provide a much greater space
from the side adjacent to the perforation than is now the practice. This applies
equally whether or not the sound record is placed outside or inside the perforation.
We have considered this greater protection of the sound record when proposing
a much greater width for the light-shield between sound track and perforation
and a much greater width between perforation and edge of film than in today's
dimensional standards.
ACOUSTIC CONTROL OF RECORDING FOR TALKING
MOTION PICTURES
J. P. MAXFIELD *
The purpose of this paper is to describe the fundamental basis
of sound recording as applied to motion pictures and to give certain
results which have been obtained by the use of these principles
in the actual production of pictures for release. The quantitative
methods of applying the material have not been completely worked
out and the work described is therefore largely of a qualitative
nature. Some indication has been obtained, however, regarding
the approximate magnitude of the more important factors.
The problem to be solved is that of obtaining a sound record
which correlates with the picture in such a manner that a member of
the audience is given the illusion of being an actual spectator in
the scene. This problem readily divides itself into three parts:
First, a determination of the factors which are of importance to
an actual observer in a scene in the appreciation of depth of sound
and direction of sight. Second, a determination of which of these
factors are usable under the conditions of photography and acoustic
pickup for a talking picture. Third, the control of the acoustics
in the set and the position of the pickup device in order to best
make use of the available factors.
When a person is viewing a real scene in real life, he is viewing
it with lenses that is, the eyes, and pickup devices that is, the
ears, which are in a fixed relationship, one to the other. This
observer is equipped with two eyes and two ears. The two eyes
enable him to appreciate distance or depth with much more facility
than would be possible with one eye, while the two ears enable
him to appreciate direction and perhaps, to a slight extent, depth
where sound is concerned. The point of importance, however,
is the fact that the eyes and ears maintain a fixed relationship to
one another.
* Electrical Research Products, Inc., New York City.
85
86 J. P. MAXFIELD [j. s. M. p. E.
The method by which we determine direction with either one or
two eyes is obvious and need not be discussed. The factors which
enter into our appreciation of depth or perspective in sound are
the ones of interest to this paper. It is probable that the most
important factor, particularly where monaural hearing is concerned,
is that which deals with the relative change in loudness of the di-
rect and reflected sound. Since the intensity of the reflected sound
varies relatively little from place to place in a room, while the direct
sound from the source to the pickup device varies quite rapidly
with its distance, the ratio of the intensity of the direct to the re-
flected sound also varies considerably. Hence, as a source of sound
such as a person speaking recedes from the microphone, the loudness
of the voice appears to decrease slightly while the reverberation
appears to increase materially. With binaural listening, this is
unconsciously interpreted as distance. It has been found that this
effect, when properly controlled, can also be interpreted as distance
with monaural listening.
In the case of a talking motion picture, the camera has only
one lens and the recording system only one ear, so that those effects
which were brought about by the binocular seeing and binaural
hearing cannot be made use of. Long experience with the photog-
raphy has enabled the cameramen to create a part of the depth
illusion by the proper choice of the focal length of the lens used
and by the proper type of lighting. Fortunately, for the acoustic
engineer, the impression of depth depends upon factors which are
almost as effective with monaural as with binaural listening ; namely,
the change in the ratio of the intensity of the direct sound to the
reverberation present.
The loss of direction brought about by the use of one ear only,
causes some rather unexpected results. When two ears are used,
a person has the ability to consciously pay attention to sounds
coming from a given direction to the partial exclusion of sounds
coming from other directions. With the loss of the sense of di-
rection which accompanies the use of monaural hearing, this con-
scious discrimination becomes impossible and the incidental noises
occurring in a scene, as well as any reverberation which may be
present, are apparently increased to such an extent that they un-
duly intrude themselves on the hearer's notice. It is, therefore,
necessary to hold these noises, including the reverberation, down
to a lower loudness than normal if a scene recorded monaurally
Jan., 1930] ACOUSTIC CONTROL OF RECORDING 87
is to satisfactorily create the illusion of reality when listened to
binaurally.
This apparent increase in incidental noises and reverberation
may easily be heard by completely stopping up one ear and listening
with the other only. It is easier to detect this effect in a room
where the incidental noises are fairly loud and where the amount
of damping is frequently less than in the normal living room.
Before starting the discussion of the third part of the problem,
namely, the control of the acoustics in the set and the position of
the pickup device in order to best make use of the available knowl-
edge, it might be interesting to point out some of the conclusions
which were drawn from the foregoing brief analysis and which led
to the method of pickup and acoustic control to be described. One
of the most important requirements for obtaining the illusion of
reality is that the sound shall appear to come from the visible source
on the screen.
Since it is possible to create the illusion of depth or distance in
both the visual and audible parts of the talking picture, it is neces-
sary that the amount by which the voice appears to move forward
and backward in the set should correspond with the amount the
image actually moves. This amount by which the voice appears
to move forward and backward in the set depends upon the amount
of reverberation present and upon the relative distance of the micro-
phone from the foreground and background action. In general,
the more reverberation present, or the further the microphone
from the source of sound, the greater is the apparent distance of
the voice from the near foreground. It has also been found by
experience that if the conditions have been made correct to obtain
this illusion, the voice or sound also appears to follow the picture
across the screen.
Before discussing the design of the acoustics of the set itself,
it is necessary to consider the acoustics of the space in which the set
is built. Where outdoor sets are used or on "location," very little
acoustic trouble is experienced the natural conditions of the out-
doors being satisfactory for recording. In this connection it should
be remembered that most outdoor scenes are not free from reflection
as the majority of them contain buildings or other acoustically
hard objects. If, therefore, an outdoor scene is being imitated
in an indoor studio, this fact should be taken into account. In
the case of indoor sets, it has been found desirable that the studio
88 J. P. MAXFIKU) [j. s. M. p. E.
in which they are built should be dead and as nearly as possible
imitate open outdoor conditions. This insures that any sound
leaving the set will not return and create an echo.
It has also been found that the character of the reverberations
present should be that which one would expect to find were he
actually placed in the scene being shown. As mentioned pre-
viously, the amount of reverberation should be somewhat less than
that actually occurring in real life. A set which has no ceiling
and with one end open, approximately fulfills the proper acoustic
conditions provided the amount and nature of the reflections from
its walls approximate the amount and nature of the reflection which
would occur from the real walls being depicted. Were it not for
expense, it would be desirable to build the set of the same materials
which would have been used under actual conditions for a real
building. In practice, however, satisfactory materials can be found
which acoustically imitate the real ones and which are considerably
more economical to handle. The extra deadness needed for mon-
aural recording has, therefore, been obtained by the fact that the
sound which would normally be reflected from the ceiling and the
one missing wall, now receives no reflection but spreads out into
the dead studio and is absorbed there. In some cases sets with
two walls only are built, usually for photographic reasons. In
general, these sets do not have sufficient reverberation and it is
then necessary to move in a third wall even though this be behind
the lights, in order that proper acoustics may be obtained. Fig. 1
shows such a set-up.
It is therefore seen that this method of acoustic pickup really
amounts to the building of a set having proper acoustic conditions
inside of a very dead room. By this means it is possible to obtain
the desired acoustic properties without continually changing the
nature of the surfaces on the large sound stage itself. It is obvious
that from a practical standpoint this is a very important item.
Having obtained a set with the proper acoustic properties, the
next phase of the problem might well be termed "The Trail of the
Lonesome Microphone." The term "lonesome" is used advisedly,
for it has been found that the use of more than one microphone in a
set at one time tends to destroy the proper depth illusion and as a
result the voices very frequently fail to follow the artist about the
scene. The use of only one microphone for each camera condition
cannot be too strongly stressed. In several cases where difficulty
Jan., 1930]
ACOUSTIC CONTROL OF RECORDING
89
has been experienced with one microphone and a multiplicity was
therefore resorted to, the final sound track picked and used was
the one made with the single instrument. This has happened so
often that it would appear as a reasonable conclusion that for the
same over-all artistic result, it is easier and simpler to obtain high
quality with one microphone than with a multiplicity of them.
While it is true that the eyes and ears of a speaker are always
maintained in a fixed relationship, one to another, it is not possible
to obtain the correct effect for talking pictures with a constant
relationship between the position of the camera and the microphone.
If all pictures were taken with lenses of the same focal length, such a
-FLAT* FOR
THIRD WALL
FIG. 1. Location of an acoustic wall in a set.
relationship would exist, but in actual practice lenses of various
focal lengths are used and each of these requires a microphone
position to correspond. For instance, in Fig. 2, it will be noted
that the microphone's position for the long shot camera is quite
different from the positions used for the three close-up cameras
occurring in the same set.
An interesting experiment was tried in this connection, namely,
piecing up the long shot sound track with a close-up in position
No. 2, Fig. 2. While it was not difficult to understand every word
that was said, the illusion produced was that of the voices coming
through the open window directly behind the speakers instead of
90
J. P. MAXFIELD
[J. S. M. p. E.
coming from their lips as should have been the case. This effect
is somewhat weird and is certainly quite displeasing if it occurs
very often or for any length of dialog. It is, therefore, necessary
to use separate sound tracks for long shots and close-ups particularly
where the close-up is of action occurring in the back of the set. This
CAMERA BOOTH POSITION
FOR LONG SHOT
POSITION NO. 2
T
ICROPHONE
L
POSITION
NO I
MICROPHONE
POSITION
NO. 3
MICROPHONE
' POS
| MO. I
I
POS.
NO 3
POSITIONS OF CAMERA BOOTH
FOR CLOSEUPS
FlG. 2.
Microphone and camera
placement.
is no more than is to be expected as a close-up is merely the photog-
rapher's method of bringing distant action into the near foreground
and it is obviously necessary that the voices corresponding to this
action should be brought into the near foreground also. While a
photographer may obtain his close-up either by moving the camera
Jan., 1930] ACOUSTIC CONTROL OF RECORDING 91
closer to the subject or by changing the focal length of the lens,
this double method is not open to the acoustic engineer who can
change his perspective only by moving the microphone. Were he
able to decrease the amount of reverberation in the set, he could,
of course, get a close-up sound track without moving the micro-
phone into as close a position as would otherwise be necessary. This
latter method is, however, impracticable.
Inasmuch as we are now recognizing the difference in the sound
of a voice in the foreground and of one in the background, it becomes
necessary that the microphone be placed in the same general di-
rection from the scene as is the camera so that when an actor recedes
from or approaches the camera, he also recedes from or approaches
the microphone. Under these conditions it is possible to take a
dialog with the actors facing directly at, across or even directly
away from the microphone, since the change in quality which ac-
companies the changes in direction is only that which would be
expected as the person turns in the picture. In this connection,
it might be well to mention that with many of the dead sets which
have been used, this statement does not apply, as these sets in
general tended to reduce the intensity of the high frequencies and
this reduction often became so great when a speaker talked away
from the microphone that the intelligibility of the record was con-
siderably impaired. However, with a set having considerable
reverberation, the high frequencies which fail to reach the micro-
phone directly, do reach it after reflection from the walls and there-
fore leave the intelligibility relatively unimpaired. This failure
to get these higher frequencies of speech directly, but by reflection
only, is probably one of the factors which bring about the change in
quality in a voice when a person turns away and talks with his
back toward the listener.
It might be well at this time to summarize briefly the proper
type of arrangement of set, microphone, and camera. Fig. 2 shows
two diagrams of the same set, one arranged for a long shot of a
rather extended scene and the other arranged for the taking of three
close-ups to be inserted at the proper places in the long shot. This
figure is a diagrammatic representation of a scene actually taken.
It will be noted that for the long shot, there is only one microphone
and that for the close-up conditions, there is only one microphone
for each close-up. In some studios these three close-ups would
have been photographed separately, in which case there would
92 J. P. MAXFIELD [j. s. M. p. E.
have been only one microphone in the set at a time. However,
for continuity of action, the director in this case preferred to photo-
graph these three close-ups by repeating the long shot action com-
pletely, and it was therefore necessary to set up the three micro-
phones and the three cameras on the set. The use of this method
of pickup with its attendant improvement of quality is causing the
producers gradually to use fewer cameras on the set at any one time
and to bring the talking picture practice more nearly into line with
the practice formerly used on silent pictures. Discussions with the
cameramen regarding the desirability of taking close-ups and long
shots simultaneously indicate that the cameramen prefer to take them
separately as it makes the problems of photography, and particularly
lighting, much simpler.
For simplicity of discussion, we will confine ourselves to the use
of a single camera and a single microphone. It is seen from the
diagrams, Fig. 2, that the camera and microphone are situated in
the same general direction from the action and that the relative
distance of the microphone and camera from the scene depends
upon the focal length of the lens being used. We have found no
occasion in the six pictures which have been made by this method,
to deviate from this type of set-up.
When the set is arranged in this manner, some very useful and
interesting results are obtained. In the first place, very complete
freedom of action is permitted to the actors as it is not necessary
for the people speaking to know where the microphone is placed
and they are therefore enabled to carry on their action in a natural
manner. This has done a great deal toward helping the director
and actor improve the quality of action.
It has also been found that with such an arrangement a much
wider range of loudness can be recorded without loss of intelligi-
bility and in a very few cases has it been necessary to operate the
mixer dials during a take. This freedom from operation of the mixer
dials cannot be too strongly emphasized as such operation during a
take may completely change the emotional effect which the director
is trying to obtain with the dialog. If, therefore, an arrangement
can be found such that the dialog is recorded without any mixer
manipulation, the audience is much more likely to be presented
with the emotional result which the director intended the scene to
portray.
With this arrangement in a set, the incidental noises occurring
Jan., 1930]
ACOUSTIC CONTROL OF RECORDING
93
have been found to be much more natural and very little faking is
necessary. In fact, the experience to date with this new method
has indicated that where these noises have been faked, they have
been less convincing than when they were taken naturally.
There is one other important matter in connection with sound
wording for talking pictures and that is the addition of a musical
>re to a silent picture or the recording of a large orchestra or
:horus. In the industry this is generally called scoring. The
acoustic conditions governing this type of recording differ somewhat
from those under which dialog scenes are usually produced.
A considerable amount of work has been done regarding the
looooo
VOLUME Or ROOM IN CUBIC FEET
FIG. 3. Optimum time of reverberation as a function of room size.
optimum time of reverberation which an auditorium should have
for best conditions of music and speech. All of this work has as-
sumed a real audience and therefore binaural listening. Curve A,
Fig. 3, shows a plot of time of reverberation as a function of the
size of the auditorium in cubic feet. The shaded area marked Curve
B, Fig. 3, shows the region in which the optimum time of reverbera-
tion of the room should lie for monaural listening or recording.
It is probable that when sufficient data have been obtained a single
line may be plotted which represents the best condition as is the
case with Curve A. Present experience indicates that a line about
midway between the upper and lower edges of the area marked
94 J. P. MAXFIELD [j. s. M. P. E.
Curve B gives the best results, but there is still too much difference
of opinion to warrant too definite a statement. This time of re-
verberation given by Curve B is that which the room should have
with the musicians in it. For convenience, it is useful to build
the room to have this time of reverberation when the largest number
of people ever used in it are present. If the music being recorded
requires less people than this number, the additional damping
material must be brought in to compensate.
It has been pointed out in the literature 1 that the best place for
the production of music is a place where there is considerable re-
verberation, while the best position for listening is one in which
there is relatively little reverberation. In rooms large enough
to be used for good scoring, namely, 50,000 cubic feet or larger,
these two sets of conditions can be realized by placing the larger
part of the damping material on the end not occupied by the mu-
sicians. The microphone is then placed in this end containing
the maximum amount of damping material.
The arrangement of musicians used is that which would be used
were their end of the scoring room a real stage and were the micro-
phone end occupied by an audience. It is not necessary, therefore,
that the musical director make any special arrangement for the
purpose of recording. In scoring as in the taking of talking pictures,
the best results have been obtained with the use of one microphone
placed at a considerable distance from the orchestra, that is, 20
to 50 feet. This statement applies and has experimental verifica-
tions up to musical aggregations having as many as 95 people.
In case of an orchestra up to thirty pieces, it has not been found
necessary to operate the mixer dials during the recording as has
been the practice in the highly damped scoring rooms.
There is one very interesting effect which has been noticed, both
in scoring and in some of the earlier work on phonograph recording,
where rooms with considerable reverberation were used for re-
cording of orchestral selections. It would be found that records
made in these live rooms appeared to be very much louder than
similar records made in heavily damped rooms. Where dead rooms
were used, it seemed impossible to obtain adequate loudness without
cutting over from one groove to another, in the case of a record,
or overloading the film recording system, in case of film. On the
1 F. R. Watson, "Acoustics of Buildings."
Jan., 1930]
ACOUSTIC CONTROL OF RECORDING
95
other hand, no difficulty has been experienced in obtaining the req-
uisite loudness under the same conditions of overload in live rooms.
This would lead one to believe that the ear interprets loudness,
not only by means of maximum intensity which reaches it, but
that it also, to a certain extent, integrates this intensity in time.
Regardless of the exact nature of this phenomenon, it is of con-
siderable commercial importance as not only the quality but the
loudness of such records is improved by the use of scoring rooms
having the proper time of reverberation.
From the foregoing, it is believed that a considerable improve-
ment in the naturalness of talking moving picture reproduction can
be obtained by a proper control of the following items:
1 . Reverberation in the set.
2. Proper placement of the microphone.
3. The use of only one microphone at a time.
4. Refraining from operating the "mixer" to any extent during
take.
SOME NEW ASPECTS OF REVERBERATION
EDWARD W. KELLOGG*
OPTIMUM REVERBERATION
A year ago Dr. Paul E- Sabine presented a paper before this
Society on "The Acoustics of Sound Recording Rooms." I must
refer you to Dr. Sabine 's paper for a fuller discussion of the funda-
mental principles of auditorium acoustics, but wish to review one
aspect of the problem. The most common fault of auditoriums is
excessive reverberation. This can be cured by the introduction
LOG OF VOLUME
i i i i i i i i
J6 3.6 4O 42 44 46 4.6 SO 52 54 S.6 5.6 6.O
FIG. 1. Reverberation times of acoustically good rooms of different volumes.
of sound absorbing materials. On the other hand it has been possible
to carry this process too far and obtain a room with too little re-
verberation. Fig. 1 of Dr. Sabine's paper, which I am reproducing
for your convenience, shows what is considered a desirable degree
of reverberation for auditoriums of various sizes. The reverbera-
tion period for a given room is the time required for the sound
energy in the room to die down to a millionth part of its initial
value, or value at the time the source is stopped. You will note
from Fig. 1 that the desirable reverberation time increases with the
* Research Laboratory, General Electric Co., Schenectady, N. Y.
96
NEW ASPECTS OF REVERBERATION
97
size of the room from about 1.2 seconds for a room of about 70,000
cubic feet to nearly 2 seconds for a room of 1,000,000 cubic feet.
It is generally agreed that the most favorable conditions for music
call for a somewhat greater reverberation period than is best for
speech. This is best brought out by Prof. F. R. Watson in his
book, "Acoustics of Buildings," from which my Fig. 2 is taken.
Music produced in rooms with too little reverberation has usually
been criticized as "dull." I know of no theories about why we like
what we like in music. Why the musical effects resulting from re-
CUBE ROOT Of VOLUME
-to
/O 2O 30 40 50 60 70 SO SO /OO
VOLUME //V CUBIC FEET
/ooo /oooo
/ooooo
00000
FIG. 2. Preferred reverberation time for music and speech
(F. R. Watson).
verberation should give greater pleasure to listeners than the same
music produced, for example, out of doors, may be left to psychologists
rather than to engineers to explain. Certain of the effects of re-
verberation, however, can be understood even by an engineer.
SOME OF THE EFFECTS OF REVERBERATION
First and probably most important is the increase in total sound
volume. Power of expression in music calls for reaching high levels
of loudness. In fact, it is probably more for the sake of loudness
obtainable than for any other reason that orchestras are made up
98 .EDWARD W. KELLOGG [j. s. M. P. E.
having as many as two hundred artists. Not only is the loudness
increased through room reverberation, but the distribution through-
out the room is equalized. Twenty feet from the source, the loud-
ness is probably not greatly increased, but one hundred feet from the
source, the loudness may be increased ten or twenty fold as compared
with that of a similar source at the same distance out of doors.
Thus the reverberation makes it possible to play satisfactorily for a
larger audience.
The second effect of reverberation is a mixing of the various
elements so that too sharp a discrimination in the direction from
which the bass and treble parts come is avoided. Both the loudness
and blending factors are even more important to the artists than to
the audience. To produce adequately loud sound when desired is
part of the pleasure of playing or singing. The satisfaction which
comes from the power to produce plenty of sound is not confined to
trained musicians, but is exhibited early in life by most of us. The
blending of parts, which is helped by reflections from walls, gives the
individual musicians a better appreciation of the effect produced
by the entire orchestra, since his own instrument does not so com-
pletely drown out those fifteen or twenty feet away as would be the
case out of doors. A soloist as a result of room reverberation and
echoes probably experiences less sense of loneliness, and subcon-
sciously feels the support and encouragement of other voices.
The third effect of room reverberation is the overlapping of sounds.
It is hard to imagine that this is anything but detrimental, since it
inevitably produces many discords. The effect is similar to that of
pressing the loud pedal of a piano,* except that the foot may readily
be removed from the pedal but reverberation cannot be stopped at
will. We tolerate many discordant sounds in music provided their
magnitude is not too great. But it is probably toleration rather
than actual pleasure in such elements. The choice of reverberation
time which gives the most pleasing over-all effect is evidently a com-
promise between the first two desirable factors and the undesirable
factor of excessive overlapping.
When it comes to speech the preferred reverberation is entirely a
question of compromise between a desirable reinforcement of volume
* The similarity applies only to the factor of overlapping. The loud pedal
causes a change in tone quality by freeing all the strings so that those correspond-
ing to harmonic overtones of the note struck are set into sympathetic vibration,
while all of the strings are in some measure shock-excited.
Jan., 1930]
NEW ASPECTS OF REVERBERATION
99
FIG. 3. Help and hindrance from echoes.
100 EDWARD W. KELLOGG [j. s. M. p. E.
and detrimental overlapping. The auditors near the speaker could
hear better without any reverberation, but in the remote parts of the
room the voice is too faint without the assistance of echoes. If the
sound from an echo follows the original sound very quickly it is
helpful, whereas if it is delayed it produces only confusion. The
effect of an echo on speech perception might be represented by a
curve such as Fig. 3A. The curve would obviously be different
if the initial loudness were changed. Thus if the initial sounds were
loud enough, there would be no help from echoes. Since, however,
the purpose of the curves of Fig. 3 is simply to help us form a mental
picture of how increasing the reverberation period shifts the balance
from no help where there is zero echo, through a condition of sub-
stantial help, to one of serious detriment, it is only necessary that
curve A be a reasonable approximation to the over-all gain or loss
from an echo in the rear part of an auditorium where an average
voice would fail to carry without reinforcement. Since reverbera-
tion consists in a series of echoes of gradually decreasing amplitude,
the first and strongest of these will help and the later weaker echoes
(resulting from repeated reflections) will hinder. Let Fig. 3B repre-
sent the reverberation curve showing the manner in which the
sound dies out in a room with considerable damping. The net help
or hindrance to the auditor would be represented by Fig. 3C, whose
ordinates are the product of those of A and B. The area above the
zero line exceeds that below, which means that the echoes have been
more help than hindrance. On the other hand, with the same
initial loudness and a longer period of reverberation as illustrated
in Fig. 3D, the product curve, E, has a larger area below the zero
line, or there is more hindrance than help. There is an intermediate
value of reverberation time at which the maximum help is obtained.
This optimum reverberation is, as has been pointed out, shorter for
speech than for music, and well-designed auditoriums have usually
aimed at a compromise between the best values for each.
ALTERED REQUIREMENTS RESULTING FROM ELECTRICAL SOUND
EQUIPMENT
I have so far simply attempted to review the fundamental princi-
ples of auditorium acoustics in so far as they can be expressed in
terms of reverberation, and to suggest some of the reasons for the
acceptable reverberation being what it is. During the past ten
years much information has been accumulated, many new and
better materials have become available for acoustic treatment, and
Jan., 1930] NEW ASPECTS OF REVERBERATION 101
the principles of good acoustics have been much more widely appre-
ciated, but I believe that the general conclusions reached in the
pioneer work of Prof. Wallace Sabine have not been materially
altered. Within the past two years, however, a new factor has come
strongly into the picture, and I believe that it will call for some
radical revisions of our criteria for best acoustics. I refer to the
electrical reproduction of sound, and my thesis is that the future
auditoriums will be designed for more nearly the maximum possible
sound absorption than for an intermediate or what has been called an
"optimum value." I shall attempt to persuade you of this, using a
voice which represents a power output in sound of probably a quarter
or a half milliwatt, but the next time you go to a movie the hero
will address you in a magnificent five-watt voice, or perhaps you will
listen while he whispers a half watt into his sweetheart's ear. Does
he need any room reverberation to help make his voice audible?
If I cannot convince you of the proposition, listen to him. If room
reverberation is not wanted to produce sufficient loudness, then its
effect on clearness of speech is always detrimental. 1
The case is not so simple when it is music that is being reproduced.
The power available in present day electrical sound equipment is not
in general in excess of that of an orchestra and it is distinctly below
that of a large organ. Hence the building up of sound intensity by
room reverberation is generally as helpful today with electrical
music as it "is when an orchestra is playing, but I am speaking espe-
cially of future developments and of auditoriums in which expensive
equipment can be employed to secure the best effects. The power
from electrical sound producing devices can unquestionably be raised
to whatever levels are desired. If the best conditions for speech
call for a highly damped room, the intensity factor for music can
certainly be cared for in the amount of sound generated.
ELECTRICAL SUBSTITUTES FOR ROOM REVERBERATION
Suitable equalization of the sound in the different parts of the room
may be obtained in a number of ways without the help of reverbera-
tion. In the first place, many of the sound producing devices are
highly directive and may be made more so if desired. By directing
the sound more strongly at the remote parts of the room a satis-
1 The conclusions of K. S. Wolf as reported to this Society at the Toronto
meeting in his paper, "Theater Acoustics" and in the discussion following that
paper are not at variance with the above statement.
102 EDWARD W. KEU.OGG [J. S. M. p. E.
factory degree of equalization can be had. If it is desired to avoid
the effect on the hearer of the sound emanating all from a small
source, sound producing devices can be distributed at various points
around the room and used during the reproduction of music. The
mixing or blending of the various instruments in an orchestra has
been completed before the recording of the sound, and the auditorium
where the sound is reproduced is not depended upon to accomplish
this mixing through reverberation. It is thus possible to take care
of the loudness, the distribution, and the blending factors without
the help of room reverberation. There remains the overlapping
or echo effect as such. This is usually supplied by the characteristics
of the room in which the sound is recorded and is subject to a wide
range of control by the placing of microphones, the selection of a
suitable recording room, and other elements of recording technic.
So far as we can see, then, there is practically nothing which audi-
torium reverberation accomplishes which cannot be secured in a
highly damped auditorium by other means, and the other means
which I have suggested are susceptible to a high degree of control,
which is not possible when reverberation is depended upon to accom-
plish these results. The reverberation characteristics of the room are
constant except for changes in the size of the audience, and the
audience factor is a bothersome variable in lively auditoriums, but
much less so in highly damped rooms.
VOICE AMPLIFYING SYSTEMS
The foregoing applies only to sound which is recorded and subse-
quently reproduced, to the voices of the characters we are watching
on the screen, but in spite of whatever optimism we may possess in
regard to the future of the talking movie we may be fairly sure that
for a good while to come, three-dimensional persons with first-hand
voices will continue to address audiences, live artists will sing and
play for the public, and people will occasionally go to hear an or-
chestra. Will the highly damped auditorium meet the requirements
for such performances? The case is not so simple and clear as is
that of recorded speech and music, and improvements and refine-
ments in equipment may be necessary before the advantages of the
damped auditorium are realized in full, but I believe that the ad-
vantage will lie with the auditorium having maximum damping or a
very short reverberation period. I shall only attempt to suggest
some of the possibilities of the electrical substitutes for reverberation.
Jan., 1930] NEW ASPECTS OF REVERBERATION 103
We are all of us more or less familiar with what has been called
the "public address system" for enabling a single voice to reach
large audiences. It has certainly made possible the understanding
of speech in places where this would not otherwise be possible. It
consists essentially of a microphone, amplifiers, and loud speaker
by which the original voice is magnified. A serious limitation, how-
ever, is imposed by the fact that the microphone fails to discriminate
between the voice of the person talking and that of the loud speakers.
The latter must therefore be held down to a moderate magnification
and the microphone placed close to the person who is addressing the
audience. A very useful gain in loudness is possible in spite of these
handicaps and I believe that those who have worked with public
address systems will bear me out in saying that the difficulties from
feedback are much less in a well damped room than in a room having
strong reverberation. That a public address system is capable of
magnifying the voice of a speaker so that he will be more easily
understood, has been abundantly demonstrated, but many will
probably doubt its applicability where the utmost of voice quality
is to be preserved and aesthetic considerations control. I can fancy
an artist, jealous of her reputation, exclaiming, "What, let the people
listen to that tin horn and call it my voice?" and our sympathies
would be with the artist, or the people, or both. I am not in a
position to say whether a voice amplifying system suitable for
application to music has been developed, but we would be in serious
error if we formed our estimates of the possibilities from some of the
public address systems which we know. Their shortcomings from
an aesthetic standpoint are no reflection upon the skill or judgment
of those who designed and built them. They were developed for a
very specific purpose to get the words across and cheapness and
simplicity were important considerations. The carbon microphone
usually employed can hardly approach a condenser transmitter in
quality. One of the chief factors in controlling feedback is the use
of directive loud speakers, and directivity can be much more easily
controlled with a moderate sized device if the low frequency com-
ponents of sound are not amplified. The low frequencies, say, below
300 cycles, contribute little to understanding of speech. In a system
designed for speech amplification they have therefore been sacrificed.
A system suitable for amplifying music would of course have to
retain the low frequency components, and it would be much more
expensive but by no means out of the question. The horns, or what-
104 EDWARD W. KEU.OGG [J. s. M. p. E.
ever directive device is employed, would have to be much larger than
those used in the usual public address system. It may be desirable
to impart directive properties to the sound pickup or microphone
system as well as to the loud speakers. With the retention of low
frequency components of voice and music it may develop that in-
creased attention will have to be given to the sound deadening of the
auditorium to low frequency sounds. In his paper already referred
to, Dr. Sabine mentions the difficulty of securing large absorption
of low frequency sounds, but progress is steadily being made in this
direction.
The use of a high quality reproducing system will go far toward
reducing feedback difficulties especially if the auditorium is ade-
quately damped. High quality systems must amplify all fre-
quencies within the essential acoustic range nearly equally. Systems
which are more imperfect amplify certain frequencies much more
than others. It is these resonance points where the amplification
is high that always start the "singing" or feedback. Even though
the amplification is held below the singing point, regeneration causes
an exaggeration of those frequencies for which the amplification is
already too high and distortion becomes intolerable unless the
amplification is held far below the singing point. The more nearly
uniform the amplification of the system the closer to the singing
point it is possible to work without objectionable distortion. The
objection that by employing a public address system we shall neces-
sarily lose the fine quality of voice or instrument is therefore un-
founded. Let us assume, however, that a system having perfectly
uniform amplification is not employed and distortion results. Will
the artist have a right to object? The alternative would be to go
back to the reverberant auditorium. What does this do to voice
quality? Not only does it give the overlapping and resultant
blurring which is objectionable, but it results in great inequalities in
the loudness of the various frequencies present in the voice. The
high quality amplification system does no worse. There is one
form of distortion which the auditorium in general does not produce ,.
namely, what is known as non-linear distortion or the production
of overtones not present in the original sound. An electrical system
may give rise to non-linear distortions, but here again the question
is only one of proper design and adequate power in order to eliminate
such effects.
Given a high quality amplification system, a small amount of
I
Jan., 1930] NEW ASPECTS OF REVERBERATION 105
feedback is similar in its action to reverberation, having the ten-
dency to prolong sounds, but the reverberation period corresponding
to this would be very short. If a greater degree of overlapping and
sound prolongation is found desirable, there are many expedients
possible by which it can be supplied. For example, I was told that
a certain British broadcasting station used the device of picking up
the initial sound with a microphone, reproducing it in a separate
reverberant chamber, picking it up there with a second microphone,
and then broadcasting it.
I believe that I have gone far enough to indicate that the desirable
effects of reverberation can all be simulated by a high grade electrical
system and that these effects will be subject to complete control
while some of the undesirable effects of reverberation can be elim-
inated. Prejudice against such electrical amplifying systems is in-
evitable, but if artists find that other people's voices sound' better
with electrical reinforcement than in reverberant rooms and find
that the public appreciates their own voices better, prejudice will
quickly subside.
APPLICATION OF AMPLIFYING SYSTEMS TO ORCHESTRA MUSIC
In applying electrical reinforcement to orchestra music a favor-
able circumstance is that microphones can be located close to the
individual players, the mixing being done in the electrical circuit.
As I have said, feedback troubles are reduced whenever we can
place the microphones close to the original source. In view of this
favorable condition it should be possible to direct a certain amount
of the reproduced sound toward the orchestra itself, in order that
the musicians may get the desired sense of reinforcement and blend-
ing.
NEW MUSICAL EFFECTS
While it is not a part of the reverberation problem, I should like
to mention another application of the electrical reinforcing system,
which I believe may become an important factor. It contemplates
the same equipment which I have already described, with possibly
certain additional pickup arrangements. In the January, 1929,
issue of Radio Engineering is an article on "New Musical Effects
by Electrical Means." 1 The article was inspired by some of my
experiences with one of the first high powered loud speakers. Some
of the selections most enjoyed by myself and others were vocal and
1 Reprinted September, 1929, by Projection Engineering.
106 EDWARD W. KELLOGG [J. S. M. P. B.
violin solos. While we are accustomed to thinking of the purpose
of electrical sound equipment as that of faithfully imitating sounds
which have been produced by voices or musical instruments, there is
no reason why its function should be so limited. A voice multiplied
to one hundred times the original power is not exactly a faithful
imitation but it may be very pleasing, and I take it that the primary
function of all music production is to give pleasure or satisfaction
to listeners. A single voice or a violin is a faint source of sound for
a large auditorium. The only means hitherto possible for producing
sound in large volume has been to multiply the number of singers or
violins, so that choruses of two hundred voices and one-hundred-
piece orchestras have been employed where the finest possible in
musical entertainment has been sought, but in the effort to bring
up volume we have made great changes in tone quality. Multiplica-
tion of sources gives a sound wave of great complexity as compared
with the wave from one source. Why not have both types of sound
available at all degrees of volume? We have heretofore had our
choice between a single voice, always faint, and a chorus either faint
or loud. Let us add the fourth possibility, making the list include
a single voice either faint or with abundant volume as well as the
faint or loud chorus. This added element is made possible by
electrical equipment and it is a distinctly new musical effect. It
has been well established 1 that a change in volume results in an
alteration of sound quality. We shall still have our large choruses
and orchestras, but is anyone prepared to say that a quartette of
fine well trained voices reproduced with the volume of the large
chorus will not afford still greater pleasure to many listeners, or that
a violin solo at band volume may not be a delightful form of music?
The electrical system may go even further and give us what are
essentially new musical instruments. A magnetic pickup attached
to a violin bridge, for example, would probably give us a violin with
a different but pleasing voice quality while preserving all the power
of expression which the violin now possesses. Musical instruments
have been developed, first, to produce vibrations and, secondly, to
1 "Auditory Masking of One Pure Tone by Another," R. L. Wegel and C.
E. Lane, Phys. Rev., Vol. 23, 1924, p. 266.
"Physical Measurements of Audition," H. F. Fletcher, Bell System Tech.
Jour., Oct., 1923, p. 145. Jour. Franklin Inst., vSept., 1923.
"High Quality Transmission and Reproduction of Speech and Music," W.
H. Martin and H. Fletcher, A. I.E. E., Vol. XUII, 1924, p. 385.
Jan., 1930] NEW ASPECTS OF REVERBERATION 107
radiate the sound. The radiation of sound is by no means a simple
problem especially when it is required that the radiation cover
a large range of frequencies. This problem of radiation has
probably been more nearly solved in the case of electrical loud
speakers than in any musical instrument. Let us imagine that the
designer of a musical instrument is relieved of all necessity for worry-
ing about sound radiation and needs consider only the production
and control of vibrations of various types. May we not look as a
result of this for many new musical effects by which the musical
entertainment of the future may be enriched?
DISCUSSION
MR. SILENT: In the case of the orchestra, it would seem to be going too far to
recommend a dead theater. Many of the larger auditoriums reinforce both the
orchestra and the stage voices. However, in producing an orchestra in a dead
theater, we are taking instruments which by virtue of their purpose are designed
by men who had to play in live houses, and the sudden transport of the instru-
ments into the dead auditorium makes it necessary to compensate in their design.
Perhaps an entirely new set of musical instruments will result. In the case of
artificial reinforcements of the instruments for the purpose of simulating rever-
beration things seem precarious for the reason that one listens to reverberation
from a tremendous number of different sources. It is almost impossible to repro-
duce this effect with loud speakers.
Mr. Kellogg has offered a very valuable contribution, and while undoubtedly
his theories are very favorable for the reproduction of speech, they call for a little
modification along the lines of our experience.
CAMERA AND PROJECTOR APERTURES IN RELATION TO
SOUND-ON-FILM PICTURES
LESTER COWAN*
Recently much concern was aroused among Hollywood studio
technicians by the fact that in some theaters the heads and feet
of characters, important words in titles, and other vital elements
of the picture were being cut off in projection of sound-on-film
pictures. Projectionists were inserting in the film gate a solid
sliding aperture (Fig. 1) which masked out from the top and bottom
FIG. 1. Drawing of one attach-
ment used to simplify change from
small oblong aperture to large
aperture.
of the picture an amount sufficient to restore the normal picture
proportions. The smaller aperture reduced the height to three-
fourths of the width which had been diminished by the addition
of the sound track. The smaller rectangular picture when pro-
jected with a one-half inch shorter focal length lens filled the screen
with a picture equal in area to the silent picture.
* Assistant Secretary, Academy of Motion Picture Arts and Sciences.
108
CAMERA AND PROJECTOR APERTURES 109
1
Except in a few cases cinematographers had not been warned of
the reduced aperture practice. They did not anticipate it in their
photography. The result was that parts of the picture were being
cut out which cameramen assumed would reach the screen as usual.
Studio technicians in general were at a loss to know what to do;
they did not know the extent of the practice or the exact size of the
reduced aperture. An immediate coordination of studio practices
with existing theater methods was imperative. To this end a
nation-wide survey of theater chain and production studio practices
was launched by the Academy of Motion Picture Arts and Sciences
with the assistance of the Technical Bureau of the Association of
Motion Picture Producers. Theater chains listed in Table I and
studios listed in Table II responded to the inquiries which were sent
out.
SUMMARY OF SURVEY DATA THEATER PRACTICES
Replies from theaters reveal four different practices, alike in that
each provides for matting out the sound track by a movable masking
device, but different in their manner of compensating for the screen
area left blank because of reduced picture width due to the addition
of the sound track. For the sake of convenience let us refer to these
four practices or methods as methods A, B, C, and D.
Method A Combination of Reduced Aperture with Shorter Focal
Length Lens. An aperture is inserted in the film gate which masks
out, in addition to the sound track, a portion from the top and
bottom of the picture sufficient to reduce the height to about three-
fourths of the reduced width. The smaller 3 by 4 picture is en-
larged by a one-half inch shorter focal length lens to fill the screen.
Recentering is accomplished by auxiliary devices which enable the
lens on the machine to be moved from right to left. Unless due
allowance has been made in production for this smaller aperture
vital portions of the picture will almost certainly be cut out. The
estimated cost of installing this method is $200.
Method B Movable Mask or Flipper. A movable mask or flipper
about 30 inches wide at the left side and facing the screen changes
the screen shape to correspond with the picture shape. When sound-
on-film pictures are being shown it is moved over to cover the blank
strip on the left of the screen. The flipper is operated by a stage
110
LESTER COWAN
[J. S. M. P. E.
A
= cu
I
3to
5 E
II
i> oo
CD CD
X X
O5 00
10 co
CD CD
00 00
CD CD
X X
<N CM
00 00
CD CD
XX
CD CD
olicy
cture
r Apertur
d-on-Film
pq
|
*- en
'3 rt
.S S
o o
*!
i!
H
OT +j
< S
gs
.
Q Q ^
a -d ^
S 9 I
o o ^
pq" pq" W
Illi
re than 5%
^
oj
i
s
^
&
I
9
S I
q
I
W
o
s .S
<1 o
rt rt
pq <^5
rt rt
i
a,
cr
Jan., 1930]
CAMERA AND PROJECTOR APERTURES
111
1
i*
I U
) _3
S
|s
If
4
1
Ijll
s*
o
X
I
1 S '1
o
fs
^'| 1
1
<J
^^ r/ < H "*"*
W 3 5
1
. *'
I
p
llo
O
f
s *
O -v O^
t-H
tt
1
1
o ^ o X
3
^
j QJ
< C ;R d? *"
Q
O S
x
N
s .
rt a
* -ad
*o
S %
9
1
0)
1
+* d ^
tin
3
i*
a ^
rt 'd ^3
s .& ^ a
||gf
1 projection aperture
y is masked out the ;
rtures Vitaphone or
Movietone pi
C/3 CD
<U S
ti ^
00
^rt
ta a) '5 ^S
.S 3 OT ^
& o,
*c3
<U CO
p< ^ n
a
fl > C3 rt
rt o *2
o
& L)
o ,5 ^ 6
to 2 rt
41
&
Y T T T
W *d ^
1
^ x-
< Q
PM 3 to
H
l> ^
1111
* * a
^ S a
^ ^ 4n 4i
c/i ^ S
W
112 LESTER COWAN [j. s. M. p. E.
hand, some member of the regular house staff, or by remote control
from the booth.
Method C Blank Strip on the Left Side of Picture. A sliding plate
masks out the sound track. A blank strip shows on one side of the
screen.
Method D Small Blank Strip on Each Side of the Picture
than leave a blank strip on the left side of the picture some theaters
shift the projection machine in order to center the picture, so as to
divide the blank area between the two sides.
As conditions are constantly changing it does not seem possible at
this time to give an accurate estimate of the number of theaters
employing each of the four methods referred to above. From in-
formation received it is reasonable to assume that theaters using
methods C and D are almost exclusively the smaller houses with
less critical audiences due to lower admission prices. These theaters
proceed cautiously before adding new devices which increase their
overhead or operating expenses. The installation of a flipper costs
only about $50 but to this must be added the labor cost of operating
it. In many localities the flipper can be operated only by the em-
ployment of an extra stage hand. The alternative a new set of.
lenses and aperture plates would cost approximately $200, a very
considerable amount to the small theater owner. It is likely that
many of these small houses will continue to show their sound-on-
film pictures with a blank strip either on one side or on both sides
of the screen.
Practically all of the better class or de luxe houses fall within classes
A or B. At present the theaters in class B probably outnumber
those in class A but the tendency is definitely toward the spread of
the reduced aperture-shorter focal length lens method.
The following example illustrates the rapidly changing conditions
and the tendency. Electrical Research Products, Inc., undertook
on behalf of the Academy a complete survey of the aperture situa-
tion in all theaters west of Denver using B. R. P. I. equipment.
The current practice in 306 theaters was reported by B. R. P. I.
field representatives. A tabulation of the reports made on August
9th gave the following results:
Theaters using method A 35
Theaters using method B 123
Jan., 1930]
CAMERA AND PROJECTOR APERTURES
113
Theaters using method C
Theaters using method D
Total
136
12
306
On August 20th eleven days later a supplementary report
gave the following additional information: "Since our last report
of August 9th Fox West Coast Theaters has decided to equip all of
its theaters with the proportional masks and change of lenses."
Publix Theaters, Incorporated, are also doing this in all of their
theaters in the western part of the country, except those of the
FIG. 2. Movable lens
mount to center under-
sized aperture as developed
by Publix Theaters.
Marcus enterprises recently acquired. These new developments
would raise the number of theaters first reported as using method A
from_35 to at least 100.
Recentering. Probably the most difficult problem in connection
with the reduced aperture method (A) is to recenter the picture
after it has been enlarged. The amount masked out from the top
and bottom of the picture in reducing the aperture is calculated
to balance the increased magnification so that from the standpoint
of height the picture will fit into the screen frame. Magnification
114
LESTER COWAN
[j. s. M. P. E.
extends the left margin of the picture to cover about half of the
blank strip. The right margin is extended an equal amount beyond
the black border so that the picture must be moved to the left in
order to be properly centered. Standard equipment now in use
does not provide for this need. Movement of the picture from left
to right is not possible due to the stationary base which gives a
fixed position to the projection machine.
There are two ways in which recentering may be accomplished,
both involving the use of auxiliary devices. The first and most
ADDED HERE TO LATER MODELS
FIG. 3. Screen centering base incorporated in new models of Electrical
Research Products, Inc., reproducer set equipment.
common method of recentering is by moving the lens slightly to the
left. Publix theaters use a lever operated, horizontally movable
lens mount (Fig. 2) which moves the optical center of the lens
0.080 in. to the left. This introduces spherical aberration which
is sometimes noticeable on the screen but usually not enough to be
considered a defect. An "Ilex" lens has been developed with optical
corrections permitting sharp definition at two focal lengths, thus
simplifying the procedure by eliminating the necessity of actual lens
changing. The second method of recentering is by use of a device
which makes it possible to move the equipment on the horizontal
Jan., 1930] CAMERA AND PROJECTOR APERTURES 115
plane. A lever at the front moves the front end of the machine
laterally to preset stops.
The newest development which promises a satisfactory solution
to the problem is a shifting device (Fig. 3) developed by the Bell
Laboratories for the E. R. P. I. reproducer set for the specific pur-
pose of centering small aperture pictures on the screen.
The shifting device consists primarily of these two units: a pivot
plate for the forward pair of legs, and a plate incorporating a pedal
mechanism for the rear pair of legs. Provisions are made for an-
choring the foot pads of the reproducer set to these units, which in
turn are bolted securely to the floor. By proper adjustment of the
stop screws on the foot pedal mechanism a full sized picture is cen-
tered by depressing the right hand pedal until further motion is
halted by the adjustable stop, and the smaller picture is centered
by depressing the left hand pedal. The locking device, which con-
sists of a quick release screw clamp, maintains either position and
assures the picture remaining centered. Briefly, the device permits
the operator to quickly center either sized picture at will and main-
tain that position constantly.
Other Aspects of the Reduced Aperture Method. Attention has been
called to several other aspects of the reduced aperture practice.
1. The shorter focal length lens increases the graininess of the
picture on the screen. No theater reported this as a serious defect.
2. One theater chain called attention to the fact that the smaller
aperture slightly reduces the amount of light that gets to the screen.
Due to the fact that the size of the picture is increased, this reduced
light must cover a larger screen area. However, there has been no
indication that this constitutes a serious problem.
3. The projectionist's problem of keeping his picture in the
frame is more difficult and requires painstaking care. Although the
cameraman may keep his action within the smaller area he usually
fills up the balance of the frame with foreground and background for
the benefit of theaters using the standard aperture. This means
that the projectionist finds no indication on the picture as to the
exact line of its upper and lower limits. More is dependent upon his
own judgment than formerly and his responsibilities are greater.
SUMMARY OF SURVEY DATA STUDIO PRACTICES
Now let us turn our attention to the studios to see what, if any-
thing, they are doing to meet these changing conditions in the theater.
116 LESTER COWAN [j. s. M. P. E.
Twelve studios reported in the Academy survey. All were making
allowance in photography for the sound track either through a definite
marking on the camera ground glass or through instructions to
cameramen to center their pictures to the right so that the addition
of the sound track would not affect their composition. Two of the
twelve studios, Fox and Paramount, who had been in communica-
tion with their own theater chains, were informed of the new prac-
tices and accordingly had markings put on their camera ground
glasses delineating a smaller rectangle within which all action was
to be photographed. The pictures photographed within these new
ground glass markings did not suffer from the reduced aperture
practice.
As the ground glass markings shown in Table II indicate, when
compared with the dimensions of the reduced projection machine
aperture, most of the studios had done nothing to anticipate the
new theater methods.
TABLE II. Summary of Survey of Studio Aperture Practices
Dimensions of Ground
Studio Glass Markings
Paramount 0.623" X 0.81.2"
Fox 0.650" X 0.835"
Metro-Goldwyn-Mayer . 723 " X . 835"
Columbia 0.725" X 0.950"
United Artists . 700 " X . 920 "
Universal Bell & Howell . 720 " X . 969 "
Mitchell 0.723" X 0.835"
Sennett 0.720" X 0.865"
R-K-O Bell & Howell . 720 " X . 855 "
Mitchell 0.723" X 0.&35"
Educational 0.723" X 0.895"
Darmour 0.700" X 0.840"
Tiffany-Stahl 0.700" X 0.868"
Pathe 0.723" X 0.887*
Note: Aperture on Bell & Howell cameras is 0.720* X 0.969"; on Mitchell
cameras, 0.720" X 0.923".
It is interesting to note that twelve studios reported twelve different
dimensions marked on camera ground glasses. This is partly ex-
plained by the fact that some studios have had the sound track
width indicated by a line on the ground glass while others simply
instructed cameramen to center their compositions to the right so as
to make room for the sound track.
When the cameraman looks into his ground glass he must bear in
Jan.
1930]
CAMERA AND PROJECTOR APERTURES
117
mind that the picture which he is composing is likely to be projected
through apertures of three different sizes:
1. Movietone 0.680" X 0.820" (approximately)
2. Reduced Aperture 0.600" X 0.800" (approximately)
3. Standard Aperture for Silent and Disk Release 0.680" X 0.906'
proximately)
Restoration of Aperture to 3
x 4 Proportion on Basis of
Dimensions Recommended
by Academy of Motion
Picture Arts and Sciences.
(ap-
Circle Represents a
Head Close-up.
A-Original "B and H" Silent
Aperture .720"x9375".
B-A with Sound Track .085 ".
C-Recentering of B
Account of Sound Track.
D-C Recentered with Camera
Aperture as shown .620' x
.835".
-Head Reduced to meet projec-
tion requirements of Proj.
Aperture in F.
7 -NewProj. Aperture, size .600"
x .800", inside Camera Aper-
ture showing Head reduction.
3 and H represent -cutting of
Head in Projector by im-
propr Framing.
H
By V. K. Miller, Paramount-Famous-Lasky
'he picture must look well in all three forms. The practice of most
cameramen is to favor the reduced Movietone apertures by centering
their picture a bit to the right. A properly composed picture will
confine the action within the smaller area with a suitable back-
ground and foreground for theaters using the Movietone or standard
apertures. If any of the three forms suffer it will most likely be
118 LESTER COWAN [j. s. M. p. E.
the picture for silent or disk release. Successful examples of triple
composition have been made proving that it is possible to have the
picture look well under all conditions. In this connection a com-
ment made at a recent Academy meeting is interesting:
' 'There is a way, I think, whereby we can satisfy both the silent
picture exhibitor and the sound picture exhibitor, giving them both
an identical composition in the 3 by 4 ratio. The method is just
the reverse of what Photophone did when they first began. The
method is to take the picture in the camera on a smaller size, masking
off the rest of the film, then printing the release for the sound version
in the usual manner and printing the release for the silent version
on optical printers. Such a printer is being used back in New York.
It is made by Bell & Howell. At one time nobody knew how to do
optical printing, but with all the skill there is in the business, it
could be done."
CONCLUSION
The facts summarized above were presented at a joint meeting
of the Technicians' Branch of the Academy of Motion Picture Arts
and Sciences with the American Society of Cinematographers and
the local chapters of the Society of Motion Picture Engineers and
the American Projection Society, held in the Academy assembly
room on August 15th. After an extended discussion the meeting
decided to refer the survey data to a joint committee composed
of representatives of the four organizations. This Joint Committee
was constituted as follows: Gerald F. Rackett, John Arnold, E. W.
Anderson, Sidney Burton, Albert Feinstein, John F. Seitz, J. F.
Westerberg.
At a second joint meeting of these four societies the joint com-
mittee reported the recommendations embodied in the following
resolution, which was adopted by unanimous vote of the four societies.
WHEREAS, investigation has revealed wide variance in theater projection prac-
tices and that there is no effective standard aperture for projection of sound-on-
film talking motion pictures:
Be it resolved: That as a temporary measure this committee recommends that
all studios and cinematographers using sound-on -film methods make marks on
the camera ground glass equally spaced from the top and bottom in addition to
the mat or mark for the sound track; these marks to delineate a rectangle 0.620
by 0.835 inch in size and that all vital portions of the picture be composed within
these limits.
Be it also resolved: That the committee further recommends that theaters
which make a practice of reestablishing the full screen proportions from sound-on-
Jan., 1930] CAMERA AND PROJECTOR APERTURES 119
iilm pictures do so by the use of an aperture whose size would be 0.600 by 0.800
inch on the basis of projection on the level, the horizontal center of the aperture
coinciding with the horizontal center of the S. M. P. E. Standard Aperture.
Copies of this resolution have been sent to executives of all motion
picture studios and leading theater chains. The following Holly-
wood studios have already reported that markings would be made
on the ground glass of all cameras in accordance with the specifica-
tions contained in the resolution: Paramount-Famous-Lasky, Metro-
Goldwyn-Mayer, United Artists, Pathe, Universal, R-K-O, Tiffany-
Stahl, Mack Sennett, Darmour, and Educational. Present markings
on Fox Studio cameras approximate the recommended practice.
This assures a uniform practice in the studios that anticipates and
is in accord with existing practices in the theaters. The aperture
dimension recommended to theaters represents a mean of dimen-
sions reported by theaters now using the smaller aperture and may
serve as a guide to theaters which may choose to adopt it in the
future.
Copies of this resolution have also been sent to the Standards
Committee of the S. M. P. E.* and the Projectionists Advisory
Council in the hope that these two important bodies would interest
themselves in working out a set of permanent standards to meet the
new conditions.
ADDENDA
The following item, although not a part of this paper, I thought
might be an interesting sidelight to some members of the Society.
A supervising projectionist of one of the largest theater chains in
his reply to our inquiry raises a very pertinent question. He says:
"The matting off at the top and bottom of the picture seems essential
to members of the profession but the thought occurs to us, 'Does
the shape of the projected picture matter to the general public?' '
Our curiosity aroused, we put the question of the comparative ad-
vantages of the square and rectangular screen among others, to
Dr. Walter R. Miles of Stanford University. Dr. Miles is professor
of experimental psychology and an outstanding authority in his field.
[e was passing through Hollywood on his way east to attend inter-
itional congresses of physiology and psychology. His comments
the proportions of the screen are given below.
* Editor's note: This resolution was recommended as standard practice by the
indards Committee of the S. M. P. E. See report in this issue.
120 LESTER COWAN fj. s. M. p. E.
According to the view of Dr. Miles, the physical nature of the eye
as well as long habit is against the nearly square shape of the sound-
on-film picture for the motion picture image as compared with the
rectangular shape silent picture. He says:
"No generation of man is entirely free from former generations.
Whether this is accident or intention it is hard to determine. If we
make a survey of the tools and household articles that were used
in Egypt as compared to those that are used today we find, perhaps
to our surprise, considerable uniformity in shapes and sizes. For
example, there is an optimal size and weight for the hammer that is
used in one hand. There is an optimal size and shape for the hand
mirror to be used by a woman. Many illustrations of this come to
one's mind.
"The proportions of the rectangle have been a subject of scientific
study since about 1875. At that time it was noted that man, in
using the rectangle in nearly all of his buildings, furniture, and con-
veniences, adopted a ratio which was strikingly different from the
perfect square. Although there is no correct exactness in this ratio
it tends to be about five to eight, a combination which has been
called the golden cut, frequently found in crosses, windows, et cetera.
The formula has been: the short side is to the long side as the long
one is to the sum of the two. This must not be regarded as a law
to be striven for or which will bring punishment if it is transgressed.
"If we seek for a basis in the physiology of the eyes and in the
psychology of perception the following points come to our notice.
The eyes have one pair of muscles for moving them in the horizontal
but two pairs for moving them in the vertical. Vertical movements
are harder to make over a wide visual angle. As man has lived in
his natural environment he has usually been forced to perceive more
objects arranged in the horizontal than in the vertical. This has*:
apparently established a very deep-seated habit which operates
throughout his visual perception. Perhaps we can see the whole
thing typified in the opening through which the human eye looks ; i
it is characteristically much wider than it is high.
"If one thinks over the famous paintings with which he is familiar
or visits a gallery he finds most of the canvases with a longer hori-
zontal axis than vertical. They are thus true to nature as man
experiences nature. Movement can take place more easily on the'
horizontal and therefore this axis may well be a longer one than the
vertical.
an., 1930] CAMERA AND PROJECTOR APERTURES 121
"One final feature in the psychology of visual perception is that
he vertical axis is over-estimated. A true square looks about three
inits too high.
"We therefore see conformity with man's general experience as
,vell as with the accepted art practice in projecting a picture that is
Adder than it is tall."
Upon his return from the east Dr. Miles took pains to reassure us
that some of the leading physiologists and psychologists of the
world with whom he had discussed this very interesting subject had
n general confirmed his opinions. This is very interesting especially
n view of the fact that the proportions of some of the wide films in
use are two to one and the opinion expressed by Dr. Miles gave
sight to five as the proportion for maximum efficiency.
REPORT OF STANDARDS AND NOMENCLATURE
COMMITTEE*
Two meetings of the committee were held during the period
between the New York and Toronto meetings of the Society. The
first of these, held in May, was poorly attended, the following mem-
bers being present: Dr. Sease, Messrs. Channier, Brown, Spence
Griffin, and Jones, Chairman. At the second meeting, held Sep-
tember 26th, the attendance was somewhat better, the followng
members being present: Mr. H. N. Griffin, Dr. Sease, Messrs.
Burnap, Sponable, M. C. Batsel (representing Dr. Goldsmith),
Channier, Brown, Spence, F. L. Whiting (representing Mr. Sponable
during his absence), and Jones, Chairman.
At these meetings a large number of problems connected with
the work of standardization were discussed at considerable length.
In some cases the committee has been able to arrive at definite
proposals for standardization and recommended practice. In
other cases it has been impossible to formulate definite proposals
for presentation to the Society. In this report is given a brief
summary of the work with which the committee has been occupied
during the past six months.
At the last meeting of the Society in New York, May 6-9, 1929,
the following proposals for standardization were presented to the
Society and received the preliminary approval of the Society:
1. Taking speed, for sound recording practice.
2. Projection speed, for sound recording practice.
3. Location of scanning slit.
4. Location and width of sound track on positive.
5. Definition of "Number of teeth in contact."
6. Definition of "Safety Film."
Having stood for six months, these proposals, with the exception
of the definition of Safety Film, are now submitted for final ap-
proval. They may then be added to the list of the Society's ap-
proved standards and recommended practice.
* October, 1929.
122
REPORT OF STANDARDS COMMITTEE 123
SAFETY FILM
The definition of Safety Film, as formulated by the committee
prior to the last meeting and submitted to this Society at the New
York meeting, has been subjected to severe cirticism from various
sources. Many objections have been raised to the adoption of the
definition in the form previously submitted. The committee has
considered these objections and feels that some of them are valid
and to meet them has formulated a new definition which it feels
represents appreciable improvement. It will be recalled that the
definition as formulated specified that any material having a burning
time less than 15 seconds when tested under certain specified con-
ditions should be called Safety Film, the burning time being de-
termined by using a sample of the material of specified dimensions.
The dimensions of the proposed sample are:
Length 36 inches, 914.4 mm.
Thickness 0.005 to 0.006 inch, 0.122 to 0.152 mm.
Width 0.63 to 1.378 inches, 16 to 35 mm.
It has been brought to the attention of the committee that it is
undesirable to base the definition of Safety Film on a burning time
determined with a sample of these dimensions since motion picture
materials are, or soon will be, in use varying over a much greater
width range. For instance, film as narrow as 7 mm. has been
proposed and several wider products (up to 70 mm.) have been
made. Moreover, the thickness tolerances are not sufficiently
great to include the possible materials which it may be desirable
to use. For instance, some very thin materials, down to approxi-
mately 0.002 inch thick, have been produced, and it seems quite
possible that it might be desirable to use materials appreciably
thicker than the upper limit specified by the definition.
This point of view raises the entire question as to the fundamental
intent and purpose of formulating a definition of Safety Film. It
has been pointed out that the definition should relate to the com-
bustion rate of the product as manufactured and distributed. This
point, that the factor of importance is the rate at which a material
burns regardless of its thickness or width, seems to the committee
to be well taken and that it should be adopted in the formulation
of the definition of the term Safety Film. In order that the defini-
tion shall conform with this point of view it is necessary, therefore,
to eliminate from the specifications of the sample, with which the
burning rate is determined, statements relative to width and thickness
124 REPORT OF STANDARDS COMMITTEE [J. S. M. P. B.
and merely to state that the time of combustion for a sample of
the material in question shall be less than some specified value.
Objection was also raised to the combustion time specified in
the previous definition. Reference to the data relating to the
burning time for various samples of news print shows in one case
the burning time for a sample of standard length, namely, 36 inches,
was as low as 10 seconds. It was pointed out that it seems illogical
to formulate a definition of Safety Film which could be interpreted
to indicate that some news print papers would fall in the unsafe
category. Of this the committee feels that the point is well taken
and that the burning time should be specified as 10 seconds rather
than 15 seconds, the value mentioned in the previous definition.
This still leaves ample margin between the class of Safety Film and
that of the commercial nitrate films which have burning times of
3 and 4 seconds.
It seemed desirable also to define somewhat more clearly the
classes of materials to which this definition is intended to refer,
limiting specifically its application to motion picture materials
but at the same time making it include all types of materials that
are used or may be used for this purpose. After careful consideration
and lengthy discussion the committee therefore wishes to withdraw
the definition submitted at the last meeting and to substitute the
following:
The term "Safety Film," as applied to motion picture materials,
shall refer to materials which have a burning time greater than
ten (10) seconds and which fall in the following classes: (a) sup-
port coated with emulsion, (&) any other material on which or in
which an image can be produced, (c) the processed products of
these materials, and (d) uncoated support which is or can be used
for motion picture purposes in conjunction with the aforemen-
tioned classes of materials.
The burning time is denned as the time in seconds required for
the complete combustion of a sample of the material 30 inches
long, the determination of burning time being carried out ac-
cording to the procedure of the Underwriter's Laboratory. This
definition was designed specifically to define Safety Film in terms
of the burning rate of the commercial product of any thickness or
width used in practice. The test of burning time therefore shall
be made with a sample of the material in question having a thick-
ness and width at which the particular material is used in practice.
In making a determination of burning time the Underwriter's
Laboratory prescribes that a strip of the material shall be sits-
Jan., 1930] REPORT OF STANDARDS COMMITTEE 125
.
pended vertically by a small wire through a pinhole at one end
of the test strip. A gas test flame 3 / 4 inch long and x /4 mcn m
diameter is applied at the lower end of the suspended strip. The
relative ease of ignition, height of flame, and time required for
complete combustion are observed. Tests shall be made in a place
protected so far as possible from drafts although no definite hoods or
shields are used.
We wish to emphasize the fact that the definition is intended
to refer specifically to a commercial product and to serve as a speci-
fication of the safety of this material as used in practice. It is
realized that a given film base formula as used for making products
which differ in thickness and width might in one case give rise to a prod-
uct which may be classified as "safety" and in other cases the product
would have to be classified as unsafe. We feel that this is desirable
and that the whole object to be achieved by the formulation of the
definition is to promote safety in the utilization of motion picture
film products.
LOCATION OF SCANNING SLIT
The wording of the specification as to the position of the scanning
slit as presented in our last report seems to be a little ambiguous.
It is therefore desired to change the wording of this proposed standard
without changing the intent. It does not seem necessary to withdraw
the previous proposal, but merely to ask the Society's permission
to alter the wording for the sake of clarification and to assume that
the definition has had its six months' probationary period.
NOTCHING OF NEGATIVES
This problem has been before the Standards Committee for several
years and no solution has as yet been found. In the last report
of this committee a drawing was published showing three forms
of commercial practice and a form proposed by the Seventh Inter-
national Photographic Congress. The Congress requested that the
Society give this proposal consideration and, if possible, its approval.
It does not seem advisable to approve the recommendation of the
Congress. The notch is located directly on the splice line. This
is not satisfactory in the case of printers using a resistance control
of printing intensity on account of the time lag in change of in-
tensity when the current flow through the lamp is changed over a
wide range. The position of the light control relative to the splice
126 REPORT OF STANDARDS COMMITTEE [J. S. M. P. E.
line depends upon the type of light control used in the printing
machine. It seems evident, therefore, that before any standardized
negative notching system can be used the method of light control
in the printing machine must be standardized. There does not
seem to be any hope of producing such standardization. As a matter
of fact there is more or less time lag in any form of light change
mechanism. The position of the notch relative to the splice line is
conditioned by the magnitude of this time lag. Placing the notch
on the splice line does not seem to meet the requirements of any
of the light change systems in extensive commercial use at present.
This problem also involves the consideration of an enormous footage
of negative already in existence and notched according to various
systems. The committee feels the only thing it can do at present
is to publish the drawings showing the various notching according
to various methods of printing and to urge strongly that in the
design of new machinery no different methods of notching be intro-
duced. This will serve to prevent a multiplication of the methods
in use and it is possible that as time goes on commercial practice
will become more and more predominantly in agreement with one
present system and in this way automatically tend towards stand-
ardization.
SOUND FILM PRACTICE
The committee has prepared a drawing showing proposed di-
mensions relating to the position of the scanning line relative to the
edge and sound track area of sound-on-film positive. This is shown
in Fig. 3. This standard is in conformity with the dimensions al-
ready preliminarily adopted for the location and width of sound
track presented in our last report. The dimensions are such that
the scanning line falls symmetrically within the sound track area.
The length of scanning line, 0.084 inch, is in conformity with present
practice. We recommend this for initial adoption.
In connection with the projection of sound film it has been sug-
gested that if each reel of film is provided with a leader on which a
definite indication of the distance between a given picture and the
corresponding sound is indicated, it would materially assist the
projectionist in threading the film into the reproducing ma-
chine. The committee wishes to recommend, therefore, that manu-
facturers of this type of film provide each reel with a leader indicating
clearly the framing of picture and the respective_sound.
Jan., 1930] REPORT OF STANDARDS COMMITTEE 127
35 MM. SPROCKETS
It has been brought to the attention of the committee that the
sprockets now being made by one of the leading manufacturers of
projection equipment do not conform entirely with the standard
dimensions as adopted by this Society. This matter has been
taken up with this manufacturer and information has been sub-
mitted stating wherein sprockets manufactured by this organization
differ from the standards of this Society, and also the reason for
this deviation. The sprockets conform in every respect to the
adopted standards with the exception of the thickness at the base
of the tooth. The value specified in our standards for this di-
mension is 0.050 inch. The dimension being used in the manu-
facture of the sprockets in question is 0.060 inch, making the thick-
ness of the tooth at the base 0.010 inch greater. It is stated that in
the opinion of the mechanical experts of this organization this
represents better shop practice and enables them to produce sprock-
ets of greater precision than when using the smaller thickness value.
The only consequence of this difference in thickness of tooth base
is that the shrinkage range of film which will run satisfactorily over
the sprocket is decreased. Sprockets made according to standard
dimensions will run film under best conditions from a shrinkage
of 0.13 per cent up to 2 per cent, 6 teeth in contact. Increasing
the thickness of the tooth base to 0.060 inch will reduce the maximum
shrinkage limit to approximately 1.5 per cent. It is contended
that in practice this shrinkage limit is adequate and that a negligible
amount of film showing shrinkage greater than this value is in circu-
lation for projection. It has been stated that no complaints are
being received from the trade relative to the improper handling
of film by the mechanisms equipped with sprockets having the
thicker tooth base. It seems wise, however, before recommending
that the Society change its present standard that definite evidence
be obtained showing conclusively that the shrinkage limit of 1.5
per cent is adequate to meet all of the demands of practice.
TESTING AND APPROVING EQUIPMENT
The President of the Society has received a communication from
one of the manufacturers of sound reproducing equipment suggesting
that the Society should consider the problem of testing and placing
its stamp of approval on equipment being manufactured for the
reproduction of sound. The President has referred this corre-
128 REPORT OF STANDARDS COMMITTEE [j. s. M. P. E.
spondence to the Standards Committee with a request that it be
given consideration. A tentative proposal to establish some such
procedure as this has been sent by the manufacturer in question to
other manufacturers of equipment of this nature and it is stated
that all of the replies thus far received have been favorable to some
such scheme. The idea involved may be best presented by a quota-
tion from the communication in question.
"The condition which presents itself to the industry at the
present time is serious in many respects and confusing to the ex-
hibitor and the industry at large.
"The Society of Motion Picture Engineers have been in ex-
istence for a number of years and the writer's thought in the
matter is that various manufacturers of sound equipment should
submit their equipment to a committee appointed by the Society
of Motion Picture Engineers and give a demonstration. Such
equipment should measure up to the standard adopted by the
Society of Motion Picture Engineers and after same has been
demonstrated, satisfactorily to the Committee, it should be cer-
tified to by your organization. Of course, this may entail some
expense, but this expense should be borne by the manufacturers of
the equipment.
"We would like to have some expression from you as to the
advisability of some action of this kind. We are sure that you
would have the hearty cooperation of every distributor and pro-
ducer of motion pictures, as well as the manufacturers of sound
equipment."
The committee has discussed this matter at some length and
feels at the present time the Society is not in a position to undertake
the work suggested. Obviously it would involve a large expendi-
ture. In order to do the work well it would be necessary to have
a well equipped laboratory staffed by experts in this line. While
we do not feel that this work can be undertaken by the Society,
some of the members of the committee feel that perhaps in the future
something of a similar type might be done and would be a real
service to the industry as a whole. It is proposed, therefore, to
bequeath to the next standards committee the information now at
hand with the suggestion that it give consideration to the idea or
to some modification thereof.
LENGTH OF TITLES
It has been suggested that the Society forgiulate some approxi-
mate rules relating to the length of time during which a title should
be permitted to remain on the screen. The committee has not had
Jan., 1930] REPORT OF STANDARDS COMMITTEE 129
time, since the receipt of this request to investigate the subject
thoroughly. However, inquiry has been made and it has been
found that in the case of one laboratory the following rule is applied.
One second is allowed per word of 6 letters, or more, up to 7 words.
The minimum length of title should correspond to 2 seconds on the
screen. Assuming 90 feet per minute as projection speed, this
would require 1.5 feet per word of 6 letters, or more, up to 7 words
with a minimum length of 3 feet. For titles containing more than
7 words, the equivalent time is decreased gradually until at 25
words the length is sufficient to allow 2 /s second per word of 6 letters.
From this point on the time per word remains constant at 2 / 3 second
per additional word. Before any definite recommendation can be
made, however, the practice followed in other laboratories should
be investigated and a recommendation formulated based upon what
seems to be average good practice.
WIDE FILM
The committee has been watching with interest the developments
leading to the introduction into the industry of film wider than the
standard 35 mm. product. An attempt has been made 'to keep
closely in touch with the developments and to obtain definite quanti-
tative information as to the various proposals of the organizations
interested in the wide products. This attempt has not been en-
tirely successful since it has been impossible in some cases to obtain
precise information as to the dimensions of the film which it is pro-
posed to use. In some cases the committee has been supplied with
dimension prints showing the proposed practice. The committee
had hoped to be able to publish with this report dimensional draw-
ings of the films being promoted by the various groups, but since
these have not been obtained from all sources it does not seem
advisable to publish any of them. However in order that the
Society may have general information as to the developments
in this field, we have prepared a table in which is given approximate
information as to the various proposals. In some cases these di-
mensions have been scaled from samples of film and hence cannot
be considered as representing precisely the dimensional character-
istics. The various proposals which have come to the attention
of the committee are as follows.
Grandeur film, which has been developed by the William Fox
organization, is 70 mm. wide and employs perforations of special
dimensions as indicated in column B of the table.
130
REPORT OF STANDARDS COMMITTEE [J. S. M. P.
The Paramount-Famous-Lasky Corporation has produced a film
56 mm. wide with standard perforations, the pull-down being 4
perforations as in present practice.
RCA Photophone, Inc., it is understood, is proposing to introduce
the Spoor type using a film 63.5 mm. wide. While no definite
information has been obtained as to the dimensional details of the
final form which it is proposed to develop, the values in column D
give the dimensions taken from published reproductions of the Spoor
"Natural Vision" picture.
One other proposal which, while it does not involve the use of
wide film, but does give a wide picture in the theater should be
mentioned. This is the proposal made by Mr. Ralph G. Fear to
use the present camera and projector with an optical system at-
tachment which rotates the image through 90 and in this manner
gives a wide picture on 35 mm. film. The tentative dimensions
of negative picture area available by employment of this idea are
given in column A of the table.
. Table of Film Dimensions for Wider Pictures
B
c
D
A
Width of film
70 mm.
56 mm.
63 . 5 mm.
35 mm.
Picture width
1.840"
1.62"
2.06"
1.813"
Picture height
0.910"
0.742"
1.12"
0.800"
Perforation pitch
0.234"
0.187"
0.187"
0.187"
Pull-down no. of per-
forations
4
4
6
10
Perforation dimension
0.130" X 0.080"
Standard
Standard
Standard
Width of sound track
0.240"
0.125"
0.200"
It is interesting to note that practically all of these lead to pic-
tures in which the ratio of width to height is 2 or more. This is in
distinct contrast to the standard practice in which this ratio (width
to height) is 1.33, and in even greater contrast to the sound-on-film
positive in which this ratio decreases to approximately 1.15.
There seems to be little doubt that there is a real need for a film
wider than the present 35 mm. product. Even previous to the intro-
duction of sound it was felt by many that the picture proportion
available was not well adapted to certain types of productions,
being too narrow relative to its height. The necessity of using a
strip on the positive film for the sound record aggravated this con-
dition, giving a picture area approaching much too closely the pro-
Jan., 1930] REPORT OF STANDARDS COMMITTEE 131
portions of a square to be pleasing artistically and of practical utility
from the standpoint of motion picture technic. It seems obvious,
however, that the introduction of more than one wide film is highly
undesirable from the standpoint of the best interests of the motion
picture industry as a whole. The cost of building new equipment,
including cameras, processing machinery, projectors, etc., for any
one new width will be great. The multiplication of widths will
increase enormously the final cost to the industry of obtaining a
more satisfactory picture width. The committee urges very strongly
that these factors be considered and that every effort be made to
reach an agreement on one standard wide film.
STANDARD APERTURE FOR PROJECTION OF SOUND-ON-FILM POSITIVES
Since the introduction of the use of positives carrying sound
records, considerable confusion has resulted from the change in
shape of the available picture area and no definite standard practice
has been established. In some theaters it is practice to mask off
one end of the screen, thus giving a picture area having a width to
height ratio of approximately 1.15. In this case the regular pro-
jection lens is used. Other theaters, in an effort to retain the old
picture proportion of 1.33, have used somewhat shorter projection
lenses increasing the magnification sufficiently so as to fill the stand-
ard screen. This of course masks out a portion at the top or bottom,
or both, of the printed positive. In some cases this is a serious
objection in that it cuts out some action or seriously interferes with
the composition of the picture. On the west coast this problem has
been receiving the attention of various organizations and at a joint
meeting of the Academy of Motion Picture Arts and Sciences,
Technicians' Branch, the American Society of Cinema tographers, the
local section of the Society of Motion Picture Engineers, and the
American Projection Society, the problem was discussed and pre-
liminary resolutions drawn up and adopted. They are as follows:
"WHEREAS, Investigation has revealed wide variance in
theater projection practices and that there is no effective standard
aperture for projection of sound-on-film talking motion pictures;
"Be it resolved: That as a temporary measure this committee
recommends that all studios and cinematographers using sound-
on-film methods make marks on the camera ground glass equally
spaced from the top and bottom in addition to the mat mark for
the sound track; these marks to delineate a rectangle 0.620 by
0.835 inch in size and that all vital portions of the picture be
composed within these limits.
132 REPORT OF STANDARDS COMMITTEE [J. S. M. p. E.
"Be it also resolved: That the committee further recommends
that theaters which make a practice of reestablishing the full
screen proportions from sound-on-film pictures do so by the use
of an aperture whose size would be 0.600 by 0.800 inch on the
basis of projection on the level, the horizontal center of the aper-
ture coinciding with the horizontal center of the S. M. P. E.
standard aperture."
This committee has considered these recommendations and feels
they represent the most satisfactory solution, at least for immediate
adoption. If the lines as recommended are drawn on the ground
glass of the camera and the essential action confined to this area,
then the old 4 to 3 ratio of picture shape in the theater can be ob-
tained without danger of cutting out important elements. This,
of course, involves the use of a somewhat shorter focal length of
projection lens and an increase of about 11 per cent in magnification.
At the same time a positive without sound printed from such a
negative can be projected exactly as in presound practice. The
committee therefore concurs in recommending that this procedure
be adopted as standard. While it is not entirely free from ob-
jectionable features it seems to represent the best compromise.
Information has been received from the International Projector
Corporation that it is at the present time manufacturing two masks
for insertion in the projector when sound-on-film positive is being
used. One of these, referred to as the proportional mask, has an
aperture of 0.800 inch by 0.607 inch, and the other, for use when
it is not desired to correct the projected picture shape, has an aper-
ture 0.800 inch by 0.6795 inch. The proportional mask dimensions
coincide very closely with the Pacific Coast recommendation on
this subject, there being a discrepancy of only 0.007 inch in the
vertical dimension. The recommendation contained in the above
resolution, however, adheres strictly to the Society's recommenda-
tion that a ratio of 3 to 4 be maintained. The committee feels,
therefore, that it should approve the dimensions 0.800 inch by
0.600 inch for the proportional mask and further recommends
the acceptance of the International Projector Corporation's di-
mensions, 0.800 inch by 0.6795 inch, for use on sound-on-film positive
where correction to proportional dimensions is not desired.
SUMMARY
Recommendations Previously Approved. The following recommen-
dations have been presented previously and have received the first
jail., J.I70UJ
1 ( 1 ^ _^-rrT-n r i
( )
I.i7795" MAX. \
1
1.^77 MELAM
1
\
1
1
- 169 -
D A
1
D
\-
1
x
243
D \
d
V\
s
D
\\
*054
^>
4
sx
D
|
SN
(^
EMULSION
5IPE-UP
ss
\"
kii*-*-
1
I
.iosJ
cm
i ^jss
, . IE
r
r 004 L^
133
FIG. 1. Dimension and position of sound track on 35 mm.
sound and picture positive.
FIG. 2. Sprocket teeth in contact.
134
REPORT OF STANDARDS COMMITTEE [J. S. M. p. E.
approval of the Society. They are now presented with a recom-
mendation that you give them your second and final approval.
1. Taking speed for standard 35 mm. sound pictures shall be
24 pictures per second.
2. Projection speed for standard 35 mm. sound pictures shall
be 24 pictures per second.
3. The scanning slit (for combined sound and picture on 35 mm.
GUIPE1P ELPGE.
i
--b OF
:\
DO"-*
SOU
NP
( \
TRACK
(
ARE.A
SCANNING LIKE.
V
> '
\
_
LJ
.002
M 04Z>*'04f K
tOOi\
hrOSA" -H
C.L. OF SOUNP "^
TRACK ARELA I
ANP OF f
SCANNING LINE. J
GUIPING ELPGt
OF SOUNPGA1E.
FIG. 3. Position of scanning line for sound-on-film
positive.
film) shall be located at an average distance of 14.5 inches measured
along the film below the center of the picture gate.
4. The location and width of the sound track on combined
sound and picture positives shall be as shown in Fig. 1.
5. The number of teeth in mesh with the film (commonly re-
ferred to as "teeth in contact") shall be the number of teeth in the
arc of contact of the film with the drum of the sprocket, the pulling
face of one tooth being at the origin of the arc, as shown in Fig. 2.
Jan., 1930] REPORT OF STANDARDS CoMMlTfE^ 135
New Proposals.
6. The term "Safety Film," as applied to motion picture ma-
terials, shall refer to materials which have a burning time greater
than ten (10) seconds and which fall in the following classes: (a)
support coated with emulsion, (b) any other material on which or
in which an image can be produced, (c) the processed products of
these materials, and (d) uncoated support which is or can be used
for motion picture purposes in conjunction with the aforementioned
classes of materials.
The burning time is defined as the time in seconds required for
the complete combustion of a sample of the material 36 inches
long, the determination of burning time being carried out according
to the procedure of the Underwriter's Laboratory. This definition
was designed specifically to define Safety Film in terms of the burn-
ing rate of the commercial product of any thickness or width used
in practice. The test of burning time, therefore, shall be made with
a sample of the material in question having a thickness and width
at which the particular material is used in practice.
7. The position and dimensions of scanning line shall be as
shown in Fig. 3.
Recommended Practice.
8. It is recommended that manufacturers of sound film place a
leader on each roll of film on which is designated the framing of
the picture and the corresponding sound.
9. It is recommended that the Society approve the proposals
of the joint committee of the Academy of Motion Picture Arts
and Sciences, Technicians' Branch, the American Society of Cinema-
tographers, the local section of the Society of Motion Picture Engi-
neers, and the American Projection Society relative to practice in
the photography and projection of sound-on-film,
Respectfully submitted,
N. H. DREYER W. R. G. BAKER W. B. RAYTON
A. N. GOLDSMITH F. L. BROWN V. B. SEASE
H. GRIFFIN R. S. BURNAP J. L. SPENCE
D. MACKENZIE G. L. CHANNIER E. I. SPONABLE
T. E. SHEA E. HUSE LOYD A. JONES, Chairman
Errata
In No. 37 Transactions, Standards Report, Fig. 4, p. 38, 0.099
lould be 0.109 as shown in Fig. 1 of report dated October, 1929.
136 REPORT OF STANDARDS COMMITTEE [J. S. M. p. E.
DISCUSSION
SAFETY FILM
MR. TAYLOR: It is not clear to me whether the definition of Safety Film refers
to a specific material as manufactured i. e., safety stock, or to the film as ac-
tually used of a given width, perforation, and thickness.
MR. JONES: We propose to define Safety Film in terms of the burning rate of
an actually used commercial product and specifically do not want to attempt to
define the combustibility of some particular chemical compound.
MR. STOUTER: Would it not be more specific to state in the specification of
burning time, "according to the procedure of the Underwriter's Laboratory as I
of this date?"
MR. JONES: I think that is a good suggestion.
LOCATION OF SCANNING SLIT
MR. RICHARDSON: I believe that the committee should work on as wide a sound
track as possible, the greater the width the greater the amount of overtone..
MR. JONES: The committee has been in constant contact with the sound en-
gineers trying to obtain their reaction. It stands ready to recommend whatever
experts in the field say is the best practice.
35 MM. SPROCKETS
MR. GREENE: Mr. Jones spoke of the non-conformity of one manufacturer to
the sprocket standard. Was it the opinion of this concern that they got steadier
running over a sprocket which differed from the S. M. P. E. standard?
MR. JONES: The information was that they felt by having a somewhat thicker
metal support it allowed them to machine with somewhat greater precision;
it represented better shop practice and led to a more precise sprocket which would
tend to give a steadier picture.
MR. GREENE: Would it help the committee in deciding whether or not to rec-
ommend the approval of this sprocket, if they were to receive during the coming
year on a blank form reports from a thousand or so projectionists in all parts of
the country relative to the behavior of different grades of film on this sprocket?
Shrinkage in each case could be measured with one of the film pitch rules shown us
earlier in the convention.
MR. JONES: I doubt a little the wisdom of such a procedure because there are
too many undetermined variables. Reports from a thousand different theaters
and projectionists would make it impossible to evaluate other variables which
could not be specified. It must be done in a standardizing laboratory where con-
ditions can be controlled and everything measured under identical conditions.
I should like to ask if Mr. Griffin has anything to contribute on this matter.
MR. GRIFFIN: I have nothing to add to what was submitted. We discovered
by measuring up several hundred pieces of film procured from various sources
that the extreme shrinkage with which the 0.050 in. base tooth was concerned was
never experienced in the field. The shrinkages run far below the maximum
shrinkage limit, so that we are well within the limits in using the extra 0.010 in.
on the tooth. I might say that all the sprockets which we have turned out for
the past three or four years have been of that dimension.
Jan., 1930]
REPORT OF STANDARDS COMMITTEE
137
GENERAL DISCUSSION
MR. FARNHAM: This does not apply directly to Mr. Jones' report, but to many
of the papers and reports presented at our conventions. Frequently, in a single
illustration, some dimensions are given in English units and others in the metric
system. To visualize the size of the object illustrated necessitates considerable
mental gymnastics on the part of those not equally conversant with both sys-
tems. I believe the Society should make itself definite on this point of uni-
formity through either the Papers Committee or the Standards and Nomenclature
Committee. I would suggest all dimensional figures be given in both systems.
This is a practice followed by other engineering societies.
The question of the S. M. P. E. standards pamphlet was brought up. The
present issue is out of print. Mr. Jones was of the opinion that reprinting should
be held up pending the ratification of standards proposed in the foregoing report.
ABSTRACTS
Contribution to the Search for a New Motion Picture Frame Proportion.
A. P. RICHARD. Cinemat. jranq., 9, Nov. 26, 1927, pp. 54-5. A picture frame
having the dimensions 18 by 30 mm. is proposed for 35 mm. film. The perfora-
tions would be placed between pictures.
Difficulties of the Sound Films. Lichtbildbuhne, 21, Nov. 10, 1928, pp. 22-3.
Aside from reproduction, amplification, and acoustic problems in connection with
sound presentation, difficulties such as omissions and physical damage (ground
noise) in the film record are important. A special idler roller, patented by a
German firm, does not touch the sound record in its travel over the sprocket.
(This device is especially useful with the film made by the firm because the sound
record is between the perforations and the film edge. Abstr.) The roller is only
slightly longer than the distance between perforations and is notched to match
the sprocket teeth. It rotates like a gear in mesh with the sprocketed teeth.
Mention is made of the Tri-Ergon 42 mm. film in which the sound record is
carried near the center of the extra 7 mm. width. Condenser loud speakers are
briefly described.
This Matter of Volume Control. C. DREHER. Mot. Pict. Projectionist, 2,
February, 1929, pp. 11, 20-1. The author summarizes the principal faults of
volume in the sound motion pictures as follows: (1) General level of speech re-
production too high. (2) Failure of volume to follow the action or to maintain a
natural proportion. (3) Abrupt jumps from one musical selection to another as
scenes change. (4) Inability to adapt sound reproduction to audience reaction
in special cases.
Slits Mechanical vs. Optical. Mot. Pict. Projectionist, 2, July, 1929, pp. 16-7.
The major troubles with mechanical slits are: (1) The process of manufacturing
a fine slit in a metal plate is so difficult that the results often vary. (2) The slit
does not allow all the available light to pass. (3) The slit becomes dirty and
clogged which interferes with projection or recording. The optical slit overcomes
these difficulties.
Perspective in Photography. F. F. RENWICK. B. J., 75, Dec. 14, 1928, pp.
750-2. An analysis from the geometrical viewpoint of the true perspective in
photographs. Objects separated by considerable distances can be seen sharply
and simultaneously with one eye (as with the camera) but when two eyes are used,
only one plane of the object can be appreciated clearly at one time. Complete
examination of a scene in both depth and area is necessarily a complicated opera-
tion involving many rapid movements of the eyes with adjustments of focus of the
eye lenses. Photographs usually possess correct geometrical perspective and
depict sharply a far wider angle than is seen by the eyes focused on one point.
Artists rarely include an angle greater than 40 in pictures, but photographs often
include as much as 75. Artists add naturalness to their work by separating the
vanishing points; photographers either take the picture with a long focus lens
(which if carried too far results in a loss of solidity or soundness) or else use a short
138
ABSTRACTS 139
focus lens and enlarge the picture to produce the desired effect. It is suggested
that views seen with two eyes might be simulated by using a twin lens camera
adapted to give a fused image single and sharp only for the principal object.
Cinematographic Record of Sunrise on the Moon. R. F. ARNOTT, E. G. F.
ARNOTT, A. L. BENNETT, and J, Q. STEWART. Nature, 124, July 13, 1929, pp.
56-7. A camera taking 16 mm. film was used at the focal plane of a refractor of
30 ft. focal length, and exposures of about 3 3 /4 sees, were made at intervals of 6
sees, for about 4 hrs. The results were in some ways unsatisfactory but an in-
teresting film was secured of a region about 200 by 300 miles around Copernicus.
Theory of the Photographic Processes. H. KIESER. Z. wiss. Phot., 26,
April, 1929, pp. 321-40. The author gives hypotheses of the formation of the
photographic latent image on the basis of the photoconductivity (inner photo-
electric effect) combined with Einstein's equivalence law of photochemical proc-
esses. First he discusses the action of water in the gelatin as a bromine absorber.
Solarization is explained by L,iippo-Cramer's theory that the photolytically
formed silver at the surface of the silver halide grain is destroyed by halogen,
liberated by the photolytic decomposition within the grain, that migrated to the
surface. The solarization on plates which were first fixed and then developed is
caused by a coagulation of the silver during fixation. The Clayden and Villard
effects (reversal phenomena on lightning pictures and X-rays) are regarded as
closely connected with solarization. They differ from solarization in that the
latent image lies deeper within the grain. The regression attacks more the ripen-
ing nuclei than the photolytically formed silver. The failure of the reciprocity
law, and the intermittency effect are explained by regression. During this re-
gression not only photolytically formed silver is bromated but also the ripening
nuclei as in the case of solarization. The optical sensitizing with dyes is possible
if the excited dye molecule excites the neighboring bromine ions in the crystal
lattice. Desensitizers are substances which have electron affinity; they are not
able to excite the bromine atoms so that a regression with an already formed silver
atom by the liberated bromine atoms takes place. The Herschel effect is ex-
plained by comparison with the solarized silver halide grain, which has a greater
number of developable nuclei within the grain than on the surface of the grain.
Infra-red and red light penetrate the grain and liberate electrons, which establish
a regression within the grain. A number of free electrons migrate to the surface
of the grain and form in the layers with less nuclei new silver atoms which intro-
duce developability.
Color Camera Making Rushed to Get Set for Increased Use Next Season.
Ex. Herald World, 96, July 6, 1929, pp. 70, 131. Plans are announced by Techni-
color, Inc., to increase the number of color cameras from 12 to 50 and the capacity
of the processing laboratories from 12,000,000 to 100,000,000 feet of film per year.
Three improvements in the process are described. (1) The use of a negative film
requiring no more light for exposure than black and white film ; (2) the application
of the final color records on one side, instead of both sides of the film as previously
required; and (3) the possibility of using three basic colors instead of two as
formerly used. The color camera contains a prism which divides the image into
two parts ; one is passed through one ray filter, and the other through the next in
succession at the negative film. This negative record is "printed" by a mecha-
nism which exposes every alternate frame, so that the red corrected pictures appear
140 ABSTRACTS [j. a M. P. E.
on one continuous film and the blues on another continuous film. These prints
are developed to give a film covered with minute hills and dales, much like an en-
graving plate. The celluloid plate is hardened, dyed, and run under pressure,
along a steel plate in contact with a transparent film on which the dye image is
printed. Then the other film containing the second color record is printed on the
transparent film now bearing the first record. Fatigue tests made on audiences
have shown that color motion pictures are less tiring than black and white and
still less than reading news print for over an hour.
Story of Stereoscopic Motion Pictures. C. EARTH. Plastische Bild, No.
9/10, Sept.-Oct., 1928, pp. 98-102. A review of systems for the production of
stereoscopic motion pictures. Some of the first attempts consisted in projecting
separate images side by side of a subject taken from two points of view. Special
prism glasses were used to view the pictures, and it was necessary that the ob-
server be equidistant from the two pictures. Another method used images pro-
jected alternately on the same screen. Glasses with shutters synchronized with
the projector allowed the observer's eye to see the image from its corresponding
point of view. Other stereoscopic systems employed are: (1) Complementary
monochrome images projected on the same screen, to be observed through corre-
sponding complementary filters for each eye; (2) plane polarized light for pro-
jection and observing glasses with nicol prisms; and (3) images projected through
gratings placed near the screen and observed from a different position through
similar gratings.
Putting the Light Where You Want It. Amer. Cinemat., 10, April, 1929, p.
13. Curves for luminous flux are given for a two-lamp broadside and a high
efficiency reflector. The latter directs 45% of the light within a 60 angle, com-
pared with 15% by the broadside. Silvered glass and aluminium are compared
as reflectors, the advantage lying with the glass.
Magnesium Light for Photography and Cinematography. BRILLS. Bull.
soc.franQ. phot., 17, June, 1928, p. 156. This magnesium flare consists of a tube
containing a pile of disks or balls of magnesium making only slight contact with
each other. The space around them can contain an oxidizing substance. The
small area of contact between the pieces of magnesium decreases the rate of
propagation of the combustion down the tube and gives a light of long duration.
Incandescent Lighting Improves. R. E. FARNHAM. Amer. Cinemat., 10,
April, 1929, pp. 31-3. Four thousand eight hundred lamps, totaling 3900 kw.,
have recently been used on a Universal set. Portable lamp equipment is in favor.
The 10,000 watt lamps now contain tungsten powder for mechanically removing
blackening from the bulb. Small bare lamps are favored for natural starlight
effects.
Maximum Light for Projection with a Minimum of Heat. M. SCHOLZ.
Filmtechnik, 4, Dec. 22, 1928, pp. 512-4. The use of mirrors and condensers of
heat-absorbing glass or crown glass mirrors and condensers protected from the
heat by plates of heat-absorbing glass is advocated. Graphs are included which
show: (1) Temperature increase of different condenser lenses with an increase in
the light flux. (2) The relative transmission of heat and visible light from an arc
source with glass of varying thickness. (A plate of 1 mm. thickness transmitted
about 80% visible and 50% heat, compared with 50% visible and 10% heat for
a thickness of 5 mm.)
Jan., 1930] ABSTRACTS 141
Description of the Mechanical and Optical Principles of the Mechau Pro-
jectors. L. BURMESTKR AND E. MECHAU. Kinotechnik, 10, Aug. 5, 20, Sept. 5,
1928, pp. 395-401, 423-6, 447-51. Uniformity of illumination as the film travels
across the first condenser, and the provision of an optically imaged gate for con-
tinuous projection are considered. Light from the crater of an arc is collected by
a reflector and projected on a condensing lens which forms on an aperture an
image of it proportional in size to the film frame. The light after passing the
lens is collimated and reflected by a tilting mirror and collected by another lens
combination which images the first aperture on the film at a magnification suf-
ficient to fill one frame. On the other side of the frame is a Petzval form of pro-
jecting lens which delivers parallel rays to a second tilting mirror. These rays are
collected and thrown on the screen by a final projecting lens. The 8 mirrors,
situated vector ially round a disk, are actuated by the revolution of the disk.
Each revolution brings 4 consecutive pairs of mirrors into operation and corre-
sponds to 4 frames.
Zoechrome. Kinemat. Weekly, 145, Mar. 21, 1929, pp. 69-70. The Zoe-
chrome process of color motion pictures, invented by T. A. Mills, was shown at a
demonstration in London. One double length negative is used. Every alternate
space of 8 perforations is occupied by a complete negative image of the object,
while the intermediate spaces are occupied by 3 / 4 size images taken through filters
cutting out the red, blue, and yellow-green, respectively. The black and white
negative is taken with an //3.5, 3 in. lens, while the color-selective negatives are
made with three lenses of about //4.0 and of shorter focus, bunched together to
reduce parallax, and placed immediately below the main lens. All four lenses are
mounted together for focusing. In printing, the alternate full images of the
negative are printed in immediate succession ; the positive is developed as usual,
varnished, and then recoated with emulsion. One of the small images is printed
by enlargement in register with the key image, developed, and dye-toned. The
film is again varnished, and recoated with emulsion and the cycle of operations is
repeated for the two remaining colors. The final film is no thicker than ordinary
film. On a basis of an output of 50,000 ft. a week the cost is figured at 5 cents a
foot.
Rapid Cameras. Lichtbildbuhne, 21, Nov. 3, 1928, pp. 16-9. Short history
of the development of high-speed cameras is given. The French scientist Marey
used a high-speed camera as a scientific implement and attained velocities of 140
exposures per second with a simple intermittent mechanism. Paper negative
was used in the earliest tests. His successor, by using a double pull-down, was
able to attain speeds of 250 pictures per second. Mention is made of rapid
cameras which use continuous moving film. In one type for certain kinds of sub-
jects the light source is intermittently flashed and speeds of 2000 to 100,000
exposures per second are possible. The Lehmann "Zeitlupe" introduced in 1916
employed optical compensation in the form of a rotating mirror-wheel, and could
be operated either at normal rate or as much as 300 to 500 pictures a second.
Modern high-speed cameras briefly described are the Debrie, Askania, Lyte, Bell
and Howell, and the Thun "Zeitdehner." The last named camera employs con-
tinuous moving film and a rotating wheel of lenses, with which velocities greater
than 4000 exposures per second are possible.
BOOK REVIEWS
Speech and Hearing. H. FLETCHER. D. Van Nostrand Co., Inc., New York
City, $5.50. 331 pp. The book is arranged in four parts to deal with the topics:
(a) speech, (&) music and noise, (c) hearing, and (d) the perception of speech and
music. Among the subjects discussed are the organs and the mechanism of speech
and hearing, recording instruments, speech power, audition limits, acuity of hear-
ing, and the various factors affecting the perception of speech and music. The
book has much experimental and theoretical information.
Motion Pictures with Sound. J. R. CAMERON. Cameron Publishing Co.,
Manhattan Beach, New York, 1929, $5.00. 393 pp. There is a brief description
of developments in sound picture reproduction from Edison's early attempts in
1886 to the latest methods of reproduction. General information, in popular
language, is given on sound transmission, the phonograph, telegraphy and teleph-
ony, vacuum tubes, and light-sensitive cells. New methods of lighting studio
sets with incandescent lights have been adopted as well as new silent running
cameras for sound work. The methods in common use for recording and repro-
ducing sound are: Recording with the light valve, R. C. A. Photophone, Movie-
tone, Bristolphone, Vitaphone, Cinephone, Simotone, and Phonofilm. Construc-
tion details of each are given, followed by instructions for operating R. C. A.,
Movietone, and Vitaphone equipment. The following types of ampli-
fiers are in use: Samson Pam, and Silver-Marshall phonograph, and
Rack and Panel ("PA") amplifiers. Characteristics of the Western Electric
horns, R. C. A. horns, and electro-dynamic speakers are enumerated. Other
chapters give information on the new sound screens, film splicers, film speed indi-
cators, and storage batteries. The Telegraphone is announced as still being at the
experimental stage; this, instead of having a disk or sound track on film record,
depends on a variably magnetized wire for its sound record.
Colour and Colour Theories. C. LADD-FRANKUN. Harcourt, Brace and
Co., New York, 1929. 287 pp. A complete discussion of three color theories,
namely: (a) Trichromatic, with no yellow and no white (Helmholtz). (b)
Tetrachromatic with white added (Hering). (c) Three stage evolution (Ladd-
Franklin). In the first stage, the elements are black and white, in the second
stage, yellow and blue are added, and in the third, red and green. The outer zone
of the retina is still in the front stage, the intermediate zone in the second, and only
the central area of the retina has reached the third. In red-green blind individ-
uals, the central area remains in the second stage, and in the totally blind the
whole retina is still in the first stage
Yearbook for Photography, Cinematography, and Reproduction Processes,
for the Years 1921-7. (Jahrbuch fur Photographic, Kinematographie und Re-
produktionsverfahren fur die Jahre 1921-7.) Vol. 30, Parts I and II. J. M.
EDER AND E. KUCHINKA. W. Knapp, Halle (Saale), 1928, $7.50. 480 pp. 960 pp.
The previous volume of this excellent review of photographic progress covered the
years 1915-20. Part I deals with apparatus for various kinds of photographic
142
BOOK REVIEWS
143
work. A historical review prefaces a description of cameras of all types, film
holders, shutters, exposure meters, camera supports and tripods, studios, etc.
Developments in lens design are comprehensively treated. Apparatus for proc-
essing films and papers are discussed, including enlargers, reducers, and projec-
tors. Equipment for applications of photography and processes of color photog-
raphy are described. Part II deals with cinematography, color sensitizing and
desensitizing, and physical and chemical actions of the photographic emulsion.
A list of some of the important subjects covered includes spectrum photography,
luminescence, sensitometry, the foundation of photographic negative processes,
photochemistry, radiations, silver bromide gelatin, emulsion making, dry plates,
and film.
SOCIETY OF MOTION PICTURE
ENGINEERS
OFFICERS
President
J. I. CRABTREE, Eastman Kodak Co., Rochester, N. Y.
Past President
L. C. PORTER, Edison Lamp Works, Harrison, N. J.
Vice-Presidents
H. P. GAGE, Corning Glass Works, Corning, N. Y.
K. C. HICKMAN, Eastman Kodak Co., Rochester, N. Y.
Secretary
R. S. BURNAP, Edison Lamp Works, Harrison, N. J.
Treasurer
W. C. HUBBARD, Cooper-Hewitt Electric Co., Hoboken, N. J.
Board of Governors
R. S. BURNAP, Edison Lamp Works, Harrison, N. J.
H. T. COWLING, Eastman Teaching Films, Inc., 343 State St.,
Rochester, N. Y.
J. I. CRABTREE, Research Laboratory, Eastman Kodak Co.,
Rochester, N. Y.
H. P. GAGE, Corning Glass Works, Corning, N. Y.
K. C. HICKMAN, Research Laboratory, Eastman Kodak Co.,
Rochester, N. Y.
W. C. HUBBARD, Cooper-Hewitt Electric Co., Hoboken, N. J.
W. C. KUNZMANN, National Carbon Company, Cleveland, Ohio.
D. MACKENZIE, Bell Telephone Labs., 463 West St., New York,
N. Y.
P. MOLE, Mole-Richardson, Inc., 941 N. Sycamore Ave., Holly-
wood, Calif.
L. C. PORTER, Edison Lamp Works, Harrison, N. J.
S. ROWSON, Ideal Films, Ltd., 76 Wardour St., London, W. 1,
England.
E. I. SPONABLE, Fox-Hearst Corp., 460 West 54th St., New York,
N. Y.
144
COMMITTEES
145
J. W. COFFMAN
COMMITTEES
1929-1930
Convention
W. C. KUNZMANN, Chairman
R. S. BURNAP
C. BARRELS
J. W. BOYLE
W. H. CARSON
W. CLARK
W. C. HUBBARD
Journal
L. A. JONES, Chairman
J. W. COFFMAN
H. T. COWLING
M. W. PALMER
W. C. HUBBARD
Membership and Subscription
H. T. COWLING, Chairman
L. W. DAVEE
J. DEFRENES
E. R. GEIB
J. KLENKE
M. L. MISTRY
B. E. NORRISH
I. ROSEMAN
E. C. SCHMITZ
J. L. SPENCE
F. ZUCKER
M. C. BATSEL
F. J. CADENAS
J. A. DUBRAY
O. M. GLUNT
Papers
J. W. COFFMAN, Chairman
C. R. HANNA G. E. MATHER
K. C. HICKMAN R. F. NICHOLSON
E. HUSE J. B. TAYLOR
D. HYNDMAN
Progress
G. E. MATTHEWS, Chairman
J. A. BALL R. E. FARNHAM R. C. HUBBARD
W. CLARK H. B. FRANKLIN C. LAIR
A. W. DANESHEW K. GEYER G. F. RACKETT
J. B. ENGL A. C. HARDY S. K. WOLF
H. W. DREYER
G. C. EDWARDS
T. FAULKNER
Projection
N. M. LAPORTE, Chairman
C. GREENE H. B. SANTEE
H. GRIFFIN L. M. TOWNSEND
W. A. MCNAIR D. F. WHITING
R. MlEHLING
W. B. RAYTON
F. C. BADGLEY
Publicity
W. WHITMORE, Chairman
B. w. DEPUE
G. E. MATTHEWS
G. F. RACKETT
O. A. Ross
146
COMMITTEES
J. W. COFFMAN
M. C. BATSEL
W. H. CARSON
A. DEBRIE
L. DEFOREST
J. A. DUBRAY
E. W. ENGSTROM
L. J. BUTTOLPH
F. A. BENFORD
A. C. DOWNES
Solicitation
B. P. CURTIS, Chairman
E. A. WlLLIFORD
Standards and Nomenclature
A. C. HARDY, Chairman
P. H. EVANS
H. GRIFFIN
R. C. HUBBARD
L. A. JONES
N. M. LA PORTE
W. P. POWERS
G. F. RACKETT
W. B. RAYTON
V. B. SEASE
T. E. SHEA
J. P. SPENCE
E. I. SPONABLE
L. T. TROLAND
Studio Lighting
A. C. DOWNES, Chairman
R. E. FARNHAM M. W. PALMER
K. C. HICKMAN
Theater Lighting
C. E. EGELER, Chairman
F. FALGE
R. E. FARNHAM
C. GREENE
E. HUSE
L. A. JONES
LONDON SECTION
SIMON ROWSON, Chairman
A. NEWMAN, Vice- Chairman PAUL KIMBERLEY, Manager
L. EVELEIGH, Secretary ALAN WILLIAMSON, Manager
H. WOOD, Treasurer WILLIAM VINTEN, Manager
PACIFIC COAST SECTION
P. MOLE, Chairman C. DUNNING, Manager
G. F. RACKETT, Sec.-Treas. E. HUSE, Manager
Membership Committee
J. COURCIER, Chairman
E. JEWELL
Papers and Programs
E. HUSE, Chairman
Membership
in the
Society of Motion
Picture Engineers
is open to all who are engaged
in any branch of the motion
picture industry or allied
work. The society is inter-
national in character and its
convention papers with com-
plete discussions are furnished
free to members.
REASONS WHY
YOU
SHOULD JOIN
The Society of
Motion Picture
Engineers
1 The S. M. P. E. is an internation-
ally recognized organization of
Motion Picture Engineers.
2 The S. M. P. E. is becoming an
ever more important factor in de-
veloping, stabilizing, and standard-
izing the motion picture industry.
3 At two conventions each year reli-
able data concerning a wide range
of subjects are presented long be-
fore they become available else-
where.
4 Papers read at conventions are
printed with full discussions in
a monthly Journal and distributed
free to all members.
5 The S. M. P. E. affords unique op-
portunities for personal contact
with leaders in the industry.
6 S. M. P. E. publications are recog-
nized standard authority on Mo-
tion Picture Engineering.
7 The S. M. P. E. will help you in
many ways. Join now.
COUPON
HERFORD TYNES COWLING, Chairman
Membership Committee, Society of Motion Picture Engineers
343 State Street, Rochester, N. Y.
Dear Sir
Please mail application blank and requirements for membership in the S. M. P. E. to
Name
Position . . .
(Please print)
(Company or other Affiliation)
vStreet and City Address
Name
Position
Street and City Address. .
JOURNAL
OF THE SOCIETY OF
MOTION PICTURE ENGINEERS
LOYD A. JONES, EDITOR pro tern.
Associate Editors
G. I/. CHANIER
O. M. GLUNT
A. C. HARDY
P. MOLB
W. B. RAYTON
P. E. SABINE
S. E. SHEPPARD
J. L. SPENCB
L. T. TROI,AND
Volume XIV
FEBRUARY, 1930
Number 2
CONTENTS
Page
151
Theater Acoustics for Sound Reproduction S. K. WOLF
Loud Speakers for Use in Theaters
D. G. BLATTNER AND L. G. BOSTWICK 161
Art and Science in Sound Film Production. .JoE W. COFFMAN 172
Photographic Characteristics of Sound Recording Film
LOYD A. JONES AND OTTO SANDVIK 180
The Modern News Reel HARRY W. JONES 204
Film Perforation and Its Measurement. .WALTER H. CARSON 209
The Human Equation in Sound Picture Production
TERRY RAMS A YE 219
Progress in the Motion Picture Industry. Report of the
Progress Committee 222
Abstracts 259
Book Reviews 262
Officers 264
Committees 265
Jst of New Members and Transfers 267
nety Notes 267
Published Monthly by the
SOCIETY OF MOTION PICTURE ENGINEERS
20th & Northampton Sts., Easton, Pa.
Editorial Office: 343 State St., Rochester, N. Y.
Subscription to non-members $12.00 per year, single copies $1.50. Order from
the Secretary of the Society of Motion Picture Engineers, 5th & Sussex Streets,
Harrison, N. J. ,
Copyright
BY THE SOCIETY OF
MOTION PICTURE ENGINEERS
PERMANENT MAILING ADDRESS OF THE SOCIETY
Engineering Societies Building
29 West 39th Street
New York, N. Y.
Papers or abstracts may be reprinted if credit is given to the Journal of the
Society of Motion Picture Engineers.
The Society is not responsible for statements made by authors.
Application pending for entry as second-class matter at the Post Office at
Easton, Pa.
THEATER ACOUSTICS FOR SOUND REPRODUCTION
S. K. WOLF*
The advent of sound pictures is, no doubt, the chief single cause of
the practical importance now conceded to acoustics. The science of
acoustics is being greatly extended and altered by this most popular
diversion.
Professor Wallace C. Sabine was the first to study architectural
acoustics with practical as well as academic interest. For years after
the first publication of his results, commercial interest was entirely
lacking. Although theatrical interest in acoustics is limited almost
solely to its practical phases, a theoretical study must also be main-
tained for the advancement of the science. Advances in our knowl-
edge of acoustics, as well as in the physiology of hearing, have ma-
terially aided us in the study of practical acoustics.
During our brief study of theater acoustics, for reproduced speech,
we have found the empirical deductions of Sabine and others, whose
study was made for original speech conditions, are not wholly appli-
cable to acoustics for sound reproduction in their present form.
Differences in acoustic requirements for original and reproduced
speech have been observed by other workers in the field of acoustics.
Dr. W. H. Eccles in a recent address entitled, "The New Acoustics,"
identifies the field of acoustics dealing with the reproduction of
sound as "electro-acoustics."
The first important observation, in our study of electro-acoustics,
was that theaters theoretically meeting the optimal periods of
reverberation advocated by Sabine and others were not as satis-
factory for sound reproduction as would be expected. The second
observation was that some theaters were more satisfactory for re-
produced sound although these theaters had lower periods of reverber-
ation. In the two foregoing observations the reproduction of speech
as well as music was considered, resulting in what we believe to be a
fair compromise. Being convinced that lower periods were desirable
* Electrical Research Products, Inc., New York City.
151
152
S. K. WOLF
Lf. S. M. P. E.
for reproduced sound than for original sound our problem was then to
determine the cause of this discrepancy.
Reverberation vs. Intensity. Our first and perhaps the most
obvious consideration was the inherent difference in sound intensities
of original speech and reproduced speech. In large theaters it is
necessary to increase sound intensities in order to obtain proper dis-
tribution throughout the audience. There is, in addition, the psycho-
logical effect due to increased size of characters on the screen as com-
pared with stage characters. Aside from the theoretical considera-
tions there are those of carelessness, resulting in the improper level of
100
90
60
50
40
20
40
60
80
100
120
^VOLUME IN FEET
FIG. 1 . Relation of reverberation time to volume of an auditorium at various
loudness levels above the threshold of audibility.
operation of the reproducing system. This fact is often brought to
our attention by friends who have been driven out of theaters by the
deafening level at which reproducing systems are sometimes operated.
Even today there are Broadway houses where pictures of unusual
merit and excellent recording are shown which nevertheless lose pa-
trons nightly because of the discomforting and unnatural sound
level at which the program is being reproduced. However, this
paper is concerned only with proper level operation.
In determining theoretically the magnitude of the effect of increased
sound intensity on the factors affecting reproduction, we naturally
Feb., 1930] THEATER ACOUSTICS FOR SOUND REPRODUCTION 153
consider first, the most important and most serious obstacle to good
acoustics reverberation.
From the work of Sabine, Jaeger, Buckingham, and others, who
have laid the foundation for our present accepted theory of reverbera-
tion, we are able to evaluate the effects of increased intensity on
reverberation. From these effects we have described, graphically,
a family of curves showing the time of reverberation in relation to the
size of the theater. These various sound intensity relations have
been computed at intervals of ten decibels, from 40 to 100 above the
threshold of hearing, at C-4 or 512 cycles. These curves are shown
in Fig. 1. The curve of 60 decibels represents a million times the
threshold intensity, and is the intensity used by Sabine, and others,
the standard method of measuring the time of reverberation.
The following is a list of symbols which will be used throughout
this discussion.
V = volume of the room in cubic meters.
E = acoustic output of source of sound in ergs per second.
/ = energy density expressed in ergs per cubic meter.
I = steady state of energy density.
i = threshold of audibility.
t] = time of reverberation in seconds.
K = substitution constants.
v = velocity of sound in meters per second.
p = mean free path of any sound element between reflections.
a = total absorbing power of the room.
S = total area of bounding surfaces.
= average number of reflections per second.
P
a
- = mean absorption coefficient.
o
A = constant of proportionality, the ratio of the rate of decay of the residual
sound to the intensity at the instant.
Derivation of Steady State and Reverberation Time Relations. The
of change of the average sound intensity due to absorption at
bounding surfaces of the room is given by
ie rate of change of energy density in the room with the source
speaking is
154 S. K. WOLF [J.S. M. P.E.
E dl
Under the steady state conditions at which absorption at the bounda-
ries is just balanced by generation of sound energy at the source, the
energy density or intensity I is
f -- AI =
For the transient condition of decay we find that by integrating (1)
and supplying the steady state constants the solution becomes
L E
At = log e j = log e -^j. : ..................... (4)
From this we find if t\ is the time required for the energy density level
to decrease to i, the threshold of audibility, that (4) becomes
E
Ak = log e ............................... (5)
By the kinetic theory we find that the mean free path may be thus
expressed
4F
5
But by the general theory
P - -J (6)
v a
or substituting (6)
Thus equation (5) becomes
A -
A ~ 4V
av 4E
* ' **
or
Feb., 1930] THEATER ACOUSTICS FOR SOUND REPRODUCTION 155
.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
t - IN SECONDS
FIG. 2. Growth and decay of sound intensity for syllable emission originally
produced in an auditorium having excessive reverberation time.
4V 4E V 4E
= log e . = 9.2 /ogio .
v aw v am
.(7)
For the particular problem involved we have then two available equa-
tions to use, namely
4E
av
156
S. K. WOLF
[J. S. M. P. B.
and
V 4E
= 9.2 log w ;
av B am
Theoretical Component Reverberations. The effect of reverberation
on the quality of original speech is admirably shown in the work of
o.oi
.008
1.0
t - IN
SECONDS
FIG. 3. Growth and decay of Sound intensity for syllable emission originally
produced in an auditorium having acceptable reverberation time.
Dr. Eckhardt. In Fig. 2 are shown the intensity and growth curves
and decay curves of a number of successive syllables computed for a
room of small absorbing power. The total intensity curve for the
room is obtained by adding the intensity time curves of all syllables.
This curve is shown bythe dotted line in Fig. 2, and clearly illustrates
the effect of reverberation on intelligibility. In Fig. 3 the values
?eb., 1930] THEATER ACOUSTICS FOR SOUND REPRODUCTION 157
shown for a room in which the interior finish has been provided
with sufficient absorbing material to produce the proper period of
reverberation for original speech. It is clear, from a comparison with
Fig. 2, that a more satisfactory condition of intelligibility could be
expected. Fig. 4 carries the absorption of sound one step farther,
producing a highly damped condition. In this case, the intensity of
each syllable practically reaches the saturation value for continuous
emission at the same rate. Fig. 4 also shows that very little sound
intensity of a syllable remains when the succeeding syllable begins.
.003
.002
.001
2
1.0
t- IN SECONDS
?IG. 4. Growth and decay of sound intensity for syllable emission originally
produced in an auditorium having too small reverberation time.
Fig. 5 is a theoretical curve showing the combined effects of studio
and theater reverberation on reproduced sound. It seems logical to
assume that the combined effects of sound growth in a studio and
sound growth in a theater will produce an intensity growth curve, the
slope of which will never be greater than, and generally less than, that
for direct speech. The assumption is based on the fact that the sound
source in the theater is not constant and is less continuous than the
original sound. Likewise, in considering the decay curve, resulting
from the combined effect of the studio and theater acoustic condi-
158
S. K. WOLF
[J. S. M. P. E.
tions, we would expect the rate of decay never to be greater than,
and generally less than, that of original speech. These combined
effects, of both studio and theater growth and decay, will tend to in-
crease the duration of reproduced sound over original sound. From
these phenomena we may deduce that reproduced sound will always
require shorter periods of reverberation than will original sound. This
factor is likely to be somewhat small. Under practical conditions
and to the average hearer, these differences are not as great as the
theoretical curves would indicate; nevertheless they should be con-
.003
.002
.001
1.0
- IN SECONDS
FIG. 5. Theoretical curve showing growth and decay of sound intensity
for syllable emission reproduced in an auditorium having too small a rever-
beration time for direct audition.
sidered particularly because an accumulative effect is produced
under the existence of increased intensity of reproduced sound.
Reproduced Speech Intensity vs. Original Speech Intensity. If we
assume that the average increased level of reproduced speech intensity
over original speech intensity is of the order of magnitude of 10 deci-
bels, we may determine the proper relative time of reverberation for
reproduced speech as the time of reverberation varies directly with
the intensity in decibels. This conclusion having been reached, and
knowing the curves of Sabine, and others, to be based on 60 decibels
Feb., 1930] THEATER ACOUSTICS FOR SOUND REPRODUCTION 159
I*
2 <
20 40 60 80 100 120
FIG. 6. Calculated optimum reverberation time for reproduced speech in
comparison with that for original speech.
for original speech, we may determine the optimum curves for re-
produced sound by the simple ratio of 60 to 70. This relation is
shown in Fig. 6.
Comparison of Optimum Reverberation Times. A large number of
theaters were selected to determine, in a practical way, the optimum
VOLIME IN
FEE
10 20 30 40 50
70 80 9O
^s^
O-OPTIMUN TIME
F -WATSON S FULL HOUSE
2-LIFSHITZ
3-SABINE
IJO I4U OO IOO
FIG. 7. Optimum reverberation times as advocated for original sound by
Watson (F) Lifshitz (2) Sabine (3) and for reproduced sound (O).
160 S. K. WOLF
time of reverberation for sound reproduction. These theaters were
all considered to be excellent by competent observers for sound re-
production as judged on a qualitative basis. We have subjected
them to a quantitative analysis to determine their characteristics for
sound reproduction. Fig. 7 shows the comparison of optimum rever-
beration times that have been advocated and the relative location of
the selected theaters. Curve 2 shows Lifshitz' advocated optimum
time of reverberation. Curve F shows Watson's full house values and
curve 3 shows the optimum times of reverberation advocated by Sa-
bine. The curve labeled "0" is an optimum time of reverberation
which we believe to be an optimum for reproduced sound.
REFERENCES
ECKHARDT, E. A.: "Acoustics of Rooms," Jour. Frank. Inst. (June, 1923),
p. 799.
FLETCHER, H.: "Useful Numerical Constants of Speech and Hearing," Bell
System Technical Jour. (July, 1925).
JAEGER, G. : "Zur Theorie des Nachhalls," Acad. Wiss. Wien, Sitzungsberichte
(May, 1911).
LIFSHITZ, SAMUEL: Phys. Rev., 27 (1926), pp. 618-621.
SABINE, P. E.: "Measurement of Sound Absorption Coefficients."
SABINE, W. C.: "Collected Papers on Acoustics."
WATSON, F. R.: "Ideal Auditorium Acoustics," Jour. Am. Inst. Architects
(July, 1928).
DISCUSSION
MR. KELLOGG: I should like to ask Mr. Wolf whether there were many
theaters that they had a chance to test having a shorter reverberation than was
found to be good. Getting a short period of reverberation is expensive. Theaters
are generally built for good acoustics in view of previous standards, and theaters
falling below those conditions might be good for acoustical work, but they are
so few in number that they might not have been available for test.
MR. WOLF: In our analysis, we have found a number of theaters whose
period of reverberation falls below the 10 per cent line given in my paper. In
these theaters articulation and intelligibility of speech were improved somewhat
while the loss in brilliance of music reproduction was considerable. The periods
advocated represent a compromise between speech and music.
LOUD SPEAKERS FOR USE IN THEATERS
D. G. BLATTNER AND L. G. BOSTWICK*
INTRODUCTION
There are at the present time two types of loud speakers generally
available for use in theaters, the horn type and the free radiator baffle
type. Although these two types as usually used in theaters are
similar in that they employ moving coil driving elements, they differ
materially in their performance characteristics, and for theater pur-
poses where large sound powers are required these differences become
very important. Some of the inherent characteristics of these two
types of loud speakers are discussed in a general way in the following
paragraphs and the effects of these characteristics upon the require-
ments of theater systems are illustrated.
PERFORMANCE CHARACTERISTICS
Efficiency. The absolute efficiency 1 (the ratio of the actual acoustic
power delivered to the air load to the acoustic power that would be
delivered from the same electrical source if the loud speaker were
ideal) of the baffle type speaker is inherently lower than that of the
horn type. This is due to the fact that the baffle device depends
upon the existence of a mass controlled vibrating system 2 for its
uniformity of response at different frequencies. The radiation re-
sistance of such a system is small in comparison with the mass re-
actance so that the driving force is largely consumed in accelerating
the mass and but little is effective in producing sound. An inefficient
loud speaker must therefore result. In the horn type speaker, how-
ever, the situation is quite different. In this case the load resistance
on the diaphragm can be made large compared to the mass reactance
of the vibrating system at least for a considerable portion of the fre-
quency range. The impedance relations are therefore much more
* BeU Telephone Laboratories, New York City.
1 See definition in Report of I. R. E. Standardization Committee of 1929.
2 RICE AND KELLOGG A. I. E. E. (April, 1925).
161
162 D. G. BLATTNER AND L. G. BOSTWICK [j. s. M. P. E.
favorable and in this type of device absolute efficiencies of 25 per cent 3
or better can be obtained over a broad frequency range. In com-
parison with this, uniform efficiency values greater than 2 or 3 per
cent over a comparable frequency range are difficult to obtain with
the baffle type although baffle devices that resonate within the
transmitted frequency range may have efficiencies near resonance
somewhat greater. Aural observations in theaters and response 4
frequency measurements in laboratories indicate that for a given
sound loudness, the source of electrical supply to good horn type loud
speakers is 8 to 12 decibels less than that required for good baffle
speakers, the exact figure being somewhat dependent upon the
individual speakers and the energy distribution in the frequency
band of the program supply source.
Frequency Range and Uniformity of Response. Fundamentally
the horn and the baffle type of speaker appear to be about equally
satisfactory from the standpoint of frequency range of sounds that
can be produced efficiently. Well designed speakers of either kind
using a single type of driving unit can be relied upon to be quite
uniform in response for frequencies up to about 6000 cycles. Above
this frequency the response of both speakers diminishes rather
rapidly. At the low frequencies the horn cut-off limits the range of
the horn type speaker and the size of baffle, the natural period, and
the permissible amplitude limit the range of the baffle device.
Horns can be readily constructed to have very low cut-off fre-
quencies but the dimensions and the costs of such horns become in-
creasingly large as the cut-off frequency is lowered.
Baffle type speakers on the other hand need not be seriously re-
stricted by the baffle size or the natural frequency but in commercial
devices there is a limiting low frequency range due to the maximum
amplitude of vibration allowable by the construction. At low fre-
quencies the radiation resistance of a small piston varies as the square
of the frequency so that for frequencies of the order of 50 or 60 cycles
the radiation resistance is very small. Very high velocities and
large amplitudes of vibration are therefore required to radiate sound
powers readily radiated by lower velocities and smaller amplitudes
at the higher frequencies. A piston type diaphragm 10 inches in
diameter and designed to have a maximum double amplitude of
3 WENTE AND THURAS, Bell System Tech. Jour. (January, 1928).
4 See definition of response in Report of I. R. E. Standardization Committee
of 1929.
Feb., 1930]
LOUD SPEAKERvS
163
vibration of 0.25 inch (a value requiring large dimensions, and
possibly some difficulty in the design, of the supporting and driving
system) will radiate a maximum acoustic power of about 0.2 watt
from each side at a frequency of 60 cycles. At higher frequencies the
radiation resistance increases rapidly so that for the same amplitude
of motion the output from the above diaphragm at a few hundred
cycles may be several times the maximum 60 cycle value. Conse-
quently for constant sound power outputs greater than 0.2 watt,
the minimum frequency must be higher than 60 cycles. It will
thus be clear that for large sound power outputs such as are required
in theaters, the vibration amplitude and the baffle size constitute
1-50 CYCLE CUT-OFF EXPONENTIAL HORN
OF INFINITE LENGTH.
2-10" PISTON DIAPHRAGM IN INFINITE BAFFLE.
600 1000 1200
FREQUENCY-C.PS.
FIG. 1.
Curves showing radiation resistance of two types of radiators for
various frequencies.
a low frequency limitation of the baffle speaker somewhat analogous
to the cut-off frequency of the horn in the horn type speaker.
As to the uniformity of response at different frequencies the best
designs of horn and baffle type speakers show no definite advantage
of one over the other. Good horn and good baffle type speakers
having comparable frequency ranges, sound very much alike when
installed in a theater and alternately connected to the same program
supply source.
Sound Field Distribution Characteristics. The angle subtended by
the more intense portion of the sound field at any given frequency is
somewhat greater for the baffle than for the conventional horn type
164 D. G. BLATTNER AND L. G. BOSTWICK [j. s. M. P. E.
speaker. The baffle speaker therefore permits a larger departure of
the listener from the axis of the sound field. This difference in the
two types does not seem to be fundamental but is effectively over-
come when two or more horns are used simultaneously and pointed at
different portions of the theater. Such a scheme has the further
advantage of increased reliability of operation.
Another difference in the distribution characteristics of the two
types of speakers results from the fact that the baffle speaker radiates
effectively from both sides of the diaphragm while the horn type
radiates effectively from only one side. Because of this character-
istic of the horn type speaker less attention need be given to the region
back of the horn to prevent certain acoustic effects that might ad-
versely influence the performance as observed from the front.
Input Power Capacity. b The input power capacities of baffle and
horn type loud speakers are usually limited either by excessive tem-
perature rise of the moving coil or by mechanical restrictions of the
vibration amplitude. The temperature rise depends upon the elec-
trical resistance of the moving coil which in turn is determined by the
size and material of the coil conductor. It is necessary in both
types of loud speakers to use very light coils in order to obtain suitable
response at high frequencies and there appears little basis for choosing
either type as having the advantage from this standpoint.
As discussed under the section, "Frequency Range," the acoustic
power output from the baffle type speaker is definitely limited at low
frequencies due to mechanical restriction of the vibration amplitude.
Since the radiation resistance of the baffle speaker becomes very
small at low frequencies, much larger amplitudes are required to
radiate a given sound power than are required by the horn type in
which the radiation resistance is large and essentially constant.
Fig. 1 shows the approximate relation between frequency and radia-
tion load for a 50 cycle cut-off exponential horn and also for a 10 inch
piston. For the same ultimate radiation load it will be clear from
the figure that at low frequencies the amplitude of the horn type
6 The input power capacity is determined by the ratio
4r
where e is the maximum open circuit r.m.s. voltage of the electrical supply
source (amplifier), measured at the loud-speaker terminals, for which satisfactory
operation of the speaker will result; and r is a resistance equal in magnitude to
the impedance to which the receiver is designed to be connected.
Feb., 1930] LOUD SPEAKERS 165
speaker will be much less than that of the baffle speaker when equal
acoustic outputs obtain. Measurements on commercial speakers and
considerations as to practical design indicate that the maximum
vibration amplitudes of baffle and horn type speakers allow acoustic
power outputs over the frequency range of interest in sound picture
work that are about in the ratio of the respective efficiencies. It
follows then that the input power capacities of the two types of
speakers are roughly equal.
The above discussion of the relative performance characteristics of
horn and baffle type speakers may be summarized briefly as follows:
The baffle type speaker is 8 to 12 decibels lower in efficiency; the
frequency range and uniformity of reproduction are not funda-
mentally different for the two types; the sound field distribution
characteristics are about equally favorable for theater work; and the
input power capacities for suitable commercial devices of broad fre-
quency range are about the same, although the acoustic output ca-
pacity of the horn type device is considerably greater. While the
considerations upon which these conclusions are based are of a
general rather than a specific nature it seems reasonable to apply
these deductions to the discussion to follow.
THEATER INSTALLATIONS
For theaters where large acoustic powers are required the differ-
ences between the performance characteristics of the baffle and the
horn type loud speakers discussed above are very important, if
equally satisfactory results are to be obtained. Due to the horn
being about 10 decibels (8 to 12 decibels mentioned above) more
efficient than the baffle speaker the amplifier associated with the
baffle must be capable of delivering ten times as much electrical
power as the amplifier associated with the horn speaker. Unless the
greater power capacity amplifier is provided in the baffle speaker
system excessive distortion will result if equal sound powers are to be
obtained. As tjie acoustic power required becomes larger the
difference in cost between the amplifiers required to supply adequate
powers without distortion becomes an increasingly important item.
Also, the horn type speaker has the further advantage of greater
acoustic power output capacity and this also becomes increasingly
valuable for larger acoustic powers. Thus if the acoustic power re-
quired is greater than the baffle speaker is capable of delivering,
several baffle speakers would have to be used and the number would
166
D. G. BL-ATTNER AND L. G. BOSTWICK [J. s. M. P. E.
be greater than the number of horns required to deliver the same
power. The importance of these considerations obviously depends
upon the required acoustic power output, the larger the requirement
the more important it becomes to have the loud speaker of higher
efficiency and larger acoustic power capacity. In order to obtain a
more definite idea of the significance of these differences of perform-
ance capabilities some general information as to the acoustic power
requirements for theaters of different sizes will be given below to-
gether with certain requirements necessary for two typical sizes of
theaters; first when using horn type loud speakers and then when
using baffle type loud speakers.
2 "10 = 3*10 5
THEATRE VOLUME -CUBIC FEE!
FiG. 2. Acoustic power required in theaters of various sizes.
General Acoustic Power Requirements for Theaters. Fig. 2 shows a
curve expressing the relation between theater volume in cubic feet
and the maximum sinusoidal acoustic power in watts which the loud
speaker must be capable of delivering in order that the sound loudness
in the theater be satisfactory for sound picture use. The curve was
obtained from calculations based upon experience in a large number of
typical theaters of various sizes. In such places the reverberation
times are usually such as to justify the application of steady-state
theory so that 6
6 Crandall, "Theory of Vibrating Systems and Sound," p. 210.
Feb., 1930] LOUD SPEAKERS 167
-?......; : :<
where
R = the average energy density.
P A = the acoustic power delivered by the sound source.
c = the velocity of sound propagation.
a = the summation of the products of the surface areas by
their respective absorption coefficients.
From Sabine's reverberation equation the quantity a may be ex-
pressed in terms of the room volume V and the reverberation time T.
Thus
aT = KV
or
KV
a = -f .-(2)
Substituting (2) in (1) and rearranging gives
KVcE V
PA = JTJT = K'E- (3)
Theater observations with known values of P A and V and computed
values for T (using Lifshitz' equation 7 ) permitted an evaluation of
K'E for sound intensities which were judged satisfactory for sound
picture work. Assuming that the same energy densities are required
for other theaters it is then possible by means of equation (3) to
evaluate P A for a properly damped theater of any size. Fig. 2
shows the results of such computations. While this curve is based on
observations in a number of theaters it has not been verified ex-
tensively and is presented here merely as an aid in the following dis-
cussion.
Small Theater Installation. Consider now the case of a small
theater. It has been found from surveys of a large number of sound
picture theaters that the average size of the small theater (less than
100,000 cubic feet) is about 70,000 cubic feet with a seating capacity
of about 650 people. Assuming this value of 70,000 cubic feet for
purposes of discussion and referring to Fig. 2 it will be clear that the
average small theater should have loud speakers capable of delivering
an acoustic power of 0.46 watt. Such theaters will then require the
7 Physical Review (March, 1925).
168 D. G. BLATTNER AND L. G. BOSTWICK [j. s. M. P. E.
use of an amplifier of 1.84 watts output capacity for use with horn
type speakers 25 per cent efficient, or 18.4 watts capacity for use with
good baffle speakers. Assuming that the horn type speaker and the
baffle type speaker each are capable of handling a maximum sinu-
soidal electrical power of 6 watts (a value that seems to have some
experimental backing), it will be clear that in the first case a single horn
type speaker is capable of handling the total output required of its
amplifier but we will assume that two such speakers would be used in
order to obtain satisfactory distribution. In the second case it will
be observed that three baffle speakers are required to handle the
power output required from their amplifier. Therefore for an eco-
nomical balance in cost of equipment the three baffle speakers should
cost less than the two horn type speakers by an amount equal to the
difference in cost of the two amplifiers.
Now let us consider the relative costs of the two types of amplifiers.
On the above basis as to efficiency and power capacity of the speakers
the amplifier for the baffle speaker installation should have 10 decibels
more gain and ten times the power capacity of the amplifier for the
horn installation. An increase in gain of 10 decibels if effected at
low power capacity is not particularly expensive, but where the gain is
already considerable and the circuits are otherwise complicated this
increase in gain may increase the cost of design and installation to
insure satisfactory operation. From the standpoint of power ca-
pacity the increase required necessitates the use of higher power
vacuum tubes and current supply apparatus which requires larger
amounts of iron and higher voltage insulation in transformers and
choke coils and more costly mountings. In view of these factors and
the large powers required in theaters, it might be assumed that the
relative cost of two amplifiers having the same features would not be
greater than the ratio of their power capacities, nor perhaps less than
the square root of their capacities. Assuming the relative cost to be
the latter figure as an approximation it will be clear that since the
power capacities are in the ratio of 10 : 1 the cost of the baffle speaker
amplifier will be approximately three times that of the horn speaker
amplifier.
For the small theater installation it, therefore, appears that baffle
type speakers can be justified only if three such speakers are pro-
curable at a cost less than that of two horn type speakers by twice the
cost of the horn speaker amplifier.
Large Theater Installations. The situation in large theaters is even
I
.
Feb., 1930] LOUD SPEAKERS 169
less favorable for the use of the baffle speaker than it is in small
theaters. This is due to the fact that as the required acoustic power
increases, the difference in the number of speakers necessary to carry
the power becomes greater and the additional power capacity of the
amplifier becomes more expensive. Consider for example a theater
having a seating capacity of 2250 and a volume of 460,000 cubic feet.
From the curve in Fig. 2 such a theater would require an acoustic
output from the loud speakers of about 2.3 watts. Horn type loud
speakers used in this theater would require an amplifier capable of
delivering 9.25 watts, and the number of horn type speakers required
to carry the power need not in general be greater than in the case of
the small size theater discussed above. 8 On the other hand baffle
type speakers would require an amplifier capable of delivering 92.5
watts and at least 15 speakers to carry the power. The power ca-
pacities of the amplifiers are still in the ratio of 10:1, so that for the
above assumptions it would appear that fifteen baffle type speakers
must be procurable at a cost less than that of two horn type loud
speakers by twice the cost of the horn speaker amplifier. The cost of
the baffle speaker for large theaters must therefore be considerably
less than that justified for the small theater installation.
CONCLUSION
In this paper the performance characteristics of baffle and horn
type loud speakers have been discussed in a very general way and the
bearing of certain inherent differences between the two types upon the
economy of theater installations has been illustrated. It is, of course,
impossible to draw any precise conclusions from such reasoning since
baffle and horn type speakers may each vary considerably in their
performance characteristics. The comparative values assumed in
this paper, however, are fairly well substantiated not only by the
better existing designs but also by theoretical consideration of possible
future improvements. For example, it may be quite possible to
improve the efficiency of existing baffle speakers, but on the other
hand a considerable improvement in horn type speakers also seems
practicable. The same may be said of the power capacity of each
type. Other factors such as the use of several loud speaking receivers
on the same horn, the effect at low frequencies of using a plurality of
:
8 In some cases where distribution difficulties are encountered as many as
;three or four horns have been used in theaters of this size.
170 D. G. BLATTNER AND L. G. BOSTWICK [j. s. M. p. B.
baffle speakers in close proximity, and design considerations have been
outside the scope of this paper, but such factors do not greatly influ-
ence the case and an advantage to one type of speaker is offset by
other advantages to the other type. It, therefore, does not seem un-
reasonable to conclude in a very general way that for theater in:alla-
tions general considerations favor the use of horn type loud speakers.
DISCUSSION
MR. PALMER: Can Mr. Blattner tell us anything about the condenser type
of speaker and its relative advantages?
MR. BLATTNER: Dr. Kranz has done a considerable amount of work on the
electrostatic type of loud speaker and I am sure will be able to describe its out-
standing characteristics better than I.
DR. KRANZ: I can't give you any quantitative, comparative data on this point.
Mr. Blattner has described in his paper a serious limitation in the baffle type of
speaker resulting in a low sound power capacity at low frequencies. So far as
the electrostatic speaker is concerned this limitation does not apply.
MR. CRABTREE: Do I understand that one watt is sufficient for a theater of
500-seat capacity? Is that amount of power capable of reproducing with any
degree of realism, for instance, a bass drum, or a bass horn, or a falling building?
MR. BLATTNER: Let me repeat for Mr. Crabtree's benefit that the ordinate of
the curve Fig. 2 is the acoustic power output required from the loud speaker.
So far as we are able to determine the curve shows the acoustic power actually
delivered in theaters today. In discussing a previous paper someone in this
audience complained that the theater managers are "blowing their customers
out of their seats." In general I believe that voices are reproduced at least as
loud as the original. As for incidental noise effects, I doubt if it is practical or
even necessary to reproduce the noise of a falling building as loud as the original.
MR. KELLOGG: I think one of the first calculations of the efficiency of a cone
in a baffle was in a paper by Chester W. Rice and myself published in the A. I.E. E.
in 1925, based on formulas given in Rayleigh's "Theory of Sound." The efficiency
came out about three per cent, which is the figure Mr. Blattner gave. I didn't
know of that figure being challenged until Mr. E. D. Cook, who was with the
General Electric Company at that time, when making careful measurements by
means of the motional impedance of the cones came out with a figure of 9 per cent.
It was a surprise to me, and I cannot vouch for that figure, but I think 3 per cent
is low. The 3 per cent estimate was based on the assumption of a perfect plunger
in a baffle. In most of our units, the cabinet seems to build up the response in
the bass range, above that obtained with a baffle. In the high frequency range
the efficiency is raised by the fact that the cone cannot function as a perfect
plunger, but it breaks up into resonance and under these conditions is more
efficient than a simple, ideal plunger. On the other hand, the tests that Mr.
Cook made with the horns indicated that while they might give a theoretical
efficiency of 25 or 30 per cent in the mid range, there was a loss difficult to explain
in the high frequency range, and these factors offset the large predicted difference
in efficiency between cones and horns. Further measurements are needed, but
Feb., 1930] LOUD SPEAKERS 171
measurements as ordinarily made are hardly a satisfactory basis for estimating
efficiency because of the concentration of sound in a beam. The efficiency is not
a complete measure of utility; the beam intensity may be a better measure of
Utility than total sound radiated. Both factors come in, their relative importance
depending largely on room acoustics, but when we talk about efficiency, we have
to base it on the total sound radiated, and it is difficult to make a comparison.
MR. TOWNSEND: I am wondering about the same thing that Mr. Crabtree
spoke about with regard to the amount of power required. I use an amplifier
in my home which has an undistorted output of approximately 15 watts. I
don't use that for loudness but for quality. If we go down to one watt in even
a small theater it appears to me that the quality of sound would be rather poor.
The theater with which I am connected happens to have six dynamic speakers,
and six air column horns with dynamic units.
I can switch from the horns to the baffle type speakers and as nearly as the
ear can follow, either will give the same volume in the theater. It is impossible
to get any difference in volume between those two sets of speakers connected to
the same output transformer and using the same gain. It has been a puzzle to
me to find out where the difference in efficiency really is.
MR. BLATTNER: Referring to Mr. Kellogg's remarks, we agree that efficiencies
of 8 or 10 per cent can be obtained with baffle speakers over a limited frequency
range. Our figure of 3 per cent refers to the overall efficiency for a broad band
and checks satisfactorily with the difference between the generally accepted
efficiency figure for the better grade of horn type speakers and the difference in
loudness between the two types as observed throughout the theater auditorium.
I believe we have adequately covered the question as to relative high frequency
response and directivity in the paper.
As for Mr. Townsend's remarks I am unable to explain the lack of difference
in performance in his two types of speakers. To do so, it would be necessary to
know the characteristics of the particular device that he uses. There is a con-
siderable range in the merits of the device of both types generally available in
the market. The discussion in the paper applies to what we termed "well
designed" devices of the two types.
ART AND SCIENCE IN SOUND FILM PRODUCTION
JOE W. COFFMAN*
Much has been said about the conflict, real or apparent, between
science and religion. We also hear of bickerings between science and
art. It would seem that Lady Science, to whom we all profess devo-
tion, has her very feminine moments devoted to spying upon her
sisters, whom she scandalizes by broadcasting the intimate items she
discovers by such investigations.
But science and art are not natural enemies rather, they are
natural complements. Science reveals nature art makes life livable
in spite of those revelations. Science represents the accomplishments
of man art, his aspirations. Science moves slowly but surely
toward the conquest of the air but the Pegasus of art has for cen-
turies sailed the skies. And as aspiration tends to become accom-
plishment, the art of today becomes the science of tomorrow. And
yet, paradoxically enough, art begins where science ends, for the
foundation of all art is science, whether that science be conscious or
unconscious. Art is empirical science, mathematical. Science seeks
realism art seeks illusion. But, for the tools to create illusion, art
turns to science, the sturdy champion of reality.
This interdependence of science and art is nowhere more striking
than in motion picture production. We cannot be really scientific
in the attack upon our problems unless we recognize and evaluate the
many artistic factors bearing upon the work at hand. So let us
review the industry as it stands today.
The first year of active sound film production has been devoted
largely to experimentation and to the struggle for survival of the
fittest among technicians and their respective technics. Much of
the production reaching the public screen has been produced hastily,
with inadequate equipment and by inexperienced personnel. These
handicaps have not been without beneficial result, however, for they
forced experimentation. This sometimes resulted in the development
of very useful equipment and flexible production methods, and re-
* Audio-Cinema, Inc., New York City.
172
. ;; -
ART AND SCIENCE IN SOUND FILM 173
vealed the fact that sound pictures may be produced successfully
under a wide range of conditions which had previously been consid-
ered impossible.
Art is at its best when not limited by rigidity in its medium of
expression; and it is strongly believed that every step toward re-
moval of the present restricting factors in sound film production will
result in marked improvement of the product. It is in the nature of
things that technicians not wholly mature in their work should try to
establish taboos and conditions for the guidance of co-workers not
yet initiated into the deep mysteries of technical "expertness;"
for it is by supposed knowledge of these taboos and conditions that
"expertness" is established.
Just now, production is beginning to settle down to routine, and all
experts are breathing easier, feeling safe in the many tricks and
expedients that they have used in producing the relatively satis-
factory results now being secured. But not all these tricks are neces-
sary or even desirable. It is well to keep the art still in a plastic
state and not let some of these mistakes harden into the traditions of
production. The silent film industry suffered much from traditional
wrong approaches to some of its problems, although the industry as a
whole was never aware of it. The worship of false gods is difficult to
abandon in periods of prosperity; and the industry, if not careful, is
likely to expend millions on incorrect production methods, although
it will doubtless continue to prosper.
The evidence seems to indicate that much originally accepted as
authentic practice in the field of microphone placing, monitoring,
mixing, recorder operation, and laboratory procedure is actually
diametrically opposed to the most efficient practice. Fortunately,
the indicated changes are nearly all in the direction of greater simpli-
fication and greater flexibility.
There is probably more "hokum" practiced by the man at the mix-
ing panel than by any other talking picture artisan. The old-line
film man has felt himself helpless before the onslaught of the electrical
and recording technicians and has permitted a great deal of guess
work to pass as "art."
In some ways it is unfortunate that the radio industry supplied
most of the sound experts to the film industry. In radio broadcasting
it usually is desirable to present all sounds as coming from approxi-
mately the same plane that of the microphone. And so levels are
raised and lowered to bring all sounds out at approximately the
174 JOE W. COFFMAN [J. S. M. P. E.
same volume, the microphone being placed as near as possible to
the sources of sound.
But in talking picture presentations, it is very desirable to achieve
space effects, and dramatic variation of volume level. The monitor
operators are realizing this to some extent, but the old habits die hard.
It is difficult to resist the tendency to place microphones all over the
set, to switch from one to another, and to twist the dials which vary
the volume levels.
At the present time, the ideal condition is not always possible to
achieve because of technical considerations, but it seems unques-
tionable that eventually the first rule of successful dramatic recording
will be: "Use one microphone, in the general vicinity of the apparent
camera location; rehearse the scene to determine the highest per-
missible level; set the dials, and forget them." Not all sound men
will agree with this statement, yet its validity can be demonstrated
readily. It is believed that general application of this rule would do
more than any other one thing to free the talking picture from its
present characteristic stiffness.
The general tendency in all the studios seems to be to permit mixers
to follow their own judgment, and their judgment is not universally
good. This probably is a good policy in the long run, for it does
permit of experimentation, and the poor mixer will eventually elimi-
nate himself. However, it also encourages a tendency toward "arti-
ness" on the monitor's part, and to develop the belief that there is
some magic in the twisting of the dials that is beyond the grasp of
ordinary men. As a general rule, it may be said that the best mixer
is he who does the least mixing, and the best microphone placer is he
who places the fewest number of microphones.
At the time the industry's new sound stages were designed, they
undoubtedly reflected the most advanced production practice. But
it should not be forgotten that production practice at that time was
based largely upon laboratory experience in recording sound, per-
fection being achieved when the graphic curve representing the result
fell exactly in its theoretically perfect position. Perfection in sound
picture production, however, should be measured in terms of audience
reaction, and includes many things not considered in mere sound
recording. A monotonous voice, repeating, "I eat pea soup at six-
fifteen" may make a perfect sound recording, but it will not bring in
money at the box office.
The large monitoring rooms included in nearly all the stages are
Feb., 1930] ART AND SCIENCE IN SOUND FlLM 175
probably of some assistance in determining correct microphone
placement, and they confer dignity and a sense of ease upon the
mixer's calling, but it is very doubtful whether they justify their cost.
In the first place, they do not, as originally supposed, duplicate
acoustic conditions in the average theater. It is now apparent that,
from the acoustic standpoint, there is no average theater. Theaters
differ very widely in reverberation time and in all other acoustic
factors. The same theater has very different characteristics when
half full from those which it has when completely occupied. And it
becomes every day more obvious that an auditor unconsciously per-
ceives and adapts his mental response to the acoustic conditions pre-
vailing at the moment. It has also become obvious that the mixer
or monitor operator soon develops a factor of judgment under any
given circumstances, so that it is practically as easy for him to deter-
mine good quality in one size room as in another.
The fixed monitoring room, by removing control of the voice cur-
rents far from the scene of action, tends toward lessening directorial
authority, and toward difficulty in general coordination. If the
mixer is to see the action clearly, it forces an inflexible placement of
sets on the stage, and difficulties in the location of camera booths,
lights, "props," and other stage paraphernalia.
In view of these facts, it would appear that the best immediate
solution of the monitoring problem is the small portable monitoring
room, about ten by twelve by eight feet in size. Monitoring with
head-phones, as practiced on many improvised stages, presents
difficulties in that the best phones now available are not equal in
quality to the usual loud-speakers, unless used with rubber ear muffs
and transformers of proper impedance. At best, the head-phones
are uncomfortable. However, it is understood that head-phones of
excellent reproducing characteristics will soon become available, and
it is probable that some form of helmet will be devised which will
permit of comfort to the wearer and efficient connection to the ear.
It is believed that this arrangement, with portable mixing panel
trucks of the type devised for use on some improvised Hollywood
stages, would be by far the most flexible system for monitoring, and
would make it possible to develop that really close coordination of
sound and scene without which all claims to art are merely presump-
tuous.
There is some confusion in the use of the terms "sound proofing"
and "acoustic treatment." "Sound proofing" is accepted by acoustic
176 JOE W. COFFMAN [j. s. M. P. E.
authorities to mean insulation against external sounds; while "acous-
tic treatment" refers to control of internal reverberation, etc., by the
use of sound absorbing or other materials having the desired acoustic
characteristics .
The complete sound proofing of sound stages is undoubtedly wise,
although the result probably might have been attained less ex-
pensively than was the case with many new stages. The set must, of
course, be acoustically independent of all noises not purposely origi-
nated thereon. Failure to make this provision is expensive.
At present it is doubtful whether the ultimate sound stage con-
struction will include permanent acoustic deadening of the interior.
In the first place, no sound-absorbing material used for this purpose
absorbs all frequencies equally. Unfortunately, most "deadening"
materials do what the term signifies, that is, they absorb most of the
high frequencies which give life and brilliance to sound, and reflect
much of the low frequency component which creates "boominess."
The natural responses of the recording and reproducing equipment
also tend to suppress the higher frequencies, so that this effect is
doubly undesirable. A "dead" stage tends to create false security
on the part of the personnel of the sound department, making it feel
that no particular attention to the acoustic characteristics of the set
is necessary. On a dead stage, with absorbing materials used for set
construction, the recording inevitably lacks life and brilliance unless
the microphones are placed very close to the sources of sound, so as to
pick up nearly all their sound energy from the direct wave. This
technic, while it may result in technically good recording, will cause
all voices to seem to come from the same plane and thus destroy the
effect of spatial depth, so necessary for dramatic effect.
It would seem best to develop a system whereby each set is treated
as a separate acoustic unit, and is completely isolated in a space only
large enough for the necessary work to go on.
Normally, sets should be constructed from materials which would
be used in the actual scene being represented. Some resonance is
natural in any actual scene, and should be present in that scene as
recorded. It is true that this technic makes the placing of the micro-
phone more difficult, because the microphone picks up the sound as
would a single ear, and therefore may demonstrate undesirable se-
lectivity as regards the reflected sound. However, a suitable position
may usually be found by listening at various possible locations with
one ear closed, and this expedient will usually save much time.
I Feb., 1930] ART AND SCIENCE IN SOUND KlLM 177
It is believed that ultimate sound stage design will call for a rela-
tively large stage floor, sound proofed as regards external sounds, but
untreated on the interior. On this floor the sets will be built, prac-
tically following the old silent film procedure. When the set is
complete, with lights and properties in place, acoustic "flats" will be
used to build up a complete wall around it. If monitoring or camera
booths be used, their fronts can be incorporated in this wall at any
desired locations. This arrangement should have many advantages
over any now in use, and is recommended for experimentation.
Friction between directors and engineers developed early in sound
picture history, with the engineers eager to establish themselves in a
position of strong authority, and with the directors resisting en-
croachment on their traditional position. The noise of battle has
now subsided somewhat, with the advantage going in various direc-
tions in the different studios.
It is strongly believed that authority on the set should be centered
in one person, and that person should be the director. Engineering
qualifications can never be substituted for dramatic perception, nor
science for showmanship.
The average director of today is working in an unfamiliar medium,
and he needs much technical assistance. If he is wise, he will listen
to all the technical advice that is offered, make sure that he under-
stands the point involved, and then make his own decision, which
should be final. If his decisions are ill advised, the results will show
it, and he will soon improve the quality of his decisions, or look for
employment elsewhere.
Eventually, a new type of director will be evolved, who under-
stands his microphone placing as well as his camera angles, and who
has an ear as well as an eye. The sound man's relative position is
similar to that of the cameraman, which, of course, makes his position
still one of large responsibility.
As previously pointed out, there is nothing particularly mysterious
in the art of microphone placing. The director is usually nearly as
well qualified as the "mixer" to judge it. He can readily learn the
trick of listening to the sound with one ear, and so determine for him-
self the relative merit of various possible microphone locations. He
should particularly train himself to judge depth or space effects, which
are essentially dramatic, and are very often ignored by the mixer,
who is too frequently listening only for a technically perfect reproduc-
tion of the sound as he hears it close up.
178 JOE W. COFFMAN [J. S. M. P. E.
A pair of head-phones connected into the monitoring circuit, and
worn by the director during rehearsal and "shooting" of the- scene
frequently proves of much assistance in determining production values
and his efficiency is greatly increased by a complete signalling system
for his use, placing at his fingertips control of every possible produc-
tion factor.
Arbitrariness is, of course, not a desirable quality in a director, and
these remarks are not intended to approve that frequently observed
fault. But it is believed that much of the rigidity to be observed on
the talking screen of today is due to too scrupulous attention to the
sound man's advice upon the part of the director. Unless he under-
stands for himself the limitations and capacities of his medium, no
director can put much dramatic meaning into his work.
It is sincerely believed that utilization of the possibilities offered
by dubbing is of supreme importance to the advancement of the art
of talking picture production. It has long been recognized that a
silent picture is made or marred in the cutting room similarly, in
the not distant future it will be generally admitted that a talking
picture is made or marred in the dubbing room. The emphasis on
this last statement will be far stronger than ever was placed on the
former. It is probable that within a year no original sound records
will be used for the making of release prints of feature productions
of high quality.
By proper dubbing, it is possible to raise or lower volume levels so
that an entire production can be run without change of the projection
room fader setting, except in case of extremely loud noises such as
artillery fire. This possibility alone would make dubbing worth
while, for the greatest popular complaint against sound pictures now
is that the volume levels are unsatisfactory and are continually
changing. Dubbing places the relationship between volumes in the
control of the producer, and prevents the necessity for manipulation
of volume by the projectionist. Dubbing also makes it possible to
record all sounds at the most practical level, since the volume rela-
tionship is established in the dubbing room. It makes possible those
fine touches by the director which have previously marked the best
stage productions touches which are not possible until the produc-
tion can be viewed as a whole. It makes acoustic cutting even more
flexible than pictorial cutting; it makes possible the improvement of
voices and effects through changing their frequency content by use of
the requisite filters; it permits almost any imaginable acoustic trick,
Feb., 1930] ART AND SCIENCE IN SOUND FlLM 179
and the inclusion of effects which occur as afterthoughts; and it
insures the valuable original negative against the damage it always
incurs in the printing room.
It is believed that equipment for dubbing will be vastly improved
during the coming year, and that development will be hastened by
efficient use of the equipment now available. It is probable that the
ultimate dubbing machine will bear no resemblance to the dummy
projectors now being used, but will consist of an associated group of
sound pick-ups mounted on a panel, with faders, filters, amplifiers,
etc., arranged for easy connection thereto. A device somewhat like
the present printer light-shift, actuated by notches in the film, will
determine which particular records are to be picked up at any given
time. Fader settings and filters can be similarly cut in. If the
driving motor is capable of being interlocked with a picture projector,
it will be possible to determine by projection exactly the effects to be
secured on the dubbed record. These effects can be decided upon by
the picture director, the editor, or by conference, before any actual
re-recording is undertaken.
Seven million Americans walked up to motion picture theater box
offices yesterday, and paid the price of admission. Today, and each
tomorrow, holds the prospect of similar parades. But they enter
those doors not for the purpose of seeing realistic presentations of
their own lives they seek relief from reality. But the presentations
must be masked to pass for reality, upon the acceptance of the prem-
ises laid down by author, actor, and producer. The more sophisti-
cated the mind of the viewer, the greater the task becomes, for the
practiced eye detects the sham behind the mask, unless art has func-
tioned well indeed.
PHOTOGRAPHIC CHARACTERISTICS OF SOUND
RECORDING FILM*
LOYD A. JONES AND OTTO SANDVIK
The various methods and general principles involved in the re-
cording of sound by photographic methods are too well known to
require detailed description and discussion. The methods at present
in use commercially may be divided broadly into two classes: (l) The
variable density type, and (2) the variable width type. The former
may be subdivided, with respect to the method used for obtaining
the variable exposure, into (a) those using the "light valve," and
(b) those employing a "flashing lamp." In variable width recording
the film is moved at a uniform linear velocity past a slit, or an optical
image thereof. By suitable means the transverse length of this slit
image is so modulated that the exposed area varies in lateral dimen-
sions giving a sound record of the so-called "saw tooth" type. At any
point within the exposed area the exposure incident on the photo-
graphic material is constant, both factors of exposure, namely, in-
tensity (I) and time (t), being constant. This statement requires
some modification since with the film moving continuously in one
direction past a slit of finite width and the boundary of the illuminated
area moving in a direction perpendicular to that of the film there must
be a narrow envelop in which the t factor of exposure varies to some
extent.
In variable density recording with the light valve the film is moved
at a constant linear velocity past an illuminated slit, or an optical
image thereof, the width of which is modulated. In this case it is
evident that the intensity factor (/) of exposure is constant, while the
time factor (t) is variable. In variable density recording with the
flashing lamp the film is moved at a constant linear velocity past an
illuminated slit of fixed width, the intensity of the illumination being
modulated. In this case it is evident that the exposure at any point
on the photographic film is variable due to the variation in the inten-
* Communication No. 414 from the Kodak Research Laboratories.
180
CHARACTERISTICS OP SOUND FILM 181
sity factor of exposure. From the photographic standpoint, there-
fore, the general problem of Sound recording has at least three dis-
tinct phases, since, if the best possible results are to be obtained,
each of the methods mentioned above requires a photographic mate-
rial having characteristics and requiring processing treatments differ-
ing radically from each of the other two.
Regardless of which method of sound recording is being used, the
energy required for modulating the photographic record is derived
from the plate current flowing from the last tube in the recorder
amplifier. In all cases it is desired that the sound record positive,
printed from the sound negative, shall carry a distribution of density
which will control the intensity of the radiation incident upon the
photo-electric cell of the reproducing mechanism in such a manner
that the instantaneous intensity of this radiation is directly pro-
portional to the instantaneous sound pressure on the microphone
diaphragm.
In case of the variable density record this end is accomplished by a
variation of density from point to point along the length, that is, in
the direction of travel, of the record, with no variation of density in
the transverse direction, that is, along a line perpendicular to the
direction of travel. When such a record is moved at a uniform linear
velocity past the scanning slit, or the optical image thereof, the in-
tensity of the radiation transmitted by this slit is directly proportional
to the mean transmission of the photographic image covering the
slit at any instant. It is evident, therefore, that if it be desired to
cause the intensity incident upon the photo-electric cell to vary, let us
say, according to a sine function of time, the transmission of the
photographic image must vary as a sine function of distance measured
along the length of the record. A micro-photometric analysis of such
a record should therefore show a gradual increase and decrease in
transmission along the length of the record which, when plotted as a
function of linear displacement, should give a sine curve. Assuming
that the characteristic of the recording system (microphone, amplifier,
light valve, etc.) is linear, the exposure (I.t) incident on any point of
the photographic recording material is directly proportional to the
instantaneous sound pressure on the microphone. If this condition
is fulfilled then the photographic problem resolves itself into that of
obtaining a positive in which the distribution of transmission along
the direction of travel is directly proportional to the distribution of
exposure on the negative. This problem is fundamentally identical,
182
LOYD A. JONES AND OTTO SANDVIK [j. s. M. P. K.
in principle at least, with the usual photographic problems involved
in the production of motion pictures, portraits, landscapes, etc., and,
in fact, in all cases where the correct reproduction of a series of vari-
FIG. 1. Sensitometric curves for motion picture positive developed in metol
hydroquinone borax.
able brightnesses is of prime importance. In motion picture photog-
raphy, for instance, the camera man builds up in the studio a series of
brightnesses spacially distributed. Photographic methods are then
called upon to produce in the positive a series of brightnesses directly
Feb., 1930] CHARACTERISTICS OF SOUND FILM 183
proportional to those existing in the set. By means of a lens an
image of the object in question is formed on the photographic ma-
terial. The exposure time for all points on the negative area is the
same and hence the distribution of brightnesses existing in the object
produces a corresponding distribution of exposure at various points on
the negative surface which are directly proportional to the bright-
nesses existing in the object. In the case of sound recording an
analogous situation occurs since the light valve or "flashing lamp"
subjects the negative to a series of variable exposures. In the case of
picture records and sound records the desirable condition from this
point on is a reproduction in the positive of transmission values which
are directly proportional to the exposure values incident upon the
negative record.
The theory of tone reproduction, applying particularly to general
photographic work, has been treated at length in previous publications
and the general laws and relationships derived can be applied with
certain modifications in details, which may be desirable for the sake
of convenience, to the general problem of photographic sound repro-
duction. For instance, it has been shown that for perfect reproduc-
tion of brightness relationships, the product of the negative gamma
(TW) by the positive gamma (7^) should be equal to unity, assuming
that only the straight line portions of each of the characteristic curves
are used. This law is of equal validity in the case of sound reproduc-
tion by the variable density method.
In the case of sound on film, the positive sound record must be
developed along with the picture positive and hence must necessarily
receive the same development treatment, thus being developed to the
same contrast (7) as that required to give the desired picture quality.
The present predominant practice in the making of motion pictures
involves the use of a picture negative developed to a relatively low
gamma (0.5 to 0.6), thus requiring for the fulfillment of the above
relationship that the positive be developed to a relatively high gamma
(1.8 to 2.2). A fair approximation to practice is represented by the
following figures:
Tw = 0.55
7p = 2.00
7.7> = 1.10 = 7r
t will be noted that the product of these negative and positive gam-
mas is slightly greater than unity. It has been found that this is
184 LOYD A. JONES AND OTTO SANDVIK [j. s. M. P. K.
desirable in order to compensate for certain contrast losses which
occur at different points in the process. For instance, a certain
amount of flare may exist in the projection lens, thus spreading a
veiling glare over the projected image. In many cases also there is an
appreciable amount of stray light incident upon the screen from the
general lighting in the theater. These factors all tend to decrease the
effective contrast and it seems desirable to make the gamma of the
reproduction (7,.), the so-called "over-all gamma," somewhat greater
than unity. Since the sound positive must be developed to a gamma
of approximately 2.0, it follows that the sound negative should be
developed to a gamma of 0.5 or 0.6 in order that the required quality
of exposure variations to which the sound negative is subjected can
be reproduced in the sound positive as proportional variations in:
transmission.
In establishing a laboratory technic for the handling of sound rec-
ords it is therefore necessary to determine the development condi-
tions which will result in a sound record negative of the desired con-
trast. The required information can be derived from a sensitometric
study of the characteristics of the photographic material. In Fig. 1
are shown the sensitometric curves for motion picture positive film,
the material which is used almost exclusively in making the sound
record when using the light valve method. These curves show the
relationship between density (ordinates) and log exposure (abscissas)
for a series of different development times. The exposures from
which the data are derived were made in a high intensity sensitometer
employing a time scale exposing system, the time factors of exposure
varying from 2.5 X 10 ~ 4 to 0.5 seconds. The light source used in this
sensitometer is a high efficiency tungsten lamp with the filament
operating at a color temperature of approximately 3100K. The
exposed strips were developed in the standard metol hydroquinone
borax formula at 20 C. The resultant densities were read with the
emulsion side of the film in contact with an illuminated disk of pot
opal glass. The values obtained are therefore those of diffuse density.
The times of development used in obtaining the various curves are
shown in the first column* of Table I.
In the upper left-hand corner of Fig. 1 are plotted the time (of
development) -gamma and the time-fog curves for this material. The
time-gamma curve obtained by plotting gamma as a function of
development time shows the way in which gamma increases with in-
creasing times of development.
Feb., 1930]
CHARACTERISTICS OF SOUND FILM
185
TABLE I
Sensitometric Data for Motion Picture Positive Developed in M. Q. Borax
T d
t
i
d y
dT d
L
R.P.
Fog
2.5
0.32
T.90
1.90
2.9 +
81.0
0.01
4.5
0.64
T.62
1.43
2.9
80
0.02
8.0
1.03
1.10
0.93
2.0
78
0.03
12.0
1.30
1.02
0.66
1.8
76
0.04
20.0
1.60
2.96
0.17
1.6
75
0.05
4.2
0.60
1.66
1.48
3.1
80
0.02
In Table I various data derived from the curves in Fig. 1 are given.
The significance of the various symbols used as column headings are
as follows:
T d denotes the development time in minutes.
7 is defined as -the slope of the straight line portion of the charac-
teristic curve.
i (inertia) is expressed in terms of visual candle-meter seconds, the
radiation quality (spectral composition) being that emitted by a high
efficiency tungsten lamp operated at a color temperature of approxi-
mately 3100K. Inertia is defined as the value of exposure (I.i)
at the point where the straight line portion of the D-log E curve
extended cuts the log E axis.
-r^r- denotes the rate of change of gamma with development time
Ct J. d
and is defined as the slope of the y-t curve at the point corresponding
to the specified development time. This value is useful as a measure
of how rapidly gamma is changing at any instant and can be used to
compute the variation in development time corresponding to any
specified tolerable variation in gamma.
L (latitude) denotes length of the straight line portion of the
characteristic curve and is measured in terms of the projection of this
straight line upon the log E axis. The value is expressed in log ex-
posure units. It will be noted from an inspection of the curves in
Fig. 1, and also in the succeeding figures, that the actual length of the
straight line portion tends to remain approximately constant for all
development times; but since latitude (more properly referred to as
exposure latitude) is measured as the projection of this line on the log
E axis, the value decreases for increasing gammas. This value is a
186
LOYD A. JONES AND OTTO SANDVIK [j. s. M. p. E.
direct measure of the exposure range over which direct proportion-
ality between log exposure and density exists.
The value of R.P. (resolving power) is not derived from the curves
shown in Fig. 1 but from measurements of an entirely different
nature. Since, however, this value is of great importance in sound
reproduction, it is included in this table. The value of resolving
power given in this case is that resulting from the use of a high contrast
test object and the optimal exposure value. It will be noted that this
value of resolving power tends to decrease slightly for prolonged
development. The entire problem of resolving power and its de-
pendence on contrast, exposure, development, etc., is extremely com-
plicated and is treated at greater length in a later section of this paper.
The heading "Fog" denotes the value of density produced on a
portion of the photographic material which has received no exposure
but which has been subjected to development for the times indicated.
TABUS II
Sensitometric Data for Reprotone B Developed in M. Q. Borax
Td
7
i
dy
dTd
L
R.P.
2.0
0.25
T.77
1.28
2.9 +
90
4.0
0.47
T.60
0.89
2.9
85
8.0
0.73
1.43
0.50
2.5
78
12.0
0.87
T.40
0.29
2.0
74
20.0
1.00
1.31
0.11
1.9
72
5.6
0.60
1.52
0.65
2.8
81
At the bottom of the table are given the interpolated values for the
various factors corresponding to the development time yielding a
gamma of 0.6. As stated previously, present practice demands that
the sound record negative be developed to a gamma of approximately
0.6 and the values as indicated in the bottom line of the table therefore
give definite information as to the characteristics of the material
when developed to this extent. It should be kept in mind, however,
that the data shown in the various tables and figures in this paper
represent the average derived from tests made on several different
coatings of the various materials. There are some unavoidable
variations in characteristics from batch to batch in any photographic
material. These are relatively small but it should be remembered
that a single set of measurements made on one particular sample of
material may not check precisely with the values given here.
Feb., 1930] CHARACTERISTICS OF SOUND FlUVf 187
In Fig. 2 and Table II are given data relative to the characteristics
of Reprotone B film, a material developed particularly for use in
sound recording by the light valve method. The characteristics of
this material are very similar to those of motion picture positive with
the exception of rate of development and the maximum attainable
contrast (y a ). An inspection of the time-gamma curve in Fig. 2
will show that it rises much less steeply and obtains an ultimate value
REPROTONE.
PEVEUDPER f\Q
PEVELOPMENT
VN MINUTE!,
TIME
LOG EXPOSURE
3.0
1.0
1.0
2.0
4.0
FIG. 2. Sensitometric curves for Reprotone B developed in metol hydroquinone
borax.
appreciably lower than that for the regular motion picture positive
film. It is considered that this represents a desirable factor in ma-
terial for this purpose. As stated previously, it is necessary to stop
development when gamma reaches approximately 0.6. In the case of
positive film the rate of change of gamma with time of development
at this point as represented by the d y /dT d is 1.48, while for the Re-
protone B material the value of this factor for the same contrast is
only 0.65. This means that at the time when it is desired to stop
188
LOYD A. JONES AND OTTO SANDVIK [j. s. M. P. E.
development the value of gamma in the case of the Reprotone is
changing much less rapidly, hence a much greater error in time of
development can be allowed without introducing an intolerable vari-
ation in the value of negative gamma. The latitude for a gamma of
0.6 is 2.9, practically the same as that of the positive material and
amply sufficient to accommodate the maximum desirable exposure
variation in recording.
The general requirements imposed upon the photographic material
for use with the "flashing lamp" are practically identical with those
FIG. 3. Sensitometric curves for motion picture par speed negative (ortho)
developed in metol hydroquinone borax.
TABUS III
Sensitometric Data for Par Speed Motion Picture Negative Developed in M. Q.
Borax
Td
y
i
dj
Wl
L
R.P.
Fog
2.5
0.20
1.58
2.5
3.2 +
55
0.04
4.5
0.58
1.42
1.4
3.2
55
0.04
8.0
0.92
T.24
0.72
2.5
40
0.05
12.0
1.14
1.20
0.45
2.2
40
0.08
20.0
1.34
2.96
0.14
2.2
35
0.12
4.7
0.60
T.40
1.30
3.1
54
0.04
CHARACTERISTICS OF SOUND FILM
189
Feb., 1930]
I
required by the light valve method, with the exception of speed.
The photographic intensity of the radiation emitted by the "flashing
lamp" is not in general sufficiently great to give fully exposed negatives
when using positive motion picture film. For this type of recording,
therefore, it is common practice to use regular negative materials.
CINE. PKNCHROHAJVC TYPE. 2.
PEVE.LOPER MO.. fcORAX
fc 6 \0 It 14- Ifo 16 CO
PEVE.l-OPME.NT
TIME, IN M\NVJTE,a
LOO EXPO SURE.
4.0
1.0
1.0 Z.O 3.0 4.0
FIG. 4. Sensitometric curves for motion picture panchromatic negative Type 2
developed in metol hydroquinone borax.
In Fig. 3 and Table III are given the data relative to regular par speed
motion picture negative film developed in standard metol hydro-
quinone borax. The factors tabulated are identical with those shown
in the previous cases. In the bottom line of the table are the values
applying to the materials when developed to a gamma of 0.6.
In Fig. 4 and Table IV are the corresponding data for motion pic-
190
LOYD A. JONES AND OTTO SANDVIK [j. s. M. P. E.
ture panchromatic Type 2 film developed in the standard metol hydro-
quinone borax formula. The most noticeable difference between
these two materials from the standpoint of sound recording is the
relatively low rate at which gamma increases with time in the case of
the panchromatic film as compared with the par speed (orthochro-
matic). The rate at which contrast is changing at the point where
TABLE IV
Sensitometric Data for Motion Picture Panchromatic Type 2 Developed in M. Q.
Borax
Td
7
1
dy
dTd
L
R.P.
Fog
2.0
1.00
50
0.04
4.0
0.32
2.74
0.80
3.3 +
46
0.07
8.0
0.58
2.33
0.50
3.3
44
0.12
12.0
0.77
2.28
0.37
3.1
42
0.15
20.0
0.96
2.17
0.17
2.7
41
0.19
8.3
0.60
2.32
0.48
3.2
44
0.13
gamma becomes equal to 0.6 is appreciably less in the case of the
panchromatic material. It should be easier, therefore, to control
contrast with the desired precision in the case of the panchromatic
material. The speed of the panchromatic as indicated by the value
of inertia is also much greater.
The general requirements imposed upon a photographic material
for variable width recording are radically different from those de-
manded by the variable density methods. Here the problem is more
analogous to that met in process work, such as the reproduction of a
line (black and white) drawing. One portion of the sound track area
should be covered by a silver deposit which is opaque, or at least very
dense, while the other should receive so little exposure as to remain
almost completely transparent. In other words, a very high contrast
between the two areas is desired. Practical experience indicates that
a density difference of from 1.3 to 1.6 (corresponding to transmission
ratios of 20 and 40, respectively) is sufficient. The boundary line
between the two areas should be as sharp as possible and obviously
the resolving power of the material should be high. The regular
motion picture positive film when developed in the formula commonly
used for picture work (formula D-16) meets these requirements ad-
mirably and is the material at present in general use for variable
density recording.
I
Feb., 1930]
CHARACTERISTICS OF SOUND FILM
191
In Fig. 5 and Table V are given the sensitometric data relative to
this material. It will be noted that gamma rises very rapidly with
time of development reaching a value of 2.0 in six minutes. In this
type of recording the latitude of the material is of little importance,
- \.o
FIG. 5.
1.0 ZO 3.0 4.0
Sensitometric curves for motion picture positive developed in D-16.
nor is the usual method of expressing sensitivity in terms of inertia of
practical utility. If we assume that a density of 1.5 in the exposed
portion of the sound track negative is adequate (and practical ex-
perience supports the validity of this assumption), then it seems more
192
LOYD A. JONES AND OTTO SANDVIK [j. s. M. P. E.
logical to express the effective speed of the material in terms of the
exposure required to give this density. In the third column of the
table (log E 1.5) are given values of the exposure required at the vari-
ous development times to produce this arbitrarily assumed density
(1.5).
EXPERIMENTAL EMULSION
PEVELOPER t*VP. Ifc
- 1.0
1.0 Z.O 30 4.0
FIG. 6. Sensitometric curves for an experimental emulsion developed in D-16.
In Fig. 6 and Table VI are given some interesting data relative to a
special experimental material not at present commercially available.
This is a material of extremely high contrast and should be par-
ticularly adapted to the variable area sound recording. From a
standpoint of contrast, resolving power, and sharpness it offers con-
Feb., 1930]
CHARACTERISTICS OF SOUND FILM
193
TABLE V
Sensitometric Data for Motion Picture Positive. Developed in D-16
Td
7
Log Ei. 5
Fog
R.P.
2.5
1.02
1.18
0.04
74
5.0
1.81
0.40
0.05
73
8.0
2.28
0.07
0.06
71
12.0
2.48
1.93
0.07
71
6.0
2.00
0.22
0.05
72
siderable promise, but further experimental work must be done before
definite conclusions as to its utility and practical value can be drawn.
As stated previously, the photographic process is concerned with
two factors, namely, the rendering of tone and the reproduction of
form. The former depends on the sensitometric characteristics of the
emulsion, whereas the latter depends primarily on its resolving power
and sharpness. This distinction is only partial, however, because
those factors obviously affect the tone values; furthermore the
properties of an emulsion which determine its sensitometric character-
TABUS VI
Sensitometric Data for an Experimental Emulsion. Developed in D-16
Td
7
Log EJ.&
Fog
R.P.
2.0
3.6
0.10
0.02
120
4.0
4.0
0.00
0.02
117
6.0
4.7
1.80
0.02
114
8.0
5.7
1.70
0.03
112
12.0
6.0
1.50
0.03
98
4.0
4.0
0.00
0.02
117
istics also determine largely its resolution and sharpness. The nature
of the problem should necessarily determine the type of emulsion to
be used. Thus in the case of sound recording, where high frequencies
consist of photographic images very close together, it is necessary to
use an emulsion which has high resolution ; yet it must be sufficiently
sensitive to attain the required density with the exposure available.
Unfortunately, these two factors bear in general a reciprocal relation.
The resolving power of an emulsion is an extremely complex prob-
lem depending on a number of variables such as distribution of in-
tensity and contrast in the object, density of the photographic image,
194 LOYD A. JONES AND OTTO SANDVIK [j. s. M. p. E.
time of development, type of developer, quality (spectral composition)
of the exposing radiation, and several other minor factors. It is
impossible, therefore, with our present knowledge at least, to express
the resolving power of an emulsion in terms such that one can calcu-
late very closely the depression in volume of a sound record incurred
by imperfect resolution. It may prove useful, however, to consider
the nature and the effect of some of the above variables. In order to
simplify the problem as much as possible, we shall consider each
variable separately.
Let us consider first the effect of a change in the image density,
keeping all other factors as nearly constant as possible. Fig. 7 shows
FIG. 7. Resolving power-image density curve for motion picture positive de-
veloped 8 minutes in D-16.
a typical curve for cine positive, the object contrast being 1000 and
the development time 8 minutes in D-16. This curve shows that the
resolution increases from zero at a density of zero to a maximum value
of 80 at an image density of 1.3. This density we shall call the opti-
mal density. The general character of this curve is similar for any
type of emulsion, although in general the lower the inherent contrast
of the emulsion, the lower is the optimal density. Keeping the time
of development constant and varying the object contrast, if we
measure maximum resolving power, that is, resolving power at opti-
mal image density, we obtain the curve B, shown in Fig. 8. The
resolution increases exponentially with the log contrast approaching
its maximum value asymptotically. It is seen that cine positive
Feb., 1930] CHARACTERISTICS OP SOUND FlI^M 195
emulsion very nearly reaches its maximum value when the object
contrast is 3.0. If we now vary the time of development, keep the
object contrast 1000, and determine the resolving power for each
time of development at an image density of 0.3, we obtain the curve
shown in Fig. 9. It is interesting in this case to note the rapid
decrease in resolution with increasing time of development. This is
due to the fact that the optimal density is greater than 0.3 and that
the entire curve shifts to the right as the time of development in-
creases, thus depressing the low density end. If the image density
and the development time both vary, we obtain a family of curves;
A-RE.PROTONE B
, 00 |_ B- ONE: POSITIVE
jjj S.B. BORftX 17E.VEL.OPER
g
60
1
20
LOO CONTRAST
1.0 2.0 VO
? IG. 8. Resolving power-object contrast curves for motion picture positive (B)
and Reprotone B (A) developed in metol hydroquinone borax.
and if the object contrast varies as well, the resolving power is repre-
sented by a family of complicated surfaces.
So far we have considered only one type of emulsion, namely, mo-
tion picture positive. Reprotone B is of the same general type and
its resolving power as a function of image density is represented by
curves similar to that shown in Fig. 7. Referring again to Fig. 8, it
will be seen that the resolving power-log contrast curve for Reprotone
B (curve A) crosses the same curve for motion picture positive (curve
B) at a log contrast value of 0.5 corresponding to a contrast value of
3.2. For contrast ratios less than 1 to 3.2, therefore, the resolving
196 LOYD A. JONES AND OTTO SANDVIK [J. S. M. P. K.
power for Reprotone B is slightly lower than motion picture positive.
For values of contrast greater than 1 to 3.2, however, the resolving
power of Reprotone B is markedly greater than that of motion picture
positive. The effective contrast in sound recording is a function of
the modulation of exposure and the amount of scattered light present
due to lens aberrations, lens flare, dirty lens surfaces, etc. It is diffi-
cult to determine the mean effective contrast existing under practical
ONE: POSITIVE:
S.B. B>OR*X PEVELOPER.
60
<bO
40
TIME. OF DEVELOPMENT IN MINUTES
4 8 IZ. Ifc
FIG. 9. Resolving power-time of development curves for motion picture positive
for an image density of 0.30, developed in metol hydroquinone borax.
sound recording conditions. It seems almost certain, however, that
with a high quality optical system in perfect adjustment the mean
effective contrast should be well above the 3.2 ratio and under such
conditions Reprotone B should be somewhat superior to motion
picture positive from the standpoint of resolving power.
We have seen above (Fig. 6) that the sensitometric characteristic
curve of the experimental, high contrast emulsion is quite different
from that of the motion picture positive. Likewise, the resolving
Feb., 1930]
CHARACTERISTICS OF SOUND FILM
197
100
80
60
EXPERIMENTM. E.MUU3VON
P-lfe OELVE.L.OPER
DENSITY
1.0 fc.O 3-O 4.0
FIG. 10. Resolving power-image density curves for the experimental emulsion.
Curve A is for 4 minutes' development and curve B for 12 minutes' development.
power-image density curve is quite different in character from the
corresponding curve of cine positive as shown in Fig. 10, the optimal
density of curve A representing 4 minutes' development and curve B
12 minutes' development, both being very high. This type of
emulsion is particularly well adapted for variable area recording.
A- EXPERIMENTAL.
B- CINE POSITIVE
O-\fc PEVEUOPER,
EMUL.SION
LOG CONTRfcST
1.0
0.0
Resolving power-object contrast curves for 04) experimental emulsion,
(B) motion picture positive developed in D-16.
198
LOYD A. JONES AND OTTO SANDVIK [j. s. M. p. E.
First, because of its high optimal density, the negative could be ex-
posed to a density of two to three, corresponding to a contrast of 100
to 1000, and we have seen in Fig. 8 that resolving power as a function
of contrast has nearly reached its maximum value at a contrast of 100.
VGOOO
V 5000
%=1000
FIG. 12. Micro-densographs of variable density sound records of several different
frequencies as shown.
On making a print, therefore, the loss in definition due to lack of
contrast would be small. Second, the density gradient at the image
edge or sharpness is high because of its high contrast, thus reducing
the shading effect at the boundary of the sound record to a minimum.
Feb., 1930]
CHARACTERISTICS OF SOUND FILM
199
In Fig. 11 it is seen that the experimental emulsion is definitely
superior to cine positive, especially at low contrast. It is true, in
general, that the resolution of an emulsion whose inherent contrast is
high, gives better definition at low object contrast than one whose
inherent contrast is low.
We conclude from the above consideration that to determine the
resolution obtainable in a given practical case requires an integration
of the effects due to these several variables. This is not possible,
FIG. 13.
A photomicrograph of a variable width sound record of an 8000 cycle
constant frequency.
with our present knowledge at least. It is probably a fair assumption
to make, however, that an emulsion having a maximum resolution of
80, when correctly used with a high quality optical system, will give
excellent rendering of tone and form at frequencies well above the
highest frequencies now used, and that the volume of those frequen-
cies will not be materially reduced due to lack of definition. As a
matter of fact it is possible to record frequencies of 13,000 to 15,000
and obtain excellent definition. In order to do so the adjustment of
200
LOYD A. JONES AND OTTO SANDVIK [j. s. M. p. E.
focus has to be carried out with the utmost care. A displacement of
the objective lens, imaging the slit on the film, by a small fraction of a
millimeter causes a change from excellent definition, that is, a high
modulation in the density, in one case, to a practically uniform density
in the other. In Fig. 12 are micro-densographs of variable density
sound records of several different constant frequencies as indicated.
These in themselves do not convey much information, but wave form
analyses and a study of the various types of distortions and their
15
10
LOO EXPOSURE.
1.5
3.0
FIG. 14.
Curve showing growth of diameter of the photographic
image with the log exposure.
causes will be the subject of a future communication and we shall not
devote any space to it in the present paper. Fig. 13 is a photomicro-
graph of a variable area sound record of 8000 cycle frequency. The
definition is not perfect, yet the volume depression at this frequency
from that cause certainly would not be very large.
The necessity for careful adjustment of the optical system in the
reproducer is also of great importance because a decentered filament
image on the slit causes a reduction in volume and introduces micro-
CHARACTERISTICS OF SOUND FILM
201
Feb., 1930]
I
phonic noises ; and a slightly out-of -focus slit image on the film causes
a depression in volume of the higher frequencies of as much as 10 to
15 decibels.
10 15 20 5
PIAMETER OF IMAGE. IN mm
* fc * k-
FIG. 15. The upper curve shows the contraction of a 4.5 mm.
image with the density of the photographic image. The lower
curve shows the contraction of an image as a function of the
diameter of the image.
We have referred to certain other factors which might affect the
structure of the photographic image, namely, growth of image with
exposure, contraction of image, mutual action of adjacent images, and
202
LOYD A. JONES AND OTTO SANDVIK [j. s. M. P. E.
certain edge effects the best known of which is the Eberhardt effect.
These phenomena are probably of more theoretical interest than
practical importance at the present time.
The growth of the diameter of an image with exposure is, of course,
a well known phenomenon, and has been used by the astronomer
for years as a method to determine stellar magnitudes. A typical
case of image growth is shown in Fig. 14 where the diameter of the
image is plotted as a function of the logarithm of the exposure. The
103
101
too
93
98
97
PENSHTY OF
I I I I
OZ 0.4 0.6 Ob 1.0 I/& 1.4 !.* I.& 210
FIG. 16. Curves showing the change in the size of an image as a function
of the image density. The family of curves represents 2, 4, 8, and 12
minutes' development, respectively, from left to right.
linearity between these quantities as shown is somewhat better than
that in the average case.
There is also a contraction of the image due probably to a tanning
action of the reaction products formed during development. The
absolute value of the amount of contraction depends on the size and
the density of the image as shown by the two curves in Fig. 15. The
upper curve shows the contraction with density of an image 4.5 mm.
in diameter, while the lower curve shows the contraction of the image
with its diameter for constant density. It is apparent from the lower
curve that the contraction is differential with the distance from the
Feb., 1930] CHARACTERISTICS OF SOUND FlLM 203
edge, being largest at the edge and becoming practically constant,
that is, no contraction, 5 mm. inside the edge.
In practice these two effects occur simultaneously. The actual
change in the image size depends both on the size of the optical image
and on the density of the photographic image. Thus for a very small
optical image, that is, of the order of magnitude of the one used in
obtaining the data represented by Fig. 14, the growth factor is large,
whereas the contraction factor is almost negligible. For an image
10 mm. in diameter, however, the reverse would be true, except in the
case of extreme over exposures. The combined effect of the two fac-
tors is shown in Fig. 16. This image was formed by a slit 0.99 mm.
wide placed in contact with the emulsion. The family of curves
represents 2, 4, 8, and 16 minutes' development, respectively, from
left to right. It is seen from these curves that for low exposures the
contraction factor predominates, whereas for higher exposures the
growth factor becomes predominant. Just how important these
factors are is a subject for further investigations.
DISCUSSION
MR. KEU/OGG: I should like to ask whether sharpness and resolution go to-
gether.
DR. SANDVIK: Sharpness and resolution do not necessarily go together. In
general, an emulsion which has high resolution also has high sharpness, but they
depend on different factors. Sharpness depends on the density gradient at the
edge of an image measured in the shadow. The slope of the straight line of the
curve is the sharpness, whereas resolving power depends on the slope, and shape
of shoulder and toe.
THE MODERN NEWS REEL
HARRY W. JONES*
Nineteen years ago the first news reel was issued. This grand-
daddy's children have kept pace with the balance of the motion
picture industry through its many stages of progress; never behind
and usually a few jumps ahead, finally becoming a national, even an
international, institution. It has. been and still is an important part
of every well presented theater program. But little credit is allotted
to it as an attraction, and yet it has a personal appeal to every theater
patron young or old. Primarily, because it covers every major event
in all activities and allows the eye to see those things of interest of
which one reads. It also brings to those not fortunate enough to
have traveled extensively, places and personages of international
fame, and to those who have traveled and seen for themselves it
revives many memories. To borrow the slogan of one of the oldest,
it "sees all, knows all."
The original news reel was issued weekly as compared to present
day activities of a reel a day. Subject matter differs but little, if any.
The real comparison is in the equipment used in its making. Con-
trast the news cameraman of a few years ago with his camera case
draped over one shoulder and his tripod across his back, with the
ultra-modern equipment of the modern news reel forces. When
something happened under the old system, if a cameraman was close
at hand he got his story, or perhaps the free lance saved the day or
else everyone lost sleep and temper trying to get someone on the spot.
Today fast mobile units are scattered throughout the country, always
ready for whatever may occur.
Many types of equipment have been developed for news gathering,
each having its special place and usage. May I ask your indulgence
at this point if I seem a little partial in my descriptions, but being a
member of RCA Photophone and having devoted the major portion
of the past year to its field recording equipment, I prefer to speak of
that with which I am most familiar.
* RCA Photophone News Service, New York City.
204
MODERN NEWS REEL 205
The first RCA Photophone news truck was designed for a dual
purpose, news reel work, and a rolling studio mostly the studio.
Trying to coax it into performing all the tricks a news cameraman
could think up was no sinecure. Two Bell and Howell cameras, two
variable area recorders, all four driven by synchronous motors,
necessitated power equipment of an unusual size, that is, heavy duty
storage batteries and a rotary converter. The necessary charging
equipment to keep the batteries in condition added to the weight.
Add to all this the recording amplifiers, microphones, etc., a motor
generator set for plate supply and you have a good idea of what we
were transporting. A few days' experience taught us the motor
generator set couldn't stand road shocks, so out it came in favor of
"B" batteries. Next we shed one camera and one recorder in the
interest of space. In this condition, a news reel a week was turned
out for nearly five months quite a record. This truck gave us our
first real test of the durability of our variable area recorders. Al-
though the recording machine was solidly mounted, to the best of my
knowledge a mirror has never been shaken from the suspension
strips by road shock. The optical system will stay in adjustment for
months at a time and the balance of the mechanism has needed little
servicing in spite of dirt, grit, and climatical changes.
A real test for an amplifier is to bounce it around a hundred miles or
so on choppy roads and find tubes and connections in usable condition
on arrival. And may I also add a good word here for the Bell and
Howell cameras.
A news cameraman's creed is ''get your story" and usually he does.
At all principal events provision is made for a camera stand, but the
microphone placement man is not always so fortunate and must use
dexterity, skill, and, many times, real ingenuity.
The advantages in two-machine recording systems for the news reel
are identical to their use for studio work and far overbalance the
additional equipment necessary for their operation.
For use in those places where a recording could not be made within
four or five hundred feet of a truck an equipment with portable ampli-
fier and power supply was next adapted to field work, and, within a
limited scope, proved satisfactory.
Later, trucks were built after the style of the modified first truck.
Then came a change; the trucks looked the same but things inside
were different. A new and better recorder replaced the old, ampli-
206 HARRY W. JONES [J. s. M. P. E.
fiers were simplified, a power take-off for battery charging was added
as was also an outside pick-up amplifier and mixer panel.
The power take-off added greatly to the mobility of the outfits in
that charging was done while the truck was en route, or on the scene
if necessary, thereby insuring a constant power supply. The outside
pick-up amplifier was an even greater improvement. By its use an
operator could take this portable equipment away from the truck to
the scenes of action and there monitor more advantageously on either
or all of the three microphone circuits available. By an intercom-
municating system the operator was in contact with both cameraman
and machine operator in the truck, and was often able to get worth-
while shots that might otherwise be missed where operation is solely
from within the truck.
The demand again came for lighter and more portable equipment
and this time the RCA Photophone laboratories produced a Mitchell
camera equipped with a variable area recorder built as an integral
part. A light amplifier accompanied the Mitchell and with only 6
volts for power supply the whole made a real portable outfit. The
equipment fits nicely in the new business body sedan of a light and
fast car, so the operators now tour in style. There are several im-
provements on this outfit worthy of mention. A dry galvanometer
replaces the oil damped model in general use. For portability the
advantage of this absence of oil is very apparent, and the current
needed to drive it is considerably less than the oil damped type. An
optical system requiring much less space and using a focused filament
image in place of a mechanical slit is among the newest additions.
Sound on this Mitchell portable equipment is recorded at projector
spacing, or the standard 14.5 inches ahead of the picture. As record-
ing is done by the variable area method, development and printing
can be done in virtually any laboratory on the road even though not
equipped with sound printer, so rushes or quick news releases may be
made almost anywhere. Quality compares favorably with the two-
machine method and the total equipment weighs less than four
hundred pounds.
DISCUSSION
MR. HAMMOND: May I ask why more even sound level is not maintained in
making the positive?
Subjects are cut off very abruptly, in the middle of a word often, and instantly
it goes into music accompanying the title.
MR. JONES: We regulate sound level to the best of our ability, but the record
is made under such varying conditions that it is very difficult to get an even level.
Feb., 1930] MODERN NEWS REEL 207
There is bound to be some variation although we are doing our best to overcome
it.
An explanation of abrupt cut-offs is the fact that the news reel is 10,000 feet
long and only 500 feet are shown.
MR. RICHARDSON: This puts the projectionist in an embarrassing position.
When level changes occur, the audience instantly blames the projectionist.
Audiences have no means of knowing such faults are out of the projectionist's
control.
MR. JONES: You must remember that news reels are taken every day, and
we haven't the time to cut or record sound as it is done in the studio. We get
a story at noon, it may be something very "hot" and it's on the screen that
night. We are getting better and not worse, however.
MR. C. L. GREENE: The rapid improvement in sound film is certain evidence
that the men in the production field are doing the best they can to eliminate
faults. The projectionist who has passed through the hectic time of conversion
from silent to sound basis can well appreciate what the news-reel man is facing.
We know we cannot expect perfect recording, but perhaps those in production
work don't realize the seriousness of some of these faults when the film gets into
the theater. No recording can be good recording if it cannot be well reproduced.
The audience, remember, doesn't know or care what the source of the disturbance
is, but is prone to blame everything on the projection staff.
We run Photophone recorded news reels on Photophone equipment, and I
make a detailed volume cue sheet for each reel. It is not unusual to have this
sheet call for amplifier gain control settings ranging all the way from 6 to 30
T.U., but this condition is not serious provided we have time to rehearse the
reel and have a second or two of silence between the portions requiring greatly
different amplification.
The other day, however, we had a typical case that was serious. Essential
dialog was recorded at such a low level that the maximum double amplitude
of the sound track was only 0.005 in. Following within 0.05 in. or less than
0.003 second came the cheering of a large crowd recorded with a double amplitude
of 0.065 in. The gain control had to be held at over 30 T.U. to render the dialog
intelligible, whereas 10 was ample for the cheering. The result when the cheering
started was that for one- or two-tenths of a second the amplifier probably delivered
in excess of 150 watts to the speakers, and they in turn sent forth a volume of
sound which was extremely unpleasant all over the house. In the case of the
patrons in the first few rows it was quite possibly painful. This was not a news
reel, but a studio production. Run through one type of very high grade re-
producing equipment it would probably have wrecked the speaker units.
One speaker questioned the possibility of an amplifier delivering enough power
to "blow people out of their seats." Scientifically speaking, of course, he is right,
but when immediately following such a disturbance patrons leave the theater
and are not seen in the theater again, it perhaps is not far wrong to say that they
have been "blown out of their seats."
MR. CRABTREE: I notice that one large manufacturer of radio receivers has
an automatic control device so that the volume output is constant. I think
the solution of the problem would be to install a similar apparatus in the pro-
jection booth.
208 HARRY W. JONES
MR. RICHARDSON: I am doubtful whether that could be done owing to varying
conditions in theater auditoriums. What is right now is not so in fifteen minutes
from now in the house when the audience has changed.
MR. CRABTREE: It could be set, and once set at a certain level, it will continue
to give you the sound at that level. Of course, the level could be changed occa-
sionally to take care of the varying audience.
MR. JONES: In recording, the volume level control is comparatively simple.
We have accumulated trucks more rapidly than we can train the personnel
needed, and men went out on the jobs who have not had sufficient training.
They accumulate knowledge as they go along and iron out the troubles.
MR. RICHARDSON: Let us assume this condition: Fifteen minutes after eight,
when the audience is in, you must have a certain volume setting, and then fifteen
minutes later you have more audience and must take care of that.
MR. CUTHBERTSON: An automatic control device would be out of the question
on the news reel system. It is not needed, in fact. One of the greatest users
puts out a news reel with no cue sheet. It is run at one fader setting, and the
operator should not change it; it runs through without variations in level.
FILM PERFORATION AND ITS MEASUREMENT
WALTER H. CARSON*
The advent of sound in the motion picture field and the growing
popularity of color productions, as well as the imminent changes in
the size of motion picture film, have raised many new problems
throughout the industry from the standpoint of the producer, the
laboratory, and the manufacturer.
Not least among these questions is that of the perforation. This is
not a new question, for it has been the subject of much discussion for
a number of years past, but, through the cooperation of the various
factors, there has been a gradual standardization. Besides the
perfection of the perforators themselves, there has been a continuous
effort to improve the sprockets and claws in cameras, printers, and
projectors. Also, the inevitable shrinkage of film has been reduced
to a minimum.
In the 35 mm. field a very definite basis of standardization has been
reached, which has been fully accepted by both the manufacturer of
raw film and the manufacturer of mechanical equipment, so that
damages to the film resulting from lack of uniformity between the
perforations and the devices for the transportation of the film through
the various mechanical units have to a large degree been eliminated.
It still happens, however, that the film user encounters some difficulty
in his camera, developing machine, or projector which can only be
explained by a fault in the perforations, which, in turn, might be
traced to excessive shrinkage of the film.
Heretofore, the means of convincing himself of the correctness of
this conclusion have usually been either crude and inadequate or un-
available on account of the intricacy of such equipment. Mechanical
engineers developing film equipment of any kind are still inclined to
demand a very close conformity to the figures of standardization on
newly perforated film and to condemn each minute variation from
these figures as an insurmountable difficulty. They disregard en-
tirely the fact that mechanical equipment must be so made as to
* Agfa Ansco Corporation, Binghamton, N. Y.
209
210 WALTER H. CARSON [j. s. M. P. E.
allow a tolerance in the film due to the factor of shrinkage. The old
empiric method of placing a piece of negative on a new piece of raw
stock to prove that the pitch of the perforation hole is incorrect, is
obviously not a safe method on which to form a judgment, since it is
always practically impossible for the mechanical man to know the
age of the film which he is using as a gauge.
It is hardly to be expected that newcomers in the industry, such as
cameramen, operators in the printing rooms, and projectionists, will
be entirely familiar with the long discussions which have taken place
in the past and are still going on in some foreign countries to establish
an international standardization. Neither can we expect them to
know that the best results are secured from films which do not have
an exact pitch in perforation or measurement between centers of
perforation holes of 4.75 mm., but that there is a maximum tolerance
between 4.68 and 4.76 mm. which will allow of free movement of the
film on all of the conveying equipment without risk. By far the
larger proportion of persons handling films, who have little interest
in these mechanical and theoretical problems, merely ask, when
difficulty is encountered: "What is the matter? Is the film or the
equipment at fault?" In such cases it is very essential, when trouble
is encountered, to be able to convince oneself whether the film per-
foration is correct or not, but, before attempting an examination or
measurement of any kind, it is desirable to know definitely what is
right and wrong. Theoretically, the answer to this is contained in
the terms of standardization which indicate how the film must be
manufactured or perforated to avoid trouble on standardized equip-
ment through which the film must be transported.
In order to refresh your memory, we will state that the standard
establishes the following measurements:
First: That the distance of perforations, or pitch, immediately
after perforation, must be between 4.75 and 4.76 mm. for posi-
tive film, and between 4.75 and 4.77 mm. for negative film.
Second: That the shrinkage under unfavorable conditions, such
as 720 hours in air of approximately 140 F. and of a 70 per
cent relative humidity, should not exceed 37.5 inches in 400
feet, or 0.78 per cent.
In the matter of the first clause of standardization, the film user
must, of necessity, take the manufacturer's word for the correctness
of the measurement at the time of perforation, because it is very
seldom that the film reaches the consumer immediately after being
Feb., 1930] FlLM PERFORATION AND ITS MEASUREMENT 211
perforated, and, in all makes of film the shrinkage starts even before
the can is opened. It is, therefore, necessary to standardize the
sprockets and claws to compensate for the shrinkage which has
already taken place before the film is put through the camera or the
printing machine. Under the present methods, it is only possible to
check the second items of standardization by means of elaborate
laboratory tests for which the film user has no facilities. It is also
essential for the operator to know how much variation or tolerance is
allowable in film at its various stages of handling before it will cause
trouble in any kind of equipment.
In order to clear up the first question regarding the actual measure-
ment of raw film before it is put to use in the camera or printer, an
average of a great number of tests was taken. This proved that per-
foration measurement of film at the time it reaches the consumer is
usually betwen 4.75 and 4.73 mm. It may be remembered that
variations of pitch must still go much further, in fact, below 4.68 mm.
before they will cause difficulty in well built equipment.
In the case of the claw movement on such equipment, it is easy to
understand why difficulty is not encountered because the diameter
of the claw is normally several tenths of a mm. less than the actual
size of the perforation hole; therefore, the difference in distance
between the first and fifth perforation holes, which are the ones used in
the claw movement, can be reduced from 19 to 18.7 mm. without
noticeable trouble.
The question of sprocket transportation is a different one, but here
again, numerous experiments have proven that a shrinkage of less
than 37.5 inches in 400 feet will not cause difficulty in either negative
or positive film.
For obvious reasons, after development and drying, the distance
between the perforation holes is still less. If the film is dried in the
laboratory only enough to give the proper or original hardness of the
emulsion, there will be a very small difference between its measure-
ment at that time and in the raw state. In most of the drying boxes
used at the present time, however, there is a shrinkage during drying
after development of from 0.1 to 0.2 mm., so we find that on the aver-
age, the processed film after it leaves the laboratory measures between
4.74 and 4.72 mm., and, in some special cases, as low as 4.69 mm.
The shrinkage of film, both negative and positive, continues to go
on as small quantities of solvent contained in the nitrocellulose base
are driven off. This cannot be entirely stopped, but the older the
212 WALTER H. CARSON [j. s. M. P. K.
negative or print gets the more this shrinkage is retarded until a final
point of shrinkage is reached. This continued shrinkage is rather
slow in the case of negative^because of the fact that negative is usually
more carefully stored in sealed tin cans and under favorable atmos-
pheric conditions. In the case of positive film, which is put through
the projection machine many times and subjected to the intense heat
of the projection lamps, the process of shrinkage will be comparatively
rapid.
It is interesting to note the experience gained from 100 pieces of
positive stock of various ages as they came into the exchanges.
These were carefully measured, and it was found that the measure-
ment between the perforations varied from 4.74 mm. to 4.69 mm.,
showing an average of 4.71 mm. which, of course, is still usable.
Let us compare these figures with the measurements established by
the French standardization, which call for 16 teeth engaging on the
transport sprockets. The diameter of the rolls at the base of the
teeth is 23.85 mm. Adding to this diameter the thickness of normal
film, which is approximately 0.15 mm., we obtain a total diameter of
24 mm. which, in turn, gives us a circumference of 75.3 mm. Divid-
ing this by 16 because of the 16 tooth engagement, we find that the
distance between the centers of the teeth on the circumference of the
sprockets at the base of the teeth is 4.71 mm., or exactly the figure
which we secured by the empiric experiment mentioned above.
It is very unusual to encounter shrinkage greater than this, but, in
the case of very old film which, in some instances, had been per-
forated prior to the setting of the present standard we encounter
shrinkage down to 4.68. Usually when film has reached this point
it would be necessary to discard it in any case because of its excessive
curl and brittleness.
From the foregoing it will be seen that it is possible with micro-
scopically accurate instruments to determine the shrinkage of the film
by measurement of the distance between corresponding edges of the
perforation holes or by placing two pieces of film together, one of which
is as new as possible, and thus test visually whether the old film has
shrunk or not, and, if so, how much.
The difference of one perforation width in one-half meter would
indicate, by the above test, that the difference in shrinkage between
the two pieces of film amounted to 2 mm. in 500 cm.
There are three methods with which we are familiar by which the
difference between perforations can be established.
Feb., 1930] FlU! PERFORATION AND ITS MEASUREMENT 213
The first is to count 100 holes on the film and make a measurement
with the ordinary ruler between the corresponding edges of the first
and one-hundredth perforations. This gives a measurement of
between 476 and 468, which is great enough in length to be easily
recognized when compared with the standard. It will tell just how
much in millimeters the film has shrunk between the individual
perforation holes.
The second method gives a similar measurement by comparison
with the standard but consists of taking the piece of film the length
of 40 perforations and stretching it between brass slides. The dis-
tance between the corresponding edges of the first and forty-first
holes is measured with micrometers and is approximately 190 milli-
meters. If this space is divided by 40, you again have the difference
between the individual perforations. This is merely a modification
of the first method mentioned, only using a shorter piece of film.
The third method is to measure the perforation space or pitch with
a calibrated microscope. It is essential in using this method to
make several measurements before striking an average. There is
always the possibility of a minute variation between the individual
perforation holes which could be detected by the microscope but
which would not be an accurate measurement of the shrinkage of the
film, nor be great enough to cause any difficulty with it.
In this connection we might mention that under the old system of
one-hole perforation it was essential to determine the exact distance
between each pair of holes, as a consistent variation would give an
unsteady picture and a noticeable change in the frame line on the
screen. At the present time, to the best of our knowledge, all of the
manufacturers are using the four-hole system of perforation, which
punches four holes on each side of the film at one time with a gang of
eight punches. The film is then drawn forward by a shuttle and
eight pilots, engaging and filling exactly the previous eight holes
punched, thereby very accurately placing the film into position before
the next eight holes are punched. With this system it is practically
unnecessary to check the distance between the individual holes unless
a marked recurrent unsteadiness is noted on the screen. We might
also mention another interesting point in this connection that tests
have proven that film having a uniform thickness shrinks uniformly
throughout its length, so that the relationship of the perforation
holes one to the other is not changed.
We do not believe that any of these three methods described above
214 WALTER H. CARSON [j. s. M. p. B.
are particularly popular for practical use. The first one is not
commonly known, and the other two require instruments of a type
not usually available to the film laboratory or exchange. It was
these facts which led to the introduction of a perforation pitch
measure by Agfa, which, by its size and convenience of use, makes it
pitch measure
FIG. 1. Perforation pitch measuring rule.
possible for the cameraman, laboratory operator, or inspector in the
film exchange to check the condition of a film as regards perforation,
accuracy, and shrinkage without intricate, optical, and mechanical
equipment, and the incidental loss of time and money.
This rule (Fig. 1) consists of a light metal bar having two pins at
the left end and a groove 35 mm. in width for its entire length. The
film to be measured is fastened over the pins, depressed into the
groove and pulled tightly against the pins to the right over the end
of the rule, as shown in Fig. 2. Underneath, where the film perfora-
tions rest, are square black marks, 2X3 mm., printed on the ruler.
FIG. 2. The rule with film to be measured.
The distance between these squares is slightly greater than the
standard distance between perforation holes on new film. For this
reason, these marks shift as regards the area seen through the perfora-
tion holes until the difference finally amounts to the width of one
perforation, or 2 mm. It is easy to recognize the point at which the
Feb., 1930]
PERFORATION AND ITS MEASUREMENT 215
inches .ta|eo
mm 4.72J i I I 4
Ll*J*J .
A
FIG. 3. Use of the upper scale.
right edge of the perforation hole will coincide exactly with the left
edge of the black mark underneath. By means of a scale, which is
given in both millimeters and inches outside the edge of the film, it is
possible to read, at the point at which this coincidence takes place,
the distance or pitch between the centers of the perforation holes on
the piece of film being measured.
As indicated by Fig. 3, in order to secure as much accuracy as
possible, the distance between the upper set of marks and the lower
4
|
~^L
W
in
I I I I
i I I *-|
m i
55
.18J60
FIG. 4. Use of the lower scale.
216 WALTER H. CARSON [j. s. M. p. K.
set of marks has been made different, so that in case of film having
little shrinkage the upper set is used. Where the shrinkage is below
4.72 mm. the lower scale is used, as you will see indicated in Fig. 4.
Greater accuracy is given in the reading of the lower scale. The
reading in the illustrated instance would be, actually. 4.719 mm.
You will see by comparison of the figures which we have quoted in the
foregoing that, with a scale 175 mm. in length, it is possible to measure
accurately a shrinkage below the usual point of film shrinkage.
The principle of this measurement is very simple and surprisingly
accurate, since it is possible to determine very quickly a variation
down to Vioo part of a millimeter which is accurate enough for all
practical uses.
A development of the idea which led to this principle of measure-
ment and a critical examination of its accuracy may be of interest to
some. We have, therefore, incorporated into this paper the basis
upon which the various measurements on the rule have been estab-
lished, together with the basic equation for working it out.
Let us take two pieces of film, one being as new as possible, placing
the oldest one on top of the other in such a way that, at a given place
which we will call A , the left hole-edge of the upper film coincides
exactly with the left hole-edge of the lower film. Since the upper film
has shrunk more than the lower one, there will be a certain distance
to the right, which we will call S, where we will find that the right
perforation edge of the upper film lies on the left perforation edge of
the lower. A simple equation gives as a result the relation between
the perforation space ~f the lower film, A, and the perforation space
of the upper film, X, the distance, S, between the beginning and
the reading point, and the width, B, indicating the width of the
perforation in the upper film. We, therefore, have the following
equations:
(1)
Now let us replace the lower film with a metal bar, bearing the
perforation holes as black marks, and, to facilitate the registration
s
s
= NA = NX
S B
+ B
A
V
X
A (S B)
5
S
AB
AX '"
Feb., 1930] FlLM PERFORATION AND ITS MEASUREMENT
217
of the first pair of holes exactly, we fix two pins accurately at that point.
Now we must decide about the length of the metal bar and what de-
gree of accuracy is desirable. On the bar, the distance between the
black marks will be determined by the two foregoing factors. Let us,
therefore, glance at Table I, which will give the distance of the
reading point from the pins, S, for various values of X, and A , figur-
ing the value of B in this equation as 2 mm., since that is the stand-
ard width of a positive perforation hole:
TABLE I
Distances of Reading Points from Rule Pins
a = 4.76
Marking Distance on the Ruler
4.77 4.78 4.79 4.80
Perforation dis-
tance of the
film. x = 4.68
119.0
106.0
95.6
87.1
80.0
4.69
136.0
119.3
106.2
95.8
87.3
4.70
158.7
136.3
111.5
106.4
96.0
4.71
190.4
159.0
136.7
119.8
106.7
4.72
238.0
190.8
159.3
136.9
120.0
4.73
317.3
238.5
191.2
159.7
137.1
4.74
476.0
318.0
239.0
191.6
160.0
4.75
952.0
477.0
318.7
239.5
192.0
4.76
954.0
478.0
319.3
240.0
It will be noted that it is possible to measure perforation distances
between 4.68 and 4.76 mm. with a rule,A75 n?ra. in length, provided
the distance between the marks is 4.79 mm.- A greater distance be-
tween the marks will reduce the length of the scale. A smaller dis-
tance will increase the accuracy, but also lengthen the ruler.
By establishing the distance between the black markings on the
upper row as 4.79 mm. it is possible to read a variation between 4.76
and 4.73 mm., and, similarly, by establishing the distance on the
lower row at 4.76 mm. it is possible to measure between 4.73 and 4. 68
mm.
We have assumed, up to the present, that the pins have been placed
in a position which will coincide exactly with the correct position of
the first pair of holes on the strip of film to be measured ; however, if
they are placed a little to the left, we can facilitate the reading of
slight variations, or, if these pins are moved to the left 1 mm., the
original equation will be changed as follows :
218
WAI/TER H. CARSON
5 == AB ~ X
AX
Table II shows the advantage of using the above equation.
TABLE II
Comparison of Two Pin Settings
Pins
Distance
between
Marks
* = 4.71 Mm.
4.72 Mm.
4.73 Mm.
On the marks
4.79
S
= 119.8
136.9
159.7
1 mm. to the left
4.76
S
= 96.2
120.0
159.7
You will note that these figures show that we gain greater accuracy
with the same length of rule.
In all of our calculations up to this point we have assumed the
perforation width as exactly 2 mm. For this reason this ruler would
be, strictly speaking, correct only on positive film, as negative film
has a perforation width of 1.854 mm. The discrepancy caused by
this variation, however, is so small as to disappear almost completely
in calculating the ruler from the beginning with a perforation measure-
ment of 1.92 mm., which is the figure actually used in establishing the
measurements as shown on this scale.
DISCUSSION
MR. EDWARDS: Is there lateral as well as longitudinal shrinkage of film?
MR. CARSON: This matter was first brought to my attention today. I was
told that there was a shrinkage of Vs inch in film of 70 mm. width.
MR. EDWARDS: I recently ran a film that was shrunken pretty badly. On
one side it rode perfectly and on the other it was terrible. The effect on the
screen was like a ship at sea.
MR. CARSON: If I may digress for a moment, I should like to tell you that in
the manufacture of film base two things count: One is the bead, which is a
thick part in the base itself. The second is that as you approach the edge of
the sheet, which under normal conditions is 42 inches wide, there is a gradual
thinning. Neither has anything to do with the normal shrinking in the roll.
In my paper I have spoken of a film having an equal thickness on both sides.
If the film is thinner on one side than on the other, the shrinkage will be different.
THE HUMAN EQUATION IN SOUND PICTURE PRODUCTION
TERRY RAMSAYE*
A great deal of the equipment now used in the recording of sound
pictures is highly unreliable and full of trouble.
The equipment and the machines are, in the main, a great deal
more reliable and cause less trouble than the men who run them.
Manpower is frequently the major problem in industry, and it is
now acutely the most difficult problem in our industry of the talking
motion picture.
This problem is going to be solved, of course. One of the answers
is education of personnel through the endeavors of such organizations
as the Society of Motion Picture Engineers. Another answer is the
selective action on personnel which always operates most conspicu-
ously through the early periods of any industry involving a new
technic. The turnover in studio and sound truck employment is
likely to be rather rapid in the next year for this reason.
It is time to "debunk" the sound recording business and take the
mystery out of its processes. This Society of Motion Picture Engi-
neers can help importantly in that direction.
In its present status of development, sound recording devices ap-
pear to need rather frequent attention and a considerable array of
routine tests, but it is not unfair to say that its operation requires
hardly more attention from the recordist than is necessary for the
intelligent tuning of a fairly sensitive radio set. Yet, there is ob-
servable, a continual effort to camouflage the work with a great atmos-
phere of complexity and strange obscurities.
Recently one of the companies with whose activities I am some-
times concerned had a simple task in re-recording a dramatic sound
strip for the elimination of some minor faults of the negative.
It is hardly necessary for me to interpose the statement that the
best sound re-recording is now done by direct connection of the re-
corder with the amplifier serving the sound head, making the opera-
tion entirely an electrical operation without audible sound.
Pathe Exchange, Inc., New York City.
219
220 TERRY RAMSAYE [J. S. M. P. E.
Now the alleged technicians on this job insisted on delaying the
work for two days and transporting and installing a ponderous belt
driven film phonograph, despite the fact that two perfect sound pro-
jecting machines were already available in the plant. I had the
boldness to protest against the unnecessary delay and expense.
"But," the experts screamed at me, "we have to keep away from
the noise of the projector gears when we re-record." They were so
unutterably dense that they did not realize that it takes a microphone
to electrically listen to a noise.
Every executive concerned with the making of sound pictures can
tell you plenty of stories as bad as that one, and some a great deal
worse.
The situation is, however, no more serious in the field of sound
than it once was in simple motion picture photography. As late as
1916, I found laboratory experts running around with mysterious
little black books in their pockets, with secret formulas for making
various tones on film. These secrets they so carefully guarded as
their capital of skill had been published to the world for years by
George Eastman. They were well known to any interested person
who could read. I have always thought that an introduction to the
art of reading would be a great help to the movie industry anyway.
I am inclined to have a little more patience with the present prob-
lems on the sound recording operations in the field when I recall ex-
periences with an endeavor to put panchromatic film into studio and
newsreel operations about fifteen years ago. Some of the best camera-
men in the business assured me that they could get the same or better
results with ordinary ortho stock and some trick filter of their own
devising. When I started to talk to them about absorption bands,
they walked away tapping their heads. The status of panchromatic
stock today is ample answer.
We can anticipate that some day sound recording mechanisms will
be about as foolproof as the cameras are now. But that will not
come soon enough to save the necks of the alleged recordists who
refuse to qualify.
It seems fairly clear that we may hope for a great simplification of
sound recording equipment. In one of my annoyed hours the other
day, I found that in producing Pathe* Sound News with the excellent
but ponderous camions made by the General Electric Company, we
used 44.63 ton-miles per second of edited screen time. Operating a
big fleet of these big trucks makes newsreel production closely re-
Feb., 1930] THE HUMAN EQUATION IN PRODUCTION 221
semble the railroad business in terms of mileage and tonnage. We
may recall that Mr. Thomas A. Edison's first motion picture camera
was larger than a doghouse, and weighed about half a ton. It has
less capacity for the same work than a five pound automatic camera
of today.
Some of our troubles in the sound recording business bearing on
personnel have their smiling aspects. In a sound track made by one
of a fleet of camions assigned to an event in Washington, we found
surprising sound resembling thunder and the sharp crash of lightning
coming from a very clear sky, and disagreeably accompanying an
otherwise pleasant bit of music. The resulting investigation re-
vealed that the microphone man had been standing alongside his
instrument, cracking peanuts while the event went on. That nickel's
worth of peanuts was expensive for both the company and the
employee.
One of the major problems of personnel reposes in the difficulty of
convincing both engineers and recordists that they are engaged in an
enterprise which is an art quite as much as it is an industry. While
mechanical and electrical perfection are necessary they are not in
themselves enough. There is no substitute for thinking and for that
general assortment of common knowledge that the diverse problems
of the work require.
A trivial case in point developed not long ago when we were engaged
in making a sound interview with Chief Justice Taft. The micro-
phone man had been cautioned to make notes for the subject report
on each scene as it was shot. At the conclusion of the talking on this
assignment, the young man dashed up and demanded, "Mr. Taft,
now what is your first name and how do you spell it?"
PROGRESS IN THE MOTION PICTURE INDUSTRY*
The most important items of progress during the past six months
have been the extensive use of all-color sound pictures, or pictures
with extensive color inserts, and several demonstrations of enlarged
projected pictures by the use of film wider than 35 mm.
Only two-color subtractive processes are at present in vogue and in
one process extensively employed, two dye images are produced in a
single layer film by imbibition. Although some three color imbibition
films have been prepared, they have not been publicly displayed
To date only one type of wide film has been put on the market,
this being 70 mm. wide. Comment of the trade has been most en-
thusiastic with regard to its suitability for scenics and news events,
but it is apparent that a new photographic technic is required to se-
cure more pleasing perspective in the case of photoplays. Difficul-
ties involved in the more universal adoption of the wide film are the
present lack of standardization of size, the necessity for greater
illumination at the projector aperture, and the prevention of film
buckle.
Studios in Hollywood are now producing only about 5 per cent of
silent pictures. When it is considered that only one year ago the
first dramatic sound pictures were shown before the Society, notably
The Singing Fool, the remarkable progress made since that time is
apparent. There has been a steady improvement in the quality of
sound reproduction, notably in the theater, but in many cases the
quality in the theater falls far short of that which the film is capable
of producing when it leaves the studio. Much still remains to be
done in the way of improvement even with the best of recording.
With the high quality music given by the modern radio receivers the
public is realizing that the average theater music is not equal in
quality to that emanating from their radios at home.
Notable advances in studio technic have been (a) the tendency to
use a minimum number of microphones and eliminate mixing, (b)
the silencing of cameras by means of insulating coverings thus per-
mitting greater freedom of camera location, (c) the tendency to use
* October, 1929 Report of the Progress Committee.
222
PROGRESS REPORT 223
more live studios so as to simulate more closely natural sounds, and
(d) the non-simultaneous recording of scene and sound.
A noteworthy advance in reproducers has been the introduction of
the condenser or electrostatic reproducer consisting of a rubber
diaphragm coated with aluminum foil stretched across a metal grid.
Apart from the high quality resulting, the reproducer occupies no
more space than the average screen and can be raised and lowered
just as easily.
No fundamental advances have been made in the field of stereo-
scopic motion pictures and although some of the sponsors claim that
their wide film processes give stereoscopic effects, they are at the
most pseudo-stereoscopic. A much higher order of relief is noticeable
in many of the pictures in color.
Although color pictures have been televised during the past six
months, the probability of television usurping the present motion
picture appears to be very remote.
Respectfully submitted,
J. A. BALL J. W. COFFMAN
F. A. BENFORD R. B. FARNHAM
L. J. BUTTOLPH G. B. MATHER
G. L. CHANIER R. ROGERS
J. I. CRABTREE, Chairman
SUBJECT CLASSIFICATION
I. PRODUCTION
A. Films and Emulsions
1. New Materials
2. Manufacture
(a) Nitrate Film
(6) Acetate Film
3. Miscellaneous
B. Studio and Location
1. General
2. Studio Construction
3. Lenses and Shutters
4. Cameras and Accessories
5. Light Sources
6. Make-up
7. Exposure and Exposure Meters
8. Trick Work and Special Process Photography
9. Technic of Direction
10. Methods of Recording Sound
11. Actors, Scenarios, Sets, etc.
224 PROGRESS REPORT [J. S. M. P. E.
C. Laboratory Practice
1. Equipment
2. Photographic Chemicals and Solutions
3. Printing Machines and Methods
4. Editing and Splicing
5. Titles
6. After Treatment, Cleaning, Reclaiming, and Storage
II. DISTRIBUTION
III. EXHIBITION
A. General Projection Equipment
1. Projectors and Projection
2. Fire Protection
3. Lenses, Shutters, and Light Sources
B. Special Projection Methods
1. Sound Picture Projection
2. Stereoscopic Projection
3. Continuous or Non-intermittent Projection
4. Portable Projectors
C. Miscellaneous
1. Screens
2. Theater Construction and Illumination
IV. APPLICATIONS OF MOTION PICTURES
A . Education
B. Medical Films, Radiography, and Photomicrography
C. Telephotography and Television
D. General Recording
V. COLOR PHOTOGRAPHY
A . General
B. Additive Processes
C. Subtractive Processes
VI. AMATEUR CINEMATOGRAPHY
A . General
1. Cameras
2. Projectors and Accessories
3. Editing, Scenarios, and Libraries
B. Color Processes
VII. MISCELLANEOUS USES, STATISTICS, AND NEW BOOKS
I. PRODUCTION
A. Films and Emulsions.
Some of the special negative emulsions for making sound motion
pictures announced in the spring report have found extensive use
Feb., 1930] PROGRESS REPORT 225
during the summer of 1929 as the bulk of pictures made were all-
sound pictures or contained sound sequences. Tinted films for sound
positives were described by Jones at our spring meeting. 1 These
films have the base tinted with dyes which transmit light capable of
exciting uniformly the photo-electric cell thus avoiding a fluctuation in
the volume level during a change of tint which occurred with some of
the older tinted bases. A patent has been granted on a film base
suitable for sound motion pictures having a substance in the base
rendering it translucent. 2
A marked increase in the use of film emulsions for color motion
pictures has occurred during the past six months. Many entire fea-
tures in color and sound have been announced, a number of which
have been released, notably, On With the Show which required about
350,000 feet of negative film in the making. 3
The most radical advance since the advent of sound is the impend-
ing adoption of wider film. This has apparently been a result of
(a) the introduction of processes designed to give pseudo-stereoscopic
effects, and (6) the need for a larger picture when screening large
musical stage settings. Three processes have been announced,
namely, the Spoor Natural Vision process 4 which uses films 63.5 mm.
wide, Magnafilm, 5 which uses a film 56 mm. wide, and Grandeur
which employs a film 70 mm. wide. The Spoor system is capable of
projecting a picture 70 feet wide although a screen 52 feet wide by 30
feet high was used in the demonstration. Magnafilm for which stereo-
scopic effects are also claimed was demonstrated in New York at the
Rivoli Theater on July 25th, the screen used being 40 feet wide by
20 feet high.
A sound newsreel (sound-on-film) and a feature picture made on
Grandeur film opened at the Gaiety Theater, New York, September
17th and was favorably received. 6 A screen of 40 feet overall width
was used which fills the proscenium arch.
Another method of securing larger pictures which has many com-
mendable features is the Fear process. 7 This uses standard 35 mm.
film and photographs the picture lengthwise instead of across the
film by means of a special optical system which rotates the image
through 90 degrees, a similar rotation also being necessary on pro-
jection. A longer sound track per picture frame is a feature of this
process.
Westerberg 8 has analyzed several of the suggestions for wider film
and warns against the confusion which may result if several film sizes
226 PROGRESS REPORT [j. s. M. p. E.
should be adopted. He suggests a picture size of 36 mm. by 22 y 2
mm. leaving 4 mm. for the sound track and 11 mm. for the sprockets
giving a film 51 mm. wide. In the positive print, the sound record
is printed outside the perforations and with sound-on- disk methods a
narrower film (47 mm.) is suggested.
To avoid difficulties resulting from damage to the sound track
because of its narrowness and proximity to the picture area and per-
forations, the German Tri-Ergon process uses a 42 mm. film and
prints the sound track in the center of the extra 7 mm. width. 8 *
In the more direct field of manufacture, Didee" 9 has given informa-
tion on the manufacture of film base and preparation of emulsions.
Details of the preparation of Ozaphane film have been published by
Pouchon 10 and two patents have been granted relating to films coated
with a diazo compound and phenol. 11 Only a few patents have been
granted on improvements in the manufacture of nitrate base 12
whereas the continued large number of patent applications related to
acetate bases 13 give evidence of the efforts being made to standardize
this product. Two patents have been granted on the design of a
machine for making transparent film of viscose or cellulose acetate. 14
A few patents have appeared on special base compositions 16 such as
cellulose sulfate and carboxylate.
Improvements in methods of increasing the sensitiveness of photo-
graphic emulsions have been protected by patents, particularly the
addition of certain substances to gelatin, 16 or bathing the emulsioned
material or treating the emulsion before coating in a solution of a
double salt of silver and an alkali with boron in the negative radical. 17
B. Studio and Location.
The nearness of New York to the center of sound equipment manu-
facture and stage talent has caused a revival of work in the studios
located in the vicinity. 18 Several new studios have been built and all
of these are reported to be in operation. The production increase in
New York has not affected Hollywood apparently because in that city
additional sound stages have been built 19 and other silent ones re-
modeled. There has been considerable emigration of acting talent
to Hollywood and it is reported that voice teachers have been busily
engaged assisting the "silent" actors to acquire voices.
Most of the sound pictures produced abroad have thus far been
"shorts" and news weeklies. British International Pictures in
England and Ufa in Germany have completed sound stages and pro-
Feb., 1930] PROGRESS REPORT 227
duction is in progress. Patent difficulties have held up construction
plans generally in Europe but these are reported to have been cleared up
recently. Descriptions of several sound studios have been published. 20
In filming Trader Horn in the Belgian Congo, complete sound re-
cording equipment and laboratory processing apparatus were used so
that each day's negatives could be processed and inspected before
changing to a new location. 203
Lenses and Shutters. Lee 21 has reviewed the functions of modern
high aperture lenses and predicts that progress may be looked for in
improved color correction for use with panchromatic films. A new
lens of //1. 5 aperture has been described adaptable to most modern
professional and amateur cine cameras. 22 This aperture is claimed
by Sonnefeld 23 to represent very nearly the limit of wide aperture lens
design. A novel lens for multi-image photography contains several
reflecting prisms between the front and back components. 24 Gifford 25
has given details for constructing rapid rectilinear lenses of fluorite
and quartz and of calcite and quartz for ultra-violet photography. . .
A lens for use in a non-intermittent motion picture camera has been
patented. 26
Patents on shutters for cine cameras are related to shutters adapt-
able for either cameras or projectors, regulators for controlling rota-
tional speed of the shutter with changes in cranking speed, shutter
blades designed as spherical sections, etc. 27
Cameras and Accessories. Descriptions of new cameras or recon-
structed cameras are somewhat meager although several of these are
known to be in daily use in connection with sound recording, natural
color photography, and the four types of wide pictures mentioned
previously in this report. Useful data by Reinecke 28 on the theory
of movement in relation to cine apparatus should prove of assistance
to designers of cameras and other equipment. Effective illumination
in making good lap dissolves has been discussed by Kofinger. 29
Brackets attached to the tripod top have been described for holding
the camera view finder away from the camera and allowing the
director to view the action conveniently. 30 At the last meeting of
the Society, Struss 31 described the method of arranging a battery of
several cameras for simultaneous photography of action in dialog
pictures. Six cameras were used in one scene in photographing
Coquette, and about 1000 feet of film were used in each camera. It
was possible to complete the scene "shooting" in two days originally
scheduled for five days.
228 PROGRESS REPORT [j. s. M. p. K.
A small combined camera and projector exposes pictures on one-
half of one side of a film, then reverses and exposes the other half.
The pictures may be projected either on a screen or in a small album-
like box in daylight. 32 A compact, quickly adjustable tripod with an
extension from 85 cm. to 170 cm. has been marketed by the Askania-
Werke in Berlin. 33 This same firm has produced a tripod head by
which the camera may be moved through a 180 degrees vertical tilt,
slid forward or backward and rotated for panoraming. 34
The Mitchell camera has been equipped interchangeably for vari-
able area or variable density sound recording. 35 Stull 36 has de-
scribed several of the sound proof housings devised by various camera-
men and technical staffs to avoid the use of large sound booths.
These new housings are known by rather picturesque names such as
"Bungalow," "Blimp," "Baby Booth," etc.
Patents 37 have been granted on a large number of improvements in
camera design relating to pressure plates, friction clutches, magazine
holders, cameras for making stereoscopic pairs of images, etc.
A camera and projector having optically compensating move-
ments of comparatively simple design have been described by Hat-
schek. 38
Time-Lapse and Ultra-Speed Cameras. A historical review 39 of the
various types of rapid cameras has been published and it is claimed
with one type that exposures up to 100,000 per second are possible
for certain subjects. Thun's ultra-rapid camera employs continu-
ously moving film and a rotating lens wheel and is capable of 4000
pictures per second. 40 Another camera invented by Cranz of Berlin
will take 5000 pictures per second. 41 Beck 42 has described a time-
lapse camera which may be set for automatic exposures at intervals of
from 15 seconds to 10 minutes. Patent protection has been granted
on an automatic electrical device for actuating motion picture cameras
which operate at timed intervals. 43
Studio Light Sources. Incandescent lighting continues to bej
employed extensively in the production of many sound pictures,
although arc lighting has by no means been discontinued as Sebring
has shown in a recent article. 44 The problem with arcs has been to!
reduce motor noises and this has been accomplished by using choke i
coils and toggle switches to cut out the motors during actual shooting.;
The use of tungsten powder inside lamp bulbs is claimed to increase!
their life about 30 per cent as the efficiency may be kept at a maximum,
during an entire run. 45 Lamp manufacturers continue to improve;
Feb., 1930] PROGRESS REPORT 229
the efficiency of the higher wattage lamps, 46 as well as that of the
smaller lamps used in conjunction with sound recording and repro-
ducing equipment. Several new models of Klieglights designed for
sound recording work have been described. 46a
Silvered glass has been shown to be superior to aluminum as a
reflector. 47 A large spotlight of German design contains three rows
of reflectors around the side and to the front of the housing which
reflect the light to a series of mirrors set at slight angles immediately
behind the source. 48 Light which would otherwise be lost is thus
used to increase the brightness of the spot.
In photographing the color sequences of Rio Rita 386 lamps were
required having a total wattage of nearly a million. 49 For the picture,
Sally, it is reported that over 5 million watts were required and for
Broadway, nearly 4 million watts.
Incandescent illumination is being used rather extensively in Eu-
rope. Lighting methods in the English studios are reported to be very
similar to those used in this country except that there is a marked
tendency to avoid strong highlights and backlighting. French studios
are making tests on the use of incandescent lighting but are hamp-
ered by lack of the best lighting equipment. German studios are
reported to be using incandescent lamps to a considerable extent.
Data have been published on several new types of incandescent lamps
developed in Germany, 50 including semiportable lamps rated as high
as 5000 watts using either facetted or polished parabolic reflectors.
Make-up. Actors have found an orange make-up without eye-
shading most successful for use in an all-color motion picture. 51
Two leading professional actresses have described their methods for
using make-up in some detail for the benefit of cine amateurs. 62
Exposure Meters. Naumann 53 has described a photo-electric cell
which has been mounted in a housing on a motion picture camera so
that an image of the object may fall on the cell, and an illumination
reading be taken on a meter. Neutral gray filters are finding con-
siderable use on cameras to enable a full aperture to be used in order
to secure preferential focusing. 54 Patent protection has been given
on an exposure meter of the fade-out type wherewith the shutter is
automatically set when the indicator on the meter is just discernible. 66
Trick Work and Special Process Photography. Dunning 56 has
pointed out that the original patents will shortly expire controlling
trick printing and composite negative making and that future in-
ventors can therefore claim only improvements on basic principles.
230 PROGRESS REPORT [j. s. M. P. E.
The largest stage entirely devoted to special process work is in a
studio at Burbank, California, where a room 150 by 300 feet was used
recently. 67 In the sound picture, Masquerade, an actor played a dual
roll and double printing on the sound track was accomplished success-
fully. 58 Methods of making "matte shots" have been described by
Sersen. 69 These consist in double printing a painted section of a
scene onto photographed action. Several improvements in special
process photography 60 have been patented one of which utilizes lentic-
ulated film for making stereo and trick pictures and another employs
variously colored backgrounds and lights to secure composite ef-
fects.
Direction Technic. A greal deal more care in rehearsal has been
found necessary in directing talking pictures as retakes are expen-
sive., 61 Absolute silence is imperative whereas with silent pictures,
a working studio was usually a very noisy place. In a recent sound
picture, Lummox, one set of a concert hall took up the entire space in
the largest sound studio (225 feet long by 132 feet wide by 73 feet
high) . The action was directed entirely from a glass enclosed cupola
that surveyed the whole scene, connection being made by telephone
with cameramen, directorial assistants, and sound engineers. Play-
backs enabled the orchestra and the players to hear at any time the
record of the previous action. 62
A director at the Paramount Studios in New York used a traveling
camera in photographing over 85 per cent of a recent sound picture. 63
Every scene was rehearsed with such great care that no cutting of the
negative was required.
Sound Recording. Public interest in sound pictures has speeded up
the activities of producers and extensive programs have been an-
nounced this past summer with production schedules well under way.
Recent mergers between large producers may help to centralize the
production activities and insure better distribution. New recording
units are being installed almost monthly and sound studios have been
constructed in Hollywood and New York in the United States, Elstree
in England, Berlin in Germany, and plans are in progress in France,
Belgium, Russia, and other countries. In England, it is reported
that more capital has been made available than ever before with a
resulting increase in facilities for making British pictures. In Ger-
many, 75 sound films composed chiefly of "shorts" 64 were produced
between July, 1928, and July, 1929.
Physioc 66 has analyzed some of the problems in sound picture pro-
Feb., 1930] PROGRESS REPORT 231
duction and believes that acting will show improvement under the
supervision of sound recording.
The Gaumont method of sound recording using a sound record
which is transparent to visible light but absorbs the ultra-violet, as
mentioned in the last report, has been described more completely and
protected by an additional patent. 66
Schinzel 67 has reviewed various methods of producing sound records
on films which transmit visible radiation but absorb ultra-violet.
Another variable area method of sound recording has been described
by Miller. 68 It is known as the Vita vox which utilizes a light valve,
an image of which is focussed directly on the film. The methods of
recording used by Tobis (Ton Bild Syndicate) have been dealt with
by Bohm. 69 The position of the sound record which was originally
outside the perforation area has been changed to make it conform
with common practice. The Selenophon is still another variable area
method of sound recording which appears to have promise. Hat-
schek 70 states that a torsion galvanometer is used, the image of an
illuminated slit on the vibrating band being magnified 100 times for
recording on the film. For reproduction a "condenser-less" type of
selenium cell is used. The lag of the cell is stated to be compensated
for largely by the suitable use of amplifiers.
The technic of electromagnetic recording has been studied by a
German pioneer in this field, Curt Stille, 71 who claims that besides
having most of the advantages of optical recording the method avoids
all difficulties inherent to film such as resolving power, development
troubles, and printing errors. Play-back can be made immediately
and the record is not subject to scratches. Records 15 years old were
found to be as good as when first made.
The British Acoustic film system utilizes separate films for the
picture and the sound record which latter is of the saw-tooth type. 72
A selenium cell is employed in the reproducer, the lag being offset by
using a filter circuit which attenuates the lower frequencies in correct
proportion.
There has been further progress in voice doubling so that it can on
occasion be done to a very high grade of perfection, but a public re-
action against it has developed in those cases where it has become
known. The practice is, therefore, being very rapidly discontinued.
At the same time, a somewhat related method is very promising
which involves recording the sound and scene with the same actors,
but at different times. This method is not open to the objection
232 PROGRESS REPORT [j. s. M. P. K.
previously mentioned, but does make it possible to do the recording
in acoustically proper rooms without confusion of lights and camera,
and in the photography makes it possible to proceed in the usual way
as regards lights, angles, cameras, spoken instructions from director,
etc. The method in brief, is to do the sound recording first and then
to do the photography interlocking the cameras with the play-back
device. There promises to be an expanding use of this method par-
ticularly in musical numbers.
In the more usual methods of sound recording, advances have been
made in obtaining acoustical perspective exactly analogous to
methods of lighting which avoid flatness and suggest visual perspec-
tive. The methods which give this desirable result, also give some
simplification in the necessary mixer control (only one microphone
is considered necessary in a set as large as 15 feet by 30 feet) and allow
the set designers to use a greater range of materials since it is no
longer necessary to make all sets of sound absorbing materials.
Hemardinguer 73 has treated the subject of manufacturing and
registering of phonograph disks. Improvements in methods of
rotating the wax disks have been effected according to Elmer. 74
Hatschek 75 has discussed the characteristics of photo-electric cells
and with Lihotzky 76 has treated the subject of the optics of sound
film processes.
Theory underlying the physical basis of sound films has been
treated in a series of papers by Klages 77 and others, covering such
subjects as electrons and their properties, the action of electrons in a
high vacuum, etc.
A review of the acoustical problems in conjunction with sound
recording and reproduction has been made by Hatschek. 78 Paris 79
has deduced a formula for calculating the reverberation coefficient of
absorption of a material if the coefficient of plane waves is known for
all angles between and 90 degrees. In general, the reverberation
coefficient differs from the coefficient at normal incidence. Data of
this nature are valuable in determining the construction materials for
"live" sets according to Maxfield, 80 thus giving the actors greater
freedom of action.
A ten weeks' course giving instructions on sound, the theory of
sound recording and reproduction with explanations of recent de-
velopments is being offered this fall to 250 students by the Academy
of Motion Picture Arts and Sciences. 81
Humphrey 82 treated the subject of sound studio recording installa-
Feb., 1930] PROGRESS REPORT 233
tions at the last meeting of the Society, discussing not only the
arrangements of stages, monitor rooms, cutting and review rooms,
but also the construction materials for foundations and walls. Re-
recording has been done successfully up to ten times according to
Morgan 83 who described the method at the May 1929 meeting of
the Society.
There have been a considerable number of patents taken out in
relation to methods of sound recording which describe 84 among others
a method of recording on a plastic surface by the use of X-rays ;
a means of distorting the vibrations of large amplitude during re-
cording and correcting the distortion when reproducing the sound;
a process for impressing a high-speed sound record consisting of two
parallel records on a film by moving the film in one direction and
simultaneously moving sound recorders in the opposite direction,
permitting but one recorder to function at a time; a method of
binaural recording and reproducing, comprising a plurality of super-
imposed films each of which has a distinct sound record thereon and
is of different color, red and blue.
Actors, Scenarios, Sets. Problems in connection with scenario
writing for dialog films have been treated briefly by Jackson. 85
It is reported that the Paramount Hollywood studios have found
a mono-rail system advantageous to facilitate the rapid transporta-
tion of sets from place to place within the buildings. A turret 14 feet
high mounted on a 6 wheeled truck was used in several recent pictures
to pivot a steel girder 31 feet long. At the end of the girder was
mounted a platform for the camera and cameraman. This equipment
permitted rapid movement of the camera for photography from
several angles. 86
Bangs 87 has dealt with methods of estimating the cost of a produc-
tion based on story and scenario; location expenses, unit personnel,
laboratory, studio, and overhead. Problems confronting the location
manager are reviewed by Witham. 88 Detailed descriptions have
been published of nearly all of the British motion picture studios. 89
C. Laboratory Practice.
A special laboratory building to be devoted entirely to problems in
connection with sound pictures has been built by the Bell Telephone
Company in New York City. 90 The Kodak Company has opened a
laboratory in Hollywood which contains developing and printing
234 PROGRESS REPORT [j. s. M. p. B.
rooms as well as a library and a completely equipped little theater
and projection room. 91
Equipment. A general article has been written on the design of
automatic processing machines with suggestions on their use. 92
A compact tube developing machine known as the "Rovo" has been
marketed. 93
Photographic Chemicals and Solutions. Methods of obtaining fine
grain images have been reviewed 94 and developers described that give
images finer than can be obtained with the Kodak borax developer
but all formulas are open to the objection that the development time
required is excessively long (45 minutes to one hour). Abnormal
graininess may occasionally be due to atmospheric conditions rather
than to the solution used according to Barsy 95 who also describes tests
on several developers and strongly recommends the Kodak borax
formula.
Two reports were presented before the Society at the last meeting
on further studies on the borax developer, one by Moyse and White 96
and another by Carlton and Crabtree. 97 The former recommend a
new formula with the hydroquinone omitted as giving satisfactory
results with negative film. The latter find the present formula satis-
factory for general negative development and specify methods of
revival of the solution to keep the working capacity at a maximum
throughout the useful life. A considerable portion of the paper is
devoted to a study of methods of improving graininess of images pro-
duced by this developer as well as ways of varying the rate of develop-
ment of the solution.
A series of comprehensive papers are being published by Chibissoff
and his collaborators 98 reviewing and correlating the available data
on the chemistry of developers and development. As a result of an
investigation on the fogging properties of developers stored in contact
with various metals and alloys, Ross and Crabtree 99 conclude that
zinc, copper, and tin tend to give trouble from aerial fog or produce
chemical fogging effects. In a developer containing bisulfite, zinc
forms sodium hydrosulfite which is a strong fogging agent.
An informative study of the properties of fixing baths was de-
scribed by Crabtree and Hartt 100 at the May, 1929, meeting of the
Society. Criteria for comparing various fixing baths are established
and data are presented for compounding solutions having specific
properties. The formation of a precipitate on the addition of po-
tassium iodide solution to a fixing bath has been suggested by Gar-
Feb., 1930] PROGRESS REPORT 235
riga 101 as a test to determine the exhaustion point of the bath.
Clerc 102 has shown that unless fixation is prolonged for an abnormally
long time at normal temperatures, the usual solution will not ma-
terially reduce the image density.
I. G. Farbenindustrie Akt.-Ges. have patented the use of a 1.3 or
2.4 or 2.6 diaminophenylazonium silver compound as a desensitizer
either as a preliminary bath or in the developer solution. 103 A
modification of the usual development treatment of films containing
diazo compounds consists in adding only the diazo compound to the
film coating and using a developer containing an azo coupling agent
and a weak alkali. 104
Printing Machines and Methods. A printer for simultaneous print-
ing of sound and picture negatives was described by Depue 105 at the
spring meeting in 1929. This development is an indication of the
problems which have been introduced by sound-on-film pictures as
greater care is required in printing than heretofore. A photo-electric
exposure meter has been designed for use with printers. 106 An idea
of the capacity of the large printing laboratories can be had from a
recent report that a Hollywood laboratory is now equipped to process
2700 feet of negative film and 11,000 feet of positive film per hour and
to handle sound film in 1000 foot rolls. 107 A number of patents 108 on
printer improvements have been taken out. Some of the more novel
patents may be mentioned: (a) the use of ultra-violet light for printing ;
(b) deflection of the light beam in a printer by the use of a rotating
magnetic field ; (c) multiple printing devices ; and ( d) an apparatus for
determining the contrast and density of a photographic image.
A table for use in making animated drawings has been described by
Adam 109 which incorporates an automatic focussing device similar to
that described by Norling before the Society a year ago.
Editing and Splicing. Loeffler 110 has described the problems en-
countered in editing variable density sound films and states that
with experience certain noises can be identified visually and the
synchronization tested by counting the intervening frames. An
ingenious device for rewinding is a spool with a collapsible center
which allows the sides to collapse and free the film. 111 Patent pro-
tection has been granted on a film winding apparatus which draws the
film from the inside of a roll. 112 Another device for holding endless
bands of film has been patented by Harzer. 113 A shrinkage measuring
device mentioned in the previous report has been protected by a
U. S. Patent. 114
236 PROGRESS REPORT [j. s. M. P. E.
Titles. No outstanding articles on titling have appeared but two
patents are of interest. The first comprises a device for forming a
title on greased paper and exposing the film through the paper. 115
The second describes a projection printer having a rotating table for
holding the titles interposed between the light source and the film. 116
After-Treatment, Cleaning, Reclaiming, and Storage. Jasienski 117
has studied the effect of various intensifies on the graininess of the
image and found that chlorochromic acid and a commercial product
called Nosublim gave least increase in graininess.
A finishing laboratory has developed a process for increasing the
life of positive prints. 118 It consists in treating the emulsion side
with a chemical compound immediately after processing which pro-
tects the film from scratches, oil, and dust. A cleaning device mark-
eted under the trade name, "Imp-Impregnator" cleans, "impreg-
nates," and dries the film at the rate of 6000 feet an hour. 119
A novel device announced recently is a film inspection machine
which is constructed without sprockets and, as the film is rewound,
the machine detects any breaks, tears, or defective splices. 120 A film
clip which can be slipped on a roll of film without scratching it has
been invented to replace the commonly used rubber band. 121
A few patents have appeared on processes of lubricating and con-
ditioning motion picture film. 122
II. DISTRIBUTION
The introduction of sound pictures particularly those having the
sound on disks has increased the problem of the distributors. The
sensitiveness of the sound records and the extraneous noise resulting
from careless handling make the problem of inspection in film ex-
changes more difficult. Footage numbers have been found of great
value in connection with the inspection of sound film. 123
III. EXHIBITION
A. General Projection Equipment.
Projectors and Projection. Comparatively few changes have been
noted recently in projectors equipped for ordinary motion pictures
but many improvements have appeared in connection with projectors
for sound films and the newer wide films.
A projector of Italian manufacture has, as a novel feature, an
automatically adjusted shutter which permits as few as 14 pictures
Feb., 1930] PROGRESS REPORT 237
to be projected per second without flicker. 124 A German projector is
equipped with spools containing loose centers automatically regulat-
ing the film tension, also a shutter which rotates in a ball shaped
housing between the lamp and the gate. 125
As a change-over signal it has been suggested that a spring hinged
arm be folded over the first few convolutions of the film during re-
winding. When the arm is released during projection, it closes the
circuit of an electric bell. 126 Another device makes the change-over
automatically and also stops the projector and cuts off the light in
case of a break. 127
Types of projectors have been classified into three groups by a
committee appointed by the German government. The classes are
(1) dangerous and for use in booths only, (2) dangerous only in un-
usual circumstances, and (3) safe. 128 An advisory council has been
established recently which is working in conjunction with the
American Projection Society, studying projection conditions in
theaters. 129
Patents related to projectors deal with a great many devices such
as pull-down mechanisms, electromagnetically operated clutches, air-
cooled lamphouses, etc. no
Errors in architectural design affecting location of the projection
booth are cited to show that greater care should be given by architects
in the location and design of this important element in a motion pic-
ture theater. 131
Fire Protection. Lehmann has written a general article dealing
with motion picture film and projectors with relation to fire hazards
and predicts that nitrate film will continue in use for some time to
come. 132 Detailed specifications of construction materials for pro-
jection rooms in Germany have been published. 133 Joachim 134 has
published a comprehensive article dealing with shutter design, fire
hazards in projection booths, and other related subjects. A number
of patents deal with various improvements in methods of stopping the
projector mechanism in case of fire, closing port holes, the use of heat
resisting screens in the path of the light, etc. 1
Projector Lenses, Shutters, and Light Sources. Patents on optical
projection systems 136 disclose methods of obtaining maximum illumi-
nation with concentrated filament lamps, and a means for projecting
a small beam of light upon a douser shutter to permit the projectionist
to determine previous to projection the alignment and focus for
homogeneous screen illumination.
238 PROGRESS REPORT [j. S. M. P
Patzelt 137 has discussed the theory and practice of projection light
sources, particularly mirror arcs.
B. Special Projection Equipment.
Sound Picture Projection. The industry is rapidly adapting itself
to sound film projection and it is predicted that over 9000 houses will
be equipped for handling one or more types of sound films by January,
1930, about 5200 theaters having been equipped by the middle of
August. 138
For the projection of Fox Grandeur Pictures at the Gaiety Theater
which opened during September, 1929, a new projector was used built
especially to accommodate the 70 mm. film. It incorporated a high
intensity arc consuming 150 amperes for a 70 foot throw onto the 17
foot by 35 foot screen. Special lenses were necessary to accommodate
the large screen and a new type of carbon arc was used which will take
an amperage as high as 250, considered to be necessary for larger
houses. 139
Sound pictures (all "talkies") had their first showing in several
European countries in August and were enthusiastically received
although many pictures had to be shown only with English dialog.
The first Russian made sound film was ready for showing the latter
part of August on Russian reproducing equipment, import of foreign
equipment being prohibited. Reviews of the first all British "talkie,"
Blackmail, made at Elstree are favorable. It is predicted that over
500 British houses will be wired for sound pictures by January,
1930. 14
Interchangeability is a feature of several new projectors equipped
for sound projection. One projector is designed in three models,
sound-on-film, sound-on-disks, or both and if one of the first two types
are purchased, the other may be added later. 141 Several firms are
manufacturing sound equipment for attachment to standard pro-
jectors. Features of the Royal Amplitone are a high pedestal for the
disk assembly permitting easier handling of this type of equipment,
freedom from turn-table flutter, and a locked optical device for the
sound-on-film assembly. 142 A curved sound gate is used by Tobis
Klangfilm to prevent film buckling. 143
New apparatus for playing disk records continues to be announced.
The Filmophone 144 is stated to permit interruption of the sound at any
predetermined point and the Electrocord 146 consists merely of a well
balanced turn-table for use in small halls. RCA Photophone has
Feb., 1930] PROGRESS REPORT 239
nounced a dual system unit selling at $3000.00 for use in theaters
seating 500 or less. 146
A California exhibitor has installed a few sets of ear phones in his
theater for the use of deaf patrons; each set being adjustable for
volume by means of a small choke coil. 147 Descriptions have been
published of several types of amplifiers. 148 A small vacuum cleaner
device is available for removing dust accumulation in delicate elec-
trical parts of sound apparatus. 149
A reproducer employing the condenser principle has been de-
scribed. 150 It consists of a slotted aluminum grid which acts as one
plate and a thin layer of gold or aluminum leaf glued to a rubber
diaphragm serves as the other condenser plate. Several of these grids
are attached to the rear of the projection screen. A hydraulic lift is
now used for the stage mounting of loud speaker horns. 151
A segmented cardboard disk has been announced which can be used
to synchronize the picture with a disk record. 152 Fader control from
the auditorium is possible with an installation used by Metro-Gold-
wyn-Mayer for road shows in the larger neighborhood theaters.
A committee of technicians has undertaken an investigation to
draw up a set of standards for camera and projector apertures accord-
ing to a report from the Academy. 163 A preliminary survey indicates
that the majority of theaters showing sound-on-film pictures are using
a screen picture that is nearly square. Sliding masks are sometimes
used alone or in conjunction with a horizontally movable lens mount.
Sometimes a lens of lower focal length is used and an undersized aper-
ture plate thus restoring the 3 by 4 proportion but at a loss of some of
the picture. A recent report 153a states that all the large producers on
the Pacific coast have agreed to adopt at once the recommendations
of the joint committee of this Society and the Academy of Motion
Picture Arts and Sciences providing for the use of a standard aperture
of one size in all cameras.
Numerous patents have been granted on improvements in sound
projection apparatus and accessories. 154
Stereoscopic Motion Pictures. Since the public showing of the
Teleview in New York City in 1922, there have been no further de-
velopments of commercial interest in stereoscopic pictures until the
past summer when wide pictures were introduced. Both Fox
Grandeur and the Spoor-Bergren systems are claimed to give the
illusion of depth but those who have seen them state it is only a fair
illusion. Special lens systems are used in the recording cameras.
240 PROGRESS REPORT [j. s. M. P. .
A compressed air control is used in the Spoor-Bergren projector to
hold the 56 mm. film flat. 155 Ritterath 156 is inclined to believe the
secret of stereoscopic motion pictures lies in the use of a composite
screen rather than special cameras or projectors. A relatively com-
plicated method of stereo-motion pictures having severe practical
limitations has been described in a paper by Ives 157 before the Optical
Society of America. A few patents related to stereoscopic motion
pictures have been granted. 158
Non-intermittent Projection. Efforts continue to perfect non-
intermittent projectors, most of the published results coming from
Germany. The most successful of the commercial models, the Me-
chau projector has been further improved in Model 4, a description of
which appeared in an issue of Kinotechnik early this year. 159 Burm-
ester and Mechau 160 have prepared a very complete treatise on the
mechanical and optical principles underlying this projector. Several
German theaters are reported to be using them and an earlier model
was installed for a short time at the Capitol Theater in New York a
few years ago. Thun 161 has published a paper on projection with
optical compensation and Hatschek 162 has described a non-intermit-
tent projector of comparatively simple construction which utilizes a
spiral concave mirror with an inner hollow face which rotates on a
vertical axis once per picture. The first paper of a series written on
various non-intermittent projector systems has appeared recently. 163
It describes the projector invented by Nilson in which one pair of
oscillating mirrors are used to project the image in place of the usual
large number of mirrors and prisms. Several patents 164 have been
taken out on optically compensated projectors which describe among
others the use of a rotating disk (set at 45 degrees to the film plane)
in the periphery of which mirrors are placed; the employment of a
rotating polygon of refractors having plane parallel surfaces; and the
use of mirrors carried by two rotors and arranged prismatically there-
on, the number of mirrors being different on the two rotors.
Portable Projectors. A sound-on-film portable projector has been
marketed by Western Electric. A mechanical governor controls the
continuous movement of the film past the photo-electric cell and sound
lamp. 165 Various devices 166 have been patented for handling endless
film bands in projectors, coin-in-slot operated projectors, and trans-
lucent screens. One patent describes a music roll on which are
printed a series of pictures which show as motion pictures when the
roll is rewound rapidly. 167
?eb., 1930] PROGRESS REPORT
C. Miscellaneous.
Screens. The porous nature of many materials used for "talkie"
screen construction has resulted in a serious lowering of screen reflec-
tion values and is a regrettable feature of sound pictures. 168 One new
sound screen uses staggered perforations and it is claimed that better
picture definition is obtained accompanied by clear sound emission. 169
The use of grid condensers mounted directly on a screen, referred to
previously, 170 makes available a sound motion picture screen which
takes up little more space than a regular screen, overall thickness
being about 16 inches.
Parallel steel bands, 7 mm. wide and 0.1 mm. thick are placed in
front of a screen to permit daylight projection. To avoid a direct
black border on a screen, Keith-Albee hang a black velour curtain 10
feet behind the screen (which is exactly picture size) and use a black
ground cloth on the floor. 171 Patents 172 issued include the use of an
endless luminescent moving band viewed as a screen, several types of
translucent screen materials, and the use of tiny glass pyramids em-
bedded in a lead paint base.
Theater Construction and Illumination. The largest theater on the
Pacific coast was opened June 28, 1929. It seats 5000 persons and
is designed in French architecture. The projection throw is 212
feet. 172a Meshrabponi-Film and several other Russian organizations
are building a "Swimming Theater" or showboat to seat GOO per-
sons. 173 It will be equipped for showing pictures and will have a
special landing stage to allow it to stop at any desired place. Syl-
vester 174 has discussed the essentials in floodlighting for theater stages
and points out that prismatic lenses in front of the projector are used
to control beam spread instead of reflector contours. The improved
Clavilux invented by Wilfred, known as a Luminar has been installed
in the Paramount Theater. It is described and illustrated quite fully
in an article by Fox. 176 Applebee 176 has written on modern stage
lighting. Henly 177 has written several articles on heating and venti-
lating the theater. He describes panel systems of heating whereby
ceilings, walls, and floors are heated by means of jointless steel coils
embedded in the structure. His paper deals also with various
methods of filtering the air. A marked reduction in reverberation
and echo in public halls is claimed by Berliner to be obtained when
the side walls are covered with wire cloth cement covered dia-
phragms. 178 An audience filling one-quarter of the floor space is
sufficient to prevent disturbances from the floor.
242 PROGRESS REPORT [j. s. M. p.
IV. APPLICATIONS OP MOTION PICTURES
A. Education.
Further details on the experiment in the use of specially prepared
classroom films were presented to the Society by Finegan last spring
at the New York meeting. 179 The Mountain States Telephone and
Telegraph Company is using a portable sound motion picture unit for
educational instruction of their personnel. 180 Talking films are
expected to be particularly valuable in vocational guidance courses
according to Kitson who discussed their application at a symposium
held at Columbia University in July, 1929. 181
Motion pictures of the moon have been made at the Princeton
University using a lens 24 inches in diameter. 182 The picture shows
the sunrise on the Copernic Cirque at a speed one hundred times
faster than normal, the pictures having been taken at the rate of 10
frames per minute.
Although sound pictures offer an inviting medium for promotion
of business sales and for aiding industrial relations, the present cost
of installation of the equipment prevents their extensive use. As
time advances, industrial firms, large hotels, and educational institu-
tions will no doubt install apparatus and the problem will be simpli-
fied.
A British Grammar School has used motion picture films for three
years for instructional purposes and they are considered a useful ad-
junct, especially in connection with a technical education. Only two
British firms make films for teaching purposes and reliance had to be
placed on private enterprises for the source of most film material.
No assistance is given by the Board of Education. 183
The University of Southern California and the Academy of Motion
Picture Arts and Sciences have amplified their plans for courses re-
lated to motion picture technic and are offering work in several
subjects for the year 1929-30. 184
The first issue of the International Review of Educational Cine-
matography appeared in July, 1929. This is a monthly publication of
the International Educational Cinematographic Institute of the
League of Nations. Each month's issue is in five editions, English,
French, Italian, German, and Spanish.
A ballet master utilizes motion pictures for teaching intricate steps
and for preservation of the technic of his more famous students. 186
Thun 186 has dealt with the accuracy with which the construction and
I
Feb., 1930] PROGRESS REPORT 243
operation of a machine can be shown by appropriate motion pictures
and the ease with which such information can be imparted to a large
number of people. Various types of electric furnaces have been
filmed in action and their working principles illustrated with the aid
of animated diagrams. 187
Motion pictures are projected in an underground amphitheater
500 feet below the surface of a Missouri mine. 188 During the latter
part of 1928, aviation comprised more than 16 per cent of newsreel
views and the popularity and interest in aviation has been aided
materially by the motion picture. 189 A motion picture, The Rise of
Woman, has been produced by the New York State Federation of
Women's Clubs and the Motion Picture Producers and Distributors
of America. 190
Fokert 191 has reported on film and art in Russia. There is a
museum and research department for motion pictures in Moscow.
State cinema schools have been organized and there are two high
schools of cinematography for directors, actors, etc.
B. Medical Films, Radiography, and Photomicrography.
Stutzin 192 has described the use of a lamp and optical system called
the Cystoskop for photographing internal body cavities, such as the
bladder. Cine-photomicrographic studies of the human capillaries
have been made by Hauser. 193
Gottheiner and Jacobsohn 194 have described their methods of mak-
ing X-ray motion pictures. They used an indirect method whereby
an X-ray image on a fluorescent screen was photographed on hyper-
sensitized film using a lens aperture of f/1.4 and a camera having a
300 degree sector opening.
Cine-photomicrographs of cell stresses during the seasoning of
wood have been produced at the U. S. Forest Products Laboratory in
Madison, Wisconsin. 195 An oral description of the activity on a
microscopic slide has been made on wax disks to accompany a motion
picture, a beam splitter being employed to permit viewing during the
camera exposure. 196 The Leica camera has been equipped with a
micro-objective thus permitting photomicrography with compara-
tively simple equipment. 197
C. Telephotography and Television.
Work is in progress in several laboratories throughout the world on
problems of telephotography and television but no developments of
244 PROGRESS REPORT [j. s. M. P. E.
commercial interest have occurred recently. Friedel has described
Von Mihaly's system in some detail and it is claimed that synchroni-
zation has been simplified further. 198
Public demonstrations of television have been made in South
Africa by the Baird Television Development, Ltd. The apparatus
used is similar to that recently placed in operation in Germany with
which sound and vision are broadcast simultaneously on two wave-
lengths. 199 The Australian Broadcasting Company expected to
commence broadcasting pictures from station 2FC in Sydney by the
latter part of August, 1929, using the Fultograph process. 200
In a television long distance test, the voice and face of D. W.
Griffith were transmitted from Schenectady, N. Y. to Los Angeles,
Calif. 201 The voice of Gloria Swanson was recorded on an RCA
Photophone equipment after having been broadcast by short wave
over 3000 miles from London to New York. 20ia
A Luxemberg scientist living near Paris has recently completed an
intricate, but apparently practical, device for the transmission of
moving pictures by wireless. 202 Kuchenmeister 203 has patented the
use of the discharge from a crystal oscillator as a light source in a
television apparatus.
D. General Recording.
Time-lapse cameras have been used by the U. S. Coast Survey for
recording readings on a number of instruments measuring the ve-
locity of water currents in Chesapeake Bay. 204 Mather has produced
a series of geology films for use at Harvard University. 205 The U. S.
Department of Agriculture has made a film study of an abandoned
concrete bridge until cracks formed. 206
A high speed camera capable of making 8000 to 16,000 pictures per
second has been described by Beck. 207 The film is wrapped around
the periphery of a motor driven drum and is exposed with the aid of a
lens and 45 degree mirror. It is recommended for studying the
movement of electric discharges. The same author has described a
camera for photographing the interior of tubes, rifle barrels, and
similar surfaces, a linear record being obtained. 208 The use of the
motion picture camera for studying the duration and brightness of
ignited flash powders is discussed by Maiser and Umbehr. 209 Elec-
tric welding has also been studied by means of a cine camera designed
to make four narrow pictures across each average frame of 35 mm.
film. 210 The Imperial College of Science (London) is making a
Feb., 1930] PROGRESS REPORT 245
photographic study of gaseous explosions, using an ultra-rapid chrono-
photographic apparatus which exposes 200 meters of film per second. 211
A camera equipped with a lens which refracts the light rays into a
cone of about 90 degrees has been devised for taking pictures of light-
ning. A wide angle lens system is placed behind the front or "fish
eye" lens to project the rays on the film. 212
V. COLOR CINEMATOGRAPHY
The most extensive production program of color motion pictures
during the history of cinematography was launched during the
summer of 1929. The bulk of the pictures made thus far and planned
for are by the Technicolor process and most of them are to be all-
sound pictures. Expansion plans are announced by this company
which will give them eight times their present capacity early next
year. 213 Two producing units are to be built in New York and their
Boston and Hollywood laboratories are to be expanded so the former
will be fitted with five units and the latter with three units. The
announcement also states that the present two-color subtractive
process is to be displaced by a three-color process of similar basic
principles. It is reported that Technicolor has developed a method
whereby the sound track can be a black and white silver image where-
as the picture area is composed of dyes.
Brown 214 has described some of the problems encountered in making
the all-color (Technicolor), all-sound picture, Under a Texas Moon
during the summer of 1929. The difficulty of making exterior shots
by a two-color process is well known and great care was used in choos-
ing the location so that the rock formations and vegetation would be
of suitable color for good reproduction. To overcome the color
changes resulting from light variations, portable incandescent lamps
were used. These were focussed on cloth reflectors to minimize the
heat. Special booths had to be utilized for the color cameras as they
make more noise than black and white cameras.
Tietze 215 has written on the use of the Busch two-color additive
process for photographing surgical operations. This process uses a
twin lens camera and projector with filters over the lenses. The
two images of the positive are superposed on the screen. Patents 216
dealing with three-color additive processes are related to the prepara-
tion and use of various types of multi-color screens, a three filament
lamp with a condensing system, and a method of reducing the image
size so that three pictures may occupy one frame.
246 PROGRESS REPORT [j. s. M. P. E.
No further commercial developments have been noted in the use of
lenticulated films for theater use but numerous patents have been
taken out protecting various improvements in their preparation and
use. 217 Several of these patents are concerned with methods of
printing lenticulated films.
Thornton 218 has protected the use of double width film for a two-
color process carrying line or dot screens side by side with a panchro-
matic emulsion coated on the screens.
The two-color subtractive process known as "Multicolor" has been
described by Crespinell. 219 Two negatives with emulsion surfaces
adjacent are run through a standard camera at one time, the front
negative is orthochromatic with the surface layer dyed orange-red to
act as a filter for the image recorded on the rear panchromatic emul-
sion. Double coated yellow dyed film is used for printing the pair o
images in register on opposite sides of the film. The images are
colored by a combined dye toning and chemical toning method, am
are varnished before projection to protect them from scratching.
The Zoechrome process demonstrated in London during the spring
of 1929 is a three-color subtractive process with a fourth or key image
in black and white included. In taking the picture, every alternate
frame on the film is exposed as usual for ordinary cinematography
and the remaining frames are filled with three reduced images taken
through filters cutting out the red, blue, and green, respectively. The
standard size image is printed first, then each of the others, by
varnishing, recoating with emulsion, enlarging the image, developing
and dye toning in succession. 220
In another process known as Splendicolor 221 being exploited in
England, three negatives bearing the respective color corrected
monochromatic images are printed onto a positive film carrying
gelatin-bromide layer on one side and a coating of pure gelatin on the
other. The blue image is printed on the silver emulsion and the
yellow and red are formed by the Pinatype process in bichromated
gelatin on the opposite side of the film.
A great many patents have been taken out on improvements in
subtractive color processes. 222
VI. AMATEUR CINEMATOGRAPHY
A. General Equipment and Uses.
A useful illustrated description has been published of nearly ever>
Feb., 1930] PROGRESS REPORT 247
available type of camera, projector, and accessory recommended for
amateur use with 9.5 mm., 16 mm., and 35 mm. films. 223
Amateur Cameras. Interest in amateur movies continues to grow
as improved equipment and film become available. The large list of
finishing stations for regular and Kodacolor films recently published
by the Kodak Company reads like the itinerary of a round-the-world
tour. 224 This Company has announced a 50 foot spring driven two
speed camera which may be obtained with either an//3.5 or //1. 9 lens
which are interchangeable with a long focus //4.5 lens. The //1. 9
outfit may be equipped for Kodacolor. 225 A British made amateur
cine camera is fitted with an //2.6 lens, a direct vision finder, and is
designed to work at three speeds. 226 An improved model of the Pathe
"Baby-Cine" has been announced called the "Motocamera." The
motor drive will run through an entire charge of film and the
shutter and pull-down have been modified. 227 Zeiss Ikon A.-G. has
marketed a 16 mm. camera with an//2.7 lens. Film is supplied in
magazines holding 33 feet. 228 A combined amateur camera and
projector has been announced. 229 For projection the back of the
camera is removed and the mechanism mounted on a stand with a
motor, illuminating system, and shafts for 120 meter reels. The
shutter is rotated at double speed to avoid flicker during projection.
Zeiss has introduced a Biotar//1.4 lens of 17 and 25 mm. focal
length for use on amateur cine cameras. 230 Announcement has been
made of a 4 inch Tele-Xenar //3.8 telephoto lens. It is an unsym-
metrical half-cemented anastigmat lens of five elements. 231 Although
not yet on the market, a lens of the extreme aperture of //0.99 is
reported to have been constructed for use on amateur standard
cameras. 232
A remote control for starting and stopping the Filmo 70 has been
developed. 233 McKay 234 suggests that the camera for the advanced
amateur should have a dissolving shutter, a method of rewinding the
film in the camera, and a means for visual focusing. A few develop-
ments have been noted in the use of equipment for synchronizing
sound with pictures for the amateur. McKay describes three ways
of recording: (1) the use of wax disks with a portable phonograph,
(2) the use of a microphone in conjunction with a loud speaker and a
dictating machine, and (3) the second method with the addition of
single switch control of the motors on the camera and dictating
machine. 235
Projectors. The Victor 16 mm. projector claims as features a
248 PROGRESS REPORT [j. s. M. P. E.
straight line optical system, power rewind, and an automatic stop to
prevent film breaks. 236 An inexpensive hand cranked projector has
been added to the equipment in the amateur cine field. 237 A self-
contained projecting unit in a walnut cabinet has been announced
which uses a small translucent screen that is extended 2 feet in front
of the projector. 238 The Ensign Kinecam projector uses a 60 volt,
100 watt lamp with a variable resistance control. 239 Bell & Howell
have modified their Filmo projector to adapt it to classroom use. 240
The supply and take-up reels on the new Zeiss-Ikon projector are
located side by side on a common shaft under the gate and lens sys-
tem. Film must be removed for rewinding. 241 A 100 watt lamp,
operating from either 1 10 or 220 volt circuits is incorporated in the new
Agfa projector for 16 mm. film. The lamp house is fan cooled. 242
A device for reproducing sound, adaptable for home movies has
been described briefly. Four variable area records are printed side
by side on an opaque paper positive, 6 mm. wide. The sound is re-
produced by suitable electrical sound reproducers connected to a loud
speaker. 243 A projector using 9.5 mm. film can be equipped with a
speaker unit called the "Radioscope" synchronized with the picture. 244 i
The unit can also be used to permit sound accompaniment of a master
sound film from a central studio when a duplicate print is shown in
the home.
An interesting historical description of an animated family album
developed in 1902-3 was published recently in Germany. 245 Five
concentric rows of pictures on a disk were animated by rotating the
disk and viewing the changing picture through a peep hole in a coven
fitting over the box holding the disk.
Two patents have been granted on improvements in amateur
projectors. 246
Enlargements from 16 mm. pictures may be made up to 2 J /4 by 3 1 /
inches by using a cone like box which fits on a Filmo projector. 247
A new 16 mm. reversal film has been placed on the market 248 a.
well as an additional negative film. 249 The leader on the former i
green and the trailer red on the processed film for convenience of the
projectionist.
Editing, Scenarios, Libraries. Magnetized steel letters and a stee
background have been announced as titling equipment for the cine
amateur. 260 For use with the Ensign Auto-Kinecam, a titling box is
provided wherein the camera is pointed downward at a copyboarc
with movable letters fitted into the base. 261
Feb., 1930] PROGRESS REPORT 249
Library prints on 16 mm. film are available of pictures made with
Jenkins' speed camera which operate at 3200 pictures per second. 262
Bird studies have been made with an amateur camera which operates
quietly enough so that the birds become accustomed to the motor
noise. 253 Motion pictures taken by an amateur of an auto accident
were introduced as evidence in an Australian court at the request of
the justice. 254 A correspondence school in electricity is being taught
wholly by the use of 16 mm. pictures. 255
B. Color Processes.
A new projector for Kodacolor films has been issued by Bell &
Howell. 256 The lamp operates at 5 amperes and is fitted with a
variable resistance. Two patents 257 have appeared on the use of
lenticulated films. One is related to the use of a five banded filter
which comprises one green, two red, and two blue areas. The other
patent covers the use of an optical system for lenticulated films which
is designed for use with curved gates, compensating lenses usually
required in projection being avoided.
A projector 268 for projecting natural color pictures has t been
patented. The film passes between condensing and projecting lenses.
A shutter and a rotatable color screen, (having several different color
areas) are positioned between the film and the condensing lens.
VII. MISCELLANEOUS USES, STATISTICS, NEW BOOKS
A psychologist at Columbia University has reported on a two year
investigation made on the influence of motion pictures on crime. 259
The results indicated that most children remembered very little detail
of the picture and were unsympathetic with the wrongdoers. Only
5.2 per cent of the 150,000 patrons were under 21 years old.
Over 250 million persons see motion pictures weekly throughout
the world according to W. H. Hay's annual report. 260 Over 23,000
controversies were arbitrated by film boards during 1928, only 28
claims requiring the services of a seventh arbitrator.
Export of positive and negative film from the United States fell off
10 million feet in 1928 when 222 million feet were shipped out com-
pared to 232 million feet in 1927. Latin America continues to be the
largest consumer; Europe is next. 261 A more recent report by
Golden 262 indicates an increase in total film exports for the first six
months of 1929 which is accounted for largely by the demand for
positive prints in Europe. The totals are 121,810,453 linear feet for
250 PROGRESS REPORT [j. s. M. p. E.
1929 compared with 112,752,169 feet for 1928. Imports of raw film
for the first six months of 1929 amounted to 251 million linear feet
compared with 117 million linear feet during the same period of 1928.
Imports of finished film ran about the same as in 1928, ! 3 /4 million
feet of negative and 2 3 /4 million feet of positive films.
Nearly three thousand more American made projectors (both 35
mm. and 16 mm.) were exported in 1928 than in 1929. 263 Six thou-
sand were shipped out to 71 countries.
A comprehensive series of statistical data has been published giving
information on most all phases of the motion picture industry. 264
Some of the more outstanding items are as follows: News reel com-
panies use about ten million feet of raw film annually, only five
hundred thousand feet of which reaches the theaters. American
films return about $1.00 worth of extra trade to U. S. manufacturers
for every foot exported. The exhibition branch of the motion picture
industry uses nearly half of all the man power employed in motion
pictures, or 110,000 of the 235,000 persons engaged in all branches.
Production employs 75,000, distribution 20,000, other branches
30,000.
The world's 52,000 picture theaters have a combined seating ca-
pacity of 21,150,000 for the 1,793,000,000 people. Laboratories
process 1,500,000,000 feet of film yearly. Amateur movie makers use
upward of 20,000 miles of 16 mm. film yearly and have purchased
more than 175,000 amateur cameras and projectors in the United
States alone. Of the 11,000 extras registered at the Hollywood Cen-
tral Casting office, only 4000 receive work regularly and less than 400
can speak in foreign tongues, or with foreign accent necessary for the
foreign parts in talking pictures.
Sovkino now owns 10,000 square meters of space near Moscow and
1929 production schedules call for 86 long feature pictures. 265 About
85,000 persons are engaged in film production. Building programs
for 1932 call for the erection of 2000 new theaters and 8000 trans-
portable projection outfits for use in villages. Neither cameras nor
film were manufactured in Russia previous to September, 1928, but
about 2000 stationary and 8000 portable projectors are made an-
nually. 266 Everyone of the 400 workers clubs in Moscow is stated to
be equipped with projection facilities. 267 Leningrad boasts a theater
seating 3000 and plans are under way for the construction of several
others of similar capacity. Theaters devoted to special presentation
of scientific films are popular.
Feb., 1930] PROGRESS REPORT 251
NEW BOOKS
1. Practical Television, by E. T. Lamer, D. Van Nostrand Co., Inc., New
York. N. Y. (1928).
2. Ripening, of Silver Bromide-Gelatin Emulsions with Ammonia and Am-
monium Carbonate (Reifung von Bromsilber-gelatin mit Ammoniak und Am-
moniumkarbonat) Encyclopedia for Photography and Motion Pictures No. 113,
O. Papesch, W. Knapp, Halle, Germany (1928).
3. The Motion Picture Almanac, Quigley Publishing Co., Chicago, Illinois
(1929).
4. Heraclitus or The Future of Films, by Ernest Belts, Button & Co., New
York (1928).
5. Sound Motion Pictures, by H. B. Franklin, Doubleday, Doran & Co., Inc.,
New York (1929).
6. Handbook of Projection, Vol. Ill, by F. H. Richardson, Chalmers Publish-
ing Co., New York (1929).
7. Kinemato graph Year Book, Kinematograph Publications, Ltd., London,
England (1929).
8. Amateur Cinematography, by Owen Wheeler, Pitman & Sons, Ltd., New
York (1929).
9. Small Film Cinematography (Die Schmalfilm Kinematographie), by O.
P. Herrnkind, Hartleben's Verlag., Leipzig (1929).
10. Scenario Writing, by Marion N. Gleason, American Photographic Pub-
lishing Co., Boston, Mass. (1929).
11. Motion Pictures in the Classroom, by B. D. Wood and F. N. Freeman,
Houghton, Mifflin Co., New York (1929).
12. Applied Aerial Photography, by A. C. McKinley, Wiley & Sons, Inc.,
New York (1929).
13. Proceedings of the Seventh International Congress of Photography, edited
by W. Clark, T. Slater Price, and B. V. Storr, Heffer & Sons, Ltd., London (1929).
14. Photographic Sensitometry and Its Applications (La Sensitometrie Photo-
graphique et ses Applications), by Geo. Moreau, Gauthier-Villars, Paris (1928).
15. Manual of Sensitometry (Manuel de Sensitometrie), by L. Lobel and M.
Dubois, P. Montel, Paris.
16. Photochemistry and Photographic Chemistry (Photochemie und Photo-
graphische Chemie), by W. Noddack and E. Lehmann, Union Deutsche Verlags,
Berlin.
17. Handbook of Scientific and Applied Photography (Handbuch der Wissen-
schaftliche und Angewandten Photographic), 9 Vols. (in progress), Springer,
Berlin. Color Photography (Farbenphotographie), Vol. 8 has been published.
Authors are L. Grebe, A. Hiibl, E. J. Wall.
REFERENCES
1 Trans. Soc. Mot. Pict. Eng., XIII, No. 37 (1929), p. 199.
2 Ger. Pat., 469,415.
3 Ex. Herald-World, 94 (July 6, 1929), p. 130.
4 Ex. Daily Review & Mot. Pict. Today, 25 (June 1, 1929), p. 11.
6 Ex. Herald-World, 95 (July 27, 1929), p. 19.
252 PROGRESS REPORT [j. s. M. P. E.
New York Times (Sept. 22, 1929), p. X7; also Film Daily, 49 (Sept. 18, 1929),
P. 1.
7 C. L. WILLIAMSON: Internal. Phot., 1 (Aug., 1929), p. 4; also Ex. Daily Review
& Mot. Pict. Today, 26 (Sept. 21, 1929), p. 3.
8 Internal. Phot., 1 (Aug., 1929), p. 12.
8S Lichl Bild Bilhne, 21 (Nov. 10, 1928), p. 22.
9 Revue Scienlifique, 67, No. 10 (May 25, 1929), pp. 294-307.
10 La Nature, No. 2814 (Aug. 1, 1929), pp. 100-102.
11 Fr. Pal. 645,357; Brit. Pat. 301,879.
12 Brit. Pats. 301,878 and 302,961 ; U. S. Pat. 1,703,470; Fr. Pat. 645,358.
13 U. S. Pats. 1,697,907; 1,698,048; 1,699,049; 1,701,229; 1,704,282; 1,704,283;
1,704,304; 1,704,306; 1,711,110; 1,711,111; 1,711,314; 1,711,940; 1,711,941;
1,716,419; 1,716,420; 1,716,422; Brit. Pats. 300,477; 301,655; 301,755; 302,280;
302,390; 302,615; 302,667; 303,006; 303,099; 303,134; 303,135; 303,136;
303,485; 303,491; 304,278; 304,279; 305,096; 305,601; 305,946; 305,947;
306,125; 306,531; 3C6,911; 307,392; 307,431; 308,323; 308,395; 308,657;
309,201; 309,203; 309,913; Fr. Pat. 645,110; Can. Pat. 289,854.
14 Brit. Pat. 304,374; Fr. Pat. 640,066.
15 Brit. Pats. 303,493; 303,752; 303,794; 305,674; 306,132; 308,798.
16 Ger. Pat. 463,879; 464,450; 467,179; 468,171; 468,604.
17 Brit. Pat. 301,962.
18 DOUGLAS Fox: Ex. Herald-World, 94 (Mar. 16, 1929), p. 31.
19 Ex. Daily Rev. & Mot. Pict. Today, 26 (July 6, 1929), p. 16.
20 L. C. MOBN: Kine. Weekly, 145 (Mar. 28, 1929), p. 25; also Bioscope, 79
(Apr. 10, 1929), p. 25; and Mot. Pict., 5, No. 2 (1929), p. 7.
Ma Ex. Herald-World, 96 (Sept. 21, 1929), p. 33.
21 Kine. Weekly, 145 (Mar. 21, 1929), p. 63.
22 Phot. J., 69 (Mar. 1929), p. 125.
23 Phot. Korr., 64 (Dec. 1, 1928), p. 376.
24 Amer. Cinemat., 9 (Mar., 1929), p. 10.
25 Trans. Opt. Soc., 30, No. 1 (1928-29), p. 34.
26 Ger. Pat. 468,838.
27 Brit. Pat. 307,683; Fr. Pat. 640,833 ; U. S. Pats. 1,700,513; 1,716,512.
28 Kinotechnik, 11 (Feb. 20, 1929), p. 87.
29 Kinotechnik, 11 (Apr. 5, 1929), p. 174.
30 Ex. Herald-World, 94, Sect. 2 (Mar. 16, 1928), p. 85; also Internal. Phot., 1
(July, 1929), p. 14.
31 Internal. Phot., 1 (July, 1929), p. 17; also Trans. Soc. M. P. Eng., XIII, No.
38 (1929), p. 477.
32 Ex. Herald-World, 94, Sect. 2 (Mar. 16, 1929), p. 86.
33 Kinotechnik, 11 (Feb. 20, 1929), p. 107.
34 Kinotechnik, 11 (Mar. 20, 1929), p. 147.
36 Trans. Soc. Mot. Pict. Eng., XIII, No. 37 (1929), p. 312.
* WM. STULL: Amer. Cinemat., 10 (Sept., 1929), p. 7.
37 Ger. Pal. 470,779; Fr. Pals. 32,865 (Addition to 633,405); 640,261; 640,866;
641,211; 642,986; 644,325; 645,744; 645,798; 646,621; 647,059; 648,016;
648,782; Brit. Pats. 303,354; 303,869; 305,215; 305,550; 306,424; 307,270;
Feb., 1930] PROGRESS REPORT 253
308,784; 308,839; 308,840; U. S.Pats. 1,698,106; 1,704,189; 1,707,625; 1,707,767;
1,708,087; 1,714,862; 1,716,463; 1,716,990.
38 P. HATSCHEK: Kinotechnik, 11 (July 20, 1929), p. 367.
39 Licht Bild Buhne, 21 (Nov. 3, 1928), p. 16.
40 Kinotechnik, 11 (Mar. 20, 1929), p. 145.
41 Ed. Screen, 8 (Apr., 1929), p. 105.
42 Kinotechnik, 11 (Apr. 20, 1929), p. 202.
43 Ger. Pat. 470,566.
44 E. M. W. SABRING: Internal. Phot., 1 (July, 1929), p. 12.
46 R. E. FARNHAM: Amer. Cinemat., 10 (May, 1929), p. 16; also WRIGHT and
EGELER: Trans. Soc. Mot. Pict. Eng., XIII, No. 38 (1929), p. 346.
46 O. K. OLSON: Amer. Cinemat., 10 (June, 1929), p. 14; also R. E. FARNHAM:
Ibid., 10 (July, 1929), p. 7, and Trans. II. Eng. Soc., 23 (Dec., 1928), p. 1241.
46a Amer. Cinemat., 10 (Aug., 1929), p. 21.
47 Amer. Cinemat., 10 (Apr., 1929), p. 13.
48 Kinotechnik, 11 (Apr. 20, 1929), p. 216.
49 Internat. Phot., 1 (Sept., 1929), p. 12.
50 Licht Bild Biihne, 22 (Jan. 19, 1929), p. 20; Ibid., 22 (Feb. 2, 1929), p. 19.
51 Ex. Daily Rev. & Mot. Pict. Today, 25 (June 1, 1929), p. 6.
62 J. M. FIDLER: Amer. Cinemat., 10 (Sept., 1929), p. 33.
63 R. E. NORMAN: Amer. Cinemat., 10 (May, 1929), p. 19.
64 J. DUBRAY: Amer. Cinemat., 9 (Sept., 1928), p. 11.
55 Ger. Pat. 466,607.
56 C. H. DUNNING: Amer. Cinemat., 10 (Apr., 1929), p. 18.
57 Amer. Cinemat., 10 (Apr., 1929), p. 20.
58 Amer. Cinemat., 10 (July, 1929), p. 37.
59 F. W. SERSEN: Amer. Cinemat., 10 (July, 1929), p. 31.
60 Ger. Pat. 466,347; U. S. Pats. 1,698,178; 1,703,818; 1,715,127; 1,715,510.
61 H. CROISE: Bioscope (Brit. Film No.) (1928), p. 267.
62 Internat. Phot., 1 (Aug., 1929), p. 16.
63 Mot. Pict. News, 40 (Sept. 7, 1929), p. 908; also Ex. Herald-World, 96
(Aug. 24, 1929), p. 39.
64 Mot. Pict. Div. U. S. Dept. Com. Report (Aug. 21, 1929).
65 L. W. PHYSIOC: Internat. Phot., 1 (Sept., 1929), p. 7.
66 B. /., 76 (Mar. 15, 1929), p. 149; Can. Pat. 289,343.
67 Kinotechnik, 11 (Apr. 20, 1929), p. 208.
68 T. A. MILLER: Internat. Phot., 1 (Aug., 1929), p. 32.
69 H. BOHM: Kinotechnik, 11 (Feb. 20, 1929), p. 90; also Wireless World (Apr.
10, 1929), and Bioscope (Supp.), 78 (Feb. 27, 1929), p. VII.
70 P. HATSCHEK: Kinotechnik, 11 (Aug. 20, 1929), p. 436.
71 Amer. Cinemat., 10 (Sept., 1929), p. 16; also Filmtechnik, 5 (Apr. 27, 1929),
p. 191.
72 Wireless World, 23 (Dec. 26, 1928), p. 842.
73 P. HEMARDINGUER: La Nature, No. 2814 (July 1, 1929), p. 107.
74 L. A. ELMER: Bell Lab. Record, 7 (July, 1929), p. 445.
75 P. HATSCHEK, Kinotechnik, 11 (July 5, 1929), p. 343.
7 P. HATSCHEK and E. LIHOTZKY: Kinotechnik, 11 (Mar. 20, 1929), p. 149.
77 A. KLAGES: Kinotechnik, 11 (July 20, 1929), p. 376; et seq.
254 PROGRESS REPORT [j. s. M. p. E.
78 P. HATSCHEK: Kinotechnik, 11 (May 5, 1929), p. 235.
79 E. T. PARIS: Phil. Mag., 5 (Mar., 1928), p. 489.
80 Prog. Report. Supp. Acad. Mot. Pict. Arts & Sciences (Aug. 20, 1929), p. 7.
81 Bull. Acad. Mot. Pict. Arts and Sciences, No. 25 (Sept. 25, 1929), p. 1.
82 H. C. HUMPHREY: Trans. Soc. Mot. Pict. Eng., XIII, No. 37 (1929), p. 158.
83 K. F. MORGAN: Trans. Soc. Mot. Pict. Eng., XIII, No. 38 (1929), p. 268.
84 Can. Pats. 288,442; 288,817; 288,818; Fr. Pats. 641,854; 645,010; 645,648;
646,625; Brit. Pats. 301,391; 301,730; 304,672; 3C5,245; 305,466; 3C6,438;
306,565; 307,078; 307,348; 309,676; U. S. Pats. 1,698,536; 1,700,833; 1,707,243;
1,708,523; 1,710,677; 1,713,726; Australian Pat. 10,585 of 1927.
85 A. JACKSON: Bioscope (Brit. Film No.) (1928), p. 221.
86 Amer. Cinemat., 10 (May, 1929), p. 14; also F. O. GRAVES: Trans. Soc. Mot.
Pict. Eng., XIII, No. 38 (1929), p. 303.
87 F. G. BANGS: Bioscope (Brit. Film No.) (1928), p. 70.
88 Witham, W. J.: Bioscope (Brit. Film No.) (1928), p. 72.
89 Bioscope, (Brit. Film No.) (1928), pp. 99-117.
90 Ex. Herald-World, 96 (Sept. 14, 1929), p. 35.
91 Amer. Cinemat., 10 (May, 1929), p. 23.
92 W. VINTEN: Bioscope Supp., 77 (Dec. 12, 1928), p. vi.
93 Kinotechnik, 11 (Aug. 20, 1929), p. 442.
94 A. and L. LUMIERE and A. SEYEWETZ: Sci. Ind. Phot., 8A (Dec., 1928), p. 126.
95 VON BARSY, A.: Kinotechnik, 11 (Jan. 20, 1929), p. 40.
96 H. W. MOYSE and D. R. WHITE: Internal. Phot., 1 (July, 1929), p. 20.
97 H. C. CARLTON and J. I. CRABTREE: Amer. Cinemat., 10 (July, 1929), p. 17,
et seq; also Trans. Soc. Mot. Pict. Eng., XIII, No. 38 (1929), p. 4C6.
98 K. CHIBISSOFF: Kinotechnik, 11 (May 5, 1929), p. 227, et seq.
99 J. F. Ross and J. I. CRABTREE: Amer. Phot., 23 (May, 1929), p. 254.
100 J. I. CRABTREE and H. A. HARTT: Amer. Cinemat., 10 (Sept., 1929), p. 3;
Trans. Soc. Mot. Pict. Eng., XIII, No. 38 (1929), p. 364.
101 R. GARRIGA: El. prog.fot., 10 (Mar., 1929), p. 61.
102 L. P. CUSRC: B. J., 76 (May 24, 1929), p. 300.
-Ger. Pat. 472,096.
104 Br. Pat. 308,653.
106 O. DEPUE: Trans. Soc. Mot. Pict. Eng., XIII, No. 37 (1929), p. 150.
106 R. E. NAUMAN: Amer. Cinemat., 10 (June, 1929), p. 32.
107 Amer. Cinemat., 10 (Aug., 1929), p. 23.
m Ger.Pats. 473,070; 474,599; Brit. Pats. 308,360; 308,361; 308,693; U.S.
Pats. 1,704,785; 1,714,203; 1,716,033; 1,716,417; Fr. Pats. 32,679 (Addition to
620,977); 640,921.
109 M. ADAM: Kinotechnik, 11 (Feb. 5, 1929), p. 68.
110 L. R. LOEFFLER: Amer. Cinemat., 10 (June, 1929), p. 19.
111 Bioscope (Supp.), 78 (Mar. 20, 1929), p. xii.
112 Brit. Pat. 301,676.
113 Fr. Pat. 648,015.
114 U. S. Pat. 1,701,048.
116 Fr. Pat. 647,113.
116 Ger. Pat. 469,538.
117 S. JASIENSKI: Phot. Ind., 27 (Jan. 16, 1929), p. 73.
Feb., 1930] PROGRESS REPORT 255
118 Ex. Herald-World, 95, Sect. 1 (May 11, 1929), p. 26.
119 Amer. Cinemat., 10 (May, 1929), p. 40.
120 Film Daily (Aug. 11, 1929), p. 11.
121 Amer. Cinemat., 10 (Aug., 1929), p. 17.
122 U. S. Pat. 1,697,858; Brit. Pats. 305,681; 305,726.
123 Amer. Projectionist, 7 (Feb., 1929), p. 17.
124 Kinotechnik, 10 (Dec. 20, 1928), p. 650.
126 Bioscope (Supp.), 79 (May 15, 1929), p. xiii.
126 Mot. Pict. Projectionist, 2 (Dec., 1928), p. 33.
127 Amer. Cinemat., 10 (Aug., 1928), p. 40.
128 Sci. et Ind. Phot., 9A (Apr., 1929), p. 41.
129 Amer. Cinemat., 9 (Feb., 1929), p. 28.
130 Fr. Pat. 641,260; Brit. Pats. 305,130; 306,126; 309,869; U. S. Pats.
1,702,302; 1,708,521; 1,711,977; 1,713,663; 1,713,939; 1,714,461; 1,714,461;
1,716,322.
131 Mot. Pict. News, 39 (Feb. 2, 1929), p. 316.
132 E. LEHMANN: Kinotechnik, 10 (Dec. 20, 1928), p. 635.
133 Licht. Bild Buhne, 22 (Jan. 5, 1929), p. 22.
134 H. JOACHIM: Kinotechnik, 11 (Jan. 20, Feb. 5, 1929), pp. 33 and 59.
136 Ger. Pat. 473,443; Fr. Pats. 640,706; 643,959; 647,101; U. S. Pats. 1,700,656;
1,717,234; Brit. Pats. 304,425; 306,719.
136 U. S. Pats. 1,709,017; 1,716,361; 1,716,756.
137 FR. PATZEI/T: Kinotechnik, 11 (Aug. 20, 1929), p. 423.
138 Mot. Pict. News, 40 (Aug. 17, 1929), p. 655.
139 Ex. Daily Review & Mot. Pict. Today, 26 (Sept. 21, 1929), p. 6.
140 Kinemat. Weekly, 147 (May 9, 1929), p. 21.
141 Ex. Herald-World, 96 (Sept. 21, 1929), p. 32.
142 Ex. Daily Review & Mot. Pict. Today, 26 (July 6, 1929), p. 14.
143 R. H. CRICKS: Kinemat. Weekly, 148 (June 6, 1929), p. 72.
144 Kinemat. Weekly, 142 (Dec. 20, 1928), p. 55.
145 R. H. CRICKS: Kinemat. Weekly, 148 (June 13, 1929), p. 60.
146 Mot. Pict. News, 40 (Aug. 17, 1929), p. 652.
147 Mot. Pict. News, 39 (May 18, 1929), p. 1699.
148 Bioscope (Supp.), 79 (Apr. 10, 1929), p. ix; also Ibid., 79 (May 1, 1929), p. vi.
149 Kinemat. Weekly, 147 (May 2, 1929), p. 59.
150 G. SCHUTZ: Ex. Herald-World, 94, Sect. 2 (Mar. 16, 1929), p. 37; see also
Mot. Pict. News, 40 (Sept. 7, 1929), p. 878.
161 Ex. Herald-World, 94, Sect. 2 (Mar. 16, 1929), p. 50.
162 Ex. Herald-World, 94, Sect. 1 (Feb. 16, 1929), p. 44.
153 p rog Report, Acad. Mot. Pict. Arts & Sciences, Aug. 20 (1929), pp. 2 and 4.
153a Mot. Pict. News, 40 (Oct. 5, 1929), p. 1195.
154 Fr. Pat. 647,253; Ger. Pat. 456,872; Can. Pats. 288,816; 289,022; U. S.
Pats. 1,695,048; 1,7C6,731; 1,708,410; 1,708,533; 1,713,503; Brit. Pats. 301,872;
304,705; 305,617; 306,404; 306,426; 307,514; 309,183; 309,208.
155 Mot. Pict. News, 40 (Sept. 7, 1929), p. 894.
156 M. RITTERATH: Amer. Cinemat. 10 (Apr., 1929), p. 10.
157 H. E. IVES, /. Opt. Soc. Amer., 18 (Feb., 1929), p. 118.
256 PROGRESS REPORT* [J. s. M. p. ti.
"* Fr. Pat. 640,273; Brit. Pats. 303,067; 308,596; U. S. Pats. 1,705,760;
1,714,849.
159 R. HOCK: Kinotechnik, 11 (Feb. 5, 1929), p. 66.
160 L. BURMESTER and E. MECHAU: Kinotechnik, 10 (Aug. 5, 20; Sept. 5, 1928),
pp. 395, 423, 447.
161 R. THUN: Kinotechnik, 11 (May 20, 1929), p. 255.
162 P. HATSCHEK: Amer. Cinemat., 9 (Sept., 1928), p. 18.
163 H. IVARSON: Kinotechnik, 11 (Aug. 20, 1929), p. 425.
Fr. Pats. 641,109; 643,818; Brit. Pats. 308,945; 309,448; 309,655; U. S.
Pats. 1,699,169; 1,699,833; 1,707,498.
' Ex. Herald-World, 95, Sect. 2 (May 11, 1929), p. 41.
166 Brit. Pat. 309,801; Fr. Pats. 642,604; 647,437; 648,109; U. S. Pats.
1,701,564; 1,703,891; 1,713,921; 1,717,063.
167 U. S. Pat. 1,715,158.
168 Film Daily, 48 (June 30, 1929), p. 15.
169 Bioscope (Supp.}, 79 (June 12, 1929), p. viii.
170 Kinotechnik, 11 (Jan. 5, 20, 1929), pp. 20, 48.
171 Kinemat. Weekly, 145 (Mar. 14, 1929), p. 93.
172 Fr.Pats. 640,612; 641,597; Brit. Pats. 302,452; 304,656; 304,913; 304,975;
305,888; U. S. Pats. 1,701,590; 1,714,550.
ma Film Daily, 48 (June 28, 1929), p. 1.
173 Report from Mot. Pict. Div. U. S. Dept. Com. (Sept. 4, 1929), p. 2.
174 C. SYLVESTER: Kinemat. Weekly, 146 (Apr. 4, 1929), p. 63.
175 D. Fox: Ex. Herald-World, 95, Sect. 2 (Apr. 13, 1929), p. 20.
176 L. G. APPLEBEE: Kinemat. Weekly, 147 (May 2, 1929), p. 37.
177 A. T. HENLY: Kinemat. Weekly, 144 (Feb. 14, 1929), p. 89.
178 E. BERLINER: /. Frank. Inst., 208 (July, 1929), p. 13, et seq.
179 T. E. FINEGAN: Trans. Soc. Mot. Pict. Eng., XIII, No. 38 (1929), p. 324.
180 R. B. BONNEY: Mountain States Monitor, 23 (April, 1929), p. 26.
181 New York Times, Sect 2 (July 28, 1929).
182 Rev. franc. Phot., 10 (July 15, 1929), p. 223.
183 B. /., 76 (June 14, 1929), p. 354.
184 W. STULL: Amer. Cinemat., 10 (June, 1929), p. 16.
186 L. M. BAILEY: Movie Makers, 4 (Apr., 1929), p. 223.
186 R. THUN: Kinotechnik, 11 (Jan. 20, 1929), p. 42.
187 Brass World, 25 (May, 1929), p. 111.
188 Ed. Screen, 8 (May, 1929), p. 139.
189 Ed. Screen, 7 (Nov., 1928), p. 228.
190 Ed. Screen, 8 (Jan., 1929), p. 9.
191 O. M. FOKERT, Ed. Screen, 8 (Mar., 1929), p. 76.
192 J. J. STUTZIN: Kinotechnik, 11 (July 5, 1929), p. 350.
193 E. HAUSER: Kinotechnik, 11 (Aug. 20, 1929), p. 427.
194 V. GOTTHEINER and K. JACOBSOHN: Phot. 2nd., 27 (June 5, 1929), p. 627.
195 Photo-Era, 62 (May, 1929), p. 274.
M H. C. MCKAY: Photo-Era, 62 (May, 1929), p. 284.
197 Kinotechnik, 11 (Apr. 20, 1929), p. 216.
198 FRIEDEL: Kinotechnik, 11 (Mar. 5, 1929), p. 115.
199 Report Mot. Pict. Div. U. S. Dept. Com. (Sept. 11, 1929), p. 1.
et>., 1930] PROGRESS REPORT 257
200 Report Mot. Pict. Div. U. S Dept. Com. (Aug. 28, 1929), p. 2.
201 Ex. Herald-World, 94 (Feb. 9, 1929), p. 35.
20ia Ex. Herald-World, 96 (Sept. 14, 1929), p. 32.
202 Electrical Review, 103 (Dec. 21, 1928), p. 1075.
203 Fr. Pat. 646,420.
204 Photo-Era, 62 (March, 1928), p. 161.
205 K. F. MATHER, Ed. Screen, 8 (Feb., 1929), p. 36.
206 L. M. BAILEY, Movie Makers, 4 (Mar., 1929), p. 178.
207 F. BECK, Kinotechnik, 11 (Mar. 5, 1929), p. 124.
208 F. BECK, Kinotechnik, 11 (Apr. 5, 1929), p. 179.
209 G. MAISER and H. UMBEHR: Kinotechnik, 11 (July 20, 1929), p. 379.
210 R. THUN: Kinotechnik, 11 (July 20, 1929), p. 383.
211 Sri. Ind. Phot. 10 (March, 1929), p. 35.
212 Sri. Amer., 141 (July, 1929), p. 27.
213 Barrons' Weekly (Sept. 16, 1929), p. 18; also Ex. Herald-World, 96 (July 6,
1929), p. 70.
214 G. B. BROWN: Internal. Phot., 1 (Sept., 1929), p. 34.
215 P. TIETZE: Kinotechnik, 11 (Feb. 20, 1929), p. 99.
216 Brit. Pats. 304,632; 308,973; 309,113; 309,504; Ger. Pats. 469,502; 467,711.
217 Fr. Pate. 640,118; 640,133: 640,139; Brit. Pats. 301,732; 303,170; 303,356;
303,357; 304,643; 304,669; 307,351; 308,320; U. S. Pat. 1,707,157.
218 U. S. Pats. 1,700,617; 1,700,618.
219 W. T. CRESPINEU,: Internal. Phot., 1 (Aug., 1929), p. 30.
220 Kinemat. Weekly, 145 (Mar. 21, 1929), p. 69.
221 Fr. Pat. 644,803; and Kinemat. Weekly, 144 (Feb. 21, 1929), p. 58.
222 Can. Pat. 290,031; Fr. Pat. 646,693; Ger. Pats. 465,458; 466,327; 469,416;
Brit. Pats. 303,262; 306,328; 306,329; 307,659; U. S. Pats. 1,697,194; 1,699,226;
1,700,252; 1,700,616; 1,707,699; 1,707,709; 1,707,710; 1,707,825; 1,712,439;
1,716,989.
223 Film fur Alle, No. 14 (Dec., 1928).
Cine Kodak News, 6 (Aug., 1929), p. 6.
225 Movie Makers, 4 (May, 1929), p. 332.
226 Amat. Phot., 67 (Jan. 9, 1929), p. 28.
227 B. J., 76 (Aug. 16, 1929), p. 488.
228 Phot. Dealer, 43 (Jan., 1929), p. 34.
229 Film fur Alle, 3 (Apr., 1929), p. 108.
230 Amat. Phot., 67 (Apr. 24, 1929), p. 342.
231 Photo-Era, 62 (Mar., 1929), p. 167.
232 Amat. Phot., 67 (June 12, 1929), p. 506.
233 Filmo Topics, 5 (June, 1929), p. 5.
234 H. C. MCKAY: Amer. Phot., 23 (Jan., 1929), p. 16.
236 H. C. MCKAY: Movie Makers, 4 (Mar., 1929), p. 151.
236 H. C. MCKAY: Photo-Era, 62 (Mar., 1929), p. 172.
I 237 Movie Makers, 4 (Mar., 1929), p. 195.
238 Movie Makers, 4 (June, 1929), p. 408.
239 E. S. GODDARD: Phot. J., 69 (Feb., 1929), p. 80.
240 Ed. Screen, 8 (Mar., 1929), p. 94.
241 Film fur Alle, 3 (May, 1929), p. 141.
258 PROGRESS REPORT
242 Film fur Alle, 3 (May, 1929), p. 139.
243 P. HATSCHEK, Kinotechnik, 11 (Aug. 20, 1929), p. 192.
244 Amat. Films, 1 (June, 1929), p. 223.
245 Kinotechnik, 11 (Apr. 5, 1929), p. 192.
248 Brit. Pat. 304,366; U. S. Pat. 1,708,372.
247 Filmo Topics, 5 (Feb., 1929), p. 5.
248 Photo-Era, 62 (Feb., 1929), p. 114.
249 B. J., 76 (June 7, 1929), p. 337.
250 Movie Makers, 4 (May, 1929), p. 337.
261 Phot. Dealers, 43 (Apr., 1929), p. 196.
252 Amer. Cinemat., 10 (Aug., 1929), p. 37.
253 H. E. C. FURSIER: Amat. Phot., 67 (May, 1929), p. 381.
264 Austral. Photo-Review, 36 (Apr., 1929), p. 181.
255 Amer. Phot., 23 (Jan., 1929), p. 46.
256 Amer. Cinemat., 10 (June, 1929), p. 39.
257 U. S. Pat. 1,708,370; 1,708,371.
268 U. S. Pat. 1,709,341.
259 Mot. Pict., 5 (June, 1929), p. 3.
2 > Mot. Pict., 5 (May, 1929), p. 3.
261 Ex. Herald-World, 94 (Feb. 16, 1929), p. 28.
262 N. D. GOLDEN: Report Mot. Pict. Div. U. S. Dept. Com. (Aug. 5, 1929).
263 N. D. GOLDEN: Ex. Herald-World, 95, Sect. 2 (May 11, 1929), p. 71; also
Ed. Screen, 8 (March, 1929), p. 75.
264 Film Daily, 49 (July 29, 1929), p. 7, et seq.
265 H. FRAINKEL: Bioscope, 78 (Feb., 20, 1929), p. 28.
266 Phot. Ind., 26 (Sept. 12, 1929), p. 952.
267 Kinemat. (Supp.), 143 (Jan. 31, 1929), p. 7.
ABSTRACTS
Selenophone: A Variable Area Sound Film Device. P. HATSCHEK. Kino-
technik, 11, Aug. 20, 1929, pp. 436-8. A description of the general principles of
the Selenophone sound film system. The torsion galvanometer employed con-
sists of a transverse vibrating metal band in a strong magnetic field. The motion
of an illuminated slit attached to the vibrating band is optically magnified 100
times and recorded on the film. For reproduction the "condenser" type of
selenium cell is used. The change of resistance of selenium cells upon illumination
is known to be accompanied by considerable lag, the greatest lag occurring when
the light is decreased. This undesirable property of the selenium cell can be com-
pensated largely by the use of an amplifier vacuum tube operated during the lag
period. With the rapid light fluctuations and such an arrangement, the fatigue
of the selenium cell is also minimized. The exact details of the compensation
method employed in the Selenophone have not been made public.
Talkies Have a Past! J. F. RIDER. Mot. Pict. News, 39, Mar. 2, 1929,
p. 627. A brief description of the outstanding discoveries which made sound
motion pictures possible. In 1857, M. Leon Scott made the first record of sound
vibrations. Sound was first recorded and reproduced by Edison in 1877 in a tin-
foil record; the process was improved by Bell and Tainter in 1887 who used wax
records. In 1889 Bmil Berliner patented the disk record which, with improve-
ments, is now in use. The change in resistance of selenium with change of light
intensity was first observed in the 19th century by May, the operator of the Ire-
land terminal of the transatlantic cable. Interest in the sensitivity of selenium
and an effort to overcome the lag in its response caused much investigation which
ultimately produced the photo-electric cell. This cell was improved by deForest
in 1907 who produced the vacuum amplifying tube.
Running the Talkies. XXII. Naturetone. R. H. CRICKS. Kinemat. Weekly,
150, Aug. 15, 1929, p. 69. Comments on the Naturetone equipment for the
reproduction of disk-recorded sound. Separate turntables must be used for low
speed and high speed records. The speed control is described and stated to be
satisfactory. The sound is to be recorded on cylinders in place of the usual disks.
Sound-proof Studios. Kinemat. Weekly, 150, Aug. 22, 1929, p. 54. The con-
struction of the new sound-proof studio of the British Talking Pictures is described.
To exclude exterior noises and prevent internal reverberation, air-spaced concrete
walls are used, with an inner shell of sound absorbing material. The floor is laid
on thick felt runners, with a layer of plastic material [bitumen Abstr.] adhering
to the underside of the boards. There is a tank 33 by 32 ft. sunk in the studio
floor, arranged for underwater shots. The studio is 120 by 93 ft. in size, stated
to be the largest of its kind in Europe. Production lighting is incandescent.
[The wiring of the lighting system is arranged in a false ceiling, and all leads
and lamps will be dropped from galleries above the studio so leaving the floor
clear. Abstr.]
Acoustical Control of Theater Design. H. I,. COOKE. /. Frank. Inst., 208,
259
260 ABSTRACTS [J. s. M. p. .
September, 1929, pp. 319-24. By proper adaptation of ceiling design to the
design of the rest of the auditorium it is possible to provide all members of the
audience seated beyond 2 /s the distance from front to back with equally clear
reception. In general the longitudinal vertical median section of the computed
ceiling shows increasing curvature toward the back of the hall. The visual and
acoustical advantages of having the vertical sections of the auditorium surfaces
through the stage conform to the equation r = e a9 are pointed out.
Mazdas Make Good in Severe Studio Test. Mot. Pict. News, 39, April 6,
1929, p. 1055. In the lighting of a large set in the sound picture, Broadway,
three 163 units were used which had a connected load of 33,000 amperes. The
main set was 170 ft. long and 125 ft. wide and with 4 auxiliary sets made a total
length of 220 ft. For the color sequences, a maximum of 22,000 amp. was re-
quired; for black and white work, 17,000 amp. A large electrical crane was used
for many of the camera shots. The boom of the crane was 25 ft. long and it was
mounted on a steel column 12 ft. high. Rapid upward or circular movements were
possible with the equipment, which had a circular platform, 5 ft. in diameter at
the end, for the camera equipment and operators.
Properties and Use of Hypersensitized and Panchromatic Negative Film. K.
JACOBSOHN. Kinotechnik, 10, April 5, 1928, pp. 175-83. A summary of pre-
vious work, giving the literature references, on hypersensitizing with ammonia,
ammoniacal silver chloride solutions; color sensitizing with pinaflavol-pinacyanol
and pinachrome-pinachrome violet. Other subjects treated are the use of infra-
red sensitized film; the development of night exposures on hypersensitized film in
a special pyro developer to avoid glaring high-light contrast; and tone rendering
with panchromatic materials. References to the literature are given.
Method for the Measurement of the Effective Transparency of Photographic
Objectives. J. HRDLICKA. Compt. rend., 189, July 22, 1929, pp. 153-5. The
author advocates photographic photometry for determining the effective trans-
parency of a photographic objective and quotes an instance in which this value
does not check with the maker's // value within a reasonable amount.
Maximum Light Flux Obtainable in Kine Projection. H. NAUMANN. Kino-
technik, 10, 1928, p. 523. The theoretical maximum of illumination obtainable
with the mirror-arc system, taking into account the effects of size of source, type,
and aberrations of mirror and projection lens aperture, has been closely approached
in practice. Owing to the smaller surface intensity and the presence of the glass
bulb, tungsten filament lamp-mirror systems cannot be made to give more than
about one-sixth of the light flux of arc systems.
Muybridge's Motion Pictures. L. F. RONDINEU,A. J. Frank. Inst., 208,
September, 1929, pp. 417-20. The author, who was an assistant of Muybridge,
defends the latter's claim as inventor of motion pictures. He takes exception to
some statements made by Leffmann. Leffmann appends a reply stating that
Heyl exhibited motion pictures in 1870.
Kinematography in the Service of Medicine. E. DEGNER. Phot. Korr., 64,
1928, p. 347, p. 378. In addition to an enumeration of various medical subjects
in which motion picture photography has been of value, there is a description of
von Rothe's apparatus and that of Brusten. The former is constructed as far as
possible in a room above the operating theater. The camera is mounted on an
arm suspended vertically through the ceiling. The main disadvantages are cost
Feb., 1930] ABSTRACTS 261
and limitation to normal speeds. Brusten's apparatus is mounted on a counter-
balanced lever on a movable stand. Pictures can be made from almost any
angle and speeds up to 100 per second are possible.
Goal of Photographic Optics. A. SONNEFELD. Phot. Korr. 64, 1928, p. 376.
Because of light losses due to reflection and absorption, the useful limit of aperture
has been reached with lenses of ordinary types of f/2 to //1. 5. Such lenses,
however, have the defect of not being perfectly zonally corrected. Nonspherical
refracting surfaces (Abbe surfaces) might remove the defect and result in fewer
components and less light absorption.
New Actinometer. Luminous Source of Constant Spectral Composition. R.
LANDAU. S. & J. P. Inf. Cine., 8, 1928, p, 131; 9, 1929, p. 5. An image of the
subject is formed on a phosphorescent screen. A mirror placed clear of the ob-
jective axis is inclined so that light received from the surface is reflected in a di-
rection parallel to that of the light from the objective. This light consists of
polychromatic reflected light and monochromatic light due to phosphorescence.
A shutter is so placed that it will allow the light from the objective to reach the
screen but will intercept the reflected image light from the mirror. The shutter
will allow the phosphorescent light to pass intermittently. The phosphorescent
light is of constant spectral composition and is proportional to the actinic light
in the image. The phosphorescent image light may be inspected with a photo-cell.
BOOK REVIEWS
Proceedings of the Seventh International Congress of Photography. Edited
by W. CLARK, T. SLATER PRICE, AND B. V. STORR. Illustrated papers. W.
He/er and Sons, Ltd., Cambridge, England, 1929. XII + 571 pp. On July
9-14, 1928, the Seventh International Congress of Photography met in London
and this volume is a record of the proceedings. The material is presented under
three section heads the first of which contains the majority of papers. In this
section scientific applications, theory, and motion picture photography are in-
cluded. The other two sections contain excellent material in their subject classi-
fications, pictorial photography, history, bibliography, and legal questions. The
Proceedings may be regarded, in spite of the lack of a complete index as a valuable
reference book in general photography. The material of special interest to motion
picture photographers, however, makes up only a small portion of the book. In
this section matters of standardization which are of importance to the industry
as a whole are discussed. Some of the recommendations arising out of these dis-
cusions are as follows: Maximum thickness for negative should be 0.175 mm.
Maximum displacement of perforations on opposite edges of film should be 0.05
mm. Positive perforation should be Kodak standard and negative Bell and
Howell standard. Light change marks for printing are specified to be 38 mm.
long and 1.4 mm. deep starting at the splice. They are to be placed on the right
hand side of the negative as it is held with the picture inverted and emulsion side
toward the observer. Negative film should be supplied wound emulsion outward
on metal centers of specified dimensions. It is impractical to attempt a compre-
hensive review of the many valuable papers of general interest in photographic
theory. Some features may be mentioned however. Toy and Weigert have given
valuable contributions to the theory of the latent image. Jones and Hall have pre-
sented an empirical relation which represents the failure of the reciprocity law
with great accuracy. Jones and Russell have suggested a new method of ex-
pressing plate speeds.
Motion Picture Photography. C. L. GREGORY. Folk Publishing Co., Inc.,
New York City, 1927, $6.00. 435 p. Second edition. Few changes have been
made in this new edition of this textbook of the New York Institute of Photog-
raphy although there has been considerable progress noted in the industry since
the publication of the first edition in 1920. New material has been added in a
chapter on color motion pictures, with a very brief description of progress in stereo-
scopic and sound pictures. A useful section is the added chapter on "Some Typ-
ical Motion Picture Cameras," which gives specifications of the leading standard
cameras of American manufacture. Descriptions of British, French, and German
cameras would have increased the value of this chapter. A glossary of common
cinematographic terms has been included. Examination of the bibliography
shows that several new books have been omitted. The illustrations are
interesting although with the wealth of beautiful "stills" available it would
seem that some of the old pictures might well have been left out of this edition.
262
BOOK REVIEWS
263
These faults are minor, however, compared to the wealth of material contained
iji the work.
Motion Picture Work on Substandard Film. (Die Schmalfilm-Kinemato-
graphie.) O. P. HERRNKIND. A. Hartleben, Vienna, 1929, $2.00. 175 p. A
general review of the whole subject. The various substandard films on the mar-
ket, and the apparatus used for exposure and projection are described. A con-
siderable amount of attention is paid to the methods by which an amateur can
finish his own pictures. There is a chapter on trick film work. The whole book
is a compilation, and does not contain much original material derived from per-
sonal experience.
SOCIETY OF MOTION PICTURE
ENGINEERS
OFFICERS
President
J. I. CRABTREE, Eastman Kodak Co., Rochester, N. Y.
Past President
L. C. PORTER, Edison Lamp Works, Harrison, N. J.
Vice-Presidents
H. P. GAGE, Corning Glass Works, Corning, N. Y.
K. C. HICKMAN, Eastman Kodak Co., Rochester, N. Y.
Secretary
R. S. BURNAP, Edison Lamp Works, Harrison, N. J.
Treasurer
W. C. HUBBARD, Cooper-Hewitt Electric Co., Hoboken, N. J.
Board of Governors
R. S. BURNAP, Edison Lamp Works, Harrison, N. J.
H. T. COWLING, Eastman Teaching Films, Inc., 343 State St.,
Rochester, N. Y.
J. I. CRABTREE, Research Laboratory, Eastman Kodak Co.,
Rochester, N. Y.
H. P. GAGE, Corning Glass Works, Corning, N. Y.
K. C. HICKMAN, Research Laboratory, Eastman Kodak Co.,
Rochester, N. Y.
W. C. HUBBARD, Cooper-Hewitt Electric Co., Hoboken, N. J.
W. C. KUNZMANN, National Carbon Company, Cleveland, Ohio.
D. MACKENZIE, Bell Telephone Labs., 463 West St., New York,
N. Y.
P. MOLE, Mole-Richardson, Inc., 941 N. Sycamore Ave., Holly-
wood, Calif.
L. C. PORTER, Edison Lamp Works, Harrison, N. J.
S. ROWSON, Ideal Films, Ltd., 76 Wardour St., London, W. 1,
England.
E. I. SPONABLE, Fox-Hearst Corp., 460 West 54th St., New York,
N. Y.
264
265
COMMITTEES
1929-1930
Convention
W. C. KUNZMANN, Chairman
J. W. COFFMAN W. C. HUBBARD M. W. PALMER
R. S. BURNAP
Journal
. A. JONES, Chairman
J. W. COFFMAN
H. T. COWLING
W. C. HUBBARD
Membership and Subscription
H. T. COWLING, Chairman
C. BARRELS
L. W. DAVEE I. ROSEMAN
J. W. BOYLE
W. H. CARSON
W. CLARK
J. DEFRENES B. C. SCHMITZ
B. R. GEIB J. L. SPENCE
J. KLENKE F. ZUCKER
M. L. MISTRY
B. B. NORRISH
Papers
J. W. COFFMAN, Chairman
M. C. BATSEL C. R. HANNA G. B. MATHER
F. J. CADENAS K. C. HICKMAN R. F. NICHOLSON
J. A. DUBRAY B. HusE J. B. TAYLOR
O. M. GLUNT D. HYNDMAN
Progress
G. B. MATTHEWS, Chairman
J. A. BALL R. B. FARNHAM R. C. HUBBARD
W. CLARK H. B. FRANKLIN G. F. RACKETT
A. W. DANESHEW K. GEYER S. K. WOLF
J. B. BNGL A. C. HARDY
H. W. DREYER
G. C. BD WARDS
T. FAULKNER
C. GREENE
F. C. BADGLEY
Projection
N. M. LAPORTE, Chairman
H. GRIFFIN W. B. RAYTON
R. H. McCuLLOUGH H. B. SANTEE
W. A. MCNAIR L. M. TOWNSEND
R. MIEHLING D. F. WHITING
Publicity
W. WHITMORE, Chairman
B. W. DEPUE
G. B. MATTHEWS
G. F. RACKETT
O. A. Ross
266 COMMITTEES [J. S. M. p. E.
Solicitation
B. P. CURTIS, Chairman
J. W. COFFMAN B. A. WlLLIFORD
Standards and Nomenclature
A. C. HARDY, Chairman
M. C. BATSEL P. H. BVANS W. B. RAYTON
W. H. CARSON H. GRIFFIN V. B. SEASE
A. DEBRIE R. C. HUBBARD T. B. SHEA
L. DEFOREST L. A. JONES J. P. SPENCE
J. A. DUBRAY N. M. LAPORTE B. I. SPONABLE
B. W. BNGSTROM W. P. POWERS L. T. TROLAND
G. F. RACKETT
Studio Lighting
A. C. DOWNES, Chairman
L. J. BUTTOLPH R. B. FARNHAM M. W. PALMER
K. C. HICKMAN
Theater Lighting
C. B. BGELER, Chairman
F. A. BENFORD F. FALGE B. HUSE
A. C. DOWNES R. B. FARNHAM L,. A. JONES
C. GREENE
LONDON SECTION
SIMON ROWSON, Chairman
A. NEWMAN, Vice-Chairman PAUL KIMBERLEY, Manager
L. BVELEIGH, Secretary ALAN WILLIAMSON, Manager
H. WOOD, Treasurer WILLIAM VINTEN, Manager
PACIFIC COAST SECTION
P. MOLE, Chairman C. DUNNING, Manager
G. F. RACKETT, Sec.-Treas. B. HUSE, Manager
Membership Committee
J. COURCIER, Chairman
B. JEWELL
Papers and Programs
B. HUSE, Chairman
Feb., 1930]
SOCIETY NOTES
267
LIST OF NEW MEMBERS AND TRANSFERS
BERTRAM J. BACH (Transfer to Active}
Prov. of Ontario Pictures, Toronto,
Ont, Canada
DONALD P. BENNETT (A)
Home Talkie Machine Corp., 220
West 42nd St., New York, N. Y.
ROBERT CARULLA 04)
Fox-Hearst Corp., 460 West 54th
St., New York, N. Y.
CHARLES W. GLOVER (-4)
Abbey House, Westminster, London,
S. W. 1, England
JAMES K. HALL (A)
Kodak, Ltd., Wealdstone, Middle-
sex, England
NOTIS A. KOMNENOS 04)
Stanley Co. of America, llth &
Market Sts., Philadelphia, Pa.
HENRY V. LAWLEY (M)
The Lawley Apparatus Co., Ltd.,
26 Church St., Charing X Road,
London, W. 1, England
GEORGE S. C. LUCAS (A]
British Thomson-Houston Co., Ltd.,
Rugby, England
ALLEYNE W. MANCHEE (M)
Audio-Cinema, Inc., 161 Harris
Ave., Long Island City, N. Y.
WALTER A. MACNAIR (M )
Bell Telephone Labs., Inc., 463 West
St., New York, N.Y.
CARL HUBERT NIEPMANN (A)
Korting & Mathieson Electrical,
Ltd., 711 Fulham Road, London,
S. W. 6, England
CLAUDE F. PARKINS (A)
Studio Film Labs., Ltd., 80 Wardour
St., London, W. 1, England
GEORGE E. PATTON (Transfer to
Active)
Ontario Govt. Motion Picture Bu-
reau, Toronto, Ont., Canada
ARTHUR J. SANIAL (M)
Fox-Hearst Corp., 460 W. 54th St.,
New York, N. Y.
LAURENS A. TAYLOR (M)
General Electric Company, Schenec-
tady, New York
CECIL V. THORNTON (A)
British International Pictures, Els-
tree, Herts, England
JOHN A. TRANTHAM (M)
Standard Kine Labs., Inc., Rythe
Works, Thames-Ditton, England
SYDNEY WAKE (M}
Standard Kine Labs., Ltd., 49
Greek St., London, W. 1, England
ARTHUR J. WHITEHEAD (A)
Filmophone, Ltd., 101 Wardour St.,
London, W. 1, England
WILL WHITMORE (4)
Western Electric Co., 50 Church St.,
New York, N. Y.
SOCIETY NOTES
The Bulletin. The happenings of the Society to date have been
published in the Society's Bulletin which has been issued at infre-
quent intervals. With the appearance of the new Journal, the publi-
cation of the Bulletin will be discontinued and the doings of the
Society will be reported in these columns.
The Journal. It is apparently not clear to several members that
with the issuing of the new Journal the publication of the Transactions
268 SOCIETY NOTES [j. s. M. P. E.
will be discontinued. The Society members, of course, will receive
twelve copies of the Journal instead of four issues of the Transactions.
The domestic and foreign price of the Journal is $12.00 per year
to non-members and $1.50 per copy to members or non-members.
Board of Governors Meeting. At the last Board of Governors meet-
ing held on November 8th in New York City, a large number of
business matters were transacted including the following.
1. A final revision of the By-Laws was made which will be printed and circulated
to the Active members previous to the spring convention when they will be voted
upon for final approval.
2. It was resolved that for the time being no advertising material shall appear
in the JOURNAL. Whether such a policy will be continued indefinitely will depend
upon whether sufficient sustaining memberships can be obtained to take care of
the financial necessities of the Society.
3. The duties of the Chairman of the Papers Committee were defined as fol-
lows, (a) To secure papers for regular meetings, (b) To approve papers prior
to their presentation at meetings, (c) To supply abstracts in length not ex-
ceeding 10 per cent of the entire article for distribution by the Chairman of the
Publicity Committee.
4. It was resolved that material approved by the Chairman of the Papers Com-
mittee and presented at a regular meeting cannot afterward be withheld from
publication in the Society's Journal without the approval of the Board of Gover-
nors.
5. A motion was made and passed that papers presented at regular meetings
shall not be published or circulated but shall be considered as the confidential
property of the Society prior to their appearance in the JOURNAL.
6. It was resolved that the Board of Editors and Chairman of the Papers Com-
mittee shall prepare an instruction booklet for authors of manuscripts and that the
Chairman of the Standards and Nomenclature Committee shall prepare and print
in the JOURNAL a list of the complete standards adopted, with recommended prac-
tices and other material prepared by the Standards and Nomenclature Committee
to date, and that 200 reprints of this booklet be prepared for distribution by the
Secretary.
Solicitations Committee. This committee under the chairmanship
of Mr. B. P. Curtis, is endeavoring to secure sustaining memberships
of $100, $500, or $1000 which it is hoped the various concerns will
take up in order to provide the Society with the funds necessary for
conducting its business. The annual dues and entrance fees barely
take care of the present expenses of the Society. It will be necessary
to appoint a permanent editor to replace the temporary editor,
Mr. L. A. Jones, but before this can be done a sufficient income must
be secured to provide for a first class editor and manager who will
Feb., 1930] SOCIETY NOTES 269
take over a large part of the routine work now done by the Secretary
and Treasurer.
An Omission. In the leaflet distributed with the ballot for a loca-
tion for the spring meeting, the Convention Committee inadvertently
omitted to acknowledge the assistance rendered by the Academy of
Motion Picture Arts and Sciences during the Hollywood convention
two years ago. The Academy not only placed their rooms at our
disposal throughout the entire convention but Mr. Frank Woods and
his assistants gave unstintingly of their time, while the banquet
tendered by the Academy was unquestionably the finest formal func-
tion ever arranged in honor of our Society.
The Pacific Coast Section. Under the capable and enthusiastic
leadership of Mr. Peter Mole, the Pacific Coast Section is planning
a series of important meetings for the coming year. The first meeting
was held in the Norman Bridge Laboratory of Physics at the Pasa-
dena Institute of Technology, when Dr. W. T. Whitney gave a talk
on "The Nature of Light and Color." Although Pasadena is a con-
siderable distance from Hollywood, an attendance of 65 was recorded.
Lectures dealing with wide film, laboratory practice, stereoscopy, and
television are planned for the future.
The London Section. Our fellow members in London have been
holding and plan to continue fortnightly meetings during the coming
year. In the meeting rooms of the Royal Photographic Society on
October 28th, Mr. Fetter gave a talk on "Some Aspects of the Western
Electric Recording System." Thirty-seven were present.
On January 18th, Mr. Hodgson described a method of kaleidoscopic
cinematography and this was followed by an open discussion on
sound recording problems.
The London section is assisting the Historical Committee of the
parent Society in securing data on the accomplishments of Mr.
Eugene Lauste. Some of the members of the London section assisted
in making some of Mr. Lauste's early apparatus.
Suggestions. Although the business of the Society is conducted by
the Board of Governors, they do not have a monopoly of ideas. Your
president would greatly appreciate any suggestions from Society
members. Suggestions on subjects for papers, the manner of con-
ducting conventions, and material for publication in the JOURNAL are
vitally necessary for the welfare of the Society and the Industry.
270 SOCIETY NOTES
NOTICE TO MEMBERS
Please make sure that your name and address as they appear on
our records are correct. Inspect the address label of the JOURNAL
folder or the published membership list.
Names of those who were members prior to November 1, 1929, are
published in the Transactions, Vol. XII, No. 37 (1929) p. 7.
Names of new members appear in this issue of the Journal.
In case of error kindly write at once to the secretary, Mr. R. S.
Burnap, 5th and Sussex Streets, Harrison, N. J.
Membership Badge in ^|&2fll^ Replacements may be
white and gold given f!3f^W^^B obtained from William C.
each member upon pay- &^_l^h^Ll^f Hubbard, Treasurer, at a
ment of dues. IB Vr^^B ^r charge of $1.00.
Certificate of Membership in the Society of Motion Picture Engineers.
Obtainable by Members from R. S. Burnap, Secretary, at a charge of $1.00.
Membership
in the
Society of Motion
Picture Engineers
is open to all who are engaged
in any branch of the motion
picture industry or allied
work. The society is inter-
national in character and its
convention papers with com-
plete discussions are furnished
free to members.
REASONS WHY
.YOU
SHOULD JOIN
The Society of
Motion Picture
Engineers
1 The S. M. P. E. is an internation-
ally recognized organization of
Motion Picture Engineers.
2 The S. M. P. E. is becoming an
ever more important factor in de-
veloping, stabilizing, and standard-
izing the motion picture industry.
3 At two conventions each year reli-
able data concerning a wide range
of subjects are presented long be-
fore they become available else-
where.
4 Papers read at conventions are
printed with full discussions in
a monthly Journal and distributed
free to all members.
5 The S. M. P. E. affords unique op-
portunities for personal contact
with leaders in the industry.
6 S. M. P. E. publications are recog-
nized standard authority on Mo-
tion Picture Engineering.
7 The S. M. P. E. will help you in
many ways. Join now.
COUPON
HERFORD TYNES COWLING, Chairman
Membership Committee, Society of Motion Picture Engineers
343 State Street, Rochester, N. Y.
Dear Sir
Please mail application blank and requirements for membership in the S. M. P. E. to
Name. . .
(Please print)
Position .
(Company or other Affiliation)
Street and City Address
Name
Position
Street and City Address.
JOURNAL
OF THE SOCIETY OF
MOTION PICTURE ENGINEERS
LOYD A. JONES, EDITOR pro tern.
Associate Editors
G. L. CHANIER P. MOLE S. E. SHEPPARD
O. M. GLUNT W. B. RAYTON J. L. SPENCB
A. C. HARDY P. E. SABINE L. T. TROLAND
Volume XIV MARCH, 1930 Number 3
CONTENTS
Page
The Surface Treatment of Sound Film
J. I. CRABTREE, OTTO SANDVIK, AND C. E. IVES 275
Characteristics of High Intensity Arcs
D. B. JOY AND A. C. DOWNES 291
A Year of Sound HAROLD B. FRANKUN 302
The Optics of Motion Picture Projectors .... ARTHUR C. HARDY 309
Multiple Exposure Cinematography in Sound Pictures
WILLIAM STULL 318
The Illusion of Sound and Picture JOHN L. CASS 323
Film Numbering Device for Cameras and Recorders
M. W. PALMER 327
Water Cooling of Incandescent Lamps N. T. GORDON 332
The Development of Television and Radiomovies to Date. . . .
C. FRANCIS JENKINS 344
A New Method of Blocking Out Splices in Sound Film
J. I. CRABTREE AND C. E. IVES 349
A Light Intensity Meter J. L. McCoY 357
A New Synchronizing Apparatus for 16 Mm. Films with Disk
Records WM. H. BRISTOL 361
Abstracts 366
Book Reviews 370
Officers 371
Committees 372
Resignations 374
Change of Address 374
Published Monthly by the
SOCIETY OF MOTION PICTURE ENGINEERS
20th & Northampton Sts., Easton, Pa.
Editorial Office: 343 State St., Rochester, N. Y.
Subscription to non-members $12.00 per year, single copies $1.50. Order from
the Secretary of the Society of Motion Picture Engineers, 5th & Sussex Streets,
t Harrison, N. J.
Copyright
BY THE SOCIETY OF
MOTION PICTURE ENGINEERS
PERMANENT MAILING ADDRESS OF THE SOCIETY
Engineering Societies Building
29 West 39th Street
New York, N. Y.
Papers or abstracts may be reprinted if credit is given to the Journal of the
Society of Motion Picture Engineers.
The Society is not responsible for statements made by authors.
Application pending for entry as second-class matter at the Post Office at
Easton, Pa.
THE SURFACE TREATMENT OF SOUND FILM*
J. I. CRABTREE, OTTO SANDVIK, AND C. E. IVES
Practical experience has shown that with newly processed motion
picture positive prints it is necessary to apply some form of lubricant
to the film surface in order to facilitate the passage of the film through
the projector. Sound record prints require similar lubrication in which
case it is very necessary that the applied lubricant should not be the
cause of extraneous noise in the projector-reproducer mechanism.
In an earlier communication 1 it has been shown that the so-called
ground noise is due to scratches, dirt, dust, and finger marks on the
film. It is therefore desirable to protect the sound record in such a
manner that it is not damaged by the accumulation of those factors
which are responsible for excessive ground noise. The problem of a
suitable surface treatment therefore resolved itself into the devising of:
1. A suitable method of lubricating sound film which would not
increase ground noise.
2. A method of treating either the entire film surface or the sur-
face of the sound record area so as to reduce to a minimum its ten-
dency to become scratched and accumulate dirt during projection
and thereby retard the accumulation of ground noise on repeated pro-
jection.
3. If possible, a method of treatment combining methods 1 and 2.
I. THE LUBRICATION OF SOUND FILMS
Effects of Lack of Lubrication. As stated in a previous communica-
tion 2 the gelatin emulsion of a newly developed positive print is very
adherent to hot metal surfaces, and the adhesion of the film to the
hot gate or pressure shoes in the projector causes small particles of
gelatin to be rubbed off the film. Some of these particles become
pressed together to form a crust which increases greatly the resistance
to travel of the film through the gate. After these crusts form, the
* Communication No. 413 from the Kodak Research Laboratories.
1 SANDVIK, OTTO: "A Study of Ground Noise," Trans. Soc. Mot. Pict. Eng. t 12,
No. 35 (1928), p. 790.
2 CRABTREE, J. I., AND IVES, C. E.: "The Lubrication of Motion Picture Film,"
ians. Soc. Mot. Pict. Eng., 11, No. 31 (1927), p. 522.
275
276 CRABTRBK, SANDVIK, AND IVES [J. S. M. P. E.
film is no longer held flat but oscillates in and out of the focal plane
with the well-known "in and out" of focus effects. Also, since the
film is in a condition of varying strain between the intermittent
sprocket and the projection aperture, the projected picture is un-
steady. A similar action at the sound aperture causes a flutter in the
volume and frequency of the sound.
Effects of Wrong Lubrication. -A large quantity of paraffin or other
wax applied to the edges of the film prevents adhesion between the
film and gate surfaces but the wax falls off in flakes when the roll is
rewound after being wound up in a warm condition. Particles of
wax then lodge on the sound track with deleterious effects and ac-
cumulate in the reproducer slit or aperture, diminishing the volume of
reproduced sound and in some cases cutting off the sound com-
pletely. Some treatments to which film is subjected for the sup-
posed purpose of lubricating it have still worse effects and actually
introduce noise and shorten the useful running life of the film.
A Satisfactory Method of Lubrication. Previous work on the lubri-
cation of motion picture film has shown that a suitable application of
paraffin wax gives the best lubrication. In an earlier communica-
tion 2 on this subject a process of application of wax over the entire
emulsion surface was described which required the use of a combined
wax applicator and buffing machine. A mixture of paraffin and car-
nauba wax dissolved in a non-inflammable solvent was applied to the
film surface which was then buffed, for otherwise the waxed surface
remained dull and diffusing. This treatment was found to give a
satisfactory degree of lubrication together with protection of the
whole surface against abrasions and oil markings.
This treatment is not ideal for sound prints, because, in order to
obtain a high degree of lubrication, it is necessary to use a large pro-
portion of paraffin and this produces a surface which is rather suscep-
tible to finger markings and which collects dust particles readily. It
resists scratching, however, and dirt and scratches are largely con-
fined to the wax layer which can be removed by a cleaning solvent.
The present method of applying a thin line of molten wax along
the edge of motion picture film is open to the following objections:
1. The quantity of wax applied is not readily capable of control.
2. The wax is applied in a narrow, but thick ridge, which must be
spread out by the pressure pads in the projector.
3. The method is subject to certain accidents in operation which
render its use less dependable than could be desired. If the waxer
is used before the wax is sufficiently warm or if a draft of cold air strikes
March, 1930] SURFACE TREATMENT OF SOUND FlLM
277
the applicator, the viscosity of the wax is increased by virture of
being cooled and too much wax is applied.
It was found that paraffin wax could be applied to the perforation
area of motion picture film in the form of a solution of the wax in a
non-inflammable solvent such as carbon tetrachloride. It is not
necessary to buff the waxed film in this area after evaporation of the
solvent because the optical condition of the edge is of little importance.
FIG. 1. The wax solution applicator.
The thickness of the applied film can be controlled readily by changing
the concentration of the solution.
In order to test the suitability of this method, various concentra-
tions of the paraffin solution were applied to sound record prints and
these were tested by running through a projector-reproducer machine
and noting whether wax flaked off or accumulated in the machine.
Similarly treated samples were run on projection machines until com-
plete breakdown of the film in order to determine their comparative
resistance to wear.
Equipment for Application of Wax Solution. The first device used
for application of the wax solution to the edges of motion picture film
onsisted of two smooth, steel disks which dipped partly in the wax
lution contained in a small tank. The film was led over these disks
278 CRABTREE, SANDVIK, AND IVES [J. S. M. p. E.
with the emulsion side down and then carried through the air for a
sufficient distance to permit the carbon tetrachloride to evaporate
completely before the wind-up was reached. The applicator rollers
were driven by the film passing over them. No other roller was per-
mitted to touch the edges of the film, where the paraffin had been
coated, until the solvent was completely evaporated. A photograph
of this equipment is shown in Fig. 1. The film is held by the idler
rollers against the applicator disks (A) which dip into the solution in
tank (T). The film travels from left to right and passes directly
into the drying tube (D) through which a stream of warm air is passed
in the direction opposite to the film travel. In this tube the carbon
tetrachloride is evaporated rapidly. The film next enters a similar
tube through which cold air is forced, in order to solidify the paraffin
which is soft when it leaves the hot tube. Disks of various widths
were tried and a width of 0.15 inch was finally chosen. It was con-
sidered advisable to apply the lubricant to as much of the area re-
quiring lubrication as is possible without encroaching on the sound
track. If the applicator roller extends 0.15 inch inward from the
edge of the film these conditions are satisfactorily fulfilled.
When this equipment was first tried the disks were so mounted as
to turn freely on the shaft and were driven by the film, which was
drawn through the device by a drive roller located after the drying
tubes. With this method of driving some difficulty was experienced
as a result of the application of too much solution. Experiments
were made with other applicator surfaces and means for driving the
applicator disks. The preferred method of application was by means
of the above steel disks so driven that their peripheral speed was one-
half to one-quarter of the film speed.
Satisfactory disks were also constructed by clamping a disk of
leather or other porous fibrous material between two thin metal disks
of slightly smaller diameter.
Quantity of Paraffin Applied. Concentrations of paraffin in carbon
tetrachloride varying from 10 to 0.5 per cent were applied to devel-
oped positive motion picture film. If the solution was applied in
considerable quantity, concentrations of one per cent or greater dried
very slowly. If the concentration was less than one per cent drying
was not difficult, a few feet of drying tube being sufficient.
Table I shows the results of wear and tear tests made on film lubri-
cated by the method described above in comparison with an untreated
sample and two samples lubricated with molten paraffin.
March, 1930] SURFACE TREATMENT OF SOUND FlLM 279
No method of lubrication has been found which gives longer pro-
jection life before complete breakdown of the film than the molten
paraffin treatment used for comparison in these tests but the pro-
jection life is as great with the paraffin solution treatment as with the
molten wax method.
A small amount of wax accumulated in the projector gate when a
film treated with a solution which applied 0.3 gram of paraffin per
1000 feet of film was projected. This amount was therefore consid-
ered somewhat excessive even though no evidence was given that any
interference with sound reproduction might come from it. There-
T ABLE I
Results of Wear and Tear Tests
Method of Lubrication
Wearing Properties
None
Molten paraffin test No. 1
Molten paraffin test No. 2
Paraffin solution
0.15 gram wax per 1000 ft. film
0.30 gram wax per 1000 ft. film
100%
408%
380%
407%
423%
fore, the safe limit was considered to be 0.15 gram per 1000 feet of
film. It will be seen from the table that the degree of lubrication
given by this quantity of paraffin is equal to that given by 0.3 gram
within the error of measurement.
Control of the Rate of Application of Wax. The concentration of the
wax solution to be used depends largely upon the quantity to be ap-
plied, although there are definite practical limits to the useful concen-
tration. When using the applicator as first built, that is, with the
disks running at the same peripheral speed as the film, a rather large
volume of liquid was applied so that it was necessary to use a dilute
solution (0.25 per cent). This method was discarded because the
liquid accumulated in drops which dried slowly and showed some ten-
dency to run out of the perforation area. When the apparatus was
so modified that the peripheral speed of the disks was less than the
speed of travel of the film, less liquid was applied and it was neces-
sary to use a stronger solution (one per cent). With the more even
distribution of the liquid produced by the rubbing effect where slip-
page occurred between the film and disks, the coating dried very
easily. With the hot air tube three feet long and the cold air tube
280
CRABTREE, SANDVIK, AND IVES
[J. S. M. P. E.
about four feet, and with five feet of travel in the open air, the ma-
chine could be operated at a speed of fifty feet of film per minute.
With the applicator blades traveling at one-third this speed, the
quantity of solid wax applied amounts to only about 0.10 gram per
1000 feet of film. Projection tests with such lubricated films showed
that the wax 'did not encroach on the sound track nor did it tend to
accumulate in the aperture of the reproducer mechanism, thus fulfilling
requirement No. 1 outlined on page 275.
II. SURFACE TREATMENT TO RETARD ACCUMULATION OF GROUND NOISE
In order to determine the type of material that appeared most
promising from the standpoint of surface protection, several groups of
materials were selected differing widely in their physical properties.
These can be classified as materials which when applied in thin layers
to the film emulsion formed a hard surface, such as various types of
lacquers, or a smooth and more or less plastic surface such as is given
TABLE II
Treatment Accorded Film Samples
Sample
Treatment
91
Surface waxed with 1.0% cantol wax in carbon tetrachloride,
92
buffed, and edge-waxed with a solution of paraffin in carbon
93
tetrachloride
102
94
Buffed and edge-waxed with 1.0% solution of paraffin in carbon
95
tetrachloride
96
97
Edge- waxed in 1.0% solution of paraffin in carbon tetrachloride
100
Cantol surface waxed with 0.25% cantol wax in carbon tetra-
101
chloride
103
Plain film
106
Oiled with a 2.0% solution of light motor oil in carbon tetra-
107
chloride and buffed
110
111
Treated with special lubricant containing 0.9% paraffin wax
112
and 0.5% light motor oil dissolved in carbon tetrachloride
by various types of waxes and oils. Experiments were also made
on hardening the surface by treating it with formalin solutions. The
ground noise of these samples was then measured in a manner similar
to that described in an earlier communication. l After measurement,
the samples were cinched by winding the film into a loose roll and
March, 1930] SURFACE TREATMENT OF SOUND FlLM 281
pulling it up tight on the core or by pushing the roll out from the
center into a cone. These procedures, called longitudinal and coni-
cal cinching, respectively, provide a quick and fairly dependable
method for determining the wearing quality of the film. The noise
level of the samples was again measured after cinching.
Ground noise increased only slightly after cinching the plain buffed
film, thus showing that this treatment renders the film surface less
susceptible to scratches and abrasions. Hardening the gelatin by
bathing in a solution of formalin did not reduce the rate of accumula-
tion of ground noise. Three different lacquers were also tested but
were not found beneficial. Solution edge- waxing showed a slight
protective effect but treatment of the whole emulsion surface with
oils and waxes gave the best results.
From these preliminary experiments the processes showing most
promise from the standpoint of retarding the rate of accumulation of
ground noise were selected for a more extensive investigation. For
this purpose, a number of samples of motion picture positive film two
hundred feet long were processed in the regular manner and treated
as indicated in Table II.
The Waxing and Buffing Operation. The combined operation of
applying a solution of wax in a volatile solvent to the emulsion surface
of the film and then buffing the waxed surface to produce a high gloss
has been described and illustrated in a previous paper. 2 The opera-
tion is briefly as follows. The film is passed over a revolving roller
which is continuously wetted with a dilute solution of the wax in car-
bon tetrachloride. This solution dries on the film immediately and
the emulsion surface is then polished to a high gloss by the action of
four cloth buffers. Film is treated in this process at the rate of about
30 feet per minute.
The Buffing Operation. In the buffing operation the wax applica-
tion is omitted. A noticeable gloss is imparted to the film surface
under these conditions.
The Edge Lubrication. In the tests tabulated above, application of
a 1.0 per cent paraffin solution to the edge of the film was carried out
as described in Part I. This treatment applied about 0.3 gram of
paraffin per 1000 linear feet of film.
Noise Level Tests with Projected Films. The noise level of each of
these samples was measured in the customary manner. l Each sample
was projected ten times and rewound after each projection with a
constant speed rewind. The projector was rechecked at frequent
282
CRABTREE, SANDVIK, AND IVES
[J. S. M. P. E.
intervals to insure that it was working properly and that the pressure
shoes and other parts were in correct adjustment. After ten projec-
tions each sample was remeasured. After ten runs, the samples were
divided into groups for further treatment, as indicated in Table III.
TABLE III
Treatment of Various Samples after Ten Runs
Sample
Treatment
91
Wiped with clean plush
92
94
96
QC
100
Cleaned on the cleaning machine with carbon tetrachloride
106
110
112
93
95
Q7
QQ
Cleaned on the cleaning machine with carbon tetrachloride and
101*
the original treatment repeated with each sample
107
111
102
No treatment
103
* This sample was not cleaned but merely bathed with the original treating
solution.
The Cleaning Operation. Cleaning of the test samples was carried
out with a slightly modified cleaning machine described previously. 3
The modification consists in the use of two tanks of cleaning solution
instead of one. The film passes from the feed reel with the emulsion
face downward into the first tank A, Fig. 2, under an idler roller and
over the plush covered roller P, then under a second idler, and then out
of this tank. The plush covered roller is driven by the film and is
partially immersed in the cleaning liquid. As it revolves at a very
high speed it throws a shower of solvent against the film. Also the
pressure between the film and the roller wrings the liquid out of the
cloth and forces it along the film surface. In this way a very gentle
3 CRABTREE, J. I., AND CARLTON, H. C.: "Cleaning Liquids for Motion Picture
Film," Trans. Soc. Mot. Pict. Eng., 11, No. 30 (1927), p. 277.
March, 1930] SURFACE TREATMENT OF SOUND FlLM
283
but thorough scouring is given to the emulsion surface. At the point
where the film leaves the first tank a single squeegee is located to pre-
vent the more or less dirty liquid being carried in a large quantity into
the tank B. New cleaning liquid is introduced in tank B and then
transferred to tank A so that the film is finally rinsed in clean liquid.
Bach sample, except Nos. 102 and 103, was again measured and the
procedure repeated after projecting for 20, 30, 40, 50, 82, and 130
times, respectively.
The results of these measurements are shown in Table IV where the
ume level of a 2000 cycle constant frequency as 100. When the film
FIG. 2. Diagram of the cleaning machine.
relative ground noise volume levels are expressed in terms of the vol-
samples were being measured, this constant frequency was measured
at frequent intervals, as a check on the constancy of the photo-cell
and the amplifier.
The excellence of the different treatments included in Table IV is
shown in Table V in the order of their decreasing merit.
The values in Table IV are expressed graphically in Fig. 3. From
the curves and Table IV it is seen that samples Nos. 91, 93, 102, 107,
and 111 were very satisfactory and much better than any of the others.
Sample No. 102 (cantol wax, buffed, and solution edge-waxed) shows
the very permanent protective effect found in the preliminary study.
It is noteworthy that this sample was neither cleaned nor re- treated.
Also, a clean dry plush can be used repeatedly for cleaning this surface
284
CRABTREE, SANDVIK, AND IVES
[J. S. M. p. E.
without harm as shown by test No. 91. Excellent results were also
obtained by cleaning and re-treating a film originally treated with
cantol wax, buffed, and solution edge- waxed although, if a film is not
given abusive treatment during use, this repeated treatment should not
be necessary.
The results shown by tests Nos. 107 (oil treated and buffed) and
111, in which a solution of oil and paraffin wax was used instead
TABLE IV
Relative Ground Noise Intensity
Number of Runs
Sample
10
20
30
40
50
82
130
CF
100
100
100
100
100
100
100
100
91
0.30
0.45
0.70
0.78
0.90
0.92
1.03
1.20
92
0.37
0.50
0.63
0.75
1.10
2.20
3.60
5.13
93
0.45
0.77
0.90
0.98
1.05
1.10
1.25
1.45
94
0.27
0.60
1.45
3.65
4.77
5.50
6.80
7.75
95
0.30
0.80
1.12
1.35
1.56
1.75
2.25
2.83
96
0.20
1.75
2.65
3.30
3.82
4.35
5.85
7.90
97
0.30
1.48
2.45
3.20
3.85
4.40
5.86
7.45
100
0.45
0.95
1.65
2.45
3.22
3.93
6.01
8.90
101
0.28
2.02
2.60
2.83
2.94
3.03
3.20
3.33
102
0.30
0.48
0.61
0.75
0.85
0.93
1.10
1.25
103
0.50
3.45
4.67
5.47
6.02
6.43
7.30
8.05
106
0.50
0.90
2.35
3.45
4.28
4.85
5.81
6.33
107
0.32
0.88
1.05
1.14
1.20
1.25
1.30
1.37
110
0.50
1.35
3.35
4.63
5.45
6.07
7.45
8.87
111
0.43
0.92
1.00
1.00
1.00
1.00
1.00
1.00
112
0.65
1.40
2.85
4.03
4.93
5.55
6.72
7.53
of the oil solution, were very satisfactory. Such processes, however,
involving frequent re-treatments are objectionably complicated.
Preliminary study has shown that oily coatings tend to accumulate
dirt somewhat rapidly and this is shown by a study of sample No.
107 before and after treatment.
Sample No. 92 is a rather interesting case in that a sufficient quan-
tity of wax and paraffin remained on the film to offer protection until
the fourth cleaning after which the ground noise increased to such
an extent that a repetition of the original treatment was considered
imperative after three cleanings.
It was concluded that the best treatment consisted in the applica-
tion of a solution of cantol wax to the entire emulsion surface, buffing
March, 1930] SURFACE TREATMENT OF SOUND
285
to a high gloss, and then coating a solution of paraffin on the edges for
lubrication.
Sample No. 95 which was simply buffed and then edge-waxed with
a paraffin solution is the next in order of choice. This sample was
cleaned and re- treated after every ten runs.
As a third choice, No. 101, which was merely bathed on the clean-
ing machine in a solution of carbon tetrachloride containing 0.25 per
1C 20 30 40 50 60 70 80 90 100 110 120 130
SO 90 100 IK) HO 130
FIG. 3. Curves showing change in relative ground noise volume level with
continued projection.
cent of cantol wax when new and cleaned in the same solution after
every ten projector runs, offers a moderate degree of protection with-
out requiring the use of a polishing machine in the first treatment or in
the after treatments.
A slight degree of protection was effected by the treatments indi-
cated in Table VI.
It is noteworthy that with the edge lubrication treatment (Nos. 96
and 97) there was a definitely lower rate of ground noise accumulation
than with an untreated film (No. 103).
No protection whatever could be noticed in the case of sample
280
CRABTREE, SANDVIK, AND IVES
TABLE V
Comparative Value of Various Treatments
[J. S. M. P. E.
Sample
Treatment
102
91
111
93
107
92
Cantol buffed-Sol No after treatment
Cantol buffed-Sol Wiped with plush
Special lubricant Re-treatment*
Cantol buffed-Sol Re-treatment*
2.0% oil buffed Re-treatment*
Cantol buffed-Sol Clean
95
Plain buffed-Sol Re-treatment*
101
0.25% cantol no buff Re-treatment**
106
2.0% oil buffed Clean only
96
97
100
Sol Clean
Sol Clean and Re- treatment*
0.25% cantol no buff Clean
94
112
Buffed-Sol Clean only
Special lubricant not buffed Cleaned every 10 runs
103
Plain film
* Re-treatment signifies that the sample was cleaned as described and then
given the original treatment after every ten projection runs.
** Re-treatment consisted only of cleaning in a bath having the same formula
as the original treating solution.
Sol indicates edge- waxing with solution of paraffin wax in carbon tetrachloride.
No. 112 after the first ten runs. This is undoubtedly because the oily
protective surface was removed in the subsequent cleaning operations.
The results shown in the case of sample No. 94 would not favor the
use of plain buffing with solution edge-waxing if the film was cleaned
with carbon tetrachloride after every ten runs without re-waxing.
The ground noise of sample No. 103 which received no treatment in-
creased very rapidly in comparison with that of the tested samples.
TABLE VI
Treatments Giving Slight Protection
Sample
Description
96
97
100
106
Solution edge-waxed Cleaned after every 10 runs
Solution edge-waxed Cleaned and re-treated after every ten
runs
Bathed in 0.25% solution of cantol wax Cleaned after every
10 runs
Oil buffed Cleaned after every 10 runs
March, 1930] SURFACE TREATMENT OF SOUND
287
In Table VII the relative noise levels in decibels of each sample is
expressed in the terms of the volume level of the constant frequency.
This table shows for each case how much additional amplification is
required for the sound volume to equal that of the constant frequency
record. The constant frequency record was of variable area type and
of about 80 per cent modulation which of course is higher than the
average modulation in a record of music or speech. On the other hand,
TABLE VII
Volume Level in Decibels
Number of Runs
Sample
10
20
30
40
50
82
130
91
-25.2
-23.5
-21.5
-21.1
-20.5
-20.4
-19.9
-19.2
92
-24.3
-23.0
-22.0
-21.2
-19.6
-16.6
-14.4
-12.9
93
-23.5
-21.1
-20.5
-20.1
-19.8
-19.6
-19.0
-18.4
94
-25.7
-22.2
-18.4
-14.4
-13.2
-12.5
-11.7
-11.1
95
-25.2
-21.0
-19.5
-18.7
-18.1
-17.6
-16.5
-15.5
96
-27.0
-17.6
-15.8
-14.8
-14.2
-13.6
-12.3
-11.0
97
-25.2
-18.3
-16.1
-14.9
-14.1
-13.6
-12.3
-11.3
100
-23.5
-20.2
-17.8
-16.1
-14.9
-14.0
-12.2
-10.5
101
-25.5
-16.9
-15.9
-15.5
-15.3
-15.2
-15.0
-14.8
102
-25.2
-23.2
-22.1
-21.2
-20.7
-20.3
-19.6
-19.0
103
-23.0
-14.6
-13.3
-12.6
-12.2
-11.9
-11.4
-10.9
106
-23.0
-20.4
-16.3
-14.6
-13.7
-13.1
-12.4
-12.0
107
-24.9
-20.6
-19.8
-19.4
-19.2
-19.0
-18.9
-18.6
110
-23.0
-18.7
-14.8
-13.3
-12.6
-12.2
-11.3
-10.5
111
-23.7
-20 .4
-20.0
-20.0
-20.0
-20.0
-20.0
-20.0
112
-21.9
-18.5
-15.5
-13.9
-13.1
-12.6
-11.7
-11.2
CF
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
the noise level of the best samples is twenty-one decibels down after
eighty runs leaving a good margin between signal level and noise level.
The noise level of the untreated film, however, is only ten decibels
down after eighty runs, in which case the noise would be very objec-
tionable. The values of Table VII are shown graphically in Fig. 4.
It is well to emphasize at this point that in actual practice the ratio
of signal level to noise level would be considerably greater than that
shown in this table. The measuring system used responds to a much
greater range of frequencies than any actual sound reproducing sys-
tem. These measurements therefore include a large amount of
noise which would not be reproduced. Also, since these measure-
icnts were made on clear film, the noise level is somewhat enhanced.
288
CRABTREE, SANDVIK, AND IVES
[J. S. M. P. E.
SUMMARY AND PRACTICAL RECOMMENDATIONS
Sound record prints can be satisfactorily lubricated by applying a
thin coating of a solution of paraffin wax in carbon tetrachloride along
the edges of the film in the perforation area and drying. This treat-
ment is superior to the application of solid or molten wax inasmuch as
the wax does not flake off or encroach on the sound track during re-
winding or projection, which would produce ground noise.
The application of the wax is accomplished by means of two steel
disks which dip into the wax solution. The disks should be about 0. 15
W 20 30 40 50 60 70 80 90 KX> 110 l0 130 10 20 SO 40 50 O 70 80 *> 100 HO 110 130
-30
10 20 30 40 50 60 70 80 90 100 110 120 130
FIG. 4. Curves showing change in relative ground noise volume level in decibels.
inch wide and so spaced that they are in contact with the film from
the edge inward 0.15 inch so that the area lubricated will correspond
closely with that under the tension shoes in the projector gate. The
quantity of wax applied is varied by changing the rate of rotation of
the disks in relation to the speed of the film. For a film speed of 50
feet per minute, a disk 3 inches in diameter should so rotate that its
peripheral speed is about one-third this value when immersed one-
half inch in a 1.0 per cent solution of the wax. The quantity of wax
thus applied is about 0.30 to 0.35 gram per 1000 linear feet of film.
For higher speeds, the wax solution should be applied to the disks in
a suitable manner, such as by means of an application roller dipping
into the wax solution. After application the solvent is quickly evapo-
March, 1930] SURFACE TREATMENT OF SOUND FlUM 289
rated by passing the film through a short narrow tube through which
a current of air at 120 F. is blown.
An alternative method of lubrication is to apply a 1.0 per cent solu-
tion of light motor oil in carbon tetrachloride to the entire film surface
and then buff in a manner as described previously. 2
In addition to providing satisfactory lubrication, it is desirable to
treat sound record prints in such a manner that the film will have
during handling a minimum tendency to accumulate scratches, dirt,
dust, and finger marks which in turn cause ground noise. Several
suitable methods of treatment have been evolved, the most satis-
factory of which consists in applying a one per cent solution of cantol
wax to the entire emulsion surface of the film, buffing, and edge-wax-
ing as described above. The cantol wax provides a hard smooth
surface which in itself has poor lubricating properties but the edge-
waxing supplies the necessary lubrication. A film treated in this
manner eventually becomes scratched but the scratches are usually
confined to the wax coating and do not reach down to the silver image
so that by removing the wax coating at intervals by cleaning with
carbon tetrachloride and re-waxing, the image is maintained clean
and free from scratches.
Three machines are necessary for the above treatment, namely:
(a) the waxing and buffing machine, (&) the edge-waxing machine, and
(c) the cleaning machine. Machine (b) can be attached to the end of
machine (a) but it would be inefficient to attach machine (c) to ma-
chine (a) plus (b) because the former can be run at a speed of 200 feet
per minute while it would not be desirable to run machine (a) at a
speed greater than 30 feet per minute unless more buffing wheels were
attached.
Although in some of the experiments outlined the treated film was
cleaned and re- treated after projecting 10 times, in practice this rou-
tine is usually not necessary, the treated film requiring cleaning only
when indicated by the presence of visible dirt, oil spots, or excessive
ground noise. In the case of the tests with the cantol buffed and edge-
waxed sample, after projecting 130 times without further treatment of
any kind the magnitude of the ground noise was only slightly greater
than at the start. The projectors were kept in a very clean condition
throughout the tests. This test demonstrates that it is possible to
keep the projector sufficiently clean and the rewinder free from dust so
that with film treated in the manner outlined no excessive ground
noise is produced after 130 runs.
290 CRABTREE, SANDVIK, AND
In the absence of the surface waxing treatment with newly proc-
essed prints it is imperative either to edge-wax as recommended or
to pass the film through a cleaning machine using a 0.5 per cent solu-
tion of light motor oil in carbon tetrachloride in the second tank, the
first tank being by-passed. This treatment will apply a thin film of
lubricating oil to the entire film surface which will assist in preventing
the accumulation of ground noise although, in view of the slightly
tacky nature of the oiled surface, the film will accumulate dust and
dirt more rapidly than cantol waxed film and will require cleaning and
retreating frequently.
The authors are indebted to Mr. D. B. Hyndman for assistance in
the experimental work.
Note. Since the above experiments were completed it has been
found that sound record film may be satisfactorily edge-waxed by
using a 10 per cent solution of paraffin in carbon tetrachloride and
rotating the application disks so that the peripheral speed is about
one-twelfth the speed of the film. With this procedure no auxiliary
drying apparatus is necessary.
DISCUSSION
MR. DICKSON: Did you run samples of film through the carbon tetra-
chloride forty or fifty times in these tests?
DR. SANDVIK: No, we cleaned some of the samples as many as seven times.
MR. DICKSON: Does treatment with carbon tetrachloride make the film
brittle?
MR. CRABTREE: If carbon tetrachloride is pure, and reputable commercial
samples are pure and free from sulphur, the film is not affected. If sulphur
compounds are contained in it, the image is eventually toned brown.
MR. RICHARDSON: Recently I received a complaint from a New York City
exhibitor that his projectors were continually damaging film. I found that the
aperture tension was abnormally high so high that 145 feet of film per minute
could be projected with no over-shooting. High tension is the primary cause
of excessive film wear and of the deposition of emulsion on the tension shoes.
This difficulty could be remedied by the projector manufacturer. If he would
provide a tension adjustment, theaters requiring a ninety foot per minute pro-
jection speed would not abuse the film to the extent they now do.
MR. CRABTREE: I don't know whether Mr. Richardson heard the first part
of the paper. The object of the treatment is to enable you to get "green" film
through the projector, and this method ensures that you cannot get too much
wax on it. Molten wax is all right if it is put on correctly but usually it is not.
The second object is to prevent the accumulation of ground noise, which you
notice could be produced by conically cinching the film. The matter of the
tension of the shoes has nothing to do with this.
CHARACTERISTICS OF HIGH INTENSITY ARCS
D. B. JOY AND A. C. DOWNES*
INTRODUCTION
The amount of light used at the aperture plate of the motion pic-
ture projector has steadily increased until at the present time only
the high intensity arc can furnish the light concentration necessary
to satisfy the demands of the larger theaters. Recent changes which
have been made and rumors of others about to occur in the motion
picture industry have again emphasized the constant demand for
more light on the screen of the theater. It therefore seems desirable
to call attention to certain characteristics of high intensity arcs which
may help in the solution of the ever present problem of increasing
the useful light.
The light from a high intensity arc emanates from two distinct
sources, the crater and the tail flame. The tail flame produces about
thirty per cent of the total light from this type of arc but is of no
value for projection because it cannot be focused on account of its
large size, shape, and position. Therefore, in a consideration of the
characteristics of the high intensity arc only the crater light should
be studied. The characteristics should include candle power both
directly in front of the arc and at various angles, the area of crater
opening, intrinsic brilliancy, and spectral energy distribution for the
various carbon sizes and operating currents.
The literature 1 to 8> mc ' contains angular distributions of candle
power, spectral energy curves, and values of intrinsic brilliancy,
but in many cases the conditions under which they were obtained
and the identification of the carbons are not clear. The spectral
energy distribution curves for high intensity arcs given in the Bureau
of Standards Scientific Paper No. 539 were obtained at the given cur-
rents and voltages but include the tail flame light. These curves are
therefore only of value as a means of comparison, for practically none
of the tail flame is picked up by the optical system of the high inten-
sity equipment used for the projecting or taking of motion pictures.
* Research Laboratories of National Carbon Co., Inc., Cleveland, Ohio.
291
292
D. B. Jov AND A. C. DOWNES
EXPERIMENTAL PROCEDURE
[J. S. M. P.
An arrangement for measuring the candle power and intrinsic
brilliancy of the high intensity arcs is shown in Fig. 1. The arc is
placed directly facing the comparison plate D. Between the arc and
comparison plate are the shields A and B. C is a black box which
contains the comparison plate.
The light from the crater passes through the holes in screens A and
B, and is reflected from the comparison plate D to the Macbeth illu-
minometer E. The function of screen A is to cut out the light from
the tail flame, negative carbon, and negative arc stream. The hole
in this screen is approximately 1 to 2 millimeters larger in diameter
than the crater. This allows clearance enough to take care of any
FIG. 1. Apparatus for measuring crater light.
slight change in position of the positive carbon while rotating, and
gives a clear field approximately 1.5 inches in diameter on the com-
parison plate. The light from the small part of the tail flame which
is included by this clearance is negligible. This was demonstrated
by tests with larger and smaller openings in screen A. Screen B
shields the operator of the illuminometer from the crater light. The
hollow tube projecting from the side of the box furnishes the neces-
sary opening for the illuminometer. The correct position of the
crater with respect to screen A and the comparison plate is checked
by means of the substitution of a false back with an opening slightly
larger than the field of view of the comparison plate, and a telescope
F placed at the back of the opening, as shown in the figure. The
angular distribution in a horizontal plane was obtained by rotating
the lamp about the crater as the axis. The size of the crater opening
was obtained by measuring the craters of carbons which had been
March, 1930]
HIGH INTENSITY ARCS
293
burned at the various currents. The intrinsic brilliancy was calcu-
lated from the above data by the usual method.
The spectral energy distribution curves were made with prac-
tically the same set-up for excluding light other than that from the
crater. They were made with a quartz spectroradiometer used in
connection with a thermopile with calibrated transmission screens,
140000
120000
100000
80000
60000
40000
20000
o
NA
TIOM
u. HIGH
INTEND
Y OB(
)N5
CANDLE
POWEI
\ OF a
vs.
:URI?EN
:TER
LIGHT
V
T
1
X
I3.
MM>
X,
X
^x
X
9MM.
^ j _^-
-<:
^
^
""'^
30 60 70 80 90 100 110 120 130 140 150 16C
CURRENT
FIG. 2. Candle power of crater light vs. current.
according to the procedure described by Coblentz 6 and Greider and
Downes. 9
DISCUSSION OF RESULTS
The candle power of the crater light directly in front of the arc is
shown in Fig. 2. As would be expected the candle power increases
with the current. When the same current is used on two different
size carbons of the same composition, the smaller size carbon, that is,
the one with the higher current concentration, gives the greater
candle power.
The crater light is only approximately 68 per cent of the total light
from the high intensity arc as measured directly in front of the crater.
The additional light comes almost entirely from the tail flame which
streams out of the positive crater.
The candle power as well as the steadiness of operation is affected
294 D. B. JOY AND A. C. DOWNES [j. s. M. P. B.
by the angle and relative position of the negative carbon with re-
spect to the positive crater and by the voltage maintained across the
arc. The angle is usually fixed by the construction of the lamp. The
best results were obtained when the relative positions of the negative
carbon and positive crater were such that the negative flame just
brushed the lower edge of the positive crater as shown in Fig. 3-A.
If the negative flame bathed the lower outside of the positive crater
appreciably, as shown in Fig. 3-B, the candle power decreased prob-
ably because some of the current was taken on the outside of the posi-
tive crater thus lowering the current and energy concentration on the
inside of the crater. If the edge of the negative flame were consider-
ably ahead of the lower edge of the positive crater as shown in Fig.
3-C, it would not have as much tendency to keep the hot gases in the
A B
FIG. 3. Effect of position of negative.
crater and would result in a lower candle power. It was found in the
case of the 16 mm. carbons in the current range of 140-150 amperes,
which is ordinarily used, that the best arc voltage was 73-83 volts.
Below this voltage the negative was so close to the positive that the
negative flame appeared to impinge on the hot gases in the positive
crater with such force as to actually drive them out with a consequent
unsteadiness and loss of light. Above this voltage the negative was
so far away from the positive that the negative flame apparently
lacked the necessary force to confine the gases in the positive crater
and caused a loss of light from the crater area. With lower currents,
lower voltages can be used.
The 13.6 mm. carbons in the current range of 110-125 amperes
operated best at approximately 67-73 volts and the 9 mm. carbons in
the current range of 60-70 amperes operated best at 4855 volts. In
general, if lower currents are used, the voltage should be correspond-
ingly decreased. The effect of lower and higher voltages with the
March, 1930]
HIGH INTENSITY ARCS
295
9 mm. and 13.6 mm. carbons is the same as with the 16 mm. carbons
although to a somewhat smaller degree.
The angular distributions of candle power from the positive craters
of 9, 13.6, and 16 mm. carbons in the horizontal plane in a total angle
of 80 are given in Fig. 4 for a number of different currents. The
NATIONAL HIGH INTENSITY CARBONS
CAN
M.E PO
WER DISTRIBUTION OF CRAT
IN HORIZONTAL PLANE
LR LIG
-IT
90000
8QQOO
70000
6QOOO
5QDOO
40000
30000
20000
/
>^
^
K
/
\
\
^
6 MM.
NATION
U. HIGH INTCN'
150 AMPS.
80 VOLTS
>ITY C*
RBON
\
S
*^.
^^~
X
3.6 MM
. Npmo
MftL HIG
120
72
H INTE
A.MPS.
VOLTS
ITY
IARBON
_,
"Vs^^_^
-~
^
3.6 MM
NATIOI
4AL HIG
H INTE
4SITY C
^^^
ARBON
^
^^
^= 3 -
9 MM.
_ i- ii
NATION
70
in -
AL HIG
VOLTS
~~
4 INTE
43ITY
^^
:ARBOh
^
51
VOLTS
40"
30*
20'
10-
10-
20'
30
HORIZONTAL ANGLE FROM M\5 OF POSITIVE CARBON
FIG. 4. Angular distribution of candle power from posi-
tive craters of various carbons.
candle power is slightly lower directly in front of the crater than
at 10 to 20 on either side. The candle power holds up remarkably
well to the 40 limit measured and is only 10 to 17 per cent lower at
40 than at the center. This accounts for the decided increase in the
useful light from the high intensity arc when a mirror or condensers
of large effective angle 10 are substituted for the old style condensing
lenses of small effective angle.
The light distribution is approximately the same for the different
296
D. B. JOY AND A. C. DOWNES
[J. S. M. P. E.
sizes of carbons and the different current values investigated as
is clearly shown in Fig. 4.
The areas of the crater openings of the different size carbons at the
various currents are given in Fig. 5. The cross-sectional areas of the
9 mm., 13.6 mm., and 16 mm. high intensity carbons are 64 sq. mm.,
145 sq. mm., and 201 sq. mm., respectively. It is obvious from the
curves that the crater openings for even the higher currents are much
less than the original carbon cross-section.
The decrease in crater opening for the lower current densities is
140
NAT
lONfll
.HIGH IN
TEN:
5ITY
CARE
0NS
X
i
CRffTE
? OPE
VS.
.NING
x
x^lCM
W
100
80
60
40
20
URREN
T
x
^
^
^^
-^\
i^
\& MM.
IMM!
,
JO 60 70 60 90 100 110 120 130 140 150 16C
CURRENT
FIG. 5. Crater opening vs. current.
due in part to the increased spindle or tapering of the portion of the
carbon projecting from the positive holder. This increased tapering
is due to the enormous decrease in the length of carbon consumed per
unit of time for a small decrease in current which allows a longer time
for the hot surface of the carbon close to the crater to burn away.
The size of the crater opening or light source of the high intensity
carbons is important in considering the application of any optical
system for it has long been recognized and clearly demonstrated be-
fore this Society 11 - 12 that the light efficiency for motion picture pro-
jection decreases rapidly as the area of the light source increases.
The intrinsic brilliancies in candle power per square millimeter of
March, 1930]
HIGH INTENSITY ARCS
297
crater opening have been calculated from the above values of candle
power and crater opening and are plotted in Fig. 6. As in the case
of the candle power, the intrinsic brilliancy increases very rapidly
as the current is increased on any given size carbon. The values
come within the range of those given in the literature. 1 ' 7 It is
believed, however, that this is the first time that data showing the
change in intrinsic brilliancy for the currents and sizes of high
intensity carbons have been compiled. It is interesting to note that
practically the same intrinsic brilliancies are Obtained with the various
NATIONAL HIGH INTEI
Msrry D
RBONS
'
NTRINSIC BRI
/imne^r
LLIANC
r
/
8OO
1
1
1
,600
-500
400
300
M
,M./
/
x
/
/
x
/
^x
X
/
/
n
1.6 MM.
/
^s
^
r>MM
>|V|M*
'
X
X
/
X
>0 60 70 80 90 KO 110 120 130 14O 150 16C
CURRENT
FIG. 6. Intrinsic brilliancy vs. current.
sizes of carbons at the currents ordinarily used. These values, rang-
ing from 500 to 750 candle power per square millimeter, illustrate quite
forcibly the advantage that the high intensity arc has for projection
purposes over the plain carbon arc with an intrinsic brilliancy of 130
candle power per square millimeter and the incandescent tungsten
filament projector lamp run at overvoltage with an intrinsic brilliancy
of 27 candle power per square millimeter. 13
Typical curves of the spectral energy distribution of the light from
the craters of high intensity arcs are given in Fig. 7. The distribution
closely approximates that of sunlight. 9 The curves show that there
is approximately the same amount of energy in the blue region as in
298
D. B. JOY AND A. C. DOWNES
[J. S. M. P. E.
the red region for the lower currents on the carbons. As these cur-
rents are increased as evidenced by the curves for the 13.6 mm. car-
bons, the red end of the curve increases faster than the blue so that
at the high currents there is actually an appreciable preponderance
of red as compared with blue. This is contrary to the distribution
curves given in the Bureau of Standards Scientific Paper No. 539, but,
as stated previously, the measurements tabulated in that paper were
ANGSTROM UNITS
ULTRAVIOLET VIOLET BLUE GBCCN YELLOW
FIG. 7. Spectral energy distribution curves.
made on the unscreened arc and included the light from the negative
arc stream and tail flame which amounts to approximately 32 per cent
of the total light and which is known to give a decided peak of energy
in the blue and near ultra-violet end of the spectrum. This tail
flame and negative arc stream light is not picked up by the optical
system commonly used in either the Sun Arc or projection lamps and
is not therefore a factor. It would seem from these energy distribu-
tion curves in Fig. 7 that the high intensity arc, particularly
at the higher currents, is a very desirable light source for use in motion
picture photography.
March, 1930] HlGH INTENSITY ARCS 299
An example of the use that can be made of data of this nature is
furnished by comparing the relative light which can be obtained on
the screen when 13.6 and 16 millimeter carbons are used with the or-
dinary plano-convex lens combination. If the 13.6 millimeter car-
bons were to be burned at 120 amperes and the 1'6 millimeter carbons
at 145 amperes, the crater areas (Fig. 5) are 90 and 137 square milli-
meters and the intrinsic brilliancies are 737 and 620 candle power per
square millimeter, respectively. It has been shown in the Trans-
actions 12 that for crater areas of 137 square millimeters the relative
screen illumination with arc and lenses set properly is approximately
27 per cent more than for a crater area of 90 square millimeters with
two sources of the same intrinsic brilliancy. After correcting for the
difference in intrinsic brilliancy, it is found that only 7 per cent more
light can be expected from the 16 millimeter carbons at 145 amperes
than from the 13.6 millimeter carbons at 120 amperes. Such cal-
culations as these, which are made possible in part by the data given
above, should be of some assistance in the more efficient use of this
very fine source of light for projection of all kinds.
REFERENCES
1 BASSETT: "The High Power Arc in Motion Pictures," Trans. Soc. Mot.
Pict. Eng., No. 11 (1920).
2 PRIEST: Tech. Papers Bur. Stand., No. 168 (1920).
3 BASSETT: "Electrochemistry of the High Intensity Arc," Trans. Amer.
Electrochem. Soc., 44 (1923).
4 LICHTENBERG: "Military Searchlights," Trans. III. Eng. Soc., 15 (1920).
5 Giu,ETT: "Modern Searchlights," /. Amer. Soc. Naval Eng. (1922).
6 COBLENTZ, DORCAS, AND HUGHES: Sci. Papers Bur. Stand., No. 539 (1926).
7 BENFORD: "High Intensity Arc," Trans. Soc. Mot. Pict. Eng., No. 24 (1925).
8 BASSETT: "Sources of Light," Trans. Soc. Mot. Pict. Eng., 10, No. 27 (1926).
9 GREIDER AND DOWNES: "Sunlight Natural and Synthetic." A paper
presented before the 23rd annual convention of the Illuminating Engineering
Society, Philadelphia (Sept., 1929).
10 TOWNSEND: "An Improved Condenser System for Motion Picture Projec-
tion," Trans. Soc. Mot. Pict. Eng., 11, No. 31 (1927).
11 STORY: "Preliminary Measurements of Illumination in Motion Picture Pro-
jection," Trans. Soc. Mot. Pict. Eng., No. 9 (1919).
12 STORY: "Further Measurements of Illumination in Motion Picture Pro-
jection," Trans. Soc. Mot. Pict. Eng., No. 10 (1920).
13 CADY AND DATES: Illuminating Engineering, Second Edition, John Wiley
and Sons, Inc., New York (1928), pp. 38 and 76.
DISCUSSION
MR. STOLLER: I should like to ask Mr. Downes what prospects there are for
increasing the amount of illumination available. With the advent of color
300 D. B. JOY AND A. C. DOWNES [J. S. M. P. E.
pictures and the wider film we are going to need about double the light flux
through the optical system that we are now obtaining.
MR. DOWNES: We have made and sold some quantities of carbons for use
in a 250 ampere searchlight but as we unfortunately had no machine in which
we could burn them, our data are not complete. Calculations from the very
meager information available indicate that the light from this arc is at least
fifty per cent greater than that from the regular 150 ampere searchlight. This
is confirmed by certain tests made by the United States Army.
MR. GRIFFIN: I should like to ask what size the carbons were.
MR. DOWNES: 16 mm.; the same size as the 150 ampere carbons.
MR. MOLE: Some experiments were carried on about eight years ago on the
16 mm. carbon with increased current, and some 25 samples were made, and of
these about three had some promise in direct operation. At that time, we found
we had an increase of about 50 per cent in illumination at 175 amperes.
MR. BENFORD: With regard to the arrangement shown in Fig. 1, were lenses
not used in making this separation? If you used two apertures to get a pinhole
image, the image would be very poor. There would not be a clear division
between crater and flame light. This shows up too in the curves in the manner
in which the scattered light is shown to increase with current. As the current
is increased, there is a tendency for the gas from the crater to boil over the sides,
and the region surrounding the crater is full of gas. If a sharp image of the crater
had been made, it would have been found there is not much increase in the useful
flux from the electrode.
MR. DOWNES: Replying to Mr. Benford, we roughly checked the amount
of flame light, which was included with what we have called crater light in
this set-up, by using both larger and smaller sized openings in screen A and found
that with the particular size adopted only a negligible amount of flame light
entered the box C in Fig. 1.
In making these measurements no readings were attempted beyond the rating
of the carbon, that is, the highest current which would give quiet, steady burning.
This seems to me to be the best way to arrive at a rating for a high intensity
carbon.
MR. GREENE: Can Mr. Downes tell us at what angle the negative carbon was
set?
MR. DOWNES: I think it was 35.
MR. GRIFFIN : Can Mr. Benford tell us, from the research laboratory check,
what the maximum rating is for the 16 mm. carbon?
MR. BENFORD: At 165, it is about right.
MR. GRIFFIN: Did I understand Mr. Downes to say that the 250 ampere
carbon was of different construction from the regular 16 mm.?
MR. DOWNES: Entirely different.
MR. GRIFFIN: And you have not arrived at a definite rating?
MR. DOWNES: Yes, sir.
MR. GRIFFIN: Are the carbons available?
MR. GEIB: I think Mr. Benford and Mr. Griffin are referring to different
types.
MR. GREENE: Would it be possible or practical to build a 13.6 mm. carbon
of the 250 ampere type to burn at more than 125 amperes?
March, 1930] HlGH INTENSITY ARCS 301
MR. DOWNES: Yes, it is possible to produce a 13.6 mm. carbon of the same
type as the 16 mm. 250 ampere carbon. It should be remembered, however,
that a considerably higher current is required with a super-high intensity carbon
to equal the illumination given by the regular carbon of the same size at its
point of maximum light production. In other words, considerably more than
150 amperes on the 16 mm. 250 ampere carbon is required to give a light value
equal to that of the regular 16 mm. carbon at 150 amperes.
MR. GRIFFIN: I am interested in this and should like to ask if Mr. Downes
can tell us about the quality of the light he is able to get from the carbon at 200
amperes. My impression is that it is yellow; is that so?
MR. DOWNES: I do not know that I can answer that definitely. I doubt if
it would be yellow at 200 amperes. I should hesitate to say what the color
would be.
MR. MOLE: Do you happen to know definitely the burning rate of the carbon
compared with the normal 16 mm.?
MR. DOWNES: It has varied from 22 inches an hour up to 31 inches an hour;
the average is about 28 inches an hour.
MR. FARNHAM: With regard to the question of more light for color picture
projection; was any work done with high efficiency condensing lenses, so that
a larger angle of light from the carbons could be intercepted?
MR. DOWNES: Work has and is being done, but we are not concerned primarily
with the production of lenses. We have nothing whatever to do with them.
MR. GRIFFIN: Might I ask Mr. Downes in what way a super-high intensity
and the regular high intensity 16 mm. carbons differ in construction?
MR. DOWNES: The shell of the regular 150 ampere 16 mm. carbon is basically
lampblack and if burned at 250 amperes will be consumed at a rate of 48 inches
to 60 inches per hour which is very fast. The 250 ampere 16 mm. carbon is
primarily coke and burns much more slowly than the lampblack.
The cores of the two carbons are also different using different compounds of
the rare earths. The compounds used in the 150 ampere carbons begin to cause
bad unsteadiness at a little over 160 amperes.
A YEAR OF SOUND
HAROLD B. FRANKLIN*
In the operation of a vast chain of theaters catering to almost seven
hundred thousand patrons daily, with over ninety per cent of our
theaters equipped with sound installations, our organization is in a
position to study the requirements and reaction of the general public
in the acceptance of the sound motion picture. I am glad to have this
opportunity to make a few observations on this absorbing subject.
That sound is here to stay is a foregone conclusion. It has brought
to the motion picture the added advantage of speech and song and
has enhanced the scope of screen entertainment, making possible
perfect musical interpretation and bringing greater realism through
the intelligent use of effects. Sound of every description is a part of
our lives and it is natural, in a faithful representation of life, that
speech and song interpret our moods. The public wants sound motion
pictures but those that are either poorly recorded or reproduced are
endangering the future of sound.
The sound picture has made it possible to combine the best qualities
of the silent screen with the best traditions of the theater. This has
made it possible for the sound motion picture to meet the legitimate
theater not alone on financial but on artistic grounds as well. A
great advantage which sound pictures hold is their ability to present
every word so clearly and distinctly that no one need strain to hear
what is being said, at least when recording and reproducing is prop-
erly conducted. A whisper is clearly audible from the front row in
the orchestra to the last row in the balcony. Let me offer my own
opinion that when dialog pictures reach the degree of technical perfec-
tion now enjoyed by stage productions the latter are going to suffer by
comparison.
The manufacture of sound motion pictures has passed the stage of
mystery. Those engaged in the business of making sound pictures are
now familiar with the medium. Many technical words coined be-
cause of sound have already become a regular part of cinema vocabu-
* Fox West Coast Theaters, Los Angeles.
302
A YEAR OF SOUND 303
lary. There is now a feeling of confidence around the studios that
was lacking in the beginning. Technicians and players are available
in sufficiency. They have a full realization of sound possibilities and
are equipped to use their knowledge to advantage. Moreover, prac-
tically every important producer is now active in the new medium.
We have learned that the entertainment and artistic value of the silent
technic need not be sacrificed in the adaptation of sound. What is
more, each new sound motion picture has shown improvement, which
is reflected by an ever increasing patronage. Notwithstanding the
general acceptance of sound, certain stories or subjects that do not
lend themselves to dialog will in all likelihood continue to be made in
silent form, for the public have shown themselves to be hospitable
to silent motion pictures provided they are of good quality. This has
been demonstrated recently by huge grosses of such pictures as Greta
Garbo in Single Standard, Joan Crawford in Modern Maidens, Four
Feathers, and others.
Under the new conditions it is likely that fewer productions will
be made than in the past. It is a far more simple problem to turn
out a number of silent motion pictures that require only titles to hold a
story together. But when a story depends on intelligent and continu-
ous dialog, the richest capabilities of authors and directors are taxed.
Where the silent motion picture left something to the imagination of
the audience, a dialog picture, to be acceptable, must absorb the full
attention of the auditor. Good writers will become more important
than in the past; and though it is likely that those who have been
writing titles for the silent motion picture will be in demand as writers
of dialog pictures, their dialog will probably be part of their own sto-
ries, for the new art will demand an author's creation. The industry
would do well to foster a school for playwrights and otherwise en-
courage writers of talent. Good story material will be the most im-
portant requisite in time to come for the dialog motion picture, be-
cause a picture is never better than the story it tells.
A new musical interest has been added because of the sound motion
picture. Scores adroitly arranged, that interpret each situation,
together with cleverly written theme songs, have increased the enter-
tainment value of the screen. The music, as synchronized, is in
closer unity with the situation pictured than was the case in former
times. There is not, moreover, the distraction caused by the close
proximity of musicians to the screen. The art of scoring motion
pictures under the new order of synchronization has scarcely begun,
304 HAROLD B. FRANKUN [j. s. M. p. E.
and important strides may be expected in this connection within the
next few years. Where inadequate orchestras used to render their
ineffectual accompaniments, motion pictures are now reaping the
special benefits of musical synchronization. Music of the best caliber
becomes available to every type of theater. Legitimate theaters
may now install reproduction apparatus to be used not only for the
showing of special sound motion pictures but also for furnishing
entr'acte music.
Standardization would be of advantage in considering the sound-on-
film and disk method of recording and reproducing. The present
condition where studios and exhibitors have the choice of sound-on-
film and disk methods is one that has resulted in duplication. Stand-
ardization will eventually eliminate one or the other, and in the interest
of greater efficiency it would appear that the system of recording sound
on film will ultimately be the standard adopted by most producers.
The advantages of the sound-on-film method are many ; economically,
it is the safer and surer method. When the sound is recorded as part
of the film itself we eliminate the possibility of mistakes in shipment
or in handling a possibility that actually does arise in connection
with the disks. Furthermore, the sound-on-film system is handled
much more easily in the projection booth, and our experience would
indicate that fewer surface noises result when this method is used.
The gradual but sure loss of film due to breaks and careless patching
frequently throws the disk method out of synchronization.
The sound motion picture has met with greater success in theaters
of medium seating capacity and this fact may have a marked effect
upon the design of newer theaters ; for, while satisfactory reproduction
has been attained in theaters of huge seating capacity, yet the problem
in such houses is so formidable as to require constant and minute
supervision. Auditoriums will be specially designed with the great-
est regard to acoustical conditions. We may well expect except in
theaters located in the very largest communities, where stage enter-
tainment may be expected at some time to be a part of the program
to see the elimination of the present size stage with its lofty gridiron.
Projection booths have already become the subjects of special study
by theater architects and engineers. In the newer Fox West Coast
Theaters, for example, a special observer's box is provided as part of
the booth, so that projectionists may see and hear everything just
as it comes to the audience. Experiments are now being made looking
to the substitution of remote controls for the present methods of booth
March, 1930] A YEAR OF SOUND 305
operation. In our Grauman's Chinese and Carthay Circle Theaters
in Los Angeles such controls are mounted on a small panel in a seat
on the orchestra floor where the volume and tonal quality of sound is
controlled from the vantage point of a place in the audience. Speech
must be audible. Many theater patrons have been lost because of
speech not being audible. Others have condemned sound because
it was too loud. It is very essential that an observer be placed in the
audience, at all times, so that the sound may be governed accordingly.
No one can doubt that with the development of sound synchroniza-
tion electrical science has entered the entertainment field. It is to
be expected that the great electrical organizations will take an ever
increasing interest in the future of the industry. Organizations such
as the American Telephone & Telegraph Company through its sub-
sidiary, the Western Electric Company, the General Electric Com-
pany, the Westinghouse Electric Company, and the Radio Corpora-
tion will further encourage the development of sound and will make
available to the public the resources of their laboratories.
In view of this interest the possibilities of motion picture entertain-
ment may be said to have scarcely been scratched. Newer methods
and revolutionary improvements will come in direct ratio to the scien-
tific facilities applied to them. This will probably bring to a prac-
tical solution such problems as stereoscopics as well as the further de-
velopment of natural color. The possible future of the motion pic-
ture screen, with animation, sound, color, third dimension, and screen
magnification, gives unbounded play to the imagination. Eventu-
ally there could be such perfection along these lines that one entering
a theater and seeing such an exhibition for the first time will get the
impression that he is actually seeing and hearing living people in
action.
Already we have sound, color photography, and the double width
screen. The double width film is now being developed by different
organizations. It is hoped that standardization will guide them in
their final development, if the double width motion picture is to be
accepted by the industry under the most favorable auspices. By this
means an image of wider vista may be extended through the prosce-
nium opening. To bring the innovation to the public will require
important changes, involving new cameras and projectors, as well
as new screens. In production, the optical and photographic prin-
ciples involve a new technic in set construction, as well as lighting.
Pessimistic forecasts concerning the sound motion picture have been
306 HAROLD B. FRANKLIN [j. s. M. P. E.
made on the basis of novelty or of difficulty in foreign distribution;
but more recently others have arisen in connection with what seems to
be the next development television. It has been held by some that
before sound pictures can reach their potential audience television
will snatch it away.
That there will be some sort of problem no one can deny. That one
phase of the problem, moreover, will somehow involve competition
is likewise easy to foresee. A new amusement feature is almost bound
to distract people away from the old, simply because newness affects
us that way. Then, too, each diversion builds up its own following.
In consequence, the film industry must look forward to a day when a
rival attraction will call for the tactics of rivalry. There is at this
moment a need of clear vision and close thinking on the part of con-
structive minds, for the highest resourcefulness, the readiest initiative
will be required to offset the opposition that looms ahead in the dis-
tance. All this, mind you, without panic or pessimism; for although
it is the opinion of some observers that the cinema may be seriously
affected by the perfection of television, there are not lacking others
who insist that television will be an adjunct to the picture trade.
They base their prediction on the saving thought that television
may develop new audiences for us; nor need this reasoning seem
utterly paradoxical. In the beginning radio broadcasting was con-
sidered a serious competitor of motion pictures and in the beginning
its introduction did affect the box office receipts. Eventually, how-
ever, as the novelty of radio wore off and it became part of everyday
life, it helped the motion picture by cultivating a taste for entertain-
ment in many who had not been entertainment minded before. In a
like manner it is conceivable that motion pictures sent through tele-
vision may act as a stimulant to cultivate a taste for the theater in
people who now visit us only on rare occasions. It is really not to be
expected, after all, that the American family will be content to sit
at the fireside at home and be entirely satisfied with the entertain-
ment that may be sent through the air by means of television. With-
out arguing the point further, let me say merely that this fact is recog-
nized by even so important an organization as the Radio Corporation
of America, which is conducting laboratory experiments with tele-
vision. Only recently the corporation has become interested in a
theatrical enterprise involving many millions. It is thus only fair
to deduce that those who are closest to television apparently feel
that the motion picture theater is here to stay.
March, 1930] A YEAR OF SOUND 307
Why not! People like to be seen by others and enjoy being in
public places. Here is a refined instance of "mob psychology" one
which perhaps accounts for the universal preference to go where the
crowds go. In every city, most people congregate in the most
popular place, whether it be a theater, a dance hall, or a restaurant.
There may be plenty of room in similar places away from the main
stem, yet the public will put up with disadvantages, congested traffic,
and other discomforts to be with the crowd. It is the entertainment
that is presented that interests the public, and not the fact that it is
a motion picture and part of public entertainment is the pleasure of
congregation. Producers who continue to present good entertain-
ment need not be concerned with the inroads that the perfection of
any device may eventually bring.
Experience has always indicated that in order to get the great-
est enjoyment from the motion picture or other entertainment it is
essential to be one of an audience. It is questionable whether drama
or comedy, even though it be sent through television successfully, can
register properly without the presence of a large number of people.
Laughter is contagious ; dramatic moments require a socialized recep-
tion to register properly. This statement may be illustrated by the
fact that frequently we find it difficult to laugh at comedy renditions
over the radio. The reason is not hard to find, for even motion pic-
ture producers are not able to judge a finished product until it has been
previewed at a theater. Many scenes register differently from the
way anticipated and changes are made after the audience reaction has
been determined.
The sound motion picture, however, should be prepared to face a
readjustment period when television becomes practical. Most as-
suredly, in the beginning, the novelty will evoke wide interest. But
after the newness wears off television will find its usefulness and its
proper groove and become just another comfort to modern life, as
has radio.
Television has a brilliant future but not one which will come in
weeks or months. In the years directly ahead sound has no obstacle
to its solid intrenchment with the public. Given such a start,
it should devote itself to the kind of product that will hold fast the
affections of theatergoers.
Sound pictures require great skill in presentation. The public
has been educated as to quality of recording and sound reproduction.
Sound technicians are responsible for further development which will
308 HAROLD B. FRANKUN
eliminate the difficulties and will standardize the operation and pre-
sentation. It is remarkable how theater patrons question the two
sizes of pictures used in many theaters when presenting Movietone
and Vitaphone subjects. Many theaters have restored the Movie-
tone picture to normal size, at the projector, while others are using
the Movietone flipper to cover the space omitted on the screen, be-
cause of masking the sound track at the theater.
It is the opinion of many in both production and exhibition circles
that the aperture size must be standardized in Movietone picture
cameras and projectors, and this is now receiving serious considera-
tion by different official bodies.
The potentialities of sound have opened a greater field for the
motion picture than ever before. The future of the screen is brighter
from every artistic and economic point of view. The industry is
just entering its greatest era of development and more than ever will
justify the fact that it wields the world's greatest medium of expres-
sion. The future, with its greater plans, greater now than in any
previous period of the business, brings to us the vision of the greater
responsibility that is ours.
THE OPTICS OF MOTION PICTURE PROJECTORS
ARTHUR C. HARDY*
INTRODUCTION
The usual method employed in designing an optical system seems
to consist in assembling a collection of lenses and trying them in vari-
ous combinations and positions until either the patience of the ex-
perimenter is exhausted or an optimum condition seems to be reached.
This criticism does not apply, of course, to the optical systems of tele-
scopes or microscopes, but rather to systems like that of the motion
picture projector where it is relatively easy to obtain satisfactory defi-
nition in the image but difficult to secure enough illumination on the
screen. Curiously enough, this unsystematic method of design pro-
cedure seems to be peculiar to optics, and is certainly due in part to
a lack of knowledge concerning the performance that could be ex-
pected of an ideal optical system. In other branches of physics, such
as heat, for example, there is the well-known and widely employed con-
cept of thermal efficiency. Every heat engine or other piece of ther-
mal equipment is rated by the closeness of its approach to the per-
formance of an ideal apparatus which is assumed to operate without
losses. In a previous paper, 1 the present author has attempted to
establish a similar basis of comparison for optical systems based on
the conservation of energy principle. The purpose of the present
paper is to apply the results to motion picture projectors.
SCREEN ILLUMINATION WITH AN IDEAL OPTICAL SYSTEM
It will simplify the present treatment to consider first only those
elements in the system which are fixed by the assigned conditions.
These are quite evidently the gate, the projection lens, and the screen,
as shown in Fig. 1 . The size of the gate is fixed by convention and the
size of the screen is largely determined by the size of the theater.
This fixes the magnification of the film on the screen which in turn
determines the focal length of the projection lens. Thus, if y is the
* Massachusetts Institute of Technology, Cambridge, Mass.
1 HARDY, ARTHUR C.: "Distribution of Light in Optical Systems," Jour.
Franklin Inst., 208 (Dec., 1929), p. 773.
309
310
ARTHUR C. HARDY
[J. S. M. p. K.
distance from the focal point of the projection lens to the screen, the
focal length (/) of the projection lens is determined by equation (l),
where m is the linear magnification of the film on the screen.
Let us first consider these elements in Fig. 1 independently of the
customary source of illumination. To do this, we may imagine a
ground glass or diffusing glass placed just to the left of the gate and we
may ignore for the present the method by which this receives its
illumination. If the diffusion is perfect, this source will appear equally
bright from every direction of observation. Assuming its brightness
Diffusing
Glass
Gate
Screen
FIG. 1. Blements of an optical system which determine magnification and
intensity of illumination.
to be B candles per square foot, it has been shown 1 that the illumina-
tion at the center of the screen is given by equation (2),
E = TT B sin 2 S f
(2)
where E is the illumination in lumens per square foot, and 6' is the
half-angle of the cone whose base is the effective area of the projec-
tion lens and whose apex is the center of the screen. Equation (2) is
rigorously correct when the source is perfectly diffusing, when the
losses by reflection or absorption within the projection lens are negli-
gible, 2 and when the projection lens obeys the sine condition. The
latter condition can be derived from the conservation of energy prin-
ciple and applies only to a perfect image-forming system. No actual
lens can be constructed to fulfill this condition completely nor can the
losses caused by absorption and reflection be eliminated. Conse-
quently, equation (2) gives the illumination at the center of the screen
* The transmission of the usual projection lens is between 60% and 80%,
depending principally upon the number of air-glass surfaces it contains. The
loss by reflection usually amounts to 5% for each air-glass surface in the system.
March, 1930] OPTICS OF MOTION PICTURE PROJECTORS 311
that could be expected of an ideal optical system and a source of in-
trinsic brightness B. It is as futile to attempt to produce more
illumination than is indicated by equation (2) as it is to attempt to
build a perpetual motion machine, and for the same reason. Ob-
viously, it makes no difference how far the diffusing glass is placed
behind the gate, provided the gate appears filled with light from every
point of the projection lens.
When 6' is small, as it is in this case, equation (3) below gives sub-
stantially the same result.
,., _ Brightness of Source X Effective Area of Projection Lens . .
xi . . (^oj
Square of Distance from Lens to Screen
The units of E will be lumens per square foot (or foot-candles) when
the brightness of the source is expressed in candles per square foot
and the area of the projection lens and its distance from the screen
are measured in square feet and feet, respectively. Equations (2) and
(3) apply only to the center of the screen or better to the point where
the optical axis intersectst he screen. It has been shown 1 that the
illumination decreases toward the edge of the screen as the fourth power
of the distance from the projection lens. For example, the illumina-
tion at the edge of the screen can be determined by multiplying the
illumination at the center by the fourth power of the ratio of the re-
spective distances of the two points in question from the projection
lens. As the screen is usually small, this decrease in illumination
toward the edge of the screen is not serious. As a practical matter, a
slight reduction in illumination toward the edge is desirable because
of the contrast between the edge of the screen and the black border
surrounding it. In fact, it has been found experimentally that an
absolutely uniform illumination of the screen makes it appear too
bright at the edges due to this contrast effect.
THE EFFECT OF APERTURES
Before attempting to include the light source and condenser, let
us consider briefly the effect of apertures on the performance of the
optical system. Fig. 1 shows two apertures, one being the gate and
the other the rim or effective stop of the projection lens. Since the
gate is imaged on the screen, it is known in optical theory as a field
stop and limits only the area of the picture without having any effect
on the screen illumination. If a metal mask containing a small
hole were inserted at the gate, the size of the picture would be reduced
312
ARTHUR C. HARDY
[J. S. M. p. E.
but the illumination of the remaining portion would be unaltered. In
other words, placing this mask at the gate would have exactly the
same effect as moving in the black border surrounding the screen, a
result to be expected from the fact that the two planes are conju-
gate to each other. On the other hand, if the same mask were placed
at the projection lens, the illumination of the entire screen would be
reduced as shown by equation (3), but the illumination would still be
nearly uniform over the entire picture area. The hole in the mask is
then said to operate as an aperture stop as opposed to a field stop.
Although the insertion of such a mask or aperture can serve no useful
purpose in practice, we shall see later that the source of light or the
condenser may produce substantially the same result, and a considera-
tion of the effect of apertures is consequently in order.
Diffusing
Glass Gate
Screen
FIG. 2. Effect of the stop positian.
Let us consider the effect of placing a small stop or aperture at some
point on the axis of the optical system between the projection lens and
the screen, as shown in Fig. 2. As this figure is drawn, this stop is
the aperture stop of the system. Although this is obvious from the
figure, it is easily proven in any case by substituting the effective area
of the stop for the area of the projection lens in equation (3) , and the
distance of the stop from the screen for the corresponding distance of
the projection lens from the screen. If the resulting illumination is
less than without the stop, the latter is the aperture stop of the system.
We should normally expect the illumination to decrease toward the
edge of the screen as the fourth power of the distance from the center
of the stop. In this case, however, the presence of the projection
lens in the system causes the illumination to decrease at an even
greater rate because the effective area of the stop is reduced. Thus,
as Fig. 2 has been drawn, light is received at the edge of the screen
from only that portion of the stop through which the projection lens
can be seen. If no portion of the projection lens can be seen through
.
March, 1930] OPTICS OF MOTION PICTURE PROJECTORS 313
the stop from a given point, the illumination is zero at that point. In
other words, when the stop is at the projection lens, it limits only the
aperture of the system while, if it is placed at the screen, it limits only
the field. For intermediate points, it may limit either the field or
the aperture or both, depending upon its size and position and on the
rest of the optical system. For such intermediate positions, the field
is not sharply limited but is gradually vignetted.
The effect of a stop in the system at the left of the projection lens
can be determined by using the method due to Abbe. This consists
in determining the size and position of the image of the stop formed by
the projection lens and treating it as a real stop in the system. Since
every ray through a given point in the real stop goes through the cor-
responding or conjugate point in the image, the image is just as effec-
tive in limiting the rays as a real aperture at that point would be.
For example, if the diameter of the diffusing glass in Fig. 2 were too
small, its effect could be calculated by determining the size and posi-
tion of its image formed by the projection lens, using the familiar
lens equations. Suppose that the image of the diffusing glass lies
in the plane of the real stop shown in Fig. 2 and that its size is the
same as the free aperture of the latter. The diffusing glass would
then behave in every way like the real stop. In fact, the stop could
then be removed and both the field and aperture of the system would
be the same as though it were still in position. This is a very
useful method of analyzing the effect of any element in an optical
system.
DESIGN OF THE ILLUMINATING SYSTEM
Let us apply this method of analysis to the illuminating system of
the motion picture projector. As we have already seen, the size of
the gate is fixed by convention, while the size of the screen and the pro-
jection distance are fixed by local theater conditions. This deter-
mines the focal length of the projection lens, and its minimum diameter
is determined by equation (3) in terms of the intrinsic brightness of
the source and the amount of illumination desired on the screen.
Since the maximum intrinsic brightness in the case of either carbon
arcs or tungsten filaments is a fairly definite quantity for a given
source, all the elements in the system at the right of the gate in Fig. 1
are known and this portion of the projection system may be laid out
on the drafting table. We come then to the design of the illuminating
system which must obviously satisfy the following requirements:
814
ARTHUR C. HARDY
[J. S. M. P. E
(1) The projection lens must remain the aperture stop of the en-
tire system.
(2) The gate must remain the field stop of the entire system.
These conditions do not determine the best design of the illuminating
system. However, since the cost of operation of either *a tungsten
Gate
Screen
Condenser
Arc
FIG. 3. A system in which the arc crater is focussed on the projection lens
lamp or an arc is approximately proportional to its size, it is more
economical to satisfy the above conditions with as small a source as
possible.
There are two illuminating systems that possess more than ordinary
interest. These are shown in Figs. 3 and 4, but we will consider the
system of Fig. 3 first. The arc is here focussed on the projection lens
by a condenser located at or very near the gate. It is obviously im-
possible with this arrangement for the arc to limit the field or for the
Screen
Arc
FIG. 4. A system in which the arc crater is focussed on the gate.
condenser to limit the aperture. The condenser will not be the field
stop of the system if it is larger than the gate and the arc will not be
the aperture stop if its image fills the entire area of the projection
lens. The magnification of the image of the arc should be as high
as possible so that a small source can be used. This means that the
condenser should have a short focal length, which requires that the
source be placed very close to the condenser. The limit of efficiency
is reached with this system when the focal length of the condenser is as
March, 1930] OPTICS OF MOTION PICTURE PROJECTORS 315
short as possible with due consideration for lens aberrations on the
one hand, and over-heating or pitting of the surface of the condenser
on the other.
Let us now examine the system shown in Fig. 4, in which the arc is
focussed directly on the gate. With this arrangement, it is impossible
for the arc to be the aperture stop of the system, but it may be the
field stop unless the magnification of the image formed by the con-
denser more than covers the gate. As before, the size of the arc will
be a minimum when the magnification of its image is a maximum.
The condenser, in this case, may limit both the field and the aperture
if it is too small. Its minimum diameter may be quickly determined
by applying the method outlined in the preceding section. This con-
sists in determining the image of the condenser formed by the pro-
jection lens, and treating this image in the same manner as the stop
shown in Fig. 2.
If the two major conditions are satisfied, the screen illumination in
both systems that we have just considered will be substantially the
same. However, one system or the other will satisfy these conditions
with a smaller source, depending upon the relative sizes of the gate
and the projection lens. Since the gate is ordinarily smaller than the
projection lens in projecting motion pictures, it is somewhat easier
to fill the gate with the image of the source than to fill the projection
lens. In other words, if we assume the same magnification in the
image of the arc by the condenser, the two major conditions can be
satisfied with a smaller source with the system shown in Fig. 4. On
the other hand, in the projection of lantern slides, or the wide motion
picture film that is now being discussed, the gate may be larger than
the projection lens, and it is then more economical to image the arc
on the latter. In comparing the two systems in this way, we are
tacitly assuming that the surface of the arc crater is sufficiently uni-
form in brightness to focus directly on the gate. This assumption is
seldom completely justified and is never possible with incandescent
lamp sources. Consequently, when the maximum efficiency would
result from imaging the source on the gate, a compromise is usually
made by moving the image of the source toward the projection lens
until the illumination of the screen is sufficiently uniform. The
proper size of the arc can be determined by finding the size and posi-
tion of its image by the condenser, and then determining the image of
this image formed by the projection lens. The second image is then
treated as a real stop in the manner described with reference to Fig. 2
316 ARTHUR C. HARDY [j. s. M. p. E.
in the preceding section. In a similar way, the proper diameter for
the condenser is determined by finding the position and size of its
image formed by the projection lens. It may be worth while to re-
mark that the adjustment of the arc is less critical if the diameter of
the projection lens is slightly larger than required to produce the de-
sired screen illumination.
PRACTICAL CONSIDERATIONS
The foregoing treatment of this subject has been kept as free as pos-
sible from practical details in order that the attention might be fo-
cussed exclusively on the underlying principles. No mention has
been made of the pull-down mechanism or the arc control mechanism,
which may prevent the condenser from being placed in the most favor-
able location. Also, it was not thought desirable to distinguish be-
tween condensing systems employing lenses and those using a mirror.
Both types are characterized by the common property of forming an
image somewhere in space and of a certain size. Also, both mirrors
and lenses have rims in common which may restrict the light beam
unless the diameter is properly chosen. As the fundamental require-
ments are the same in both systems, the design procedure is identical
in the two cases and is greatly facilitated by the concept of an ideal
system, which for our purpose is assumed to operate without losses.
By way of conclusion it is interesting to return again to equations
(2) and (3) and to reconsider the assumptions upon which they depend.
It will be recalled that the source was assumed to be uniform and of
constant brightness from every direction of observation. In other
words, the source was assumed to obey Lambert's law of emission,
which states that the intensity varies as the cosine of the angle from
the normal. An examination of the intensity distribution curves of
some of the sources in common use for motion picture projection shows
a decided tendency for them to obey Lambert's law of emission except
for shadows cast by the negative carbon or the arc control mechanism.
Although this decreases the available illumination, it does not other-
wise vitiate any of the conclusions reached in this paper. It will also
be recalled that the lenses in the system were assumed to obey the
so-called sine condition. Unless the projection lens obeys this con-
dition, the definition at the margin of the screen will suffer. Since
aberrations in the condensing system do not affect the definition on the
screen, the lenses employed in that part of the system need not fulfill
the sine condition to the same degree. In view of the well-known
March, 1930] OPTICS OF MOTION PICTURE PROJECTORS 317
phenomena of spherical and chromatic aberration, it is apparent that
the position and size of the image of the arc formed by the condenser
will depend somewhat upon the zone of the condenser used and the
color of the light. Consequently, our two fundamental conditions
must be extended to include every zone of the lens and every color in
the light. The magnitude of the losses within the system due to ab-
sorption and reflection have already been considered.
It should be stated again that the results obtained on the basis of
these assumptions apply only to an ideal system and that no actual
system can quite equal its performance. This difference between the
two cases may be used as a measure of the efficiency of any actual
system. Since the underlying principles in the case of an ideal system
are more or less obvious, much of the uncoordinated experimentation,
which often accompanies the design of projection systems, can thereby
be avoided.
MULTIPLE EXPOSURE CINEMATOGRAPHY IN SOUND
PICTURES
WILLIAM STULL*
It is hardly more than a year since sound pictures took their place
as the major part of studio production programs. In that year an
enormous amount of progress has been made, alike in the artistic
utilization of the new form, and in the technic of its operation. Stu-
dio personnel has grown increasingly familiar with the sound device,
and this familiarity has resulted in the overcoming of many of the ob-
stacles which the coming of sound was thought to have placed in the
path of true screen technic.
An instance of this is the reappearance of such truly cinematographic
effects as lap-dissolves and multiple exposure work. A year ago
they were regretfully dropped from the cinematic vocabulary due to
the added complication of sound photography. Now they are re-
appearing, as cinematographers and recorders gain more assured
mastery of the new medium.
Probably the first to reappear were the fade-out and fade-in. Screen
technic demanded them. As a rule, they have been made chemically;
but to cinematographers, chemical fades are rarely satisfactory substi-
tutes for those made directly in the camera. Similarly, recording engi-
neers greatly prefer to control the fades on their sound tracks them-
selves. Therefore, in practically all studios, fades are now made di-
rectly in the camera and recorder. When recording with the variable
density process, by means of a glow-lamp, the most satisfactory
method has been found to be the gradual removal of the lamp to a dis-
tance from the film at which its light is no longer strong enough to affect
the emulsion. While this could of course be done mechanically, it is at
present done manually, very little practice being required to attain
proficiency. When using the light-valve method, two courses are pos-
sible. One may either gradually stop down the lens of the recorder, or
reduce the amplification from the mixing-panel. Both of these meth-
ods are also appliable to the variable area processes, while of course
the only control possible for the disk systems is through the amplifier
* American Society of Cinematographers, Los Angeles, Calif.
318
MULTIPLE EXPOSURE CINEMATOGRAPHY 319
Having mastered the technic of fading in and out in sound, it is
not such a great step to combining and overlapping the fades, making
a lap-dissolve. Still, it has proven quite an undertaking, as it offers
rather more than double the complication and hazard that silent laps
entail. None the less, it is a vitally important part of dramatic
cinematography, and could' not be overlooked; consequently, the
majority of the studios are in one way or another accomplishing sight
and sound laps with increasing frequency. Probably the easiest
way of getting the desired effect is through the use of the optical
printer and the making of duplicate negatives. This is, indeed, the
general practice in the studios using disk recording exclusively. But
"dupes, "unless made with a skill and care almost never found in the
rush of commercial production, seriously detract from the quality of
both picture and sound, and are naturally avoided wherever possible.
A second method is to allow the picture to lap quite as though it were
a silent film, while the sound merely fades in and out with unusual
rapidity: for instance, if the complete lap were to run, say, eight
feet, the sound would fade out in four, being immediately faded in
on the next scene, also in four feet.
But this is so slightly removed from true lap-dissolving that the
added trouble is negligible. Therefore, in most cases, true lap-dis-
solves are returning to favor in preference to other makeshift methods.
When using the variable density systems with glow-lamp apparatus,
the procedure, as is the case in fades, is to withdraw the lamp from
the recorder. Then the several films are wound back to the marked
starting point of the scene, and run forward, with shutters closed and
glow-lamp withdrawn, to the point at which the dissolve was started,
and the fade-in is made in the usual manner. As a matter of actual
practice, however, it has been found necessary to rewind only to the
start of the fade-out, plus the footage necessary to regain speed usu-
ally twenty feet. The writer recently spoke with a cinematographer
who had on the same day made by this method a sequence involving
four such lap-dissolves, without a single failure in the course of a half-
dozen takes. He had found it necessary, however, to recognize the
human element in his problem to the extent of allowing for the in-
evitable lag in the recorder's response: for instance, if the fade were
to come at the 40-foot mark, he would signal the recorder when the
indicator read 38 feet, and then start his own fade.
When recording with the light-valve, the same general technic is
followed, save that the sound is faded in or out by either the optical
320 WILLIAM STULL [J. s. M. p. E.
or electrical methods earlier mentioned. In the variable area systems,
the same general procedure may be followed, but there is an additional
possibility, as well. The entire optical assembly may be gradually de-
centered with respect to the film, gradually reducing the magnitude
of the serrated edges of the sound track to their mean level. If this
be done, moving the assembly to the left, for instance, and at the
same time shielding the right-hand side of the track from exposure,
the other half of the dissolve may be effected by similarly moving the
assembly in from the right, and stopping it when centered. So far
as is known, this latter possibility has not as yet been tried in actual
production, though it is considered quite feasible from the theoretical
standpoint.
For the disk systems, lap-dissolves still present a serious problem.
Maintaining proper synchronism is difficult, and it is highly improb-
able that the two scenes could be recorded directly over each other
successfully. Therefore, the general practice of organizations using
disk recording exclusively is to make all lap-dissolves and fades with
the optical printer. However, where the equipment permits, the
most likely way to secure these effects without the use of "dupes" is
through the use of a film-recording process, and subsequent re-record-
ing onto the disk. Another possibility is the use of two separate
disks. The first is used until the fade-out is complete the volume
being reduced electrically. The second is used with the second scene
of the pair; the photographic film having been rewound to the origi-
nal starting point of the first scene, after which it is run, with the
shutter closed, synchronously with the new record, to the point at
which the second half of the lap begins, whereupon both picture and
sound are faded in, and the scene continued as usual. The two partial
records can then be processed, and re-recorded onto a third and final
one. A third possible method is quite similar as regards the making of
the first record. This is then processed, and played through a loud-
speaker on the set, while the camera runs, with shutter closed, syn-
chronously with the record, which is being re-recorded by properly
placed microphones. At the proper place, the camera shutter may
be opened, and the other microphones about the set gradually ener-
gized to record the action of the second scene.
A variant of this method has been used in the recording of large
scenes, especially those representing theatrical performances. The
vocal part of the scene is first recorded, under acoustically perfect
conditions. The film or disk of this record is then processed, and
March, 1930] MULTIPLE EXPOSURE CINEMATOGRAPHY 321
thereafter played through a loudspeaker and re-recorded while the
photographic part of the scene is made, the actors "mouthing" their
lines and songs inaudibly. This combination enables these some-
what difficult scenes to be photographed and recorded much more
satisfactorily than could otherwise be the case.
Similarly, in a recent film wherein the star was required to play a
dual role, this arrangement enabled him to time his actions perfectly,
and to give himself his own cues. Photographically, the scene was
made by the familiar "split-screen" methods, whereby the picture-
area is divided in two, first one-half being photographed, and then the
other. Strangely enough; the addition of dialog simplified the pro-
cedure, instead of complicating it. Formerly, the action had to be
timed by counts, which, for any degree of precision, was rather in-
volved and exacting and at times highly disconcerting to tempera-
mental players. In this case, however, the actor was able to time
and cue himself. The first half of the action was photographed and
recorded quite normally. Then the sound record in this instance a
disk was quickly processed, and the photographic film turned back
to the original starting point. When the record was ready, it was
played through a loudspeaker on the set, before which a microphone
was hung. Both the camera and recorders were synchronized with
the phonograph, and the remaining half of the scene was made with
the phonograph not only supplying the cues to the actor, but also
making the dialog complete on one record for both halves of the scene.
Similar double-exposure work has been done in at least two in-
stances in the variable density process, using both light- valve and
glow-lamp recording. In the first case, the scene was comparatively
simple, requiring one character to converse with another, played by
the same actor, without a great deal of action. Photographically,
of course, it was easy, the more so since one character remained prac-
tically motionless throughout the scene, presenting his profile to the
camera. The sound was not difficult, either. Between the speeches
of the first character, the sound track was left blank, by closing the
lens of the recording light. This first record was then processed, and
played back to the actor as a cue for his speeches in his second char-
acter. However, instead of using a loudspeaker and re-recording, the
actor wore a radio-earphone on the side away from the camera, and
the two partial records were combined later, in the printing.
In the other case, where the glow-lamp method was used, the two
halves of the scene were made in quick succession, with a single sound
322 WILLIAM STUU,
track. To avoid exposing the film between each character's speeches,
the lamp was withdrawn, and replaced at the proper time. As there
was no partial record to play back to cue the actor, and as counts were
obviously impossible, the cinematographer memorized the entire
scene, and devised an elaborate system of lights by which he could
signal both actor and recorder their respective cues. In this case
again, he had to take into account the lag in their response. Aside
from this, his task was of particular interest because of the nature of
one of the doubled scenes, in which the actor, having beaten him-
self in a fight, knelt over his own prostrate form, and talked with
himself ! The effect was achieved by exact and skillful photographic
matching of the actor's head onto a double's body. The scene was
photographed and recorded three times and each "take" was perfect!
So far as is known, while such double-exposure work is equally
feasible with the variable area systems, none has so far been
attempted, as no need for it has happened to arise in the course of the
regular work of the studios using that system.
Thus, however, it will be seen that, even in the brief space of a year,
studio technicians have so far mastered the sound device that they
can successfully attempt most of the cinematic effects and tricks of
yesteryear in today's vocal films. Had they achieved this under the
perfect conditions of laboratory research, they would be deserving of
the highest praise, but that they have done so instead under the hurried
and nerve-wracking conditions of scheduled commercial production
adds incalculably to the glory of their achievement.
THE ILLUSION OF SOUND AND PICTURE
JOHN L. CASS*
The word "illusion" is one of the most patient and long-suffering
in common usage. It is a favorite with the official propagandists of
the film industry, sharing honors with the appellations, "box-office
appeal" and "sure-fire smash." We have many "illusions" in our
industry, but the one for which we all strive is the "illusion of reality,"
which is also the ultimate goal of all other forms of synthetic entertain-
ment. Motion pictures, with or without sound, constitute a medium
of expression, and accordingly must be governed by certain funda-
mental rules.
If a medium of expression is to be powerful, the medium itself must
be so utilized that it retires into oblivion as it does its work. This
is true in the case of the printed word, the spoken drama, pantomime,
the silent motion picture, and the talking picture. Each one of us
has had the experience of reading an excellent piece of literature which
had been printed rather poorly, but legibly, on cheap paper. As
we opened the book, we noticed the lack of quality, but as the worthy
contents disclosed themselves, the quality of the medium faded in
importance, and eventually we became so engrossed that the con-
sciousness of reading disappeared. The illusion thus created de-
pended upon the fact that legibility was the one requirement of that
particular medium. Graceful type, or fine paper, would have added
nothing to our enjoyment. On the other hand, graceful type which
was more difficult to decipher would have detracted from our pleasure,
as it would have made the act of reading more difficult, thus thrusting
the medium upon our consciousness, when that consciousness desired
to be alone with the meaning of the printed words.
Parallel cases might be drawn for all other media of entertainment,
to illustrate that the prime necessity is to create the illusion. The
problem of the motion picture is to create the illusion of reality, using
gray shadows as the medium of expression. The effort of many
years in silent pictures has created a technic of skilled photography
* Gramercy Studio, RCA Photophone, Inc.
323
324 JOHN L. CASS [J. S. M. P. E.
combined with ingenious cutting which has proven many times that
a perfect illusion may thus be created. Sound was added to increase
the scope and flexibility of the motion picture as a form of dramatic
expression, and to combine with the picture the ability to cater to the
musical appetites of the public. This musical appetite was demon-
strated by the popularity of the phonograph, followed by the over-
whelming success of radio broadcasting.
Several of the great electrical companies, recognizing the possi-
bilities of the talking picture, developed equipment which made pos-
sible the creation of a new medium of expression, meaning a new form
of illusion. Sounds may be recorded with sufficient fidelity and
strength, and with such accurate directional effect, that the theater
audience of today may forget the medium used, and may lose itself
in absorbing the meaning of the images and accompanying sounds
without being conscious of the medium itself. The popularity of
talking pictures is due to the success of the illusion.
A number of requirements must be met to maintain the illusion.
As in the case of the printed word, the pictures must be easily dis-
cernible, and the sounds easily understood. Intelligibility, and musi-
cal quality, may now be guaranteed, and will be further improved as
the fruits of research come from the laboratories. However, the
greatest strides will come from the development of recording technic.
Now that equipment is approaching perfection, the time has ar-
rived for concentration on the psychological phases of recording, to
the end that inconsistencies may be minimized. Referring to silent
picture methods for a moment, let us consider photographic technic.
Changing of camera angle or camera lens means that the eye of the
observer is being shifted, either in angle or in distance, from the action.
It has been found that the eye of the audience may be moved and by
this means actually enhance the illusion of reality, provided the move-
ment is accomplished judiciously and with definite purpose. It is
quite possible to induce dizziness and nausea in an observer by such
means as photography from the rolling deck of a vessel. Similarly,
cutting from a very long shot to a close-up at the wrong time would
very probably induce an effect of sudden acceleration. There is a
similar situation in the handling of sound records.
Present practice in sound studios involves the use of a number of
cameras, each using a lens of focal length which places the observer
at a very definite point with respect to the action. The extreme
positions would be the long shot, covering the entire set, and the big
March, 1930] ILLUSION OF SOUND AND PICTURE 325
close-up of the principal performer. Contrasted to this, it is common
practice to use a single microphone system, in which a number
of microphones are mixed in the monitor room to attain intelligibility
of speech and good quality of speech and music. When a number of
microphones are used, the resultant blend of sound may not be said
to represent any given point of audition, but is the sound which would
be heard by a man with five or six very long ears, said ears extending
in various directions. This blend of sound may be recorded on several
machines, film or wax, or both film and wax, but the sound record is
the same on all machines. Eventually the cutter will take this sound
record, and will cut from one camera to the other in order to get
the proper picture results. When this scene is projected, the eye will
jump from a distant position to an intermediate position, and from
there to close-up positions on important business. The sound will
run throughout as though heard from the indefinite position described
above. Since it is customary among humans to attempt to maintain
constant the distance between the eye and the ear, these organs
should move together from one point to another in order to maintain
our much mentioned illusion.
My observation has been that this lack of coordination of eye and
ear is the most flagrant fault in sound recording at the present time.
It is particularly noticeable in short subjects of orchestras, where the
close-up camera moves from one instrument to another while the mi-
crophone is recording a balanced blend of the combined instruments.
If one were standing close to the saxophone, its tones would pre-
dominate, and shifting to the violin would have obvious consequences.
Similarly, in dialog sequences, quality and volume remain constant
while the cutter jumps from across the room to a big close-up. At
such times one becomes conscious that he is witnessing a talking pic-
ture, this condition indicating that the illusion has been partially de-
stroyed at that point.
Here it may be asked, "What can be done about it?" It is possible
technically to make sound tracks which will match the camera takes
so that the eyes and ears of the audience may retain their normal po-
sitions. This can be done by using parallel recording channels, with
the microphone on each so placed that the resultant sound tracks will
approximate the effective camera positions desired. This procedure
would require more predetermination of camera angles than is usual
at the present time, and coordination of the camera positions with the
microphone placing. The desired result could be obtained in most
326 JOHN L. CASS
cases by one or two microphones in each channel. In many instances
where volume changes alone will suffice, one recording channel may be
used, with subsequent treatment after the picture has been edited.
Progress along these lines will demand better understanding of
photography by sound engineers, and better understanding of sound
by camera men. Artistic results without the present distractions will
require the following:
1. More accurate and detailed scripts, for technical planning.
2. Complete understanding of plans between director, camera man,
sound engineer, and set designer.
3. Elimination, in so far as is possible, of "ad libbing" by the di-
rector.
If the foregoing conditions are met, the work expended in intelli-
gent planning will remove much of the present load of responsibility
from the shoulders of the cutter, and should react to lower the cost of
production by the minimizing of delays on the set. Sound has al-
ready forced forethought on the makers of motion pictures to the end
that the savings have practically cancelled the cost of recording. This
tendency will continue, and should serve to materially reduce cost
of production as compared to the old silent picture methods of prodigal
extravagance. The talking picture of the future will be engineered
by a team of highly intelligent and cooperative technicians, cinematog-
rapher, and sound engineer, who must have broad vision, and who
must drop, in so far as possible, the prejudices of the past. Rapid
strides are being made in this direction, which augurs well for the
future of the film industry.
FILM NUMBERING DEVICE FOR CAMERAS AND
RECORDERS
M. W. PALMER*
Footage numbering has been used on the edge of motion picture
film for some time, and has proven to be a great aid in cutting and
assembling silent pictures. With the introduction of sound, a sepa-
FIG. 1. Diagram of mechanism of the footage numbering device.
rate film is used for the sound track, and it is very desirable for cutting
and matching that the sound track bear the same numbers along its
edge as does the picture negative. The device, which I am about to
describe, numbers both films in the camera while the picture is being
made, thus substituting for the present numbering system a different
one better adapted to sound pictures.
* Paramount-Famous-Lasky Corp., Long Island City, N. Y.
327
328
M. W. PALMER
[J. S. M. P. E.
This device consists essentially of an illuminated counter, mounted
in a box on the outside of the camera, a lens, and a prism inside the
camera to carry the image of the counter face to the edge of the film.
The counter, lens, prism, and film all move in synchronism about the
same axis, thus making it possible to put the number on while the film
is moving.
Fig. 1 is a diagram of the mechanism. A is the re-set counter, B
is a small lamp to illuminate the face of the counter, C is a lens
FIG. 2. Numbering device attached to camera.
focussed on the face of the counter, and D is a prism which diverts the
light rays so that the image falls on the edge of the film which is rid-
ing on the sprocket E. All these elements are revolving about the
same axis, thus producing an image which is moving at the same angu-
lar velocity as the film which is receiving it.
Fig. 2 shows the device attached to a motion picture camera. The,
cover is removable, so that the counter can be reset to any particular
reading desired.
Fig. 3 shows the camera door open. The member containing the
lens and the prism is screwed on to the end of the sprocket shaft and
March, 1930]
FILM NUMBERING DEVICE
329
the image is projected upon the film through a small notch cut in the
sprocket. A simple catch is provided which drives the part contain-
ing the counter when the door is closed.
For recording systems where the camera and the sound recorder are
run by separate synchronous motors, a slightly different type of
mechanism is used which does not start to number until both
machines have come up to synchronous speed.
The operation of this device in connection with motion picture pro-
FIG. 3. Rotating member of numbering device in position on sprocket.
duction would be as follows. Before starting any particular scene,
the camera men on the set receive their starting number from the re-
cording room, the same as is done at present. Instead of punching this
number on the film, each man sets his counter dial at the starting
number, and when the cameras start each film will be numbered with
the same series of consecutive numbers. After the film has been de-
veloped in the laboratory all that is necessary to do to locate the sound
track belonging to any particular frame of the negative, is to look for
the same number. If desirable, the various cameras and recorders
330
M. W.
[J. S. M. P. K.
can use a small symbol ahead of the numbers which will also identify
the film coming from a particular camera.
It is also possible with this device to put the production number
on the edge of each piece of film by providing another small lens and
j
i
\
FIG. 4. Example of numbering on picture and sound track.
a changeable "slate" in the mechanism itself. This would serve to
completely identify each foot of film as to production, camera, and
corresponding sound track, thus relieving the film editor of unneces-
sary detail, and allowing him to concentrate on the more important
features of his work.
DISCUSSION
MR. COFFMAN: I would like to emphasize as strongly as I can the merits of
this little device of Mr. Palmer's. It is small as far as complication and size go,
but nevertheless it can save a tremendous amount of money for the industry
if adopted. I have done enough editing of sound film to know the difficulty
of handling separate pieces of film from the triple or double rewinders and going
to a great deal of pains to maintain synchronism. The general use of this device
would make it unnecessary to provide starting marks; it would mean that in
addition to footage numbering the camera slate or code representing it could be
recorded so it would be unnecessary to take up film footage by photographing
the slate. Sound track and picture film could be cut into pieces a foot long with-
out difficulty in identifying them.
MR. OFFENHAUSER: There is only one little remark I should like to make and
that is that a recorder takes longer to start up than the camera. How does
Mr. Palmer arrange for the proper starting? Where does he locate the mark?
Here is another point: The camera magazines are not loaded when the sound
magazines are loaded. How about the mark in case film is left in one and not
in the other? Can they stop the feed counter at the end of a shot?
MR. PALMER: As far as the two machines coming up to speed at the same
time, I had that in my paper but skipped it. I have an arrangement whereby
the counter which is on the picture camera and that on the sound camera are
held out of engagement by a magnetic clutch and, when both are up to speed,
March, 1930] FlLM NUMBERING DEVICE 331
the clutches are released simultaneously and the numbering begins with the
same number on both.
As for one camera running out of film and the other having film in it, I am
afraid I didn't make that quite clear in my paper, but regardless of what film
is in the camera, each operator of the picture camera and the operator of the
sound camera have the counter set at the same number before taking is started,
and this number goes on each film and numbering starts from that point. Each
film starts at the same number, and all have the same number along the edge
when they come out of the laboratory.
lato.t sri
WATER COOLING OF INCANDESCENT LAMPS
N. T. GORDON*
INTRODUCTION
The ordinary applications of incandescent lamps in lighting our
homes, offices, and cities seldom bring to our attention or considera-
tion the quantity of heat which is produced as a necessary conse-
quence to the light emitted by incandescent tungsten. However, in
certain special applications of high intensity illumination, such as the
lighting in motion picture studios and the projection of motion pic-
ture films, the intense heat not only is brought to our attention, but is
impressed on our minds through physical discomfort.
The tendency is toward higher and higher intensity of illumination,
and along with the light we get more and more heat which is evidenced
by spoiled make-up and dispositions. Talking and color motion pic-
tures are placing added responsibility upon the incandescent lamp,
and it is the desire to remove, so far as possible, any features which are
objectionable even in special applications. With this aim in mind,
the problem of reducing the heat from incandescent lamps has re-
ceived careful consideration in the research and engineering labora-
tories of lamp manufacturers, and it is our purpose to present a report
of progress on one line of experimentation. It must be emphasized
that the work has not reached a commercial stage, but we are in-
tensely interested in solving the problem, and criticism and discussion
of the present experimental work will be of great value in future de-
velopment, should it progress beyond the laboratory.
ENERGY DISTRIBUTIONS FOR A BLACK BODY AND TUNGSTEN
In order to obtain a clearer conception of the proportion of the total
energy radiated by an incandescent body in the different spectral re-
gions, let us refer to some diagrams and tables taken from the litera-
ture on that subject. Fig. 1 shows energy distribution curves for a
black body at three temperatures. Relative energy is plotted as
abscissas and wave-length as ordinates. The visible spectrum is
* General Electric Co. Research Laboratory, Schenectady, N. Y.
332
WATER COOLING OF INCANDESCENT LAMPS
333
included between the dotted lines and extends from 0.4 micron 1 to
0.76 micron; the infra-red, from 0.76 micron to infinity; the ultra-
violet, from 0.18 micron to 0.4 micron.
It will be noted that the largest part of the energy, as indicated by
the areas under the curves, lies in the infra-red. It is this infra-red
or heat area that we are interested in reducing. As the temperature
TABLE I
Proportion of Total Radiant Energy for Various Lamps (Holladay)
Lamp
Lumens
Emit-
ted per
Watt
/i
Maxi-
mum
Tem-
pera-
ture in
Deg. K.
Average
Color
Temp.
Tc
inDeg.K.
Maxi-
mum
Bright-
ness of
Filament
Candles
/(cm.) 9 -
bi
Probable
Value ol
Factor G
for the
Visible
Spectrum
Proportion of Total
Radiant Energy
Emitted in the
Visible Spectrum
Bv a Black
Body at
Temp. Tc
<i>v
By a Non-
Black Body
Radiator
G<t>v
(Regular gas-
filled tungsten
lamps):
50 watt tung-
sten
10.0
2685
2670
469
1.25
0.07165
0.090
75 watt
11.8
2735
2705
563
1.24
0.07592
0.094
100 watt
12.9
2760
2740
605
1.23
0.08020
0.099
200 watt
15.2
2840
2810
781
1.22
0.08897
0.109
300 watt
16.3
2870
2840
862
1.21
0.09314
0.113
500 watt
18.1
2930
2920
1015
1.20
. 1003
0.120
1000 watt
20.0
2990
2980
1225
1.19
0.1122
0.133
2000 watt
21.2
3020
3000
1350
1.18
0.1151
0.136
(Special tung-
sten lamps) :
1000 watt stere-
optican
24.2
3185
3175
2065
1.16
. 1407
0.163
900 watt movie
27.3
3290
3220
2660
1.15
. 1476
0.170
10 kw.
31.0
3350
3300
3050
1.14
0.1595
0.182
30 kw.
31.0
3350
3300
3050
1.14
0.1595
0.182
of the radiator is raised, the maximum of the energy curve shifts
toward the shorter wave-lengths, and the proportion of energy radi-
ated in the visible region increases. But even at 3000K. the pro-
portion of the total energy radiated by a black body in the visible
spectrum is only about 1 1.5 per cent. Fig. 2 is an energy distribution
curve for a black body at 3500 K. In this case, the curve bounding the
black area is obtained by multiplying the energy radiated in the vis-
1 Micron
1000 millimicrons (m M ) = 10,000 Angstroms (A).
334
N. T. GORDON
[J. S. M. P. E.
ible spectrum by the visibility curve. The proportion of effective
visible light to total radiation is thus still further reduced.
An incandescent tungsten filament has an advantage over a black
body due to its selective radiation, and affords a more efficient source
of visible light, but the proportion of energy radiated as heat to that
radiated as light is still large. The proportions of total radiant energy
emitted in the visible spectrum by tungsten lamps are shown in Table
I taken from calculations published by Holladay. 2 These figures
/.S 2 ZS 33.54 45
WAVE: LENGTH
FIG. 1. Energy distribution curve of a black
body for different temperatures.
show 9 per cent of the total energy radiated by a 50 watt lamp in the
visible spectrum, and 18 per cent for a 10 or 30 kw. lamp. Reference
will be made later, in connection with water cooling, to a 1500 watt
lamp, and it should be noted here that less than 1.0 per cent of its
radiant energy is in the ultra-violet, 13.5 per cent in the visible, and
about 85 per cent in the infra-red spectra.
In round numbers, 85 per cent of the energy radiated by a 1500 watt
tungsten lamp is in the infra-red region, and constitutes the heat which
we desire to eliminate.
1 HOU,ADAY, L. L.: "Proportion of Energy Radiated by Incandescent Solids
in Various Spectral Regions," /. 0. 5. A., 17 (1928), p. 329.
March, 1930] WATER COOUNG OF INCANDESCENT LAMPS
TRANSMISSION CURVE FOR WATER
335
In any consideration of the elimination of heat from a beam of light,
one thinks immediately of the water cell. The International Critical
Tables (Vol. 5, p. 269) provide data for the transmission of water,
and Fig. 3 is plotted for a layer of water 1 cm. thick. As is shown by
the curve, the transmission of 1 cm. of water is high for the ultra-violet,
and 99 per cent or more through the visible spectrum. At Ifi it falls to
66 per cent. Beyond lju there is one slight rise, but the transmission
V*
/o-
V C}=3.67 XT'* WATT C
FIG. 2. Energy distribution curve for a black body at 3500 K.
then falls rapidly to 30 per cent at 1.24^ and at I AH is only 3 per
cent. At 1.5/j the transmission is practically zero. In other words,
water is a very suitable absorbent for heat and has an excellent trans-
mission for visible radiation.
EXPERIMENTS ON RELATIVE ABSORPTION OF LIGHT AND HEAT
The preceding paragraphs have indicated that it should be possible
to remove much of the heat from an incandescent lamp by means of
a water cell a centimeter or two thick with the loss of but very little
light. Data will now be presented showing the relative transmission
of light and heat in experiments made in the laboratory with not only
water, but also copper chloride solutions as the absorbing media. The
first experiment measured the per cent of light and heat from a 400
watt projection lamp transmitted through a water cell one centimeter
thick between parallel glass plates. The second experiment involved
measurements on a 150 watt lamp operating in air within a double
336
N. T. GORDON
]J. S. M. P. E.
walled cylindrical glass jacket. The space of 1.7 cm. between the
double walls was filled in turn with water, 0.5 per cent CuCl2 solu-
tion, and 1 per cent CuCl 2 solution. The visible light was measured
with a photometer, and the radiant energy by means of a thermopile
and sensitive galvanometer.
Table II contains the results of these experiments, the data for the
400 watt lamp being kindly furnished by Dr. G. R. Fonda, and by
Mr. F. A. Benford and Dr. S. Dushman for the 150 watt lamp. There
appears to be some discrepancy for the values obtained with water,
10
.9
.8
.7
.6
.5
.4
.3
.Z
.\
]
1
* '
\
\
i
v
.[
\
z
^o
in
\
/ \\
\\
TRANSM1S
\\
\
\
V
VW
ML LENGTH - MICRONS
i 1
N
^J
0.1 .Z .3 .4 .5 .6 .7 .8 .9 1.0 11 1.2 1.3 U IS
? IG. 3. Transmission of 1.0 cm. of water (International Critical Tables).
but I think these may be explained as being due to different experi-
mental conditions. The fact which is most striking, however, is the
advantage of a copper chloride solution over water for the relatively
high ratio of absorption of heat to light. A layer of CuCl 2 1.7 cm.
thick transmits only 8 per cent of the radiant energy for constant
light intensity, and this 8 per cent must lie almost entirely in the
visible spectrum. However, as is so often the case, certain difficulties
must be overcome before copper chloride may be used satisfactorily.
These difficulties include hydrolysis of the salt, corrosion of metal
parts, and the formation of deposits when slight evaporation occurs.
It seemed expedient, therefore, to proceed experimentally with a unit
using water as the absorbing medium.
March, 1930] WATER COOUNG OF INCANDESCENT LAMPS 337
AN EXPERIMENTAL WATER COOLED UNIT
The unit at present in the process of development consists of a lamp
immersed directly in the absorbing liquid which is confined by an
outer glass jacket. A cooling coil through which tap water is cir-
culated is also immersed in the absorbing liquid. Convection currents
set up within the liquid are sufficient to maintain a circulation, and
no mechanical stirring is necessary. The lamp, cooling coil, and outer
jacket are all supported from a base plate on which the lamp socket
is mounted. Two gaskets, one between the base plate and the jacket,
and the other between the base plate and the lamp at a point just
TABLE II
Results of Experiments on the Absorption of Heat
Light Source
Absorbing Cell
Light
Transmitted
Radiant
Energy
Transmitted
Radiant
Energy for
Constant
Light
400 w. or 150 w.
lamp
None
100%
100%
100%
400 w. proj . lamp
1 cm. H2O; parallel plates
89%
23%
26%
150 watt lamp
1.7 cm. H2O; cylindrical
87%
29%
33%
150 watt lamp
Va% CuCl 2 ; cylindrical
85%
10%
12%
150 watt lamp
1% CuCl 2 ; cylindrical
78%
6%
8%
below the base, make the unit water tight. Fig. 4 is a photograph
of a unit for a 1500 watt lamp. The base plate is five inches in diame-
ter, the outer jacket four inches in diameter, and the over-all length
fifteen inches. Nine turns of 0.25 inch copper tubing serve as the
cooling coil.
This type of arrangement has several advantages. The absorbing
layer of water practically surrounds the light source so that almost no
radiation reaches the atmosphere of the room except through the ab-
sorbing medium. Cooling water is circulated in and confined by the
coil so that either distilled water or some heat absorbing solution may
be kept permanently in the jacket. The jacket and lamp surfaces
are thus kept clean and free from the deposits of ordinary tap water,
although tap water is the cooling agent. Another advantage is the
possible use of smaller bulb sizes. The temperature of the bulb is
not a limiting factor in this case.
In one experiment, a 1500 watt, 115 volt filament was mounted in a
special 2.5 inch tubular bulb, and this lamp placed in a unit as shown
in the photograph. Measurements were made of watts input into
338
N. T. GORDON
[J. S. M. P. E.
the lamp, energy dissipated in the circulating water, and light output.
The energy dissipated in the circulating water was determined by
carefully measuring the rate of flow and the temperature of the in-
coming and outgoing water. Conversion from the calories so obtained
to watts showed that 75 per cent of the watts input was dissipated
in the circulating water. Candle power measurements were made on
the horizontal photometer, and also in the spherical photometer.
Readings were taken both with and without the water jacket
attached to the unit to determine the amount of light absorbed by the
FIG. 4. A 1500 watt water
cooled lamp unit.
combined water and jacket. These figures are presented in Table III
and show 93 to 95 per cent light transmitted. Seventy-five per cent
of the total energy is dissipated by the cooling system. The lumen
output from the complete unit with water cell, base plate, coil, and
base is 80 per cent of that from the bare lamp without a fixture. This
figure is subject to a revision of a few per cent because an oxidized
fixture was employed in the spherical candle power measurements.
In order to maintain an illumination from the water cooled lamp
equal to that from the 1500 watt lamp without the water jacket it would
be necessary to increase the watts in the water cooled lamp about
March, 1930] WATER COOLING OF INCANDESCENT LAMPS
339
72
70
66
66
64
62
60
56
56
54
52
50
48
46
44
42
40
4
78
77
76
75
74
73
7Z
71
O 70
I.HR.
\
1 *
4*2 O.D. WATER CELL
^COIL 1295Q.IN.
AUQUST 28, 1929.
N
1 I
1 5
a ?
II
\\
\
\
\
\
:t
%
J
L
\
I
\
&
^^ g
*
-o
%
-( '
-a^
-"^
>-
1
\
S
\j
y^
^
^^
****
a
^
^
^>
^^
^
%
=
l
R
1
6.TE. <
\
>F ri
' o
OW (
! ii .
C PE
.
* Ml
**
N.
-^
*-*.
*
- .
e-
aoo so* TOO 300 uoo 1300 iwo noo isoo zioo z*oo esoo zroo 2900 3100 3300 350
QAL . PH HR. ZO G At PER HR. 46 QAU.PEf
TEMR H 2 16'C.
FIG. 5. Kffects of rate of water flow on cell temperature and on ratio of
energy dissipation to energy input.
TABLE III
Results of Experiments on the Absorption of Heat
Light Source
1500 watt special
1500 watt "
1500 watt "
Absorbing Cell
None
2.2 cm. H 2 O; lamp
inH 2 O
2.2 cm. E^O; lamp
inH 2 O
Light
Transmitted
100%
93 (H.C.P.)
95 (S.C.P.)
Per Cent Watts
Dissipated in
Circulating
Water
75%
75%
Radiant
Energy for
Constant
Light '
100%
27%
26%
340
N. T. GORDON
[J. S. M. P. E.
50*C
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
xn
y
4iO.D. WATER CELL
i'CoiL 129 SQ. IN.
AUGUST 29,1929.
i
?
/
/
/
/
v
/
U
/
/
>
u
<
.
/
1
-fc
/
/
/
,1
\
/
/
y
*
/
TEMP. HgO 16C. RATE OF FLOW CONSTANT AT so cc5w.
WATTS IN LAMP
Fig. 6. Effect of wattage input on temperature of water cell.
2.5 to 3.5 per cent. The total radiant energy from this water cooled
lamp would then be 26 to 27 per cent of that from the bare lamp as
indicated in the last column of Table III.
March, 1930] WATER COOLING OF INCANDESCENT LAMPS 341
Fig. 5 shows the effect of rate of flow of the cooling water on the
temperature of the water cell, and also on the ratio of watts dissipated
in the circulating water to watts input into the lamp.
It will be noticed that it is of little utility to increase the flow of
water above 1500 cc. per minute. At this point, 75 per cent of the
watts are dissipated in the circulating water and the temperature of
the water cell is 44C. At a flow of 3500 cc. per minute, the watts
dissipated increase only 3 per cent and the temperature of the cell
falls only 2 degrees.
The effect of change of wattage in the same lamp on the tempera-
ture of the water cell is plotted in Fig. 6. This curve indicates that it
may be possible to operate a lamp of 1700 watts in a 2.5 inch tubular
bulb.
SUMMARY
An experimental device is described for absorbing and removing
heat from incandescent lamps by means of a water cell surrounding the
lamp. Ordinary tap water flows through a cooling coil immersed in
the cell and dissipates 75 per cent of the total watts input for a 1500
watt, 115 volt lamp. The loss of light due to the water cell is 5 to
7 per cent. These figures give some idea of the result obtained by
water cooling incandescent lamps, but an actual personal exposure
to both the regular and experimental lamps affords the only satis-
factory means of comparison.
DISCUSSION
MR. EGELER: The problem of taking care of the heat from the light source
is not one which has given concern with the ordinary lighting intensities, but in
motion picture projection it has been a subject of discussion previously. A
number of years ago some publicity was given to the removal of heat from the
light beam in connection with motion pictures of medical work where the effect
of this non-luminous radiation was destructive to the specimens. For many
years, of course, we have used water cells in slide projectors, and in motion
picture photography the problem has come up with the changes in operating
practice. With the coming of sound pictures most of the old studios, modified
to sound practice, had inadequate ventilation; in the new studio design condi-
tions are made much better by providing adequate ventilation without the noise
of ventilating fans. There are several methods of attacking this problem:
First, the scheme referred to, taking out the heat with adequate circulation of
air. The second way would be to take the heat out of the light beam by putting
an absorbing medium, such as glass, on the front of the lighting units, so that
the radiation directed toward the actors could be filtered and the heat
of the unit removed. The remainder of the radiation would be taken care of by
342 N. T. GORDON [J. S. M. p. K.
the ventilation. A third method would be to absorb all of the heat in some me-
dium and remove it from the studio; that is what Dr. Gordon's development
does. It actually filters most of the heat radiated by the lamp and by means of
circulated water conducts it away from the set. There are present several
limitations from the standpoint of operating practice which our studio friends
know more about than I do; I had best let them talk on these phases.
MR. MOLE: While the heat coming from the incandescent lamp, when a con-
siderable number are used in a poorly ventilated stage, has been a source of in-
convenience to the production studios, I doubt very much whether the studios
would be willing to relieve this situation by bringing in additional equipment
necessary with a water cooled lamp, as outlined in Dr. Gordon's paper. However,
such a lamp would find many applications where the placements are of a per-
manent or semi-permanent nature; such as operating rooms in hospitals, still
and portrait studios, and for close-ups in connection with regular motion picture
productions. Many mediums such as clear glass, Florentine glass, and silks are
now being used in front of the lamp, which have the effect of absorbing some
portion of the heat as well as diffusing the light. I believe that the development
work along lines which Dr. Gordon is doing is of very great value and should be
carried on, and no doubt in future studio design, provision could be made to
accommodate a water cooled incandescent lamp.
We have many members present who are engaged in the operation of the
electrical departments of the various studios, and I believe we should hear from
them on this particular problem.
MR. PALMER: It seems to me that two very serious objections to this water
cooling proposition are, first of all, the element of danger, with so many lamps
operating on a set and the necessity for having water flowing through each one
in order to keep it from exploding. If the water in the lamp started to boil,
the condition would become very serious; it is not always possible to keep water
flowing in two or three hundred lamps on the same set. Another objection
would be the additional expense for hose and other auxiliary equipment going
along with this arrangement. One of the reasons for using incandescent lamps
is that they make studio operation more flexible. We can dress a set more
quickly and strike it more quickly with incandescent lamps. Mr. Buck has
told us of a system to eliminate the use of choke coils on lamps. The tendency
in studio operation in the last two years has been toward simpler and more
economical methods, and anything which will tend to work in the other direction
would not be desirable.
MR. FARNHAM: I should like to call attention to one variation of the water
cell and that is the possibility of cooling the water in the vicinity of the apparatus
by some means such as a radiator and depending on natural circulation of the
water caused by difference in temperature between the cell and radiator. There
is a great deal of good circulating air in the more modern sound studios, and'
such an arrangement would do away with the need for hose connections.
All that is necessary is to keep the water below the boiling point. The use
of solid filters, such as glass, has been considered. One of the difficulties
with some of the glasses is that they alter the color quality of the light,
and any glass absorbing heat becomes hot itself, and there is the problem
of dissipating heat from the glass, which may be done with air. The glass
March, 1930] WATER COOI.ING OF INCANDESCENT LAMPS 343
is put in, in strips, so that inequalities in temperature causing unequal ex-
pansion do not crack it.
MR. EDWARDS: I think that some years ago some experiments were made on
artificial cooling with the same general ideas that we have seen this morning.
At that time, a modification of a thermo-syphon system was used, and I wonder
if anybody has ever tried the idea of a modified form of refrigeration, such as
that used in a gas operated refrigerator, for the purpose of keeping a lamp cool.
That might be actuated by the natural heat of the lamp itself. I think it is a
line on which research might be done.
DR. GORDON: I should like to make a few remarks on some of the objections
that have been raised to the water cooling of incandescent lamps. We cannot
expect to eliminate the heat by means of water without encountering some
difficulty. The question to be answered will be: "Can the water cooling be
made so convenient that the objections to it will be more than compensated
for by the reduction in radiant heat?" It is thought that the water leads can
be combined with the electric leads so that only one cable will be necessary.
When a medium, such as silk, is used before the lamp a loss of more than 50
per cent of the light has been observed so that heat is eliminated only at the
expense of a very considerable amount of light. It is thought that a water cell
cannot be used in the beam satisfactorily unless the cell is water cooled. Other-
wise trouble would be experienced due to leakage caused by excessive expansion
and contraction of the cell. Since we have to use water connections to cool a
cell placed in the beam, it would seem better to surround the entire lamp with
the water cell and take care of all the radiation.
The installation of ventilation systems has been mentioned. In this case, it
might be the cost of the ventilation systems against the cost of water cooled
lamps, and in some instances ventilation systems might not be required.
A ventilation system does not remove the heat from the beam of radiation. Certain
lamps which are not movable afford a very convenient place for water cooling
since the water leads would not have to be carried around.
In regard to the risk of explosion, we have let lamps operate without circu-
lating, the water. The water heats up, starts to boil, steam escapes through the
gaskets, and if you let this continue the lamp bulb will crack when the water is
about half evaporated. So far we have had no outside jacket break and have
experienced no trouble from explosion.
THE DEVELOPMENT OF TELEVISION AND RADIOMOVIES
TO DATE
C. FRANCIS JENKINS*
Radiomovies for entertainment in the home have progressed rather
satisfactorily during the year. Our audience on 46 meters has grown
in a year to some 18,000 or 20,000. To distinguish them from the
radio fan with a set which covers only the entertainment band from
200 to 550 meters most of this audience are known as amateurs.
This limitation of visual radio to short wave channels comes about
because the Federal Radio Commission does not at present permit
visual broadcast in the audible entertainment band. That is the
reason we cannot encourage the purchase of a television attachment
for your present set.
The surprising quickness with which our radiomovie audience has
been built up is largely accounted for by the fact that the amateur
already had his radio set for code communication on 40 meters, and
all he had to do was to attach a radiovisor to his receiver, tune 6
meters farther along on his dials, and pick up our radiomovies, broad-
cast from W3XK, Washington. Because we published a broadcast
schedule on which he could depend, he rigged up his visual radio re-
ceiver with confidence.
Our broadcasts were well received rather widely over the United
States, very dependably as far west as Denver; occasionally we got
reports from California, Canada, Cuba, and Porto Rico of reception
on the 46 meter channel. But as 46 meters gave double images in local
territory, we also simultaneously broadcast on 186 meters for Wash-
ington, Baltimore, and other nearby receivers. As with audible radio
there are locations in which reception is better than in other places.
An amateur in Cold Springs, Iowa, explained that he happened to
tune in on our initial radiomovies broadcast, July 2, 1928, and that
he had missed very few of our broadcasts since, and then only because
of absence from home at our broadcast hour. We believe his re-
ports authentic for we have checked him up; which we easily do by
* Jenkins Laboratories, Washington, D. C.
344
TELEVISION AND RADIOMOVIES 345
comparing reports from amateurs with the order of picture sequence
in the broadcast on that particular evening.
All the broadcasts have been in photographic silhouette, or in black
and white cartoon drawings. But those cartoonists we have patron-
ized don't seem to be able to grasp the requirements of radiomovies,
and so, after spending considerable money with them, we abandoned
the cartoonist as an undependable source of picture story for us.
I had, however, designed a silhouette studio equipment which was
already working excellently, and with which we can produce radio-
movie stories in silhouette as fast and as satisfactorily as is usual with
regular movie negative in regular movie studios, and at small cost.
When I first designed this equipment and worked out the operation
methods, I really did not think of it as new ; but it seems on search of
available motion picture references that this is a new attainment.
We also discovered scenario writer talent in our laboratory staff,
and so we are a self-sufficient institution, from story concept to the
reproduction of this movie story in your house, delivered there over
radio channels.
All of these broadcasts were on ten kilocycle channels. Some
months ago the Federal Radio Commission, on the showing of what
we had already accomplished, and the explanation that radio trans-
mission of the halftones of television and regular theater movie
film required a broader channel than the ten kilocycle width employed
in audible radio, set aside eight channels, each one hundred kilo-
cycles wide for visual radio.
We then immediately proceeded with the erection and equipment
of a powerful station in the country about five miles north of Washing-
ton. The broadcast frequencies were 2850 to 2950 kilocycles and
2000 to 2100 kilocycles, for distant and for local reception, respec-
tively. This station's broadcasts are well received by those who have
rebuilt their radio receivers for the new frequencies, but I am doubtful
that we shall build up as large an audience on these frequencies as
quickly as we did on the old frequencies.
Of the little kit set receivers we sold many thousands at $2.50 each.
They cost $3.10, but I made money because I sold so many of them.
That is literally true, for we built up a demand for a better receiver,
and a public confidence that television and radiomovies was a prac-
tical thing, possible of wide usefulness as development progresses.
To date, the quartz or glass rod drum scanner continues to represent
the best type of receiver. It makes a larger and brighter picture with
C. FRANCIS JENKINS [J. S. M. p. E.
simpler mechanism, and less amplification, than any other form yet
produced.
How long it will remain the best form of receiver no one knows, for
thousands of engineers, my own staff included, are feverishly at work
on the problem.
A different type of receiver is used on occasions, namely, the lens
scanning disk (U. S. patent No. 1,679,086) used in the General Electric
television demonstration at the New York Radio Show last winter.
This receiver with a high intensity neon light source projects a rather
creditable size and brightness of picture, as those of you who saw it
will remember.
But all the different mechanisms demonstrated to this time have
a common limitation, fatal to extended development, in this art,
namely: they all depend upon persistence of vision for success.
While interesting results have been attained with the old scanning
disk, there is not much opportunity for extended practical develop-
ment.
It is quite surprising to figure out the efficiency of the light source
on the eye of the observer, and find that it is only about one-fifty
thousandth (1/50,000) of one per cent, which probably accounts for
the slow development of this art.
This extremely low efficiency comes about because of two basic
errors of concept of the problem involved, namely: (1) that each
elementary area light-source should be at least as large as the whole
area of the picture itself; and (2) that persistence of vision of the
eye should be depended upon for an assembly of the elementary areas
of the picture.
Theoretically, (a) no more light-current is actually required than
that needed to illuminate a single elementary area at any moment
considered ; and (b) a real picture should exist in the receiver whether
there is a human eye to see it or not, that is, it should be possible to
photograph the received picture with a snapshot camera. This
cannot be done with the disk scanner method.
Plate Receiver. The plate receiver, however, is designed and built
to embody both these essentials and consists of a picture plate divided
into 2304 elementary areas, that is, 48 lines with 48 picture elements
in each line.
In the construction described the picture area consists of 48 hori-
zontal rows of flash-light lamps, with 48 lamps in each row. These
lamps are inserted in a corresponding number of holes in a plate sup-
March, 1930] TELEVISION AND RADIOMOVIES 347
_-
ported, preferably, in a vertical position, each lamp being an ele-
ment of the picture.
The lamps are divided, electrically, into four banks. Bach lamp
is individually wired to its particular contact of the switching gear.
All the lamps in each bank have a common return connection, and
the lamp face is, for certain uses, covered with ground glass or the
like, for soft diffusion in the finished picture.
The switching gear is a four-part device, each of the parts being
connected to its particular bank of lights. Such a division permits
the construction of a commutator but one-fourth as large as if it were
a single commutator structure. A 3600 rpm., 1 /z hp. synchronous
motor is quite suitable for driving the commutator brush in city
service.
In operation, the motor being started, the incoming amplified
radio signals are distributed to the several lamps in succession, fully
lighting some of them, lighting others to partial brilliancy, and leav-
ing others unlighted. The result is a picture built up in lights and
halftones and shadow on the face of the plate, or the glass diffusion
cover.
The picture on the plate is made up of glowing lamp elements, which
persist in light value for an appreciable time, say, a tenth of a second.
But as the exciting impulse is applied every fifteenth of a second, the
lamp is aglow for the whole time the corresponding elementary area
of the scene at the transmitting station is alight.
That is, in this scheme, persistence of light is substituted for per-
sistence of vision, and the whole of the received picture is on the plate
all the time instead of only a fractional part (l/2304th) an elemen-
tary area time of the picture.
The amount of light available is the average light of a single lamp
multiplied by the number of lamps. The average light of a single
lamp can be approximately the normal lumens of the lamp because
it can be flashed with a very much higher voltage than if the voltage
were applied continuously.
Assuming a l / 2 inch diameter lamp, the multiple lamp plate would
be 2 X 2 feet square, as we built it. In front of this light source a
lens is mounted for projecting it onto a theater screen. As the light
source is the picture itself, the only loss of light in the projection is
the reduction in foot-candles which results from the magnification.
And fortunately the light is the usual color, that is, white light, not
the pink light characteristic of neon.
348 C. FRANCIS JENKINS
Such a receiver-projector will ultimately enable the producer to
distribute motion pictures to the theaters by radio instead of film,
doing away with the present profit-consuming film exchange.
A transmitter is also made on this same principle, in which light
sensitive elements are substituted for the lamp elements in the
receiver.
I am confident this principle, broadly illustrated and first described
by me in The Electric Engineer, of July 25, 1894, will ultimately be
universally adopted. I am encouraged in this belief because the Pat-
ent Office has officially declared eleven other inventors to be in inter-
ference with my application.
A NEW METHOD OF BLOCKING OUT SPLICES IN SOUND
FILM*
J. I. CRABTREE AND C. E. IVES
A splice in motion picture film which bears a sound record usually
introduces extraneous noise in the reproduced sounds unless some
means is taken to obscure it. Rapid variations in light transmission
of the sound record area are productive of sound and the reproducing
equipment is, of course, unable to distinguish between the record
proper and such extraneous variations.
It is not difficult to see that a badly aligned splice surrounded by
cement smears, finger prints, abrasions, and dirt spots could produce
noise. Even though the splice is made with the greatest care and pre-
cision, however, a very objectionable noise might be introduced as a
result of the passage of a splice joining parts of the sound record be-
tween which there is an abrupt change in transmission. This condi-
tion is liable to be encountered even if the method of joining were
capable of eliminating all other mechanical imperfections such as
roughness of the cut edge and light loss produced by refraction at
the edge. Therefore, noise will be produced if the change in trans-
mission between the contiguous areas is large and abrupt enough to
come within the range of the reproducer.
If the transmission of the area illuminated by the slit in the repro-
ducer is reduced gradually until it is insignificant at the time when the
splice passes, then no noise will be made by the splice in passing. The
rate of decrease of transmission must be less than that corresponding
to the minimum frequency attainable in the reproducer system.
Remedy for Splice Noise. It has been found possible to eliminate
the splice noise by applying an opaque coating to the sound track
(Fig. 1) in such a way that as the film travels past the slit the effective
transmission is gradually reduced to a very small value and then in-
creased in the same manner. 1 It is much easier to apply an opaque
coating in the shape of a wedge than to vary the thickness of the coat-
* Communication No. 411 from the Kodak Research Laboratories.
1 Movitone Bulletin, 1, No. 31 (Aug. 4, 1928).
349
350
J. I. CRABTREE AND C. E. IVES [j. s. M. p. E.
ing, so the overlay usually is made to resemble a ten to forty cycle
variable area signal.
When a splice is "inked out" or "painted-out" in this way in the
negative, it leaves an area of high transmission in the positive which
is very easily scarred so that it might cause ground noise. In the
positive, the "paint-out ".does its work very well. India ink has been
used in this way but becomes brittle and develops very noisy cracks.
An opaque lacquer has proven more satisfactory.
Improvement in the Method of Masking Out. In a processing labora-
tory it is quite possible to make good "paint-outs" by applying a
black lacquer with a fine brush either with or without the assistance
of a stencil. In the hands of a skilled worker making many hundreds
FIG. 1. A typical "paint-out."
in a day, this method has proven satisfactory, but in the projection
room of a theater different conditions exist. It is often necessary for
the projectionist to make a number of splices in a few minutes when a
new picture is received, and since he is not doing the brush work fre-
quently, it is difficult for him to make a satisfactory "paint-out"
quickly with the result that more noise is liable to be introduced by
a poor "paint-out" than would have resulted from the splice in the
first place. It was obvious that the solution of this problem lay not
alone in the use of a quick drying lacquer, but in devising a rapid
method of applying it.
Various types of stencils constructed of the following materials
were tried: cardboard, rubber, inking roller gelatin, steel and rubber
plated metal and steel. A slow drying lacquer or ink could be used
with any of the above devices, but in the case of rapidly drying lac-
quers, if the brush contained sufficient liquid to make the film opaque
with one or two applications, the more mobile, rapidly drying inks
were sucked in under the edge of the stencil by capillary attraction,
March, 1930] BLOCKING OUT SPLICES IN SOUND FlLM 351
and a very irregular edge was produced. This effect did not occur
when a thick lacquer was used, or when very small quantities of the
thin lacquer were applied repeatedly, but this procedure was so slow
as to be of no advantage. It was then considered that an opaque
sticker or patch of suitable material and design could be applied
rapidly enough for this purpose. A gummed paper patch was first
tried. This could be applied readily and eliminated the splice noise,
but became brittle and sometimes peeled off after the film had been
projected a few times.
Decalcomania transfers were also tried but found unsuitable.
These transfers as purchased consist of a sheet of material, 0.001 inch
thick, attached to a thick paper. They are soaked in water and the
transfer then floated off onto the gelatin coated side of the film. This
type of patch dries too slowly and does nbt become intimately at-
tached to the film in the region of the splice, because there is no fusing
together as with a cemented patch.
An opaque film was then made by incorporating dye and pigment
in motion picture film base, but when the cement was applied to
patches made from such film they curled excessively. A critical
thickness of four-thousandths of an inch was necessary in order to
prevent curling. This thickness was considered excessive. If the
film base was coated with a gelatin layer, this materially reduced the
curling tendency.
The film patch material finally adopted consisted of clear film base,
emulsion-coated, and rendered opaque by exposure and development.
A film of minimum thickness (0.003 inch) was chosen so as to conform
readily to the irregular surface of the splice and prevent the splice
from becoming too thick and stiff.
This type of splice (Fig. 2) was very successful. The patches were
tested by applying them over splices in a positive film which was then
run through a projection machine until the film broke down com-
pletely. The patches were intact up to the time when the perfora-
tions commenced to fracture at the corners.
The Splicing Operation. The patch is applied with the aid of a
registration block shown in Fig. 3. This consists of a bed plate fitted
with registration pins and a pressure platen fitted with a rubber pres-
sure plate. The platen is hinged to the bed and the rubber pressure
surface is cut out so that it fits closely around the pins.
The motion picture film is placed on the registration block with the
support side up and that side of the strip which bears the sound record
352
J. I. CRABTREE AND C. E. IVES [J. S. M. P. E.
FIG. 2. The patch with and without finger tab.
in engagement with the four pins. The splice is placed at or near the
center of the block. The pins fit the perforations so closely that
pressure clips for holding the film in place are unnecessary. When
the film is in position on the block the patch is picked up and held at
one end by means of tweezers or an attached tab while cement is
applied to the side which is to come in contact with the film strip.
The cement application is accomplished by a single stroke of a soft
cementing brush of medium size. The patch is placed immediately
on the registration pins, the pressure plate brought down, and held in
position for about five seconds.
FIG. 3. Registration block showing film and patch in position on pins.
March, 1930] BLOCKING OUT SPLICES IN SOUND FlLM 353
The patch which proved most successful was so made that it covered
the entire width of the sound track completely and extended as far
as possible toward the center of the film strip without entering the
picture area. Some of the factors which entered into consideration
of the best design for the patch are discussed below.
Design of Patch. As mentioned above, the patch or a "paint-out"
performs its function by masking off an area of sound track of vary-
ing width so as to reduce the total transmission of the area illuminated
by the slit in the reproducer at a rate which is insufficiently rapid to
cause the recorder to generate an audible sound, and then, when the
splice is past, uncovering the track in a like manner.
The reproducers now in use are capable of generating sounds of a fre-
quency not less than 20 to 50 cycles per second. Therefore, if the splice
is to be designed so that it will cause no noise of itself, it should vary
the transmission as it would be varied by a signal whose frequency is
not more than 20 cycles. Such a signal would be represented by a
patch whose contour would be described by a sine curve of an ampli-
tude corresponding to full modulation. Its length for 20 cycles would
be
18 inches
20
= 0.9 inch.
Now it might be argued that this length causes a noticeable dis-
continuity in the sound. This is not so serious as might seem. A
patch having straight instead of curved sides has been considered be-
cause it is much more easily made, especially if it is to be cut by hand.
If the patch is shorter (about one-half this length, as has been recom-
mended), the harmonics introduced by using a straight edge for the
cut-off as an approximation for an edge of curved contour, are of a
higher frequency and therefore more prominent. Also, the funda-
mental is well within the range of the reproducer.
The following tests were made with a view to arriving at a design
which would be a compromise between one which would be audible
and one which would obscure too much of the sound record.
A number of patches having dimensions indicated in Fig. 4 as
shown in Table I were made and applied to (1) an oscillator record of
low modulation (frequency 540 cycles) ; (2) a strip of clear film of
density about 0. 1 ; and (3) a strip of film flashed and developed to
produce a uniform density of about 0.7. In each of these films two
splices were made with 5 feet of film between them and then 17 feet
354
J. I. CRABTREE AND C. B.
[J. S. M. P. E.
were skipped before another splice was made. The first splice was
left bare, the second was covered with the patch, and then 5 feet be-
yond the second splice a patch was mounted at a point where there
was no splice. In this way each of the patches in the table was pre-
pared for test. In order not to have any bad corners it is desirable
to avoid cutting across perforations so that the choice of lengths is
limited.
TABLE I
Experimental Patch Dimensions (See Fig. 4)
Patch No.
A
B
C
1
0.09 in.
0.29 in.
0.10-0. 12 in.
2
0.1875 in.
0.65 in.
0.10-0. 12 in.
3
0.1875 in.
1.00 in.
0.10-0. 12 in.
4
0.1875 in.
1.40 in.
0.10-0. 12 in.
The tests were made by running these strips through a standard
type of reproducer operated at a normal gain setting. The modula-
tion of the oscillator record was such as to produce at this gain setting
a volume corresponding to normal speech. The noise from a well
made splice, made with a widely used mechanical splicing machine,
was plainly audible.
In general, the noise produced by a plain splice was least noticeable
in the oscillator records, more noticeable in the 0.7 density, and most
in the 0.1 density film. The patch number 1 produced a plainly
D D
FIG. 4. Dimensioned sketch of patch.
audible sound, number 2 was somewhat less loud, and numbers 3 and
4 were only just audible on the 0. 1 density film and apparently about
equally effective.
Numbers 3 and 4 were noticeable because of their obscuring the
oscillator record for a perceptible duration of time. Number 2 did
March, 1930] BLOCKING OUT SPLICES IN SOUND
355
not cause a noticeable interruption. The best length of patch is
therefore indicated by number 2 or 3. number 1 being noisy of itself
and number 4 interfering with the record for an unnecessarily long
period of time. With reproducing systems which are capable of
reaching 20 to 30 cycles it is necessary to use the number 3 size, be-
cause the smaller patches make an offensively loud sound.
The patch should cover the splice at the widest point. This con-
FIG. 5. Spliced film with patch.
dition is satisfactorily fulfilled when the sound track is completely
obscured for a distance equal to 0.098 inch each way of the center
line of the central perforation (Fig. 4 at A ) . This allows for the stand-
ard "full-hole" splice. It is advisable to have the patch extend in-
ward almost to the picture frame. Then there is no danger of leaving
part of the splice uncovered through an inaccuracy in mounting the
patch.
A total length of 1.00 inch was found best because of these con-
siderations. A spliced sound record film fitted with the patch is
shown in Fig. 5. The sloping sides have a length along the sound
track of, in this case, 1.00 - 0.1875 = 0.8125 inch, or 0.4102 inch
356 J. I. CRAETRE^ AND C. E.
each. This is slightly shorter than that for the one-half wave length
at 20 cycles (0.45) and corresponds to a frequency of about 22 cycles.
The patch is very much easier to handle if it is supplied with a
finger tab, consisting of a strip of stiff cloth attached with a non-per-
manent adhesive. (See Fig. 2 at left.) The tab is readily removed
in the same manner as ordinary surgical adhesive tape.
A LIGHT INTENSITY METER
J. L. McCOY*
Ever since the beginning of photography, the judging of light value
has been one of the great problems, to the photographer or camera
man. In many cases in the past as now, the person responsible for
taking of pictures is required to judge light values using his naked eye
as an indicating means. His accuracy or ability to do this is the prod-
uct of his appreciation and his experience as received through this
natural indicator. The unassisted eye at its best is considered un-
stable with a possible error of 100 percent or more from day to day when
used as a light intensity measuring instrument. It is unreasonable
to expect that two or more men would come very close in a simultane-
ous check. In order to assist the eye in measuring light and to obtain
consistent results, several types of photometers have been developed.
In most cases, these instruments are rather awkward to use because
they require a comparatively slow process of matching of light inten-
sities, to obtain a reading. Therefore, they might be classed as
laboratory equipment, from a studio standpoint, rather than practical
and portable direct reading indicators.
As a natural result, there has been a need for a studio type of pho-
tometer that could be worked, set up, and read quickly without mak-
ing adjustments. For this reason, the Westinghouse Lamp Company
and the Westinghouse Elec. and Mfg. Company have designed this
new tool, to place in the hands of the photographer or camera man
to assist him in his work.
This new indicating electrical eye should have the same value
to the camera man as the slide rule to the engineer. It is a quick
reading light yardstick as simple as a voltmeter to read. As this is
a very new development, we are not sure just what the possibilities
or limitations of this device might be, but it is felt that it has a wide
application in the motion picture and other photographic industries.
This meter is self-contained and carried as a complete unit in one
case. The light sensitive pickup is a photo-electric cell covered
* Westinghouse Lamp Co., Bloomfield, N. J.
357
358 J. L. McCoy tJ. $. M. P. .
with a shield. A window is cut in one side to admit the light to be
measured. The photo-electric cell unit is connected to the meter by
a six foot double conductor cord making it possible to move the cell
unit around within that radius without moving the case. The in-
strument contains a commercial, portable microammeter calibrated
directly in foot-candles. The smallest size "B" batteries are wired
and mounted in the case. As very little energy is required, the .bat-
tery life will be about its shelf life.
The photo-electric cell is generally known as a light-sensitive tube
having somewhat the appearance of a radio tube. The tube has two
distinct parts, an anode and cathode. The cathode is coated, light-
sensitive material giving the tube its characteristics. The resistance
of the cell will vary with the intensity of the light which strikes it.
Many other commercial uses have been found for the photo-cell. It
is used as a smoke detector to sound an alarm in case of fire or to count
the product of quantity production as the cars are counted as they
pass through the Holland Tunnel by the interrupted beam of light.
The cell plays an important role in several different schemes of mo-
tion picture sound reproduction.
There are a number of different types of cells and their character-
istics vary materially with the elements used. They can be made of
different materials to respond to different wave-lengths of light. Dr.
Rentschler of our research department has constructed a photo-electric
cell that will respond only to the ultra-violet region of the spectrum.
This cell is now being used in an ultra-violet recording device, making
it possible to obtain a quantitative reading in ultra-violet units.
The cell used in our light intensity meter is a special cell having a
very broad response, covering the visible spectrum. This response
is such that it will fit in very well for light measurements where the
combination of Mazda light and panchromatic film is used. A spec-
troscopic study of the response of the panchromatic film when plotted
against the light of the Mazda lamp shows that the results are some-
what near a straight line, making it possible for the meter to give an
integration that will come close to the photographic results obtained
with given light values. The use of this meter is suggested to be of
considerable value when colored pictures are taken because of the
integration of the values of different wave-lengths of light through the
visible spectrum. The same cell can also be used for the measure-
ment of north sky daylight, giving approximately the same values for
the same intensity from a photographic standpoint. The photo-cell
March, 1930] A LlGHT INTENSITY M^TER 350
as used is directional in its pickup making it possible to study the
light from different angles. The pickup can be made non-directional
if so desired.
The sensitivity is such that a range of full scale readings can be
made from 100 foot-candles to 3000 foot-candles. We believe the
range of 400 to 500 foot-candles, as read on a full scale of 1000 foot-
candles will fit the studio requirements the best, but this is a matter
to be controlled by the professional studio man.
In order to provide a simple and effective means of calibrating the
meter, without returning it to the factory, we plan to mount a low
voltage lamp in the meter case to check the cell for calibration. At
a definite spacing a calibration check can be easily made. The lamp
will be a six volt type to be supplied with energy from a six volt ex-
ternal battery.
Mr. M. W. Palmer of the Paramount-Famous-Lasky Corp. has
been doing some work with this photometer during the past few
months, to determine the light values on motion picture sets. He has
informed me that while he was checking the light reflected from an
actor's face, the light intensity meter picked up the change in illumina-
tion caused by this man lighting a cigarette. This incident may
illustrate how sensitive this device is to change in light intensity.
We believe this device has an application in connection with film
printing machines. There are a number of different settings of the
printing lamp required to have the film printed without glaring or
too dark results. To control this condition, the different settings
must be made by the operator. In order to try the light intensity
meter for this application, a special mask for the photo-cell has been
made to fit into the aperture of the printer. Mr. La Grande of the
Paramount-Famous-Lasky Corp. has been making tests to deter-
mine the meter's value in this field.
The meter has also been suggested as a means to analyze the light
on a motion picture screen.
As we feel this is a step in the right direction and there is a commer-
cial field for this meter, we should like very much to have the com-
ments of the interested engineers.
DISCUSSION
MR. JONES: I should like to inquire whether the author of the paper has data
available showing the spectral distribution of sensitivity for the cell, also what
he considers to be the certainty with which readings can be made. Is the in-
strument at present commercially available?
360 J. L. McCov
MR. McCov: Data on the spectral response are not available at the present
moment. The instrument is commercially available in certain full scale values.
The meter has an accuracy of probably plus or minus 10 per cent.
MR. JONES: Do I understand that the cell as used gives an indication which
is directly proportional to photographic intensity in the case of the panchromatic
film-Mazda lamp combination and directly proportional to the intensity of north
skylight? Do you propose to publish the data with the paper?
MR. McCov : We have not proposed to do so, but I see no reason why it should
not be published.
MR. JONES: It would add to the value of the paper to have direct data on the
sensitivity.
MR. McCov: This device is very new. We have just gotten it off the
"griddle."
MR. PALMER: (Communicated.) We have found this instrument very useful
around the studio for quick tests. Recently we had submitted to us several
reflectors for which great claims were made as to their efficiency. We took
readings with this photometer and determined their relative value immediately.
We have also used it in checking the relative amount of light in various parts of
a set. We are interested in relative values. We can take a light measurement
with this instrument today and if we have to retake the same scene several weeks
later, we can use the same light value. I believe this instrument is of great
importance to the industry and new uses will be found for it from time to time.
A NEW SYNCHRONIZING APPARATUS FOR 16 MM. FILMS
WITH DISK RECORDS
WM. H. BRISTOL*
In the operation of motion picture projectors, where the film is
synchronized with sound recorded on a disk or on a film, the standard
speed of the projector is 90 feet per minute or 24 frames per second.
It will be understood that the sound record, whether on a disk or
on a film, must be reproduced at the same speed it was originally
recorded, and in order to use the standard theatrical, synchronized
film, whether of original width or whether reduced to 16 mm. width,
it will be necessary to project the pictures at this standard speed of
24 frames per second.
Professional projectors are always operated in booths for fire pro-
tection, which at the same time prevents the audience from being
disturbed by the noise of the machine. All projectors, whether made
for 35 mm. or for 16 mm. films, when operated in the open without
a booth at the standard 24 frames per second, make so much noise
that it is practically impossible to reproduce synchronized sound pic-
tures satisfactorily. Projectors for amateur use are designed pri-
marily to be operated at 16 frames per second. At this speed, it would
usually be impossible to synchronize theatrical records, as they would
only be running at two-thirds of the normal speed at which they were
recorded.
To avoid the difficulties of operating these projectors at the
abnormally high speed that would be necessary to maintain synchro-
nism and give correct reproduction of the sound, we have found, by
experiment, that we can remove every third frame from the syn-
chronized film, thus reducing it to two-thirds of its original number of
frames and when projected at two-thirds the speed at which it was
originally recorded, perfect synchronism will be maintained between
the shortened film and the original sound record. Although by this
plan we have eliminated every third picture, we have found that, due
to persistency of vision, it does not detract from the natural action
of the picture.
* Bristol Studios, Waterbury, Conn.
361
362
WM. H. BRISTOL
[J. S. M. P. B.
By a specially designed printing machine, we are able to make prints
from the original theatrical negatives, either of the standard width or
the 16 mm. width, with every third frame eliminated. Such prints
can then be used in either 35 mm. projectors or 16 mm. projectors at
the reduced speed of 16 frames per second, still producing results
equally as good as though the pictures had been originally taken at
16 frames per second. When projecting these shortened films, it is
FIG. 1. Bell and Howell projector with synchronizing motor attached.
necessary to use a shutter designed for the projection of 16 pictures
per second in order to reduce flicker to a minimum.
The complete outfit for reproducing these special synchronized 16
mm. or any other 16 mm. films, consists of a turntable unit connected
electrically by a small cable of any convenient length to the 16 mm.
projector, using the special synchronizers described in a paper pre-
sented at the meeting of the Society of Motion Picture Engineers,
September, 1928.
We have developed a method of using the same type of synchro-
nizing motors which were previously described, but now made up into
smaller models, especially for non-theatrical, industrial, and educa-
March, 1930]
NEW SYNCHRONIZING APPARATUS
363
tional uses, so that the synchronizers can be used to replace the motors
that are usually employed in 16 mm. projectors. For illustration,
in the 16 mm. Bell & Howell projector, we have been able to substi-
tute for the motor which is usually supplied, one of these synchro-
nizers. Fig. 1 is an illustration of the Bell & Howell projector with
raUSS**' f
i ',
FIG. 2. Turntable mechanism and its support.
this synchronizing motor applied. There is no other change in the
projector, since the gearing at the turntable is made to give the correct
speed ratios. The cord shown is a cable leading to a companion
synchronizing motor, which is shown at the right-hand end on the
base of the turntable (Fig. 2).
The electric motor which is shown on the left-hand side of the base,
364 WM. H. BRISTOL [J. s. M. p. E.
through a worm and gear located in the center of the base, rotates the
turntable by means of a vertical shaft at 33 l /s revolutions per minute.
The motor, in addition to driving the turntable, also turns the rotor
of the synchronizing motor on the base, which generates the current
to drive the synchronizing motor shown as a part of the projector in
Fig. 1.
In order to make the synchronizing motor small enough to replace
the original motor in the Bell & Howell projector, it is necessary that
this motor should run at high speed, but such a high speed is unde-
sirable at the turntable, as it may make noise and cause vibration,
interfering with the perfect reproduction of the sound.
We have always made the synchronizers so that one drives the other
at the same speed as has been previously described, but in this case
the turntable synchronizer is made to drive the projector synchronizer
at twice its own speed. This is accomplished by making a four-pole
synchronizer at the turntable and a two-pole synchronizer for the pro-
jector. The field of the turntable synchronizer is mounted on trun-
nion bearings, so that it may be rotated independently of the rotor
of the turntable synchronizer. The rotation of this field on its trun-
nion bearings in a direction the same as the rotor is turning will cause
a decrease in the speed of the projector, while the rotation of this field
in the opposite direction to that of the rotor will increase the speed of
the projector without in any way affecting the speed of the turntable
or quality of the reproduction. The handle shown in the illustration
(Fig. 2) may be used for revolving the field of the synchronizing motor
in its trunnion bearings through a pair of gears. By means of this, per-
fect synchronism may always be maintained without in any way dis-
turbing the projection of the picture on the screen.
It is of the utmost importance that the turntable be absolutely
free of vibration in order to obtain perfect reproduction, especially of
music. To accomplish this, we have developed a mechanical filter
system which has proven very simple and efficient. The turntable
is mounted on a tripod, which stands on the floor, independent of the
base carrying the motors. A vertical shaft connecting the motor
base with the turntable is provided with several flexible metal disk
joints, designed particularly to filter out the vibration that would
otherwise be transmitted to the turntable from the motor base.
In addition to these flexible disks, there is also a double sliding joint
which is clearly shown in Fig. 2. This double sliding joint, working
in conjunction with the flexible filter disks, has proven to be a most
March, 1930] NEW SYNCHRONIZING APPARATUS 365
practical way of eliminating vibration, which would ordinarily be
transmitted from the motor.
In conclusion, I would like to call your attention to some of the ad-
vantages the author considers are to be gained by the use of these
shortened synchronized films. First, the noise of the projector is
kept down to a satisfactory level without using a sound proof cover,
thus not interfering with the accompanying sound reproduction;
second, the wear and tear is reduced on both the projectors and films
which means longer life for both; third, by using the film of reduced
length, there will be an appreciable saving in the cost of the prints,
handling, storage, and transportation; fourth, this slow speed allows
for increased length of the running time; fifth, the small space occu-
pied by the equipment and the simplicity of its construction makes it
easy to operate and desirable for homes, class-rooms, churches, clubs,
lodges, etc.; sixth, the ease with which the outfit can be packed, trans-
ported, and set up makes it portable and practical for demonstration
and commercial purposes.
DISCUSSION
MR. TAYLOR: When every third frame is cut out isn't there a jiggling move-
ment where something moves uniformly across the screen?
MR. BRISTOL: We have found, as already explained due to persistency of
vision, there is no flickering and the picture appears to be the same on the screen
as if every third frame had not been eliminated.
; | ABSTRACTS ; ; "''
Sound Film Processes. W. STULL. Photo-Era, 63, August, 1929, pp. 70-5.
Wax disk and sound-on-film, both variable area and variable density methods of
sound film processes, are described. Two processes, the Paramount and the
Gaumont-Petersen-Poulsen, record the sound on a separate film and later print
it on the picture positive. Recording practice as well as reproduction are de-
scribed.
Sound Film as Adjunct in Medicine, Law, and Criminal Practice. H. ROOM.
Kinotechnik, 11, Aug. 20, 1929, pp. 430-1. The author stresses the value of
sound pictures in fields outside of the amusement field, such as in medicine, law,
and criminal practice. Actual voice recording of wills, testimony at trials,
property sales, and other uses would make records of greater value and accuracy
than written records.
Interchangeability of Sound Equipment. R. H. CRICKS. Kinemat. Weekly,
151, Sept. 12, 1929, p. 176. Original standards in sound equipment were set by
the Western Electric Co., the sound track being 0.1 inch in width and situated
at the right-hand side of the projector gate; it is separated from its corresponding
picture by 19 frames. There is a possibility that a 56 mm. or even a 63 mm. film
will make its appearance. The existing standard is not claimed to be the best
theoretically, but inventors should bear in mind that it is the most expedient.
The most suitable ratio for disk synchronization would appear to be a record
speed of 80 rpm. with a film speed of 90 ft. per minute, or 18 pictures to the
revolution of the record. The prime essential for disk synchronization is a good
start; this could be effected more easily by widening the first groove to Vis
inch so that the needle could be merely dropped into it, without the necessity for
a minute examination of the disk.
Rational Film. L. GAUMONT. Bull. soc. fran$. phot., 16, March, 1929, pp.
59-61. The author suggests leaving room between the picture and the per-
forations on both sides for two sound records as might be required if right and
left side microphones and reproducers were employed for simulating normal
binaural hearing. Alternating these, two sound tracks could be reserved for
non-synchronized speech in various languages. Also a method of superimposing
the sound and picture records is suggested. The sound record would consist of
variations in ultra-violet or infra-red transmission which would not interfere
with the picture projection and the picture image would not interfere with the
sound reproduction owing to a "special" treatment. The area between the per-
forations and the edge of the film could be used for operating noise effect
machines.
Photographic Problems of the Variable Density Sound Films. R. SCHMIDT.
Filmtechmk, 5, Apr. 27, Aug. 3, 1929, pp. 194-7, 334-6; Sci. Ind. Phot., 9,
August, 1929, pp. 86-8. A theoretical discussion of the photographic relations
of density, transparency, and contrast of negative and positive films and the
conditions for obtaining correct sound rendering with variable density systems.
366
ABSTRACTS 367
Explanation of "Dubbing." Bull. Acad. Mot. Pict. Arts and Sci., No. 26, Oct.
30, 1929, p. 3. A review of a picture given before the Academy on Oct. 23rd by
C. W. Spain. The term "dubbing" was invented in the early years of the phono-
graph and is derived from the word "doubling." Dubbing is resorted to in con-
nection with wax records (1) to even up the volume; (2) to make a new master
record; (3) to eliminate defects in a record; and (4) to give uniform quality to
an uncut negative. Synchronization is also necessary when sound is added to a
previously recorded sound track or when a film record is transferred to a disk
record.
Director Fits German Dialog to Lip Action of American Cast. Ex. Herald
World, 97, Nov. 2, 1929, p. 36. By studying each spoken word of the English
version of the picture Lummox, a German director has so directed a German
speaking cast that their voices are adapted to the lip action of the production.
When expressions could not be made to fit a particular lip movement, the voices
were made to appear to come off the screen, the film portraying only the facial
action of the person addressed.
Sound Film Studios The Problem of Ventilation. A. T. HENLEY. Kinemat.
Weekly, 152, Oct. 3, 1929, p. 61. Essential points in connection with the con-
struction of a talking picture studio foundation system are summarized. For
the ventilation of sound studios refrigeration plants are necessary owing to the
large amount of heat radiated from the lighting units.
Modern Studios at Joinville-le-Pont. G. M. COISSAC. Cineopse, 10, July,
1928, pp. 581-6. The motion picture studio of the Soc. Cineromans-Films de
France, under the direction of Jean Sapene, is described. There are four stages
with a total area of 3275 square meters, two tanks for submarine photography, and
an available current supply of 40,000 amperes. A detailed account of the lighting
and laboratory equipment is included.
Cameraman's Experiences in the Tropics. Filmtechnik, 5, May 11, 1929, pp.
214-5. Cameraman Berliet relates several interesting details of work in the
tropics. During the ocean trip he found the most satisfactory lighting conditions
between Spain and the Canary Islands. In the equatorial belt the contrasts were
excessive and yellow filters were employed. The best time for exposing was
between 7 and 11 A.M. The general results obtained with panchromatic negative
were superior to those on orthochromatic negative material. Temperatures of
104 F. were encountered. The rainy season extended from May to October.
Motion Pictures of the Embryonic Development of the Sea-Urchin. L.
FRANC.OIS-FRANCK AND M. F. VLES. Bull, soc.frang. phot., 16, February, 1929,
pp. 39-41. Motion pictures were made through a microscope of the processes
taking place between fertilization and full development of the larva of the egg of
the sea-urchin. Pictures were made every 4 sec. for a period of 8 hrs. Between
exposures the specimen was protected from the radiation of the illuminator by a
shutter operated electrically from the camera driving mechanism. The camera
and microscope were supported independently.
Motion Picture Study of the Coanoleucocytes and Their Movements. L.
FRANCOIS-FRANCK AND M. FAURE-FREMIET. Bull. soc.fran$. phot., 16, February,
1929, pp. 41-2. Motion photomicrographs were made of white blood cells
in vitro. In one case transmitted light was used in making exposures ; in a second,
reflected light (showing interference patterns) ; and in a third, ultra-microscopic
368 ABSTRACTS [J. S. M. P. E.
technic. The microscope objectives and oculars are mentioned. The taking
speeds varied from 14 to 30 pictures a minute.
Development of Cancer Cells Photographed. Photo-Era, 63, September, 1929,
p. 163. Editorial comment. Photomicrographs were made of growing cancer
cells. By making the exposures at varying intervals from three to sixty seconds
it was discovered that their behavior was very different from that of any other
type of cell.
Motion Pictures of the Interior of the Living Human Bladder. J. J. STUTZIN.
Kinotechnik, 11, July 5, 1929, pp. 350-1. Ten years after the conception of the
idea, Stutzin (Urological Division of the Kaiserin Auguste Victoria Hospital,
Berlin) has succeeded in making motion pictures of the interior of the human
bladder. The exposures were made by the use of the cystoscope attached to the
camera apparatus, and controlled by a lateral view finder to prevent penetration
of the mucous membrane by the lamp end of the cystoscope. An arrange-
ment was also designed which permitted the cystoscope to turn with the camera
apparatus to permit panoramic exposures. To obtain sufficient light was a
difficulty. An illustrative film of this subject was shown at the 78th meeting
of the Deut. kinotech. Gesellsch., June 24, 1929. The author plans to use a
similar set-up to photograph the interior of the stomach, etc.
Lighting Equipment for Photographing Surgical Operations. H. NAUMANN.
Filmtechnik, 5, Jan. 19, 1929, pp. 27-9. The outfit comprises a steel and angle-
iron framework which is supported high above the operating table, on four legs.
Six reflector lamps are mounted at one end of the frame and shine horizontally to
6 respective plane mirrors which are adjustable 1 / cords or levers to throw the
light where it is needed. The camera which exposes at the rate of 24 frames a
second is located in the battery of mirrors. The 6 lamps comprise three of 500
watt capacity and three of 250 watt capacity. The illumination is equal to ap-
proximately 60,000 lux and the lamps are of a type intended for long service
(400-500 hrs.). The lighting has been used successfully to make both ordinary
and color films. The use of panchromatic and hypersensitized panchromatic film
is advocated.
Modern Scientific Uses of Photography. H. J. GRAMARSKI. Filmtechnik, 5,
May 25, 1929, pp. 232-6. A popular article setting forth some of the present
day uses of photography in science. The following are among the uses men-
tioned: (1) photography of electron and atom tracks (work of C. T. R. Wilson);
(2) ultra-microscopic photography (Brownian movement) ; (3) X-ray cinematog-
raphy (work of Gottheiner and Jacobsohn); (4) developments in stereo-cine-
matography; (5) studies of the motion of terrestrial bodies (recent film of Jupiter
and its moons by Prof. Wright).
Motion Picture of Electric Arcs. R. THUN. Kinotechnik, 11, July 20, 1929,
pp. 283-4. This paper deals with the use of motion pictures in an investigation
of conduction in arcs. Photographs of the arc taken through a suitable filter
show the conduction process. Relations between current, voltage, and conduc-
tion process are given in Z. deut. Ing., 73, June 8, 1929, p. 798.
Non-Intermittent Projector. Cintopse, 9, June, 1927, pp. 513-20. The
Continsouza-Combes non-intermittent projector is described in some detail.
Eight similar objectives, mounted on levers and controlled by cams, move in
synchronism with the film so that each objective projects a stationary image of
March, 1930] ABSTRACTS 369
one frame during its entire passage before the gate. No shutter is used, the im-
ages fading one into the other. A rate of projection as low as eight frames per
second gives the illusion of continuity. Photographs and diagrams are included.
New Projectors with Optical Compensation. I. The System of Gummax
Nilsen Vig. H. IVARSON. Kinotechnik, 11, Aug. 20, 1929, pp. 425-6. The
Norwegian, Gummax Nilsen Vig., has constructed a projector with optical com-
pensation similar to the Mechau projector. In Nilsen Vig.'s projector one
oscillating mirror is placed between the objective and the screen, whereby the
curved gate needed for the Mechau and the necessary correction for the curve
through a torus lens is obviated. Another oscillating mirror is placed between
the film gate and the condenser. Thus the number of mirrors has been reduced
from eight to two. The mechanism, which causes the oscillation of the mirrors
and also makes the pictures intermittent, is entirely different from that used in
the Mechau projector.
Askania High Speed Camera. Kinotechnik, 11, Mar. 5, 1929, pp. 124-6;
Lichtbildbuhne, 22, Apr. 13, 1929, pp. 18-9. An ultra rapid camera known as the
"trommelapparat" employs a high frequency 30,000 volt arc for illumination.
The arc current is supplied by a series battery of nine Ley den jars and the light
is intermittently flashed on the subject by means of a rotating sector. The
film (perforated or unperforated) is wound on the inside of a specially constructed
cylinder which accommodates 100 turns of 40 normal frames each. The film is
held in absolute contact in the local plane by centrifugal force. With this type
of camera 4000 normal frames per second are possible. Exposure frequencies of
8000 and 16,000 per second with frames of one-half and one-quarter normal heights
are possible by increasing the intensity and frequency of the light pulses.
Color Film Using Embossed Prisms. P. HATSCHEK. Filmtechnik, 5, Apr. 13,
1929, pp. 154-6. The description of the working principles of a color film system
(U. S. pat. 747,961, Dec. 29, 1903, by Paul Georg and Lena Rosa Frauenf elder) .
(See B. J., Jan. 6, 1911.) The film support is embossed with prisms and the ex-
posure is made from the embossed side. Each prism produces on the film a tiny
spectrum of the light which it receives. After reversal the original colors are
reproduced by projecting the tiny monochrome spectral images through the origi-
nal prisms to the screen. No filters are used in either the camera or projector.
Illumination by Mercury Vapor Lamps. L. P. CLERC. Sci. Ind. Phot., 9,
Sect. A, July, 1929, pp. 75-7. Reflectors dyed with rhodamine and emitting
fluorescent red light proved inadequate and too unstable as a practical means for
supplying the red rays deficient in mercury vapor lamps. A mixture of tungsten
lamps (at normal voltage) and of mercury vapor lamps in the ratio of 1125 watts
of tungsten to 400 watts of mercury, and also in the ratio of 750 watts of tungsten
to 400 watts of mercury, both gave satisfactory rendering on Eastman panchro-
matic film without a filter.
On the Use of Motion Pictures in Schools. // prog, jot., 36, September, 1929,
pp. 303-10. Report of a paper by G. Luzzatto at the motion picture congress in
Padua, June, 1929. The Pathe Baby film is recommended for use in schools on
the ground of its extreme economy. It is stated that with this film a screen of
nearly 60 in. diameter can be filled with sufficient light and that this is ample for
classrooms,
BOOK REVIEWS
Kinematograph Yearbook, 1929. Kinematograph Pub., Ltd., London, 1929,
$1 .50. 536 p. This is the sixteenth yearly issue of this valuable review of progress
in the British cinema trade. The editor's foreword mentions the inroads made
by sound pictures and their effect on the industry; the encouraging improvement
noted in quality of 90 British features produced in 1928; and the continued in-
crease in theater building. The usual summaries of events in the trade are pre-
sented, such as lists of films, producing artists, theater owners, trade organizations,
etc. From a legal standpoint the digest of acts and regulations and the court
actions held should be of value to those interested. The review of the technical
section by A. C. Carter is replete with useful material presented in orderly fashion.
More data, especially on photographic solutions, might have been given in the
section devoted to Data for Kinematograph Technicians.
Yearbook for Photography, Cinematography, and Reproduction Processes
for the Years 1921-27. (Jahrbuch fur Photographic, Kinematographie, und
Reproduktionsverfahren fur die Jahre 1921-27.) J. M. EDER, Editor. W.
Knapp, Halle-an-der-Saale, 1928, vol. 30, $3.25. 1356 p. This number covers
the developments, between 1921 and 1927, in the following fields: Developers; de-
veloping-out papers; intensifiers; reducers; toning bromide and chloride prints ;
fixing; lantern slides; processes for direct positives; reversal processes; printing-
out papers; defects in negative and positive processes; recovering silver, etc.;
finishing photographs; printing from tracings; pigment processes; photographs
on wood, cloth, and other materials; relief photography; photomechanical proc-
esses; etc. Many formulas and directions are given, and there are abundant
references to the original literature. The author and subject indexes for vol. 30
are contained in this number.
Sound Motion Pictures. H. B. FRANKLIN. DouUeday, Doran & Co., Garden
City, L. I., N. Y., 1929, $3.00. 401 p. A well prepared compilation in five chapters
dealing with an historical survey, the theater, the studio, advertising, music,
and the outlook for the future. Some of the technical sections consist of almost
verbatim quotations from technical papers previously published but without
acknowledgment to the authors.
370
SOCIETY OF MOTION PICTURE
ENGINEERS
OFFICERS
President
J. I. CRABTREE, Eastman Kodak Co., Rochester, N. Y.
Past President
L. C. PORTER, Edison Lamp Works, Harrison, N. J.
Vice-Presidents
H. P. GAGE, Corning Glass Works, Corning, N. Y.
K. C. HICKMAN, Eastman Kodak Co., Rochester, N. Y.
Secretary
R. S. BURNAP, Edison Lamp Works, Harrison, N. J.
Treasurer
W. C. HUBBARD, Cooper-Hewitt Electric Co., Hoboken, N. J.
Board of Governors
R. S. BURNAP, Edison Lamp Works, Harrison, N. J.
H. T. COWLING, Eastman Teaching Films, Inc., 343 State St.,
Rochester, N. Y.
J. I. CRABTREE, Research Laboratory, Eastman Kodak Co.,
Rochester, N. Y.
H. P. GAGE, Corning Glass Works, Corning, N. Y.
K. C. HICKMAN, Research Laboratory, Eastman Kodak Co.,
Rochester, N. Y.
W. C. HUBBARD, Cooper-Hewitt Electric Co., Hoboken, N. J.
W. C. KUNZMANN, National Carbon Company, Cleveland, Ohio.
D. MACKENZIE, Bell Telephone Labs., 463 West St., New York,
N. Y.
P. MOLE, Mole- Richardson, Inc., 941 N. Sycamore Ave., Holly-
wood, Calif.
L. C. PORTER, Edison Lamp Works, Harrison, N. J.
S. ROWSON, Ideal Films, Ltd., 76 Wardour St., London, W. 1,
England.
E. I. SPONABUS, Fox-Hearst Corp., 460 West 54th St., New York,
N. Y.
371
372
[J. S. M. P. K.
COMMITTEES
1929-1930
Convention
W. C. KUNZMANN, Chairman
J. W. COFFMAN W. C. HUBBARD M. W. PALMER
M. CRAWFORD
Historical Committee
F. J. WILSTACH, Chairman
C. L. GREGORY T. RAMSAYE
C. F. JENKINS
O. NELSON
R. S. BURNAP
C. BARRELL
J. W. BOYLE
W. H. CARSON
W. CLARK
Journal
L. A. JONES, Chairman
J. W. COFFMAN
H. T. COWLING
W. C. HUBBARD
Membership and Subscription
H. T. COWLING, Chairman
L. W. DAVEE
J. DEFRENES
E. R. GEIB
J. KLENKE
M. L. MISTRY
B. B. NORRISH
I. ROSEMAN
E. C. SCHMITZ
J. L. SPENCE
F. ZUCKER
M. C. BATSEL
F. J. CADENAS
J. A. DUBRAY
O. M. GLUNT
J. A. BALL
J. BOOLSKY
W. CLARK
Papers
J. W. COFFMAN, Chairman
C. R. HANNA G. E. MATHER
K. C. HICKMAN R. F. NICHOLSON
E. HUSE J. B. TAYLOR
D. HYNDMAN
Progress
G. E. MATTHEWS, Chairman
J. B. ENGL A. C. HARDY
R. E. FARNHAM R. C. HUBBARD
H. B. FRANKLIN G. F. RACKETT
A. W. DANESHEW
K. GEYER
S. K. WOLF
H. W. DREYER
G. C. EDWARDS
T. FAULKNER
C. GREENE
Projection
N. M. LAPORTE, Chairman
H. GRIFFIN W. B. RAYTON
R. H. McCuLLOUGH H. B. SANTEE
W. A. McNAiR L. M. TOWNSEND
R. MIEHLING D. F. WHITING
March, 1930]
COMMITTEES
373
F. C. BADGLEY
J. W. COFFMAN
Publicity
W. WHITMORE, Chairman
B. W. DEPUE
G. E. MATTHEWS
G. F. RACKETT
Solicitation
E. P. CURTIS, Chairman
O. A. Ross
E. A. WILLIFORD
M. C. BATSEL
W. H. CARSON
A. DEBRIE
L. DEFOREST
J. A. DUBRAY
E. W. ENG STROM
P. H. EVANS
L. J. BUTTOLPH
F. A. BENFORD
A. C. DOWNES
Standards and Nomenclature
A. C. HARDY, Chairman
R. E. FARNHAM
H. GRIFFIN
R. C. HUBBARD
L. A. JONES
N. M. LAPORTE
W. P. POWERS
G. F. RACKETT
W. B. RAYTON
V. B. SEASE
T. E. SHEA
J. P. SPENCE
E. I. SPONABLE
L. T. TROLAND
Studio Lighting
A. C. DOWNES, Chairman
R. E. FARNHAM
K. C. HICKMAN
M. W. PALMER
Theater Lighting
C. E. EGELER, Chairman
F. FALGE E. HUSE
R. E. FARNHAM L. A. JONES
C. GREENE
LONDON SECTION
SIMON ROWSON, Chairman
A. NEWMAN, Vice-Chairman PAUL KIMBERLEY, Manager
L. EVELEIGH, Secretary ALAN WILLIAMSON, Manager
H. WOOD, Treasurer ' WILLIAM VINTEN, Manager
PACIFIC COAST SECTION
P. MOLE, Chairman
G. F. RACKETT, Sec.-Treas.
C. DUNNING, Manager
E. HuSE, Manager
Membership Committee
J. COURCIER, Chairman
E. JEWELL
Papers and Programs
E. HUSE, Chairman
374 SOCIETY NOTES
RESIGNATIONS
A. C. BROMHBAD HARRY LACHMAN
Gaumont British Picture Corp., Ltd., British International Pictures,
6 Denman St., W. 1., London, Blstree, Herts, England
England
CHANGE OF ADDRESS
JAMES MATTHEWS BERNARD J. KNOWLES
P. O. Box 1629, Manila, P. I. "St. Raphaels" Hillrise, Gerrards
Cross, Bucks, England
GARE SCHWARTZ L. A. CHUBB
9, Deacon Hill, Elstree, RCA Victor Co., Inc.,
Herts, England Camden, N. J.
JOURNAL
OF THE SOCIETY OF
MOTION PICTURE ENGINEERS
LOYD A. JONES, EDITOR pro tern.
Associate Editors
G. L. CHANIER P. MOLE S. E. SHEPPARD
O. M. GLUNT W. B. RAYTON J. L. SPENCE
A. C. HARDY P. E. SABINB I/. T. TROLAND
Volume XIV APRIL, 1930 Number 4
CONTENTS
Page
Dimensional Analysis as an Aid to Miniature Cinematography
G. F. HUTCHINS 377
Flexible Drive Shafts Their Application to Sound Pictures . . J. C. SMACK 384
A Quick Test for Determining the Degree of Exhaustion of Developers ....
MERLE L. DUNDON, G. H. BROWN, AND J. G. CAPSTAFF 389
Elimination of Commutator Ripple from Direct Current Generators ....
O. K. BUCK AND J. C. ALBERT 399
Radiation Characteristics of Two Mercury Arcs FRANK BENFORD 404
A Method of Testing for the Presence of Sodium Thiosulfate in Motion
Picture Films J. I. CRABTREE AND J. F. Ross 419
A New Sixteen Millimeter Motion Picture Camera . . JOSEPH A. DUBRAY 427
The Academy of Motion Picture Arts and Sciences and Its Service as a
Forum for the Industry FRANK WOODS 436
Theater Lighting 441
Report of Projection Committee 444
Abstracts 450
Officers 453
Committees 454
Committee Chairmen 457
New Members 459
Change of Address 459
Society Notes 460
Pacific Coast Section 464
Report of the Secretary 466
Spring Meeting of the Society, Washington, D. C 468
Information for Authors concerning Publication in the JOURNAL 471
Published Monthly by the
SOCIETY OF MOTION PICTURE ENGINEERS
20th & Northampton Sts., Easton, Pa.
Editorial Office: 343 State St., Rochester, N. Y.
Subscription to non-members $12.00 per year, single copies $1.50. Order from
the Secretary of the Society of Motion Picture Engineers, 2 Clearfield Ave.,
Bloomfield, N. J.
Copyright
BY THE SOCIETY OF
MOTION PICTURE ENGINEERS
PERMANENT MAILING ADDRESS OF THE SOCIETY
Engineering Societies Building
29 West 39th Street
New York, N. Y.
Papers or abstracts may be reprinted if credit is given to the Journal of the
Society of Motion Picture Engineers.
The Society is not responsible for statements made by authors.
Application pending for entry as second-class matter at the Post Office at
Easton, Pa.
DIMENSIONAL ANALYSIS AS AN AID TO MINIATURE
CINEMATOGRAPHY
G. F. HUTCHINS*
At the May, 1924, convention of the Society, a paper was pre-
sented by Mr. J. A. Ball on the subject "Theory of Mechanical Minia-
tures in Cinematography." 1 This dealt with the relation of length
and time as seen from the motion picture standpoint. It is the
purpose of this paper to revive this subject with the hope of making
clear some points which may have been vague to many at the time.
Mr. Ball chose four fundamental quantities on which to base his
discussion force, /, mass, m, length, /, and time, t. I prefer, since
these quantities are not mutually independent, to accept only three
as being fundamental, namely, m, /, and /, and to regard force as a
composition of the three. This may simplify the things which
we must keep in mind.
Sir Isaac Newton has stated a series of laws, which, while having
been recently modified by the relativity theory, may be accepted
for our purposes as governing the motion of bodies in our known
universe. These laws may be briefly summarized by the one equa-
tion:
/ = ma,
where a is the acceleration of the body, or its rate of change of veloc-
ity in feet per second per second. It is immediately seen that the
dimensional expression for acceleration is:
We are now able to tie force in, if we choose, with our fundamental
quantities of mass, length, and time, that is,
*
J t*
* General Electric Company.
1 BAI<L, J. A.: "Theory of Mechanical Miniatures in Cinematography," Trans.
Soc. Mot. Pict. Eng., No. 18 (May, 1924), p. 119.
377
378 G. F. HUTCHINS [J. S. M. p. E.
For the purpose of preserving one system of nomenclature, I shall
adopt the notation of the paper mentioned above; small letters will
designate dimensions of the model, small prime letters dimensions in
the imaginary scene or world, and capital letters the ratios of the
former to the latter.
It is a well-known fact that all falling bodies are subjected to the
same nearly constant acceleration on our earth, very slight changes
being observed at different points on the surface. Without realizing
this fact in many cases we are all conscious of it, and any attempt to
show us any other behavior of falling bodies will immediately de-
stroy our illusion as to the "earthly" qualities of the scene which we
are witnessing. The acceleration must, of course, be the same as our
earthly acceleration in order to establish the illusion.
Now with these facts in mind, let us write the expression, in di-
mensional form, for the acceleration with which we are working,
calling this nearly constant acceleration which we experience on the
earth g.
I
= ?
and let us remember that
/ = LI'
m = mm'
t = 7T.
Suppose for example that we wish to show a scene of a large build-
ing toppling. Let us assume that the building which we have in
mind is actually 200 feet in height. Perhaps it is most convenient
to build a miniature of this building ten feet in height. We have now
established the ratio
In order that we may film this miniature action here on the earth
we must content ourselves with the fact that the bricks in the minia-
ture will still fall with an acceleration g, hence,
I
but
April, 1930] DIMENSIONAL ANALYSIS 379
and
/ = LI' and / = TV,
so that
LI' I'
S 5-p i .I'-t
Applying this result to our problem we find that
T = -\/L = \/OXJ5 = 0.224.
This is the relative size of an interval of time in the miniature
system, and is the ratio of projector to camera speed. The reciprocal,
or 4.5, is the speed at which the camera should be run with respect
to the projector.
Now let us study the illusion that we have created. It is important
to note that length and time mutually control one another, that is,
had we run the camera just a trifle slower we would have created the
illusion that the building was only 160 feet tall instead of 200. Had
we run it at 5 times normal, the building would have grown in the
imagination of the audience to a height of 250 feet. The illusion,
then, is made perfect by two facts: first, that the building is made
to represent something with which the audience is familiar here on
earth, and secondly, because the audience is unthinkingly conscious
of the fact that bodies on the earth fall naturally with a very definite
acceleration which is practically constant for all bodies.
Having gone this far without saying very much about the forces
involved, it will be well to attack the forces in our model at this
point. In the case of falling bodies, which we have been considering
up to this point, weight has been the active force. If we may assume
that the densities of the materials in our rnodel are the same as the
densities of the real objects which we are depicting, it is clear that
our mass reduction factor, M, will be equal to L 3 or the volume di-
mension. The force causing a body to fall is then m'g, and will
be mg in the model, or L 3 times as great. In order to be consistent
then, it will be necessary to cause all forces to be reduced in propor-
tion to L 3 . In the case of gravitational force, we are not greatly
concerned with the exact value of mass, for it cancels on both sides
of our equation of motion, and the motion is independent of mass
as first pointed out.
We may now consider some special types of forces. A very inter-
esting illustration is that of resilience forces, such as are produced by
springs, bending beams (with certain limitations), and torsional
380 G. F. HUTCHINS [j. S. M. p. E.
mechanisms. In general this type of force is proportional to a
deflection or deformation, and we may call the constant of propor-
tionality k s ; then in the large scene
/'. = k'sl'
where k' s is measured in pounds per foot displacement. In the
miniature we have
/. = ksl
and since we wish to be consistent with our forces,
/'. k'sl'
so that
K s = L 2 .
This means that in order for our stressed member to behave cor-
rectly when shown on the screen at normal speed, its resilience con-
stant must be reduced in proportion to the square of the length
scale. It should be noted that this treatment applies to any sort
of member where the deformation is proportional to the applied
force and vice versa.
Another very interesting type of force which may be encountered
in miniature work is the damping force, that is, any force which is
proportional to and usually caused by the velocity of a moving body.
Such forces would be very important in such a scene as a falling para-
chute, sinking ship (beneath the waves), or any other case in which
relatively high velocities would be encountered in dense mediums.
This phenomenon is even apparent in the case of our freely falling
bodies, but is so small that we neglect it there.
The resisting force to our motion will be designated by the term,
/'</, and the factor of proportionality, measured in pounds per foot
per second, will be called k' d . Our equations are then
k' d l'
Again the force must conform to other forces in the system, so that
Tt _ K(>L
k'# T
April, 1930] DIMENSIONAL ANALYSIS 381
so that
K d = L*T = Z//2.
It may be expected, then, that a body moving through a dense
medium will be affected in a natural way on the screen only when the
damping constant of the system is reduced in proportion to the
five-halves power of the length reduction factor. It should be
noted, however, that in reducing the length dimension by L, we
have reduced the area of the model by L 2 and hence the liquid itself
need have its damping constant with respect to any moving system
reduced by only Z/ /2 , for the damping constant of any system in
general is proportional to the area of the moving member.
I would like to indicate at this point that the placing of waves in
the same category as falling bodies, as was done in the paper by
Mr. Ball, is not justified. So far as spray and other falling particles
of water are concerned, the parabolic relation of length and time is
probably justified, but in the case of the waves themselves, the
theory of falling bodies no longer holds. In this case the velocity of
the waves is constant, and the length-time relation is a linear one.
I will illustrate by an example. Suppose we have a pool of water
100 feet in length, and suppose we drop a pebble in at one end. It
will take t seconds for the ripples, or waves, to reach the other end.
Now suppose it is desired to make a picture of such an action in
miniature and choose a pool only ten feet long. It will now actually
take one tenth of t seconds for the waves to traverse the pool, so
in order that it appear as though they traversed it in t seconds, it
will be necessary to crank ten times as fast, so that the time ratio is
the same as the length ratio. A failure to realize this fact probably
accounts for some unconvincing ocean scenes which we have seen done
in miniature.
The problem which now presents itself is, how are we to picture
in miniature a ship blowing up in a rough sea. If we scale our time
intervals to accommodate the falling debris, we have not timed
properly for a good illusion in the case of the waves. It may, how-
ever, be shown that the depth of the water used is a factor in the
determination of the velocity of propagation of waves, and since
our model ship is probably floating on a model ocean it is not im-
probable that we may so design the tank as to give the desired effect.
The problem of surface wave motion is not readily adaptable to
simple and direct mathematics, and will not be treated here. This
382 G. F. HUTCHINS [J. S. M. p. E.
subject is ably discussed in detail in Horace Lamb's well-known work
on Hydrodynamics (Cambridge Press).
A very interesting example of the type of problem to be encountered
in cases where stresses in structures accompany motion is to be
had in the cantilever beam. The expression for the end deflection of
a cantilever beam with concentrated load of/ 7 pounds and length s' is
where e' is the modulus of elasticity of the material and i' is the
moment of inertia of the beam with respect to the axis of bending.
Dimensionally this expression may be written:
/ f' 1 ' 3
~ e' i'
and in the miniature
* Ee'Ii'
If the densities are kept constant, F = L 3 and a combination of
equations gives:
El = L 5 .
If we use the same material in our miniature beam that we would use
in the large beam, the modulus of elasticity factor, E, is unity, and
we must reduce our moment of inertia in proportion to L 5 . If we
merely reduce the linear dimensions of the beam by L and keep its
structure the same, its moment of inertia will be reduced by only L 4 ,
so that it will be necessary to change the structure of the beam in the
miniature to secure good results. A properly designed hollow beam
would give the desired effect. The same end might also be obtained
by designing the beam with a reduction in moment of inertia of L 4
(reproduction of the structure in the large beam) and a reduction in
the modulus of elasticity of L. This calls for a beam of different
material, however, and it would therefore be necessary to also see
that the density of the new material was right, and would probably
not be as good a solution of the problem in most cases as the first
alternative.
It may be noted that this problem is merely a special application
of the resilience force case already covered. In our present problem
3ei
April, 1930] DIMENSIONAL ANALYSIS 383
Most of the important cases to be met in designing miniature
sets have now been covered in a general way. It must be remem-
bered, however, that the specific problems present themselves in an
infinite number of combinations, and each one must be solved in a
slightly different way. Fortunately we do not usually have to have
everything perfect, but need concentrate only on those phases of the
structure which lend themselves to enhancing the illusion or spoiling
it, as the case may be. There is no set of equations by the use of
which any one may design convincing models, but one who has a
sound foundation in physics and mathematics combined with a clear
understanding of dimensional relations may use this knowledge to
see at a glance the important considerations of the problem, and
apply his ingenuity to a solution that will give an excellent impression
on the screen.
The difficult conception for the layman to grasp is the idea of a
connection between time magnification and linear magnification, for
he is thinking in terms of optics, and knows that the actual optical
process is geometrically the same in taking pictures at high speed
as when taking them at normal speed. To fully grasp the idea it
must be remembered that the linear magnification which we are
discussing is not an optical one but a psychological one, and is just
as true to physical law in the case of a perfect mind as the optical
magnification which might be accomplished with lenses. The un-
trained mind is easier to satisfy than the trained mind, but the trained
mind, for the same reason, is more appreciative of an illusion suffi-
ciently good to be outside his power of detection. It is pleasing
to know that it is within our power, by using simple physical laws,
to produce illusions which cannot be detected by the hypothetically
perfect mind.
FLEXIBLE DRIVE SHAFTS THEIR APPLICATION TO
SOUND PICTURES
J. C. SMACK*
Before describing the actual applications of flexible drive shafts to
motion picture equipment, it might be well to give you as briefly as
possible a general description of flexible shafts and their charac-
teristics. Although there are over thirty million feet of flexible shaft-
ing used yearly in practically every type of industry in this country,
engineers as a whole are not generally familiar with the technical
characteristics of this product.
Flexible shafts are manufactured in all sizes from 0.041 inch to
0.750 inch in diameter and larger. They are built up of wires usu-
ally in strands of four, wound in superimposed layers. The direction
of the lead or pitch of the successive windings alternates and the
wires are of graduated sizes, increasing with the layers. The ma-
terial itself is a special grade of steel music wire of high tensile strength
and may be wound in any number of layers from two to nine, accord-
ing to the type and size of flexible shaft desired. Shafts of widely
varying characteristics may be produced by different combinations
of wires, by differences in number of layers, and subsequent heat
treatment.
Irrespective of diameter, flexible shafts are regularly made in two
general types, classified as grade "H" and grade "S." The grade
"H" flexible shaft has high torsional strength, or resistance to twisting
strain, and is adaptable to the majority of uses. Grade "S" shafting
has greater flexibility than grade "H" and is usually used where
extreme flexibility is the deciding factor. Various other grades are
also supplied for special applications.
Flexible shafts are wound for maximum efficiency when rotating in
one direction. The pitch direction of the outer layer of wires de-
termines the direction of rotation in which the shaft will give the
best results. A shaft should be rotated so that the tendency is to
* S. S. White Dental Mfg. Co., N. Y. City.
384
DRIVE SHAFTS 385
tighten up the outer layer. A shaft to be operated in a right hand
direction should have its outer layer wound oppositely or left hand.
Therefore, for right hand driving a left hand or left lay shaft should
be used and for left hand driving a right hand or right lay shaft. All
sizes of shafting are manufactured either right or left lay and
although either type can be used in either direction, greater efficiency
is obtained by using the proper lay of winding.
Manufactured in long lengths, flexible shafts are cut to desired
lengths while the wires are under tension. This is accomplished by
brazing or swaging the wires solidly together where the cuts are to
be made. Thus a flexible shaft presents solid ends which may be
soldered or swaged into metal end connections. As this work requires
special equipment and considerable skill, it is advisable that it be
done at the factory of manufacture. Otherwise the structure of the
shaft is sure to be weakened.
The characteristics of torsional stiffness, torsional strength, the safe
working minimum diameter of curvature in which the shaft may be
used, transverse stiffness, internal friction, etc., are very definitely
affected by the construction and method of manufacturing the
shaft. Certain characteristics of a shaft can be modified to advantage
generally at a sacrifice of certain other characteristics. Therefore,
by changing certain factors in the construction or method of manu-
facture, shafts most suitable for a particular set of conditions can be
obtained.
Under these special conditions, the engineer will recognize that it
is a difficult matter to predict in advance the proper shaft to use in
any given installation without an exact knowledge of all the cir-
cumstances under which the shaft will operate. It is therefore
advisable, if a flexible shaft is desired for a particular application,
to consult your flexible shaft manufacturer as to the proper size and
type of shaft to use, supplying him with as full information as pos-
sible. Factors which should be considered are: power to be trans-
mitted, whether continuous or intermittent; speed of rotation of the
flexible shaft; distance between the source of power and object to be
driven; and the radius of the curve or arc about which the shaft
must operate.
Most flexible shaft drives require a casing, both as a protection
against injury and as a guide for them to run in. In some cases
where a short shaft is used no casing is necessary. Casings are
manufactured in all sizes to fit the various sizes of shafting. The
386 J. C. SMACK [j. s. M. p. B.
four principal types of casing generally used are the fabric, the two-
wire metallic, the interlocking metallic, and the rubber covered.
These casings all have special uses and will be taken up later.
For those interested in more detailed information on flexible shaft-
ing the S. S. White Dental Co. about two years ago published the
Handbook on Flexible Shafts. This book has been so widely accepted
and praised by engineers that a more elaborate handbook has been
compiled giving complete engineering data on all sizes of flexible
shafting, and in addition descriptions and photographs of actual
applications in various industries. This handbook will be invaluable
to all designing engineers and will be distributed gratis to those
interested.
CAMERA DRIVES
Let us investigate the characteristics of those shafts most widely
used in the motion picture industry, that is, the y 4 in. and 5 /i 6 in.
diameters. A flexible shaft, to be satisfactory for synchronized
sound motion picture equipment, must be flexible transversely
must be-torsionally as stiff as practical, and still not be too heavy or
cumbersome for general use. To this end the y 4 in. diameter
grade "H" left lay shaft was selected for driving the Bell & Howell-
Western Electric cameras. This shaft has sufficient flexibility to
allow the motor to be placed under the camera, to one side, or in what-
ever position is the most convenient for the operator. The safe
allowable torque on this shaft at 1450 rpm., the speed of the camera
drive shaft, is 13 inch-pounds considerably more than the actual
torque of the camera at any time. Extensive experimentation with
this shaft indicated its altogether satisfactory performance, and it
was adopted by the Western Electric Co. as standard equipment
for their cameras. In the selection of a casing for this application,
the y 2 in. diameter fabric type was used, due to its lightness in weight
and flexibility.
Further experimentation on various types of camera drives indi-
cated that there were cameras which exerted a greater torque on the
flexible shaft than others. Investigation showed that some cameras,
in particular the new sound cameras, were considerably stiffer in
operation than others. Some were so stiff that at times a wobble
or fluctuation was experienced in the camera drive. A larger shaft,
the 6 /ie in. diameter, was substituted for the x /4 in- an d no further
trouble was experienced on these cameras. With this shaft a 8 /s in.
diameter two-wire, black japanned metallic casing is used, or a 5 /g in.
April, 1930] Fl^XIBI^ DRIVE SHAFTS 387
diameter rubber covered casing. For cameras used without a sound-
proof booth, the rubber covered casing is the best as it will deaden
any slight noise caused by the rotation of the flexible shaft. Some-
what the same effect can be obtained with the metallic casing, by
covering it with a light, flexible rubber tubing. It is also advisable
to grease the flexible shaft occasionally with a good grade of light
grease.
Attachment of the flexible shaft assembly to the motor is usually
made with a special ball bearing motor coupling manufactured for
this purpose and designed to fit the standard end fittings furnished
on stock */4 in., 5 /ie in., and 3 /g in. diameter flexible shaft combinations
and their respective casings. These couplings are also supplied in
various sizes to fit standard size motor shafts.
Due to the many types of cameras, there is no standard adapter
made for attaching the flexible shaft drive to the camera. It is,
however, a simple matter to have one made to fit both the camera
drive shaft and the standard end fittings provided on the flexible
shaft and casing. Flexible shaft camera drives are usually used in
lengths from 3 ft. to 6 ft. and in special cases up to 10 ft., the length
being governed of course by the position of the motor.
TURNTABLE DRIVES
Our next problem is the turntable for synchronized sound disk
records. It is customary to connect the turntable direct to the pro-
jecting machine by any one of a number of methods. Those most
widely used are: (1) the direct shaft drive where the turntable is
usually mounted directly on the projection machine; (2) the solid
shaft drive with one or two universal couplings ; (3) the short flexible
solid rubber coupling drive; (4) the flexible shaft drive.
A perfect turntable drive should be all of three things. It should
be vibrationless, provide a positive drive, and allow for flexibility in
installation. Of the four drives listed above, the flexible shaft drive
is the only one which fulfills all three requirements. Vibration is
experienced with solid shafts if they are not properly installed; also
there is no flexibility in installation as the position of the turntable
cannot be changed. Vibration is the main disadvantage of universal
joints and here also we have little opportunity to change the location
of the turntable. The flexible rubber coupling is partially satis-
factory but is subject to deterioration and cannot be used in lengths
over 6 in. However, when we consider the flexible shaft drive we
J. C. SMACK
find a vibrationless and positive drive with extreme flexibility and
ease of installation. In long narrow booths, the turntable can be
placed at the rear of the projection machine or for wider booths on
either side, providing a means by which the space available can be
used in the most economical and convenient way.
As for the camera drives, a x /4 m - diameter grade "H" shaft has
been found to be the most satisfactory shaft although for long drives
it is usually advisable to use the 3 /ie in. diameter shaft. Any of the
three types of casings mentioned can be used with these shafts
and for short lengths under 12 in. the casing can be eliminated. How-
ever, a turntable to be satisfactorily driven by a flexible shaft must
be designed to provide a uniform load for the shaft, sufficient to hold
it at its average angle of torsional deflection. If the turntable
has a tendency to fluctuate, producing a wavering sound reproduction,
a friction brake of some type should be attached to the periphery of
the turntable or to the internal shaft. Only a slight braking force
will be necessary to eliminate this trouble. Also the addition of a
fair size fly wheel or proper gearing will eliminate this fluctuation.
Flexible drive shafts for turntables are now being adopted as
regular equipment by many manufacturers of sound picture equip-
ment.
OTHER FLEXIBLE SHAFT APPLICATIONS
In addition to driving cameras and turntables, the flexible shaft is
also being used for driving optical printers for trick cinematography
as developed by the Lang Film Co., specialists in this type of work.
A 5 /ie in. diameter grade "H" shaft drives this printer in perfect
synchronization, fulfilling in every way the rigid requirements of
this application. On other printers it has sometimes been found
advisable to use a 3 /s in. diameter grade "H" shaft with 3 / 4 in.
diameter casing, due to the larger torque applied to the shaft.
Small diameter flexible shafts are being used on film speed indi-
cators for projecting machines. In most cases this is the 0.130 in.
diameter shaft. Attachment is made with a special coupling to the
shutter shaft and the instrument is mounted in a convenient position
nearby.
For a small home talking motion picture outfit a 3 /ie in. diameter
grade "H" shaft with 0.445 in. diameter interlocked, black japanned
metallic casing is used with great success for driving the turntable in
perfect synchronism direct from any 16 mm. motor driven projector.
A QUICK TEST FOR DETERMINING THE DEGREE OF
EXHAUSTION OF DEVELOPERS*
MERLE L. DUNDON, G. H. BROWN, AND J. G. CAPSTAFF
INTRODUCTION
The fine grain borax developer formula, 1 originated by J. G.
Capstaff and R. A. Purdy, was presented to the trade in the East-
man Duplicating Film booklet issued in January, 1927, 2 and has since
been widely adopted.
The end of the useful life of the borax developer is reached when
its degree of exhaustion is such that it causes an apparent loss of
exposure on the film, although the desired contrast can still be ob-
tained by longer development. 3 With ordinary developers, this
condition does not become serious, and they can be used until the
required time of development becomes too long. The loss of avail-
able image peculiar to exhausted borax developer cannot be de-
tected by examining a developed film of unknown exposure, but if
two pieces of film having identical exposures are developed to the
same gamma in fresh borax and in exhausted borax, the film developed
in the latter will appear to have had less exposure. For this reason,
it is obviously important that borax developer should not be ex-
hausted too far when used for negative film.
In this communication, a quick test is described which gives a
reliable indication of the degree of exhauslion of the developer, and
the application of this test to borax developer is discussed in detail.
* Communication No. 405 from the Kodak Research Laboratories.
1 Elon 2.0 grams
Sodium sulfite (anhydrous) 100 . grams
Hydroquinone 5.0 grams
Borax 2.0 grams
Water to 1.0 liter
2 Eastman Duplicating Film, Eastman Kodak Company, Rochester, N. Y.
(1927).
3 CARLTON, H. C., AND CRABTREE, J. I.: "Some Properties of Fine-Grain De-
velopers for Motion Picture Film," Trans. Soc. Mot. Pict. Eng., XIII (May,
1929), No. 38, p. 406.
389
390 DUNDON, BROWN, AND CAPSTAFF [j. s. M. P. E.
It is believed that under certain conditions such a control test can
be very useful.
CONDITIONS CAUSING LOSS OF EXPOSURE
When a silver bromide solvent is present in low concentration in a
developer of reasonably strong reduction potential, most of the dis-
solved silver bromide is reduced as fast as it is dissolved and the
silver is redeposited very near to its original location on the develop-
ing nuclei already present. When the solvent is too strong or the re-
ducing action too weak, the soluble complex formed with the silver
halide escapes into the developer and is slowly reduced, causing a
sludge of the reduced silver. In this case, some of the available den-
sity for a given exposure is lost,
It is a wdl-known fact that increasing the bromide content of a
developer delays the first stages of development. When an image is
being rapidly formed by development, it is obvious that so much
bromide is released within the film that the influence of ordinary
bromide concentrations in the developer is negligible. Therefore,
the effect of bromide in the developer is limited largely to the first
stages of development.
In the borax developer with a fresh solution containing no bromide,
development starts very quickly. When bromide is introduced
either directly or by developing film, the appearance of the image is
greatly delayed. With 2.0 grams per liter of potassium bromide, 3
or 4 minutes elapse before the shadow detail becomes visible. Mean-
while, the sulfite is exerting its solvent action with the resulting loss
of developable image density. This is in agreement with the known
fact that bromide in a borax developer causes an effective loss of
exposure in film when developed to the customary gamma between
0.6 and 0.8.
To test this idea further, strips of film exposed through a step
tablet were bathed for five minutes at 70F. in a solution of sodium
sulfite containing 100 grams per liter, and then developed for differing
times in a fresh borax developer at the same temperature. Com-
parison strips were soaked in water instead of the sulfite solution and
developed for the same times. When a gamma of approximately
0.7 was obtained in each case, the film bathed in the sulfite solution
showed such a loss of image that it appeared to have an exposure of
only about one-third that of the strip bathed in water.
If the solvent action during the induction period before the de-
April, 1930] EXHAUSTION OF DEVELOPERS 391
velopment starts is responsible for the loss of image density, then,
if development is started in a fresh developer and completed in an
exhausted developer, no shadow detail should be lost. This possi-
bility was tested carefully using a fresh borax developer and a badly
exhausted one. The latter had been used in a large tank for de-
veloping motion picture negative film, and it had been revived after
80 feet per gallon. When the tank was finally discarded after a total
of 160 feet per gallon, a small sample was exhausted further. When
Eastman motion picture panchromatic negative film was developed
for eight minutes in the fresh and ten and one-half minutes in the
revived and exhausted developer a gamma of 0.7 was obtained in
both developers. The film developed in the exhausted developer,
however, appeared to have only half the exposure of that developed
in the fresh developer although actually the strips had been exposed
exactly alike.
Tests were then made by starting strips for differing lengths of time
in the fresh developer and completing development to the same
gamma in the old developer. These tests showed that, if the film
were developed for 2 minutes in the fresh developer followed by l /z
minutes in the old developer, the same gamma of 0.7 could be ob-
tained with no loss in exposure, although both fog and image density
were slightly less than with the fresh developer. With 4 minutes
in the fresh and 4 minutes in the old, the total density also was the
same as with 8 minutes in the fresh. The exact times stated above
applied to the particular developers, and emulsion used in these tests
would vary under different conditions.
In a developing machine where fresh developer is put in con-
tinuously at one end and the exhausted developer is allowed to
overflow at the other, always maintaining constant development
conditions, it is obvious from the above data that the fresh borax
developer should be introduced where the film enters and moved
through the machine in the same direction as the film. This is
opposite to what would be done with most developers as develop-
ment would ordinarily be started in the seasoned portion of the
developer in order to prevent fog.
THE DEVELOPER TEST
The developer test described herein is of a photographic nature
and is based on the well-known principle of the Watkins factor.
Instead of determining time of appearance of an image, however, it
392 DUNDON, BROWN, AND CAPSTAFF [j. s. M. p. E.
has been found much simpler and more accurate to develop a standard
exposure for a definite time, stop development instantly, and com-
pare the image so obtained with a previously prepared standard.
Such a strip can be examined easily by reflected light, either in white
light or with a bright safelight. If the time of development for the
test strip is so selected that the last available exposure step (shadow
detail) just fails to become visible in the fresh developer, then a
very great difference will become evident with any less active de-
veloper. With some developers, this time may be 30 seconds or
less but with borax developer a time of 1 or 2 minutes is best.
Motion picture positive film is advised for the test strips be-
cause it can be handled with less danger of light fog than negative
film. The test can be made directly in the tank or a sample of the
developer can be tested in a graduate or other suitable vessel if
care be taken to see that the temperature is correct.
Technic Advised. A strip of motion picture positive film containing
a standard exposure, preferably a print from a uniform density
step tablet, is used. The strip of film is quickly dipped into the
developer, noting the time accurately to the second. During im-
mersion, it should be agitated gently. Three or four seconds before
the required time is up, the strip should be lifted from the developer
and so held that it can be plunged into the stop bath without delay
when the time is up. In other words, the time of the test is measured
from the moment the strip enters the developer to the moment it
enters the stop bath. The strip should be agitated when first put
into the stop bath. After 10 seconds it can be examined satis-
factorily, but if it is to be made permanent for keeping, it should be
kept in the stop bath for 2 minutes and then washed for about
10 minutes. In handling the strip, it can merely be dipped by hand
with a clip on the lower end for weight, or a special holder can be
devised by attaching clips to a monel wire frame. Contamination
from fingers or dirty clips should, of course, be avoided. The stop
bath can be used most conveniently in a graduate or tube deep enough
to permit the entire strip to be suspended in it.
Composition of the Stop Bath. The formula for the stop bath is as
follows:
Potassium iodide 20 grams
Glacial acetic acid 20 cc.
Potassium alum 40 grams
Sodium sulfite 1 gram
Water to 1 liter
April, 1930] EXHAUSTION OF DEVELOPERS 393
The acetic acid instantly stops the action of the developer and the
iodide converts the undeveloped silver bromide to silver iodide which
is not darkened by light. The alum serves to harden the film and
the sulfite prevents the solution from becoming colored because
of the action of light on the potassium iodide. The bath can be
used repeatedly as long as it remains acid.
Stability of the Test Strips. If the test strips are to be kept as a
record or as a standard for comparison, they must be permanent.
It has been found that motion picture positive film after 2 minutes
in a stop bath is sufficiently iodized so that it is not darkened by
several days' exposure to sunlight. To prevent the image from
fading, the film must be washed thoroughly to remove free iodide and
acid. The acid can also be removed by giving a final rinse in water
containing a few drops of ammonia. Potassium iodide in an acid
medium is readily decomposed by light forming free iodine which
converts the fine silver grains back to silver iodide, causing the
strip to fade. This explains the need for thorough washing.
It should also be noted that test strips should not be used more
than a month after they are printed since the latent image on motion
picture positive film is liable to show some fading in that time.
TYPICAL EXHAUSTION TESTS
In the photographs are shown test strips dipped for 1, 2, and 3
minutes at 65F., 70F., and 75F., in borax developer at different
stages of exhaustion and with different quantities of bromide added
to the unused developer. In Fig. 1 are shown tests made at certain
stages of exhaustion life of a 120 gallon tank of borax developer
used for rack development of panchromatic motion picture film. 4
After 80 feet per gallon had been developed in the tank, the film
showed an apparent exposure about 70 per cent of that obtained
with the fresh developer. This developer was used for a series of
tests marked "before revival." The tank was revived by adding
half the original quantity of developing agents and borax dissolved
in as little water as possible with sufficient sulfite to equal 10 per cent
of the solution added. This revived solution was used for the test
marked "after revival." The tank of developer was then further
exhausted to a total footage of 160 feet per gallon when the apparent
4 The authors are indebted to Dr. H. C. Carlton of these Laboratories for the
history of these developer samples.
394
DUNDON, BROWN, AND CAPSTAFF ]J. S. M. P. B.
exposure on the film was about 60 per cent of that shown by the
fresh developer. At this point, its use for commercial purposes
was discontinued. A sample was further exhausted, however, to a
FIG. 1. Tests at various stages of developer exhaustion.
total of 240 feet per gallon when it showed an exposure only half that
obtained with fresh developer. This was used for the final series
marked "end of useful life." On this chart, looking down each
column from top to bottom, one can observe the changed appearance
April, 1930]
EXHAUSTION OF DEVELOPERS
395
of the test strips as the developer was exhausted for any given tem-
perature and time of testing.
It is obvious from this chart that a one-minute test at 65F. is
2mm. 3min. ttnltv 2rrtvr\
FIG. 2. Tests at various bromide concentrations.
too short to give the desired information. Likewise, 3 minutes at
75F. does not show suitable differences. With 2 minutes at 65F.
and 1 or 2 minutes at 70F., however, there are very striking dif-
ferences in the appearance of the test strips at different stages of
exhaustion.
396
DUNDON, BROWN, AND CAPSTAFF [j. s. M. p. B.
In Fig. 2 is shown a similar series of test strips for a fresh, unused
borax developer to which varying amounts of bromide were added.
The effect of the bromide in delaying the appearance of. the image
is striking. Further, it can be seen that differences in this chart are
quite similar to those obtained by exhaustion, showing that a
FRESH OLP
PE.V. PCV.
PIP TESTS
FSCSH OLP
PCV. PEV.
PRINTS FROM FULLY
PtVELOPEP STRIPS
A. FRE5M PEV. PWNTEP TO GSVE B.EST PICTURE!
B . OUP PE.V. " WSTW A
C. FRESH PEV. " p
P. OLP PEV. " TO OWE &E.ST PICTURE.
FIG. 3. Exposure loss in exhausted borax developer.
large part of the exhaustion effect with borax developer can be
attributed to accumulated bromide.
In Fig. 3 are shown the two-minute dip tests at 65 F. for a fresh
and a badly exhausted developer as described above. Corresponding
to these are prints from two strips both having the same exposure
and each developed to a gamma of 0.7, one in the fresh and one in the
old developer. The strips were printed from a 0.3 density step tablet
and therefore each step had just twice the exposure of the preceding
one. It can be seen that one step on the shadow end is missing from
the strip developed in the exhausted developer since that strip has to
be moved along one step in order to make the densities the same as
in the other strip. In other words, the exhausted developer would
April, 1930] EXHAUSTION OF DEVELOPERS 397
require twice as much exposure as the fresh developer to give a
negative of the same range and density. Picture negatives from the
same strip also were developed to the same gamma in the same two
developers, and prints which are reproduced show the loss in shadow
detail on the film developed in exhausted developer. From this
figure, therefore, it can be seen that the dip test gives a greatly
exaggerated measure of the degree of exhaustion, compared to the
effect on the fully developed film. This makes it a very sensitive
test and when properly interpreted adds to its usefulness.
Advantages of the Dip Test. The dip test when applied to borax
developer as described above measures the delayed appearance of the
image which has been found to correspond with the tendency of the
developer to show a loss of exposure on the film. The test can be
performed in 3 or 4 minutes except for the complete washing required
to make the strip permanent; and for immediate information the
strips can be examined without washing. The differences are so
great as to be very easily noticed and the weaker images have a
brown tone which is also significant. Examination of a fully de-
veloped and fixed film is much more difficult when detecting the
same differences in developers. It seems, therefore, that such a test
should be very useful whenever it is desired to learn quickly the
degree of exhaustion and comparative safety of a used borax developer.
With a little experience, and when using a standard exposure, a
mere glance at the finished test strip is usually sufficient, but for
exactness, comparison should be made with a previously prepared
standard strip.
SUMMARY
It is suggested that the loss of exposure on motion picture negative
film developed in badly exhausted borax developer is caused by the
solvent action of the sulfite while the start of development is being
delayed by the bromide.
A quick photographic test is described by means of which one can
measure the retarded start of development which corresponds to
the loss in exposure obtained with exhausted borax developer.
The same test can be applied to ordinary developers to measure
their degree of exhaustion, provided it is standardized for the given
developer as used.
DISCUSSION
MR. TAYLOR: Your usage of the term "exposure" might in some cases be
open to criticism. To speak of the "loss of exposure" is misleading. Would
not "loss of latent image" be more accurate?
398 DUNDON, BROWN, AND CAPSTAN
DR. DUNDON: It may be that the term "exposure" is not technically correct.
In measuring this effect, we took the speed reading on the H & D curves as is
customary, and when this H & D curve shifted one step on the 0.3 density tab-
let, we said that it showed one-half the exposure or speed. In some discussions
of this matter it has been called a loss of speed. Actually, it is loss of latent
image. If we use the old developer all the latent image does not come up and,
measuring it in the ordinary way, the film has only half the speed that it had
originally.
MR. TAYLOR: Some one else at another time may use "loss of speed." I
noticed also that once or twice you said "apparent loss of exposure" or "effective
loss of exposure," which might be the better term.
DR. DUNDON: Perhaps this nomenclature might be used more uniformly.
However, when the camera man sets his exposure from a test film developed
in a fresh developer and then shoots his picture and has it developed to the same
gamma in an exhausted developer, it is under-exposed. This is due to the
characteristics of the exhausted developer.
ELIMINATION OF COMMUTATOR RIPPLE FROM DIRECT
CURRENT GENERATORS
O. K. BUCK AND J. C. ALBERT*
The large electric utilities of today are interested not only in the
kilowatt hour sales, but also in the most efficient use of that energy
by its consumers. The Department of Water and Power of Los
Angeles endeavors to identify itself with the industries it serves by
cooperation with its consumers to the fullest extent. This depart-
ment has established very low rates for energy and also has assisted
in solving technical problems which arise in the utilization of that
energy.
One of these problems which we have been able to render assis-
tance in solving is undoubtedly of considerable interest to this group.
This is the elimination of the commutator ripple from the direct cur-
rent generator in order that high intensity arcs may be used in the
production of talking pictures.
When the studios first started making talking pictures it was, of
course, necessary to eliminate all outside noises from the sets. In
using the high intensity arc it was found that a high pitched squeal
was emitted therefrom, a pitch near the middle of the audible range
and therefore very objectionable. It was found upon investigation
that this noise was caused by an alternating current wave super-
imposed upon the direct current. This was readily traced to the
generator and determined as a function of commutation. It has
been termed "commutator ripple." The frequency is directly
proportional to the speed of the generator times the number of com-
mutator bars. We therefore have to deal with frequencies ranging
from 900 to 1800 cycles.
Several of the studios have been more or less successful in cutting
the noise down to a minimum. The first method employed was the use
of impedance choke coils, either on the lamp, on the feeder, or, per-
haps, upon the generator itself. The small "whistle boxes" installed
* Dept. of Water and Power, Los Angeles, Calif.
399
400 O. K. BUCK AND J. C. ALBERT [j. s. M. p. E.
at the lamp are most commonly used. They consist of from 50
to 130 Ibs. of copper and iron. They are moved around with the
lamps and thus increase the cost of rigging and striking sets. It then
developed that there were different characteristics of distribution
system or generator design that produced different results at dif-
ferent studios.
One particular lot has a large distribution system of lead covered
cable and a low frequency ripple. For this reason the choke coils
FIG. 1. Alternating current wave of 1800 cycles superimposed upon the
direct current.
on the lamp are very successful. The ripple is not as readily picked
up by the microphone on account of this lower frequency and the
large amount of capacity in the lead covered cable furnishes a by-pass
for the alternating current. The same method on other lots would
not work with the same degree of satisfaction.
The Test and Research Section of the Department of Water and
Power of Los Angeles was then called in and has endeavored to
analyze the problem in a scientific way. An oscillograph record
shows that upon the particular generator studied, there was an
alternating current wave of 1.5 per cent variation superimposed upon
the direct current. Fig. 1 shows this wave. It can be readily seen
April, 1930] ELIMINATION OF COMMUTATOR RlPPLE 401
that this is an even wave form of 1800 cycles frequency. After
considering the practical features of the situation it was decided
that the proper place to damp out the ripple was at the generator.
The two principal reasons were: first, the cost of rigging sets would
be thus reduced; second, the possibility of inductive pickup on micro-
phone cable would be eliminated.
As I have mentioned, the methods employed up to this time had
consisted of the addition of impedance only to the line. The alter-
nating current was thus left to seek its own path across the line or
across the generator. Our plan was to establish a well-defined path
directly across the generator. An harmonic filter of both impedance
and capacity was designed and tuned to absorb a frequency of 1800
cycles. Connected across the line it was effective to a slight extent
but the resistance of the device was altogether too high. When a
load of 5000 amperes is thrown across the line the resistance of the
circuit is extremely low and therefore the ripple would take the path
of least resistance going around through the arcs rather than across
the filter.
Experimentation with paper condensers necessarily limited us to
small amounts of capacity and high resistance. We found that on
account of the much higher capacity provided by means of electro-
lytic condensers the results were much more satisfactory. Even
with these higher capacities it was necessary to use a large impedance
coil to choke back the alternating current and force it through the
condenser by-pass.
We tried several designs of impedance coils. An air core coil would,
of course, be independent of load in its effectiveness but, on account
of the large size and the large amount of copper necessary, it was
impracticable. An iron core coil could be built for the same im-
pedance value and consume much less space. This type of coil was
effective up to the point of saturation of the iron core. On account
of the very heavy direct current loads carried by the studio, a simple
coil with an iron core was necessarily unsatisfactory.
We then tried a coil consisting of two windings upon a common
core, each winding to be on opposite sides of the direct current line
and so connected that the direct current field of one line would
buck that of the other line. This, after several refinements, produced
rather satisfactory results.
The experimentation continued and we then decided by using more
capacity and connecting the condenser to the generator in such a
402 O. K. BUCK AND J. C. ALBERT [j. s. M. p. B.
fashion as to use the generator itself as the impedance that we could
secure the same results. The final outcome was a condenser of 2100
microfarads installed on each side of the generator. Fig. 2 shows
the direct current voltage and current as a straight line; the ripple
has been reduced to the point where it is not rneasurable by. means
of our oscillograph.
Our method in arriving at this solution of the problem has been
one of experimentation, or cut and try plus a certain amount of
FIG. 2. Oscillograph record of current and voltage with filter.
theoretical calculation. I do not believe that there is available
any precedent by which we could govern our work and predetermine
the results that would be secured. We are continuing the experimen-
tation and hope to have available within a very short while ways and
means of calculating the amount of condenser capacity necessary
and method of connection for the various types and makes of gener-
ators. The condenser was built by the use of lightning arrester cones,
of which we had a large supply in our warehouse. These were con-
venient for determining the proper values. The ultimate design of
this electrolytic condenser will undoubtedly be worked out by the
manufacturers. The main characteristics will be large capacity,
low resistance, and compactness.
April, 1930] ELIMINATION OF COMMUTATOR RlPPI,E 403
In conclusion I might mention that the Department of Water and
Power is not interested in promoting the use of either incandescent
or arc lighting. It is our desire to assist the studios in securing the
best results from the consumption of the energy we sell them. If
the producers desire to use arcs for production we feel that the way
has been cleared for them in a satisfactory manner. For the various
types of photography they can now use the various types of lighting
equipment, without fear of microphone interference.
DISCUSSION
MR. PAL,MER: I am very much interested in what Mr. Buck has to say
because we have had the same trouble in our studio in running arcs on d. c.
generators. We get a whistle from them, and I should like to know what the
extra equipment costs for a 500 kw. generator.
MR. BUCK: We have not worked out the design of the filter. We wanted
to take it up with the manufacturers, for we feel it is a manufacturing problem.
We have decided for ourselves, if necessary, we can construct the filters for this
326 KDA generator and install them for less than $500.
MR. STOL,L,ER: I might mention that this problem of filtering the a. c. ripple
out of a d. c. generator is an old telephone problem in connection with the charg-
ing of the central office storage batteries. There is in the Bell System Technical
Journal considerable literature on the subject of choke coils and electrolytic
condensers.
RADIATION CHARACTERISTICS OF TWO MERCURY ARCS
FRANK BENFORD*
INTRODUCTION
The lighting industry from its earliest beginnings to the present
time has been under a peculiar handicap because man's best efforts
in the production of light have always yielded results different from
the light of nature under which mankind has developed. It is no
mere accident that the human eye is most sensitive to those rays of
the sun that are received most abundantly at the earth's surface.
This condition may be looked upon as a natural result of evolution
and, if the facts were otherwise, it would be a matter for profound
speculation. But while the eye has adapted itself to the light of the
sun, there are other natural and artificial factors to be considered.
The beneficial effects of natural light, and of sunlight in particular,
have long been known, but it is only recently that definite data
have been obtained on the so-called therapeutic rays, and these
rays are found to lie entirely outside of the visible spectrum. The
rays that tan the skin and promote the growth of the bones lie at
the extreme boundary of sunlight as received at the surface of the
earth. In this case, our logic of connecting each function of the
body to such a part of the spectrum where it will lie under optimum
conditions is rather weak, and perhaps in abler hands it might be
shown that the presumably older function of the bone growth having
a maximum sensitivity to radiation at 2967 A., as contrasted with the
newer sensation of vision with its peak at 5550 A., indicates that in
previous geologic ages the composition of sunlight was decidedly
stronger in the far ultra-violet regions.
A third factor, and the one in which this Society is particularly
interested, is the region between the therapeutic range and the
visible range, that is, from 3200 A. to 4000 A. Here the ordinary
photographic emulsion is most affected, and therefore to people who
are interested in health, photography, and vision there may be
* Research Laboratory, General Electric Co., Schenectady, N. Y.
404
RADIATION CHARACTERISTICS
405
points of interest in the following data on the radiation of two
mercury arcs that cover the range of radiation over the three regions
mentioned.
It is no part of the purpose of this paper to present these lamps as
cures for any disease. The purpose is to present data showing that
these lamps will help maintain our good health, leaving the cure of
disease where it rightly belongs, in the competent hands of the
physician.
NATURAL LIGHT
It is rather a sad commentary on the state of present day science
1/0
/00
90
80
70
60
SO
3O
^o
JO
3
V/SlBl+E-
/OOO 3000 5000 700O 9OOO //OOO /3OOO S5OOO
O ZOOO 4000 6000 BOOO /OOOO /ZOOO /4OOO
FIG. 1. Sunlight at sea level.
to adniit that we have but little precise knowledge of the composition
of the very sunlight that seems to be the foundation stone upon
which all visible life forms are built. Besides being cheap, and
therefore uninteresting, it is extremely difficult to measure, but
progress is being made and we can hope for much more definite
data in the immediate future. The temperature of the sun is high
enough to furnish generous quantities of energy in the therapeutic
region between 2800 A. and 3200 A. but the earth's atmosphere absorbs
all radiation shorter than 2900 A. and weakens the longer wave-
lengths so that the physical measurement of their strength is a matter
of some difficulty.
406
FRANK BENFORD
[J. S. M. p.
There is only one disease, rickets, for which ultra-violet radiation is
an accepted specific, but there is good evidence that the same radia-
tions that produce sunburn and tan are of material aid in the cure
of several diseases. It has long been accepted that sunlight has great
curvative properties, and the recent development has been the
identification of the rays that are active in certain cases. The pur-
pose of this paper is to give some physical facts about the radiation
characteristics of two mercury lamps, leaving the precise effects
/OO
30
80
70
8*
20
/OO 200 30O
SOO
2OOO
FIG. 2.
7OO 8OO BOO /OO ZOO 3OO
3OOO
Effectiveness of radiation in producing erythema or
reddening of the skin.
and effectiveness of the various wave-lengths to be determined by
the medical profession.
Glass is almost perfectly opaque to the therapeutic rays and hence
sunlight received through a window is non-therapeutic, and the glass
of the ordinary incandescent lamp renders it equally ineffective. As
a result, we who spend a great part of our lives indoors are completely
cut off from a vital factor in our well-being. This is a condition
that has been the subject of considerable thought and discussion on
the part of medical men for years past, but they have been unable
to supply the missing ray, and have been forced to wait for the
physician and lamp engineers to bring artificial light up to the
standard set by nature. Two new units are now available for dupli-
April, 1930] RADIATION CHARACTERISTICS 407
cation of nature's therapeutic effects. One of these is a C. H.
Uviarc Sunlamp with an optical filter for absorbing the far ultra-
violet beyond the therapeutic range.
C. H. UVIARC SUNLAMP
This lamp is a mercury arc in a fused quartz bulb. Quartz is
highly transparent to radiation as short as 1500 A. and moreover
it is capable of operating at temperatures far beyond the limits of
glass. The lamp is therefore useful as a radiant of wide spectral
FIG. 3. Horizontal type burner for Cooper Hewitt Uviarc Sunlamp.
range and high specific intensity, and it is a powerful tool for both
the physicist and the physician.
This type of arc has an operating characteristic that is often
puzzling to an operator not well versed in arcs. If the arc is set
to run at 3.75 amperes and 74 volts, it will be found upon closing the
switch that the current starts at about 9 amperes with a drop across
the lamp of 15 volts. The current drops and the voltage rises until
stability is attained when the lamp has reached its operating tem-
perature. The introduction of lamp temperature as a controlling
factor must be constantly kept in mind if any accurate control of
the radiation is desired. The resistance of the arc depends upon the
pressure of mercury vapor in the lamp, and the pressure depends
upon the temperature of the pool of liquid mercury. Therefore by
attaining control of the temperature of the mercury pool by proper
408
FRANK
[J. S. M. p.
cooling, the electrical and radiating properties are brought under
control.
An analysis of the spectrum of the quartz mercury arc, without
filter, in bands 200 A. wide has been made from 2300 A. to
FIG. 4. Vertical type
burner for Cooper Hew-
itt Uviarc Sunlamp.
7000 A. The energy within this range is radiated in a number of
spectrum lines with region of zero energy between. The lines in
some regions are so numerous as to make their individual measure-
ment a thankless task, and the zone or group method of measurement
is best for the purpose in view. The energy analysis shows a grouping
of energy about 3000 A., the center of the known therapeutic region,
a second grouping about 4000 A., the center of the old photographic
April, 1930]
RADIATION CHARACTERISTICS
409
region, and a third grouping about 5500 A., the center of the visible
region. This coincidence of energy with three regions where man's
interest is concentrated makes the mercury arc one of the most
interesting of lamps.
The lower limit of the therapeutic action is at about 2800 A. and
it is sometimes desirable to eliminate shorter wave-lengths. This is
done by an optical filter, as is illustrated in Fig. 6, for the therapeutic
group of lines, where the filter passes those lines of most value in
2> Pf?ceMTStG. OF TOTfiL /fJft/T
F/fOM .
SHPUT
\o -
sooo
7f.S VOLTS
^7^ WATTS
FIG. 5. Energy in spectrum of C. H. Uviarc burner.
therapeutic effect and eliminates much of the valueless short wave
energy.
In order to attain the maximum intensity in the 2800 A. to 3200 A.
region, the current and voltage must be held within certain limits.
The radiation was found to show a pronounced maximum at 3.75
amperes when the voltage was held at 72.5 volts, and with a fixed
current of 3.75 amperes a practical maximum was found at 72.5
volts. These figures are practically the specified operating figures,
and attempts to force the output by overloading the lamp will
result in a decrease in the output of the desired therapeutic energy.
The depreciation rate of the quartz mercury arc is always slow,
and in this respect it is similar to the low pressure arc in having a
long life with radiation that is not rapidly changed by the blackening
of the tube. Thus tests have shown a 24 per cent depreciation in
410
FRANK BENFORD
[J. S. M. P. E.
the ultra-violet below 3000 A. in 1000 hours, but the total ultra-
violet from 4000 A. down dropped only 15 per cent.
G. E. SUNLAMP
This lamp is of a new and unique type, and the present description
FIG. 6. Uviarc spectrum, with and without Uviarc filter.
is perhaps the first presented to an engineering society. The Re-
search Laboratories of the General Electric Company at Cleveland,
Lynn, and Schenectady have collaborated in the development, and
the writer's connection has been that of analyst as the lamp has
passed through various stages of growth. Essentially the lamp
April, 1930]
RADIATION CHARACTERISTICS
411
consists of a mercury arc operating between tungsten electrodes and
in parallel with a tungsten filament. A small pool of mercury close
IZ
/o
8
/?&
300V TO
zeoo
3ZOOA
70 3OOO
O JO ZO 3O 4O SO 6O 7O SO 9O /OO
LfiMP VOLTS
FIG. 7. Volt-energy characteristic of Uviarc at constant current.
under the filament insures a mercury- vapor saturated arc enclosure
or the forming and maintenance of the arc. The fact that this arc
unctions without moving or auxiliary parts makes it stand apart
If.
/o
8
6
^
2
n
/9T7e.
6 VOLTS
/^
p 3000
rb 3ZOO/
/
ja< ^K
\^\
a a oo ro
30 00 A
o / a 3 4- s
LfiMF* rtMF>f?S
FIG. 8. Current-energy characteristic of Uviarc at constant voltage.
from all other arcs, and challenges the old saying that there is nothing
new under the sun.
The bulb of the lamp is made of one of the glasses that absorb the
energy below 2800 A. and at the same time has a high transparency
412
FRANK BEN FORD
[J. S. M. p. E.
in the visible region. The operating temperature of the glass is
high, but necessarily less than quartz, and therefore the vapor pres-
sure is lower and the brilliancy of the arc is less than in the case
of the quartz lamp.
The starting and operating characteristics of this lamp are dif-
ferent from other lamps that are either plane arcs or plane incan-
descent and not a combination of the two. The lamp is best operated
on a transformer with a magnetically saturated core . Upon closing the
circuit the filament carries the entire current, which rises to between 7
and 10 amperes before the arc forms, which occurs about a second
30
~Job too *oo BOO /ooo
FIG. 9. Typical depreciation curves of Uviarc.
after the current starts to flow. In the case of the particular lamp
of Fig. 10, the maximum current was 7.5 amperes at the moment of
arc formation. The voltage was 18 volts, but this quickly fell to
10.5 volts when the combined arc and incandescent currents mounted
to 30 amperes, which is the normal operating current. In Fig. 11
the solid lines were obtained by reading indicating instruments
as the voltage was slowly changed and hence the record probably
differs in details from an oscillograph of the normal starting charac-
teristic. The dotted lines represent changes that took place too
rapidly for instrument readings, but the real starting characteristic
probably does not greatly differ from curves A, J5, and C.
At 30 amperes total current the division is about 25 amperes arc
and 5 amperes incandescent, the latter being slightly reduced by the
conducted heat from the electrodes raising the temperature and
April, 1930]
RADIATION CHARACTERISTICS
413
resistance of the top coils. If the line voltage is reduced, the lamp
current will gradually fall to 19 amperes at 13 volts, and at about
this point the arc will break and then reform with the ends of the
arc making contact with both the electrodes and the top coils of the
filament. Dotted curve's, E and F, represent the relations existing
FIG. 10.
General Electric Sunlamp,
Type S-l.
when the arc is breaking and reforming. A further reduction of line
voltage will give the stable characteristic, G, but this is not a desirable
condition on account of the arc overheating the coils where it makes
contact. A further reduction of current to below 10 amperes will cause
permanent breaking of the arc and equilibrium will be attained at
some point on the filament curve, A .
414
FRANK BENFORD
[j. s. M. P. B.
/s
/O
\
o 2 4- 6 a /o / /* /6 /e ^o e^ ft e* ^s *o
/f#tPB/fSf
FIG. 11. Volt-ampere characteristic of Type S-l.
From an operating point of view the lamp should be kept above a
certain dangerous minimum current (in this particular lamp, 20
amperes) and below a maximum fixed by the rating of the lamp.
The arc spectrum is similar to the quartz-mercury arc for wave-
lengths greater than 3700 A. but below this limit the radiation is
^000 000
AffGST/fOMS
FIG. 12. Arc radiation from Type S-l.
April, 1930]
RADIATION CHARACTERISTICS
415
weakened by the absorption of the glass, and there is but little
radiation below 3000 A. In Fig. 13 the broken line represents the
distribution of energy in the spectrum, both arc and filament being
included. The solid line marked "I" is the filament and electrode
radiation, and the height between the solid line and the broken line
is the arc radiation. A comparison of the regions about 3000 A.
in Figs. 5 and 13 will show the effects of the glass. Later a compari-
son will be made to point out how this weakened spectrum compares
with the sun in ultra-violet.
The growth of arc radiation with current is seen by Fig. 14 to be
JO WP 10.9 I 'OLT3 316
TYF> S'/
TST
OF fit. 1. /? f)O/f) T/Ofi/ /N ff
/V CM 1
R *
FIG. 13. Complete radiation from Type S-l.
slight in amount. It has been found that mercury arcs in general
are apt to have both currents and voltages that give maximum
outputs, and the relative uniformity of arc output is therefore in line
with previous lamps. The incandescent output is shown in Fig. 14
to be nearly constant between 24 and 27 amperes and to rise rapidly
at 30 amperes. This rather unique characteristic for tungsten is
caused by the dual nature of the lamp. The negative resistance
characteristic of the arc lowers the voltage across the filament as the
current increases from 24 to 27 amperes, and the light from the
filament decreases. At the same time the electrodes become more
luminous, giving a small net increase of tungsten light. From 27 to 30
416
FRANK BENFORD
[J. S. M. p. E.
amperes the arc drop changes by a smaller amount and the filament
current is not changed by as large a percentage as before. The
electrodes radiate greatly increased quantities of energy and the
net gain in incandescent light is now much greater.
Perhaps a better picture of the relations between input and radia-
tion is gained by examining the watt-lumen characteristics. In
ouuu
7OOO
60OO
5OOO
4OOO
300O
WOO
7Z
I
1
/A/
CftA/OES*
0^
** (
2-*_
/O
20
30
FIG. 14. Ampere-lumen characteristic of Type S-l.
Fig. 15 the arc output of visible radiation is seen to approach a
maximum between 300 and 350 watts, while the tungsten radiation
increases in more nearly the customary manner of an incandescent
lamp. The arc has its maximum efficiency at slightly over 300 watts
while the tungsten efficiency increases steadily with the current.
The presence of well-marked engineering optima will appeal to the
engineer and they seem a guide to good engineering practice.
In Table I a summary is made of some of the therapeutic and lumi-
nous properties of the sun and two therapeutics arcs. It will be
April, 1930]
RADIATION CHARACTERISTICS
417
seen that in the production of light we have a long way to go before
we can hope to rival the sun, but in the production of therapeutic
radiation we have taken a long lead over nature. An extended series
of tests are being conducted on the production of erythema by
these and other lights. So far the results conform fairly well to the
purely physical relations here given, and if proper allowance be
Z./G/1T
7000
6000
5000
40OO
3000
^000
/OOO
O
/
/
7
/
*/
A,^
j
40
30
/o
o /oo zoo 300 +00
LAMP w/trrs
FIG. 15. Watt-lumen characteristic of Type S-l.
made for the finer details of relationship between these radiants and
the erythema curve the computed and experimental degrees of ery-
thema are in excellent agreement.
For equal illuminations the C. H. Uviarc Sunlamp with filter is
300 times as strong in the therapeutic region as the sun, while the
G. E. Sunlamp is 65 times as strong.
The illumination in mid-summer is often 10,000 foot-candles in
direct sunlight, and with present lighting equipment this illumination
by artificial means would be unbearable. But the vastly increased
418
FRANK BENFORD
TABLE I
Some Properties of the Sun and the Two Arcs
Hnergy Analysis in Percentages
Source
Sea Level Sun
Cooper Hewitt Uviarc Sunlamp
G. E. Sunlamp
0-2800 A.
0.00
0.00
0.00
2800-3200 A.
0.05
1.60
0.80
3200-4000 A.
3.75
2.90
1.40
4000-7000 A.
45.00
5.60
9.40
7000-inf.
51.20
89.90
88.40
ratio of therapeutic rays in these mercury arcsi makes it possible to
give sunlight therapeutic values at comfortable illumination, and the
benefits of sunlight are now obtainable for use in the home.
A METHOD OF TESTING FOR THE PRESENCE OF SODIUM
THIOSULFATE IN MOTION PICTURE FILMS*
J. I. CRABTREE AND J. F. ROSS
It is necessary that photographic films be thoroughly washed
after fixing; otherwise, if any appreciable quantity of sodium thio-
sulfate or other sulfur-containing compounds remain in the film,
sooner or later they react with the silver image to form silver sulfide
with the result that the image becomes brown, and it is said to have
faded.
Three common methods are used to detect the presence of sodium
thiosulfate in photographic materials and roughly determine the
thoroughness of washing:
(1) When the film is thought to be washed, it is lifted from the
washing tray or tank and the surface water allowed to drain into 10
or 20 cc. of the following alkaline potassium permanganate solution:
Metric Avoirdupois
Potassium permanganate . 5 gram 7 . 5 grains
Sodium hydroxide (caustic soda) 1.0 gram 15.0 grains
Water (distilled) to make 1.0 liter 32 .0 ounces
For use take stock solution 1 part, water 20 parts. If a small percentage of
hypo is present, the violet color will turn orange in about 30 seconds, and with
larger concentrations of hypo the orange color will change to yellow.
Oxidizable organic matter, if present in the water, reacts with the
permanganate solution and changes the color in the same manner as
hypo. The water should, therefore, be tested as follows:
Add a quantity of water equal in volume to that of the wash
water drained from the film to a second test solution prepared as
above from pure water. If the sample to which tap water has been
added remains a violet color, this indicates the absence of organic
matter and it will be unnecessary to repeat the test. If the color is
changed slightly by the tap water, the presence of hypo in the film
will be shown by the relative color change of the two samples. For
* Communication No. 412 from the Kodak Research Laboratories.
419
420 J. I. CRABTREE AND J. F. Ross [j. S. M. p. E.
example, if the tap water sample turned orange, and the wash water
sample became yellow, it would indicate the presence of hypo; but
if both samples remained the same shade, this would indicate the
absence of hypo.
This method is subject to error inasmuch as the quantity of hypo
in the water drained from the film constitutes only a small propor-
tion of the quantity absorbed by the film, so that a negative result
with the above permanganate test does not necessarily indicate the
absence of hypo.
(2) A drop of a dilute potassium permanganate solution (0.5 gram
per liter) is placed on the dry film. Any rapid change in the color
from brown to yellow indicates an unsafe degree of washing, but since
permanganate is likewise reduced by silver and gelatin, a slow dis-
coloration occurs even in the absence of hypo. By carefully com-
paring the rates of discoloration of the permanganate, however,
a satisfactory estimate of the relative quantities of hypo present
can be made.
(3) Strips of the film being tested are soaked for several hours in
a small volume of distilled water. A few drops of starch solution
are added to this solution and then a drop of dilute iodine solution
(1 gram of solid iodine dissolved in 20 cc. of water containing 2 grams
of potassium iodide, and after the iodine is dissolved the solution is
diluted to 100 cc.). If the solution turns blue immediately because
of the formation of a starch iodide complex, the material is free from
residual sodium thiosulfate. If, however, several drops of the iodine
solution are required to produce a permanent blue coloration, the
material is poorly washed. By using a standard iodine solution it is
possible to determine quantitatively the sodium thiosulfate per
unit area of film.
(4) The new method of determining the thiosulfate content
of films consists in placing strips of these materials in a solution
of mercuric chloride, preferably one which also contains potassium
bromide, and observing any turbidity which may develop in the
solution. If sodium thiosulfate is present, it reacts with the mer-
curic chloride to form mercurous chloride which is relatively
insoluble and causes a turbidity to appear in the solution; while in
the presence of potassium bromide, the precipitate consists of mer-
curous bromide. If no sodium thiosulfate or other reducing agent
is present, the solution remains clear although the silver image is
bleached white. This method is also subject to error inasmuch as it
April, 1930] TESTING FOR SODIUM TniOSULFATE 421
indicates the presence of any reducing agent whether it be sodium
thiosulfate or not, but this error is also common to the three above-
mentioned methods.
The use of mercuric chloride, however, has several distinct ad-
vantages as follows: (1) Only a relatively small quantity of the
film or print is required for testing; (2) the test can be made very
quickly; (3) it probably indicates the presence of a reducing agent
more satisfactorily than the other methods inasmuch as mercuric
chloride causes the silver image to be bleached and thus liberates
any adsorbed insoluble thiosulfate compounds which might be asso-
ciated with the silver; and (4) it is extremely delicate and capable
of detecting the presence of 0.05 milligram of sodium thiosulfate
(crystals) .
The Test Solution. Although a plain solution of mercuric chloride
gave good results, the following formula containing potassium bro-
mide was more sensitive:
Metric . Avoirdupois
Mercuric chloride 25 grams 365 grains
Potassium bromide 25 grams 365 grains
Water to make 1 liter 32 ounces
Method of Testing. Two methods of .testing the thoroughness of
washing of photographic materials are possible, as follows:
(a) By determination of the absolute quantity of hypo in the
film.
Data on the hypo content of photographic films are of little value
unless they are accompanied by data giving the quantity of
hypo necessary to cause fading or otherwise impair the image.
Such data are outlined below.
The absolute hypo content of the film may be determined as follows:
Place 10 cc. of the mercuric chloride solutions in each of a series of
small, glass cylinders. Place a single frame of motion picture film
cut into small pieces in one of the cylinders, and then add increasing
quantities of a 1:1000 solution of hypo to each of the remaining
cylinders containing the test solution. Allow them to stand for
15 minutes, stirring the film occasionally with a glass rod, and
compare the opalescence of the solutions. The quantity of hypo in
the cylinder whose opalescence corresponds with that containing
the film is equal to the quantity of hypo in the film strip.
(b) By comparison of the test film with films which have been
washed for known safe periods.
422 J. I. CRABTREE AND J. F. Ross [J. S. M. P. E.
The actual quantity of sodium thiosulfate contained in a photo-
graphic film or paper is of less practical interest than the relative
degree of thoroughness of washing of the material. Common prac-
tice has more or less established washing times for various materials
which are known to give stable images upon keeping as indicated
below, so that by comparing the hypo content of the test film with
that of films washed for increasing times, a measure of the thorough-
ness of washing is obtained.
The test is conducted as outlined above, namely, 10 cc. of the
test solution are placed in a small glass cylinder and a single frame
of the motion picture film is placed in the solution, taking care to
use a glass rod or other non-metallic material to push the film under
the solution. Standard films which have been washed under known
conditions for 10, 20, 30, 45, and 60 minutes are used for compari-
son. Allow the solutions to stand for 15 minutes and compare the
degree of opalescence by looking down the tube from the top.
The mercuric chloride test has been used to determine the relative
washing times, in comparison with standards, of motion picture
negative and positive films and the test was found satisfactory in all
cases.
The quantity of material and the volume of solution used in making
the test can be varied depending upon the quantity of material
available for the test. One frame of standard motion picture nega-
tive film in 10 cc. of solution was found sufficient for a satisfactory
test, while at least twice this area of film was required for the positive
film test because the emulsion thickness of positive film is less than
that of negative.
THE FADING OF SILVER IMAGES
In the presence of extremely small quantities of hypo or other sul-
fur-containing compounds, the rate at which the silver image is con-
verted to silver sulfide is extremely slow at normal temperatures
so that it was necessary to devise an accelerated test in order to
hasten the rate of fading. The most satisfactory test consisted in
suspending the test samples of film in a glass fruit jar, containing
carbon dioxide gas, over a small quantity of water (Fig. 1) and stor-
ing at a temperature of 110F. The strips of film to be tested were
first arranged around the edge of the jar, an excess of carbon dioxide
gas passed into the jar from a gas cylinder, and the jar then rapidly
sealed. Careful tests indicated that the carbon dioxide did not at-
tack the image but merely accelerated the fading reaction.
April, 1930]
TESTING FOR SODIUM
423
From an exhaustive series of tests it has been found that the rate
of fading of a silver image in air free from sulfur compounds depends
upon the following factors:
(a) The size of the grains which comprise the image.
(b) The temperature and humidity of the air during storage.
(c) The quantity of hypo or other sulfur-containing compounds retained in
the image.
(d) The relative acidity or alkalinity of the gelatin film Containing the image.
FIG. 1.
Illustration of method of con-
ducting fading tests.
The size of the image grains is, perhaps, the most important factor
involved. With images such as exist on motion picture film, it is
somewhat difficult to produce fading even in the presence of appre-
ciable quantities of hypo, whereas with extremely fine-grained images
fading may take place in a few hours' time under the above test
conditions, even in the presence of relatively small quantities of
hypo. A maximum degree of immunity to fading exists, therefore,
with well-washed images which are stored in a dry atmosphere at a
temperature which does not exceed 70F. to 75F.
424 J. I. CRABTREE AND J. F. Ross [j. S. M. p. E.
THE TIME OF WASHING REQUIRED TO INSURE STABILITY
The washing time required in order to insure stability of motion
picture film images depends, of course, upon the method of washing
and particularly the rate of removal of the water at the surface of the
film. 1 In the present experiments samples of motion picture film were
washed in flat trays with an excess of running water at 60F. After
washing for increasing times, the samples were then subjected to the
carbon dioxide fading test described above.
Table I indicates the critical times of washing required before no
fading was obtained on storing for one week at a temperature of
110F. in an atmosphere of carbon dioxide.
TABLE I
Critical Washing Time
Nature of Material
Time of Washing Required to Give Negative
Result in Fading Test
Eastman Motion Picture Panchromatic
Negative Film (Type 2)
Eastman Motion Picture Positive
Film
2 Minutes
5 Minutes
The fact that motion picture negative film washed for 2 minutes
did not fade in the above test does not mean that this time of washing
is sufficient for practical purposes, because the relationship between
the time to produce equal degrees of fading under normal storage
conditions and conditions existing with the accelerated test is not
known. It is desirable in all cases to eliminate the hypo entirely
and Table II indicates that it is necessary to wash negative film for
30 minutes in order to do this.
The above result, however, is significant in showing that the image
on motion picture negative film is very resistant to fading, and in the
experience of the authors very few cases of the fading of negative
images which could be attributed to imperfect washing have been
encountered during a period of 15 years.
In view of the fact that the image on motion picture positive film
is composed of finer grains than a negative film image, it is more
susceptible to the presence of traces of residual hypo. By washing
for five minutes, the image is practically immune from fading but a
1 HICKMAN, K. C. D.: "Washing Motion Picture Film," Trans. Soc. Mot.
Pict. Eng., No. 23 (1925), p. 62.
April, 1930]
TESTING FOR SODIUM THIOSUL.FATE
425
washing time of 20 minutes is required under ideal washing con-
ditions to eliminate the hypo thoroughly.
THE HYPO CONTENT OF WELL-WASHED IMAGES
The hypo content of various materials washed for increasing times
under the following conditions are given in Table II. Strips four
inches long of the developed and thoroughly fixed films were placed
in shallow trays 4 by 6 cm. and a stream of water allowed to flow
into the trays at the rate of one gallon per minute, the water be-
ing completely emptied from each tray at two minute intervals.
TABLE II
Time for Elimination of Hypo
Material
Time of Washing
Hypo Content
Eastman Motion Picture Panchro-
2 Minutes
12 Mg. per foot
matic Negative (Type 2)
5 Minutes
8 Mg. per foot
10 Minutes
4 Mg. per foot
20 Minutes
1 Mg. per foot
30 Minutes
No test
Eastman Motion Picture Positive
2 Minutes
8 Mg. per foot
Film
5 Minutes
2 Mg. per foot
10 Minutes
*/2 Mg. per foot
20 Minutes
No test
A number of strips of motion picture negative film secured at
random from a number of Hollywood laboratories showed a maximum
content of 1 mg. of hypo per foot. A test of a number of strips
of positive films from different laboratories indicated the almost
complete absence of hypo. These tests would indicate, therefore,
that present day laboratories are washing their films satisfactorily.
Practical Recommendations. The times of washing required to
insure the stability of motion picture film as indicated above are given
merely as an indication of what is required under ideal conditions.
In practice, the conditions of washing vary so greatly that it is
absolutely impossible to recommend specific washing times, which
is the reason for determining the hypo content of films or prints
washed for increasing times under any given conditions, and selecting
the time which will give the necessary stability.
SUMMARY
A method of testing for the presence of sodium thiosulf ate in motion
picture film has been worked out which consists of placing strips of
426 J. I. CRABTREE AND J. F. Ross
the processed films in a mercuric chloride-potassium bromide solu-
tion. If the film contains an appreciable quantity of sodium thio-
sulfate, the solution becomes opalescent, the turbidity being roughly
proportional to the quantity of hypo present. It is possible to
detect the presence of 0.05 milligram of sodium thiosulfate (crystals)
in motion picture film by this test.
Some of the factors which determine the rate of fading of silver
images have been outlined, and the critical hypo content and degree
of washing necessary with negative and positive motion picture
film to insure stability have been indicated.
Under ideal conditions it is necessary to wash thoroughly fixed
motion picture negative film for 30 minutes and motion picture
positive film for 20 minutes in order to eliminate the hypo. Under
practical conditions the times are greater according as the conditions
differ from the ideal.
The authors wish to express their appreciation to Mr. I/. B. Mueh-
ler for assistance in the experimental work.
DISCUSSION
DR. HICKMAN: The way in which hypo diffuses out of the film and washes
away has been guessed at for a number of years but has been understood well
only lately. After two or three minutes, the whole of the hypo that can come
away from the gelatin has done so, but there is left in the film a quantity of
hypo which comes out more slowly because it is probably stuck on to the silver
grain itself. I should like to ask whether any of the tests have been made by
differentiating between blank film and that having a fairly heavy deposit.
MR. CRABTREE: No, we have not made such tests. "We took samples at
random from commercial productions. It would be well to repeat the tests
with images of low and high density and I think that such information will be
very valuable.
MR. RICHARDSON: We now have samples of motion picture film that are at
least twenty years old which show no appreciable fading effect. Would that
not indicate that the hypo had been removed?
MR. CRABTREE: It indicates that the films were very well washed when
processed.
A NEW SIXTEEN MILLIMETER MOTION PICTURE
CAMERA
JOSEPH A. DUBRAY*
The Bell & Howell Company has recently brought out a new
model 16 mm. camera, which is known as the Filmo Model 70-D.
It presents such a departure from the Design 70 models, that it is not
expected to supplant them but is considered as an entirely new mem-
ber of the Filmo family.
Some of the engineering developments achieved in this apparatus
will be described.
It is well known that the Filmo camera is of the spring motor
type, that it has a total capacity of 100 feet of 16 mm. film, and that
each complete winding of the spring motor permits, if desired, an
uninterrupted run of 25 feet of film.
The camera, as shown in Fig. 1, is equipped with a turret, T,
capable of holding three photographic objectives and also with a
spring motor winding key, W, of new design.
It is also equipped with three dials, one shown at F indicates the
footage run through the camera, the second at 5 serves to set a
governor to run the camera at any desired speed from 8 to 64 pictures
per second, and the third at E serves as a guide and instructor in
regard to exposures in relation to the speed at which the camera is
operated.
The camera turret can be revolved in either direction to bring
the desired lens into its proper photographic position.
The lens seats shown at L are ground during the assembly of the
apparatus, insuring the standard 0.690 in. distance from the lens
seat to the film plane.
An audible click, caused by the spring-controlled roller, A, falling
into a notch provided in the camera frame, assures the operator
that the lens is properly set and the camera ready for operation.
This position is also controlled by two supplementary rollers and
* Bell & Howell Company, Chicago, 111.
427
428
JOSEPH A. DUBRAY
[J. S. M. P. E.
spring assemblies, equally spaced, as shown in Fig. 2, which insure
stability and perfection of registration.
When the turret is so set that the rollers, A, fall into the locking
notches, a plunger controlled by the supplementary notches, N, is
forced into a groove of the operating button and positive locking is
insured. The locking device is so designed that the operating button
cannot be released unless one of the three lenses is in its exact photo-
graphing position. Index marks and captions are conveniently
engraved on the camera frame to assist the operator in the setting of
FIG. 1. The Filmo Model 70-D camera.
the turret. The camera door, which gives access to the loading
chamber, is located at the opposite side of the winding key and control
dials.
As shown in Fig. 3, the door, D, fits into the frame of the camera
so as to make it light-proof. It is securely fastened to it by means
of two simultaneously operating cams, controlled by the latches, L,
which serve also as indicators for the "Open" and "Closed" markings
engraved on the camera door.
The viewfinder, F, is an integral part of the camera door, and has
been especially designed for its rapid setting at an aperture inclosing
the field of view covered by any of six lenses of different focal length.
These openings have been calculated for lenses of focal lengths
of 20 mm., 1 in., 2 in., 3 in., 4 in., and 6 in., which quite completely
April, 1930]
NEW SIXTEEN MILLIMETER CAMERA
429
A- INDEX ROLLER
ASSEMBLIES
B-LOCK & RUN
INDEX NOTCHES
N- RELEASE BUT-
TON LOCK
NOTCHES
L- LENS SEAT
R- OPERATING
BUTTON
FIG. 2. The multiple-lens turret of the Filmo 70-D
camera.
cover the range of focal lengths most generally used by the amateur
cinematogr apher .
Fig. 4 shows a sectional drawing of the viewfinder. As seen in the
figure, the image formed by the objective, L, and viewed as an
erect image of the subject through the eye-piece, E, is limited in its
area by the opening, 0, which is set the nearest to the objective.
FIG. 3.
View of the door and finder side of the Filmo
70-D camera.
430
JOSEPH A. DUBRAY
[J. S. M. p. E.
A revolving drum controlled by an outside dial is pierced with six
apertures rectangular in shape and of convenient size. The diameter
of the drum and the position of these apertures have been so calcu-
FIG. 4. Viewfinder of the Filmo 70-D camera.
lated that no one of the openings interferes with the one cut in the
position diametrically opposite to it. The path of the light rays,
as traced in the figure, clearly demonstrates this characteristic. The
D
FIG. 5.
Mechanism and spring motor assembly of the
Filmo 70-D camera.
diagram has been drawn so as to show the aperture corresponding to
a 20 mm. lens in the proper position to permit the viewer to examine
the whole field of view of a lens of such focal length.
April, 1930]
NEW SIXTEEN MIUJMETER CAMERA
431
The aperture corresponding to a 1 in. lens, which is cut into the
drum in a position diametrically opposite to the first, does not, as
shown in the picture, intercept any of the rays of light which are
limited by the larger aperture.
It is quite obvious that by reversing the position of these two
apertures so that the 1 in. aperture is in the correct viewing position,
the greater 20 mm. aperture could not possibly interfere with its
G
B
C
FIG. 6. The mechanism of the Filmo 70-D camera with
driving spring and middle plate removed.
field of view. The same condition is fulfilled for all of the remaining
four apertures.
The objective lens can be easily replaced with one of lesser power,
thereby permitting the use of photographic lenses of other focal
lengths. The change of the objective lens would demand the use
of a different eye-piece than the standard with which the finder is
equipped.
If we remove the camera mechanism from its casing, we will be
in a position to see what we would call the "heart" of the apparatus,
which is shown in Fig. 5.
At A, are shown the shutter and cam driving gear; at B, the film
back plate, which is of hardened and highly polished stainless steel;
at C, two of the four film guard spindles; at E, the main driving
spring and hub, which we may mention in passing is kept free from
432
JOSEPH A. DUBRAY
[J. S. M. p. E.
grease or oil and is lubricated by dry graphite; at D, the graphite
retaining plate; at F, the two footage dial operating levers; and
finally, at G, the front motor plate assembly.
If we further remove the driving spring and the middle plate,
we will make it possible to see the mechanism proper, as shown in
Fig. 6.
At G, is shown what we would call the back-bone of the camera,
the front motor plate assembly; at A, the shutter and cam driving
gear; at B, the spring-hub and main driving gear; at C, the take-up
8'
FIG. 7. Head assembly of the Filmo 70-D camera.
spindle gear; at D, the governor assembly and driving mechanism,
of which we will say a few words later; at E, the speed-control lever;
and at F, the footage dial operating levers.
We shall pass next to the head of the camera, which is illustrated
in Fig. 7.
Just as the front motor plate can be called the "back-bone" of
the camera, no more appropriate name could have been found for
this part of the apparatus than the "head," because it encloses the
mechanical brains of the whole instrument.
At A, we see the shutter of the camera as being an integral part of
the cam assembly, which imparts to the film shuttle, B, the com-
posite motion permitting the film feeding fingers, B', to lead the
April, 1930]
NEW SIXTEEN MILLIMETER CAMERA
433
film, after each exposure, in its proper position in front of the aper-
ture. The maximum possible angular opening of the shutter is
216, which represents an exposure of 1 /2eth of a second for each
picture frame. The aperture plate, C, is of hardened, highly polished,
stainless steel, and is easily accessible for cleaning purposes. The
film tension is of the side-tension Bell & Howell type, controlled
by a stationary film-guide rail, D, and a spring controlled film side-
tension rail, E. This all-important feature of the camera distributes
FIG. 8.
A - WORM SPINDLE
B - GOVERNOR WEIGHT
C - SPRING
D - GOVERNOR HOUSING
G - WORM GEAR
W - WORM
1 - POSITION OF D FOR
SPEED OF 8 PICTURES
PER SEC.
2 - POSITION OF D FOR
SPEED OF 16 PICTURES
PER SEC.
3 - POSITION OF D FOR
SPEED OF 32 PICTURES
PER SEC.
C D
The governor of the Filmo 70- D camera.
the film tension over a large film area, completely eliminating the
necessity of pressure upon the back surface of the film.
The space between the aperture plate and the back plate is fixed
to permit a free passage of the film with provision, through a spring
arrangement, for allowing the passage of the splices attaching the
paper or film leader to the light sensitive material.
We wish to emphasize here the importance of the elimination of
back pressure, since it reduces to a minimum the danger of scratch-
ing either one of the two film surfaces, especially for those processes
such as Kodacolor, in which both surfaces of the film play an essen-
tial part. This type of film tension permits an equal degree of
accuracy of registration for both forward and backward running
of the film, which accounts for the steadiness of the picture during
the process of projection.
The speed of the camera is controlled by a governor of entirely
434
JOSEPH A. DUBRAY
[J. S. M. P. E.
new design, which permits accurate variations of speed from 8 to
64 picture frames per second, and at any of the intermediate speeds.
A worm, W, of hardened and polished steel, which is an integral
part of a shaft, A , has its teeth angularly cut so as to properly engage
into the teeth of the driving gear, G. The shaft is mounted in an
adjustable hardened steel bearing with a ball thrust. Four weights,
B, each mounted on a spring, C, are permanently fastened to the
worm shaft.
The speed of rotation is controlled by the sliding outer housing, D,
A - CAMERA
APERTURE
B - SHUTTER &
CAM ASSEMBLY
C - OPERATING
BUTTON
D - STOP PAWL
E - GRAVITY LATCH
S - RECOIL SPRING
DIRECTION OF
ROTATION OF SHUTTER
FIG. 9. Stop control of the Filmo 70-D camera.
which regulates the tension of the springs, C, by means of the flexure
control collar, which is rotatably mounted in the housing, D, and is
controlled by the speed control dial on the outside of the camera
case.
In the figure, position 1 of the case, D, corresponds to a speed of
8 picture frames per second; position 2, to a speed of 16 frames
per second; and position 3, to a speed of 32 frames per second. If
the sliding case, D, is set at the end of its allotted path, the camera
mechanism will feed the film at the maximum speed of 64 picture
frames per second. The action of the governor is instantaneous.
This extremely important characteristic permits the use of high
speeds without sacrificing the feature of securing a positive stopping
of the camera while the shutter is in its position of occultation.
While the governor can be set for any desired speed within the
range of from 8 to 64 pictures per second, the setting and indicator
April, 1930] NEW SIXTEEN MILLIMETER CAMERA 435
dial on the outside of the camera case is, for the sake of simplicity,
graduated only for the speeds of 8, 12, 16, 24, 32, 48, and 64 picture
frames per second. The constancy of the camera speed has been ob-
tained through exacting calculations of the length, weight, and tension
of the driving spring and through the above-mentioned instantaneous
action of the governor.
An oiling system is provided so that all moving parts are auto-
matically lubricated while in operation. Oil holes are conveniently
placed and are easily accessible. The governor oiling system consists
of an especially designed oil reservoir with felt filling, which is in con-
stant contact with the worm gear and which supplies a continuous
flow of fresh lubricant on the governor worm. The capacity of the
oil reservoir is calculated so as to insure proper lubrication for a
considerable length of time.
It is quite obvious that in a camera operating at as high a speed
as 64 picture frames per second, the problem of securing a positive
start and stop of the mechanism, in order to avoid differences in
exposures during these periods, and the total loss of picture frames,
would present some serious difficulties. These problems were solved
by devising a unique system of stop pawl and recoil spring, controlled
by the camera operating button, which insures a positive start of
the mechanism at the desired speed and an equally positive stop at
all speeds.
At the moment that the camera release button, C, is pressed down,
the stop pawl, D, disengages from the recoil springs, S, allowing the
mechanism to function at the speed controlled by the governor.
The instant the operating button is released, the stop pawl engages
the recoil spring, the weight and tension of which are so calculated
as to minimize the shock of sudden arrest. The action of this
stop control, added to the instantaneous action of the governor,
eliminates the possibility of even the slightest appearance of either
acceleration or deceleration.
In presenting this new camera to the public, the Bell & Howell
Company feels confident that it will stimulate a further interest in
amateur cinematography the world over.
THE ACADEMY OF MOTION PICTURE ARTS AND
SCIENCES AND ITS SERVICE AS A FORUM
FOR THE INDUSTRY
FRANK WOODS*
A leading figure in the industry was addressing a meeting of the
Academy of Motion Picture Arts and Sciences. "I agree with the
previous speakers," he said. "The first rush of talking picture pro-
duction is settling into a longer and steadier stride. We have revo-
lutionized a great creative art and business to the end that it shall
be a more expressive art and a better business. New methods to use
new machines to secure new effects were thrust upon us hardly more
than a year ago. It was the work of a good many days and nights
as well to get on friendly terms of acquaintanceship with them.
"Now it is time for an inventory. We need to be sure that we
are on a broad foundation. That foundation can only be the widest
possible interest and information in the whole motion picture industry
so that wherever each person makes his individual contribution it will
be intelligently efficient.
"The addition of recorded sound to motion pictures ushered in a
new art form with infinitely greater possibilities as a medium than
the silent motion picture. In this new form the microphone has
taken place alongside the camera as a vital instrument to be skilfully
manipulated, to hear as keenly as the camera sees the idea of the
artist.
"More and more the public demands better quality as the novelty
of sound wears away. The acquirement of this improved technic
involves as a basis an accurate understanding of the principles and
features, the possibilities and limitations of the new tools.
"Nor should this understanding be confined to a few experts.
The production of a motion picture involves a collaboration of a num-
ber of specialized crafts whose functions are interdependent. It is as
necessary for studio employees generally to have an understanding of
the fundamentals of sound recording as it is desirable for the sound
* Academy of Motion Picture Arts and Sciences, Los Angeles, Calif.
436
MOTION PICTURE ARTS AND SCIENCES 437
expert to have an appreciation of screen drama. A mutual under-
standing facilitates communication and the cooperation that is so
vital."
It was with this idea as a keynote that the Academy of Motion
Picture Arts and Sciences undertook a unique, new activity recently
which will continue this year over a period of about three months.
I refer to the first cooperative all-industry school in the fundamentals
of sound recording and reproduction, about which I will give more
details in a moment. The school is designed to intensify one phase
of the Academy's many sided work as the forum of the motion pic-
ture industry on the West Coast.
The Academy is an experiment in organization engineering. It
represents the increasingly successful attempt to combine in one
unified body the members of the several associated but diversified
creative arts on the basis of friendly cooperation for the common
good. Its present membership of 388 includes nearly all of the
principal actors, directors, producers, technicians, and writers in
Hollywood.
One of the most profitable of the Academy activities bearing on
the technical side of the industry has been a long continued series of
joint meetings among the different branches. On one night, for
instance, directors will tell how they suffer between the eccentricities
of the producers on the one hand and those of the microphone
crew on the other. A subsequent meeting gives the sound men
their inning and arc lights have seldom been needed to warm up the
debate between sound men and directors or actors. At present in a
number of general Academy meetings the recording experts are hold-
ing forth for the benefit of the non- technical branches. "Artistic
Possibilities of Acoustic Control," was discussed recently, and "Dub-
bing" (or re-recording) will be taken up this month.
Getting nearer the laboratory itself, a joint committee of three
producers and three technicians is now engaged in studying the possi-
bility of a program of research along non-competitive lines for the
benefit of the whole production industry. This will supplement
the Technical Bureau of the Producer's Association and concern
itself with problems of a somewhat different nature. Pending the
first report of the committee no more specific announcement can be
made.
The present liaison work of the Academy on problems affecting
theaters and studios arose from the occurrence of a semi-emergency,
438 FRANK WOODS [J. S. M. P. E.
which is discussed further in another paper. 1 On the basis of a sur-
vey of conditions a practice for camera and projector apertures has
been recommended by the Academy Technicians' Branch in con-
junction with the Pacific Coast Section of the S. M. P. E., the
American Society of Cinematographers, and the California Chapter of
the American Projection Society. A committee is now studying
recommendations to correlate practice on release print leaders.
Another has for its subject the complex problem of measuring and
equalizing screen illumination as between studios, laboratories, and
theaters. Both of these will work in advisement with the S. M. P. E.
Standards Committee.
The technical school for studio employees which began September
17th developed in a way that it should be admitted, frankly, was a
surprise. A meeting of producers and technicians passed a reso-
lution asking the Academy Board to consider sponsoring a class
with studio employees as students and recording experts as teachers.
The idea was to provide, for the first time in the industry, a systematic
resume of the fundamentals of sound recording and reproduction in
language that it wouldn't take a slide rule to understand.
The executives of the sixteen principal studios heartily arranged
cooperation, as did the heads of the sound departments. The class
was planned for 100 students but a check-up soon showed that nearly
500 had paid the nominal fee of $10 in advance and secured the sig-
nature of both their department heads and an Academy member to
their applications. Quotas had to be allotted and the studio execu-
tives personally selected the 250 students who now make up the
first class, divided into two sections, of 125 each, and meeting one
evening a week for the two-hour lecture demonstrations. At the
time this paper was written it seemed probable that the Academy
Board would authorize organization of a second class of 250 and
others to follow from time to time.
The students make up a cross section of the studio personnel al-
though a majority are from the sound departments.
The first four lectures, following an introductory talk by William
C. de Mille, vice-president of the Academy, have been given by
professors of two universities neighboring Hollywood. Professor
A. W. Nye, head of the Physics Department of the University of
Southern California, discussed the nature of sound in two lectures.
1 COWAN, LESTER: "Camera and Projector Apertures in Relation to Sound-
on-Film Pictures," J. Soc. MOT. PICT. BNG., XIV (Jan., 1930), No. 1, p. 108.
April, 1930] MOTION PICTURE ARTS AND SCIENCES 439
He was followed by Dr. Vern O. Knudsen, associate professor of
physics at the University of California at Los Angeles, and vice^
president of the Acoustical Society of America, who discussed the
nature of speech and hearing and architectural acoustics.
Three men are taking part in a lecture devoted to recording sound
for motion pictures, covering briefly the various methods of recording.
Dr. Donald MacKenzie, technical service engineer for Electrical
Research Products, Inc., will give the general principles of the
Western Electric System. This will be amplified in so far as the
Fox-Case method is concerned by E. H. Hansen, who was an expert
with the Fox- Case Company previous to his present association as
operating head of the Fox Studios sound department. The features
of the RCA Photophone System will be explained by Ralph Town-
send, supervising engineer for RCA Photophone studios on the west
coast.
Reproduction in the theater will be discussed by S. K. Wolf,
theater acoustics engineer for Electrical Research Products, Inc., of
New York, and by John O. Aalberg, engineer in charge of repro-
duction in RCA Photophone studios.
The possibilities of acoustical control in recording and reproduction
will be outlined by J. P. Maxfield, recording engineer for Electrical
Research Products, Inc.
The subject of re-recording will be taken up by Kenneth F. Mor-
gan, supervising engineer of the recording department of Electrical
Research Products. This talk will precede a comparative dis-
cussion of film and disk recording by Nugent H. Slaughter, chief
engineer in charge of recording for Warner Brothers Vitaphone pro-
ductions, and Albert W. De Sart, technical director for Paramount-
Famous-I/asky Studios.
The two final meetings will be devoted to practical problems
in recording and reproduction, including demonstrations in the dif-
ferent studios. In these lectures four men will take part: Douglas
Shearer, recording engineer in charge of the sound department at
Metro-Goldwyn-Mayer Studios; John K. Hilliard, sound director at
United Artists Studios ; C. Roy Hunter, sound director at Universal
Studios; and L. E. Clark, technical director of sound at Pathe
Studios.
Roy J. Pomeroy, a pioneer sound director who is credited with in-
stalling the first sound-on-film equipment in Hollywood, will discuss
the future of sound in motion pictures.
440 FRANK WOODS
For the benefit of the students the Academy library is being
supplemented to include all the standard books on sound and allied
subjects as well as the various journals. The S. M. P. K. Trans-
actions have an important place here, of course.
In response to a widely expressed demand that the authoritative
material included in the lectures before the school be made available
in more permanent form, the edited texts of the lectures are being
printed as papers for the members of the class. A limited number
will also be printed for general distribution.
EDITOR'S NOTE: This paper was presented to the Society in
October, 1929. Since that time many of the things described by
Mr. Woods as part of the future program of the Academy have
become accomplishments.
THEATER LIGHTING*
In a previous report, the Theater Lighting committee's preliminary
survey of lighting conditions in theaters was described and the plans
for a more extensive survey discussed. It was first thought that it
would be desirable to obtain data in a relatively large number of
theaters, getting as complete information as possible, including phases
not embraced in the preliminary survey, and a complete test outline
was worked up.
Since the last meeting of the Society, the committee has been able
to study the problem from a broader viewpoint, from which it
appears that the more advisable procedure is the obtaining of illumi-
nation intensity and brightness measurements in a relatively small
number of theaters, especially selected by the committee because of
certain desirable and undesirable characteristics. On the occasion
of a committee meeting held during the summer, several theaters in
Rochester were visited and the lighting at each criticized. At these
theaters a number of unsatisfactory conditions were noted, such as
too abrupt changes in lighting intensity, excess of extraneous light on
the screen, distracting light sources near the line of vision, screen
surroundings, and front of theater too dark, etc.
Particular study has been made of the relation of screen bright-
ness, screen surroundings, and front wall brightnesses to vision.
Using values actually obtained in theaters, Holladay's data were
employed to check two principal factors: first, whether the bright-
ness contrasts obtained were satisfactory from the standpoint of
comfort, and second, whether they interfered appreciably with
visibility.
From the standpoint of visual comfort, the worst conditions obtained
when a very light film, say, an animated cartoon with a light trans-
mission of 80 per cent, is viewed from a close distance with the screen
surroundings very dark, such as black velvet with a brightness of
0.0002 millilambert. Using the arbitrary scale developed by Holla-
day, the contrasts produced with a screen brightness of 24 millilam-
berts gave a condition which can be designated as uncomfortable.
* Report of Theater Lighting Committee, Nov., 1929.
441
442 THEATER LIGHTING [J. s. M. p. E.
The same film reviewed at about three times the distance (approxi-
mately 72 feet) causes less visual shock and could be classified as
almost perceptibly uncomfortable with dark surroundings, and with
screen surroundings ten times as bright could be classified as almost
comfortable.
Table Showing the Visual Comfort Scale (Holladay]
Scale Value Sensation Classification
. 3 Scarcely noticeable
. 6 Most pleasant
. 9 Still pleasant
1 . 2 Limit of pleasure
1 . 5 Very comfortable
1 . 7 vStill comfortable
1 . 8 Less comfortable
1 .9 Boundary between comfort and discomfort
2 . 2 Perceptibly uncomfortable
2.4 Uncomfortable
2.6 Boundary between objectionable and intolerable
2.8 Irritating
Somewhat different conditions exist when film more nearly average
in character is projected. Using in this case a screen brightness only
one-eighth that for the light film and a viewing distance of 25 feet,
the sensation could be classified as comfortable for dark screen
surroundings; and the sensation would be at the limit of pleasure,
that is, the higher limit of that brightness which is pleasant to view,
when the screen surroundings were increased to ten times the bright-
ness or approximately that which would obtain in a theater which
had a buff front wall illuminated to about 0.004 foot-candle and
surfaces surrounding the screen of about the same illumination and
brightness.
From the standpoint of visibility, conditions are best when the
screen surroundings are darkest. This condition, however, is the
least pleasant from the standpoint of visual comfort. Calculations
from data furnished by the same authority indicated, however,
that the changes in visibility are very small, within the range of change
in screen brightness referred to previously, that is, from black velvet
surroundings to materials reflecting about ten times as much light,
so that it would appear that visual comfort is the more important
factor and that the screen surroundings may be made as bright as is
practical from the standpoint of lessened contrasts due to extraneous
light reaching the screen.
April, 1930] THEATER LIGHTING 443
Since conventional methods of obtaining of brightness measure-
ments in the theater become a very laborious job, the possibility o~f
obtaining measurements photographically was discussed. An in-
vestigation of possibilities indicates, however, that for the present
at least this method would not be practicable. It appears necessary,
therefore, to use portable photometers to obtain the brightness
measurements still required by the committee. It is the plan to
confine further measurements to a very few theaters in which limit-
ing or good conditions obtain and at the same time combine with them
data on comfort and acuity observations made by at least two com-
mittee members working together and, if possible, others making
observations at the same time.
The recommendations of the Japanese National Committee on
Cinema Lighting, presented at the last meeting of the International
Commission on Illumination, specified an average intensity of screen
illumination of about 2.3 foot-candles. This value is considerably
below that obtained in most theaters in this country. Other inter-
esting features of the report are the recommendations that for long
pictures the sessions be arranged so that the duration for a con-
tinuous viewing shall not exceed two hours, and the inclusion of
recommendations on ordinary lighting to the effect that there shall
be enough light to distinguish the spectators' countenances, gradual
diminution in the lighting of the lamps, and the gradation of in-
tensity between the main auditorium and the exterior of the theater.
Respectfully submitted,
F. BENFORD F. M. FALGE L. A. JONES
A. C. DOWNES R. E. FARNHAM I. L. NIXON
CARL E- EGELER, Chairman
REPORT OF PROJECTION COMMITTEE*
VENTILATION OF LAMPHOUSE AND RHEOSTAT ROOMS
In its initial report to the Society last Spring the Projection Com-
mittee stated that the ventilation section of the report was far from
complete, but promised to go more thoroughly into the matter in the
succeeding six months.
Some progress has been made, but the section is still incomplete.
No definite data has been secured regarding the volume of smoke
and gas that may be expected in the case of a film fire. Until this
is done all recommendations as to the ventilation necessary to re-
move these fumes would be purely guesswork.
With regard to the ventilation of the lamphouses and rheostat
room, however, the problem is much more simple. Starting with the
reasonable assumption that the vent flue temperature should not
exceed 300 F., it becomes merely a problem of calculating the air
volume necessary to carry away the wattage dissipated at the
temperature rise of 230F.
Considering the case of the large de luxe theater, it is not un-
reasonable to assume that within a few years the connected load
will be about as follows:
4 H. I. Arcs, each 150 amps, and 80 volts 48,000 watts
2 Stereo Arcs, each 50 amps, and 50 volts 5,000 watts
2 Effect Arcs, each 100 amps, and 60 volts 12,000 watts
2 Spot Arcs, each 100 amps, and 60 volts 12,000 watts
Total 77,000 watts
It is, of course, not likely that all of this load will be connected
at any one time, but the draft adjustment for best results is quite
critical; consequently, it is impractical to install a system having
capacity less than sufficient to care for all equipment simultaneously.
Such a system then should be capable of removing 77,000 watts
continuously with a temperature rise of 230F. This 77,000 watts
is equivalent to 4380 Btu. per minute and, assuming a temperature
rise of 230 F. and a specific heat of 0.25 for the flue gas, we find the
* October, 1929.
444
REPORT OP PROJECTION COMMITTEE 445
system should exhaust 76.2 Ib. of gas or 1456 cu. ft. per minute.
This is in the ratio of one cu. ft. per minute for each 53 watts of total
connected load, and this ratio might be used to calculate the ven-
tilation requirements for smaller installations.
At this point it should be mentioned that to draw this relatively
large quantity of air through a lamphouse without affecting the
stability of the arc will require very careful lamphouse design. Vent-
pipes should be as large as possible near the lamphouse (pipes eleven
inches in diameter have been used on 100 ampere arcs with decidedly
beneficial results) but the system as a whole should have sufficient
"ventilation resistance," so that atmospheric conditions will have
but a negligible effect. The ventilation characteristics of some
high intensity lamphouses have been improved by moving the vent-
pipe forward from the center of the top to a position directly over
the positive flame.
In the case of the rheostat room the problem is slightly different.
Here, due to the need for accessibility, the use of tightly fitting flues
is not practical, and lower temperatures must prevail, but only the
maximum wattage to be dissipated for an extended period of time
need be considered. For the large installation before mentioned,
assuming a line voltage of 115, this will be about as follows:
2 Spots each 100 amps, and 55 volts 11,000 watts
1 Flood 150 amps, and 35 volts 5,250 watts
2 Effects each 100 amps, and 55 volts 11,000 watts
1 Projector 150 amps, and 35 volts 5,250 watts
Total 32,500 watts
This is equivalent to 1850 Btu. per minute and, assuming a tem-
perature rise of 30 F., the system should have a capacity of 3475 cu.
ft. per minute, or one cubic foot per minute for each 9.3 watts. This
ratio would, of course, apply for any type of converting or controlling
equipment merely by applying it to the total watts lost over a period
of time.
The constants used in the foregoing calculations were taken from
Babcock & Wilcox' Steam, and are as follows:
Approximate specific heat of flue gas at 300 F. = 0.25
1 pound air at 100 F. = 14.1 cu. ft.
1 pound air at 300 F. = 19.1 cu. ft.
1 kilowatt hour = 3413 Btu.
44(i REPORT OF PROJECTION COMMITTEE [j. s. M. p. E.
PROBLEMS OF THE PROJECTIONIST
The Chairman of your committee was obliged to devote two of
the past six months to some special work. This caused the piling
up of so much regular work that it has been impossible to give the
work of the Projection Committee that attention it should have had.
However, what we shall lay before the Society is perhaps even
of greater importance than would be some one of the other many
things your committee has under consideration. In fact, your
committee feels that what we shall set before you is deserving of
your very serious attention, and such action as you may see fit to
take along the lines we shall suggest.
Gentlemen, we would direct your attention to the fact that the
chief thing now needed to improve the excellence of screen images in
our many thousands of theaters, is that projectionists be helped and
encouraged to make every possible effort to get from the really splen-
didly efficient equipment now t available its full possible excellence
in performance.
In the years now past the procedure has been, save in a relatively
few isolated cases, almost exactly the opposite. It is but a statement
of plain, known fact to say that in the past a very large percentage
of the men engaged in projection have met with what has amounted
to a literally astounding amount of discouragement. Many have
been forced to work with equipment which had entirely outlived its
day of usefulness, and in addition was in a literally terrible state
of disrepair.
There has been a decided tendency to belittle the work of pro-
jection and to make light of it. There has even been a tendency,
in not a small number of our theaters, to impress upon the mind of
the projectionist the idea that the study of technical matters relating
to projection is of very little importance and that all such matters
are being and would be attended to by others; that projection is
purely a mechanical and electrical operation which can be performed
acceptably by almost any one after a bit of coaching.
This attitude toward projection and the projectionist has been
taken by a large number of theater managers apparently under the
impression that such a course would tend to induce projectionists to
accept less money than would be the case were they encouraged to
respect their profession and to regard its work as of high importance.
These men have overlooked or ignored the fact that the discourage-
ment set up by such a course might well react in such a way that
April, 1930] REPORT OF PROJECTION COMMITT^ 447
there would be far greater loss at the box-office by failure to place
the product of the motion picture industry before the public at its
highest entertainment and amusement value, and by excessive ma-
chinery deterioration caused by the indifference thus generated in
the mind of the projectionist, than any rise in wages could possibly
amount to.
Gentlemen, the excellence of everything this great industry has for
sale to the public is in considerable measure directly dependent upon
the excellence with which it is displayed upon the theater screen.
As has been many times pointed out to you, if a production be poorly
or indifferently projected on the screen, then its entertainment value
is automatically lowered as against what it would have been had it
been projected in the best possible manner. You know that; we all
know it.
We also know that men engaged in any line of human endeavor will
do far better, more perfect work if they are encouraged to believe
the work they are engaged in is of real importance, and is therefore a
work in which they may and should feel pride.
This being true, and we believe you must all agree that it is true,
would it not have beneficial effect did this Society take such steps
as may seem practicable to encourage rather than discourage high
class work in projection, to the end that the finished product of this
great industry be placed before its buyers at its highest possible
value?
In line with this proposal your committee respectfully suggests:
(a) that the President of the organization controlling motion picture
projectionists, the I. A. T. S. E- and M. P. M. O., be invited to join
this Society; (b) that this Society, either through its officers or
through a committee to be appointed by our President, confer with
the President of the before-named organization with the idea of
inducing him to favor the establishment of a suitable apprenticeship
system by means of which candidates for membership in his or-
ganization may approach with a good basis of both practical ex-
perience in the work of projection and technical knowledge relating
to it; (c) that he also be urged to use every possible means for in-
ducing the local units of his organization to encourage the production
of the best possible work by their members.
Admitting that what we propose cannot be expected to work
any immediate large benefits, we direct your attention to the fact
that we ask nothing which is difficult of accomplishment and that
448 REPORT OF PROJECTION COMMITTEE [j. s. M. P. E.
in any event no possible harm can be done by acquiescence to our
proposal. On the other hand, it will indicate that this Society
recognizes the high importance of excellence in the work of pro-
jection and proposes to put its weight behind the movement for its
betterment. It also will be visual evidence to the projectionist that
at last a really authoritative body other than his own organization is
giving direct, official recognition to both him and his work.
Respectfully submitted,
A. H. GRAY HARRY RUBIN
C. L. GREENE J. H. KURLANDER
HERBERT GRIFFIN M. S. SWAAB
LESTER ISAACS F. H. RICHARDSON, Chairman
DISCUSSION
MR. C. L. GREENE: I wish to state, in the event that the Society sees fit to
accept and approve the ventilation section of the report, I have a request to make
particularly of the members of the Society who are now connected with develop-
ments in wide films. When I wrote the supplement, I thought I was being far-
sighted when I assumed an average of 150 amperes for the projection arc for
wide film, but before the first session had been on two hours I heard discussion
of 200 and 250 ampere arcs. As work progresses, if the men who are in a posi-
tion to know what requirements are going to be placed on ventilation would
keep the Projection Committee advised along that line it would greatly facilitate
our work.
MR. EDWARDS: If the Chairman spoke of the lack of appreciation of pro-
jection by the SOCIETY OF MOTION PICTURE ENGINEERS I think it was a slip. I
don't think that is quite what was in his mind. I believe that suggestion with
regard to the President of the International Alliance becoming a member of the
Society is something of value. We happened to have the gentleman in here
this morning. I think it is the first time he has sat in on even a portion of our
proceedings, and I can assure you he was very much impressed by the type of
paper being presented. He was frank to tell me, "I don't understand very much
about that, but it engenders new thought, and that is what the industry needs
in all branches."
MR. RICHARDSON: I didn't say the Society lacks appreciation; I said every-
body.
You have the whole official staff of the organization I mentioned in this building,
and it has been suggested that you appoint a committee to cooperate. It should
have consideration by the Society.
PRESIDENT PORTER: The body is considering it.
MR. RICHARDSON: You will never have another opportunity like the present
one. I move that a committee be appointed to confer with the Board of Inter-
national Alliance and find what their attitude would be and if official results can
be obtained.
April, 1930] REPORT OF PROJECTION COMMITTEE 449
PRESIDENT PORTER: Do I hear a second to the motion?
MR. TAYLOR: It seems to me that the lack of action results from general
unfamiliarity with the suggestion. I don't know enough about it to be for it
or against it. I think the Board of Governors is better able to handle it than
the Society is.
MR. COFFMAN: I move that the report be referred to the Board of Governors
for action.
(Motion duly seconded and passed.)
ABSTRACTS
The Editorial Office will welcome contributions of abstracts and book reviews
from members and subscribers. The customary practice of initialing abstracts
will be followed.
Contributors to the abstract section of this issue are as follows: G. L. Chanier,
Clifton Tuttle, and the Monthly Abstract Bulletin of the Kodak Research
Laboratories.
Solving the "Ice Box" Problem. W. STULL. Amer. CinemaL, 10, September,
1929, p. 7. An account of the various methods which have been used to silence
the motion picture camera. Present-day practice attempts to stop the noise as
near the camera as possible. Various types of sound absorbing casings for the
camera are replacing the old type of sound booth. C. M. T.
New Portable Model RCA Photophone. H. L. DANSON. Ex. Herald World,
97, Sect. 2, Oct. 26, 1929, p. 58. The entire projector and sound reproducer sys-
tem is housed in an all metal cabinet 24 inches square and 12 inches wide, mounted
on four adjustable telescopic legs. The amplifier is housed in a separate metal
cabinet of similar size. Volume control permits adjustment in graded steps from
zero to maximum volume. -Accommodation is made in the amplifier for a second
projector to permit smooth change-over. The speaker is an electrodynamic
moving coil cone type. Film speed is standardized at 90 feet per minute and the
projector operates/ from a power source of 110 volts, 60 cycles a. c. Recording
facilities are offered by the RCA Photophone at its Grammercy Studios in New
York. Kodak Abstr. Bull.
Sound on a Wire. Stille Electromagnetic System Reviewed. Bioscope
(Mod. Cinema Technique), 81, Oct. 16, 1929, p. vii. A steel wire or band is run
between the poles of an electro-magnet, which is connected in the ordinary way
to a microphone. The variations in the current density produced in the micro-
phone are impressed electromagnetically on the traveling ribbon or wire. By
passing the magnetized wire at a correct constant speed between the poles of the
solenoid again, variations are produced in the magnetic field corresponding to
those which were impressed on the wire. These variations may be amplified to
give sound reproduction. The record is permanent under ordinary conditions,
but may be completely removed by passing the wire or tape through an electro-
magnetic field of constant intensity. C. M. T.
Acoustimeter. R. F. NORRIS. Projection Eng., 1, September, 1929, p. 43.
The output from a four stage transformer coupled amplifier is measured with a
thermo-junction meter calibrated to read sound intensity. A Baldwin type
magnetophone is used as the pickup. C. M. T.
Burt Reproducer for Talking Motion Pictures. Projection Eng., 1, September,
1929, p. 50. This reproducer, manufactured by the R. C. Burt Scientific Lab-
oratories, is stated to have several advantages over other types. A synchronous
motor drive without flexible drive shafts or universal points is ysed. The cell has
ABSTRACTS 451
a high output therefore less amplification is required than is usual. Two cells are
mounted so that a replacement can be readily made hi case one cell ceases to
function. C. M. T.
Light Sensitive Cells. JOHN P. ARNOLD. Projection Eng., 1, September,
1929, p. 44. The properties of photo-conductive, photo-electric, and photo-
voltaic cells are briefly described. C. M. T.
Ufa Sound Studios. An Original Lay-Out. Kinemat. Weekly, 152, Oct. 24,
1929, p. 30. Four Ufa studios at Neubabelsberg were completed a few weeks
ago. These studios are built about a central portion where all the recording
apparatus and monitors are placed. C. M. T.
New Findings in Sound Theater Acoustics. Ex. Herald World, 97, Sect. 2,
Nov. 23, 1929, p. 30. A summary of observations made in about five hundred
theaters is given. Conclusions reached are: that the previously accepted rever-
beration time value should be corrected, that square theaters are better acousti-
cally than narrow theaters, and that seats should be made to absorb the same
amount of sound whether occupied or not. C. M. T.
New Sound Film Process. G. SEEBER. Phot. Ind., 27, April 3, 1929, p. 389.
In this modification of the Poulsen magnetized wire memograph, the film base
itself is made magnetic by the incorporation of colloidal particles of a magnetic
alloy cobalt, nickel, and iron. C. M. T.
Amplifiers and Hookups to Minimize Distortion. P. HATSCHEK. Film-
technik, 5, Aug. 3, 1929, pp. 353-9. The principles of vacuum tube amplification,
distortion, general characteristics of resistance coupled and transformer hookups,
and explanation of push-pull amplification are given. Kodak Abstr. Bull.
Make-Up Tests by the American Society of Cinematographers. Amer.
Cinemat., 10, November, 1929, p. 13. Tests to determine the best make-up for
panchromatic film and for color photography have been conducted at the Tec-
Art studios under the auspices of the American Society of Cinematographers.
It is reported that a new series of paints and greases have been found which
photograph as they appear to the eye. The results will be embodied in a quick
reference make-up chart. C. M. T.
Lighting "Rio Rita." Internal. Phot., September, 1929, p. 12. A total in-
candescent wattage of 976,000 was used during the eight days of filming the color
sequences of "Rio Rita." C. M. T.
The Schiifftan Process of Model Photography. HANS NIETER. Phot. J.,
January, 1930, p. 16. A method of combining actual photography and model
photography to create the illusion of immense settings upon the screen. This
method uses a mirror of special silvered glass set at an angle to, and near the lens
of the camera. A model of the set is constructed. The necessary parts of this
set are built upon the studio floor. The mirror is scratched away to allow this
portion to be seen by the lens through the clear glass, the rest of the mirror re-
flecting to the lens the image of the model which matches perfectly with the parts
of the set built on the stage. G. L. C.
Pan Film. Camera Craft, 36, November, 1929, p. 526. The use of panchro-
matic film has made it necessary for the lens designer to correct his objectives for
all colors. C. M. T.
New Depth Process for Motion Pictures. Mot. Pict. Projectionist, 2, Septem-
ber, 1929, p. 37. The appearance of depth in a picture is obtained by photo-
452 ABSTRACTS
graphing the object through a screen of very narrow transparent vertical lines
while the camera is moved in an arc around the object, at the same time moving
the plate horizontally the width of the lines. When the picture is shown a line
screen is placed in front and the two views give an appearance of depth. Kodak
Abstr. Bull.
Measure of the Effective Luminosity of Objectives. J. HRDLICKA. Photo-
Revue, 41, Sept. 1, 1929, p. 267. A simple method is described for finding the
effective relative aperture of photographic objectives, by taking into considera-
tion the loss of illumination through reflection and absorption in the lens. An
objective rated at //4.5 is found to have an effective aperture of only //5.54. -
Kodak Abstr. Bull
Lens Viewing Angles. J. DUBRAY. Internal. Phot., 1, September, 1929, p. 14.
Formulas are given which enable the cinematographer to make a rapid cal-
culation of the width of object space embraced by lenses of different focal lengths
for both sound and silent apertures. C. M. T.
Distribution of Light Flux from a Mirror Arc. H. NAUMANN. Filmtechnik, 5,
Aug. 31, 1929, p. 389. The author uses a photographic method to examine the
intensity distribution from a mirror arc. The effects of changing arc current or
its position with respect to the mirror and of altering the size of the projection
objective are illustrated by silhouette photographs. Serious disturbance of the
illumination of the film aperture may result from poor adjustment of the arc and
reflector. C. M. T.
Color and Its Measurement. J. GUILD. Phot. J., January, 1930, p. 22.
The paper deals with the question of applying a standard system of measurement
to the color of objective things. Though we can apply physical measurements
to the properties of the stimulus of vision, we cannot evaluate the sensation of
brightness or that of color. The author discusses Young's trichromatic theory,
then studies the effects of visual conditions on color measurement, explaining
why the National Physical Laboratory recommends the use in all color measuring
apparatus of a field subtending an angle of 2 degrees. With an angle of this size
measurement is not affected by the brightness of the field or the adaptation and
fatigue of the 1 eye. Standardization of color measurements is more easily effected
in the case of additive colorimeters, several of which are described. For standardi-
zation of measurement, it is recommended that color measurements be expressed
on the trichromatic system. The standardization of the illuminant and the
method of illumination are then discussed, as well as the question of the "normal
eye" and the problem of correcting the observer's eye by means of auxiliary
filters. G. L. C.
Dental Profession Uses Motion Pictures. Intern. Phot. Bull., February, 1930.
No less than ten reports made at the 66th Meeting and Clinic of the Chicago
Dental Society were illustrated with 16 mm. motion pictures, one of them showing
the physiology of mastication made entirely by Dr. Hugh McMillan. G. L. C.
SOCIETY OF MOTION PICTURE
ENGINEERS
OFFICERS
President
J. I. CRABTREE, Eastman Kodak Co., Rochester, New York
Past President
L. C. PORTER, General Electric Co., Nela Park, Cleveland, Ohio
Vice-Presidents
H. P. GAGE, Corning Glass Works, Corning, N. Y.
K. C. D. HICKMAN, Eastman Kodak Co., Rochester, N. Y.
Secretary
J. H. KURLANDER, Westinghouse Lamp Co., Bloomfield, N. J.
Treasurer
W. C. HUBBARD, General Electric Vaporlamp Co., Hoboken, N. J.
Board of Governors
H. T. COWUNG, Eastman Teaching Films, Inc., 343 State St., Roches-
ter, N. Y.
J. I. CRABTREE. Research Laboratory, Eastman Kodak Co., Roches-
ter, N. Y.
H. P. GAGE, Corning Glass Works, Corning, N. Y.
K. C. D. HICKMAN, Research Laboratory, Eastman Kodak Co.,
Rochester,, N. Y.
W. C. HUBBARD, General Electric Vaporlamp Co., Hoboken, N. J.
J. H. KURLANDER, We'stinghouse Lamp Co., Bloomfield, N. J.
W. C. KUNZMANN, National Carbon Co., Cleveland, Ohio
D. MACKENZIE, Electrical Research Products, Inc., 7046 Hollywood
Blvd., Los Angeles, Calif.
r P. MOLE, Mole-Richardson, Inc., 941 N. Sycamore Ave., Holly-
wood, Calif.
M. W. PALMER, Paramount-Famous-Lasky, Inc., 6th & Pierce Aves.,
Long Island City, N. Y.
L. C. PORTER, General Electric Co.. Nela Park, Cleveland, Ohio
S. ROWSON, Ideal Films, Ltd., 76 Wardour St., London, W. 1,
England.
E. I. SPONABLE, 277 Park Avenue, New York, N. Y.
453
454
[J. S. M. P.
J. G. CAPSTAFF
COMMITTEES
1929-1930
Color
W. V. D. KELLEY, Chairman
W. T. CRESPINEL F. E. IVES
Convention
W. C. KUNZMANN, Chairman
J. W. COFFMAN W. C. HUBBARD M. W. PALMER
Historical Committee
F. J. WILSTACH, Chairman
M. CRAWFORD C. L. GREGORY T. RAMSAYE
C. F. JENKINS
O. NELSON
J. W. COFFMAN
Journal
L. A. JONES, Chairman
H. T. COWLING
J. H. KURLANDER
W. C. HUBBARD
C. BARRELL
J. W. BOYLE
W. H. CARSON
W. CLARK
Membership and Subscription
H. T. COWLING, Chairman
L. W. DAVEE
J. DEFRENES
B. R. GEIB
J. KLENKE
M. L. MISTRY
B. E. NORRISH
I. ROSEMAN
E. C. SCHMITZ
J. L. SPENCE
F. ZUCKER
M. C. BATSEL
F. J. CADENAS
J. A. DUBRAY
O. M. GLUNT
Papers
J. W. COFFMAN, Chairman
C. R. HANNA
K. C. HICKMAN
E. HUSE
D. HYNDMAN
G. E. MATHER
R. F. NICHOLSON
J. B. TAYLOR
April, 1930]
COMMITTEES
455
Progress
G. E. MATTHEWS, Chairman
J. A. BALL J. B. ENGL A. C. HARDY
J. BOOLSKY R. E. FARNHAM R. C. HUBBARD
W. CLARK H. B. FRANKLIN G. F. RACKETT
A. W. DANESHEW
K. GEYER
S. K. WOLF
H. W. DREYER
G. C. EDWARDS
P. H. EVANS
T. FAULKNER
Projection
L. M. TOWNSEND, Chairman
C. GREENE W. B. RAYTON
H. GRIFFIN H. B. SANTEE
R. H. McCuLLOUGH L. M. TOWNSEND
W. A. MCNAIR D. F. WHITING
R. MlEHLING
F. C. BADGLEY
Publicity
W. WHITMORE, Chairman
B. W. DEPUE
G. E. MATTHEWS
G. F. RACKETT
O. A. Ross
J. W. COFFMAN
Solicitation
E. P. CURTIS, Chairman
E. A. WILLIFORD
Standards and Nomenclature
M. C. BATSEL
W. H. CARSON
L. W. DAVEE
A. DEBRIE
L. DEFOREST
J. A. DUBRAY
E. W. ENGSTROM
A. C. HARDY, Chairman
P. H. EVANS
R. E. FARNHAM
H. GRIFFIN
R. C. HUBBARD
L. A. JONES
N. M. LAPORTE
G. MITCHELL
W. P. POWERS
G. F. RACKETT
W. B. RAYTON
V. B. SEASE
T. E. SHEA
j. P. SPENCE
E. I. SPONABLE
I,. T. TROLAND
L. J. BUTTOLPH
Studio Lighting
A. C. DOWNES, Chairman
R. E. FARNHAM
K. C. HICKMAN
M. W. PALMER
456 COMMITTEES [J. s. M. P. E.
Theater Lighting
C. E. EGELER, Chairman
J. C. AALBERG F. FALGE C. GREENE
F. A. BENFORD R. E. FARNHAM E. HUSE
A. C. DOWNES L. A. JONES
LONDON SECTION
SIMON ROWSON, Chairman
A. NEWMAN, Vice-Chairman PAUL KIMBERLEY, Manager
L. EVELEIGH, Secretary ALAN WILLIAMSON, Manager
H. WOOD, Treasurer WILLIAM VINTEN, Manager
NEW YORK SECTION
M. W. PALMER, Chairman M. C. BATSEL, Manager
D. F. HYNDMAN, Sec.-Treas. T. E. SHEA, Manager
PACIFIC COAST SECTION
P. MOLE, Chairman C. DUNNING, Manager
G. F. RACKETT, Sec.-Treas. E. HUSE, Manager
Membership Committee
J. COURCIER, Chairman
E. JEWELL
Papers and Programs
E. HUSE, Chairman
April, 1930]
COMMITTEE CHAIRMEN
457
W. V. D. KELLEY
Color
W. C. KUNZMANN
Convention
F. J. WlIvSTACH
Historical
L. A. JONES
Journal
H. T. COWUNG
Membership and
Subscription
J. W. COFFMAN
Papers
458
COMMITTEE CHAIRMEN
[J. S. M. P. E.
G. B. MATTHEWS
Progress
L. M. TOWNSEND
Projection
W. WHITMORE
Publicity
B. P. CURTIS
Solicitation
A. C. HARDY
Standards and
Nomenclature
A. C. DOWNES
Studio Lighting
C. B. BGELER
Theater Lighting
April, 1930]
NEW
450
NEW MEMBERS
LERoY O. ANDREWS
New England Theaters Operating
Corp., 19 Milk Street, Boston,
Mass.
JUDD O. BAKER
RCA Photophone, Inc., 411 Fifth
Avenue, New York, N. Y.
WILLIAM P. BIEUCKE
5462 Marathon Street, Los Angeles,
Calif.
GORDON A. CHAMBERS
Eastman Kodak Company, 6706
Santa Monica Blvd., Hollywood,
Calif.
MERRITT CRAWFORD
Bell Telephone Laboratories, Inc.,
463 West Street, New York, N. Y.
P. H. EVANS
Warners Bros. Vitaphone Corp., 1277
East 14th Street, Brooklyn, New
York
WILMORE C. HARCUS
Paramount-Famous -La sky -Cor p.,
5451 Marathon Street, Hollywood.
Calif.
ARTHUR HIGGINS
119 Darley Road, Randwick, Syd-
ney, Australia
FREDERICK L. G. KOLLMORGEN
Kollmorgen Optical Corp., 767
Wythe Avenue, Brooklyn, New
York
CHARLES L. LOOTENS
RCA Photophone, Inc., 411 Fifth
Avenue, New York, N. Y.
DONALD McNicoL
Projection Engineering, 52 Vander-
bilt Avenue, New York, N. Y.
HERBERT MEYER
Agfa Ansco Corp., Binghamton,
N. Y.
LLOYD P. MORRIS
606 West Elm Street, Urbana, 111.
JOHN P. MULLER
2629 Calhoun Street, New Orleans,
La.
HANS M. NIETER
British Schufftan Process, Ltd.,
Elstree, Herts, England
JOSEPH P. O'DONNELL
Cinema Studios Supply Corp., 1438
N. Beach wood Drive, Hollywood,
Calif.
JAMES OLSON
National Theater Supply Co., 2310
Cass Avenue, Detroit, Mich.
Louis I. PAGE
RKO Studios, 780 Gower Street,
Hollywood, Calif.
EUGENE A. PFEIL
71 Root Building, Buffalo, New York
A. SHAPIRO
Universal Stamping and Mfg. Co.,
2839 North Western Avenue,
Chicago, 111.
JOHN H. A. WHITEHOUSE
The Gramophone Co., Ltd., Ruislip,
Middlesex, England
FRANK J. WILSTACH
Motion Picture Producers & Dis-
tributors of America, Inc., 469
Fifth Avenue, New York, N. Y.
CHANGE OF ADDRESS
J. C. AALBERG
RKO Studios, 78 Gower
Los Angeles, Calif.
J. BURGI CONTNER
Street, c/o President Hotel, West
Street, New York, N. Y.
48th
460 SOCIETY NOTES [j. s. M. P. E.
SOCIETY NOTES
The Spring Meeting. Mr. W. C. Kunzmann, chairman of the
Convention Committee, reports that arrangements for the Spring
Meeting, which is to be held at the Wardman Park Hotel, Wash-
ington, D. C., May 5th to 8th, inclusive 1 , are almost complete and a
preliminary program will be circulated to the members very shortly.
The Acoustical Society. The Acoustical Society will hold its con-
vention on May 9th and 10th in the auditorium of the Westinghouse
Lighting Institute in Grand Central Palace, New York, N. Y. The
technical sessions will be devoted to symposiums on "noises" and
loud speakers. This convention was previously scheduled for May
8th and 9th but President Fletcher made arrangements to delay the
convention in order to permit our members to proceed from Washing-
ton to attend this convention.
The Secretaryship. After almost two years of efficient and faithful
service, Secretary R. S. Burnap has resigned. The Society hereby
extends its appreciation and thanks to Mr. Burnap for his valuable
services and expresses its deep regret that his associations with the
Society have been severed.
The Society has been extremely fortunate, however, in that Mr.
J. H. Kurlander o'f the Westinghouse Lamp Company has accepted
the appointment of temporary secretary to conclude the fiscal year.
Mr. Kurlander is well known to many of the older members of the
Society and has been active in the motion picture field for many
years.
Board of Governors Meeting. At the Board of Governors meeting
held on February 4th at Rochester, New York, a large number of busi-
ness matters were transacted including the following.
1. Resolved, that papers presented at the regular meeting shall not be pub-
lished or circulated and shall be considered the confidential property of the
vSociety prior to their appearance in the JOURNAL, except that in case a paper is
not published in the JOURNAL within six months after its presentation, the author
is free to use it in whatever manner he sees fit.
2. The President was instructed to write to the Secretary of the Academy of
Motion Picture Arts and Sciences expressing a desire and willingness on the part
of the Society of Motion Picture Engineers to collaborate with them on technical
matters and especially those dealing with standardization and the preparation of
nomenclature lists.
3. Sections of the proposed revision of the By-Laws of the Society were
modified further as follows:
BY-LAW 7, Section 3, was revised to read as follows: The annual dues
April, 1930] SOCIETY NOTES 461
shall be $20.00 for Active Members, and $10.00 for Associate Members, pay-
able on or before October 1st of each year. Current or first year's dues for
new members dating from notification of acceptance into the Society shall
be pro-rated on a quarterly basis, said quarters beginning October 1st, Janu-
ary 1st, April 1st, and July 1st. Ten dollars of these dues shall apply for annual
subscription for the monthly publication.
The change in this section has1)een made necessary in order to obtain second
class mailing privileges for the JOURNAL.
BY-LAW 10, Section 5, was revised to read as follows: The Board of
Governors shall consist of a Section Chairman, the Section Past Chairman,
the Section Secretary-Treasurer, and two Active Members, one of which last
named shall be elected for a two-year term, and one for one year, and then one
for two years each year thereafter. At the discretion of the Board of Govern-
ors, and with their written approval, this list of officers may be extended.
This revision was made necessary by the need in the case of large sections for a
larger staff to carry on the work of the Section.
4. The chairman of the JOURNAL Committee was informed that the order of
publication of papers in the JOURNAL is placed within the discretion of the editor.
In case early and special publication is desired, papers will preferably be pub-
lished in order of receipt of the complete manuscript for printing by the editorial
office.
5. A petition was received, signed in proper form by ten Active Members of
the Society in good standing, requesting authorization to organize a New York
Section of the Society. A motion was made and passed that this petition be
granted.
The New York Section. An organization meeting was held on March
6th at the Engineering Societies Building, New York, N. Y. About
150 members were present. President Crabtree acted as temporary
chairman and introduced the speaker, Dr. Walter Pitkin of the School
of Journalism, Columbia University, New York, N. Y., who spoke
on "The Psychology of the Sound Picture." He drew attention
to the many shortcomings of the reproduced sounds in the theater,
particularly with respect to noises. The election of officers resulted
as follows: M. W. Palmer, Chairman; T. E. Shea (Long Term),
M. C. Batsel (Short Term), Managers; D. E. Hyndman, Secy.-Treas.
The geographical boundaries of the New York Section have been
denned by the Board of Governors as an area enclosed within a
circle having a radius of 50 miles from Times Square. At this
meeting, however, a motion was made that the Board of Governors
reconsider this matter and recommend the boundaries as those of
the Metropolitan area as denned by the authoritative body.
The Pacific Coast Section. The second meeting of the season was
held in the factory of the Mitchell Camera Company on February
27th. Mr. R. E. Farnham of the General Electric Company reviewed
462 SOCIETY NOTES [J. S. M. p. E.
the character of the emission of luminous bodies in general and of
the tungsten filament in particular. He also demonstrated a tungsten
spot lamp equipped with a heat absorbing water filter. This was
followed by a general discussion on wide film problems together with
a demonstration of the various parts of the Grandeur 70 mm. camera.
The London Section. Our fellow members in London have been
continuing their bi-weekly meetings with systematic regularity.
Many of the papers read at the Toronto convention have been
again presented at these sessions. The program for the remainder
of the year is as follows:
March 10th at Mayfair Hotel First Annual Dinner
March 24th at R. P. S. "Lenses with Special Reference to Color Correc-
tion," by Mr. Warmisham.
April 14th at R. P. S. "Acoustics of Buildings," by Mr. Fleming of the
National Physical Laboratory.
Sustaining Memberships. To date, the following firms have agreed
to take up sustaining memberships for the amounts indicated.
$1000 Memberships
Bell Telephone Laboratories, Inc.
Eastman Kodak Company
Paramount-Famous-Lasky Corp.
RCA Photophone, Inc.
$500 Memberships
Bell & Howell Company
Consolidated Film Industries
Du Pont-Pathe Film Mfg. Corp.
Technicolor Motion Picture Corp.
$100 Memberships
Audio-Cinema, Inc.
Case Research Laboratory
As explained previously, sustaining memberships have been estab-
lished in order to provide a fund of from $9000 to $10,000 annually
for the purpose of acquiring a permanent editor-manager for the
JOURNAL who will also act as assistant secretary-treasurer and also
to enable the Society to establish permanent headquarters in the
Engineering Societies Building, New York, N. Y. All members are
urged to make every effort to persuade their firms to take up sus-
taining memberships in one of the classes indicated.
New Committees. Two new committees have been appointed.
The Historical Committee under the chairmanship of Mr. F..J.
Wilstach will undertake the collection of old films and motion picture
April, 1930] SOCIETY NOTES 463
apparatus of historical interest and place these in a suitable deposi-
tory, such as the National Museum at Washington, D. C. The com-
mittee is also preparing a report on the accomplishments of Messrs.
Lauste and LeRoy in order to assist the Board of Governors in de-
ciding upon a petition recently submitted to the effect that these
men be granted honorary membership in the Society.
The Color Committee under the chairmanship of Mr. W. V. D.
Kelley will undertake the compilation of reports on progress in color
motion picture work.
The Wide Film Situation. Professor A. C. Hardy, chairman of the
Standards and Nomenclature Committee, has appointed a sub-
committee under the chairmanship of Mr. M. C. Batsel of the RCA
Photophone, Inc., which has under consideration the recommen-
dation of dimensional standards for wide film. The sub-committee
is composed as follows: L. W. Davee, L. DeForest, P. H. Evans,
H. Griffin, N. M. LaPorte, J. L. Spence, B. I. Sponable.
The committee has met weekly during the past month and the
prospects of their being in a position to make definite recommenda-
tions in time for the spring meeting are very promising.
The Committee Chairmen. The following notes have been prepared
with a view to better acquainting the members with the various com-
mittee chairmen whose photographs appear on pages 457 and 458.
W. V. D. Kelley (Color). President of the Du Chrome Color Corporation,
Hollywood, California, and formerly Vice-President of Prisma, Inc., and Kelley-
Color, Inc. Mr. Kelley was formerly a member of the Board of Governors and
has contributed articles on color photography to the Transactions.
W. C. Kunzmann (Convention). Member of Sales Division of the National
Carbon Company and a member of the Board of Governors. Mr. Kunzmann has
been in charge of the arrangements for the Society's conventions for many years.
F. J. Wilstach (Historical). Chief of Publicity Department of the Motion
Picture Producers and Distributors of America, Inc. Has been connected with
theater activities for many years and was formerly press agent for Messrs. Schu-
bert, and general manager for Sothern & Marlowe, and DeWolf Hopper.
L. A. Jones (Journal). Past- President of our Society and has held the chair-
manship of the Papers, Publications, and Standards Committees. He is presi-
dent of the Optical Society of America. Mr. Jones has contributed many sci-
entific papers to our Transactions and those of other scientific societies.
H. T. Cowling (Membership and, Subscription). Technical director of the
Eastman Teaching Films, Inc., and a member of the Board of Governors. Mr.
Cowling was previously engaged in the filming of travelogs.
J. W. Coffman (Papers). President of the Audio-Cinema, Inc., and formerly
Vice-President of the Carpenter-Goldman Laboratories, Inc., engaged in the
production of educational films.
464 PACIFIC COAST SECTION [j, s. M. p. K.
G. E. Matthews (Progress). Member of the Kodak Research Laboratories and
has assisted largely in the preparation of Progress Reports for the past two years.
L. M. Townsend (Projection). Member of Sound Division of the Paramount-
Famous- Lasky Corporation and formerly supervisor of projection at the East-
man Theater, Rochester, N. Y. Mr. Townsend has been a frequent contributor
to the Transactions.
W. Whitmore (Publicity). Member of Advertising and Publishing Depart-
ments of the Western Electric Company and formerly on the editorial staff of the
the Exhibitors' Herald-World.
E. P. Curtis (Solicitations). General Sales Manager of the Motion Picture
Film Department, Eastman Kodak Company, Major of Air Corps, Reserve
Section, and Ace of the World War.
A. C. Hardy (Standards and Nomenclature}. Assistant Professor of Physics,
Massachusetts Institute of Technology. A former staff member of the Kodak
Research Laboratories and a contributor of many articles to the Transactions and
JOURNAL.
A . C. Downes (Studio Lighting) . A member of the Research Laboratory of the
National Carbon Company, in charge of carbon electrode -and lamp research.
Mr. Downes has contributed many articles to the Transactions.
C. A. Egeler (Theater Lighting). Illuminating engineer of the National Lamp
Works, Cleveland, Ohio. Mr. Egeler has served previously as chairman of the
Progress Committee.
PACIFIC COAST SECTION, SOCIETY OF MOTION PICTURE
ENGINEERS
MINUTES OF MEETING
February 27, 1930
The second meeting of this season, held in the new factory of the
Mitchell Camera Corporation on Thursday, February 27, 1930, was
called to order by Mr. Peter Mole, Chairman of The Pacific Coast
Section, at 8:30 P.M.
In calling the meeting to order Mr. Mole outlined briefly the broad
aims and policies of the Society, in which it was not only nationally
but internationally functioning, and pointed out the program of ac-
tivity and work undertaken by the Pacific Coast Section for the
current year. The increasing importance to the motion picture
industry, of reliable engineering with a background of scientific
research was explained with its particular importance to the Holly-
wood center of production. The substantial growth of the Pacific
Coast Section with its membership of approximately eighty and
an attendance at this meeting of more than a hundred representative
engineers and technicians was the occasion for requesting an informal
April, 1930] PACIFIC COAST SECTION 465
report from Mr. J. L. Courcier, Chairman of the local membership
committee.
Mr. Courcier stated that it was not the policy of his committee
to solicit membership or conduct a sales campaign but that all those
qualified for membership were cordially invited to make application.
Mr. Courcier brought out the fact that a widespread distribution of
application forms was but a waste and expense to the Society and
that applications would be given to those who indicated a desire
for membership.
At the conclusion of Mr. Courcier's remarks, Chairman Mole
handed the meeting over to Mr. Emery Huse, Chairman of the Papers
and Programs Committee.
Mr. Huse explained that the schedule of the Society, which outlined
color as the subject for the first three meetings, had been changed
to permit this special meeting on the timely subject of Wide Film.
The subject was particularly pertinent because of the opening on
February 25th at the Circle Theater of the first production on
Grandeur Film to be shown on the Pacific Coast.
Mr. Huse also announced that due to the presence of a represen-
tative of the General Electric Company they were to be given a review
of the recent developments in means for cooling the beams of large
wattage incandescent lamps. It was pointed out by Mr. Huse that
one of the important functions of the Society was the contact it
afforded between the industry and the many research organizations
whose work so materially affected the progress of the motion picture
industry. Mr. Huse introduced Mr. Ralph Farnham of the General
Electric Company.
Mr. Farnham reviewed the character of the emission of luminous
bodies in general and of the tungsten filament in particular. The
various zones in which the energy was of photographic value or heat
value were explained with curves and diagrams. From this Mr.
Farnham discussed the various methods of screening out the heat
zone and reviewed the materials best suited for this purpose. It was
shown that a layer of distilled water in the path of the beam removed
most of the heat. This was accompanied by a demonstration with
two eighteen inch spot lamps equipped with five-thousand watt
bulbs. One of the lamps was equipped with a water filter while one
was open. Beams from the two lamps were projected on the audience.
Mr. Farnham concluded his talk with a brief period of questions from
the floor that elicited many interesting points of view.
466 REPORT OF* THE SECRETARY fj. s. M. P.
Mr. Huse then made some brief comments on the feature subject
of the evening, Wide Film, followed by statements of the manufacturing
problems involved in producing wider film. These comments were
followed by brief remarks from Mr. Rhody, covering some of the
optical problems that had been raised by the use of wide film. Mr.
Huse then introduced Mr. George Mitchell, Chief Engineer of the
Mitchell Camera Corporation.
Mr. Mitchell had prepared an excellent group of exhibits of the
various parts of the Grandeur camera together with completely
assembled units. These he reviewed, pointing out the differences
between these and the better known thirty-five millimeter cameras.
His discussion was quite complete as well as interesting and was
followed by an open forum of questions that elicited discussions from
the floor on photography, projection, illumination, optics, picture
proportion, etc.
At the conclusion of the open forum the speakers were thanked
and the meeting was invited to inspect the plant which represents one
of the most complete examples of modern engineering in the motion
picture industry. G. F. RACKETT, Secretary
REPORT OF THE SECRETARY*
This report summarizes briefly some of the items which will be of
interest to the membership regarding the conduct of the office of
Secretary for 1928 to 1929.
The past year has been a record year for the Society. It saw the
formation of the London Section and witnessed a decided increase in
our German and French membership, with a substantial growth of
American membership. Our growth in membership is indicative of
the increased new work carried on by the Society in every field. In
order to meet these new conditions, the Board of Governors appointed
early last year an Assistant to the Secretary and Treasurer, who was
to cooperate with other officers and committee chairmen as much as
possible. Miss Renwick took this position the first week in January
and has done much to keep the work of the Secretary's office up
to date. Since the Secretary's office is a clearing house for a great
many of the Society's matters, there is necessarily considerable de-
tail work required. No further mention will be made of this par-
* October 1, 1928, to October 1, 1929.
April, 1930] REPORT OF THE SECRETARY 467
ticular phase of the work, but attention will now be given to items
more pertinent to the membership.
MEMBERSHIP
Mr. Cowling, the very active Chairman of the Membership Com-
mittee, has added many new names to the Society rolls. The present
roll of the Society is 611 members, which represents an increase of
313 new members for the year! The total enrollment is divided as
follows: 5 Honorary members, 326 Active members, and 280 Asso-
ciate members. Seven members have resigned from the Society
during the past year, and 18 have been dropped from the rolls. Six
Associate members have been transferred to Active membership.
Twenty-five applications are now pending action. Of these, 11 await
approval by the Board, and 14 are held up for entrance fee.
The Pacific Coast Section, which includes Los Angeles, Hollywood,
San Francisco, and Washington, shows a total of 74 members. The
London Section which was organized last year has increased during
the year to 90 members, and is very active, holding meetings regularly
once a month during the winter season.
The total Society membership as distributed over the United States
or in foreign countries is as follows:
New York and East 303
Chicago and Mid-West 82
Pacific Coast 74
British Isles 90
Canada 15
France 14
Germany 15
India 6
Italy 3
Russia 2
Australia 2
Japan 2
Switzerland 1
Sweden 1
Holland 1
Total 611
TRANSACTIONS
One thousand, three hundred and thirty-one (1331) Transactions
since October 1, 1928, have been mailed out by the Secretary.
Over $3000 has been received in payment for these Transactions.
468 SPRING MEETING [j. s. M. P E.
Our Transactions went to many foreign countries; approximately
one-fourth of the Transactions distributed from this office have gone
to non-members in foreign countries.
PRINTING AND STATIONERY
In order to insure that stationery of uniform quality is used, and
that printed matter is handled through a central source, practically
all requirements along this line have been taken care of by the
Secretary. On the whole, this scheme has worked out well. The
Secretary has taken care of all printed matter circularized to the
members during the past six months. In addition, the publication
of the Bulletin was taken over for this six-months' period. Two
issues, one in June and one in September, have been prepared and
mailed to the membership.
Assistance has been given to other officers and committee chairmen
in preparing mailing material and in the furnishing of addressed
envelopes.
CONCLUSION
As a result of my year's experience as Secretary, it is evident to
me that there are many opportunities for further centralization of
the Society's activities and coordination of effort through the Secre-
tary's office. However, in view of the fact that the publishing of
a journal is under immediate consideration, it does not seem ad-
visable to make recommendations at the present time. Undoubtedly
much routine work now handled by the Secretary will be taken
care of by the office conducting this JOURNAL. Details of coor-
dination and centralization under these new conditions will require
careful consideration and will have to be worked out by the manager
conducting the JOURNAL.
Respectfully submitted,
R. S. BURNAP, Secretary
SPRING MEETING OF THE SOCIETY, WASHINGTON, D. C.
(May 5th to 8th, inclusive)
Arrangements for the Spring meeting of the Society to be held at
the Wardman Park Hotel, Washington, D. C., have been announced
by the Chairman of the Convention Committee, Mr. W. C. Kunz-
mann.
April, 1930] SPRING MEETING 469
The Committee has the following tentative program under con-
sideration.
Monday, May 5th
Convention Registration, 8:30 to 10:00 A.M.
Convention called to order, 10: 00 A.M., Little Theater, Wardman
Park Hotel
Address of Welcome
Response by President J. I. Crab tree
Report of the Convention Committee, W. C. Kunzmann
.Report of the Secretary, J. H. Kurlander
Report of the Treasurer, William C. Hubbard
Committee Reports and Papers Presentation
12:30 to 1:30 P.M. Luncheon
2:00 P.M. Little Theater, Wardman Park Hotel
Presentation of Papers
Monday Evening, May 5th, 7:30 P. M.
Get together party, and exhibition of a selected film program
Tuesday, May 6th
8:30 to 9:30 A.M. Registration
9:30 A.M. Presentation of Papers, Little Theater, Wardman Park
Hotel
12:30 to 1:30 P.M. Luncheon
2:00 P.M. Presentation of Papers, Little Theater, Wardman Park
Hotel
Tuesday Evening
Entertainment under consideration
Wednesday, May 7th
9:30 A.M. Presentation of Papers, Little Theater, Wardman Park
Hotel
12:30 to 1:30 P.M. Luncheon
2:00 P.M. Contemplated bus ride and sightseeing trip to Mt.
Vernon, Va., and visit to the White House
Wednesday Evening, 7:00 P. M.
Semi-annual banquet in the Gold Room of the Wardman Park
Hotel
Speakers for the evening to be announced later
Dancing and elaborate program of entertainment
470 SPRING MEETING [j. s. M. p. E.
Thursday, May 8th
9:30 A.M. Presentation of Papers, Little Theater, Wardman Park
Hotel
12:30 to 1:30 P.M. Luncheon
2:00 P.M. Presentation of Papers, Little Theater, Wardman Park
Hotel
Open Forum
Convention Committee report and discussion of place and plans for
the Fall Convention
Adjournment
The following committees and individuals will officiate during the
convention:
Reception Committee
WVC. HUBBARD C. FRANCIS JENKINS W. C. KUNZMANN
J. W. COFFMAN H. T. COWUNG M. W. PALMER
N. D. GOLDEN RAYMOND EVANS C. J. NORTH
W. WHITMORE LT.-COL. WALTER E. PROSSER
Convention Registrars
W. C. KUNZMANN C. RENWICK
K. C. D. HICKMANN E. R. GEIB
Hostess to Convention
MRS. WALTER E. PROSSER, assisted by
MRS. C. FRANCIS JENKINS MRS. N. D. GOLDEN MRS. C. J. NORTH
Banquet Arrangements
W. C. HUBBARD
Banquet Master of Ceremonies
HON. CONGRESSMAN W. B. CONNERY, JR., 7th District, Massachusetts
Floor Show Entertainment
HARDIE MEAKIN, Washington Representative "Variety"
Supervision Projection Equipment
Installation and Operation
H. B. SANTEE M. C. BATSEL H. GRIFFIN
F. J. STORTY PAUL R. HEYL
April, 1930] INFORMATION FOR AUTHORS 471
Entertainment and Amusements
C. FRANCIS JENKINS N. D. GOLDEN NAT GLASSER
RAYMOND EVANS K. C. D. HICKMANN F. J. STORTY
L/r.-CoL. WALTER E. PROSSER
Press and Publicity
W. WHITMORE G. E. MATTHEWS F. C. BADGLEY
Transportation, Bulletins, and Reservations
P. A. McGuiRE N. D. GOLDEN
Convention Official Photographers
J. T. FLANAGAN RAYMOND EVANS
Convention Announcements
MEMBERS RECEPTION COMMITTEE
INFORMATION FOR AUTHORS CONCERNING
PUBLICATION IN THE JOURNAL
JOURNAL ADMINISTRATION
Certain rules and regulations pertaining to the publication of the
JOURNAL OF THE SOCIETY OF MOTION PICTURE ENGINEERS have been
adopted. It is desirable that members of the Society and contribu-
tors to the convention programs and to the JOURNAL should be fa-
miliar with these regulations. We shall attempt therefore at this
time to explain certain phases of the JOURNAL administration. It is
hoped that all contributors will strive to cooperate with the editorial
office to the end that the affairs of the JOURNAL shall run smoothly
and that a publication of maximum usefulness and highest quality
shall be created.
PRIOR RIGHT TO PUBLICATION OF CONVENTION PAPERS
There has been some uncertainty and misunderstanding in the
past, relative to the Society's attitude toward the publication of pa-
pers which are read at our semi-annual conventions. At a recent
meeting of the Board of Governors a definite action designed to
clarify this was taken. The motion passed at that time is as follows:
"Papers presented at regular meetings shall 'not be published or
circulated, and shall be considered as the confidential property of the
Society, prior to their appearance in the JOURNAL, except that in case
472 INFORMATION FOR AUTHORS [j. s. M. p. E.
such paper is not published in the JOURNAL within six months after
its presentation, the author is free to use it in whatever manner he
sees fit." This action definitely establishes the prior claim of the
Society to any paper which a contributor may present at the Society's
semi-annual meetings. This position which has been adopted by the
Society of Motion Picture Engineers is the same as that taken by
many other similar technical organizations. It seems only reason-
able that, if the Society grants the privilege of the floor to any con-
tributor for the presentation of a paper on the program of its meeting,
it is only fair that the Society shall have a prior right to the publica-
tion of that material. It is recognized, of course, that in asking this
privilege the Society should assure the contributor reasonably prompt
publication. While we were publishing our convention programs in
the form of transactions it was not possible to assure prompt publica-
tion, but now that the JOURNAL is operating successfully we should
have little difficulty in meeting reasonable demands of contributors
for promptness of publication.
ORDER OF PUBLICATION
The material presented at one of our semi-annual conventions is
obviously much more voluminous than can be published in one of the
monthly issues of the JOURNAL. In fact, the material from one con-
vention, assuming an average number of papers, should be adequate
to fill at least four monthly issues. We are faced, therefore, with the
problem of order of publication and it is obvious that some papers
will appear at a materially earlier date than others. A consideration
of the general types of papers which are read at conventions indicates
that there are some which should be published very promptly, while
others may reasonably be held up for two or three months without any
serious depreciation in value. Of the latter type are those which
may be referred to as tutorial and those which aim to summarize the
status of some particular phase of technology. Papers dealing with
new developments and things of vital interest, of course, should be
published as promptly as possible. Authors desiring immediate
publication should notify the editor of the JOURNAL to this effect.
Such requests will be given every possible consideration. It is
possible, of course, that the attempt to take care of this order of
publication by granting requests of authors may lead the editorial
office into difficulty. For instance, all authors may request prompt
publication. Obviously under such conditions some mechanism
April, 1930] INFORMATION FOR AUTHORS 473
must be adopted for determining the order in which papers presented
at our semi-annual conventions shall be published. The authority
to decide upon order of publication must, of course, reside in some
particular individual or committee. At the recent meeting of the
Board of Governors the following instructions were given to the editor
of the JOURNAL: "The order of publication of papers in the JOURNAL
is placed within the discretion of the editor. In case special and early
publication is desired, papers will preferably be published in the order
of receipt by the editorial office, of a complete manuscript for print-
ing."
In view of these instructions from the Board of Governors, the
editorial office proposes to determine in general the order in which
papers are published by the chronological order in which manu-
scripts are received at the editorial office. We wish to emphasize
that any author desiring early publication of his article should submit
a manuscript complete with all drawings, diagrams, etc., at the
earliest possible moment. Upon receipt at the editorial office these
will be date stamped. The course which an author should follow
in order to obtain early publication is therefore clearly denned and
we feel that little dissatisfaction can possibly result from delay in the
publication of papers depending for their greatest value upon im-
mediate publication. This regulation, it is hoped, will stimulate
contributors to exercise the utmost care in the preparation of manu-
scripts which are submitted, and the editorial office will consider that
the necessity of returning a manuscript to the author for revision
or correction or the provision of more satisfactory drawings will be
sufficient reason to invalidate his precedence date and the date which
will be effective in determining the order of publication will be that
upon which the corrected manuscript is received again at the edi-
torial office.
In dealing with those papers for which no particular request for
promptness is made the editor will use his best judgment in arranging
them so as to give JOURNAL issues of maximum interest to a maximum
number of readers. The present editorial management does not
feel particularly disposed to allotting some particular JOURNAL to a
definite group of papers dealing with a specific subject. We feel
that in general this does not serve to keep alive the interest of the
maximum number of readers in all of the JOURNAL issues. In our
opinion a JOURNAL carrying papers of a diversified type, all, of course,
bearing on the motion picture industry, is more desirable.
474 INFORMATION FOR AUTHORS [J. S. M. p. E
DATE OF RECEIPT OF MATERIAL RELATIVE TO THE PUBLICATION DATE
Material for the technical section of the JOURNAL, must be in the
hands of the editor not later than the 20th of the second month
preceding the date of issue. This deadline date applies also to any
other material for which the author desires to see galley proof.
For example, any material of a technical nature which is to appear
in the July issue of the JOURNAL, must be mailed early enough to be
received by the editor by the 20th of May.
Abstracts, reviews, and material of a strictly news nature must be
received by the editor not later than the 7th of the month preceding
the date of issue. No proof will be submitted to authors for material
of this class. For example, all material in this class to be included
in the July issue must be received by the editor by the 7th of June.
STANDARDIZATION OF USAGE FOR THE JOURNAL
It seems desirable to establish a style as to typography, form, and
spelling which will be consistent from issue to issue. The vocabulary
and forms of expression of the motion picture engineer are specialized
to such an extent that there is no inclusive published compendium
of terms to which one can refer. We believe one of the services
which the JOURNAL, can render to the industry is in the standardiza-
tion of verbal usage.
Authors of papers can assist the editorial office to a great extent by
conforming to the suggestions which follow. We wish it under-
stood, however, that this office will welcome criticism of any of the
items presented. We shall be glad to have brought to our attention
additional matters of verbal usage which seem to demand standardiza-
tion through the pages of the JOURNAL.
MECHANICAL FORM OF THE MANUSCRIPT
Text. Papers should always be typewritten on only one side of the
paper. It is desirable to send for publication the original (ribbon
copy) a carbon copy is easily erased and may become illegible.
Double spacing should be used so as to provide space for interlined
editorial correction.
Illustrations. Each drawing or photograph should occupy a
separate sheet and must be of a type which will reproduce well.
Blueprints, photostats, or sepia prints cannot be accepted. Tracings
or line drawings should be made with black india ink on white paper
or tracing cloth. Closely spaced coordinate lines on curves should be
avoided.
April, 1930] INFORMATION FOR AUTHORS 475
The minimum amount of reading matter should be included on the
illustrations. Necessary information can better be set in type in a
caption accompanying the illustration.
The maximum width of a JOURNAL cut is 4 inches and the maximum
length is 6 l /t inches. It is important to make sure that the necessary
reduction in magnification of an illustration will not make the
height of letters contained in reading matter on the illustration less
than Vs2 inch.
Listing of Captions. Captions for all figures and tables should be
listed on separate sheets accompanying the manuscript.
Address. It is important that the author's mailing address shall
be written on the first page of the manuscript. His business affilia-
tion should also be mentioned. The editorial office should be kept
informed of changes in the author's address in order that proof may
reach him promptly.
PRINTING STYLE (HEADINGS)
Although the general make-up of the JOURNAL is still in the state
of evolution, certain points of typographic style are rather definitely
established. In the setting of this style, it was attempted to provide
a flexible form. It is suggested that the author make extensive use
of the possibilities of this established form.
It undoubtedly increases the value and clarity of a paper for it to
be definitely divided into sections. It would assist the editorial
office for the author to specify which type of heading or subheading
is desired in each instance. The headings conforming to JOURNAL
style, in descending order of importance are as follows:
CENTERHEAD
Italic Centerhead
Italic Sidehead. These sideheads are run in to the text of the para-
graph.
BIBLIOGRAPHY AND FOOTNOTES
References to literature should be accurate and complete. A mere
listing of titles uncritically made is worse than no bibliography at all.
For the author to save himself a few minutes by omitting any item
of the reference appears almost criminal when one considers the total
amount of time needlessly wasted by the many readers.
References to periodical literature should contain the following
items in the given order:
1 . The reference number which corresponds to the number in the
text.
476 INFORMATION FOR AUTHORS [j. s. M. p. E.
2. The author of the paper correctly spelled and with initials.
3. The name of the article enclosed in quotation marks.
4. The name of the periodical (unless the periodical is a common
one its title should not be abbreviated) .
5. The volume number.
6. The date month and year enclosed in parentheses.
7. The serial number preceded by the abbreviation "No."
8. The page number preceded by the letter ' 'p. "
Example. l McCov, J. L.: "A Light Intensity Meter." J. Soc.
Mot. Pict. Eng., XIV (March, 1930), No. 3, p. 357.
References to books should be made as follows:
1. Author's name.
2. Name of book enclosed in quotation marks.
3. Edition.
4. Publisher.
5. Place of publication.
6. Date of publication enclosed in parentheses.
7. Page preceded by letter "p."
Example. FRANKUN, H. B.: "Sound Motion Pictures." 1st ed.
Doubleday, Doran & Co., Garden City, L. I., N. Y. (1929), p. 101.
SPELLING
Usages and preferred spelling forms as given in the Standard Dic-
tionary will be followed in general. The appended list of spelling
forms contains some exceptions which have been tentatively adopted
as JOURNAL style.
It is very desirable that authors follow these forms of spelling and
usage in the drawing of figures.
all-sound diaphragm
all-talking disk
aluminum etc.
astrogamma //1 .9 (referring to aperture)
abscissas (not ae) formulas (not ae)
"B" battery fade-in
back-focus fade-out
cut-back (noun) feedback
cut-in (noun) indexes (not indices)
change-over infra-red
close-up mediums (not a)
April, 1930] INFORMATION FOR AUTHORS 477
microns (not a) technic
pickup time-lapse
pull-down (noun) through
photo-electric though
photo-cell theater
play-backs (noun) two-color
sound-on-disk (adjective) three-color
sound-on-film (adjective) ultra-violet
sound-proof ultra-speed
sulfur X-ray
super-speed
ABBREVIATIONS
alternating current
a.c.
ampere
amp.
British thermal unit
Btu.
candle power
cp.
centimeter
cm.
centigrade
C.
cosine
cos
cubic centimeter
cc.
decibel
db.
diameter
spell out
direct current
d.c.
electromotive force
emf.
Fahrenheit
F.
feet
ft.
gram
spell out
inch or inches
in.
kilocycles
spell out
kilowatts
kw.
Kelvin
K.
lambert
L.
lumen
1.
lumens per watt
Ipw.
megohm
spell out
meter
m.
millimeter
mm.
microfarad
juf.
millivolt
mv.
ounce
oz.
478 INFORMATION FOR AUTHORS
per write out
revolutions per minute rpm.
secant sec
second sec.
sine sin
square root of mean square rms.
tangent tan
watts per candle wpc.
MISCELLANEOUS ITEMS CONCERNING JOURNAL STYLE
Papers should preferably be written from the impersonal point of
view. For example, it is preferable to write:
"The amplitude is varied by the use of the potentiometer " rather
than "you vary the amplitude " or "I vary the amplitude ."
The indefinite use of "we" except in papers by joint authors should
be avoided.
Long introductions not dealing specifically with the subject of the
paper should be avoided.
Capitalize significant parts in the names of a manufactured prod-
uct, i. e., Ivory soap.
Verify the spelling of all proper nouns.
In using numbers, spell out the following:
1. Numbers at the beginning of a sentence.
2. Numbers indicating length of time (i. e., for thirty minutes).
3. Ordinal numbers (i. e., eighth foot, tenth day).
4. Common fractions (three-fourths, half, etc.) if easily expressed
in words.
5. Numbers in reading matter of less than three digits.
Use figures for:
1. Numbers of three or more digits except at the beginning of a
sentence.
2. Temperatures, weights, lengths, areas, capacities, percentages,
ratios, etc.
3. Dates either in ordinal or cardinal style (i. e., July 15, 1920) or
(on the 15th of July).
4. Cardinal numbers indicating serial position (i. e., page 321,
Fig.5,efc.).
5. Sums of money.
Membership
in the
Society of Motion
Picture Engineers
is open to all who are engaged
in any branch of the motion
picture industry or allied
work. The society is inter-
national in character and its
convention papers with com-
plete discussions are furnished
free to members.
REASONS WHY
YOU
SHOULD JOIN
The Society of
Motion Picture
Engineers
1 The S. M. P. E. is an internation-
ally recognized organisation of
Motion Picture Engineers.
2 The S. M. P. E. is becoming an
ever more important factor in de-
veloping, stabilizing, and standard-
izing the motion picture industry.
3 At two conventions each year reli-
able data concerning a wide range
of subjects are presented long be-
fore they become available else-
where.
4 Papers read at conventions are
printed with full discussions in
a monthly Journal and distributed
free to all members.
5 The S. M. P. E. affords unique op-
portunities for personal contact
with leaders in the industry.
6 S. M. P. E. publications are recog-
nized standard authority on Mo-
tion Picture Engineering.
7 The S. M. P. E. will help you in
many ways. Join now.
COUPON
HERFORD TYNES COWLING, Chairman
Membership Committee, Society of Motion Picture Engineers
343 State Street, Rochester, N. Y.
Dear Sir
Please mail application blank and requirements for membership in the S. M. P. E. to-
Name.
(Please print)
Position.
(Company or other Affiliation)
Street and City Address
Name
Position
Street and City Address.
JOURNAL
OF THE SOCIETY OF
MOTION PICTURE ENGINEERS
LOYD A. JONES, EDITOR pro tern.
Volume XIV MAY, 1930 Number 5
CONTENTS
Page
Some Properties of Chrome Alum Stop Baths and Fixing Baths
(Part I) J. I. CRABTREE AND H. D. RUSSELI, 483
Sound Films for Surgical Instruction P. E. TRUESDALE 513
Some Aspects of a Western Electric Sound Recording System .
S. S. A. WATKINS AND C. H. FETTER 520
Measuring the Effective Illumination of Photographic Objec-
tives J. HRDLICKA 531
Camera Mechanism, Ancient and Modern
ARTHUR S. NEWMAN 534
Standards Adopted by the Society of Motion Picture Engineers 545
Abstracts 567
Book Reviews 571
Officers 572
Committees 573
Annual Report of the Treasurer 578
London Section 579
New York Section 580
News Note from the National Society for the Prevention of
Blindness 581
Society Notes 582
List of Membership 585
JOURNAL
OF THE SOCIETY OF
MOTION PICTURE ENGINEERS
LOYD A. JONES, EDITOR pro tern.
Associate Editors
G. L. CHANIER P. Mous S. E. SHEPPARD
O. M. GLUNT W. B. RAYTON J. L. SPENCE
A. C. HARDY P. E. SABINE L. T. TROLAND
Publication Office, 20th & Northampton Sts., Easton, Pa.
Editorial Office, 343 State St., Rochester, N. Y.
Published Monthly
Copyrighted, 1930, by the Society of Motion Picture Engineers
Subscription to non-members $12.00 per year; single copies $1.50. Order from
the Secretary of the Society of Motion Picture Engineers, 20th and Northampton
Sts., Easton, Pa., or 2 Clearfield Ave., Bloomfield, N. J.
Papers or abstracts may be reprinted if credit is given to the Journal of the
Society of Motion Picture Engineers.
The Society is not responsible for statements made by authors.
Application pending for second-class entry at the Post Office at Easton, Pa.
SOME PROPERTIES OF CHROME ALUM STOP
BATHS AND FIXING BATHS (PART I)*
J. I. CRABTREE AND H. D. RUSSELL
INTRODUCTION
In a previous paper, the results of an extended investigation of
the properties of fixing baths compounded with potassium alum
were given. 1 In the present paper, the results of a similar study of
stop baths and fixing baths containing chrome alum will be outlined.
Chrome alum or chromium potassium sulfate, K 2 SO4, C^CSOOs'-
24H 2 O, was one of the first hardening agents used for tanning gelatin
and was referred to in practically all of the early literature on the
insolubilization of gelatin solutions by inorganic hardening agents.
Little or no reference was made to aluminum alum until the time of
Lainer 2 whose investigations made possible the addition of acids to a
solution of hypo without the precipitation of sulfur by utilizing the
protective action of alkaline sulfites. The first hardening baths
contained chrome alum together with sodium bisulfite and hypo,
while later Namias 3 used sodium acetate as an anti-sulfur protective
in place of the sodium bisulfite. Chrome alum in acid-sodium
sulfite-hypo fixing baths does not readily precipitate a sludge on the
addition of developer as is the case with a similar combination
with aluminum alum in the absence of suitable revival with acid and
this is undoubtedly the reason why aluminum alum was not more
generally used by the early workers. At the present time, chrome
alum baths are less extensively used than potassium alum baths
for normal temperature processing of motion picture film for the
following reasons:
(a) Chrome alum fixing baths tend to lose their hardening properties whether
or not they are used, especially when stored at high temperatures.
(6) The sludge which tends to form on the addition of an excess of developer
to most chrome alum hardening baths is very difficult to remove from the film
when it is precipitated thereon.
(c) At high temperatures chrome alum baths have a tendency to stain the
* Communication No. 432 from the Kodak Research Laboratories.
483
484 J. I. CRABTRKE AND H. D. RUSSELL [J. S. M. P. E.
gelatin film green, but at normal temperatures no staining occurs unless the bath
contains a high concentration of alum.
On the other hand, chrome alum baths possess the following ad-
vantages:
(a) Under suitable conditions, chrome alum has the property of rendering
gelatin insoluble in boiling water while in all of the cases investigated in which
aluminum alum was the hardening agent, it was impossible to obtain a gelatin
film which would not melt at 212F. with prolonged treatment. Chrome alum
baths are therefore particularly suitable for processing at high temperatures.
(fc) Chrome alum is more efficient with regard to the quantity of alum re-
quired to produce a given degree of hardening. Lumiere and Seyewetz 4 found
that 0.5 per cent of chrome alum in a 15 per cent solution of hypo produced the
same degree of hardening as 1.5 per cent of aluminum alum in a similar solution.
In order to determine more precisely the relative merits of chrome
alum as compared with aluminum alum as a hardening agent for use
with motion picture film, an extended investigation of the properties
of chrome alum stop bath and fixing bath formulas seemed justified.
PART I CHROME ALUM STOP BATHS
The Function of a Stop Bath. During the development of photo-
graphic emulsions the gelatin is rendered alkaline by the carbonate
or alkali in the developer. Part of this alkali may be removed from
the film by rinsing in water between development and fixation but
the gelatin still contains an appreciable quantity of alkali when
the film is placed in the fixing bath, depending on the duration of the
rinse. As previously shown, 1 an excess of alkali destroys the harden-
ing properties of a potassium alum fixing bath and tends to cause the
formation of a precipitate of aluminum sulfite, thus rendering the
bath unsatisfactory for further use. It is possible to prevent en-
tirely the carrying over of alkali into the fixing bath by immersing
the film in an acid solution termed a "short stop" or "acid stop"
bath after developing and before fixing. If the stop bath contains
hardening ingredients it is then possible to dispense with a hardening
fixing bath and use a plain acid hypo solution for fixing purposes.
Stop baths are very necessary with certain types of motion picture
film processing machines where the film is exposed to the air for
several seconds in passing from the developer to the fixing bath.
The stop bath not only arrests development immediately and pre-
vents the possible formation of aerial fog and developer stain but
likewise prevents sludging of the fixing bath.
May, 1930] STOP BATHS AND FlXING BATHS 485
When considering the advisability of using an acid hardening
stop bath, the efficiency of the processing must be considered in
terms of the total time required to develop, harden, and fix a given
film, that is, in the case of a hardening fixing bath, the film is hard-
ened and fixed simultaneously, while in the case of a hardening stop
bath used in conjunction with a non-hardening fixing bath, hardening
and fixing are independent. It is therefore evident that the use of
a hardening stop bath increases the time required for processing a
given film and for this reason the hardening fixing bath is most
desirable under normal conditions because of the time saved.
Desirable Properties of Stop Baths. (a) The bath must be
distinctly acid and to be efficient should remain acid during the life
of the fixing bath. Although the stop bath should be sufficiently
acid to insure long life, when the film leaves the bath it is more or
less acid and will therefore increase the free acid content of the
fixing bath which in turn will increase the tendency of the latter
to sulfurize. The choice of acids therefore depends on the pro-
pensity of the acid to precipitate sulfur in a hypo solution.
(b) A stop bath should not be sufficiently acid to cause blisters,
and the limit of acidity in this case is much less than in the case of a
fixing bath because the alkalinity of the film is much greater when
removed from the developer than after a slight rinse and previous to
immersion in the fixing bath.
(c) A hardening stop bath should have properties similar to those
of a plain acid stop bath and in addition should produce satisfactory
hardening throughout its life. Since the hardening produced by
alum mixtures varies with the quantity of developer or alkali added,
it is apparent that an acid hardening stop bath will not produce
uniform hardening except for a limited time unless it is suitably
revived.
Choice of Acids and Hardening Agents for Use in Stop Baths.
Since the acid contained in the stop bath is carried into the fixing
bath, it is important that the acid should have properties similar
to those of the acid used in the fixing bath, that is, it should have
the least possible tendency to precipitate sulfur with hypo and
should not produce blisters readily. Solid organic acids, such as
citric, tartaric, malic, and maleic, are not suitable because they
decrease the hardening properties of a fixing bath by virtue of the
formation of non-hardening complexes. At the present time, acetic
486 J. I. CRABTREE AND H. D. RUSSELL [J. S. M. p. E.
acid appears to be the most suitable available acid for non-hardening
baths because it does not materially affect the hardening properties
of a potassium alum fixing bath and has a minimum tendency to
precipitate sulfur therein. Of the common acid salts which can be
used for this purpose, sodium bisulfite is perhaps the most suitable
since it does not impair the properties of the fixing bath and, so far
as is known, will not blister the film under normal conditions.
Of the available hardening agents for use in acid hardening stop
baths, chrome alum was considered the most promising because
it is capable of producing a greater degree of hardening than po-
tassium alum and is therefore suitable for use at high temperatures,
under which conditions the use of a hardening stop bath is usually
desirable. Both acetic and sulfuric acids were tested to determine
their suitability for use in acid hardening baths.
Hardening Action of Chrome Alum Solutions. In the preliminary
experiments, the hardening action of chrome alum solutions on both
neutral and alkaline film was investigated. The most alkaline
film met with in actual practice was that placed directly from the
developer into the stop bath without rinsing. The neutral film was
rinsed for fifteen minutes after development and before placing in the
chrome alum bath, which rendered it less alkaline than any met
with in actual practice. In making the hardening tests, strips of
motion picture positive film were developed for five minutes in D-16*
at 70F., rinsed for fifteen minutes (neutral film) and then agitated
in the chrome alum bath every thirty seconds for three minutes.
For the alkaline film tests the rinse was omitted. On leaving the
bath, the film was again rinsed for fifteen minutes, fixed in a plain
30 per cent hypo solution for five minutes, washed for twenty minutes,
and the hardening determined as in the case of fixing baths. 1 The
acidity of the solution was determined in the following manner:
* Formula
D-16
Metric
Avoirdupois
Elon
0.3 gram
2 ounces
Sodium sulfite (desiccated)
40 . grams
16 x /2 pounds
Hydroquinone
6 . grams
2*/2 pounds
Sodium carbonate (desiccated)
19.0 grams
7 3 /4 pounds
Potassium bromide
. 9 gram
5 8 /4 ounces
Citric acid
0.7 gram
4Y 2 ounces
Potassium metabisulfite
1 . 5 grams
10 ounces
Water to make
1 liter
50 gallons
Average time of development: 5 to 10 minutes at 65 F. (18 C.).
,
,
May, 1930] STOP BATHS AND FIXING BATHS 487
Acidity Measurements. The acidic properties of an acid solution
are attributable to the presence of free hydrogen ions. In a strongly
acid solution there are many more of these ions than in a weakly
acid solution so that the hydrogen ion concentration may be con-
sidered as a measure of the acidity of the solution. Acidity is usually
expressed by the symbol "pH" which is equal to the logarithm of
the reciprocal of the hydrogen ion concentration or pH = log H ion CQnc
An alkaline solution has therefore a relatively high pH value as
compared with an acid solution.
In the present investigation, the pH or the acidity of the various
chrome alum solutions was determined by the colorimetric method
which depends upon the fact that the color or light absorbing proper-
ties of solutions of certain organic compounds (indicators) vary
with their degree of acidity or alkalinity (hydrogen ion concentration).
For instance, methyl orange is yellow at pH values lower than 4
but the dye changes color to orange at a pH of 4.0. The indicator,
brom phenol blue, is yellow at a pH of 3.0 and purple at 4.6. At
intermediate pH values the dye has definite intermediate shades.
Therefore, by comparing the color of any solution with a set of
standards having known pH values, the pH value of the test solution
is obtained.
The indicator solution used in the present investigation was
made by dissolving 0.4 gram of brom phenol blue in 75 cc. of a
0.05 per cent solution of potassium hydroxide and adding enough
water to make one liter of solution.
Preliminary pH measurements were made with plain 2 per cent
chrome alum solutions containing increasing quantities of developer.
TABLE I. Effect of Acidity on Color of Indicator
Nature of Solution
Color
PH
2% Chrome alum
Reddish yellow
3.2
2% Chrome alum +
4%D-16
Bluish red
4.0*
2% Chrome alum +
7% D-16
Purple
4.6*
Two cc. of each solution were added to 5 cc. of distilled water con-
taining 10 drops of the indicator solution. These solutions were
placed in test tubes of equal diameter and then arranged in a single
line in a rack before an illuminator containing a tungsten bulb
488 J. I. CRABTREE AND H. D. RUSSBU, [J. S. M. p. E.
screened to the color of noonday sun with a No. 79 Wratten filter.
A comparison between the color of each solution gave a relative
measure of the acidity of the solutions. The color change observed
with brom phenol blue under these conditions is indicated in Table I.
The pH values bearing asterisks were checked with other indicators
such as methyl orange (pH range 2.9-4.0), methyl red (pH range
4.2-6.4), and brom cresol purple (pH range 5.2-6.8). The pH
values between these points were estimated by judgment.
This colorimetric method gives relative pH values which are
sufficiently accurate for practical purposes. Blectrometric methods
were not used because they did not give satisfactory results in the
presence of sodium sulfite.
Effect of Acidity on the Hardening Action of Chrome Alum Solu-
tions. Using the above procedure, the effect of concentration and
the acidity on the hardening properties of plain chrome alum stop
baths was determined. The results are indicated in Fig. 1 from
which it is seen (curve A) that for neutral film the hardening in-
creases to a maximum at a concentration of 0.2 per cent and then
decreases rapidly as the concentration of chrome alum increases.
For alkaline film the hardening does not reach a maximum until a
concentration of 0.4 per cent is reached and then it remains at a
maximum throughout the range of concentrations tested. In view
of the fact that melting points above 212F. were not determined,
it cannot truthfully be said that the hardening reaches a maximum
if the film does not melt at 212F. For the purpose of this investi-
gation, however, it was considered unnecessary to make melting
points in water under pressure.
The acidity of the solutions indicated in curve B by pH values
was measured in the manner outlined above. Curve B shows that
for maximum hardening the acidity of the bath for neutral film
should be about a pH of 4.0 and that for alkaline film between
3.8 and 3.0. The degree of hardening observed in curve C was
obtained after the acidity of the baths had been so adjusted by
adding either sulfuric acid or caustic soda. For neutral film the
pH was 4.0 and for alkaline film, 3.2. It is seen that when the acidity
is adjusted to these values, the hardening properties of the baths
are constant, irrespective of the concentration of the chrome alum.
The inaccuracy of judging the acidity of the solutions with pH
indicators and the extreme change in hardening properties resulting
from slight changes in the acidity of the solutions accounts for the
May, 1930]
STOP BATHS AND FIXING BATHS
slight variations in the hardening properties of these adjusted solu-
tions.
A comparison of curves A and C (Fig. 1) indicates that the harden-
ing effect of a plain chrome alum solution depends largely upon its
acidity and for a constant acidity is independent of the concentration.
A. and L. Lumiere and Seyewetz, 4 Namias, 5 and a large number of
workers on the chrome tanning of leather have also observed this
fact.
The difference between the hardening of neutral and alkaline
IT 210
o
no
30
4
210
170
D-Ub -TO*F
AV_KA\_\NEL FIL.M
NEIUTRAX- F\\_f\
FlG. 1.
MELTING, POINTS FRE1SH SOLUTION
AC1PITV
pH. 4.O
MELTING PO\NTS AFTER AttJUSTlNG ACIDITY
/o CHgQMEL AUV3M
1.0
Z.O
3.O
4.0
Effect of concentration of a chrome alum solution on its hardening
properties.
film produced by a chrome alum stop bath may be readily explained
from a consideration of the effect of the addition of developer on the
hardening properties of an alum solution as discussed in a previous
paper. 1 It was shown that an excess of acid decreased the hardening
properties of a fixing bath while the addition of developer to a fixing
bath containing an excess of acid increased the hardening properties
to a maximum and with the addition of an excess quantity of de-
veloper the hardening was destroyed.
In a 1 per cent chrome alum stop bath, for example, which con-
tains no sodium sulfite or other acid buffering material we have a
490
J. I. CRABTREE AND H. D. RUSSEU, [J. S. M. p. E.
similar case in which the acid content is distinctly above the normal
limits permissible for satisfactory hardening of neutral gelatin.
If a developed film containing appreciable quantities of developer
is plunged immediately into the stop bath, the above conditions
are reproduced in situ within the film and the solution immediately
adjacent to it, that is, the developer locally neutralizes the excess
acidity of the stop bath so that the chrome alum is then rendered
capable of hardening the gelatin. In other words, the alkali held
in the gelatin and on the surface of the film creates a local condition
170
130-
90
NEUTRAL. FIL.M
xjx FRELSH
MEH_TING POINTS
1.0 .0 3.0 4.0
FIG. 2. Effect of the addition of sodium sulfite on the hardening properties
of a 2 per cent chrome alum stop bath containing 1 cc. of sulfuric acid per liter.
in the stop bath as represented by the addition of a sufficient quan-
tity of developer to the stop bath to produce maximum hardening
as in the case of adding developer to a hardening fixing bath. Once
the film is hardened and the alkali is neutralized by the acid, the
excess free acid in the stop bath does not destroy the hardening
already produced, because the acid content is relatively low and
the chrome alum hardening is not readily affected by weakly acid
solutions.
Eject of the Addition of Sodium Sulfite on the Hardening Properties
of a Chrome Alum Stop Bath. The effect of varying the concentration
of sodium sulfite on the hardening properties of a stop bath con-
May, 1930] STOP BATHS AND FlXING BATHS 491
taining 0.1 per cent sulfuric acid and 2 per cent chrome alum was
determined, using the same procedure as above for neutral film.
From Fig. 2 it is seen that as the concentration of sodium sulfite
increases, the acidity decreases and the hardening effect increases.
On standing for three weeks, a decrease in hardening occurred due
to an increase in acidity of the solution. From curves A and B
it is seen that maximum hardening is obtained when the solution has
a pH of 4.0 on ageing. Curve C was obtained by adjusting the acidity
of the solutions to a pH of 4.0 each time before measuring the harden-
ing. The results indicate that the hardening action is largely
dependent upon the acidity or pH value of the solution.
It was also noticed that on the addition of sodium sulfite to the
chrome alum solution the original violet color changed to a deep
green by transmitted light and it was considered that this color
change was correlated in some way to the decrease in the hardening
properties of the bath which resulted. From extensive tests, however,
it was concluded that the hardening properties were determined
largely by the degree of acidity or pH of the solution. This matter
will be discussed more fully in Part II of this paper.
Effect of Addition of MQ-25 Developer on the Hardening Properties
of Chrome Alum Stop Baths. To test further the factors favoring
the hardening action of chrome alum solutions, increasing quantities
of MQ-25 developer* were added to several stop bath formulas
and the hardening properties tested in the same manner as above
with neutral and alkaline film over a period of several days.
In the case of a plain 2 per cent chrome alum stop bath (Fig. 3)
the hardening properties with alkaline film and the acidity of the
solution decreased as the quantity of developer added increased.
A minimum degree of hardening was obtained with neutral film
in the plain solution but the hardening increased on the addition of
a small quantity of developer and then decreased as the proportion
*MQ-25 Developer
Metric Avoirdupois
Elon 1.25 grams 18 grains
Sodium sulfite (desiccated) 75.0 grams 2 ! /2 ounces
Hydroquinone 3.75 grams 54 grains
Sodium carbonate (desiccated) 25.0 grams 365 grains
Potassium bromide 1.5 grams 22 grains
Water to make 1 .0 liter 32 ounces
492
J. I. CRABTREE AND H. D. RUSSELL [J. S. M. P. E.
of developer increased. After the acidity was adjusted to a pH
of 3.2 for alkaline film and 4.0 for neutral film, the hardening proper-
ties were satisfactory. Age had little effect on the hardening proper-
2. 7<> CHROME: MJJM
X 70 N\C*. Z5
F\UV\ AUKAUNE. F\UA
HYPROXU7E.
90-
O ^> 10 5 \0
FIG. 3. Effect of the addition of MQ-25 developer on the hardening proper-
ties of a plain 2 per cent chrome alum stop bath.
ties of the solution in relation to alkaline film. The increase in
acidity on ageing of the solutions containing a small percentage of
developer accounts for the decrease in the hardening properties of
the solutions with neutral film.
May, 1930]
STOP BATHS AND FIXING BATHS
493
Effect of Addition of Acids to Hardening Stop Baths. It was con-
sidered that it might be possible to prolong the life of a plain 2 per
.070 CHROME. M.UM
0.*>7o /^CELTIC AGIO
*7o MQ. Z5
NEAJTRAA- FlV-t"V
FRELSH
90
\
i WE1E.KS
\
\
V
i^
"^
O 6 O 5 10
FIG. 4. Effect of the addition of MQ-25 developer on the hardening
properties of a 2 per cent chrome alum stop bath containing 5 cc. of acetic
acid per liter.
cent solution of chrome alum, particularly with respect to retarding
the formation of hydroxide sludge, by the addition of acids.
To date, sulfuric acid has been more commonly used than acetic
acid in chrome alum baths. From a consideration of the chemical
494
J. I. CRABTREE AND H. D. RUSSEU, [J. s. M. p. K.
properties of the two acids with respect to the photographic proper-
ties desired, acetic acid would appear more suitable because it is less
2.0 % CHROME. AL.UM
O.I 70 SULPHURIC AC\P
X 7* MQ. Z6
NEUTRAL.
AL.KM.INE1
o- -- O- -----
tJOQ o- o o
-g- -ff-^- 8
MELTING PO\NTS KFTE.R
MELTING, POINTS AFTER
O 6 10 O 5 10
FIG. 5. Effect of the addition of MQ-25 developer on the hardening
properties of a 2 per cent chrome alum stop bath containing 1 cc. of sulfuric
acid per liter..
dissociated and does not tend to precipitate sulfur from hypo as
readily as sulfuric acid. However, because of the prevailing prefer-
ence for sulfuric acid in chrome alum baths, the effect of both of the
above acids was determined.
May, 1930]
STOP BATHS AND FIXING BATHS
495
The effect of varying concentrations of MQ-25 developer on the
hardening properties of a stop bath containing (1) acetic acid and
7o CHROME ALUM
0.57. SULPHURIC
X 70 r^Q. 25
NEUTRKL F\LM
F\Lf\
MELTING, PO\NTS KFTER
MELTING POINTS AFTER
O ^) 10 O b \0
FIG. 6. Effect of the addition of MQ-25 developer on the hardening
properties of a 2 per cent chrome alum stop bath containing 5 cc. of sulfuric
acid per liter.
(2) sulfuric acid was therefore determined. The results are given
in Figs. 4, 5, and 6. From Fig. 4 it is seen that in the fresh bath
the hardening action produced with neutral film increased as the
496 J. I. CRABTREE AND H. D. RUSSELL [J. S. M. p. E.
quantity of developer added increased, while the hardening with
alkaline film decreased. The hardening properties, after standing
one day, were almost completely destroyed and were not revived
by an adjustment of the acidity with acetic acid. In view of these
facts, it was concluded that acetic acid was not satisfactory for use
in chrome alum stop baths.
The effect of the addition of sulfuric acid on the hardening proper-
ties of a 2 per cent chrome alum stop bath is shown in Figs. 5 and 6.
The hardening action produced with neutral film in a bath containing
0.1 per cent sulfuric acid (Fig. 5) increased and the acidity decreased
on the addition of developer. A maximum degree of hardening,
however, was produced with neutral film after the acidity of the solu-
tion was adjusted to a pH of 4.0. The age of the bath had no effect
on the hardening properties. Alkaline film was hardened to a
maximum degree, irrespective of the quantity of developer added up
to 10 per cent. In the case of the 0.5 per cent sulfuric acid stop
bath, the hardening action with alkaline film increased as the original
acidity decreased. After the bath was three weeks old, the harden-
ing behavior with alkaline film increased slightly. No appreciable
hardening was obtained with neutral film until the acidity was
adjusted to a pH of 4.0. A maximum degree of hardening was
produced with both neutral and alkaline film after the acidity of the
bath had been adjusted in this way.
From the results of these preliminary experiments recorded in
Figs. 1 to 6, it was concluded that: (1) the hardening properties of a
chrome alum stop bath are impaired by the presence of acetic acid,
developer, and sodium sulfite; (2) the addition of developer and
sodium sulfite decreases the acidity of the bath which usually de-
creases the hardening action; (3) the hardening properties of an
acetic acid-chrome alum bath containing developer are almost
completely destroyed after standing for one day, while baths con-
taining an equivalent quantity of sulfuric acid produce satisfactory
hardening on keeping; (4) the hardening properties of a plain 2
per cent chrome alum bath with the addition of developer over a
period of several days are better than those of a 2 per cent chrome
alum bath containing acetic acid; (5) sulfuric acid appears to be the
most suitable acid for use in chrome alum stop baths; (6) the degree
of hardening produced in a plain chrome alum bath or in a sulfuric
acid-chrome alum bath depends upon the acidity of the bath in
relation to that of the gelatin film, which is determined by the
May, 1930] STOP BATHS AND FIXING BATHS 497
quantity of developer retained by the film, the concentration of
alkali in the developer, and the hydrogen ion concentration of the
bath; (8) the hydrogen ion concentration of the bath must be
maintained between certain limits in order to obtain satisfactory
hardening properties; (9) a maximum degree of hardening is pro-
duced with neutral film when the acidity of the bath is maintained
between a pH of 3.8 and 4.2 and with alkaline film (as defined) when
the acidity lies between a pH of 3.0 and 4.0; (10) the concentration
of chrome alum and the age of a plain chrome alum bath containing
developer has but little effect on the hardening properties if the
acidity of the bath is maintained between the above limits by the
addition of sulfuric acid or caustic soda.
For practical purposes it was concluded that a 2 per cent chrome
alum solution is the best stop bath. In cases where dilute developer
is used and the alkalinity of the film is sufficiently low to reduce
to a minimum the tendency of the bath to blister, the addition of
0.1 per cent sulfuric acid is an advantage in increasing the developer
life of the bath, but it is not considered advisable to increase the
quantity of acid above this amount because of the accompanying
propensity of the bath to blister and to fail to harden weakly alkaline
film.
Fixing Baths for Use with Acid Stop Baths. Gelatin which has
been hardened in a suitable chrome alum stop bath is sufficiently
hardened to withstand wash water at relatively high temperatures
and therefore further hardening of the film in the fixing bath is not
necessary. However, a non-hardening fixing bath suitable for use
in conjunction with a chrome alum hardening stop bath should not
precipitate sulfur in the presence of an appreciable quantity (50
per cent) of stop bath since a relatively large quantity of acid is
continually being carried into the fixing bath. Therefore, the fixing
bath must contain an appreciable quantity of an anti-sulfur pro-
tective so as to prevent the precipitation of sulfur as the fixing bath
becomes exhausted and at the same time the chrome alum must not
precipitate as a sludge in the fixing bath.
Since sodium sulfite is the most efficient anti-sulfur protective,
experiments were made to determine the quantity of sodium sulfite
necessary to prevent the precipitation of sulfur from a 30 per cent
hypo solution containing 50 per cent of stop bath (a quantity of stop
bath which would normally be carried into the fixing bath). At
normal temperatures, sodium sulfite was found to be satisfactory
498 J. I. CRABTREE AND H. D. RUSSELL [J. S. M. p. E.
but on incubation a distinct gray-green precipitate occurred similar
to that formed in an aluminum alum fixing bath.
In further experiments it was found that 1 per cent sodium
sulfite together with 0.5 per cent sodium bisulfite prevented the
precipitation of both sulfur and the hardening agent from a 30 per
cent hypo solution containing 50 per cent of a 2 per cent solution of
chrome alum. Comparative experiments were made with a 2 per
cent chrome alum stop bath containing 0. 1 per cent sulf uric acid and
it was found that the increased acidity was not sufficient to cause
any material difference in the sulfurization life of the fixing bath.
PRACTICAL TESTS WITH CHROME ALUM STOP BATHS
At the outset, practical tests were made with the following formula:
Metric Avoirdupois
Potassium chrome alum 20 grams 8% Ibs.
Water to make 1 liter 50 gallons
Effect of Addition of Developer on Hardening Properties. In order
to gain a preliminary idea of the behavior of the stop bath on ex-
haustion with film, increasing quantities of the developers D-16
and D-76* were added to a definite volume of the bath and samples
stored at 70F. and 110F. Hardening tests were then made at
regular intervals after storing the mixtures for increasing periods of
time.
The tests with the D-16 developer were made according to the
procedure described on page 486 for alkaline film. With the D-76
developer a similar procedure was followed, except that strips of
Eastman motion picture panchromatic negative film were developed
in D-76 for ten minutes. The fixing bath for these tests contained
30 per cent hypo and 1.0 per cent sodium bisulfite.
The hardening tests were made by determining both the reticulation
and melting points of the film. Since a hardening stop bath is used
mostly for high temperature work, the reticulation point is of the
* Formula D-76
Metric
Avoirdupois
Elon
2 grams
13 ounces
Hydroquinone
5 grams
2 pounds
Sodium sulfite (anhydrous E. K. Co.)
100 grams
42 pounds
Borax
2 grams
13 ounces
Water to make
1 liter
50 gallons
May, 1930]
STOP BATHS AND FIXING BATHS
499
greatest importance because, although a film is insoluble in boiling
water, it may reticulate readily and a reticulated film is usually
worthless.
In practice when processing at high temperatures it is important
that the film should not swell and at the same time it should have a
fairly high melting point. In many cases, the thickness of the film
was measured before determining the reticulation and melting points
and it was found that a fairly close relation existed between the de-
gree of swelling and the reticulation point as is shown by Table II.
TABLE II. Relation between Hardness and Degree of Swelling of Film
Footage Processed per Gallon
Thickness
Reticulation
Point
Melting Point
0.010 in.
Nil
210 F.
125
0.011 in.
Nil
210 F.
190 (before revival with acid)
. 013 in.
105 F.
170 F.
190 (after revival with acid)
0.013 in.
105 F.
170 F.
250
0.013 in.
100 F.
130 F.
315 (before revival with acid)
0.013 in.
95 F.
120 F.
315 (after revival with acid)
0.013 in.
95 F.
120 F.
375
0.013 in.
95 F.
110F.
It is seen that the unswollen film did not reticulate but, after
swelling from 0.010 to 0.013 inch, the reticulation point dropped
to 105F., although the film melted at a temperature as high as
170 F.
The effect of adding D-16 developer to a 2 per cent chrome alum
stop bath is shown in Fig. 7. The results indicate that a quantity of
developer equal to 10 per cent of the volume of the bath may be
added before an immediate drop in the melting point occurs. This
corresponds to a footage of 200 feet per gallon. After storage for three
weeks at 70F. and 110F., the life of the bath was reduced to 150
feet per gallon. The hardening action of a similar stop bath con-
taining D-76 developer fell off more rapidly with the addition of
increasing quantities of developer. This was to be expected as
formula D-76 contains more sodium sulfite than formula D-16.
The life of the bath with D-76 developer was reduced to 115 feet
per gallon in the fresh bath and to 85 feet per gallon after the bath
had stood for three weeks.
From the results in Fig. 7 it is seen that: (1) a change in the
storage temperature from 70F. to 110F. has very little effect on
the loss in hardening properties on the addition of developer;
500
J. I. CRABTREE AND H. D. RUSSELI, [J. S. M. P. E.
(2) the hardening properties of solutions having a pH greater than 4.0
fell off rapidly on ageing; (3) the acidity of the solutions containing
developer increased on ageing except in the case of solutions con-
Z 7* CHROHEL MJJH
P-\<b (AUKMJNE. FIL.M)
SOLUTIONS STORES KT 70F --- STORE.P AT l\0*F
(s) HVPROXIPE:
FRELSH
FIG. 7. Effect of the addition of D-16 developer on the hardening properties
of a plain 2 per cent chrome alum stop bath.
taining sludges; (4) the hardening decreased most within the first
24 hours after adding developer.
Effect of Exhaustion of Stop Baths without Revival. For the
practical exhaustion tests, 50 foot lengths of Eastman motion picture
May, 1930]
STOP BATHS AND FIXING BATHS
501
positive film were developed in D-16 at 70F. and processed in a
manner similar to that described on page 486 for alkaline film.
The effect of exhaustion on the hardening properties of 2 per
cent and 3 per cent plain chrome alum stop baths is shown in Fig. 8.
The hardening properties of the 2 per cent bath decreased rapidly after
200 feet of film per gallon had been processed, which may be con-
sidered as the life of the fresh bath. After storing for two weeks, the
hardening life of the bath decreased to 100 feet per gallon. The
CHROME: A.LUM
P-lfe 10*F
ioo ^oo soo 100 zoo
FIG. 8. Effect of the exhaustion without acid revival on the hardening
properties of 2 per cent and 3 per cent chrome alum stop baths (D-16
developer, 70 F.).
change in acidity during the processing of 250 feet of film per gallon
was from a pH of 3.2 to a pH of 5.0 at which point a chromium
sludge precipitated on standing.
A maximum degree of hardening was obtained in the fresh 3 per
cent bath throughout the entire period of processing 300 feet of
film but after storing for two weeks the life of the bath decreased
to 200 feet of film per gallon. The acidity changed from a pH
of 3.2 to a pH of 4.2 during the exhaustion with 300 feet per gallon,
which was not as great as the acidity change in the 2 per cent bath
under similar conditions. No sludges were formed in the 3 per cent
bath even after standing for two weeks at 70 F.
502 J. I. CRABTRBE AND H. D. RUSSELL [J. S. M. p. E.
A comparison between the hardening properties of the 2 per cent
and 3 per cent chrome alum stop baths indicated that the hardening
life of the 3 per cent bath is about twice as great as that of the 2
per cent bath. It also seems plausible that a further increase in
hardening properties might be obtained with higher concentrations
of chrome alum, but concentrated solutions of chrome alum terid to
stain the film, especially at high temperatures. For this reason,
it was not considered desirable to increase the concentration of
chrome alum beyond 3 per cent for use as a stop bath.
Effect of Exhaustion and Revival with Acid on the Hardening Proper-
ties of Stop Baths. Practical exhaustion tests during which the stop
baths were suitably revived were made with 2 per cent and 3 per
cent chrome alum solutions as follows. Lengths of Eastman positive
motion picture film were processed in D-16 at 70F. and 85F. in a
manner similar to that outlined previously. Ten per cent of sodium
sulfate (desiccated) was added to the D-16 developer at 85 F.
to prevent excessive swelling. One hundred cc. samples of the
solution were taken after every 50 feet of film had been processed
and after revival with acid. They were then stored at 70F. and
their hardening properties measured at regular intervals. Lengths
of Eastman panchromatic negative motion picture film were de-
veloped in D-76 for 10 minutes and subsequently given a treatment
similar to the positive film in D-16 above.
The acidity of the baths was revived at regular intervals by
adding a quantity of acid so as to restore the acidity of the bath to a
pH of 3.0, at which point previous experiments had indicated that
maximum hardening was obtained. The condition of the bath was
determined by titrating a 25 cc. sample (in 50 cc. of distilled water
containing 5 cc. of brom phenol blue indicator) with a 2.5 per cent
sulfuric acid solution until the solution was just acid to the indicator.
From these results the quantity of concentrated acid necessary
to add to the bath was calculated. The pH of the bath was always
measured after the concentrated acid had been added so as to be
sure that it was correct. The average quantity of concentrated
acid which it was necessary to add at each revival point with the
D-16 developer was 1 cc. per liter or 0.13 ounce per gallon and
with film developed in D-76 the quantity was 1.5 cc. per liter or 0.19
ounce per gallon. The results of the exhaustion tests are given in
Figs. 9, 10, 11, 12, and 13.
With D-16 at 70F. (Fig. 9), the 2 per cent bath, revived with
May, 1930]
STOP BATHS AND FIXING BATHS
503
acid after processing 150 feet of film per gallon, was capable of treating
250 feet of film per gallon before a decrease in the hardening proper-
ties occurred. The hardening action was restored by the addition
of acid but decreased on further exhaustion up to 380 feet per gallon.
The original degree of hardening was again obtained after the addition
of acid and the hardening action again decreased after processing
500 feet of film per gallon. After revival with acid the hardening
properties increased but decreased rapidly on further exhaustion
g' 30
-90
3.0
4.0
3.0
4-0
2 % CHROME ALUM
TOT
O MELTING
R- REVIVAL
\$ - 4
FRESH
epH
FRESH
I WEEK
FEET PER GALLON
I WEEK
100 200 300 4OO 3OO 60O 7OO QOO
FIG. 9. Effect of exhaustion with acid revival on the hardening properties
of a plain 2 per cent chrome alum stop bath (D-16 developer, 70 F.).
when they were not satisfactorily revived by the addition of acid.
The hardening action of the samples was again determined after
storing for one week. With the samples taken before revival a
minimum degree of hardening was obtained except in the case of the
sample taken at 150 feet when the hardening action was satisfactory.
This indicates that the bath should be revived more frequently if
uniform hardening properties are desired.
With D-16 at 70F., the 3 per cent bath, when exhausted and
revived in a manner similar to that employed for the 2 per cent
bath, showed more uniform hardening properties (Fig. 10). A
maximum degree of hardening was maintained throughout the ex-
504
J. I. CRABTREE AND H. D. RUSSEU, [J. S. M. p. E.
haustion with 750 feet of motion picture positive film per gallon.
A slight decrease in the hardening properties was obtained with the
samples one week old which were taken before revival after processing
450 feet of film.
The hardening properties of the 3 per cent chrome alum bath
decreased more rapidly on exhaustion with D-76 at 70F. (Fig. 11)
than those of the 3 per cent bath exhausted with D-16 at 70F.
The hardening properties were maintained until 300 feet of film
*"
S' 70
2/3*
Sso
3.0
3% CHROME ALUM
D-lfe 70* P.
O MELTING
RETICULATION
R-REVIVAL
FRESH
epH
X 130
90
I YfK
4.0
FEET f>CK G*l.t.t
I WEEK
100 200 500 400 500 6OO 70O 800
FIG. 10. Effect of exhaustion with acid revival on the hardening properties
of a plain 3 per cent chrome alum stop bath (D-16 developer, 70 F.).
per gallon had been processed by reviving with acid every 100
feet, but on further exhaustion the hardening action decreased
rapidly and the baths could not be satisfactorily revived by the
addition of acid.
With D-16 at 85F., the hardening properties of the 2 per cent
bath during exhaustion with revival were more uniform than when
the bath was exhausted at 70F. (Fig. 12). A maximum degree of
hardening was maintained until 600 feet of film per gallon had
been treated. The film processed in the samples one week old taken
after the second revival reticulated at a temperature of 90F., indi-
cating that too much acid had been added during revival.
May, 1930]
STOP BATHS AND FIXING BATHS
505
170
130
,
t 90
3.0
4.0
2to
no
so
CHROME. MAJM
FRE.S.H
FRELSH
\ WE.E.K
FELELT PELR &f\L.V-ON
\ WE1E.K
100
2.00 30O 40O 500 foOO 100 600
FIG. 11. Effect of exhaustion with acid revival on the hardening properties
of a plain 3 per cent chrome alum stop bath (D-76 developer, 70 F.).
v> 170
r
Q 90
3.0
Z % CHROME ALUM
O MELTING
RETICULATION
R-REV/VAL
FRESH
3.0
4.0
FEET PER.
/ MEEK
zoo
300
-100
JOO
700 800
FIG. 12. Effect of exhaustion with acid revival on the hardening properties
of a plain 2 per cent chrome alum stop bath (D-16 developer, 85 F.).
506
J. I. CRABTREE AND H. D. RUSSEU, [J. S. M. p. E.
With the 2 per cent bath, the hardening properties on exhaustion
with D-76 at 85F. were inferior to those of the other baths investi-
gated (Fig. 13). Revival with acid every 100 feet per gallon in-
creased the hardening action at these points but the hardening
decreased rapidly on further exhaustion. After 300 feet of film
per gallon had been processed, satisfactory hardening properties
were not maintained.
The low temperature at which the film reticulated before each
100 ZOO 300 400 500 <bOO TOO &00
FIG. 13. Effect of exhaustion with acid revival on the hardening properties
of a plain 2 per cent chrome alum stop bath (D-76 developer, 85 F.).
revival indicates that the bath should have been revived more
frequently. The age of the stored samples had little effect on the
hardening properties.
SUMMARY
The function of a chrome alum stop bath is to arrest development
and harden the emulsion before fixing. It also prolongs the life of an
alum fixing bath by virtue of preventing the addition of alkali.
This, in turn, serves to maintain the hardening properties of the
fixing bath and prevent sludging.
At normal temperatures it is no 
