(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Journal of the Society of Motion Picture Engineers"



From the collection of the 



Prejinger 
v Jjibrary 



San Francisco, California 
2007 




vlE XXIII NUMBER ONE 

JOURNAL 

of the 

SOCIETY OF MOTION 
PICTURE ENGINEERS 







JULY, 1934 



HED MONTHLY BY THE SOCIETY OF MOTION PICTURE ENGINEER! 



The Society of Motion Picture Engineers 
Its Aims and Accomplishments 

The Society was founded in 1916, its purpose as expressed in its 
constitution being the "advancement in the theory and practice of mo- 
tion picture engineering and the allied arts and sciences, the standardi- 
zation of the mechanisms and practices employed therein, and the 
maintenance of a high professional standing among its members." 

The membership of the Society is composed of the technical ex- 
perts in the various research laboratories and other engineering 
branches of the industry, executives in the manufacturing, produc- 
ing, and exhibiting branches, studio and laboratory technicians, 
cinematographers, projectionists, and others interested in or con- 
nected with the motion picture field. 

The Society holds two conventions a year, spring and fall, at various 
places and generally lasting four days. At these meetings papers 
dealing with all phases of the industry theoretical, technical, and 
practical are presented and discussed and equipment and methods 
are often demonstrated. A wide range of subjects is covered, many 
of the authors being the highest authorities in their particular lines 
of endeavor. Reports of the technical committees are presented and 
published semi-annually. On occasion, special developments, such 
as the S. M. P. E. Standard Visual and Sound Test Reels, designed 
for the general improvement of the motion picture art, are placed at 
the disposal of the membership and the industry. 

Papers presented at conventions, together with contributed arti- 
cles, translations and reprints, abstracts and abridgments, and other 
material of interest to the motion picture engineer are published 
monthly in the JOURNAL of the Society. The publications of the 
Society constitute the most complete existing technical library of 
the motion picture industry. 



JOURNAL 

OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 

Volume XXIII JULY, 1934 Number 1 



CONTENTS 

Page 

Report of the Committee on Standards and Nomenclature 3 

Report of the Sound Committee 6 

Report of the Non-Theatrical Equipment Committee 9 

The English Dufaycolor Film Process W. H. CARSON 14 

Operating Characteristics of the High-Intensity A-C. Arc for 

Motion Picture Projection D. B. JOY AND E. R. GEIB 27 

The Relation of the High-Intensity A-C. Arc to the Light on the 

Projection Screen D. B. JOY AND E. R. GEIB 35 

An Improved System for Noiseless Recording 

G. L. DIMMICK AND H. BELAR 48 

Committees of the Society of Motion Picture Engineers 55 

Book Reviews 58 

Society Announcements 59 

Obituaries: C. Francis Jenkins; J. Elliott Jenkins 59 



JOURNAL 

OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 



SYLVAN HARRIS, EDITOR 

Board of Editors 
J. I. CRABTRBB, Chairman 

O. M. GLUNT A. C. HARDY L. A. JONES 

J. O. BAKER 



Subscription to non-members, $8.00 per annum; to members, $5.00 per annum, 
included in their annual membership dues; single copies, $1.00. A discount 
on subscriptions or single copies of 15 per cent is allowed to accredited agencies. 
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton 
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y. 

Published monthly at Easton, Pa., by the Society of Motion Picture Engineers. 

Publication Office, 20th & Northampton Sts., Easton, Pa. 
General and Editorial Office, Hotel Pennsylvania, New York, N. Y. 
Entered as second class matter January 15, 1930, at the Post Office at Easton, 
Pa., under the Act of March 3, 1879. Copyrighted, 1934, by the Society of 
Motion Picture Engineers, Inc. 

Papers appearing in this Journal may be reprinted, abstracted, or abridged 
provided credit is given to the Journal of the Society of Motion Picture Engineers 
and to the author, or authors, of the papers in question. Exact reference as to 
the volume, number, and page of the Journal must be given. The Society is 
not responsible for statements made by authors. 



Officers of the Society 

President: ALFRED N. GOLDSMITH, 444 Madison Ave., New York, N. Y. 
Executive Vice-President: HAROLD C. SILENT, 7046 Hollywood Blvd., Los 

Angeles, Calif. 

Engineering Vice-President: LOYD A. JONES, Kodak Park, Rochester, N. Y. 
Editorial Vice-President: JOHN I. CRABTREE, Kodak Park, Rochester, N. Y. 
Financial Vice-President: OMER M. GLUNT, 463 West St., New York, N. Y. 
Convention Vice-President: WILLIAM C. KUNZMANN, Box 400, Cleveland, Ohio. 
Secretary: JOHN H. KURLANDER, 2 Clear-field Ave. , Bloomfield, N. J. 
Treasurer: TIMOTHY E. SHEA, 463 West St., New York, N. Y. 

Governors 

EUGENB COUR, 1029 S. Wabash Ave., Chicago, 111. 
HERFORD T. COWLING, 7510 N. Ashland Ave., Chicago, 111. 
ARTHUR S. DICKINSON, 28 W. 44th St., New York, N. Y. 
RALPH E. FARNHAM, Nela Park, Cleveland, Ohio. 
HERBERT GRIFFIN, 90 Gold St., New York, N. Y. 
EMERY HUSB, 6706 Santa Monica Blvd., Hollywood, Calif. 
WILBUR B. RAYTON, 635 St. Paul St., Rochester, N. Y. 
HOMER G. TASKER, 41-39 38th St., Long Island City, N. Y. 



REPORT OF THE COMMITTEE ON STANDARDS 
AND NOMENCLATURE* 

Since the last report, this Committee has concentrated its efforts 
on the preparation of data for a new issue of the Standards Booklet. 
Much new material has been included, and some of the data con- 
tained in the old booklet have been rearranged and amplified. The 
material for the new booklet will be published in an early issue of 
the JOURNAL, and will contain data on cutting and perforating di- 
mensions of raw stock with tolerances, for 35- and 16-mm. sizes. 
Charts showing dimensions and location of camera and projector 
apertures, and sound track location for 35-mm. and 16-mm. sound 
film will be included. The standard 35-mm. sprocket specifications 
have been revised. 

The German standardizing body has accepted the dimensions of 
the S. M. P. E. standard 16-mm. film, but has made proposals differ- 
ing from them in the following respects, contained in a communica- 
tion from Mr. Flinker of the Standards Committee of the Deutsche 
Kinotechnische Gesellschaft, dated February 8, 1934: 

At first, it appeared that these proposals corresponded with those of the Ameri- 
can Standards Committee, which had been published on page 478 of the JOURNAL 
of the S. M. P. E., Nov., 1932. Later, however, it became obvious that the 
proposals of the two Committees differed considerably, especially in two respects: 

(/) The position of the sound track relative to the picture. 

(2} The position of the emulsion side in the projector. 

In regard to (1), the German proposal states that the location of 
the sound track on the outside (when film is passed through a pro- 
jector operated from the right-hand side when facing the screen) 
has advantages in constructional possibilities of equipment. The 
claims relate to details of arrangement of sound reproducer parts, 
and the arguments depend upon the mechanical design under con- 
sideration. It seems possible to design arrangements having all the 
advantages mentioned, or rendering them impertinent, with the 
sound track on the inside. 

In regard to (2), quoting from the German report: 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 



4 STANDARDS AND NOMENCLATURE COMMITTEE [j. S. M. P. E. 

The German Standards Committee agrees with the opinion of the American 
Standards Committee that it would be advisable to establish for all types of 
film a uniform position of the emulsion side in the projector, in order to avoid 
a differential focusing of the sound optic; they have come to the conclusion, 
however, that this is not possible in every case without encountering serious 
technical difficulties. It would be desirable, however, to come to some agree- 
ment on the subject, so that the designer would know what position he must 
first of all take into consideration. 

The German Committee recommends that the 16-mm. film be 
projected with the emulsion side toward the light, except in the case 
of 16-mm. reversal film. The S. M. P. E. Standard is to project all 
16-mm. film with the emulsion toward the screen, except in the case 
of Kodacolor or Keller-Dorian color prints. The German Committee 
points out that contact printing would require that the emulsion be 
run toward the light. Preference is stated for optical printing with 
the emulsions facing each other, resulting in prints to be projected 
with the emulsion toward the light. For home use either reversal 
film or optically reduced prints are required, as the pictures are made 
by the user of the projector or obtained from a library. In both 
cases, the emulsion may be away from the light in projection. 

As mentioned by Mr. Flinker, absolute standardization of the po- 
sition of the emulsion side in the projector for all conditions seems 
to be impossible. The Standards Committee will study the pro- 
posals regarding this point, however, and endeavor to reach a mutual 
agreement with the German Committee. Conclusions regarding 
the most important types of prints depend upon the fields of applica- 
tion. The S. M. P. E. Standards Committee has not found that in- 
formation received indicates any advantage in optical reduction 
printing by facing the emulsions toward each other; and, therefore, 
in this case, which is the more important one, the prints can be pro- 
jected with the emulsion toward the screen. 

Quoting again from the German communication: 

There are still other queries to be settled by the American and German Stand- 
ards Committees; for instance, the longitudinal distance between the sound 
and the picture, shrinkage, and standardization of sprocket wheels, but no 
reference is made to these points in the report. The German Standards Com- 
mittee is convinced that an agreement with regard to these questions can be 
deferred until a later date, and that no difficulties are likely to be encountered 
in this direction after the position of the sound track and the emulsion side in 
the projector has been agreed upon. It is the earnest desire of all German, and, 
we feel sure, also of American film technicians, that such an agreement should be 



July, 1934] STANDARDS AND NOMENCLATURE COMMITTEE 5 

arrived at. In Germany, the question whether or not it would be possible to 
adopt the American proposals has been studied very thoroughly. 

All large factories in Germany actually interested in the matter have thoroughly 
gone into it, but they have all come to the conclusion that in practice there are 
so many important arguments in favor of an alteration to the American pro- 
posals that even if they were to be adopted, the question of an alteration would 
be bound to turn up again in the near future ; and that the sacrifices then incurred 
by an alteration would be even greater if, in the meantime, a further supply of 
projectors according with the American standards has been put on the market. 
The German Standards Committee is therefore of the opinion that it would be 
advisable for the American industry to reconsider the question now, and trusts 
that the American Standards Committee, after having studied the above view- 
points in regard to the position of the sound track and the emulsion side in the 
projector, will agree with the German proposal. As the ultimate date for the 
final decisions regarding German Standards is March 15, 1934, it would be 
necessary to have the decision of the American Standards Committee here in 
Berlin by March 5, 1934, in case they also desire an agreement. 

This report was not received in time to arrange for a meeting of 
the S. M. P. E. Standards Committee to consider it, and reply before 
March 5th. In the absence of the chairman, Mr. C. N. Reifsteck 
transmitted a reply on the specific points mentioned. 

The complete report will receive further consideration by the 
Standards Committee, so that the information in the Standards 
Booklet when submitted to the Board of Governors for approval will 
be final ; and it is hoped will be acceptable to the German Committee. 

No further action has been taken in regard to the proposals from 
the British Standards Committee for a standard film core for 35-mm. 
raw stock and a proposed universal sign for all 35-mm. safety film. 

In the near future, the Committee plans to consider standards for 
16-mm. sprockets having one row of teeth, as required for sound 
film. It is planned to study the results of the work of the Labora- 
tory and Exchange Practice Committee, now studying the problem 
of standard reels for release prints. 

M. C. BATSEL, Chairman 

W. H. CARSON H. GRIFFIN W. B. RAYTON 

E. K. CARVER A. C. HARDY C. N. REIFSTECK 

L. E. CLARK R. C. HUBBARD H. RUBIN 

J. A. DUBRAY L. A. JONES H. B. SANTEE 

P. H. EVANS N. M. LAPORTE V. B. SEASE 

R. M. EVANS C. W. LOOTENS J. L. SPENCE 

R. E. FARNHAM D. MACKENZIE E. I. SPONABLE 

C. L. FARRAND G. F. RACKETT H. M. STOLLER 

L. DE FOREST S. K. WOLF 



REPORT OF SOUND COMMITTEE* 

In a communication addressed to the Chairman of the Committee 
by President Goldsmith, about the middle of March, the Committee 
was asked ". . .to formulate standards of sound recording and repro- 
duction (audio-frequency characteristics) of such a type that the 
producing studios and the theater circuits can all agree to accept 
them at a reasonably early date after the standards shall have been 
agreed upon. The present state of sound recording and reproducing 
indicates that the matter is definitely urgent. There is an unneces- 
sary amount of deviation in releases from the various studios, and it 
is obvious that the full advantages of improved methods of repro- 
duction can not be realized under the present conditions. Such 
standardization is the most important problem facing the Com- 
mittee." 

In order to attack the problems indicated in the above paragraph 
it was thought advisable to establish two major sub-committees 
of the Sound Committee, one of the sub-committees to be repre- 
sentative of the East Coast and the other of the West Coast. Mr. 
M. C. Batsel has been appointed Chairman of the Eastern Sub- 
Committee, the remainder of the personnel being as indicated at the 
end of this report. Establishment of the Western Sub-Committee 
awaits advices from Mr. H. C. Silent, Executive Vice- President of the 
Society, who has been requested to assist in selecting its personnel. 

On April 12th, the East Coast Sub-Committee met at the Hotel 
Pennsylvania, New York, at which meeting the discussions and 
conclusions that were reached were, it is believed, of particular 
significance to the Society and to the motion picture industry in 
general. The first question considered was, "Is it agreed that fre- 
quency characteristics measured in current or power are a measure 
of quality?" In answering the question, the Committee agreed 
that "in a linear, flutterless, noiseless system, frequency range meas- 
ured in current or power is one factor that determines quality." 
It was agreed that for the purpose of study by the Committee, the 
sound system should be divided into four sections : 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
6 



SOUND COMMITTEE 7 

(1) Acoustics of the stage and characteristics of the microphone. 

(2) From the output of (1) to and including the release print. 

(3) From the release print to the input of the loud speaker. 

(4) From the loud speaker to the ear. 

One of the most difficult tasks was to determine a starting point 
for the discussion. It was the consensus of opinion, however, that 
a standard for determining frequency characteristics should be es- 
tablished. It was agreed that frequency characteristics should be 
measured in terms of calibrated prints of frequency film, this print 
corresponding to release prints. A print is being prepared, to be 
independently calibrated in the Bell Telephone Laboratories and in 
the laboratories of the RCA Victor Co., which, when completed 
will be kept in the offices of the Society as a reference standard. 
Data will be available in the S. M. P. E. office regarding the measur- 
ing circuits employed in calibrating the film, and the methods of 
making comparisons with sub -standards. This film will be avail- 
able to studio personnel for use in calibrating secondary standards. 

An attempt will be made, by the time of the next meeting, to ob- 
tain data on the frequency characteristics being used in the several 
recording studios in the East. These data will serve as a basis of 
discussion of present practices and methods followed in determining 
the characteristics now employed. 

It is the aim of the Sound Committee to lay a foundation for one, 
two, or even five years' work, if necessary; and to formulate a plan 
so that at the completion of the program, systematic and compre- 
hensive coordination between the production studio and the theater 
can be achieved. It is hoped that the industry, as a whole, may 
become more closely associated, and that the theater audience may 
enjoy to the fullest extent the benefits that the industry is techni- 
cally capable of giving. 

L. W. DAVEE, Chairman 

East Coast Sub- Committee 

M. C. BATSEL, Chairman 

P. H. EVANS H. B. SANTEE E. I. SPONABLE 

R. M. EVANS W. A. MACNAIR . R. O. STROCK 

O. SANDVIK S. K. WOLF 

DISCUSSION 

MR. SPONABLE: I received one of the first copies of the Standard test reel 
devised by the Projection Practice Committee, and have been using it almost 
constantly since the time I received it. There is an indication that the reel is 



8 SOUND COMMITTEE 

gradually changing as a standard of frequency, also as a standard of sound 
quality. The Committee should investigate the question of how long a standard 
would remain a standard for frequency and speech and quality. 

MR. DAVEE: When the films that we propose to make are calibrated, the cir- 
cuits that are employed in the calibration will be in the Society's offices. Both 
the RCA Victor Company and the Bell Telephone Laboratories will calibrate the 
same film, and if a difference is found to exist between the calibrations, it will 
have to be eliminated. 

When the circuits are submitted to the Committee, it is expected that they will 
not differ so much as to forbid a satisfactory correlation between the two, and a 
standard measuring circuit will be arrived at so that we can check the frequency of 
the standard film from time to time to find out whether it has deteriorated or not. 

We do not particularly care what that frequency characteristic is; it can be 
anything, so long as we know what it is and can check it from time to time. 

MR. KELLOGG: The calibration of such a film involves not only correction for 
the frequency characteristics of the electrical circuits and equipment, but com- 
plete specification of the characteristics of the optical system. The first and 
obvious item is the width of the scanning or slit image on the film. That is very 
readily defined. The next question would be the percentage of light falling within 
the nominal image width; and even the distribution of light in both directions 
might have to be specified, especially if we are much concerned with the very high 
frequencies. The correction of the solid angle of collected light on the photo-cell 
side would probably have to be specified in order to obtain the same ratio of 
scattered light to specularly transmitted light in all calibrations. 

MR. DAVEE: Those points have already been discussed by the Sound Com- 
mittee, and as soon as we have the circuits I believe they will be covered. 




REPORT OF THE NON-THEATRICAL EQUIPMENT 
COMMITTEE* 

A general survey of the many uses of films, both 35-mm. and 16- 
mm., as applied to non-theatrical purposes, has been begun by the 
Committee. There seems to be no question but that this field 
is growing in importance at a rapid rate, and bids fair to approach 
the theatrical field in importance, if not eventually in film footage 
used. The historical situation with reference to non-theatrical 
films may be of some interest. For more than a decade, individuals 
and organizations making use of motion pictures for non-theatrical 
purposes have urged theatrical film producers to provide pictures 
especially made for non-theatrical showing. To these urgings, the 
theatrical industry has made practically no response, but has main- 
tained the general attitude that such production was the legitimate 
function of the theatrical producing companies, and would be taken 
up at some later date. In addition, the theatrical industry has 
generally been reluctant to permit a wide non-theatrical use of 
pictures originally made for theatrical exhibition. As a result, the 
supply of non-theatrical films and the ready availability of up-to-date 
theatrical films for non-theatrical purposes have been greatly limited. 

With the introduction of personal movies, however, there came 
into being a means of modifying the existing situation with reference 
to non-theatrical film and film exhibitions. Before personal movies 
had been in use for any length of time, manufacturers of sub-standard 
equipment met the challenge of auditorium projection, with the 
result that it is now possible to fulfill practically every important 
non-theatrical film need with sub-standard equipment and film. 
The ready supply by the sub-standard industry of material that had 
been withheld by the theatrical producers has convinced non- 
theatrical interests that sub-standard projection and, in a large 
number of instances, sub-standard production, is the real answer to 
the non-theatrical motion picture problem. At the present time, 
the trend of non-theatrical film usage is toward the sub-standard 
widths. The special problem of supplying sub-standard versions of 

* Presented at the Spring, 1933, Meeting at Atlantic City, N. J. 



10 NON-THEATRICAL EQUIPMENT COMMITTEE [j. s. M. p. E. 

standard sound subjects for non-theatrical projection is being given 
active attention at this time and the availability of such films is 
definitely on the increase. 

Obviously, the scope of this committee is quite broad, but the 
following comprise the main divisions : 

(1) Industrial Advertising: 35-mm. and 16-mm. 

Silent 
Sound 

(2) Educational: 35-mm. and 16-mm. 

Schools 

Industrial employee training 

(3) Medical 

(4) Religious and ethical 

(5) Research 

Industrial 
Medical 

(6) Film Slides 

Industrial 
Educational 

(7) Records 

Library 

Bank 

Industrial 

Medical 

Insurance 

(8) Legal 

Insurance 
Accidents 

(9) Government 

All the above 
Military and naval 
(10) Amateur 
Sports 
Miscellaneous 

(1) Industrial. This is by far the most extensively developed 
non-theatrical film application. Reference is made to Motion Pic- 
tures in Industry, published by the National Advertisers Association, 
Inc., 537 South Dearborn Street, Chicago (500 per copy). 

(2) Educational -The interest of educators and the appreciation 
of the practical value of films for teaching purposes are increasing 
with surprising rapidity. For reasons of safety, convenience, economy, 
etc., 16-mm. film is used for educational purposes to a much greater 



11 



July, 1934] NON-THEATRICAL EQUIPMENT COMMITTEE 

extent than 35-mm. film. With the possible exception of large 
institutions where a regular projection room and operator are avail- 
able 16-mm. film will probably supplant the 35-mm. for educational 
purposes. Movies have been used extensively in various arts, in 
museum activities, for recording the activities of college and alumni 
organizations, and for physical education in its various phases. 

Various departments of the U. S. Government have for many 
years used films for instructional purposes. The Civilian Conserva- 
tion Corps project brought this possibility to the fore. The Unite 
States was represented at the International Congress on the Educa- 
tional Use of the Cinema held at Rome, in April of this year. More 
and more material is being published covering this field. 

(3) Medical. The value of movies for photographing delicate 
surgical operations has been appreciated for a long time. Sixteen- 
mm. film and the convenient cameras and projectors available for it 
have induced a rapid growth in the number of such pictures taken. 
Several medical papers have been presented in full as movies, and 
it is now quite customary for medical papers to be accompanied by a 
movie. The medical and dental supply houses have extensive film 
libraries, and usually conduct movie "clinics" in conjunction with 
medical conventions. Several medical films have been made in 
Kodacolor, and, where conditions permit taking, Kodacolor is in- 
valuable. This process is as yet available only in 16-mm. 

(4) Religious and Ethical. Selected films are quite often shown 
at church bazaars, and the like. Judging from comments made 
recently in some of the trade papers (The Spectator, Hollywood), there 
seems to be a growing tendency toward the wider use of more speci- 
alized films in this field. The Religious Motion Picture Foundation 
has brought about a very active production of sub-standard films for 
use in religious work, including films depicting missionary activities 
and those giving instruction in religious rituals. The Federal Council 
of the Churches of Christ in America maintains a department devoted 
to increasing the use of films not only in supplementary religious 
work but also in religious services. 

Many Parent-Teacher Associations and other organizations are 
grading pictures as suitable or unusuitable for showing to children. 
Pictures, usually educational in nature, but often purely entertaining, 
are often shown in schools and in the club-houses of Boy Scout and 
similar organizations. 

(5) Research Movies are being used extensively for all kinds of 



12 NON-THEATRICAL EQUIPMENT COMMITTEE [J. S. M. P. E. 

research, especially high-speed (slow-motion) shots of fast action. 
Micro-motion is a specialization applied to studies in industrial 
efficiency, and is attracting considerable attention. Movies for 
medical research purposes have particularly great value, and have 
already been referred to under section 3, on page 11. 

(6) Film Slides. Single frames of 35-mm. film are being used 
in place of regular lantern slides. Application is found in the in- 
dustrial and educational fields. The Committee hopes to be able to 
obtain further data on the subject at a later date. 

(7) Records. Many large libraries, including the Library of 
Congress, The Huntington, and others are photographing valuable 
records on film. The U. S. Department of the Interior is now en- 
gaged in photographing the famous Yale Historical Collection. 
Thirty-five-mm. film is used mostly for this type of work. A special 
device, the Recordak, has found extensive application in industry 
for photographing bank checks, bills, statements, etc. This unit 
utilizes 16-mm. film. 

By using film, copies of rare or cumbersome material are made 
available in a cheap, compact, and convenient form. It seems likely 
that such applications will find more and more favor. Movies are 
used extensively for obtaining historical records. A large number of 
war films, movies of past-presidents, etc., are becoming of greater and 
greater importance. In the industrial field, movies are made of 
building and constructional operations of all kinds. In the medical 
field, record movies are of great value and are finding application in 
pediatrics and similar fields for encouraging patients by demon- 
strating that they are making progress, even though slowly. 

(8) Legal. Every now and then one hears of a court case in 
which movies are admitted as evidence: accidents and false in- 
surance claims, particularly. 

(9) Government. The U. S. Government employs motion picture 
films for a large variety of purposes, which can be covered generally 
under the other classifications. The main divisions of such uses are 
for records, research, instruction, and propaganda. 

(10) Amateur, Miscellaneous. The amateur use of film is firmly 
established; and in this country at least one publication covers the 
field exclusively, while practically all the photographic magazines 
have sections devoted to the amateur movie maker. The amateur 
film user has gone so far in emulating his professional prototype 
and produces results of such high grade that efforts have been made 



13 



July, 1934] NON-THEATRICAL EQUIPMENT COMMITTEE 

to establish a specific name for this class. In many cases the amateur 
has gone off on experimental paths of his own. The equipment at 
his disposal is excellent and, in Kodacolor, he has a ^f^ 
ess that the theatrical filmer does not possess. In subject matter, 
the amateur has separated widely from the theatrical filmer, and the 
production of amateur photoplays cast in the professional or theat- 
rical vein has been more and more limited. Some amateur experi- 
menters, such as J. S. Watson, Jr., and Melville Webber, have been 
recognized by critics of the motion picture art as workers of as great 
endowment as any theatrical directors or cameramen The Amateur 
Cinema League, organized on a similar basis to the well-known 
Amateur Radio League, is firmly established, and is the sponsor of a 
large number of cine clubs in all parts of the world. These clubs 
engage in every type of cine activity, from the making of civic and 
local film records to quite elaborate dramatic productions. 

An Amateur Cine Competition has been held by the magazine 
American Cinematogmpher, which bids fair to be an annual event. 
At least one foreign amateur cinema magazine is sponsoring a similar 
competition; each year the Amateur Cinema League selects the best 
pictures submitted to it for review. Outside these more highly 
organized activities, there is a growing army of film users (16-mm., 
9V2-mm., and 8-mm.), whose shots are of purely personal interests. 
In the field of sport, movies find extensive application. Quite a few 
universities make a regular practice of photographing football games 
and using the films for checking faults and improving the teamwork of 
the players. Similarly, movies are found of great help in practically 
all branches of sport. This is especially true of slow-motion or semi- 
slow-motion pictures. 

(11) Civil, Social Movies, mostly 16-mm., have been used 
extensively for making records of civic developments, new buildings, 
parks, clean-up activities, safety and traffic regulations, etc. 
Use of movies in social work is increasing; they are used to 
popularize and explain what is being done or attempted, and have 
been found helpful in raising funds for many such purposes. 

R. F. MITCHELL, Chairman 

H. A. ANDERS H. T. COWLING A. SHAPIRO 

D BEAN H. DEVRY C. TUTTLE 

E W BEGGS R. E. FARNHAM A. F. VICTOR 

W. B. COOK H. GRIFFIN V. C. ARNSPIGER 

R. C. HOLSLAG 



THE ENGLISH DUFAYCOLOR FILM PROCESS* 
W. H. CARSON** 



Summary. The Duf ay color three-color additive system of color cinematography, 
employing a geometrical color-screen or reseau imprinted on the film base, is briefly 
described. As many as a million color elements per square inch are employed, and 
a correct color balance is achieved by adjusting the area covered by the blue dye 
in relation to that covered by the two other primary colors. No appreciable changes 
of equipment are required in applying the system commercially, either in photo- 
graphing, processing, or projecting, from what is now found in use. 

Many may wonder at the presentation of a paper on a subject as 
old in color photography as a color-screen process. However, the 
developments of the past two years have proved the process to be no 
longer in the theoretical and experimental stages but on a practical 
and commercial basis, and for that reason a discussion of the new 
Dufaycolor system seems to be in order. 

Any engineering group may rightly be skeptical of the recom- 
mendation or adoption of any innovation in the industry that can 
not conclusively demonstrate its basic soundness in both the theo- 
retical and' practical fields. However, past experience has shown that 
new scientific developments and improvements must be injected 
into the industry from the bottom up rather than from the top down. 
The introduction of sound into the motion picture industry came 
after years of research and the expenditure of millions of dollars in 
experimentation, which have been little recognized by the layman 
or the box-office patron. It was only through the tremendous pres- 
sure brought to bear by the sound technicians who visualized its 
future that it was finally grudgingly accepted by the producer and 
exhibitor and even more reluctantly by the public. Today it is 
impossible for silent productions to compete with talking pictures. 

The whole technic of producing silent motion pictures, including 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** New York, N. Y. 

14 



ENGLISH DUFAYCOLOR FILM PROCESS 15 

script writing, directing, acting, photographing, lighting, stage con- 
struction, processing, projection, and theater construction, has been 
revolutionized to serve the new medium of sound. But in return 
for all that, a broadened scope of dramatic and popular application 
of sound pictures with respect to their increased entertainment value 
has been found. Since we are dealing with an industry that depends 
for its continued prosperity on its dollar-and-cent value and an ade- 
quate return to its stock -holders, it must be admitted that the advent 
of sound motion pictures has enabled the motion picture industry to 
retain a position in the entertainment field through a most trying 
period, when almost every other industry in the luxury field has been 
forced into bankruptcy, if not completely annihilated. 

Color in motion picture photography must enjoy the same con- 
sideration in planning productions, selecting subjects, actors, make-up, 
costumes, settings, in directing, lighting, and photographing, that 
is now being given to sound, if it is to contribute as fully to the 
progress of the industry; but it can not fail to assume a position of 
similar importance in the very near future. No claim for originality 
is made for these statements, and recognition must fairly be given 
to the pioneer work that has been done by Technicolor under the 
able direction of Dr. Herbert T. Kalmus along those lines. The 
progress that has been made up to the present in recognizing a 
distinct technic in color production lends some encouragement to 
the conviction that producers are awake to the possibilities of color, 
and are only waiting to be shown the practical means of application 
and be assured consistently satisfactory results on duplication before 
making it a major consideration in future productions. 

The first question that arises is whether colored motion pictures 
having a true color fidelity throughout the full range of the visible 
spectrum can be produced commercially for a slightly increased 
cost, which increase might be justified by an increase either in the 
box-office receipts or in entertainment value, permitting the motion 
picture to maintain or improve its present outstanding value as 
entertainment so that financially it may continue to compete success- 
fully against other and newer amusements. 

No industry that occupies such a paramount position as the motion 
picture industry occupies in the amusement field can afford to "rest 
on its oars" during a time when changing conditions in the social order 
are creating a superabundance of leisure for the average person, 
who can now indulge more frequently in the pleasures that formerly 



16 W. H. CARSON [J. S. M. P. E. 

he was able to enjoy only to a limited extent; or, if these are not 
sufficient to satisfy his need, seek new and other diversions with 
which to fill his time. Countless thousands of dollars are being 
spent to create, on an ever-increasing scale, extravagant and spec- 
tacular productions that must in time break down of their own weight. 
Some new and startling feature must be introduced to rejuvenate the 
appeal, a feature that would admit of simplifying or abandoning the 
costly artificial settings and bring into play a new artistic medium, 
which, while new in motion pictures, is one of the primal appeals to 
which human beings react color. 

After a comprehensive study of all the theoretical processes avail- 
able and those that have been in a measure successful, the conclusion 
was reached that two-color and three-color optical and imbibition 
processes have not, with existing equipment, both taking and pro- 
jection, given a result on the theatrical screen that will satisfactorily 
fulfill these various requirements. The ideal method of producing 
colored motion pictures would seem to be a system by which such 
colored pictures could be made with the existing cameras and light- 
ing equipment, and supplied to the exhibitor for satisfactory use on 
his present projection equipment without expensive alterations ; and, 
what is equally as important, to accomplish that result without any 
radical change in the present laboratory procedure. Thus it would 
be possible for every producing company to add color as a supple- 
mentary feature to its productions without disrupting its organi- 
zation or making large capital investments. All these require- 
ments are fulfilled by the Dufaycolor process, here described. 

For ordinary transparency purposes little importance seems to be 
attached to the pattern of the screen so long as the three primary 
additive color elements are present in the proper balance and pro- 
portion. Dufaycolor, Lumiere, Agfa, Finlay, or other transparencies 
that are really representative of these systems will all produce apparently 
perfect color rendition with suitable transmitted light if viewed at 
a distance of about eighteen inches by the average eye or projected 
from standard lantern-slide size to the usual small-screen size. 

Where non-geometrical color-screens are used it necessarily hap- 
pens that masses of the red, blue, or green units occur in the form 
of blotches or larger areas, and it is obvious that for achieving per- 
fect effects on greater magnification better results can be attained 
when the three primary color elements are regularly broken up into 
the smallest possible units and uniformly distributed. For that 



July, 1934] ENGLISH DUFAYCOLOR FILM PROCESS 17 

reason the geometric matrix or reseau, as it is termed, seems to have a 
decided advantage. It is believed that the Dufay system is the first 
screen process in which projection from standard 35-mm. film to 
theatrical screen size has been seriously attempted. The application 
of a reseau of this kind to a film base by mechanical means, on a 
regular and comparatively inexpensive commercial basis, further 
seems to enhance its value as an acceptable medium for use in the 
professional motion picture field. 

The idea of applying a series of colored lines or squares to the film 
base, originally suggested by Vidal in 1895, was used by Dufay in 
the further development of the process under discussion, wherein a 
contiguous series of red and green squares (or any two of the primary 
colors) were placed alternately between lines of blue (or the third 
primary color). Theoretically it would not seem to be of great im- 
portance as to what order was used in the application of the three 
primary colors. In practice it was found that on account of the 
high visual contrast of the blue line, the screen so constructed was much 
more visible when magnified to the extent necessary in motion pic- 
ture work than a different arrangement. At present the screen is 
produced with blue and red squares and a green line, which has the 
effect of reducing the visibility of the screen on projection. 

It is obvious that the smaller the area of each individual unit, 
the more perfect will be the blending of the color units by the eye, 
even upon excessive enlargement, and the less the effect on image 
definition. It was formerly believed that fifteen lines to the milli- 
meter was the limit of practical mechanical production, but within 
the last year a screen having nineteen lines to the millimeter (i. e., 
one thousand lines and spaces to the inch) has been very satisfactorily 
produced, and recent improvements point to a still further reduction 
of the line width. Even with the present line width it has been found 
that the reseau is not visible beyond the first six rows of the seats 
in the average theater. This provides the present screen with ap- 
proximately a million color elements to the square inch, and further 
diminution will have a progressively startling effect in definition and 
luminosity. 

The statement that such a screen or re*seau can be produced 
mechanically, consistently, in large quantities, on a commercial basis, 
and at a reasonable cost, will bear some scrutiny ; so the first question 
that arises is, has it been done? The answer is that it is now being 
done by a reputable and well-known English manufacturer on 21- 



18 



W. H. CARSON 



[J. S. M. P. E. 



inch acetate motion picture base in 1000-foot lengths at the rate of 
90,000 35-mm. cine* feet per week. Increased production is contem- 
plated immediately, and the reception of the film by the English pro- 
ducers has been very enthusiastic. 

The next question is, how is it done? A film base of suitable 
thickness (acetate base has been used exclusively because eventually 
legal restrictions will require it, but similar results are possible on 
nitrate) is first coated with a thin layer of collodion containing a dye, 
let us say blue, adjusted to the spectral hue of the blue primary. 
After drying, the film is then passed through a highly specialized 
type of rotary printing machine consisting of a steel roller milled one 
thousand lines to the inch (really five hundred lines, with an equal 
number of spaces between). The machine embodies an elaborate 




GRCASY L/ 



FIG. 1. Diagram illustrating the application of the resist, the bleaching 
of the spaces between the resist lines, the subsequent dyeing, and the scrub- 
bing process for removing the protective ink. 

ink distribution device for the roller; and underneath, in contact 
with it, a soft rubber covered roller capable of minute vernier con- 
centric adjustment for controlling pressure. The ink used on the 
press is a special kind, forming a moisture resistant line printed upon 
the basic color. The idea of using a greasy resist was first suggested 
by du Hauron and Bercegol in 1907. And here again reference should 
be made to the remarkable far-sightedness of Louis Dufay in the ap- 
plication of the basic principle of the geometric screen and the use 
of resistant medium for applying the primary colors to the film base 
by mechanical means. 

In the development of any new idea, there must be some individual 
or group that has enough faith in its ultimate value to be willing to 
finance it through the sterile years when salaries must be paid and 
valuable council and encouragement given in the face of apparently 



July, 1934] ENGLISH DUFAYCOLOR FILM PROCESS 19 

meager progress. It has been fortunate that this process has been 
sponsored by Spicers, Ltd., of London. This firm, manufacturers 
of all kinds of fine paper products, is an old English family organi- 
zation, whose commercial solidity has enabled them to keep their 
wheels turning through the past lean years, and who have pro- 
vided the financial backing and the technical guidance of such men 
of their organization as A. Dykes Spicer and S. R. Wycherley to 
bring this process to its present degree of perfection. However, the 
credit for the practical application of the resist on a commercial scale 
must be given to Charles Bonamico, a French engineer with Spicer- 
Dufay. His engineering skill in perfecting a means of milling a steel 
roller for applying the lines, and the subsequent control of applica- 
tion of the ink, marks one of the outstanding factors in the success 
of the process. 

Although the ink used in applying the resist is much thinner than 
would ordinarily be used for typographic purposes, under suitable 
conditions it assumes a partially dry state, providing lines having 
substantially sharp parallel edges and free from blur or creep, and 
when subsequently passed through a properly selected bleaching 
bath, produces perfectly clear white lines between the ink-protected 
lines. 

In the same machine, which has been especially designed for the 
process, the film is then passed into a bath containing dye of such 
concentration that will give the primary red on the intermediate 
bleached white lines. Allowing time and space for suitable washing 
to remove the excess red dye, the film then passes into a solution and 
a mechanical scrubbing action removes the protective ink. A 
simple diagram illustrating the method is shown in Fig. 1. If at 
this stage the film be examined with a microscope, we shall find that 
it is covered with a fine grid of alternating blue and red lines, having 
the same width and with perfectly contiguous but not overlapping 
edges, and each line representing a perfect primary filter in the two 
colors named (Fig. 2). 

After drying, the film is again passed through a similar rotary 
printing machine, but this time the lines on the printing rollers are 
at an angle of about forty-five degrees to the original lines (theo- 
retically the best angle is not forty-five degrees : this has a very im- 
portant bearing on other features of the process) . The width of the 
lines applied in this operation is not the same as that of the lines ap- 
plied in first, but is so controlled that the imprinted area alongside 



20 



W. H. CARSON 



[J. S. M. P. E. 



two contiguous squares, so formed, is equal to the area of each of the 
squares. The film is then bleached in a manner similar to that 
formerly described, the bleached line is dyed the third primary color 
(green), and the resisting ink is then removed in the same manner as 
described before (refer to Fig. 1). The film is then dried and wound 
up. This arrangement produces a perfectly balanced neutral grey 
screen when viewed or projected. When examined microscopically, 
a r6seau such as illustrated in Fig. 3 is seen. 

The next question refers to the emulsion to be applied to this 
reseau. While there are, of course, many applications for color film 
and the emulsion characteristics are correspondingly numerous, for 



V//////////////////////////A 



V///////////////////////////A 



W/////////////////////////J 
\ / 



FIG. 2. Appearance of the 
film under the microscope, 
after the process illustrated 
in Fig. 1. 



, BLUE 

| RED 

I GREBN 

FIG. 3. Appearance of the 
reseau under the microscope, 
after application of the third 
color. (In recent screens 
the green lines are at an 
angle of approx. 45 degrees 
to the blue and red.) 



the present only those that apply to cinematography will be con- 
sidered. 

It is interesting to note that in the very early stages of color de- 
velopment the theorists visualized an emulsion that was truly 
panchromatic and had a high speed and very fine grains. As no 
such emulsion existed at that time they approached the emulsion 
makers much as Macbeth sought the witches of Endor and suggested 
some diabolical brews that too often resulted in nothing more than 
toil and trouble, and never achieved results on a practical basis. 
For that reason it may be said that the development of color photog- 
raphy has had to mark time until the art of emulsion making could 
catch up with its theoretical requirements, and it is believed that that 
time has now arrived. 

It would be of interest to review some of the problems of the 



July, 1934] ENGLISH DUFAYCOLOR FILM PROCESS 21 

photographic chemists. The art of emulsion making formerly de- 
pended upon controlling the balance of silver halide and gelatin 
characteristics, together with delicate manipulation of heating, diges- 
tion, washing, ripening, etc., with more or less crude equipment. 
Today those factors have been so well correlated as to establish a 
science; and emulsion making equipment has become practically 
standardized, with automatic engineering controls that assure an 
accuracy permitting duplication of results within remarkably narrow 
limits. 

Considering also the great strides that have been made within the 
past few years by all the large photographic manufacturers, both 
in this country and abroad, in controlling the size of grain of super- 
speed emulsions without increasing the fog or impairing the keeping 
quality; and further, in developing new sensitizers by means of 
which emulsions can be made selective to any portion of the spectrum, 
visible, infra- visible, and supra-visible, it can be understood that 
problems in the reproduction of color, that seemed insurmountable 
a few years ago, have now been resolved by the progress that has 
been made in the black-and-white field of the art. The application 
of these advances to color photography now realizes satisfactory re- 
sults where before the same efforts met only with failure. 

So now, for the requirements of this process, emulsions may be 
selected practically according to specification, provided the basic, 
characteristics of the process are known. These factors are all well 
known, and are the same as those now operating in black-and-white 
technic: they may be briefly mentioned as speed, color-sensitivity, 
grain size, gradation, and gamma. With slight modification it may 
be said that a good panchromatic emulsion, rich in silver as compared 
with its gelatin content, with a color- sensitivity that will produce, 
as nearly as possible, the same density with all three of the primary 
colors, with a fine grain, and high speed will serve admirably for 
the process. Such an emulsion is now being used. 

There are several important characteristics that had to be con- 
sidered in selecting the emulsion that might be well discussed at 
greater length. First, the effect of wavelength on the gradation and 
gamma: Experience has shown that the effect of wavelength on 
gamma is negligible, provided it is measured at gamma infinity; 
but that, of course, must be considered in relation to exposure, 
development, and intermediate gradation. For that reason an 
emulsion has been selected that has a long straight line in its char- 



22 



W. H. CARSON 



[J. S. M. P. E. 



acteristic curve together with a short toe. So much progress has 
been made within the past few months that it is impossible to show 
by graphs the curves of the emulsion now being used, but it may be 
said that the range of latitude in the present emulsion is far greater 
than it was thought possible to produce a year ago. In any screen proc- 
ess it is imperative that the emulsion, no matter how thinly it may be 
coated, be capable of giving intense blacks, so that any colored area 
on the reseau may be effectually blocked out, allowing no dilution of 
the true color by the transmission of a foreign color that is not truly 
an additive component of the colors in the object being photographed. 
Second is the question of the spectral value of the filters. Various 
statements have been made as to the proportion of the incident light 
that passes through the many types of matrices used in the various 
processes, and have ranged from ten to twenty-five per cent. In the 



BLUE-VIOLET 



GREEN 



RED 




475 



550 



625 



700 



400 

FIG. 4. Diagram showing the approximate overlapping 
of the spectral transmission of the color filters used in the 
Dufaycolor process. 

Dufaycolor process the filter colors selected do not transmit in short 
narrow bands, but rather overlap from one to another much in the 
manner shown in Fig. 4. Whether that is theoretically the proper 
way to produce true color in a three-color additive process is of no 
particular concern if a result having a satisfactory color fidelity for 
the average eye is achieved. At the same time, such a procedure 
results in marked advantage as to the proportion of light transmitted 
to the emulsion on the taking film, and increases the luminosity 
of the resultant picture on the screen with ordinary projection 
light. (It has been noticed in this connection that a lower screen 
luminosity seems to be acceptable in color pictures than would 
be regarded as satisfactory in black-and-white.) The use of filters 
having such overlapping transmission characteristics may raise a 
question concerning the dilution of color on reproduction, but that 
will be covered later. The filters used also provide a remarkable in- 



July, 1934] ENGLISH DUFAYCOLOR FILM PROCESS 23 

crease in the latitude of exposure and development as compared 
with matrices in which niters having narrow transmission bands are 
used. 

Much advancement has been made in England in the past two 
years in perfecting dyes capable of very much greater light trans- 
mission than was formerly attained, without sacrificing their spectral 
fidelity. These new dyes have been adopted by Duf ay color. A 
method has been found to isolate them from the emulsion so that no 
desensitizing action takes place, and excellent adhesion between the 
matrix and the emulsion, which has heretofore often been unsatis- 
factory and extremely difficult to attain, has been accomplished. 
The two factors of increased speed of modern panchromatic emulsions 
and better dyes for the filters have made possible a film having a 
speed hitherto unattainable in screen processes. 

Any color process that does not provide for duplication in un- 
limited quantities, of consistent fidelity, and on a commercial scale 
is, of course, not worthy of consideration. It is believed that meth- 
ods have been found and patented by which to accomplish such re- 
sults to such a high degree of satisfaction that it is almost impossible 
to distinguish between originals made in the camera for projection 
and copies made from the original master positive. Up to last 
year it was believed that the same type of emulsion would serve 
both for taking and for making subsequent copies or dupes. At 
present, however, it is believed that the master positive, which might 
be called the original (and made in the camera), should have a heavy 
coating of emulsion as compared with the stock used for copies. 
When it is reversed it seems quite flat and the colors feeble, but when 
duplicates are made from it by the latest methods on a suitable 
printing stock, the colors come up to full strength. The maximum 
density is about 1.2, and a very wide range of gradation is main- 
tained. 

It has not been found possible to produce an emulsion adapted to 
all light conditions, natural (daylight) and artificial (arc and in- 
candescent), without using a compensating filter of some sort. Be- 
cause of the fact that a large proportion of professional motion 
picture photography is done under artificial light it seems best for 
the moment to adapt the film to artificial lighting, and to compensate 
for other conditions by using the proper filters. While very fast 
emulsions have been developed for the system, no claim is made that 
the speed is comparable with that of black-and-white, since there 



24 W. H. CARSON [J. S. M. P. E. 

must be a marked reduction in the transmission in any color process. 
However, a speed has been attained that makes it possible to fulfill 
the requirements of motion picture studios with the existing lenses 
and lighting equipment. 

Now regarding laboratory treatment : Many studios are at present 
working on the "master positive" basis, on which a positive is made 
by reversal from the edited first print after the cutting and timing 
have been done in order to gain the advantage of reduced graininess 
and uniformity of density. Although no reference has been pre- 
viously made, it is understood, of course, that the original film under 
this process is reversed to produce a positive result (it is possible to 
develop the film as a negative and make positive prints therefrom) . 
The procedure in reversal is standard. Developers of various kinds 
have been tested, the best results having been achieved with M-Q 
ammonia of rather high concentration at 65 F. After the bleaching 
and the second exposure, the second development occurs in an or- 
dinary metol-hydroquinone developer, and it is recommended that the 
second development be carried on under full illumination. It may 
be well to mention that by reversal the usual advantage of eliminat- 
ing the larger grains of the emulsion is gained, leaving the smaller 
grains to form the reversed image. It should be noted also that 
the entire procedure can be accomplished on existing motion picture 
developing machines with only very slight, if any, modification, 
and is therefore adaptable without expensive changes in equipment 
or personnel by any producing company that operates its own 
laboratory. 

No mention has as yet been made regarding the possibility of re- 
cording sound on the film; but that, of course, has been given full 
consideration. Several methods have been de'vised and patented 
for removing the screen or reseau, before the film is coated with 
emulsion, from the space along the edge of the film to be occupied 
by the sound track. In practice it has been found that such a pro- 
cedure is not necessary, as the number of lines in the screen that is 
used is so great that any effect it may produce on the various types 
of sound recording equipment now in use will not produce a reaction 
within the audible range. Recording can be done by either the 
variable width or the variable density method if the intensity of 
the recording light source is increased enough to offset the reduction 
of light transmission by the reseau. Similar remarks apply to the 
reproduction of sound during projection. 



July, 1934] ENGLISH DUFAYCOLOR FILM PROCESS 25 

The emulsion, which has been described as ideal for color repro- 
duction, is of the same type that would be selected by the sound 
engineer as the best for true sound reproduction. Sound has been 
recorded on all the standard systems, including the Movietone News 
camera, wherein a sound record was taken, through the reseau, on 
the same film as that used for the picture. Originals and copies 
have given excellent sound reproduction and, although several English 
sound experts have expressed the belief that the reseau would inter- 
fere with some of the higher frequencies of the audible range, as yet 
no such interference has been detected in practice. 

It has long been thought that it was impossible to reproduce from 
a screen transparency having a geometrical design due to the diffi- 
culty of exactly registering the colored areas in the original with the 
similar colored areas in the copy. The problem of avoiding moire 
effects in reproducing through a geometrical screen has also been ad- 
judged insurmountable but several simple and very ingenious methods 
have been developed to circumvent both those problems. 

Most of the research in the development of this process, theoretical 
and scientific, has been done by T. Thorne Baker, a member of our 
Society. Many of the statements in this paper are based upon data 
that he has supplied. 

Many technical points have been brought out in this paper that 
have not been fully covered; but as the purpose of this presentation 
is simply to describe the general process, it is hoped that further op- 
portunity will be given later for their more detailed discussion. 

DISCUSSION 

MR. MITCHELL : What is the relative speed, compared to black-and-white ? 

MR. CARSON: Developments are occurring so rapidly that I hesitate to 
answer. I will say, however, that the film that I am showing here is approxi- 
mately one-fourth as fast as black-and-white. We made some that were only one- 
third as fast. The fastest emulsion receives through the screen about one-third 
the light incident on the film. 

MR. PALMER: Is the picture you are to show a reversal print or a print from 
the original? 

MR. CARSON: Both. The first is an original or master positive, as made in 
the camera. The second will be a print made from some of the same scenes as a 
duplicate, made in England. It was developed under rather unfavorable condi- 
tions by rack and tank, and not by machine; and the evidences of the rack marks 
are present in the print. 

MR. POPOVICI: What kind of light was used for photographing? Arc or in- 
candescent? 



26 W. H. CARSON 

MR. CARSON : Arc and incandescent, I understand. I did not see the exposures 
made, as they were made in England. 

DR. GOLDSMITH: Approximately how many lines are there across the screen? 

MR. CARSON: Nineteen lines to the millimeter, or approximately one million 
elements to the square inch. With 25 lines to the millimeter, which is the screen 
that will be produced next, there will be approximately a million and a half to the 
square inch. The luminosity and the definition will both increase. The light we 
are using here is the standard light for black-and-white pictures. Even though 
there is stray light on the screen, which would not occur under good conditions, 
the picture is sufficiently bright. That is a fact that I mentioned in the paper 
that a lower screen brilliancy seems to be acceptable with color than with black- 
and-white. 

MR. BATSEL: Are the prints made by contact or by projection? 

MR. CARSON: Projection. We are not ready to discuss the method of print- 
ing right now, for patent reasons; but I will say that it was the combined work of 
the Ilford group, under the direction of Dr. Renwick, who was formerly with 
the Dupont Company. The film was made by the Ilford, Limited. 

MR. SACHTLEBEN: What difficulties, if any, are experienced in obtaining 
proper registration of the colors when making a print? How do you manage to 
have the greens green and the blues blue and not something else? 

MR. CARSON: A means has been devised of interposing a prism type of lens 
between the two films on the projection printer, which divides into four each of 
the color areas in the original screen as it prints, so that any color area is bound to 
fall on one similar to it. 

MR. CRABTREE: Was the original developed by machine or by rack-and- 
tank? 

MR. CARSON: By rack, also. 

MR. KELLOGG: One would expect, with the extent of the overlap of the spec- 
tral regions, that the printing process you just described would cost something in 
saturation. 

MR. CARSON: Theoretically, each time you step down, a certain dilution 
occurs due. to the overlaps. Here, again, means were found of eliminating the 
overlap in the printing operation. While there is some dilution, there is not very 
much. With proper laboratory treatment and machine control, duplicates can 
be produced that are entirely satisfactory for commercial use. 

MR. SACHTLEBEN: Mr. Carson stated that the quality of the print was su- 
perior to that of the original. I believe that has been quite well borne out in this 
demonstration. 

MR. CARSON: We don't consider it so. You misunderstood me. 

MR. SACHTLEBEN: I found the second reel that was shown more pleasing than 
the first. 

MR. CARSON: The fact of whether it is more pleasing to the eye or not is 
something that is more or less a matter of personal taste. What I meant to say 
was the spectral fidelity of the original is greater than the spectral fidelity of the dup- 
licates. I do not believe that the duplicates are exactly as good as the original. 
If you saw the two run side by side, you could distinguish the difference. If you 
saw one run in one place and one in another, they would appear so nearly alike 
that you would find it difficult to say which was which. 



OPERATING CHARACTERISTICS OF THE HIGH-INTENSITY 

ALTERNATING-CURRENT ARC FOR MOTION PICTURE 

PROJECTION* 

D. B. JOY AND E. R. GE1B** 

Summary. A detailed description is given of the high-intensity a-c. carbons, in- 
cluding the current-carrying capacity, the arc voltage, and the rate of consumption. 
The appearance of the arc and the carbons when the arc is burning is shown in a num- 
ber of illustrations covering overload and underload conditions, and long, short, and 
medium arc lengths. The essential requirements for the feeding mechanism and 
transformer to operate the arc are outlined. It is emphasized that the carbons must 
be operated under certain definite conditions for the best results. 

The new high-intensity a-c. arc was first discussed before the 
S. M. P. E. at the Spring, 1933, Meeting 1 at New York, and additional 
data 2 were given in connection with another subject at the Fall 
Meeting of the same year at Chicago. Subsequently it was the sub- 
ject of much consideration by the Projection Practice Committee. 
The writers contributed to the discussion and were later asked to put 
their comments in written form as it was felt that this information 
would be of value to both the users of the high-intensity a-c. arc and 
the equipment manufacturers. In this paper the high-intensity a-c. 
arc is described. In the following paper 3 the relationship of this arc 
to the light on the projection screen will be considered. 

The above papers 1 ' 2 gave a general description of the arc, the cur- 
rent and voltage ratings of the carbons, and approximate consump- 
tion rates. This is summarized in Table I. 

TABLE I 

Characteristics of Copper-Coated A-C. High-Intensity Carbons 





8-mm. 


7-mm. 


Current (Amperes) 


75-80 


60-65 


Approximate Arc Voltage 


24-29 


23-26 


Consumption (Inches per Hour) 


4.0-5.5 


4.0-5.5 


Current Density (Amps, per Sq. In.) 


970-1040 


1000-1090 



* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** National Carbon Co., Cleveland, Ohio. 

27 



28 D. B. JOY AND E. R. GEIB [J. S. M. P. E. 

A number of lamps and auxiliary equipment for using the a-c. high- 
intensity arc have recently appeared on the market and have been 
installed in a number of theaters. For that reason, a more detailed 
description of the arc and its operating characteristics will be helpful 
to those responsible for the operation of such equipment. 

The high-intensity a-c. projection arc is essentially a high current- 
density, low-voltage arc. At the rated currents the current density 
(970-1090 amps, per sq. in. of carbon cross-section) is very much 
higher than that of the mirror arc carbons (140-188 amps, per sq. 
in.), and somewhat higher than even that of the high-intensity d-c. 
positive carbons (450-900 amps, per sq. in.). Another difference is 
that in the conventional d-c. high-intensity lamp the positive carbon 
is gripped at a point close to the arc, whereas in the a-c. high-intensity 
lamps both carbons are clamped near the holder end. It is therefore 




FIG. 1. 8-mm. a-c. high-intensity carbons, over- 
loaded: 90 amperes, 35 volts. 

necessary to increase the conductance of the electrode by coating it 
with metal, which in this case is copper. The copper does not enter 
the arc stream, its only function being to furnish a low-resistance 
path for the current from the carbon holder to a point near the arc. 

By carefully observing the high-intensity a-c. arc in operation, it 
will be seen, as shown in the accompanying illustrations, that the 
copper coat ends an appreciable distance from the arc. As the car- 
bons are consumed the copper coat continually melts away, so that 
it never is sufficiently close to the tip of the carbon to enter the arc 
stream itself. 

This copper coat is designed to take care of the current rating of the 
carbon. If the current is too great, the copper will melt to a consider- 
able distance from the arc, as shown in Fig. 1. The arc then be- 
comes unsteady and is apt to blow out, and the arc voltage and con- 
sumption of the carbons are increased to such an extent that they may 




July, 1934] OPERATION OF HIGH-INTENSITY A-C. ARC 



29 



be outside the range of control of the arc-feeding mechanism. If, 
on the other hand, the current is too low, the copper will not melt away 
as far from the arc, the light will be very much reduced, and the 
current and voltage will not be constant. This condition results in 




FIG. 2. 8-mm. a-c. high-intensity carbons, underloaded: 60 amperes, 
24 volts; showing different positions of the arc as it "flops" about on the 
ends of the carbons. 

an unsteady arc, which "flops" from the top to the bottom of the car- 
bon, as illustrated in Figs. 2(A) and 2(5). If the current and volt- 
age limits recommended in Table I are observed neither of these un- 
desirable conditions will be encountered. 

The illustrations of the arcs shown in this paper are all traced from 
actual arc images, and show the true relationship between the differ- 
ent parts of the arc. 

It is essential for good operation of the arc and good light projec- 




BALL SHAPED />^^Si- HIGHLY LUMINOUS 
PORTION OF ARC x PORTION OF ARC 

LOWER LUMINOSITY 

FIG. 3. 8-mm. a-c. high-intensity carbons: 
80 amperes, 25 l / 2 volts; good operating con- 
ditions. 

tion that the high-intensity a-c. arc be maintained within certain 
definite arc lengths and that it have a characteristic shape which is 
easily identified. Fig. 3 shows the high-intensity a-c. arc burning 
under the correct conditions at 80 amperes and 25 Y 2 volts between 
two 8-mm. carbons. 



.30 



D. B. JOY AND E. R. GEIB 



[J. S. M. P. E. 



The copper coats end 0.35 inch (8.9 mm.) from the ends of the 
carbons. The arc length is 0.27 inch (6.9 mm.) long. The end of the 
electrode is 0.225 inch (5.7 mm.) in diameter. The arc itself consists 
of a highly luminous portion close to each electrode, and a portion of 
lower luminosity almost the shape of a ball extending about as far 
below the electrodes as above them and ending at the top in two 
well-defined short tail-flames. It is interesting to note that the shape 
of the highly luminous portion of the arc near the electrodes approxi- 
mates the shape of the intrinsic brilliancy curve across the electrode 
face, which was presented in an earlier paper 1 and is reproduced in 
Fig. 4. This highly luminous portion of the arc close to the electrode 
decreases in size as the current is decreased, and becomes very small 
at the lower current-densities, as illustrated in Fig. 2. This result 



1 

5? 400 


































!. 
















J- * 


, 


*- . 


-^^^^ 






















S 


^ 










^v 


\ 








N CANDLE P 

S s l 










/ 
















NS 


\ 














/ 


















\ 






ILUANCV 1 

1 S 










/ 




























































3 

S so 

S o 






































































" .16 -12 -oa .04 .04 .06 .12 



CADIU5 OF CBATER IN INCHES 



FIG. 4. Intrinsic brilliancy across crater face: 8-mm. 
a-c. high -intensity carbons; 80 amperes, 25 Va volts. 

gives, of course, a much lower intrinsic brilliancy curve and less light 
on the projection screen. 

If the arc length is decreased it will hold essentially the same arc 
shape, if the operating conditions are favorable, until it reaches ap- 
proximately 0.23 inch (5.8 mm.), or 24 volts. Fig. 5 (-4) illustrates 
the arc just before that point, with a good burning condition ; and Fig. 
5(5) the arc just after that point, with a shorter arc length and poor 
burning conditions. When the arc length is 0.23 inch (5.8 mm.) the 
arc stream begins to be turbulent. The two tail-flames and the highly 
luminous portion of the arc close to the electrodes lose their identity, 
and the whole arc assumes a boiling and seething appearance. There 
is rapid flicker; the arc voltage and current are erratic; and in addi- 
tion, at such very short arc lengths there is a noticeable shadow- 
ing effect from the electrodes themselves. 



July, 1934 J OPERATION OF HIGH-INTENSITY A-C. ARC 



31 



If the length of the arc is increased beyond that shown in Fig. 3, 
the form of the arc will be sustained if the operating conditions are 
suitable, until the length is approximately 0.35 inch (8.9 mm.). Fig. 
604) shows the arc immediately before, and Fig. 6(5) after, such a 
point has been reached. At and beyond, that length the arc has a 
tendency to be swept upward, so that the lower part no longer bows 
down appreciably and the upper part and the tail-flame become 
greatly extended. The highly luminous portion close to the elec- 
trode likewise becomes distorted, as shown in Fig. 6(5). The arc is 
unstable to such an extent that it will repeatedly jump back and forth 
between the positions shown in Figs. 6(^4) and 6(5). 

Another arc condition that must be considered and, if encountered, 
corrected, is shown in Fig. 7. The arc is of medium length, and would 
ordinarily have the appearance of Fig. 3, but is disturbed by external 
forces so that it appears very much like Fig. 6(5), and has the 




FIG. 5. 8-mm. a-c. high-intensity carbons: 80 amperes, 23 to 24 volts; 
(A) short arc length, good operating conditions; (B) short arc length, poor 
operating conditions. 

tendency to snap back and forth between that position and the one 
shown in Fig. 3, causing variation of the current and voltage, flicker, 
and uneven light distribution. This condition may be caused by too 
strong a draft in the lamp, or by an unbalanced magnetic effect due 
to a poor arrangement of the current leads; or by other means that 
would tend to distort the arc. 

If we assume that the design of lamp house, the draft, and the ar- 
rangement of leads are such as to avoid the above conditions, the 
8-mm. high-intensity a-c. carbons at 80 amperes will exhibit good 
burning characteristics for arc lengths between 0.23 inch (5.8 mm.) 
and 0.35 inch (8.9 mm.), and from approximately 24 to 29 volts. 
There will, however, be a noticeable change of light intensity between 
those extreme limits, so that the permissible range of variation in arc 
length and voltage from moment to moment is much less than the 
complete range of satisfactory performance. This is discussed in 



32 



D. B. JOY AND E. R. GEIB 



[J. S. M. P. E. 



greater detail in a later paragraph. The limits of arc voltage, as 
ordinarily measured at the incoming leads, will vary slightly depend- 
ing upon the length of spindle of the carbons, the lengths of the car- 
bons in the holders, and the resistance of the holders themselves 




FIG. 6. 8-mm. a-c. high-intensity carbons: 80 amperes, 28 to 29 volts; 
(4) long arc length, good operating conditions; (B) long arc length, poor 
operating conditions. 

At 75 amperes the arc lengths that will give good burning character- 
istics with the 8-mm. carbons are essentially the same as those for 80 
amperes, and the arc voltage is approximately one volt lower. 
The 7-mm. high-intensity a-c. carbons are rated from 60 to 65 am- 
peres. The corresponding conditions for good operation are an arc 




FIG. 7. 8-mm. a-c. high-intensity carbons: 80 
amperes, 26 volts; medium arc length, arc dis- 
turbed by external forces. 



gap of 0.21 inch (5.3 mm.) to 0.31 inch (7.9 mm.), and an arc voltage 
of approximately 23 to 26 volts. 

The action of the high-intensity a-c. arc under various conditions 
has a direct bearing on the limitations of the mechanism for feeding 



July, 1934] OPERATION OF HIGH-INTENSITY A-C. ARC 33 

the carbons. From the considerations discussed above it is apparent 
that such a mechanism must be able to feed the carbons at a rate up 
to 5.5 inches per hour; depending, of course, upon the current passing 
through the arc. It must also prevent the arc gap from varying more 
than 0.10 inch (2.5 mm.) or 0.12 inch (3.0 mm.); or, in terms of volt- 
age, it must prevent the arc from varying over a range greater than 
:] or 5 volts for the 7-mm. and 8-mm. carbons, respectively. These 
are the outside limits, for in order to utilize the total ranges the mecha- 
nism would have to be adjusted so that the average position of the 
carbons would be exactly at the center of the permissible variation. 
It must also be borne in mind that if the arc length varies in either 
direction much beyond the limits of good operation, the current and 
voltage become erratic and swing through a considerable range. If 
the feeding mechanism is controlled by either the current or the voltage 
the above action causes a sudden change in the rate of feeding that 
is not desirable. 

It is not practicable to adjust the feeding mechanism so that it will 
operate exactly at the center of the permissible range, nor can it be 
expected that other conditions might remain sufficiently constant to 
keep it exactly in that position. It is therefore necessary that the 
mechanism be designed to feed the carbons within a variation much 
less than the theoretically allowable limits. The narrower the range, 
the easier it is for the projectionist to maintain the lamp adjust- 
ment within the limits of satisfactory arc operation, and maintain a 
uniform intensity of screen illumination. 

These narrow limits for maintaining the arc length presented a real 
problem, but through close cooperation between the National Carbon 
Company and the manufacturers of projection equipment the desired 
results have been accomplished. 

In the paper 1 previously cited, it was mentioned that the high- 
intensity a-c. arc can be operated in series with a suitable resistance 
unit from the power line, but that for practical reasons a resistance is 
never used. A transformer and reactor are used instead. The 
transformer gives an electrical efficiency of 90 per cent or more, a 
figure that can not be equaled when ballast resistance is used. The 
reactor is usually the leakage reactance of the windings of a "high- 
reactance" transformer. It is desirable that the reactance be kept 
comparatively low, in order to maintain a reasonable power factor. 
On the other hand, it must be high enough to assure sufficient 
stability so that the arc may not be extinguished by ordinary drafts 



34 D. B. JOY AND E. R. GEIB 

at the longest desirable arc length. Tests have shown that a 40- 
per cent reactance will afford sufficient stability to the arc. In 
other words, if the no-load voltage on the secondary of the transformer 
is about 40 per cent higher than the load voltage, there will be suffi- 
cient stability of the arc for ordinary applications. Additional re- 
actance would improve the factor of safety, but above a no-load 
voltage of about twice the load voltage, the effect would not be no- 
ticeable. A lower reactance could be used and the results might be 
satisfactory in most cases, but any advantage achieved in reducing 
the reactance would not be worth the risk of an "outage." 

Another important factor in the design of a transformer for use with 
the high-intensity a-c. arc is the possible variation of line voltage on 
different installations. The transformer should be provided with 
suitable taps, or other means, so that it can be adjusted for the 
average line voltage of the theater in which it is installed. If the 
line voltage at the theater should vary appreciably, convenient 
means should be provided for the projectionist to change the trans- 
former taps and so regulate the secondary voltage. 

(The discussion of this paper at the Spring, 1934, Meeting at Atlantic City, N. J., 
was held simultaneously with that of the supplementary paper by the same authors, 
published also in this issue of the JOURNAL. The reader is referred to p. 47.) 

REFERENCES 

1 JOY, D. B., AND DOWNES, A. C. : "A New Alternating-Current Projection Arc," 
/. Soc. Mot. Pict. Eng., XXI (Aug., 1933), No. 2, p. 116. 

2 JOY, D. B., AND DOWNES, A. C.: "Direct-Current High-Intensity Arcs with 
Non-Rotating Positive Carbons," /. Soc. Mot. Pict. Eng., XXII (Jan., 1934), No. 
1. p. 42. 

1 JOY, D. B., AND GEIB, E. R.: "The High-Intensity A-C. Arc in Relation to 
the Light upon the Projection vScreen," /. Soc. Mot. Pict. Eng. XXIII (July, 1934), 
No. 1, p. 35. 



THE RELATION OF THE HIGH-INTENSITY A-C. ARC 
TO THE LIGHT ON THE PROJECTION SCREEN* 

D. B. JOY AND E. R. GEIB** 

Summary. The effect on the amount and uniformity of light on the projection 
screen of changing the position of the arc with respect to the reflector, varying the arc 
length, decreasing the current, and irregular feeding of the carbons is measured and 
discussed. The importance of proper draft conditions in the lamp house is em- 
phasized. The comparatively low temperature at the film aperture for a given amount 
of light on the projection screen from this type of arc is demonstrated. 

The unique wave-form of the screen light from this high-intensity alternating-current 
arc is compared with the wave-form of the screen light from the low-intensity alternat- 
ing-current neutral cored carbon arc and the rectified neutral cored carbon arc. A 
logical explanation is furnished by a consideration of these wave-forms for the com- 
parative freedom from light beat or fluctuation with this type of alternating-current 
arc. It is pointed out that this arc gives no greater light fluctuation on the screen than 
the arc from rectified current. Other causes of fluctuation of the screen light are cited 
and suggestions are given for minimizing their effects. 

The new high-intensity a-c. arc has already been compared with 
other types of arcs used for projection. 1 Since that time further data 
on details of operation have been accumulated which will enable the 
industry to use the arc to better advantage. The preceding paper 2 
in this issue of the JOURNAL furnishes some of those details, describ- 
ing the appearance of the arc, specifications for correctly operating 
the arc, and the general requirements concerning the reactance 
transformer and the feeding mechanism. The present paper, con- 
tinuing the subject, discusses the high-intensity a-c. arc in relation 
to the light on the projection screen. 

One of the objectives of good projection is to maintain a light of 
uniform intensity and good distribution on the screen at all times. 
As has been pointed out in the case of other types of arc, the light 
on the projection screen is dependent upon both the arc itself and 
the position of the arc in relation to the optical system. This applies 
also to the new high-intensity a-c. arc. 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** National Carbon Co., Cleveland, Ohio. 

35 



36 



D. B. JOY AND E. R. GEIB 



[J. S. M. P. E. 



The lamps using this carbon ordinarily have a horizontal trim 
with the carbon tip facing the back of the lamp, in focus with an 
elliptical reflector that projects the light picked up from the carbon 
and arc to the aperture and film. These lamps are provided with a 
device that throws an image of the arc on a white card, on which the 
correct arc length and arc position with respect to the mirror are 
indicated. They also have a method of feeding and adjusting the 
arc that keeps the carbons in the proper position with respect to each 
other and the optical system, provided the lamp is operated properly 
and the projectionist pays a reasonable amount of attention to the 
arc image. 

The following illustrations show what happens to the light on the 
screen when the arc is not kept in the correct focal position, and indi- 



HALF SIZE OBJECTIVE LENS 
6 '/z EFFECTIVE FOCUS 




FIG. 1. Diagram of optical arrangement used in the test. 

cate the leeway that the projectionist has in that respect in main- 
taining a reasonably uniform light on the projection screen. The 
curves were made by using one of the latest types of high-intensity 
a-c. projection lamps with an optical arrangement as shown in Fig. 1. 
If the magnification of the mirror, the size of the carbon, or the 
objective lens is changed, the shapes of the curves will remain essen- 
tially the same, but the relative values will be altered. 

Fig. 2 shows the effect on the screen light of keeping the arc length 
and the current constant but changing the position of the arc with 
respect to the mirror. As the arc is moved from the position of 
maximum screen light (C) toward the reflector, the total light on the 
screen decreases rapidly, the light at the corners of the screen in- 
creases in intensity, and the light at the center of the screen decreases 
in intensity; until, at the position A the light at the sides and corners 



July, 1934] 



HIGH-INTENSITY ARC AND LIGHT 



37 



of the screen is actually brighter than at the center, and the center 
appears yellow. As the arc is moved from the position C away from 
the reflector, the total light on the screen decreases at a slower rate 
and the distribution of the light on the screen remains practically 
constant. 

The curve of average screen light was constructed from the read- 



Soo 



4oo 



3oo 



loo 



too 



{I 

I! 




C 


/u 

^c/e 


'evAGE 
ZEN LIGHT 


/ K. 

I 1 

5" 




B 

/ 


Y 


X 


\ 


1 

^ * 


I 










1 2 3 
000 




15 $> 

MV* 
uU 

/Olrt^ 


At 
^ 






\ 




. 9 K 

**S 


\^ 


\ 




^d . 




L/0HT 


DlSTKIBU 


'IOH 


** 

J H 

f*J 











3.57 3.66 3.75- 3.84 3.33 4.Ot 

DISTANCE IN IMCHEJ Feon CAZ SON IN Focus To REFLECTO* 
FIG. 2. Light on projection screen vs. position of the arc; 

8-mm. high-intensity a-c. carbons: 80 amperes, 0. 29-inch arc 

length. 

ings of nine Weston photronic cells placed at points on the screen 
that afforded a representative average of the total screen illumination. 
The ratio of the light at the sides to the light at the center was ob- 
tained by comparing the average of the readings taken at positions 
1 and 3, Fig. 2, with that taken at position 2. The lower curve of 
Fig. 2 shows the change in this ratio for various positions of the arc. 
It is apparent from the curves that, with the particular optical 



38 



D. B. JOY AND E. R. GEIB 



[J. S. M. P. E. 



system used, the arc can be moved a distance of approximately 0.20 
inch without allowing a variation in the total light on the screen of 
more than 5 per cent, and with the distribution of light maintained 
within a reasonable range of uniformity. It should be remembered, 
however, that unless the lamp is so adjusted that the position of the 
arc, as indicated by the arc image, is at the center of the allowable 

range, a small movement one 
way or the other might cause 
a considerable change in the 
light on the screen. For ex- 
ample, if the lamp had been 
set so that the arc was in the 
position B with respect to 
the optical system, a move- 
ment of 0.10 inch of the arc 
toward the reflector would 
cause an undesirable change 
both in the quantity of light 
and its distribution on the 
screen. If the magnification 
of the optical system or the 
size of the light source were 
increased, the arc would have 
a greater latitude of motion 
for the same change in the 
light on the screen. 

The appearance of the 
high-intensity a-c. arc gives 
the impression that there is 
an appreciable quantity of 
useful light cut off by the 
carbon facing away from the 
reflector. A practical dem- 
onstration is given in Fig. 3, 

which indicates that at the minimum recommended arc length of 
0.23 inch, 2 there is only a very small loss of light due to the shadow- 
ing of the carbon, and it is not until an arc length of 0.20 inch has 
been attained that the loss becomes serious. It is also shown by the 
lower curve of Fig. 3 that this short arc length results in a poorer 
distribution of light on the screen. In addition, the arc tends to be- 





z 










g 








500 


*i 

i! - 


Av 


ZGAGE 5c 


GEE N Z.MJ/1 




^^ 






K 




f 






P 




{ 






8s 








4oo 


O.B 
5 - 
















K 










^J 










kj 










W 








3oo 


5 
















1 








7/yi 


|O V| M 








C.\J\, 

IOO 


5 ^ 


< 


LVHT 0. 


*jTRIBUTIOt\ 


^ 






'^ 

ih 










: x ? 










/ c^ j 









-II -tO .19 .3Q 

ABC LENGTH IN INCHES 

FIG. 3. Light on projection screen vs. arc 
length; 8-mm. high-intensity a-c. carbons: 
80 amperes, carbon in focus 3.84 inches 
from reflector. 



July, 1934] 



HIGH-INTENSITY ARC AND LIGHT 



39 



come unsteady, 2 and the arc feeding erratic. It should be noted 
in connection with Fig. 3 that the current was held constant for the 
various arc lengths by adjusting the transformer. 

If the arc length and the position of the carbons with respect to the 
mirror are held constant, but the current varied, the light on the 
projection screen changes as shown in Fig. 4. The light, of course, 



p 

I 




















AV&ZAQC LIGHT ON PROJECTION SCREEN IN ARBITRAL* 

8 8 $ 8 * 










H 


/ 

t? 


^ 


x 

t 








M' 


#* 










'! 

JO OC 

$ 
%\ 

Sfi 

'# 

J S5 

34! 


















> 


















LK 


}HT i 


"ilSTl 


?I6U' 


riON 




i 

i 

















64 66 68 TO 7t 



8O 



14 76 76 
AMPS. 

FIG. 4. Light on projection screen vs. current; 
8-mm. high-intensity a-c. carbons: arc length, 0.29 
inch. 



decreases as the current through the arc is decreased, but the distribu- 
tion of the light on the screen remains practically unchanged. If 
the current at the arc is decreased very much below the minimum 
recommended current of 75 amperes, the arc will fail to fill the ends 
of the carbons and will cause a variation of the distribution of the 
light 2 not shown by the curves. 



40 



D. B. JOY AND E. R. GEIB 



[J. S. M. P. E. 



If the carbons are not fed together at such a rate as to maintain the 
arc length approximately constant, the position of the arc with respect 
to the mirror, the arc length, and the current will all change at the 
same time. In other words, the changes illustrated in Figs. 2, 3, and 
4 all occur simultaneously, and the result on the screen light is a 
composite of all the curves. Such a composite curve can be cal- 
culated for a given set of con- 
ditions, but actual measure- 
ments are given for one case 
in Fig. 5. 

Fig. 5 shows the change in 
the total light on the screen, 
the fluctuation of the light, 
and the change in the current 
as the arc is allowed to burn 
from a 0.245-inch length to a 
0.58-inch length, without ad- 

3oo| (6o r 1 1 1 justment of the transformer 

the arc controls. The 



500 



200 



J? 



loo 



1 

5^ 20- 



80- 






LlQHT DISTRIBUTION 



.02 



.36 



or 

focal position of the carbon 
for the 0.245-inch length was 
3.84 inches from the reflector, 
corresponding to position C in 
Fig. 2. The light on the pro- 
jection screen decreases rap- 
idly because of the cumulative 
effect of the decrease in the 
current and the change in the 
position of the carbon with 
respect to the reflector. 

Besides the rapid decrease 
light, the lower current 
causes unsteadiness of the 
arc, which is discussed in de- 
tail in a previous paper. 2 Also, if the carbons are allowed to burn 
apart and are then suddenly adjusted to a much shorter arc length, 
the sudden change of current and arc length causes a disturbance 
in the arc which, of course, is transmitted to the light on the 
screen. It is therefore essential, both from the standpoint of steadi- 
ness and total light on the screen, that the arc length be held within 



.// .20 .29 

LENGTH IN INCHES 



FIG. 5. Light on projection screen vs. 
arc length; carbons not feeding; no adjust- 
ment of transformer or arc position: 45 of 
volts, no load on transformer. 



July, 1934] HIGH-INTENSITY ARC AND LIGHT 41 

as close limits as is practicable by the feeding mechanism, and that 
this feeding mechanism be kept in adjustment by the projectionist. 

In addition to the foregoing factors, which are directly related to 
the control of the arc, certain other conditions may affect the steadi- 
ness of the screen illumination. It is assumed that any magnetic 
fields which might cause the arc to burn unsteadily have been taken 
care of in designing the lamp. Therefore, if blowing of the arc is 
observed, evidenced by a fluttering of the light on the screen, the 
drafts in the lamp house should be given some attention. It was 
noted in one theater installation that the rear shutter was so designed 
as to draw the air from the projection lamp through the light shaft 
of the lamp. This caused a blowing of the arc around the forward 
carbon and a noticeable disturbance in the light on the screen. 

A characteristic of the high-intensity a-c. arc which, although not 
directly connected with the light on the screen, is a distinct advantage, 

TABLE I 

Thermocouple Temperature at Film Aperture 

Carbons and Lamp Light on Screen Temp, in C. . 

(Relative) at Aperture 

12-mm. X 8-mm. S.R.A. d-c. Carbons 

30 Amps, in Mirror Arc Lamp 56 525 

8-mm. H.-I. a-c. Carbons 

80 Amps, in H.-I. Mirror 100 630 

Arc Lamp (Full light) 
8-mm. H.-I. a-c. Carbons 

80 Amps, in H.-I. Mirror Arc Lamp 56 425 

(Light and heat reduced by wire screen 
between lamp and aperture) 

is the comparatively low temperature at the film aperture. Table I 
compares the relative screen illuminations obtained with a low- 
intensity d-c. mirror arc and the high-intensity a-c. arc, and the 
corresponding temperatures at the film gate. The temperature was 
recorded by a thermocouple placed at the aperture. No shutter was 
used between the lamp and the projector, and the projector was not 
running. Although producing almost twice as much light on the 
screen as the low-intensity d-c. mirror arc, the high-intensity a-c. 
arc caused a temperature at the film gate of only 630 C. as compared 
with 525 C for the d-c. arc. In order to compare film gate tem- 
peratures for a given screen illumination, a wire grating was placed 
between the high-intensity a-c. lamp and the aperture. The openings 
in the grating were of such size as to allow the same amount of light 
to fall upon the projection screen as from the unscreened low-inten- 



42 D. B. JOY AND E. R. GEIB [J. S. M. P. E. 

sity d-c. arc. In this case the temperature at the film gate was 100 C. 

lower for the high-intensity a-c. arc than it was with low-intensity d-c. 

There has been considerable discussion concerning the possibility 

of a beat or fluctuation in the light on the projection screen from the 





Zro axis 
Current 



ww 



v v 

Low-Intnsity 60 -Cycle Alternating-Current Are 





Zero axis 



A A A A /g^A A A A 
V V V V^" v v V \J 

m <rh -Intensity 60-Cycle Alternating-Current Arc 



M/WWW\mVW\AA/WW 



Zero axis. 




Low-Intensity Reetlflad Current Are 

FIG. 6. Oscillograms of arc current and instantaneous light 
on projection screen; projector shutter not running. 

high-intensity a-c. arc. This idea is based on the results that were 
formerly obtained when the low-intensity a-c. arc was used for pro- 
jection. It will be shown that the present high-intensity a-c. arc 
is not the same as the old type low-intensity a-c. arc with neutral 
cored carbons, but is a new type of arc producing a light on the screen 



July, 1934] HIGH-INTENSITY ARC AND LIGHT 43 

more comparable in wave-form to the light from the low-intensity 
d-c. arc operated by a rectifier. 

Oscillographic pictures of the current and light on the screen with- 
out the shutter running are shown in Fig. 6 for the low-intensity a-c. 
arc, the new high-intensity a-c. arc, and the rectified low-intensity arc. 
The instantaneous light on the screen was measured by means of a 
photoelectric cell and an amplifying system that allowed a linear re- 
lation between the cell current and the output current, which was, 
in turn, recorded on the oscillograph coinciden tally with the instan- 
taneous value of the arc current. 

The curves, of course, represent the fluctuations of the light over 
very short periods of time less than one-fifth of a second as in- 
dicated. A high-intensity a-c. lamp and transformer unit, which 
is typical of the equipment on the market at the present time, was 
used to obtain the curves for the a-c. high-intensity arc. A common 
type of ordinary low-intensity reflecting arc lamp was used with low- 
intensity neutral cored carbons for both the rectified current and the 
alternating current arcs. In other words, the same kind of optical 
system was used with all three varieties of arcs. The rectifier is the 
same as is now used with low-intensity mirror arc lamps in hundreds 
of theaters. 

The direction of the current in the low-intensity a-c. arc changes 
every half cycle in the usual manner. The light emanating from the 
arc, as indicated in Fig. 6, rises to a peak when the carbon that 
is in focus is positive, and decreases and remains at a low value as the 
direction of the current changes and the carbon in focus becomes nega- 
tive for half a cycle. 

With the low-intensity d-c. arc operated by a rectifier, the current 
is unidirectional, but decreases to a zero point during each half cycle. 
The light on the screen rises to a peak at the middle of each half cycle, 
but decreases to about half that value as the current approaches the 
zero point, rising again to a peak, which is not quite so high as that in 
the first half of the cycle, and decreasing to a low value again. In 
other words, there is a fluctuation, but the light during each half 
cycle rises to very nearly the same level. 

The current in the a-c. high-intensity arc, of course, changes its 
direction in the usual way, but the light on the screen is considerably 
different from the light of the low-intensity a-c. arc. Instead of re- 
maining at a low value while the carbon in focus is negative, the light 
rises to approximately the same value as it does when the carbon in 



44 D. B. JOY AND E. R. GEIB [j. s. M. P. E. 

focus is positive, but the shape of the light curve is slightly different. 
In other words, except for certain differences in the shape of the curve, 
the light projected by the high-intensity a-c. arc approximates that 
of the rectified current arc much more closely than it does the light 
of the low-intensity a-c. arc. 

The effect of the light-wave is very noticeable when the shutter 
mechanism is operating. The speed of the shutter is fixed at 1440 
rpm. by the standard film speed of 90 feet per minute. On the other 
hand, the current from the ordinary 60-cycle circuit, or from a single- 
phase rectifier placed in the circuit, goes through a characteristic 
change 3600 times per minute. In other words, the time of opening 
of the shutter does not correspond to an even number of changes in the 




"I" 4 "!"* *"|-*'n tow-lntenalty 

I Shutter OonJ 

* Shutter Cloe< ' 




High-Intensity gQ-Crl tltem.ttiy-Oirrent Are 



AAAAAAAAAAAAA 



nw-Tntanaltr int< t lad-Current Are 



FIG. 7. Oscillograms of instantaneous light on projection screen ; 
two-bladed shutter, 1440 rpm., corresponding to film speed of 90 ft. 
per min. [These oscillograms are of same magnitude as those in 
Fig. 6, although reduced in reproduction.] 

current or the light on the screen. This is illustrated very clearly by 
the oscillograms in Fig. 7, which show the variation of the light in- 
tensity on the screen for the three types of arc with the shutter 
running at approximately 1440 rpm. If it were possible to run the 
shutter at 1800 rpm., which would correspond to a film speed of 
112.5 feet per minute, the shutter openings of the ordinary two-bladed 
shutter would correspond to one-half a cycle in the current and light 
curves, and would give the same amount of light on the screen for 
each shutter opening. Theoretically and actually, with a two-bladed 
symmetrical shutter operating at a speed of 1800 rpm., there would 
be no fluctuation of the light on the screen that could be detected by 



July, 1934] HIGH-INTENSITY ARC AND LIGHT 

the eye even without film in the machine. In other words, the more 
nearly identical in amount and wave-shape the light on the screen is 
during each shutter opening, the less discernible would be the fluctua- 
tions or beats in the light on the screen. 

It can be seen in Fig. 7 that the amount of light on the screen from 
one shutter opening to the next varies enormously in the case of th 
low-intensity a-c. arc. This is due directly to the fact that, as illus- 
trated in Fig. 6, during the half cycle that the carbon in focus is nega- 
tive the light remains at a comparatively low value. On the oth 
hand the light from the high-intensity a-c. arc, although of irregular 
wave-form, is much more nearly constant for each shutter opening 
and corresponds much more closely to the curve of the light obtained 
from the d-c. arc operating on rectified current with the shutter rui 



is the reason for the very decided improvement in steadiness 
over the low-intensity a-c. arc, and for the practical elimination, under 
favorable conditions, of noticeable fluctuation in the light on t 
screen from the high-intensity a-c. arc. In other words, the light- 
curve of the high-intensity a-c. arc, being of nearly the same inten- 
sity during each half of the current cycle, has practically the same 
fluctuation characteristic as that of the low-intensity d-c. arc oper- 
ated by a rectifier. The practical proof of this is obtained by observ- 
ing the projection of the same amount of light from the three 
types of arcs with the shutter running. This has been done in the 
laboratory with a very high degree of illumination on the screen 
and without film in the projector. Observation under such condi- 
tions agrees with the conclusions arrived at from the oscillograms : 
namely, that the light beat or fluctuation of the high-intensity a-c. 
arc is very much less than that of the low-intensity a-c. arc and of 
essentially the same magnitude as that of the low-intensity d-c. arc 
using neutral cored carbons and operated by a rectifier. 

From the standpoint of practical projection, the beat or fluctuation 
of light is so small that under reasonable conditions it can not be con- 
sidered detrimental to the quality of the picture. This was demon- 
strated at a recent meeting of the S. M. P. E. Projection Practice Com- 
mittee, when pictures were projected by a high-intensity a-c. arc. 
One member of the Committee remarked at the time that if he could 
not see the light-beat or fluctuation, it was not there so far as he was 

concerned. 

Factors other than the light source itself exert an influence on the 



46 D. B. JOY AND E. R. GEIB [j. s. M. P. E. 

fluctuation of the light and, if properly taken into consideration, 
will produce the favorable condition referred to before. For example, 
the design of the shutter is very important. It has been found ex- 
perimentally that a three-bladed shutter of the unbalanced type, one 
blade of which is considerably larger than the other blades, causes 
noticeable beat of the light on the screen. It was also noticed that in 
a two-bladed shutter, when one of the blades is larger than the other, 
the beat of the light is more pronounced. In other words, lack of 
symmetry in the shutter will, of itself, introduce a beat with any arc. 
It has been reported that in cases where fluctuation is noticed, it can be 
decreased by stopping down the objective lens and cutting down both 
blades of the two-winged shutter to the point just before the appear- 
ance of shadow-ghost. The average shutter speed is fixed at 1440 
rpm., but in some cases the speed fluctuates considerably because 
of worn gears or parts in the projector mechanism. This variation 
of the speed tends also to produce a beat in the screen light. 

The use of a projection screen that has a highly directional reflec- 
tion characteristic with the very efficient high-intensity a-c. lamps 
now available tends to make the beat more noticeable than when a 
flat white screen is used, which reflects the light evenly in all direc- 
tions. This is probably a function of the light intensity, for in 
observations made in the laboratory with no film in the machine, the 
light beat is noticeable on the directional screen when viewed at a 
direct reflecting angle from the projector, but decreases as the angle of 
observation increases, until it entirely disappears. 

From these practical and theoretical considerations it is believed 
that with a reasonable amount of care in the design of the lamp, 
in the operation of the arc, and in the choice of the light intensity, 
shutter, and type of screen, the high-intensity a-c. arc will find a defi- 
nite place in the projection field in the same manner as other new 
types of arcs, such as the low-intensity mirror arc and the conventional 
high-intensity d-c. arc, which have appeared on the market during the 
past few years. 

REFERENCES 

1 JOY, D. B., AND DOWNES, A. C.: "A New Alternating- Current Projection 
Arc," J. Soc. Mot. Pict. Eng., XXI (Aug., 1933), No. 2, p. 116. 

2 JOY, D. B., AND GEIB, E. R.: "Operating Characteristics of the High-Inten- 
sity Alternating-Current Arc for Motion Picture Projection," /. Soc. Mot. Pict. 
Eng., XXIll (July, 1934), No. 1, p. 27. 

3 JOY, D. B., AND DOWNES, A. C. : "Some Causes of Variations in the Light and 
Steadiness of High-Intensity Carbons," /. Soc. Mot. Pict. Eng., XVI (Jan., 1931), 
No. 1, p. 61 



July, 1934] HIGH-INTENSITY ARC AND LIGHT 47 

4 JOY, D. B., AND DOWNES, A. C. : "Properties of Low-Intensity Reflecting Arc 
Projector Carbons," /. Soc. Mot. Pict, Eng., XVI (June, 1931), No. 6, p. 684. 

DISCUSSION 

MR. RICHARDSON: Will you please describe your observations on the effect 
of shutter speed variation on the screen illumination? 

MR. JOY : Our observations in a theater were as follows : We used a tachome- 
ter to measure the shutter speed and found in one machine that it varied from 
1420 to 1450 rpm. periodically, several times a minute. There was probably 
something worn in the mechanism to make it do that. The periodic change of 
speed made a noticeable variation in light on the screen. 

MR. HARDY : What is the brightness of the effective area of the arc ? Have you 
considered the possibility of supplying the arc possibly by means of a thyratron ; 
from a source having a frequency the same as that of the shutter, so that the dark 
period of the arc would correspond to the dark period of the shutter? 

MR. JOY: The brightness of the effective area of the arc is given in Fig. 1 
of the paper 2 entitled "Operating Characteristics of High-Intensity A-C. Arcs for 
Motion Picture Projection." The maximum intrinsic brilliancy at the center of 
the crater was 360 candles per sq. mm., tapering off to lower values at the edges of 
the effective area. 

The suggestion of supplying the arc by a thyratron from a source having 
frequencies the same as the shutter, so that the dark period of the arc would 
correspond to the dark period of the shutter, should have very interesting possibili- 
ties. A machine has been developed for changing the 60-cycle alternating current 
to a current of higher frequency. Such a machine is on the market at the present 
time, and does practically eliminate any flicker that may be due to the alternation 
of the current, even with no film in the machine. 

MR. PALMER: How much of the light comes from the crater, and how much 
from the flame? That question has a bearing on the efficiency of the whole set-up. 
It seems to me that the light coming from the carbon that does not face the mirror 
is entirely lost. How much light is lost from the crater of that carbon? 

MR. JOY: The light at and around the carbon not at the focus of the reflector 
is equal to the light at and around the carbon at the focus. The carbons are 
identical in composition. Of course, if the light from the carbon not at the focus 
could be directly utilized we should have a more efficient system. According 
to the oscillograms in Figs. 6 and 7, when the carbon at the focus is negative the 
light still rises to almost as high a value as it does when the carbon at the focus is 
positive, so that we may be indirectly using some of the light from the carbon not 
at the focus. 

We have no data on the proportion of the useful light that comes from the 
incandescent carbon or from the concentrated flame close to the carbon. The 
intrinsic brilliancy curve shows a maximum of 360 candles per sq. mm. at the 
center of the curve. The intrinsic brilliancy of the low-intensity d-c. positive 
carbon that is, incandescent carbon is approximately 160 candles per sq. mm. 
What we probably have in this arc is the light from the gases that lie close to 
the carbons themselves superimposed on the light from the incandescent carbon 
and core material. 



AN IMPROVED SYSTEM FOR NOISELESS 
RECORDING* 

G. L. DIMMICK AND H. BELAR** 



Summary. A new system of noisless recording that makes it possible to increase 
the volume range considerably without introducing distortion has been developed. 
The sound waves are amplified and split into two halves by a special mask in the re- 
cording optical system. The two half -waves are recorded 180 degress out of phase on 
separate parts of the sound track. The reproducing system utilizes a photoelectric cell 
having two cathodes connected in push-pull. Ground noise is reduced to a minimum 
because only the area occupied by the the recorded waves is transparent, and when 
there is no modulation the track is completely back. 

The reduction of ground noise in film recording has engaged the 
attention of engineers for many years. The incentive has been to 
increase the range of volume capable of being recorded, and to sup- 
press the extraneous background noise to a level below the 
threshold of hearing. Both these factors are tremendously important 
in creating the illusion of reality, which, of course, is the ultimate ob- 
jective of any reproducing system. Several methods have been de- 
vised for reducing ground noise to a limited extent. It is the purpose 
of this paper to describe a practical variable-width sound recording 
system that permits the reduction of ground noise to an absolute 
minimum, without introducing distortion. The system does not re- 
quire auxiliary recording equipment, nor does it require special care 
in recording or processing. 

The two principal causes of extraneous noise in film records are the 
film grains in the exposed portion, and foreign particles or scratches 
in the clear portion. Because of the random distribution of silver 
grains and groups of grains, the transmission through the dense part 
of the sound track varies at audible frequencies, producing a high- 
pitched hiss that sounds very much like the hiss due to "thermal 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** RCA Victor Company, Camden, N. J. 

48 



IMPROVED NOISELESS RECORDING 



49 



agitation" in resistors, or "shot effect" in vacuum tubes. At the 
recommended print density for variable-width records, the hiss is of 
extremely low amplitude; foreign particles and scratches on the 






FIG. 1. Four types of vari- 
able-amplitude sound track. 

transparent portion of the sound track form the most annoying cause 
of ground noise. The photoelectric cell is unable to distinguish be- 
tween the reduction of light due to a decrease of width of the trans- 
parent portion of the track and the reduction of light due to opaque 
particles in the clear track. 




FIG. 2. A new type of push-pull track. 

The average width of the clear portion in either of the variable- 
width tracks A or C, Fig. 1, is constant and equal to half the track 
width. Since the ground noise remains constant, the ratio of noise 



50 



G. L. DIMMICK AND H. BELAR 



[J. S. M. P. E. 



to signal increases as the signal is reduced. Tracks B and D, Fig. 1, 
were made with the biasing system of noise reduction. In that system a 
portion of the signal is rectified, and is caused to operate either a 
shutter vane or a biasing winding on the recording galvanometer in such 
a way that the clear portion of the track is reduced to a width that 
will just accommodate the modulation. When there is no modula- 
tion the clear track shrinks to a width of about four mils. The system 
affords a considerable reduction of the ground noise, and is a consider- 
able improvement over previous systems. The biasing system is, how- 
ever, inherently limited in the extent to which it can reduce film noise 
without introducing distortion. If the biasing current were allowed 
to actuate the galvanometer freely, without a timing circuit, an au- 
dible distortion would be superimposed upon the signal, because the 





FIG. 3. Recording optical system. 

envelope of many sounds occurring in nature is a wave of audible 
frequency. If the timing circuit should not act quickly enough, the 
narrow track could not accommodate the beginnings of sounds that oc- 
curred suddenly, thus causing the first part of the sound to be dis- 
torted. In practice, the biasing system is utilized to reduce ground 
noise only to such an extent that the accompanying distortion is 
negligible. 

A new type of sound track, which permits the reduction of ground 
noise to the theoretical minimum, is shown in Fig. 2. Only the area 
actually occupied by the sound record is transparent, which means 
that the ratio of the ground noise to the signal is constant, regardless 
of the amplitude. The recording optical system used in making the 
track is shown in Fig. 3. The only change that has been made in the 
standard Photophone recording optical system is the replacement of 



July, 1934] 



IMPROVED NOISELESS RECORDING 



51 



the single triangular mask by a mask having two triangles. An opti- 
cal image of two opposing triangles is formed at the slit after being re- 
flected from the galvanometer mirror, as shown in Fig. 2. The 
apexes of the triangular images are coincident with the center of the 
slit and are spaced apart half the length of the slit. When a signal is 
impressed upon the galvanometer the triangular light beams vibrate 
in a vertical plane and record two symmetrical tracks, one of which 
carries the positive half, the other the negative half, of the sound 
waves. The axes of the two component tracks are located a quarter 
of the total width of the track from each edge. The purpose of this 
is to assure proper scanning with low modulation and the proper 
separation of the two halves of the reproducing light beam in case of 
either a slight weaving of the film or a slight misalignment of the track. 




FIG. 4. Reproducing optical system. 

The axes of the two half-tracks might be made to coincide at the cen- 
ter of the track, but it would be practically impossible to separate 
them later. The axes might also be placed at the two outside edges 
of the track, but then there would be less assurance of proper scanning 
with low modulation. 

In practice, the recording system is quite simple to operate and 
adjust. The points of the two triangles may be made to lie upon a 
line parallel to the slit by a rotary adjustment of the barrel containing 
the aperture. The points are brought to the center of the slit by a 
vernier adjustment of the galvanometer about its horizontal axis. 
If, for any reason, the latter adjustment were either made incorrectly 
or accidentally spoiled, no distortion would be introduced. The 
only effect would be a slight increase of ground noise. 

Both the optical and the electrical systems for reproducing this type 



52 



G. L. DIMMICK AND H. BELAR 



[J. S. M. P. E. 



of sound track are shown in Fig. 4. A beam of light 0.084 inch long 
and 0.001 inch wide is projected on the film 44 by means of a standard 
reproducing optical system 47 and a 10-volt, 5-ampere lamp 45. A 
cylindrical lens 48 forms an image of the width of the sound track 
upon the two cylindrical lenses 49 and 50. In the other plane, light 
from the reproducing optical system is allowed to expand to a height 
of about an inch. Lenses 49 and 50 each form an image of lens 48 
upon the two cathodes 52 and 53, of the photoelectric cell 46. By 
means of such an arrangement the two images of lens 48 are sepa- 
rated, each containing the light transmitted through half the track, 
since the center of the track coincides with the dividing line between 




FIG. 5. A 9000-cycle negative made 
with the push-pull system. 



the two adjacent cylindrical lenses. The system produces variations 
in the intensity of the light striking the cathodes, corresponding to 
variations in the width of the clear portion of the sound track. As 
shown in Fig. 4, the cathodes are connected to the primary terminals 
of a transformer. The anode is connected through a battery to the 
center of the transformer. The secondary is connected to the repro- 
ducing amplifier. It is obvious that the two halves of the sound 
waves, which were recorded 180 degrees out of phase, are recombined 
in the proper phase by the push-pull transformer. 

In addition to its inherent freedom from ground noise, the push- 
pull sound track has other advantages of equal importance. The 



July, 1934] IMPROVED NOISELESS RECORDING 53 

finite width and the spreading of the photographic image of the re- 
cording light beam are responsible for filling in the valleys and re- 
ducing the density of the peaks of the high-frequency waves. The 
push-pull track improves the condition in two ways. As shown in 
Fig. 5, the negative is composed only of peaks that are separated from 
each other by clear spaces equal in width to a half wavelength. In 
order to make a good print it is necessary to make the peaks quite 
dense. In the conventional system of variable- width recording, a 
compromise between light peaks and dense valleys must determine 
the density of the negative. Elimination of the valleys from the 
negative makes it possible to increase the negative density and 
thereby obtain better prints. 

Another important advantage of the push-pull sound recording 




FIG. 6. Push-pull recording of keys jingling. 

system is the elimination of a kind of distortion that results from 
improperly processing the variable-width films. When high fre- 
quencies recorded on a sound negative are attenuated because of the 
finite width of the slit and the limited resolution of the film, a reduc- 
tion of the average transmission also results. If this condition were 
allowed to persist, a certain amount of distortion would accompany 
all high-frequency sounds that varied in amplitude at audible fre- 
quencies. The distortion would be of the form of an extraneous 
noise produced by the envelope of the high frequencies, as shown in 
Fig. 6. By properly determining the negative and print density it 
is possible to avoid such distortion in any type of variable- width track. 
The push-pull system completely eliminates all the distortion that is 
not already printed out. The reason may be seen in Fig. 6. The 



54 IMPROVED NOISELESS RECORDING 

positive and negative waves of the high frequencies are 180 degrees 
out of phase, and so are added in the push-pull transformer; but the 
envelopes of amplitude for the two tracks are in phase, thereby can- 
celling the distortion in the transformer. 

Acknowledgment is due Messrs. E. W. Kellogg and L. T. Sacht- 
leben for their contributions to the development of the new system for 
noiseless recording. 

DISCUSSION 

MR. WENTE: How much free area is there between the two sound tracks? 
When there is no free space the method would appear to impose severe require- 
ments with regard to weaving during reproduction. How much weaving can you 
tolerate with the records you have made? 

MR. DIMMICK: The axes of the two sound tracks are half the width of the 
whole track, or 35 mils apart; therefore, for low modulation they are spaced 35 
mils apart. However, for 100 per cent modulation the tracks just come together 
at the center, but do not overlap. 

The triangles are so made that the tracks can not overlap; but in the record 
that you have just heard, there was no space between the half-tracks when the 
modulation was 100 per cent. 

MR. WENTE: That is at 100 per cent modulation; if there were any weaving 
you would have "spilling over" from one side to the other, would you not? 

MR. DIMMICK: Yes. 

MR. KELLOGG: It should be understood that the fact that there was no clear- 
ance between the two half-tracks in this 51m, or, in other words, no margin to 
allow for weaving, means simply that this particular record happens to have been 
made that way. There is nothing inherent in the system that precludes a reason- 
able allowance for weaving. 



COMMITTEES 

OF THE 

SOCIETY OF MOTION PICTURE ENGINEERS 



J. FRANK, JR. 
H. GRIFFIN 



P. D. BREWSTER 



ADMISSIONS 

H. G. TASKER, Chairman 
R. F. MITCHELL 



COLOR 

W. V. D. KELLEY, Chairman 
C. TUTTLE, Vice- Chairman 
R. M. EVANS 
L. A. JONES 



E. HUSE 

H. M. STOLLER 



J. F. KlENNINGER 



H. GRIFFIN 



CONVENTION 
W. C. KUNZMANN, Chairman 

J. H. KURLANDER 



M. W. PALMER 



G. A. CHAMBERS 
O. B. DEPUE 



HISTORICAL 
W. E. THEISEN, Chairman 

J. A. DUBRAY 

W. V. D. KELLEY 



G. E. MATTHEWS 
T. RAMSAYE 



LABORATORY AND EXCHANGE PRACTICE 

R. F. NICHOLSON, Chairman 



J. I. CRABTREE 
J. CRABTREE 
R. M. EVANS 



Laboratory Practice 

D. E. HYNDMAN, Chairman 
E. HUSE 

C. L. LOOTENS 

D. MACKENZIE 
R. F. MITCHELL 



W. SCHMIDT 
V. B. SEASE 
J. H. SPRAY 



A. S. DICKINSON 
G. C. EDWARDS 
A. HIATT 



Exchange Practice 

T. FAULKNER, Chairman 
J. S. MACLEOD 
N. F. OAKLEY 



H. RUBIN 
J. H. SPRAY 
L. L. STEELE 



55 



56 



COMMITTEES OF S. M. P. E. 



[J. S. M. P. E. 





MEMBERSHIP 






E. R. GEIB, Chairman 




Publicity 


C. W. HANDLEY 


M. RUOT 


D. M. BALTIMORE 


R, H. McCULLOUGH 


S. S. A. WATKINS 


J. J. FINN 


E. HUSE 




T. RAMSAYE 


P. MOLE 


France 


F. H. RICHARDSON 
W. WHITMORE 


Minneapolis 


L. J. J. DIDIEE 
L. G. EGROT 




C. L. GREENE 


F. H. HOTCHKISS 


Itinerant 




J. MARETTE 


E. AUGER 


New York 




K. BRENKERT 


T. FAULKNER 


Germany 


W. C. KUNZMANN 


H. GRIFFIN 


W. F. BlELICKE 


D. McRAE 


W. W. HENNESSY 


H. J. LUMMERZHEIM 


H. H. STRONG 


T. E. SHEA 


K. NORDEN 




J. H. SPRAY 




Boston 




Hawaii 


J. S. CIFRE 


Rochester 


L. LACHAPELLE 




D. McMASTER 




Camden 




India 


J. FRANK, JR. 


Washington, D. C. 


H. S. MEHTA 




H. T. COWLING 


D. L. MISTRY 


Chicago 


N. GLASSER 


M. B. PATEL 


E. COUR 






J. H. GOLDBERG 


A ustria 


Japan 




P. R. VON SCHROTT 


T. NAGASE 


Cleveland 




Y. OSAWA 


R. E. FARNHAM 


Canada 




L. J. SHAFER 


F. C. BADGLEY 


New Zealand 


V. A. WELMAN 


C. A. DENTELBECK 


C. BANKS 




G. E. PATTON 




Detroit 




Russia 


M. RUBIN 


China 


E. G. JACHONTOW 




W. D. COOLEY 




Hollywood 


R. E. O'BOLGER 


Scotland 


C. DREHER 




R. L. JAY 


H. C. SILENT 


England 






E. E. LAMB 





NON-THEATRICAL EQUIPMENT 
R. F. MITCHELL, Chairman 



H. A. ANDERS 
D. BEAN 
E. W. BEGGS 
W. B. COOK 


H. T. COWLING 
H. DEVRY 
R. E. FARNHAM 
H. GRIFFIN 
R. C. HOLSLAG 


A. SHAPIRO 
C. TUTTLE 
A. F. VICTOR 
V. C. ARNSPIGER 



R. E. FARNHAM 
A. C. HARDY 
G. E. MATTHEWS 



PAPERS 

J. O. BAKER, Chairman 
P. A. McGuiRE 
P. McNicoL. 



E. O. SCRIVEN 
H. C. SILENT 
H. G. TASKER 



July, 1934] 



COMMITTEES OF S. M. P. E. 



57 





PROGRESS 






J. G. FRAYNE, Chairman 




W. P. BlELICKE 


J. CRABTREE 


G. E. MATTHEWS 


L. BUSCH 


J. A. DUBRAY 


H. MEYER 


A. A. COOK 


R. E. FARNHAM 


G. F. RACKETT 


R. M. CORBIN 


W. C. HARCUS 


S. S. A. WATKINS 




PROJECTION PRACTICE 






H. RUBIN, Chairman 




T O. BAKER 


E. R. GEIB 


R. H. MCCULLOUGH 


J ' 

T. C. BARROWS 


S. GLAUBER 


R. MlEHLING 


G. C. EDWARDS 


C. L. GREENE 


P. A. McGuiRE 


J. K. ELDERKIN 


H. GRIFFIN 


F. H. RICHARDSON 


J. J. FINN 


J. J. HOPKINS 


V. A. WELMAN 




W. C. KUNZMANN 






PROJECTION SCREENS 






J. H. KURLANDER, Chairman 




H. GRIFFIN 


E. HUSE 


S. K. WOLF 




W. F. LITTLE 






PROJECTION THEORY 






A. C. HARDY, Chairman 




R. E. FARNHAM 


W. F. LITTLE 


C. M. TUTTLE 


H. P. GAGE 




W. B. RAYTON 



J. J. FINN 



P. H. EVANS 
R. M. EVANS 
O. SANDVIK 



W. H. CARSON 
E. K. CARVER 
L. E. CLARK 
J. A. DUBRAY 
P. H. EVANS 
R. M. EVANS 
R. E. FARNHAM 
C. L. FARRAND 



PUBLICITY 

W. WHITMORE, Chairman 
G. E. MATTHEWS 
P. A. McGuiRE 

SOUND 

L. W. DAVEE, Chairman 
East Coast Subcommittee 

M. C. BATSEL, Chairman 
H. B. SANTEE 
W. A. MACNAIR 

West Coast Subcommittee 
H. C. SILENT, Chairman 

STANDARDS 

M. C. BATSEL, Chairman 
H. GRIFFIN 
A. C. HARDY 
R. C. HUBBARD 
L. A. JONES 
N. M. LAPORTE 

C. W. LOOTENS 

D. MACKENZIE 
G. F. RACKETT 
W. B. RAYTON 



F. H. RICHARDSON 



E. I. SPONABLE 
R. O. STROCK 
S. K. WOLF 



C. N. REIFSTECK 
H. RUBIN 
H. B. SANTEE 
V. B. SEASE 
J. L. SPENCE 
E. I. SPONABLE 
H. M. STOLLER 
S. K. WOLF 



BOOK REVIEWS 

Movie Making Made Easy. W. J. Shannon. Moorfield & Shannon, Nutley, 
N. J. 219 pp. 

The preface of this handbook for the cine amateur states: "It has been esti- 
mated that there are some 300,000 home movie camera owners and 400,000 pro- 
jector owners in this country alone. Serial numbers on equipment produced by 
leading manufacturers of cine equipment confirm this estimate." With these 
facts in mind, the author has attempted to compile into one book information 
that would interest not only this group but others contemplating joining it. The 
booklet is a compilation of tersely written chapters covering a very wide range of 
subject matter. In some cases it seems as though the brevity is too great even 
though this quality is most distinctly a virtue in any modern book. Some of the 
subjects treated are : The Home Theater, Amateur Movie Clubs, Making Up for 
the Camera, Photochemical Reactions, Reversal Process Explained, Aerial Photog- 
raphy, and Backyard Science with a Movie Camera. Practice and theory are 
somewhat mixed together in the text, and a more logical arrangement of subject 
matter might have been possible. 

G. E. MATTHEWS 

Filming with the Cine Kodak Eight (Filmen mit Cine Kodak Acht). A. Stuhler. 
W. Knapp, Halle, Germany. 

This little book contains an excellent discussion of the working characteristics 
of this 8-mm. camera, including many interesting illustrations and self-explana- 
tory diagrams. In addition to general directions for use, information is given on 
the following subjects: artificial illumination, the use of teleobjectives, titling, 
making a picture story, editing, and splicing. 

G. E. MATTHEWS 

Signals and Speech in Electrical Communication. J. Mills. Harcourt, Bract 
& Co., New York, N. Y., 1934. 281 pp. 

Without a diagram, an equation, a formula, or a chart, this book nevertheless 
portrays the discoveries, inventions, and principles that underly the many forms 
of communication of which the talking motion picture is but one. 

"Twenty years ago a telegram was an event in the ordinary household, and 
the telephone was not the universal necessity it is today. Phonographs ground 
out a canned music all their own; motion pictures were silent, and there was no 
radio broadcasting. One couldn't telephone across America, much less across 
the Atlantic. There were no radios to ships at sea and airplanes in flight; no 
transmission of pictures by wire; and no prospect of television." 

Intending his work for the interested but untechnical layman the author 
employs a number of unusually effective similes that tend to compensate for 
occasional obscurity resulting from inadequate editing. 

H. G. TASKER 

68 



SOCIETY ANNOUNCEMENTS 

STANDARDS COMMITTEE 

At a meeting held at the Hotel Pennsylvania, New York, N. Y., on June 6th, 
the preliminary proofs of the revised Standards Booklet were carefully studied 
and corrected. New proofs are in process of being made for distribution to the 
members of the Committee for final vote on their acceptability for publication in 
the JOURNAL and subsequent recommendation to the Board of Governors for 
validation and submission to the American Standards Association. 

Further attention was given to the comments of the German standardizing 
body on a number of the proposals of the S. M. P. E. Standards Committee with 
the thought of reconciling as many of the divergent opinions as possible in the re- 
vision of the Standards Booklet. 

AMERICAN STANDARDS ASSOCIATION 

At the last meeting of the Board of Governors, at Atlantic City, N. J., April 
22nd, provision was made and the necessary funds appropriated to enable the 
S. M. P. E. to become an Associate Member of the American Standards Associa- 
tion. This is a new grade of membership in the A. S. A., created for the purpose 
of enabling organizations like the S. M. P. E. to participate more intimately in the 
work of the Association. Members in the Associate class are entitled to all the 
privileges of Member-Bodies except representation upon the Standards Council. 

BOARD OF GOVERNORS 

The next meeting of the Board of Governors will be held on July 16th, at the 
Westchester Country Club, Rye, N. Y. Among other items on the agenda, the 
nominations for officers for 1935 will be completed and plans will be initiated for 
the Fall Convention to be held at the Hotel Pennsylvania, New York, N. Y., 
October 29th-November 1st. 



The Society regrets to announce* the deaths of 

C. Francis Jenkins 
Honorary Member of the Society 
June 6, 1934 

and 

J. Elliott Jenkins 
June 9, 1934 



* A full account of the contributions of Mr. C. Francis Jenkins to radio, motion 
picture engineering, and television will be published in a forthcoming issue of the 
JOURNAL. 

59 



STANDARD S. M. P. E. 

VISUAL AND SOUND TEST REELS 

Prepared under the Supervision 

OF THE 
PROJECTION PRACTICE COMMITTEE 

OF THE 
SOCIETY OF MOTION PICTURE ENGINEERS 



Two reels, each approximately 500 feet long, of specially pre- 
pared film, designed to be used as a precision instrument in 
theaters, review rooms, exchanges, laboratories, and the like 
for testing the performance of projectors. The visual section 
includes special targets with the aid of which travel-ghost, 
lens aberration, definition, and film weave may be detected 
and corrected. The sound section includes recordings of 
various kinds of music and voice, in addition to constant 
frequency, constant amplitude recordings which may be used 
for testing the quality of reproduction, the frequency range 
of the reproducer, the presence of flutter and 60-cycle or 96- 
cycle modulation, and the adjustment of the sound track. 
Reels sold complete only (no short sections). 

PRICE $37.50 FOR EACH SECTION, 
INCLUDING INSTRUCTIONS 

(Shipped to any point in the United States) 

Address the 

SOCIETY OF MOTION PICTURE ENGINEERS 

HOTEL PENNSYLVANIA 
NEW YORK, N. Y. 



JOURNAL 



OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 

Volume XXIII AUGUST, 1934 Number 2 



CONTENTS 

Page 

On the Realistic Reproduction of Sound with Particular Refer- 
ence to Sound Motion Pictures . . H. F. OLSON AND F. MASSA 63 

Sixteen-Millimeter Sound Pictures in Color 

C. N. BATSEL AND L. T. SACHTLEBEN 82 

A 16-Mm. Sound Recording Camera 

C. N. BATSEL, L. T. SACHTLEBEN, AND G. L. DIMMICK 87 

Continuous Optical Reduction Printing A. F. VICTOR 96 

A Non-Slip Sound Printer C. N. BATSEL 100 

Optical Reduction Sound Printing 

G. L. DIMMICK, C. N. BATSEL, AND L. T. SACHTLEBEN 108 

Book Review 117 

Officers and Governors of the S. M. P. E 118 

Society Announcements 121 



JOURNAL 

OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 



SYLVAN HARRIS, EDITOR 

Board of Editors 
J. I. CRABTREE, Chairman 

O. M. GLUNT A. C. HARDY L. A. JONES 

J. O. BAKER 



Subscription to non-members, $8.00 per annum; to members, $5.00 per annum, 
included in their annual membership dues; single copies, $1.00. A discount 
on subscriptions or single copies of 15 per cent is allowed to accredited agencies. 
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton 
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y. 

Published monthly at Easton, Pa., by the Society of Motion Picture Engineers 

Publication Office, 20th & Northampton Sts., Easton, Pa. 
General and Editorial Office, Hotel Pennsylvania, New York, N. Y. 
Entered as second class matter January 15, 1930, at the Post Office at Easton, 
Pa., under the Act of March 3, 1879. Copyrighted, 1934, by the Society of 
Motion Picture Engineers, Inc. 

Papers appearing in this Journal may be reprinted, abstracted, or abridged 
provided credit is given to the Journal of the Society of Motion Picture Engineers 
and to the author, or authors, of the papers in question. Exact reference as to 
the volume, number, and page of the Journal must be given. The Society is 
not responsible for statements made by authors. 



Officers of the Society 

President: ALFRED N. GOLDSMITH, 444 Madison Ave., New York, N. Y. 
Executive Vice-President: HAROLD C. SILENT, 7046 Hollywood Blvd., Los 

Angeles, Calif. 

Engineering Vice-P resident: LOYD A. JONES, Kodak Park, Rochester, N. Y. 
Editorial Vice-President: JOHN I. CRABTREE, Kodak Park, Rochester, N. Y. 
Financial Vice-President: OMER M. GLUNT, 463 West St., New York, N. Y. 
Convention Vice-President: WILLIAM C. KUNZMANN, Box 400, Cleveland, Ohio. 
Secretary: JOHN H. KURLANDER, 2 Clear-field Ave., Bloomfield, N. J. 
Treasurer: TIMOTHY E. SHEA, 463 West St., New York, N. Y. 

Governors 

EUGENE COUR, 1029 S. Wabash Ave., Chicago, 111. 
HERFORD T. COWLING, 7510 N. Ashland Ave., Chicago, 111. 
ARTHUR S. DICKINSON, 28 W. 44th St., New York, N. Y. 
RALPH E. FARNHAM, Nela Park, Cleveland, Ohio. 
HERBERT GRIFFIN, 90 Gold St., New York, N. Y. 
EMERY HUSB, 6706 Santa Monica Blvd., Hollywood, Calif. 
WILBUR B. RAYTON, 635 St. Paul St., Rochester, N. Y. 
HOMER G. TASKER, 41-39 38th St., Long Island City, N. Y. 



ON THE REALISTIC REPRODUCTION OF SOUND WITH 

PARTICULAR REFERENCE TO SOUND MOTION 

PICTURES* 

H. F. OLSON AND F. MASSA** 

Summary. The criteria for realistic reproduction of sound are discussed, showing 
how directional sound-collecting and dispersing systems may be employed to give 
results comparable with those of an ideal binaural system of reproduction. The use of 
a directional sound-collecting system, together with a directional sound-dispersing 
system, establishes: a "center of gravity" of the action; an illusion of depth or 
perspective; an acoustical or reverberation characteristic compatible with the picture; 
a large ratio of direct to reflected sound in the theater, emphasizing the acoustical 
properties of the theater; in musical reproduction, a correct balance and reverberation 
characteristic by the use of the two parameters. 

INTRODUCTION 

To achieve realism in a sound-reproducing system, three condi- 
tions must be fulfilled: first, the frequency range must be such 
as to include all the audible components of the various sounds to 
be reproduced; second, the volume range must be such as to permit 
distortionless reproduction of the entire range of intensity associated 
with the sounds; third, the reverberation and binaural characteristic 
of the original sound must be preserved. It is only natural that most 
of the developments during the past decade have been concerned 
with the first two conditions, as it is quite obvious that those condi- 
tions should be satisfied before attempting a solution of the last 
condition. 

During the past few years, the frequency and volume ranges of 
sound recording and reproducing equipment have been improved 
to such an extent as to permit serious thought on the problem of 
binaural reproduction. A brief discussion will be given of several 
methods now available for lending added realism to reproduced 
sounds, keeping in mind the particular requirements that must be 
fulfilled in sound motion picture reproduction. It must also be under- 
stood that from an acoustical point of view there are, fundamentally, 
two different and distinct types of scenes to be considered. First 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** RCA Victor Co., Camden, N. J. 

63 



64 



H. F. OLSON AND F. MASSA 



[J. S. M. P. E. 



are those in which the action and sound are intimately related; and 
second are the scenes in which the sound effects are incidental. 
The first group, of course, includes the great majority of motion pic- 
tures; whereas the latter includes such pictures as are concerned with 
scenic views in which the orchestral accompaniment has no direct re- 
lation to the scene, but serves only to create a suitable mood in the 
audience. 



' RECORDING ' 

r c 



'CHANNEL'!-"' 



SET 
STUDIO 

o 

MJ fa R 
DUMMY 



THEATRE 



L ! RCPRODUCING ! 

. /~l_l AKIfc.fC-1 "I* f 



CHANNEL "L" 



J REPRODUCING | | 

"" CHANNEL -R- 1 - 



AUDITOR 

FIG. 1. Schematic arrangement of an ideal bin- 
aural sound -reproducing system. 



(A) Ideal System of Reproduction. An ideal binaural sound- 
reproducing system is shown schematically in Fig. 1, which indicates 
that the desired objective is attained by effectively transferring the 
auditor to the point of scenic action through the intermediary of 
a double recording and reproducing channel. Two microphones M R 
and M L simulate the ears of a dummy, each receiving the com- 
ponent of the original sound that would normally be received were 
the dummy a human being. Each component is recorded on a 
separate sound track and reproduced through a separate audio 



Aug., 1934] 



REPRODUCTION OF SOUND 



65 



channel, each channel terminating in a high-quality telephone re- 
ceiver. Each of the receivers is placed on the proper ear by the 
auditor, and the sound produced in each of his ears will be identical 
to what would have been produced at the original set had he been 
there at the time. 

The advantages of this system are quite obvious; the binaural 
effect is practically perfect, and the reverberation characteristic of 
the set (which should be designed to conform to the scene) is trans- 
ferred unadulterated to the listener. 

There are two serious disadvantages to this ideal system in addition 
to the requirement for a double channel. In the first place, a set of 
ear phones is required for each member of the audience, which must 
be worn throughout the performance, and would not be tolerated by 
most persons. Second, each listener should be in the same position 
relatively to the scene as the 
dummy was relatively to the 
original set. Such a condition 
is obviously quite impossible of 
realization, and consequently 
those members of the audience 
who are somewhat removed 
from the screen will recognize a 
binaural effect not in accord with 
their distances from the scene. 
It appears, therefore, that the 
practical limitations of the ideal 
system render it undesirable for 
commercial application. 

(B) Approximation to Ideal 
System (Multi-Channel System) . 
It has been stated that in an 
ideal binaural reproducing sys- 
tem the ears of the auditor 

must be effectively transferred to the original scene of action. A 
system for effectively transferring the original sources of sound 
from the studio to the theater stage is shown schematically in 

Fig. 2. A large number of microphones (Mi, M 2 , ) cover 

the entire area over which the action is taking place. The sound 
picked up by each microphone is recorded on a separate channel, 
each channel later feeding a separate loud speaker (5 b 5 2 , ). 




STAGE 

FIG. 2. Effective transfer of sound 
sources to a theater stage. 



66 H. F. OLSON AND F. MASSA [j. s. M. P. E. 

The loud speakers are arranged on the stage in the same positions as 
the microphones on the original set. * 

The best application for such a system would be in those produc- 
tions in which music is the essential part of the entire sound. In 
particular, a symphonic arrangement in which the picture accompani- 
ment serves only to depict the meaning of the selection is admirably 
adapted to such a system. The orchestra would, figuratively, be 
transported bodily to the stage of the theater, and the location of 
each instrument of the group could be easily detected. The large 
number of channels required is the most serious handicap of the 
system. Attempts to reduce the number of channels have been made, 
and at a recent demonstration at New York City, Dr. Harvey 
Fletcher 1 of the Bell Telephone Laboratories showed the improvement 
over a single-channel system that could be attained by using only 
three channels. 

The application of the multi-channel system to the theater will 
require drastic changes in the present technic of sound motion pic- 
ture reproduction. If several sound tracks are to be recorded on 
the same film it is obvious that a wider film will become necessary, 
and it is improbable that such a change will be made. 

In addition to the objections that arise from the need of several 
channels, two other conditions tend to operate against the ideality 
of the system. The first arises from the fact that the acoustical 
characteristic of the theater is superimposed upon that of the set. 
That may not be serious in some cases, but in others, particularly 
outdoor scenes, the reverberation of the theater may detract consider- 
ably from the naturalness of the sounds. Another objection arises 
from the necessity of requiring that the sound sources be spread far 
apart for the best effect. That means that the picture that is being 
reproduced should be spread out to cover the same distance occupied 
by the sound sources; otherwise the sounds will appear to come 
from "off stage" instead of from the picture. 

(C) Approximation to Ideal System (Single- Channel System). The 

* Another system of stereoacoustical reproduction has been suggested by J. E. 
Volkmann. The stage should be made ideal for the collection of sound, and the 
auditorium should be made ideal for the dispersion of sound. For stereoacoustical 
reproduction, the collecting microphones and the corresponding loud speakers 
should be located in the imaginary plane separating the two sections. This 
concept is different from the ordinary ones in which the auditor is transported 
to the scene of action, or the action transported to the auditorium. 



Aug., 1934] 



REPRODUCTION OF SOUND 67 



most practical solution of the problem would obviously be one in 
which a single channel is employed for recording and reproducing. 
To what extent can a single-channel system be made to approach 
a solution of the problem? First, consider what happens when both 
ears are used in listening. In the first place, the auditor is able to 
judge the direction and apparent distance of the source and, second, to 
focus his attention upon the main source of sound and subconsciously 
attenuate the incidental noises that may be present. The latter 
characteristic of binaural hearing is perhaps the more important 
of the two, as it acts to enhance intelligibility, which is undoubtedly 
the most important factor of the ability to understand. The dis- 
crimination against undesired sounds that can be realized with a 
binaural reproducing system may be attained with a single-channel 
system by employing a directional pick-up; and it will be shown 
later how the apparent distance of the source of sound is pre- 
served by using a directional pick-up. By employing a direc- 
tional dispersion system in the theater, the acoustical characteristic 
of the auditorium will not mask the reverberation characteristic 
of the recording to such an extent as a non-directional reproduc- 
ing system. 

The advantages of directional systems for collecting and dispersing 
sound will be outlined more in detail in the sections that follow, and 
the discussions will indicate the extent to which they enhance 
the artistic quality and naturalness of sound motion picture re- 
production. 



COLLECTION OF SOUND 



(A) Collection of Sound in Reverberant Rooms; Direct and Gener- 
ally Reflected Sound. When a source of sound is caused to act in a 
room, the first sound that strikes a collecting system placed in the 
room is the sound that comes directly from the source without reflec- 
tion from the boundaries. Following that comes sound that has 
been reflected once, twice, and so on; meaning that the energy 
density of the sound increases with the time, as the number of re- 
flections increase. Ultimately, the absorption of energy by the 
boundaries equals the output of the source, and the energy density 
at the collecting system no longer increases; this is called the steady- 
state condition. Therefore, at a given point in a room there are two 
distinct sources of sound: namely, (1) the direct, and (2) the generally 
reflected sound. For rooms that do not exhibit abnormal acoustical 



68 



H. F. OLSON AND F. MASSA 



[J. S. M. P. E. 



characteristics, it may be assumed that the ratio* of the reflected 
to the direct sound represents the effective reverberation 2 of the 
collected sound. 

(B) Performance of Directional and Non-Directional Collecting 
Systems in Reverberant Rooms. Consider a sound-collecting system, 
the efficiency of reception of which may be characterized as a func- 
tion of the direction with respect to some reference axis of the system. 
(The non-directional collecting system is a special case of the direc- 



/RANDOM 
/REFLECTED 
/COMPONENT 




COLLECT 
5Y5TEM 



FIG. 3. Directional sound-collecting system. 

tional system in which the efficiency of reception is the same in all 
directions.) The output of the microphone may be expressed as 

(1) 



where e voltage output of the microphone. 
p = sound pressure. 

Q = sensitivity constant of the microphone. 
^ and < are the angles shown in Fig. 3. 

If the distance between the source of the sound and the collecting 
system is D, Fig. 3, the energy density at the microphone due to the 
direct sound is 

Eo (2) 



where = power output of the sound source. 
c = velocity of sound. 



* The ratio of reflected to direct sound has been referred to as the "recorded" 
or "collected" reverberation. 



Aug., 1934] REPRODUCTION OF SOUND 69 

To simplify the discussion, assume that the effective response angle 
of the microphone is the solid angle 12. The direction and phase of 
the reflected sound are assumed to be random. Therefore, the re- 
flected sounds available for actuating the directional microphone are 
the pencils of sound within the angle 12. The response of the direc- 
tional microphone to generally reflected sound will be 12/47T that of a 
non-directional microphone. The generally reflected sound to which 
the directional microphone is responsive is therefore given by 

- ecS [log (1 -a)t}/4v] (1 - a ) (3) 



where a = absorption per unit area. 

5 = area of absorbing material. 

V = volume of room. 

t = time. 

The ratio of the generally reflected sound to the direct sound is a 
measure of the recorded reverberation: 

En _ 4D 2 tt [1 - ecS [log, (1 -o)*]/4y] (1 - g) 
E~ aS 

If the sound continues until the conditions are steady, equation (4) 
becomes 



From (4) and (5), it will be seen that the received reverberation can 
be reduced by decreasing the distance D, by increasing the absorption 
aS, or by decreasing 12. 

Fig. 4 compares a non-directional microphone with a directional 
microphone in which 12 = 4?r/3 (i. e., the velocity microphone). 
The output of the microphone due to direct and generally reflected 
sound shows less frequency discrimination due to the absorption 
characteristics of the studio. 

This discussion shows that, for the same room, the recorded rever- 
beration in a directional system will be 12/47T that of a non-directional 
system; or, for the same room and the same recorded reverberation, 
the directional microphone can be operated at \/47r/12 times the 
distance of a non-directional microphone. * 

* A fundamental requirement of any microphone is a directional characteristic 
independent of frequency. A system that does not possess such a characteristic 
will introduce frequency discrimination. The directional characteristics of the 
velocity ribbon microphone are independent of the frequency. 



70 



H. F. OLSON AND F. MASSA 



[J. S. M. P. E. 



(C) Use of a Directional Sound-Collecting System for Discriminat- 
ing against Sounds Incidental to the Action. When one listens nor- 
mally with both ears he is able to focus his attention on the main 
source of action and subconsciously attenuate incidental noises that 
may be present. In single-channel sound reproduction, it is im- 
portant that the same emphasis be placed on the main action and a 




Aug., 1934] 



REPRODUCTION OF SOUND 



71 



corresponding discrimination be made against the incidental sounds. 
In those respects the directional collecting system possesses distinct 
advantages. Fig. 5 illustrates. The action centers about the char- 
acters seated at table 2. To achieve the correct artistic effects as 
regards distance, the pick-up distance must be comparable with the 
camera distance. As a consequence, the distances from tables 1, 2, 
and 3 to the microphone are nearly the same. Therefore, in order to 
concentrate the attention upon table 2, the only alternative for 
attenuating the sound from the tables 1 and 3 with respect to 2 is 



SET WALL 



\ I / 

Y 

O MICROPHONE 






CAMERA 



FIG. 5. Arrangement employing a directional 
collecting system for emphasizing the action and dis- 
criminating against incidental sounds. 



to use a directional collecting system. Furthermore, the relative 
ratio of the intensities of the sounds from tables 1 and 3 can be ad- 
justed to what one would actually hear were he located at the "dis- 
tance" of the camera. This example illustrates how a "center of 
gravity" of the recorded sound can be established comparable with 
the "center of gravity" of the action. 

(D) Use of a Directional Sound-Collecting System in Locating 
the Action with Respect to the Environs. When we listen normally 
with both ears we are able to localize the azimuth of the sound by 
means of binaural triangulation. In the preceding section, it was 
shown that an illusion of azimuth of the action can be gained in a 



72 



H. F. OLSON AND F. MASSA 



[J. S. M. P. E. 



single-channel system by adjusting the relative intensities of the 
various sounds in accordance with the way in which one would nor- 
mally hear when viewing the action first-hand. In listening nor- 
mally the source of sound is further localized, as regards distance, by 
the time relations between the direct sound and the sound reflected 
from the boundaries, as illustrated in Fig. 6. If a directional sound- 
collecting system is employed, the pencils of sound reflected from the 
walls 1 and 3 will be attenuated more than the pencils of sound re- 
flected from wall 2, corresponding to the relative intensities of the 
sounds perceived by a person located at the microphone position. 
The relative time-intervals and intensities of the direct sound and 
the sound reflected from wall 2 determine the perspective of the 

5ET WALL 2 




FIG. 6. Arrangement employing a directional 
sound-collecting system for creating an illusion of 
the position of the source of sound, by utilizing the 
relative times and intensities of the direct and re- 
flected sounds. 



sound. To accomplish an illusion of depth successfully under 
the conditions described, it is important that the first reflections 
from the boundaries should overshadow the succeeding reflections. 
The reverberation-time of sets is generally relatively short, which 
means that the boundaries are highly absorbent and that the first 
reflections predominate. Furthermore, the geometry of the sets is 
usually such that the reflected sound is directed into the studio 
proper. This example illustrates how an illusion of depth or per- 
spective of the recorded sound can be established by the time-interval 
and intensity of the direct and reflected sounds reaching the micro- 
phone, and by excluding or attenuating sounds that would not normally 
contribute to the perspective. 



Aug., 1934] REPRODUCTION OF SOUND 73 

(E) Sound-Collection Distance Commensurate with Camera Dis- 
tance. In the preceding sections means have been outlined for es- 
tablishing perspective in a single-channel system by employing a 
directional sound-collecting system. In order further to enhance the 
artistic effect of the collected sound, it is important that the apparent 
distance of the sound source, as perceived in the reproduced sound, 
be commensurate with the apparent distance of the projected picture 
as perceived on the screen by the eye. In order that the realistic 
effects outlined in sections (C) and (D) be enjoyed to their utmost, 
it is important that the reflected sounds capable of actuating the 
microphone shall not be large compared with the direct sound. 



DIRECTIONAL CHARACTERISTIC 
OF MICROPHONE ~~ -^ 



MICROPHONE 




FIG. 7. Arrangement employing a direc- 
tional sound -collecting system to secure the 
correct balance and reverberation character- 
istics of the instruments of an orchestra. 



In section (B) it was shown that the ratio of the direct to the re- 
flected sound was inversely proportional to the square of the dis- 
tance and directly proportional to the effective angle of the collect- 
ing system. Obviously, since the collecting distances commensurate 
with the picture distance are in general relatively large, a directional 
collecting system is required to maintain a tolerable ratio of direct to 
reflected sound. 

(F) Use of a Directional Collecting System for Adjusting the Relative 
Intensities and Reverberation Characteristics of a Group of Recorded 
Sounds. The recording of an orchestra is a salient example of the 



74 



H. F. OLSON AND F. MASSA 



[J. S. M. P. E. 



value of a directional sound-collecting system. In musical sound 
reproduction there are two important factors, namely; the "correct 
balance" or relative intensities of the instruments, and the correct 
reverberation characteristics of the reproduced sound. In a non- 
directional system only one parameter, the distance, is available for 
controlling the intensity and effective reverberation of the recorded 
sound. However, in a directional sound-collecting system, two 
parameters are available. A plan view of a directional sound-collect- 
ing system (a velocity microphone) and a group of sound sources is 



ARRANGEMENT OF 

MICROPHONE* 



I -ORCHESTRA 




(OJ 



(b) 



ORCHESTRA 
RESULTANT, 




(C) 



FIG. 8. Use of two directional microphones mounted at right angles for 
varying the "balance" of an orchestra. 



shown in Fig. 7, which is self-explanatory. In this particular case 
the sound source 5 2 is to be emphasized, and it is consequently placed 
upon the axis of the sound-collecting system and quite close to it. This 
results in a relatively high recorded intensity and low recorded rever- 
beration. Sound source 5 4 is placed at an angle of 60 degrees, in 
which case an attenuation of the direct sound of 6 db. results, due to 
the directional response characteristic of the microphone. In other 
words, practically any value of loudness, as well as of effective rever- 



Aug., 1934] REPRODUCTION OF SOUND 75 

beration, can be attained by orienting and positioning the sources 
with respect to the microphone. 

The preceding discussion shows how the correct balance and rever- 
beration characteristics of musical reproduction may be effected by 
employing a velocity microphone. In certain musical recordings it is 
desirable to change the balance or relative intensities of the instru- 
ments during the course of a single selection. This may be accom- 
plished by employing two velocity microphones, one placed above 
the other, with the axes of the ribbons in the same line and the planes 
of the ribbons intersecting at right angles. A plan view of such an 
arrangement is shown in Fig. 8. In Fig. S(d) the mixers of micro- 
phones 1 and 2 are adjusted so that the outputs of the two micro- 



ORCHESTRA ORCHESTRA 





(b) 

FIG. 9. Arrangement of two directional micro- 
phones for controlling the recorded reverberation of 
an orchestra. 



phones are equal. In this case the vector of maximum pick-up 
passes through the center of the orchestra. In Fig. 8(b) the mixers of 
microphones 1 and 2 are adjusted so that the output of microphone 1 
is several times that of 2. In this case, the vector of maximum 
pick-up passes through the left-hand portion of the orchestra and, as a 
consequence, the left portion of the orchestra is emphasized relatively 
to the right-hand portion. Similarly, in Fig. 8(c), the right-hand 
portion of the orchestra is emphasized relatively to the left-hand 
portion. 

By employing three velocity microphones, two placed as described 
above and the third at right angles, the resultant vector can be 



76 H. F. OLSON AND F. MASSA [j. S. M. P. E. 

shifted from side to side in order to emphasize certain portions of the 
orchestra, and shifted up and down to control the collected reverbera- 
tion. 

Fig. 9 shows another variation of the use of two microphones. 
In Fig. 9 (a) the axis of microphone 1 passes through the center of 
the orchestra, microphone 2 being at right angles. If microphone 2 
is used alone, practically all the recorded sound is reflected sound. 
The reflected or reverberant sound decreases as the relative recorded 
output of 1 with respect to 2 increases. 

Fig. 9(6) is another variation, in which the microphones are placed 
at right angles and separated in space. At low frequencies, when the 
distance between the microphones is small compared with the wave- 
length of the sound, the resultant collection diagram is a cosine 
function. At higher frequencies the diagram is complex. 

The systems shown in Fig. 9 are valuable when it is desirable 
to introduce considerable reverberation or "liveliness" into the 
recording. 

DISPERSION OF SOUND 

(A) The Action of a Reproducer in a Reverberant Room: Direct 
and Generally Reflected Sound. The resultant sound energy density 
at the position of the auditor in a theater depends upon the response, 
the directional and energy characteristics of the loud speaker, and 
the reverberation characteristics of the theater. From the stand- 
point of the auditor, it may be said that there are two sources of 
sound energy, namely: the direct sound, which travels directly 
from the loud speaker to the auditor, and the generally reflected 
sound, which is reflected from the boundaries before reaching the 
auditor. 

In a theater free from acoustical difficulties, the energy density 
of the generally reflected sound is practically the same for all parts 
of the theater. Therefore, the solution of the problem of achieving 
uniform energy density is to employ reproducers that will yield the 
same direct sound energy to all parts of the theater. We shall il- 
lustrate by an example how that may be accomplished by employing 
a directional loud speaker. 

(B) The Distribution of Direct Sound Energy in a Theater, Em- 
ploying a Directional Loud Speaker. An elevation view of a re- 
producer in a theater is shown in Fig. 10. The two extreme points 
to be supplied are indicated 1 and 2. If the speaker were non-direc- 



Aug., 1934] 



REPRODUCTION OF SOUND 



77 



tional, the ratio of the direct sound energy densities at the two points 
would be inversely as the ratio of the squares of the distances from 
the reproducer. In this particular case, the difference in level is 13 
db. Obviously, such a large variation in sound intensity precludes 
the possibility of satisfactory reproduction over the entire area to be 
supplied. Therefore, a compensating means must be provided to 
counteract the variation of intensity with the distance from the re- 
producer. The directional reproducer furnishes a solution of the 
problem. 



HIGH FREQUENCY 
DISTRIBUTION^^ 



T 



MBINED LOW 
FREQ. DISTRIBUTION 




DISTANCE ALONG THEATRE 

FIG. 10. Arrangement of a directional sound-radiating system in a theater, 
shelving the uniform sound distribution attained. 

The directional characteristics of the individual units in Fig. 10 
vary with frequency, being somewhat sharper at the high frequencies, 
as compared with the low frequencies. The use of two or more loud 
speakers makes it possible to arrive at directional characteristics 
that are practically independent of the frequency. In this particular 
case, at low frequencies, the difference of level for a point 40 degrees 
from the common axis, as compared with the level at a point on the 



78 H. F. OLSON AND F. MASSA [j. s. M. P. E. 

axis, is 13 db. The loud speakers are adjusted until the axis of the 
characteristic passes through the point 2. Then the height is ad- 
justed until the angle 6 is 40 degrees. To render the distribution 
uniform at the higher frequencies, the horns are flared and the rela- 
tive output of the loud speakers adjusted for uniform distribution. 
The distribution over the distance under consideration is shown in 
Fig. 10. In other words, the variation of the sound pressure with 
the angle between the axis and the line joining the observation point 
and the reproducer has been employed to compensate for the de- 
crease of the sound energy with the distance. 

The sound energy density, due to direct sound radiation from 
the loud speaker, may be defined as 

(6) 



where po = the sound pressure at a distance X . 

r the distance from the loud speaker to the observation point. 
p = the density of air. 
c = the velocity of sound. 

Re = the ratio of the sound pressure at the angle 6 to that at the angle 
zero. 

To analyze the distribution of the direct sound over the area, the 
plan view of the theater and the directional characteristics of the 
reproducer must be considered. The number of reproducers will de- 
pend upon the angle subtended at the loud speaker by the area to be 
covered and the effective dispersion angle of the reproducer. 

(C) The Energy Density in a Theater Due to Reflected Sound. The 
sound energy density due to the generally reflected sound is a func- 
tion of the absorption characteristics of the theater and the power 
output of the reproducer. The sound energy density due to the 
generally reflected sound is given by 

- a ) (7) 



where a = the average absorption per unit area. * 
,S = the area of the absorbing material. 
V = the volume of the room. 
t = time. 

c = the velocity of sound. 
P = the power output of the loud speaker. 



*The average absorption coefficient for a directional dispersing system in a 
theater in which the absorption of the boundaries depends upon the orientation of 
the axis of the system with respect to these surfaces. 



Aug., 1934] REPRODUCTION OF SOUND 79 

(D) Total Sound Energy Density: Effective Reverberation. The 
total sound energy density at any point in the theater will be the sum 
of the direct and the generally reflected sound, and may be expressed 
by 

E T = D + R (8) 

In section (B), a method was outlined employing directional loud 
speakers for achieving uniformity of the energy density of the direct 
sound. The energy density of reflected sound, as shown by equation 
(7), is independent of the observation point. As a consequence, by 
employing directional loud speakers, the sound energy density will 
be the same in all parts of the theater. Furthermore, the effective 
reverberation of the reproduced sound (the ratio of generally reflected 
to direct sound), due to the theater, is the same for all parts of the 
theater. 

To gain the effect of greatest intimacy in the reproduced sound, 
it is important that the acoustical characteristics of the recording con- 
ditions be emphasized and those of the theater suppressed, an ob- 
jective that will be attained by making the ratio of the direct to the 
reflected sound as great as possible. 

A consideration of equations (6) and (7) shows that the effective re- 
verberation due to the theater can be reduced by decreasing the rever- 
beration time. There are, of course, limitations beyond which a 
further reduction of the reverberation time becomes impracticable. 
Further consideration of the equations shows that the effective rever- 
beration can be reduced by means of directional loud speakers; that 
is to say, the generally reflected sound is proportional to the effective 
dispersion angle of the loud speaker. From the foregoing discussion, 
we may draw the following conclusion: the use of a directional 
loud speaker reduces the effective reverberation due to the theater 
and emphasizes the acoustics of the action by suppressing the acous- 
tics of the theater; for example: outdoor scenes practically no 
reverberation; cathedral scenes much reverberation. 

This paper has been concerned with creating the maximum degree 
of intimacy with the reproduced sounds by emphasizing the acoustics 
of the studio. In certain musical arrangements serving as accompani- 
ments to the picture, there would be an advantage in employing a 
spread-out sound source, such as, for example, loud speakers spread 
across the entire stage, as contrasted to the cluster outlined in this 
paper. 



80 H. F. OLSON AND F. MASSA [J. S. M. P. E. 

DIRECTIONAL SOUND-COLLECTING AND DISPERSING SOUND SYSTEMS AS 

A UNIT 

The use of a directional sound-collecting system, together with 
a directional sound-dispersing system, establishes: A "center of 
gravity" of the action by emphasizing the action and suppressing in- 
cidental sounds ; an illusion of depth or perspective, by adjusting the 
time intervals and intensities of the direct and reflected sounds reach- 
ing the microphone and by excluding or attenuating sounds that 
would not contribute to the perspective; a reverberation characteris- 
tic compatible with the projected picture, by employing collection 
distances comparable with the camera distance; a large ratio of 
direct to reflected sound in the theater, emphasizing the acoustics of 
the action and suppressing the acoustics of the theater; in reproduc- 
ing music, a correct "balance" or relative ratio of intensities of the 
instruments, and a correct reverberation characteristic of the re- 
produced sound by adjusting the two parameters in the directional 
collecting-system that control those factors. Then by the careful 
application of a directional sound-collecting and dispersing system, 
a new and powerful means of controlling sound reproduction becomes 
available for enhancing the illusion of reality and heightening the 
acoustical character of the performance. 

REFERENCES 

1 FLETCHER, H.: "Transmission and Reproduction of Speech and Music in 
Auditory Perspective," /. Soc. Mot. Pict. Eng., XXII (May, 1934), No. 5, p. 314. 

2 OLSON, H. F. : "The Ribbon Microphone," /. Soc. Mot. Pict. Eng., XVI (June, 
1931), No. 6 J p. 695. 

DISCUSSION 

MR. DAVEE: Are the data given in the paper actual or theoretical? How 
were the sound pressures measured, if the data are actual? 

MR. OLSON: In the case of the theater, we have made sound energy measure- 
ments. To obtain the direct sound energy density the measurements are made 
outdoors, or in free space. Then measurements are made indoors, giving a combi- 
nation of direct and generally reflected sound. 

In the case of the collection of sound, the data which we have shown were 
results of observation rather than of direct physical measurements. Of course, 
the microphones were calibrated, and we also made measurements showing the 
discrimination against sound coming from off the axis; but in the final analysis, 
it is the results that count in case of recording, rather than the measurements. 

MR. FRITTS: Please state the elementary differences of construction and 
principles of the velocity microphone as compared with the other types? What 
other styles of construction can be used to make the microphone directional? 



Aug., 1934] REPRODUCTION OF SOUND 81 

MR. OLSON: The directional characteristic of the velocity microphone is a 
cosine characteristic the same as a loop antenna. The efficiency of pick-up 
is a function of the cosine of the angle with respect to the axis, which is normal 
to the ribbon. Such a characteristic results from the fact that the ribbon of the 
velocity microphone is actuated by the difference of pressure between the two 
sides of the ribbon, which is a function of the cosine of the angle. For ex- 
ample, if a sound originates in the plane of the ribbon, the same pressure occurs on 
both sides of the ribbon. The maximum difference of pressure between the two 
sides occurs when the source of sound is in a line normal to the ribbon. 

This microphone has a uniform directional characteristic with respect to fre- 
quency. The combination of a pressure and a velocity microphone is another 
example of a directional microphone. 

MR. SHEA: With respect to using a number of ribbon microphones* for re- 
cording, can you notice the interference due to the fact that the microphones are 
not in exactly the same location? Analogously, in theaters where one loud 
speaker is directed toward the rear and another toward the front of the theater, 
is the interference noticeable at the center of the theater? 

MR. OLSON: When using two or three microphones, the microphones are 
placed in line normal to the floor. In this case there would be practically no 
interference, because the distance from the source to each microphone is prac- 
tically the same. 

When the microphones are separated, there are interference effects, of course, 
at the higher frequencies, and the combined characteristic is quite complex; 
but, apparently, if the distance is not too great, it is noticeable in some instances, 
but not in others. 

In the case of the two loud speakers, interference does not occur because the 
distance from each unit, at the point where the two feed a certain portion of the 
theater, is the same. In other words, at the overlap point in the theater, the 
distance from the unit to the point of observation is the same; and therefore 
there is no phase shift, and, consequently, no interference. Of course, there 
would be interference at the front of the theater, but there is no sound at this 
point from the upper loud speaker. The same is true at the rear of the theater 
where there is no sound from the lower speaker. 



SIXTEEN-MILLIMETER SOUND PICTURES IN COLOR* 

C. N. BATSEL AND L. T. SACHTLEBEN** 

Summary. The nature of a variable-width sound track on longitudinally lenticu- 
lated color films is discussed, and the optical reduction of 35-mm. subtractive color sub- 
jects to 16-mm. film by the Kodacolor process is described. 

It is the purpose of this paper to present a brief account of work 
done in the development laboratory relative to the production of 16- 
mm. sound films in full color. The medium selected was the well- 
known Kodacolor process of color photography and projection, a 
true three-color additive process, 1 ' 2 by which excellent pictures may 
be made and projected in full natural color. 

Following extensive development in the 16-mm. sound picture 
field, during which means were worked out for producing 16-mm. 
sound films of good quality, both by direct recording and by re- 
recording from 35-mm. sound films, some attention was given to the 
matter of producing 16-mm. sound records on Kodacolor film. It 
was thought at the time that some peculiar effects might arise if the 
sound recording beam were passed through the longitudinally lenticu- 
lated base of the film before the final formation of the image on 
the emulsion, as in the case of the picture. The lenticular film base 
would no longer permit the formation of a true optical-slit on the 
emulsion, but would produce a series of images, each separated from 
the other, formed by the several cylindrical lenses in the path of the 
beam. For instance, if a recording optical system images an optical 
slit upon an emulsion through a longitudinally lenticulated film base, 
the image that results will be a true image of the slit in the longitu- 
dinal plane, and a series of more or less sharp images of the exit pupil 
of the system in the transverse plane. And as the cutting edge of 
the recording beam advances and recedes across the cylindrical lenses 
there will be produced a series of more or less fully illuminated images 
of the exit pupil of the system in the transverse plane, according to 
the extent to which the individual lenses on the film base are filled 

*Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
**RCA Victor Company, Camden, N. J. 
82 



SOUND PICTURES IN COLOR 83 

with light. Thus, in recording in this fashion by the variable-width 
process, the recording image consists of a series of more or less brightly 
illuminated image elements, rather than a uniformly illuminated 
image of continuously varying length. Fig. 1 shows the comparison 
between variable-width recording on standard film and on Kodacolor 
film when the emulsion is in the reverse position. 

It is seen that the blackened portion of the variable-width nega- 
tive will comprise a series of longitudinal strips of density, rather 
than a continuous field of density, and that the boundary between 




FIG. 1. Comparison of variable- width sound tracks on 
Kodacolor film and on standard film. 

the clear and the blackened portions of the track will not be a smooth 
curve, but will comprise a series of more or less fully exposed images 
of the exit pupil, in the transverse plane. Or, more simply, the 
boundary presents a serrated or step -like appearance where it crosses 
the lenticulations. This was a situation quite different from that 
encountered in usual variable- width practice, and it was felt that dis- 
tortions of a more or less troublesome nature might arise from it. 

A single-film, 16-mm. sound camera was chosen to test the feasi- 
bility of recording sound on Kodacolor film.. The camera was con- 
structed for normal black-and-white picture work with the recording 



84 C. N. BATSEL AND L. T. SACHTLEBEN [J. S. M. P. E. 

system focused directly upon the emulsion in the obverse position. 
With Kodacolor film the emulsion was in the reverse position, making 
it necessary to refocus the recording system before a recording could 
be made. The original test recording was made on August 9, 1932. 
The sound record was very successful, and definitely demonstrated 
the feasibility of recording sound on this film by the variable-width 
process, with the emulsion in the reverse position. It was found that 
no distortion of a serious nature occurred due to the use of Kodacolor 
film with longitudinal lenticulations. 

Pursuant to the successful recording of sound on Kodacolor film 
in the single-film, 16-mm. sound camera, it was believed that sub- 
tractive color subjects on 35-mm. film should be optically reducible 
to 16-mm. film by the Kodacolor process, using an optical system 
similar to that employed in Kodacolor photography with the 16-mm. 
camera. The first test was made in a crude way using a projector 
fitted with a two-inch Kodacolor projection lens as a camera. The 
projector was mounted in a light-tight box and focused on a white 
card, upon which was projected an image of a frame from a 35-mm. 
Technicolor print. A strip of raw Kodacolor film was placed in the 
projector, exposed and reversed, with the result that a fairly promis- 
ing image was obtained when the film was reprojected. 

Following this, an optical-reduction step-printer was equipped 
with the necessary optics to permit printing directly from a 35-mm. 
Technicolor film to 16-mm. Kodacolor film. This optical system 
was essentially the one used in Kodacolor projection, with a three- 
color filter in front of the printing lens, and a negative lens at the 16- 
mm. film to produce a virtual image of the filter of the proper size 
at the proper distance from the film. The first system was im- 
provised from such optics as were available in the laboratory, and the 
pictures obtained exhibited marked color dominants at the margins, 
due to the insufficient speed of the printing lens and the consequently 
diminished size of the filter image. Nevertheless, the results were re- 
markably promising. Later, a lens of sufficient speed was obtained 
to permit the required 3 :1 ratio between the distance from the film to 
the filter image, and the total width of the filter image ; with the result 
that a great improvement was effected in the color-balance, and the 
color dominants at the edges of the picture were practically eliminated. 

The sound track of the 35-mm. Technicolor print was transferred to 
the 16-mm. Kodacolor film by continuous optical reduction printing, 
with the 16-mm. emulsion in the obverse position. 



Aug., 1934] SOUND PICTURES IN COLOR 85 

Summarizing, it has been shown in the laboratory that 16-mm. 
Kodacolor sound films can be successfully produced without intro- 
ducing serious sound distortions due to the peculiar character of the 
film base. Such films can be produced by either of two methods: 
by recording with a 16-mm. single-film sound camera at the time the 
picture is taken, or by optical reduction printing of the picture and 
sound track on the Kodacolor film from a 35-mm. subtractive sound 
film. 

Acknowledgment is due Mr. A. C. Blaney for his suggestion that 
35-mm. subtractive color pictures be optically reduced to 16-mm. film 
by the Kodacolor process. 

REFERENCES 

^APSTAFF, J. G., AND SEYMOUR, M. W. : "The Kodacolor Process for Amateur 
Color Cinematography," Trans. Soc. Mot. Pict. Eng., XII (1928), No. 36, p. 940. 

2 WEiL, F. : "The Optical Photographic Principles of the Agfacolor Process," 
/. Soc. Mot. Pict. Eng., XX (Apr., 1933), No. 4, p. 301. 

DISCUSSION 

MR. HOLSLAG: Do I understand that the first portion of the film that was pro- 
jected was made on a direct single-system sound camera? 

MR. SACHTLEBEN: Yes. 

MR. HOLSLAG: Then I don't quite understand how the emulsion could be 
turned around so it would face the recording light. It seems to me that it would 
be out of focus, because in the Kodacolor process it is necessary to photograph 
through the film base. 

MR. SACHTLEBEN: It was necessary to refocus the recording optical system. 

MR. HOLSLAG: You would have to have a special focusing adjustment for the 
recording light. 

MR. SACHTLEBEN: or some means of pushing the image forward optically. 
That could be done quite simply. 

MR. RICHARDSON: It seems to me the principal fault with color pictures is the 
constant predominance of certain colors. What, if any, progress is being made in 
bringing out the finer shades of color and differentiating between the vast number 
of possible shades. 

MR. BATSEL: In respect to this paper, we are not trying to develop new color 
processes. 

MR. RICHARDSON: Well, do you know whether there is any possibility of re- 
ducing the preponderance of red, or other colors, and bringing out the more deli- 
cate shades? 

MR. BATSEL: Yes, if there is too much red you can change the filters, or the 
illumination of the subject. We used the filters that were supplied to us. We 
may have more red than we should have had if the subjects had been illuminated 
by sunlight. 

MR. RICHARDSON: When there is a predominance of one or two colors the pic- 



86 C. N. BATSEL AND L. T. SACHTLEBEN 

ture on the screen doesn't look natural. Occasionally we see a picture that ap- 
parently has a wonderful assortment of shades that appear naturally, and theater 
patrons comment on the beauty of the picture. If there is any possibility of 
making such pictures it ought to be done. 

MR. CRABTREE : Most of the color pictures shown to date have been produced 
by the two-color processes, in which, as you say, the reds and browns, greens and 
bluish greens predominate. In order to reproduce the original colors faithfully 
a three-color process is necessary. The only three-color processes that have been 
developed commercially to date are the Spicer-Dufay; the Gaumont, which re- 
quires special projectors; the Technicolor process, exemplified by the Silly Sym- 
phony cartoons; and the Kodacolor process, which to date has been shown only 
in 16-mm. 

I think that the fidelity of reproduction of color in the three-color processes is 
quite remarkable. In the case of some of the color sequences that we have seen 
perhaps the choice of colors in the set was not very appropriate, so that with some 
subjects the colors have been rather glaring. However, I want to assure Mr. 
Richardson that processes are now available that are capable of reproducing 
colors faithfully. So far Technicolor has restricted its pictures to cartoons and 
indoor sets. I expect that within the next six months you will see outdoor pic- 
tures by Technicolor that will probably meet with your approval. 

MR. ELAINE: I might mention that the Technicolor camera has been used out- 
of-doors along the coast of Europe. We have recently received some of the most 
beautiful negatives and prints that we have ever seen, and I believe they repro- 
duce exactly the natural colors of the scenes. 

MR. FAULKNER: I have seen some of Technicolor's out-door scenes taken in 
the last thirty days, and there is a vast difference between them and the two- 
color pictures with which we are all acquainted. 

MR. EDWARDS: I believe a great deal of the trouble with the color pictures 
we see in the theaters nowadays is due to the make-up man in the studio. He 
has the same idea that he had in the old Kinemacolor days, that if he wanted to 
get a peach bloom on a girt, he had to paint her in ocher red. Besides, not enough 
care is taken in selecting the colors in their sets. They are so anxious to get color 
that the color is overdone. 

MR. KELLOGG: I don't think it is quite fair to this demonstration to center 
attention on the imperfections of the colors. The men that made the film and 
projected it are interested primarily in showing that the sound system that we 
have been working on for the Victor Company is applicable to pictures made by 
the Kodacolor process. For that purpose they have used the standard Koda- 
color system, and have taken a few pictures in colors, recording sound on the same 
film. The work happened to be done in the winter, when good outdoor color sub- 
jects were not abundant. Enough shots were made to show that sound can be 
satisfactorily recorded on Kodacolor film. The pictures were in color, and that 
is as far as the authors of the paper attempted to go not to give a demonstration 
of pictorial art. 



A 16-MM. SOUND RECORDING CAMERA* 
C. N. BATSEL, L. T. SACHTLEBEN AND G. L. DIMMICK** 

Summary. A discussion of some of the problems encountered in the development 
of a 16-mm. sound recording camera, and a description of the most important features 
of such a camera developed for the use of amateurs. 

The rapid transition of the professional movies from silent to sound 
pictures convinced those engineers who had followed the development 
and expansion of 16-mm. pictures that unless sound were added, the 
field of application of that type of moving picture would rapidly 
narrow and become practically extinct. Consequently, work was 
carried on for several years in developing means of obtaining and 
showing sound-on-film 16-mm. pictures. Most of the earlier efforts 
were expended in developing re-recording, printing, and projection 
equipment that would fulfill the needs of the commercial users. It 
was realized, however, that perhaps the largest consumers of 16-mm. 
film and equipment were the amateurs; and while the projection 
equipment developed for commercial use was so designed that it could 
serve the amateur exceedingly well, it was felt that his interest in 
pictures was largely held by the fact that he could make as well as 
show his own pictures. If this interest were to be maintained it 
would be necessary to provide the appropriate film and equipment. 

The problem of providing a means of permitting him to take the 
pictures and record the sound presented some very difficult and un- 
solved problems, not only as to the simplicity and dependability of the 
design, but as to size also. 

Consequently, in developing such a camera, the primary considera- 
tions were dependability, size, weight, and simplicity of operation; 
so that the person using it could make good sound movies with very 
little more effort than when taking a silent picture, and with as much 
assurance of good over-all results as could be experienced with his 
silent camera. The size and weight should be such that it could be 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** RCA Victor Company, Camden, N. J. 

87 



88 BATSEL, SACHTLEBEN, AND DIMMICK [j. s. M. P. E. 

carried and operated inconspicuously and with ease; and, finally, 
there must be a minimum number of controls to be manipulated 
during operation. 

Although the camera described in this paper is in an advanced 
stage of development, it is still a laboratory product. However, so 
much of the preparatory work has been accomplished that we hope to 
be able to make such equipment commercially available in compact, 
fool-proof, and inexpensive form within the near future. 

Fig. 1 is a general view of the camera. Its dimensions are 7Vi 
inches high, 8 7 /ie inches long, and 5 Vie inches wide. It weighs 8 x /2 
Ibs. when loaded with one 100-ft. roll of daylight-loading sound 




FIG. 1. General view of camera. 

recording safety film and with three No. 2 dry cells for supplying the 
current for the recording lamp. The electrical equipment is some- 
what heavier, due to the amplifier and microphone. 

Extreme care was taken in designing the case to give it a neat 
appearance as well as to fulfill its function of housing the working 
parts of the camera. It is finished in a neat, durable gray, crinkle 
finish, with chromium plated trimmings, and is equipped with a 
padded leather strap handle securely attached to the top. 

The door, or cover, and the telescopic view-finder are made in one 
piece. The view-finder is so placed that when taking shots with the 
camera held before the face in the operating position it is directly 



Aug., 1934] 16-MM. SOUND CAMERA 89 

before the left eye. It is also very convenient when using the tripod. 
The front lens of the finder is ruled into squares to represent the field 
covered in using 1-, 2-, and 4-inch photographic lenses. It produces 
an upright image, is corrected for parallax for distances greater than 
35 feet, and has an adjustment on the eyepiece for distances less than 
35 feet. 

Fig. 2 is a view with the door removed, showing the arrangement of 
the main assembly plate. The reels are located in the top of the case, 
the one at the left being the supply reel. The footage indicator at the 
back of the camera is actuated by an arm that rides on the surface of 
the film on the supply reel. This type of indicator never needs re- 




FIG. 2. Main assembly plate showing 
location of reels and optical system. 

setting, and is calibrated to indicate the unused footage of film. The 
reel at the right is the take-up reel. Driving torque is supplied to it 
through gears and a slipping clutch, thereby insuring a positive, never- 
failing, take-up action. 

The single sprocket serves three functions: (1) as a pull-down 
from the feed reel; (2) as the hold-back for the take-up reel; and 
(3) as a recording sprocket. All movable pad-rollers are eliminated, 
and threading is made much easier by placing stationary rollers 
about the sprocket in such a manner that the natural stiffness of the 
film serves to keep it in contact with the sprocket surface. It is very 
essential that the film stay snug against the sprocket at the recording 
point, yet pass on and off freely. Experiment showed that suffi- 



90 BATSEL, SACHTLEBEN, AND DIMMICK [j. a M. P. E. 

ciently good sprocket action for recording could be effected by prop- 
erly dimensioning the sprocket drum and teeth and by flexing the 
film about properly placed stationary rollers so that the stiffness of the 
film would hold it snugly in contact with the drum over approxi- 
mately a 90-degree wrap. As a precaution against jamming, a metal 
stripper was inserted at the point where the film leaves the sprocket. 

Torque is supplied to the sprocket by a spring motor capable of 
running 25 feet of film through at the proper speed with one winding. 
The running time can be made longer by installing a longer spring, 
but experience has proved that 25 feet of film will be sufficient 
for practically all shots. This is particularly true of the autophone 
type. The operator of the camera rewinds after each shot, using the 
winding crank permanently attached to the rear of the case. How- 
ever, lest he should forget, the spring motor is equipped with an auto- 
matic stopping device, which prevents the camera from operating 
after 25 feet of film have passed. This feature prevents the spoiling 
of recordings resulting from the motor's running down and the conse- 
quent reduction of the speed. 

Extreme care has been taken in designing the spring motor to make 
it capable of unwinding freely during its entire run and consequently 
exerting a constant pressure on the train of high-quality spur gears 
that drive the sprocket. Uniformity of the recording speed is 
achieved by connecting a flyball governor of the type used in phono- 
graphs to the sprocket-shaft driving gear through an extra-high- 
quality pinion gear. The friction pad against which the governor 
disk runs is provided with two stops, one for a speed 16 frames per 
second, and one for 24 frames per second. The single-claw, cam- 
operated intermittent movement is driven by a crown gear freely 
mounted on the sprocket shaft, and driven by the shaft through a 
damped spring. This form of drive effectively prevents reaction of 
the intermittent load back through the gear- train to the sprocket. 
The shutter is mounted on the intermittent cam-shaft, and is open for 
picture exposure during 240 degrees of the revolution. The gate is 
doweled to the center-plate at exactly the correct distance to focus 
the picture image properly on the film. The pressure-shoe can be 
quickly and easily removed from the camera to permit inspection and 
cleaning of the gate surface. 

For picture taking the standard equipment is an//3.5 1-inch focal 
length lens. However, the camera is equipped with a self -locking 
rotating turret that will accommodate three lenses. The wear- 



Aug., 1934] 16-MM. SOUND CAMERA 91 

resisting locking device will always insure perfect centering of the lens 
on the picture area. In connection with the variable-focus lens used 
in turret jobs, it is sometimes advisable to check the focus of the 
image. A critical focusing device is supplied for installation behind 
the lens opening opposite the picture aperture. The desired lens can 
then be focused in this position and turned over to the picture aper- 
ture for use. 

The recording optical system occupies a space just behind the 
sprocket and beneath the take-up reel, as shown in Fig. 2. It is of the 
variable-width type, and records the sound track along the edge of the 
film according to the accepted dimensions. The requirements of 
space and weight were kept forcibly in mind during the development 
and design of the optical system, with the result that it is only 2y 4 
inches in diameter by 3 7 / 8 inches long, and fits into the camera without 
destroying the symmetry of the case. 

The optics of the system are extremely simple. Essentially it 
comprises a 4-volt, 3-watt Jamp with a small coiled filament, a con- 
denser lens, an aperture, a bi-convex spherical lens, and a cylindrical 
lens, arranged in the order given. The system is folded in the hori- 
zontal plane. The bi-convex spherical lens is in the form of a lens 
mirror, and is attached to the vibrating member of the system. 

In forming the recording image, the condenser focuses the lamp 
filament on the lens mirror, and the cylindrical lens in turn focuses the 
filament on the film in the vertical plane. In the horizontal plane the 
lens mirror focuses one edge of the aperture (at the condenser) on the 
film for the recording edge of the light beam. The image on the film 
is 3 /4 of a mil high, and permits a maximum sound-track width of 58 
mils. 

The recording unit carries an adjustable pin abutting against a boss 
on the main center-plate, which is machined accurately with respect 
to the surface of the sprocket drum. Before assembling the optical 
system into the camera, it is placed in a jig, adjusted, and focused. 
The adjustable pin is fixed against a boss in the jig corresponding 
exactly, as to location, to the one on the camera center-plate. Every 
camera is alike in this respect. Consequently, all recording units are 
interchangeable, and their installation merely requires placing them 
upon the plate and pushing them forward until the pin abuts against 
the boss, before locking into place with the screws provided for the 
purpose. 

The recording unit is supplied in two types the newsreel and the 



92 BATSEL, SACHTLEBEN, AND DIMMICK [j. s. M. p. E. 

galvanometer, the difference between the two lying in the means 
employed in actuating the mirror. In the newsreel type the driving 
unit is a metal diaphragm coupled mechanically to the mirror by a 
system in self -equilibrium; and by properly choosing the material 
from which it is constructed, no strain is imposed upon the diaphragm 
due to changes of temperature. The chamber that houses the dia- 
phragm is located between the mirror and the back of the camera 
case. Part of the chamber extends through the case, forming a 
mouthpiece. The mass and stiffness of the mechanical parts, assisted 




FIG. 3. Rear view showing newsreel mouth- 
piece and battery compartment. 

by the properties of the properly designed acoustical circuits, afford a 
response covering the range from 200 cycles to 3000 cycles, which is 
sufficient for recording intelligible speech. 

Inasmuch as this type of unit depends upon the sound waves of the 
voice to operate the diaphragm and mirror, it is essential that the 
speaker place his mouth fairly close to the mouthpiece. The newsreel 
camera is, therefore, so designed that when the operator holds it be- 
fore his face in order to take pictures, the mouthpiece is directly in 
front of his mouth. A double-layered wire wind-screen and perfo- 
rated metal guard placed in the mouthpiece effectively protect the 



Aug., 1934] 



16-MM. SOUND CAMERA 



93 



diaphragm from blasts of wind and physical damage. The mouth- 
piece of the newsreel recording unit and the lamp battery compart- 
ment are shown in Fig. 3. 

The galvanometer is essentially the same as the one used in 35-mm. 
recording. 1 It is of the dry, permanent magnet, vibrating-reed type, 
with the lens mirror mounted on a tiny grooved plate resting upon the 
sharp end of the vibrating reed and held in place by a flexible strip of 
phosphor bronze. It is small in size, and is completely interchangeable 
with the newsreel unit. The mirrors in both units are made adjust- 
able in the horizontal plane, in order to 
set the light beam to the null position by 
means of a screw protruding through the 
back of the case. 

Power is supplied to the galvanometer, 
and current to the recording lamp by a 
cable from the extremely portable am- 
plifier and battery-box. The amplifier 
is extremely high-gain, and contains two 
tubes, one 232 and one 233. It is 
equipped with a glow-tube monitoring 
device, which warns the operator when 
serious overshooting of the sound track 
occurs. Additional assistance in moni- 
toring can be gained by using the head- 
phones and by observing the deflection 
of the light beam through the window 
in the side of the case. The battery- 
box contains a complete set of B bat- 
teries and two sets of recorder lamp and 

C batteries. The amplifier and the battery-box measure 7 1 /z X 6 
X 2 3 / 4 inches over-all, and are designed to be mounted on the 
tripod by a "unimount" suspension as shown in Fig. 4. 

The microphone is of the magnetic type, and is not sensitive to jars 
and wind as is the carbon microphone. It is ruggedly constructed 
and sufficiently sensitive to record speech of amplitude equivalent to 
the complete width of the sound track when placed 6 feet from the 
loud speaker. The over-all response of the electrical equipment 
covers the range 150 to 3000 cycles. 

Before closing, it should again be emphasized that the models 
described in this paper were made in the laboratory, and that they are 




FIG. 4. Camera mounted on 
tripod, with amplifier mounted 
on the unimount suspension. 



94 BATSEL, SACHTLEBEN, AND DIMMICK [j. S. M. p. E. 

not yet in their final form for the commercial market. A point of 
development has been reached, however, which seems to indicate that 
within a few months apparatus incorporating such desirable features 
of convenience, simplicity, portability, and appearance may be made 
available on the market. 

Acknowledgment is due to E. W. Kellogg and I. J. Larson for many 
helpful suggestions during the development of the camera, and to 
H. Belar and A. Shoup for the design of the compact and efficient 
amplifier. 

REFERENCE 

1 DIMMICK, G. L.: "Galvanometers for Variable-Area Recording," /. Soc. 
Mot. Pict. Eng., XV (Oct., 1930), No. 4, p. 428. 

DISCUSSION 

MR. GOLDEN: What is the approximate cost of the entire outfit? 

MR. WEST: We do not yet have a final list price. I believe that the 
camera by itself will sell for less than $300. The attachment shown in the last 
illustration will probably sell for about $200. 

MR. KELLOGG: During the earlier development of 16-mm. sound films, the 
thought of making good amateur sound movies seemed to be a forlorn hope; there 
were enough difficulties in making good 35-mm. recordings. With 16-mm. films 
on which the sound waves had to be compressed to 40 per cent of their former 
size, the problem of obtaining adequate resolution was many times greater; and 
those who were following the sound-recording work were not overly optimistic 
about attempting to get good sound with extremely light and portable equipment, 
using picture negative and without either the technic or the facilities that were 
available in making commercial 35-mm. sound pictures. We felt that in order to 
record good-quality sound on 16-mm. film, all the refinements of the very best 
laboratory equipment would be essential. Mr. C. N. Batsel, the author of the 
paper, is the one to whom we are profoundly indebted for the vision to realize 
fully the possibilities of the much wider field for 16-mm. sound pictures that 
would be opened when people could make their own movies, photograph their 
own families, and be amateur picture producers, rather than simply motion pic- 
ture audiences. 

In working with some of the earlier laboratory equipment, one of the very happy 
surprises we had (perhaps not a 100 per cent surprise, but at least it was a great 
comfort to have it checked) was that there is available to every amateur a sound 
stage acoustically superior, probably, to the best stages in Hollywood. In other 
words, if you want a good sound stage you can find it out-of-doors. You may 
have to motor a mile or two to the woods, or to some quiet place away from too 
many neighbors, but when you find such a place, without too much wind (the 
wind used to bother more than it does now), you will have almost ideal conditions. 
The microphone distance at which the recording can be done is limited principally 
by the gain of the amplifier, and the great loss of sound quality that comes into 
play at quite small distances indoors is not bothersome. So there were no diffi- 



Aug., 1934] 16-MM. SOUND CAMERA 95 

culties, acoustically, in taking a number of what we considered very successful 
amateur movies, without having the microphone in the picture. 

Of course, one may wish to take movies indoors. In that case, he will have to 
endure whatever acoustical difficulties the surroundings impose; but whenever it 
is desired to have the microphone comparatively well away from the subject, the 
problem can be solved by going out-doors. It is fortunate that it is within the 
means of every amateur to get this ideal sound stage without spending a million 
dollars on concrete, sound proofing, and sound absorption. 

MR. CRABTREE: What is the weight of the total equipment? 

MR. BATSEL: The weight, including the amplifier, is approximately 30 
pounds 8Y 2 pounds for the camera alone. 

MR. PALMER: Was the picture that was shown a print from a 16-mm. nega- 
tive, or was it a reversal? 

MR . B ATSEL : Reversal . 

MR. PALMER: Was it the original film on which the picture was taken? 

MR. BATSEL : Yes ; the same as the amateur film used for silent pictures. The 
picture is made on the film and it is returned to the Eastman Kodak Co. for 
processing. The original film that was exposed in the camera is returned to you 
for projection. 



CONTINUOUS OPTICAL REDUCTION PRINTING* 
A. F. VICTOR** 



Summary. Referring to his early experimentation in continuous optical reduc- 
tion printing, the author discusses briefly the state of the art and present practices. 

At the Fall Meeting of the Society, at Pittsburgh, in 1919, the author 
presented a paper dealing with the continuous reduction printer. 1 
Since that time, many things have changed. Sound, then a vague 
possibility, has come to stay and has revolutionized the motion pic- 
ture. The continuous reduction printer, then a variant of the re- 
duction step printer, has now become an essential necessity. Quoting 
from another paper, 2 in 1918, on the subject of portable projectors: 

Following the introduction and adoption of the safety standard film, the next 
logical step of progression was the creating of a supply of this film, adequate for 
the needs of the field it has to safeguard. The most immediate and richest source 
of film subjects would naturally be the thousands of standard negatives already in 
existence. Only one bit of apparatus was required to bring this treasure trove into 
immediate service of the home, school, and church: a satisfactory reduction 
printer was the essential thing. 

With the advent of sound the continuous reduction printer has come 
into its own. By its means sound tracks already registered on stand- 
ard negatives or positives may be expeditiously and accurately trans- 
ferred to film of smaller or larger dimensions. 

At the present moment interest is centered in the reduction of sound 
from 35-mm. to 16-mm. film. Film of the latter width, since its in- 
troduction in 1923, has steadily developed in usefulness and quality. 
Finer emulsions, better development, and greater illumination in 
projectors have brought a larger and more brilliantly illuminated 
screen image. Twelve-foot pictures are now a reality, and the sim- 
plicity and safety of 16-mm. film apparatus recommend their use 
where such advantages are important. 

Several 16-mm. projectors equipped with sound reproducing appa- 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Victor Animatograph Corp., New York, N. Y. 
96 



CONTINUOUS OPTICAL PRINTING 



97 



ratus are now being manufactured and marketed. Needless to state, 
the manufacture and sale of such projectors have aroused a demand for 
16-mm. sound film. "The immediate and richest source would be the 
thousands of standard negatives already in existence," so that the 
problem is the reduction of this standard supply to 16-mm. film. 
There are two ways of doing this : by means of electrical re-recording, 
or by optical reduction. 




FIG. 1. Original design of continuous 
reduction printer. 



In re-recording, the standard negative is passed through an appa- 
ratus similar to a reproducer. A light beam passing through the al- 
ready recorded track is varied according to the photographic densities 
(in variable-density records) or to the areas of light transmission (in 
variable-width records) of such a track, and the resultant electrical 
impulses cause an oscillator or a glow-lamp to record a new sound 
track on the smaller film. In principle the system does not differ 
greatly from original recording. 



98 A. F. VICTOR [j. s. M. p. E. 

Regardless of the fact that the writer was the inventor of con- 
tinuous optical reduction, he does not believe that re-recording is 
inferior to optical reduction, as has been claimed by a number of per- 
sons lately. On the contrary, he believes that re-recording has possi- 
bilities that optical reduction does not possess; especially as regards 
the facility with which sound from mediums other than the standard 
track may be interpolated and changes made during reduction if re- 
quired. 

The particular reduction printer used and manufactured by the 
author at the present time closely resembles the machine designed in 
1919, illustrated in Fig. 1. A single sprocket carries the two films on 
different diameters, the small film on the inside. Both films travel on 
a single shaft and are turned together about a common center. There 
is no need of reversing the travel of the films ; both travel in the same 
direction, the prism serving to reverse the image. 

There can be no greater simplicity, no fewer parts. Experience 
has shown that the work produced by this machine is equal to the 
best yet produced by this method of reduction printing. The only 
limitation to the quality appears to be imposed by the graininess of 
the photographic emulsion. However, up to a frequency of 8000 
cycles, according with usual practice, the result is commercially 
acceptable and perhaps all that may be ever required. The average 
16-mm. projector-reproducer does not reproduce frequencies higher 
than 6000 cycles, although 7000 may be possible, with interference 
from film noise. 

A continuous reduction printer requires perfect sprockets and su- 
perior optics. The tendency to flare in the final line image is consider- 
able, and care must be taken in selecting the condensing as well as the 
objective lenses; otherwise the harmonics are lost. Focusing is best 
accomplished by projection : a fine surface screen is located near the 
floor, and a projection lens is placed beneath the 16-mm. track for the 
purpose of observing the projected line image. 

Referring to Fig. 1, the mount B supports the condenser, the first 
objective, and the slit. The light beam passes through the prism C 
and is directed downward at an angle of ninety degrees, the objective 
D forming an image of the sound track, at E, on the 16-mm. film. 
The sprocket A carries both films, having two sets of teeth and two 
diameters. For simplicity, the drawing does not show the take-up 
spools or the feed and take-off sprockets. 

A possible variant of the principle of optical reduction is found in 



Aug., 1934] CONTINUOUS OPTICAL PRINTING 99 

the use of the light valve. With such a type of reduction printer, no 
attempt is made toward achieving sharp optical definition, as only 
variations in the quantity of light are demanded. The result is a 
variable-density track, of course; but in this form of printer pictures 
may be reduced from variable- width as well as from variable-density 
recordings. 

The reason for suggesting such a scheme is based on the possibility 
of increasing the speed of printing. The printing light may be in- 
creased considerably when no well-defined image is demanded, an 
especially valuable feature when the reduction is directly to 16-mm. 
positive instead of to a negative track. The present tendency is to 
reduce directly from standard negative film to 16-mm. positive. The 
main disadvantage is that the negatives wear out. The writer be- 
lieves that the practice is due to the lack of better contact printers, 
and that when better equipment becomes available the results from 
16-mm. negatives will be quite satisfactory. It is recommended that 
efforts be made toward designing contact printers so that 16-mm. 
negatives may be employed. 

As regards the development and processing of 16-mm. sound 
tracks, the laboratory plays a very important part in this work. The 
most perfectly reduced track may be ruined by faulty development. 
Great precision is demanded; the striations at a frequency of 8000 
cycles are equal in fineness to those at a frequency of 24,000 cycles on 
standard film, and the high tones are easily lost when over or under- 
development occurs. Furthermore, the graininess should be reduced 
as much as possible; reversal prints have indicated what splendid 
results can be attained with finer grains, and the best sound the writer 
has heard has been obtained by that means. 

In closing, the writer should like to point out that neither the con- 
tinuous reduction process nor the type of machine designed for that 
purpose by the writer in 1918 was patented, and is therefore open to 
use or manufacture by anyone. 

REFERENCES 

1 VICTOR, A. F.: "The Continuous Reduction Printer," Trans. Soc. Mot. Pict. 
Eng., Ill (1919), No. 9, p. 34. 

2 VICTOR, A. F.: "The Portable Projector: Its Present Status and Needs," 
Trans. Soc. Mot. Pict. Eng., II (1918), No. 6, p. 29. 



A NON-SLIP SOUND PRINTER 1 
C. N. BATSEL** 



Summary. The improvement of sound negatives and the extension of the 
frequency range have made the printing of the sound negative onto the final print 
much more difficult. This paper deals with a printer that assures positive contact 
and no slipping between the two films at the time of printing. The principle upon 
which it operates is discussed, and improvements to be gained in making prints 
upon a machine of this type are shown. 



In making sound-on-film records the first requirement is a good 
sound negative. Much has been done to improve the recording 
machines, optics, and film in order that good negatives can be made 
with frequencies up to 10,000 cycles. The second requirement is 
to make high-quality reproductions of the recordings; usually by 
contact printing. Most contact printers today make use of a split 
sprocket or a curved gate to carry or support the film as it passes the 
light aperture. The sprocket or gate is usually so designed as to 
correct for a fixed value of shrinkage of the negative. 

It is physically impossible for all negatives to bear the same rela- 
tion to the raw stock as to length at the time of printing. Conse- 
quently some slippage must occur. There is also evidence of poor 
contact between the two films at the printing aperture, particularly 
in the sprocket machines. At a frequency of 10,000 cycles, corre- 
sponding to a wavelength of 1.8 mils on the film, a slippage of 0.001 
inch will cause considerable blurring and make it impossible to pro- 
duce a good print regardless of how good the negative may be. 1 

The need for a continuous contact printer that would be consistent 
in its performance and accommodate various values of film shrinkage 
became increasingly apparent as other improvements were made in 
sound recording. A principle on which a contact printer that 
meets those requirements might be based, was proposed some time 
ago by A. V. Bedford, who also constructed a laboratory contact 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** RCA Victor Company, Camden, N. J. 
100 



A NON-SLIP SOUND PRINTER 



101 



printer embodying the same idea. 2 The same principle as applied 
to printers has also been described by R. V. Wood. 3 

The principle employed for avoiding slippage, on the basis of which 
the printer described in this paper was designed, is briefly as follows : 
Two belts differing in length may be made to travel past a given 
point without slippage between the two, provided the belts are held 
in contact around rollers in such a way as to prevent slippage along 
the line of contact. This statement is based on the fact that when 
bending a belt around a pulley or roller, the mean length of the belt 
remains always the same; whereas the concave side, contiguous to 




FIG. 1. Diagram illustrating principle of non-slip printer. 

the roller, is compressed and the convex side stretched, in proportion 
to the curvature of the roller. Thus, if the short belt (or shrunken 
negative) is bent around a roller of the proper diameter, the outer 
surface will become longer than the mean length of the film. Then, 
if the longer, unshrunken raw stock is passed over the same roller, 
tangent to the outer surface of the negative film, assuring good con- 
tact and, consequently, traction, between the two by means of a pres- 
sure roller at the point of contact, the concave surface or compressed 
side of the long film will make contact with the stretched side of the 
short film only along the line of tangency. 

Printers employing sprockets or curved gates fulfill such a require- 
ment only under one condition: when the negative or raw stock 



102 C. N. BATSEL [j. s. M. p. E. 

happens to have exactly the proper length, so that the flexing around 
the sprocket or gate results in making the length of the inner surface 
of the raw stock exactly the same as that of the stretched outer sur- 
face of the negative a rather remote possibility. 

Referring to Fig. 1 and assuming that the pitch (or the number of 
sprocket holes per unit length) of the shrunken film is PI and that of 
the raw-stock is P 2 , the shrinkage factor is Pi/Pz- The condition 
for maintaining synchronism between corresponding particles of the 
two films is Pi/Pi = Vi/ V 2 , in which V\ is the mean velocity of the 
shrunken film and V 2 that of the unshrunken film. The condition 
under which no slippage occurs (referring to Fig. 1) at the line of 
tangency is 

T/ RP T/ ^ 2 t1\ 

Vl R c = Vz R? 
whence 

Rt = R P jf e .jl (2) 

Therefore since the two films are held in non -slipping contact at 
the tangent line or printing point the outer surface of the inner or 
shrunken film will be on the radius R p = RI -+- T, T being the thick- 
ness of the film; and at the line of contact (P ), the outer surface of 
the inner film will carry the inner surface of the raw stock past the 
line at its own velocity. As contact is assured and no slippage oc- 
curs at P , the raw stock automatically assumes at the line of contact 
the radius of curvature given by equation (2) which is a function of 
the lengths (or pitches) of the two films. 

It is readily seen that if no exterior forces are brought to bear 
upon the raw stock, it will travel past the line P at the proper rate to 
compensate for the difference between the mean lengths of the two 
films; and if allowed to form a free loop as it approaches PI, it will 

7? ' ~P 
form about the radius R P -=- - and remain so formed until all the 

R c Pz 
film has passed PQ. 

From this it is evident that the principle depends entirely upon 
the choice of the film path and the size of the rollers. The film path 
must be so arranged that a small change in the length of the upper 
loop of the raw stock will cause a large change in the angle at which 
the film approaches the contact line at P . The size of the rollers 
tangent at PQ must be such that for any required correction of shrink- 
age, the film will not pull taut over the pressure roller. This means 



Aug., 1934] A NON-SLIP SOUND PRINTER 103 

of control can be used until the difference between the lengths of the 
two films becomes so great that RI becomes too small to permit flex- 
ing the negative around it. 

Fig. 2 is a photograph of the model, showing the various rollers 
and the film path. The diameters of the printer rollers have been 
so chosen that the control is effective over a range in which the length 
of the negative may have any value from about 0.2 to 1.0 per cent 
greater than that of the raw stock. The curve assumed by the raw 




FIG. 2. Model of non-slip printer, showing 
film path and various rollers. 



stock as it approaches the contact point is controlled by the loop be- 
tween the feed sprocket and the main drum, which is adjusted to pro- 
vide sufficient range with a change of approximately one frame in 
the length of the loop. The average condition requires, of course, 
less than one frame, and does not interfere with the synchronism be- 
tween the sound and the picture. Immediately before passing over 
the main drum the raw stock passes over a movable roller, which 
follows up the loop and acts also as a guide roller. After passing the 
printing drum the raw stock forms a loop, and passes over a hold- 



104 



C. N. BATSEL 



[J. S. M. p. E. 



back sprocket to the take-up reel. The negative film is fed down 
from the supply reel over a feed sprocket, then over a guide and pres- 
sure roller, over the drum, and then over a pull sprocket to the 
take-up reel. The negative is in contact with the printing drum and is 
used as a means of driving the drum. To assure steadiness of mo- 
tion at the printing point and prevent variations of density in the 
sound track due to irregularities of speed, a speed-regulating mecha- 
nism has been attached to the drumshaft. 

To achieve the best results it is important that the printing light 
strike the films at the point at which they are in contact. If the 
light should cover the films before and after contact there would be 
an apparent slippage and a consequent blurring of the printed image. 
In order to prevent this the height of the printing light beam has 
been restricted to approximately 0.0025 inch, by imaging an 




FIG. 3. Output curves, showing improvement obtained with new printer 
at the high frequencies: solid curve, neg. ; dashed curve, commercial print 
(restricted light aperture) ; dot-and-dash curve, non-slip printer. 



0.005-inch mechanical slit on the film reduced in the ratio of two to 
one. Light control and stopping and starting devices are installed 
on the model to make it operative on a commercial basis. 

Test prints of the "Service Reel" have been made with this printer. 
The output and the variation in output were measured and compared 
with prints of the same negative made on a popular commercial prin- 
ter, the height of the printing aperture of which had been reduced to 
1 /s inch. The curves of Fig. 3 show the improvement in the output 
at the higher frequencies, which is apparently entirely due to better 
printing as the same care was taken in processing and the same den- 
sity produced in both cases. 

REFERENCES 

1 CRABTREE, J.: "Sound Film Printing," /. Soc. Mot. Pict. Eng., XXI (Oct., 
1933), No. 4, p. 294. 



Aug., 1934] A NON-SLIP SOUND PRINTER 105 

2 U. S. Pat. 1,754,187; granted 1927. (This type of drive was applied also to 
sound-film printers in 1929.) 

8 WOOD, R. V.: "A Shrinkage-Compensating Sound Printer," /. Soc. Mot. 
Pict. Eng., XVIII (June, 1932), No. 6, p. 788. 

DISCUSSION 

MR. KELLOGG: The fact that the radius of curvature at the driving point 
affects the linear speed of a belt, has long been recognized. The selection of 
suitable curvature to minimize slippage has also been applied in designing contact 
printers. The novelty in the Bedford printer consists in making the film select its 
own curvature, and in the very simple expedient by which that is accomplished. 
The manner in which the device operates is not obvious. Even if one conceded 
the soundness of the general principle it was not at first clear that the curvature 
at the point where the film is pinched between the rollers could be varied suffi- 
ciently to compensate for extremes of shrinkage. But Mr. Bedford's simple 
model settled the point. The principle of operation might have been somewhat 
more clearly explained if Fig. 1 had shown the film approaching the driving point 
between the rollers from several angles. You will notice in Fig. 2 that the new 
stock is fed from a sprqcket above and to the left of the friction rollers, and that 
the path between is so arranged that when the loop is excessively long, the film 
makes a swing to the right and approaches the driving point from the right. 
With a shorter loop the film approaches from directly above; whereas with a 
still shorter loop, it approaches the driving point from the left. It should also 
be borne in mind that the left-hand roller may revolve at any speed (it simply 
serves to hold the raw stock against the negative at the driving point), that 
the raw stock is drawn through the rollers entirely by the friction between it and 
the surface of the negative (which you may regard as moving at constant speed), 
and that the friction between the two films is exerted only at the line of contact 
where the rollers pinch them together. So we are concerned only with the curva- 
ture of the raw stock at that one point. 

If the concave side of a bent film is propelled at a specified velocity, more feet 
of film per minute (measured after it is straightened) would pass than if the convex 
side were propelled at the same velocity. Therefore, by flexing the film so that 
the driven side is convex or concave, the speed of the film as a whole can be altered. 
Another way to look at it is this: Imagine that we could stretch or shrink the 
film as desired. We might adjust each piece of raw stock to exactly the same 
length (for a given number of sprocket holes) as the negative, and then print 
without slippage. Fortunately, we do not need to stretch or shrink (compress) the 
film as a whole. It is sufficient to stretch or compress one of its surfaces, the one 
that is in contact with the negative, which stretching and compressing are very 
easily accomplished by simply bending the film. 

Because of the arrangement of the loop, the accumulation of a little additional 
film between the sprocket and the rollers will result in the raw stock's entering 
the driving point with its concave side toward the negative, which automatically 
speeds up its passage through the rollers. In a few seconds equilibrium is at- 
tained, and the speed at the rollers becomes identical to that at the sprocket. 
On the other hand, suppose that the raw stock has been in storage a while and 



106 C. N. BATSEL [j. s. M. P. E. 

has shrunken abnormally. It will then approach the rollers from the left, bending 
around the left-hand roller and presenting a convex surface to the negative at the 
driving point. That is the condition required to feed fewer linear feet of raw 
stock through for a given length of negative. 

One of the problems in designing the printer was to obtain the necessary 
changes of curvature with the smallest possible differences in loop length. This 
required a careful experimental study of roller sizes, and of determining the best 
loop arrangement. In the model that has been described, sufficient variation in 
the angle of approach (and therefore in the curvature at the driving point) was 
attained to accommodate all degrees of shrinkage normally encountered, with a 
small enough change in loop length to remain well within tolerances of syn- 
chronism with the picture. 

In experimenting with printers of this type it is easy to be fooled by slippage. 
Thus, with a short loop the raw stock tends to be placed in tension, causing a 
slight slipping which would work in the same direction as the curvature changes, 
and therefore make the printer appear to be working properly when it is not. 
Low loop tension for all working positives, good contact pressure, and a speed 
control by curvature that really works, are the necessary conditions to prevent the 
slipping. 

Any printer for synchronous sound must, of course, control the speeds of both 
the negative and the raw stock by sprockets geared together, or by running both 
over one sprocket. Most present contact printers print on a sprocket. There is 
one important point about sprockets that has not been recognized as generally 
as it should be, and that is that there is only one length of film (for a given number 
of sprocket holes) that can run on any particular sprocket without slippage on the 
surface. Probably the easiest way to visualize that is to calculate how fast a 
film would run in the absence of teeth if it did not slip. Obviously, it could be 
calculated simply by multiplying the number of revolutions per minute by the 
circumference in feet (making proper allowance for the thickness of the film in 
estimating the diameter) . But on the basis of the number of teeth on the sprocket 
there is another way of calculating the film speed. Multiply the number of 
teeth on the sprocket by the revolutions per minute, and divide that by the 
number of sprocket holes in a foot of film (not the nominal number 96, but the 
exact number, to a couple of decimal places), and the two calculations will almost 
always result in a slightly different answer. Which is correct? The teeth will 
control, and if friction between the film and the body of the sprocket should give 
a different speed, then slipping must occur. If, as in a printing sprocket, there 
are two films on the one sprocket, the effect is equivalent simply to increasing 
the body diameter for the outer film. There is still a surface that must be moving 
at a certain speed; and the raw stock that runs over the surface, engaged by 
teeth, in all probability requires a different speed, and slippage between the 
two surfaces is practically inevitable. The slippage is, to be sure, generally small; 
but so are the waves to be printed. 

MR. TERRY: Do you not lose loop or gain loop if the differences between the 
films are exactly figured? 

MR. KELLOGG: Whatever gain or loss of loop occurs, takes place hi the first 
few seconds, and amounts to not more than about an inch of film. Thereafter the 
loop remains constant, whether we print 50 feet or 1000 feet of film. The curva- 



Aug., 1934] A NON-SLIP SOUND PRINTER 107 

ture control makes it possible for both films to travel the same number of sprocket 
holes per minute, and at the same time to run past the printing point in contact 
without slipping and with no accumulation of gain or loss in the loop. For two 
films to run in contact without slipping it is not necessary for them to have 
identical lengths, but only that the two surfaces that are in contact shall have the 
same length, and the convex surface of the shrunken film can be made to have the 
same length (for a given number of perforations) as the concave side of an un- 
shrunk film. 

MR. MITCHELL: Have pictures been printed with this type of printer? What 
is the extent of asynchronism due to a change in the length of the loop? 

MR. BATSEL: In this particular printer the loop will change about one frame, 
and will compensate for a shrinkage of about 1.2 per cent. 

MR. MITCHELL: There seems to be a great tendency to pay more attention 
to the parent film and to maintain shrinkages within certain tolerances; with 
the proper humidity in the printing and stockroom that can be done. 

We also find that as the sprocket teeth curve away from the base to the tip, 
there is a little compensation according to a somewhat similar principle, due to the 
fact that the film rides up and down on the teeth. 

MR. BATSEL: It is true that proper storage reduces shrinkage. In running 
vault-stored films through the printer I noticed quite a bit of change in the loop, 
indicating that even those films that were stored under the proper conditions 
differ somewhat in length. It seemed that even regardless of storage some type 
of printer is needed that will compensate for varying shrinkage. The sprocket 
will not do that. 



OPTICAL REDUCTION SOUND PRINTING* 
G. L. DIMMICK, C. N. BATSEL, AND L. T. SACHTLEBEN** 

Summary. The optical reduction sound printer was developed to provide a simple 
and direct means of transferring sound tracks from 35-mm. film to 16-mm. film, and 
its use resulted in the production of 16-mm. sound tracks of superior quality. The 
mechanical and optical requirements of the printer are discussed, and features of the 
process that led to the improved record quality pointed out. An optical system is 
described that was built to convert a re-recorder into an optical reduction sound printer. 

The laboratory development of an optical reduction sound printer, 
by means of which high-quality sound tracks might be transferred 
from standard 35-mm. films to 16-mm. films by direct photographic 
printing, was originally occasioned by the desire to simplify the pro- 
duction of 16-mm. sound prints from standard films. In proceeding 
from the original standard sound negative to the finished 16-mm. 
sound print by the re-recording process, two printing operations and 
one recording operation are necessary. It is necessary to prepare a 
print of the standard negative from which to re-record on the 16- 
mm. film if the 16-mm. negative is to be of the highest quality; and 
it is also essential to produce the finished 16-mm. sound track by a 
final contact printing of the 16-mm. negative. These printing steps, 
when properly carried out, eliminate non-linear distortions occurring 
at the higher frequencies in variable-width negatives, due to the fill- 
ing in of the valleys of the negative record. The investigations of 
Sandvik, Hall, and Streiffert 1 have shown that non-linear distortion 
becomes a minimum and modulation of transmission becomes a maxi- 
mum in variable- width records when the print density is made equal 
to, or slightly less than, the negative density. The optical reduction 
sound printer provides for the direct production of a 16-mm. print 
from a standard sound negative by optically projecting an image of 
the moving standard sound track upon the moving 16-mm. positive 
emulsion, at the proper magnification. 

Steps were taken in the laboratory in January, 1932, to construct 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** RCA Victor Company, Camden, N. J. 
108 



SOUND PRINTING 



109 



a model optical reduction sound printer. The mechanical require- 
ment of uniform motion of the two films in the proper speed ratio 
of 2.5 to 1 was fulfilled by properly gearing together two film-moving 
mechanisms, each incorporating the magnetic drive developed by 
Kellogg 2 to assure freedom from irregularity of the film speed. In 
this type of drive the film is propelled at the recording or scanning 
point by a magnetically driven drum, to which irregularities of speed 
arising in the train of driving gears can not be imparted. Also at 
the recording point the film is isolated from the sprocket by flexible 
loops of film, which render the uniformity of motion of the film at 



*< 

Uj| 



LONGITUD/MAL PLAMe 





FIG. 1. Diagram of anamorphote optical system of model reduction 
sound printer. 

that point independent of the pitch of the perforations and the 
sprocket action. The normal vibrations of the film-driving system 
are effectively damped by magnetic means. The optical require- 
ments of the printing system were peculiar in that the reduction ratio 
in the plane of motion of the film was 40 per cent; whereas in the 
transverse plane the reduction ratio was 85.7 per cent, necessitating 
the adoption of an optical system of the anamorphote or distorted- 
image-producing type employing a combination of cylindrical and 
spherical lenses yielding unequal reductions in the two planes. The 
optical system finally adopted comprised a pair of crossed cylindrical 
lenses with a standard 32-mm. achromatic microscope objective dis- 



110 



DIMMICK, BATSEL, AND SACHTLEBEN [J. S. M. P. E. 



posed between them, the image being formed independently in each 
of the two planes by the achromatic lens and one of the cylindrical 
lenses. An appropriate illuminating system was employed to scan 
the standard sound track, and to direct the light into the printing 
system in an efficient manner. Fig. 1 is a schematic diagram of the 
printing optical system proper. 

Sixteen-mm. sound films were not only more easily produced on 
the optical reduction printer, but were at once noted to be superior 




FREQUENCY IN CYCLE* PER SECOND 



FIG. 2. Comparison of frequency characteristic of a print produced by 
optical reduction with that of the negative from which it was made: (A) 
35-mm. recording galvanometer deflection; (B) measured output of print 
of 35-mm. frequency negative (0.5 mil reproducer slit) ; (C) measured output 
of 16-mm. optical reduction print of same 35-mm. negative (0.5 mil repro- 
ducer slit). 



in quality to any 16-mm. sound films previously produced. Fig. 2 
compares the frequency response characteristic of a print produced 
by optical reduction with that of the negative from which it was made. 
The improved quality is partly attributable to the fact that no con- 
tact printing is involved, with its attendant dependence of print 
quality upon sprocket hole pitch, and upon the degree of fidelity of 
contact between the negative and the raw positive stock. The in- 
vestigations of J. Crabtree 3 have shown that printer "slippage," 
arising from improper sprocket hole pitch in contact printing, or 



Aug., 1934] 



SOUND PRINTING 



111 



from inaccuracies in the sprocket pitch or tooth shape in the printer, 
gives rise to more or less periodic variations in the amplitude of a 
high-frequency print. Such high-frequency prints, when reproduced, 
are characterized by a "fuzzy" or "soft" quality, and are lacking in 
"cleanness" or "crispness." In the optical reduction printer, in- 
corporating the magnetic drive to propel both the 35-mm. and 
16-mm. films, uniformity of film speed at the scanning and printing 
points does not depend upon sprocket or sprocket hole pitch. In 



/. 



02 



1.4 I.S 



FIG. 3. Relation between specular and diffuse density 
of motion picture positive film. 



addition, the transfer of the sound track by optical reduction is wholly 
an optical-photographic process, allowing distortions of a photo- 
graphic nature in the negative, such as filling in of the valleys, to be 
compensated for in printing and developing the 16-mm. positive. 1 
Compensation for such distortions in re-recording can be effected 
only by preparing a print of the standard sound negative and re- 
recording from it, since non-linear distortions of a photographic 
origin can not be compensated for in any way, once they have been 
impressed upon an electrical circuit. 

Since the two films are not printed in contact, but an image of the 



112 



DIMMICK, BATSEL, AND SACHTLEBEN [J. S. M. P. E. 



standard sound track is projected upon the 16-mm. film by an opti- 
cal system, the specular density rather than the diffuse density of the 
negative is the effective factor in optical reduction printing. The 
specular density of a developed image is determined by measuring 
the light transmitted through the layer of silver grains without change 
of direction; whereas the diffuse density is determined by measuring 
both the light passing through without change of direction and the 
light that is scattered or diffused by transmission through the silver 
grains of the developed image. Since less light is transmitted specu- 
larly than is transmitted both specularly and by diffusion, the specu- 
lar density of an image is higher than its diffuse density. Fig. 3 is 
a curve obtained by Tuttle 4 showing the relation between the specu- 




ONLy A fffACT/ON Or TRANSMITTED LIGHT /S UT/L/ZCO. 




ALL TKAMSMITTCD LIGHT /S UT/L/1O. 

FIG. 4. Diagram illustrating the manner in which in- 
creased contrast of the negative arises in optical printing. 

lar and diffuse densities of images on motion picture positive film. 
Thus, in optical reduction sound printing the effective density of the 
negative is greater than in contact printing, and therefore the effec- 
tive contrast is greater. This permits greater contrast and better 
resolution to be obtained in the print, with a consequent increase in 
the high-frequency response of the print. Fig. 4 illustrates how the 
increased effective contrast of the negative arises in optical printing. 

CONVERSION OF A RE-RECORDER FOR OPTICAL REDUCTION SOUND PRINTING 

In response to the interest shown in the improved 16-mm. sound 
prints produced by direct optical reduction printing, the laboratory 
designed an optical system for converting a re-recorder 6 to an optical 



Aug., 1934] 



SOUND PRINTING 



113 



reduction printer. The film-moving mechanisms of the film phono- 
graph and 16-mm. recorder heads of the re-recorder impart motion 
to the film of sufficient constancy for printing; and, in addition, per- 
mit the use of the simplest kind of optical system, since the two films 
are moving in opposite directions at the scanning and the printing 
points. The problem was therefore that of providing a simple optical 
system that would image the 35-mm. sound track upon the 16-mm. 
film at the proper ratios in the two planes. 

The optical system adopted is of the anamorphote type employing 
two achromatic microscope objectives, with two uncorrected cylin- 
drical lenses between them, and both working in the same plane. In 
the longitudinal plane, or the plane parallel to the direction of mo- 



LONGITUOMAL PLAHZ 




TRAHSVGS PLANE 

FIG. 5. Diagram of anamorphote optical system of re- 
recorder converted for optical reduction sound printing. 



tion of the film, the achromatic objectives alone are employed in the 
formation of the image. The first achromatic lens forms a virtual 
image of the 35-mm. sound track, which is re-imaged upon the 16-mm. 
film by the second achromatic lens at an over-all magnification of 
0.400, which is the ratio of the two film speeds. In the transverse 
plane, the two cylindrical lenses, acting together, modify the original 
virtual image of the 35-mm. sound track in such a manner that in 
the transverse plane the over-all magnification is 6/7, which is the 
ratio of the two sound track widths. Fig. 5 is a schematic repre- 
sentation of the printing optical system proper. Features of the 
system are that in the longitudinal plane, in which the greatest reso- 
lution is required in order that the shorter wavelengths may be suc- 
cessfully printed, the image is formed only by the achromatic lenses, 



114 DIMMICK, BATSEL, AND SACHTLEBEN [J. S. M. P. E. 

which in that plane work at about one-third their maximum aperture. 
The uncorrected cylindrical lenses act only in the plane in which the 
resolution requirements are not great. At the same time the mag- 
nification of the final image is practically independent of the position 
of the second achromatic lens, making it possible to adjust the focus 
of the system without changing the magnification. 

The illuminating system comprises a standard 10- volt, 7.5-ampere 
lamp, a condenser system, and a lens that images a 0.010 X 0.115- 
inch optical slit on the 35-mm. sound track. This optical slit is in 
turn imaged by the printing system upon the 16-mm. emulsion at 
which point the image of the 35-mm. sound track is in focus and mov- 




FIG. 6. Re-recorder converted for optical reduction sound printing; cover 
removed and doors open to show threading. 

ing in the same direction and at the same velocity as the 16-mm. 
emulsion. The printer is equally adaptable to both variable- width 
and variable-density work, and fulfills the high illumination require- 
ments attendant upon the production of a duplicate negative from a 
"noiseless recording" variable-density print without exceeding the 
rated wattage of the lamp. Variable- width work is carried on with 
the lamp current between 5 and 6 amperes, whereas the rated cur- 
rent is 7 x /2 amperes. The system is capable of producing a duplicate 
negative from a print, and a print from a negative, and a frame line 
mask is provided for use when printing from a combined print or 
from a negative that carries both picture and sound. 



Aug., 1934] SOUND PRINTING 115 

Some variation in the speed ratio of the two films will occur due to 
film shrinkage, since the films run at a constant number of frames per 
second. A relative shrinkage ratio of one per cent introduces a rela- 
tive slip between the printing image and the 16-mm. emulsion of 
only 5 x /2 per cent of a wavelength at 10,000 cycles during the time 
that a given element of the sound track is illuminated. During 
operation of the printer the films run at standard speed, and the 
printer is suitable for either daylight or darkroom operation. Fig. 
6 shows the appearance of the converted re-recorder. 

Acknowledgment is due Messrs. E. W. Kellogg, E. Oeller, and 
R. Brady for their work in producing the first successful model of 
the optical reduction printer. 

REFERENCES 

1 SANDVIK, O., HALL, V. C., AND STREIFFFRT, J. G.: "Wave Form Analysis of 
Variable-Width Sound Records," /. Soc. Mot. Pict. Eng., XXI (Oct., 1933), No. 
4, p. 323. 

2 KELLOGG, E. W.: "A New Recorder for Variable-Area Recording," /. Soc. 
Mot. Pict. Eng., XV (Nov., 1930), No. 5, p. 653. 

3 CRABTREE, J.: "Sound Film Printing I," J. Soc. Mot. Pict. Eng., XXI 
(Oct., 1933), No. 4, p. 294, and "Sound Film Printing II," /. Soc. Mot. Pict. 
Eng., XXII (Feb., 1934), No. 2, p. 98. 

4 TUTTLE, C.: "The Relation between Diffuse and Specular Density,"/. Soc. 
Mot. Pict. Eng., XX (March, 1933), No. 3, p. 228. 

6 ZIMMERMAN, A. G.: "Film Recorders," /. Soc. Mot. Pict. Eng., XX (March, 
1933), No. 3, p. 211. 

DISCUSSION 

MR. PALMER: Is any distortion introduced by reducing the 35-mm. sound 
track to 16 mm. laterally? 

MR. SACHTLEBEN: No. There is a true image of the sound track in each of 
the two planes. However, the magnifications in the two planes differ. 

MR. TASKER: At the time the development here described was begun the 
United Research Corporation had already done some months of work with re- 
duction printers and had concluded that it was the one successful method, as 
contrasted with re-recording. I am happy to see that there is now general agree- 
ment in the industry to the effect that reduction printing is the best method of 
producing 16-mm. sound films. 

MR. KELLOGG: On a one-to-one printing, for example, 35- to 35-mm., I doubt 
whether the increased contrast that is helpful in making prints of variable-width 
records would more than offset the slight loss due to lens flare and such optical 
defects. 

The first experiments of which I have any knowledge seemed to indicate that 
contact printing would be somewhat better under such a condition; but in mak- 
ing 16-mm. film, the contact print would necessarily have to be made from l(3-mm. 



116 DIMMICK, BATSEL, AND SACHTLEBEN [J. S. M. P. E. 

negative, whereas the optical print could be made from a negative of much 
larger scale. Owing to the better resolution of the larger-scaled negative the 
blacks would be blacker and the whites cleaner. That is, to my mind, the main 
reason why optical printing seems to work out so well in making 16-mm. re- 
ductions. 

PRESIDENT GOLDSMITH: Is it not a fact in any case that the final preferred 
16-mm. printing methods will not be definitely known until 16-mm. sound prints 
have been produced on a far larger scale? Certainly if only a small edition is re- 
quired, one can take the 35-mm. negative and conveniently reduce it optically, 
particularly if there is no necessity for modifying tone quality or changing volume 
of sound. But if very large editions were required, say, thousands of 16-mm. 
prints, it would not be desirable to preserve the 35-mm. original negative, but to 
proceed rather by contact printing from 16-mm. negatives. 

I do not propose or defend these measures at this time, but I think this is a 
subject that should be carefully studied. Probably the answer can not definitely 
be given until commercial practice in the field has been more nearly crystallized. 

MR. BATSEL: Referring to Mr. Kellogg's discussion, even though we do im- 
prove our negative in optical printing we can not realize the full advantage of 
doing so unless we do have the proper film-moving mechanism. Most of our suc- 
cess in optical printing is due largely to the fact that we have eliminated slippage 
and poor contact, and similar defects. For that reason, I feel that we can put 
10,000 cycles on the 16-mm. film. 

MR. STRICKLER: Which would result in greater loss in reduction sound print- 
ing: to make a 16-mm. dupe negative and then from that a contact positive, or 
to make a dupe 35-mm. negative from which to make the reduction 16-mm. 
prints, assuming that the original negative were not used throughout? 

MR. SACHTLEBEN: I am sure that the qualit3 r would be much better by direct 
reduction from the original or dupe 35-mm. negative than by making a 16-mm. 
negative from the 35-mm. positive and then printing by contact. You would 
lose many or all of the advantages of reduction printing if you were to make 
16-mm. prints in that fashion. 

MR. SANDVIK: You can make a somewhat better print from the 35-mm. 
dupe negative than from the 16-mm. There are optical, photographic, and 
mechanical reasons for that. 

MR. REICHER: In my experience I find that the 35-mm. sound track does 
not wear in reduction printing as it does in contact printing. Therefore, if 
thousands of 16-mm. prints were demanded at some future time from the same 
negative, far fewer reproductions would be required than with 35-mm. I have 
made short loops of 8000-cycle negatives and have run them through the printer 
enough to account for thousands of prints without deterioration. 

PRESIDENT GOLDSMITH: That was the reason why I raised the point that 
there was a necessity for crystallizing commercial practice before the preferred 
path of operations from the 35-mm. original negative to the final 16-mm. positive 
prints can be definitely specified. It might well be that the 16-mm. version would 
sometimes require special editing, as compared with the 35-mm. version. That 
again might profoundly modify the most desirable procedure for making 16-mm. 
prints. 

MR. MITCHELL; Admitting that better results might be achieved by re- 



Aug., 1934] SOUND PRINTING 117 

ducing from the duplicate of the 35-mm. negative, it must be remembered that 
in practice that involves a double printing operation, for the reason that the 16- 
mm. area occupies all the available printing space. It is quite a commercial 
problem to make a 16-mm. master negative, both picture and sound track, at 
one operation. Commercial considerations will in the long run decide the 
question. 

MR. TASKER: Wouldn't it be better to make a 35-mm. master negative 
rather than a 16? 

MR. MITCHELL: You still must consider the 35-mm. picture size as com- 
pared with the 16-mm., referring to printing the picture and sound on the 16- 
mm. In the 35-mm. negatives there is a separation between the pictures, whereas 
there is only a narrow frame line between the pictures in the 16-mm. The 
picture and sound can not be reduced to 16-mm. film in one operation. The 
picture must be reduced by step reduction, and the sound by continuous optical 
reduction. 

MR. TASKER: In the course of preparing the 35-mm. dupe negative, the 
pictures could be magnified as desired. 

PRESIDENT GOLDSMITH: with a different reduction ratio for picture and for 
sound track. 

MR. TASKER: A master 35-mm. negative could be made, properly pre-edited, 
as Dr. Goldsmith suggested, for the double sprocket hole standard and reduced 
in a single printing operation, which you suggest as being desirable. On the other 
hand, that can not be done very well for the single sprocket hole standard, in 
view of the fact that the transverse and longitudinal reductions of the sound 
track must be different unless a non-standard, 35-mm. (say, 38- or 40-mm.) dupe 
negative from which one row of sprocket holes has been omitted is provided for 
the purpose. That is a very obvious disadvantage, of course, for the double 
sprocket hole type of 16-mm. film. 

MR. MITCHELL: With the 35-mm. master positive the space between the 
35-mm. pictures must still be eliminated in the 16-mm. print, whether with one 
or two rows of sprocket holes. It would be commercially impracticable to con- 
sider 38-mm. or other off-standard film for the master negative. 

BOOK REVIEW 

The Complete Projectionist. R. H. Cricks. Kinematograph Publications, 
Ltd., London, 1933, 231 pp. 

Projectionists will undoubtedly welcome this new handbook for two reasons: 
(1) it represents a concise statement of the subject, and (2) it may be slipped into 
the pocket easily because of its small size. Both these characteristics should en- 
courage wide reading of the book. The book contains 16 chapters and 7 appen- 
dixes as well as an index. A useful feature of the latter is that all matter related 
to troubles is set in bold-faced type. Numerous illustrations and diagrams aid in 
clarifying the text. The closing chapter deals briefly with forthcoming develop- 
ments, such as color films, stereoscopy, non-intermittent projection, and tele- 
vision. Many useful tables are included in appendix sections. 

G. E. MATTHEWS 



OFFICERS AND BOARD OF GOVERNORS 





L. A. JONES H. C. SILENT 

Engineering V ice-President Executive Vice-P resident 



J. I. CRABTREE 
Editorial Vice-President 





ALFRED N. GOLDSMITH 
President 




O. M. GLUNT 
Financial Vice-P resident 

118 



W. C. KUNZMANN 

Convention Vice-President 




OFFICERS AND GOVERNORS 



119 



J. H. KURLANDER 

Secretary 




T. E. SHEA 
Treasurer 




A. S. DICKINSON 
Governor 



H. T. COWLING 
Governor 




W. B. RAYTON 
Governor 





H. GRIFFIN 
Governor 



R. E. FARNHAM 
Governor 



120 



OFFICERS AND GOVERNORS 






H. G. TASKER 

Chairman, Atlantic Coast 
Section 



E. COUR 

Chairman, Mid-West 
Section 



E. HUSE 

Chairman, Pacific Coast 
Section 



SOCIETY ANNOUNCEMENTS 



BOARD OF GOVERNORS 

At a meeting of the Board of Governors held July 16th, tentative plans for 
le Fall, 1934, Convention were formulated, as described below, and nomina- 
tions for officers of the Society for the calendar year 1935 were completed. Voting 
ballots will be mailed to the Honorary Members, Fellows, and Active Members 
on or about September 19th, and the results of the election will be announced 
at the Fall Convention. 

Various administrative and fiscal matters engaged the attention of the Board; 
and the Financial Vice-President, Mr. O. M. Glunt, reported that the Society 
was operating satisfactorily within its budget. Increased impetus is to be given 
to the membership campaign, which had shown signs of lagging during the 
summer months. 

FALL CONVENTION 
HOTEL PENNSYLVANIA, NEW YORK, N. Y., OCTOBER 29-NOVEMBER, 1, 1934. 

The Fall, 1934, Convention will be held at the Hotel Pennsylvania, New York, 
N. Y., Oct. 29th-Nov. 1st, inclusive. Mr. J. I. Crabtree, Editorial Vice-President, 
with the assistance of Mr. J. O. Baker, Chairman of the Papers Committee, 
is arranging an interesting program of technical papers, presentations, and 
lectures; and Mr. W. C. Kunzmann, Convention Vice-President, is completing 
arrangements with the Hotel for most attractive accommodations for the mem- 
bers and their guests and facilities for the Convention. 

Mr. H. Griffin will be in charge of the projection equipment; Mr. J. Frank, 
Jr., of the Apparatus Exhibit; and Mrs. O. M. Glunt will act as hostess, assisted 
by her Ladies' Committee. 

The possibilities of arranging interesting trips or tours of inspection of studios 
or manufacturers' plants are being studied; and plans are being made to provide 
several outstanding figures of the motion picture industry as speakers for the 
Semi- Annual Banquet, to be held on Wednesday, October 31st, in the Grand 
Ballroom of the Hotel. 



121 



STANDARD S. M. P. E. 

VISUAL AND SOUND TEST REELS 

Prepared under the Supervision 

OF THE 
PROJECTION PRACTICE COMMITTEE 

OF THE 
SOCIETY OF MOTION PICTURE ENGINEERS 



Two reels, each approximately 500 feet long, of specially pre- 
pared film, designed to be used as a precision instrument in 
theaters, review rooms, exchanges, laboratories, and the like 
for testing the performance of projectors. The visual section 
includes special targets with the aid of which travel-ghost, 
lens aberration, definition, and film weave may be detected 
and corrected. The sound section includes recordings of 
various kinds of music and voice, in addition to constant 
frequency, constant amplitude recordings which may be used 
for testing the quality of reproduction, the frequency range 
of the reproducer, the presence of flutter and 60-cycle or 96- 
cycle modulation, and the adjustment of the sound track. 
Reels sold complete only (no short sections). 

PRICE $37.50 FOR EACH SECTION, 
INCLUDING INSTRUCTIONS 

(Shipped to any point in the United States) 

Address the 

SOCIETY OF MOTION PICTURE ENGINEERS 

HOTEL PENNSYLVANIA 
NEW YORK, N. Y. 



JOURNAL 



OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 

Volume XXIII SEPTEMBER, 1934 Number 3 



CONTENTS 

Page 

C. Francis Jenkins: An Appreciation L. C. PORTER 126 

The Biplane Filament in Spotlighting G. MILI 131 

Reciprocity Law Failure in Photographic Exposures 

L. A. JONES AND J. H. WEBB 142 

A Motion Picture Negative of Wider Usefulness. .P. ARNOLD 160 

Recent Optical Improvements in Sound-Film Recording Equip- 
ment W. HERRIOTT AND L. V. FOSTER 167 

Pioneering Inventions by an Amateur F. E. IVES 175 

Society Announcements 182 



JOURNAL 

OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 



SYLVAN HARRIS, EDITOR 

Board of Editors 
J. I. CRABTREB, Chairman 

O. M. GLUNT A. C. HARDY L. A. JONES 

J. O. BAKER 



Subscription to non-members, $8.00 per annum; to members, $5.00 per annum, 
included in their annual membership dues; single copies, $1.00. A discount 
on subscriptions or single copies of 15 per cent is allowed to accredited agencies. 
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton 
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y. 

Published monthly at Easton, Pa., by the Society of Motion Picture Engineers 

Publication Office, 20th & Northampton Sts., Easton, Pa. 
General and Editorial Office, Hotel Pennsylvania, New York, N. Y. 
Entered as second class matter January 15, 1930, at the Post Office at Easton, 
Pa., under the Act of March 3, 1879. Copyrighted, 1934, by the Society of 
Motion Picture Engineers, Inc. 

Papers appearing in this Journal may be reprinted, abstracted, or abridged 
provided credit is given to the Journal of the Society of Motion Picture Engineers 
and to the author, or authors, of the papers in question. Exact reference as to 
the volume, number, and page of the Journal must be given. The Society is 
not responsible for statements made by authors. 



Officers of the Society 

President: ALFRED N. GOLDSMITH, 444 Madison Ave., New York, N. Y. 
Executive- Vice-President: HAROLD C. SILENT, 7046 Hollywood Blvd., Los 

Angeles, Calif. 

Engineering Vice-P resident: LOYD A. JONES, Kodak Park, Rochester, N. Y. 
Editorial Vice-President: JOHN I. CRABTREE, Kodak Park, Rochester, N. Y. 
Financial Vice-President: OMER M. GLUNT, 463 West St., New York, N. Y. 
Convention Vice-President: WILLIAM C. KUNZMANN, Box 400, Cleveland, Ohio. 
Secretary: JOHN H. KURLANDER, 2 Clearfield Ave., Bloomfield, N. J. 
Treasurer: TIMOTHY E. SHEA, 463 West St., New York, N. Y. 

Governors 

EUGENE COUR, 1029 S. Wabash Ave., Chicago, 111. 

HBRFORD T. COWLING, 4700 Connecticut Ave., N.W., Washington, 

D.C. 

ARTHUR S. DICKINSON, 28 W. 44th St., New York, N. Y. 
RALPH E. FARNHAM, Nela Park, Cleveland, Ohio. 
HERBERT GRIFFIN, 90 Gold St., New York, N. Y. 
EMERY HUSE, 6706 Santa Monica Blvd., Hollywood, Calif. 
WILBUR B. RAYTON, 635 St. Paul St., Rochester, N. Y. 
HOMER G. TASKBR, 41-39 38th St., Long Island City, N. Y. 




C. FRANCIS JENKINS 



C. FRANCIS JENKINS 

(1867-1934) 

With the death of C. Francis Jenkins, June 6, 1934, our Society 
lost not only its founder, but also one of the inventors of the motion 
picture projector, around which the entire industry has been built 
up. Those of us who had the privilege of knowing Mr. Jenkins 
intimately knew him as a man of great imagination and boundless 
energy, evidenced by something over four hundred patents in his 
own name, both here and abroad. 

On various occasions he had to leave his beloved laboratory and 
devote his attention to raising sufficient funds to carry on his prime 
work research and invention. His indomitable will and faith can 
not be better indicated than by quoting a statement that he often 
made and evidently thoroughly believed, "If a thing is very difficult 
it is as good as accomplished; if it is impossible it will take a little 
time." 

In his laboratory he surrounded himself with young men and young 
women because, as he put it, "If Jenkins tells them it can be done, 
they believe it." Once Mr. Jenkins hired a brilliant scientist from 
one of the great research laboratories of the country. The scientist 
did not last long because, as Jenkins said, "He spent too much time 
proving why it wouldn't work instead of figuring out how to do it." 

Mr. Jenkins was a true and loyal friend; a hard fighter, loved 
by those who knew him well, and respected by even his business 
enemies, of whom he had a few invariably the price of success. 

In his home life I have never seen a more beautiful relationship 
between man and wife. Mrs. Jenkins was his sweetheart to the 
very end, and he treated her, both in private and in public, as a 
youthful lover. They had no children but were continually doing 
things for their nieces and nephews and the children of their friends. 
Jenkins was always trying to help young people to get a start 
finanically. 

Just before the depression Jenkins sold his business. His manner 
of disposing of the tidy sum he received was very characteristic of 
the man. First he created a trust fund to take care of Mrs. Jenkins 
126 



C. FRANCIS JENKINS 127 

for the rest of her life. The remainder of the money he and Mrs. 
Jenkins gave away outright and unconditionally to poor relatives, 
friends, and servants whom they had had from time to time. 

Like many inventors Jenkins was of a high-strung, nervous tempera- 
ment. At times when he would get too fidgety and nervous to work, 
he would leave his laboratory and pilot his private plane up into the 
great blue reaches of the sky, where he found peace and quietness to 
rest his nerves. Often his wife, good sport that she was, would go 
with him on those flights. 

About 1930 Mr. Jenkins' health began to fail. His heart made it 
necessary for him to drop most of his active work at his laboratory. 
The majority of his time thereafter was spent quietly, though rest- 
lessly, at his home in Washington. 

Probably realizing that his years were numbered, he wrote his 
autobiography and published it in 1931 as a book entitled The 
Boyhood of an Inventor from which the following data are drawn 
largely. 

A red-headed boy, C. Francis Jenkins, was born of Welsh-French 
parents Quakers near Dayton, Ohio, in 1867. When he was 
about two years of age his parents moved to a farm near Richmond, 
Indiana. His early boyhood was spent in the log cabin home on that 
farm. Like many other farm boys Jenkins learned various things by 
experience and hard knocks. He early began to show great interest 
in mechanical things. Hours were spent turning the hand-wheel 
of his mother's sewing machine and trying to puzzle out the mechanics 
of the sewing. Other lessons were learned from the spinning-wheel, 
the flax-break, the wool-carder, the butter-churn, the log-lever cheese 
press, the winnowing mill, and such early mechanical aids that have 
long since been superseded but that nevertheless utilized many of 
the principles of mechanics of modern machinery. 

Probably his earliest invention was a bean-shelling machine which 
he made as a boy. Following that, he invented a jack to lift wagon 
wheels for greasing purposes. Some of them he painted bright 
colors, and in selling them he learned one important business principle, 
i. e., that appearance goes a long way in selling an article. 

Jenkins' early schooling was at the little country school to which 
he walked three miles from his house and three miles back again. 
This was followed by high school and Earlham College. Later in 
life his College gave him the honorary degree of Doctor of Science 
(1929). While at school the school board gave him a Ley den jar 






128 C. FRANCIS JENKINS [J. S. M. p. E. 

and a static machine, because nobody else knew how to work them. 
That was probably the start of his interest in electricity, which was 
to play so great a part in his success in later life. 

Jenkins also learned that hydrogen gas made from sulphuric acid 
and zinc would fill paper bags and cause them to rise like balloons. 
Perhaps those experiments implanted in his mind the seed of a de- 
sire to fly. After he was fifty years old he bought his first aeroplane 
and received his pilot's license. 

Parties in his youth usually furnished their own entertainment. 
The games played were those of mental skill, cleverness, quickness; 
tricks vSuch as trying to blow a card from off a spool by blowing 
through the hole involving a principle of aerodynamics; turning a 
tumbler of water upside-down on a card, and the like far different 
from the hired entertainment furnished the present-day youth. 

Jenkins' father was progressive, although not inventive nor 
particularly mechanical. He used machinery of the latest type on 
his farm, and it was Jenkins' particular job to keep all the me- 
chanical gadgets operating and in repair. He proved so adept at the 
job that he built up quite a reputation in the neighborhood as a 
clever mechanic. The day he saw his first locomotive he ran off 
from his family, who were meeting friends at the rear of the train, 
and spent his time studying the engine. Later he found out enough 
about its operation so that he borrowed a locomotive and took his 
girl for a ride. 

When he was a young man his desire to "go places and do things" 
took him to the Pacific Coast. There he worked in lumber camps, 
on a ranch, and down in Mexico in a mine. His first job in the 
lumber camp was riding logs. The first day was a series of spills into 
the water, but his persistence kept him at it all day long, even though 
soaking wet, and he soon learned the trick. His indomitable will and 
persistence were characteristics that contributed greatly toward his 
success. 

As a result of a Civil Service examination he received an appoint- 
ment as a clerk to Sumner I. Kimball, the founder of our life- 
saving service, which is now the U. S. Coast Guard. This position 
brought him to Washington, D. C., where a few years later he resigned 
to start on his real life work, inventing. 

It was at Washington that he met and married Grace Love, of 
whom he writes in his book, "Perhaps the turning point came when 
he married that wonderful girl, 'Miss Grace,' who had endeared 



>t., 1934] C. FRANCIS JENKINS 129 

icrself to everyone by her sympathetic understanding and un- 
selfishness, winning the hearts and confidences of all who came 
in contact with her. It is to her kindly help and business widsom, 
rather than to any personal 'genius,' that this inventor attributes 
such success as has attended his efforts." 

Jenkins built the first horseless carriage in Washington a small 
steam car and went broke trying to promote it. Later he developed 
the self-starter for automobiles, which proved to be a financial success. 

Photography and the projection of motion pictures were really 
his life's great work. In addition to his work on the development 
of the motion picture projector, he made many contributions to the 
motion picture art. Notable among them are the first fire-proof 
projector really the foundation of the home and school movies of 
today; a high-speed camera for showing in slow motion such things 
as the flight of a projectile, Bobby Jones' golf drive, etc. His Chrono- 
teine camera takes 3200 separate exposures in one second; the 
film moves through it so rapidly that 400 feet of film can be shot up 
into the air before the first end falls to the ground. 

Jenkins early recognized the need of standardization in the motion 
picture industry. The need was stimulated by the World War, and 
to meet the demand Jenkins founded the Society of Motion Picture 
Engineers in 1916 and became its first president. That organization 
is today international in scope. It is the outstanding organization 
in motion picture engineering, and its standards have attained world- 
wide recognition. Its Transactions and JOURNAL form the greatest 
technical library pertaining to motion pictures in existence. 

In 1921, Jenkins set up his own research laboratory at Washington, 
D. C. It was in this laboratory that Jenkins developed the prismatic 
ring, a device for producing a smoothly oscillating beam out of a 
continuous beam of light. As time went on, Jenkins became inter- 
ested in radio. By conducting tests with his own aeroplane he dis- 
covered that a radio "shadow" was cast behind a metal plane and 
that an antenna flown in that area could be used for two-way tele- 
phone conversation without interference from engine ignition. 

Sending photographs by radio, and later by television, interested 
Jenkins greatly. I shall never forget the thrill of standing in his 
laboratory and having a photograph of my daughter transmitted 
over the regular telephone line to the U. S. Naval broadcasting 
station at Anascostia, Md. There it was broadcast by radio, picked 
up in the Jenkins laboratory, and reproduced at the side of the sending 



130 C. FRANCIS JENKINS 

device. Jenkins established his own station for broadcasting motion 
pictures by radio. Nightly entertainment of that sort was trans- 
mitted from his station, W3XK. Relatively simple and inexpensive 
receivers had been developed by Jenkins and sold practically at 
cost to thousands of radio fans all over the country. 

A more complicated machine for receiving weather bureau maps 
by radio was developed and installed on many of the Government 
ships. Jenkins had the fullest cooperation of the U. S. Bureau of 
Standards, the Army, and particularly the Navy, in testing out his 
many inventions, some of which were purchased by the Government 
and put into regular service. 

As often happens to a man who works so intensively, his health 
began to fail. As a result, in 1930 he sold out his principal business, 
the Jenkins Television Corporation. A failing heart kept him more 
and more at home until his death in 1934. With his passing went one 
of the ten men in the United States having over three hundred 
patents in their own name. He was a man of great vision, with the 
courage of his convictions; a man of indomitable will and boundless 
energy; a man having great love for his fellow men, a fine Christian 
character respected by all who knew him and loved by those who had 
the opportunity of being associated with him. Perhaps the greatest 
monument to him is the continued success of the Society he founded 
and for which he worked so hard in its early struggle for recognition. 

L. C. PORTER 



THE BIPLANE FILAMENT IN SPOTLIGHTING* 
GJON MILI** 

Summary. The high degree of uniformity and source of brightness that have 
made the biplane filament so desirable for motion picture projection prove to be 
valuable also in spotlighting. The two parallel rows of coils placed so that the coils 
of one plane fill the spaces between the coils of the other provide a light source of 
greater uniformity and double the average brightness of the monoplane filament 
construction. Results are given showing the increased uniformity of the spot and the 
higher intensities attained with biplane filament lamps as compared with monoplane 
filament lamps of the same rating. The three types of spotlights most commonly 
used namely, the lens spotlight, the shallow paraboloid, and the stereopticon spot- 
lighthave been subjected to test to determine their operating results. 

The advantages of the biplane filament for motion picture pro- 
jection were reported two years ago. 1 Like motion picture pro- 
jection, spotlighting is a form of light projection, and the advantages 
of the biplane filament in the one field apply to a large extent in the 
other. Two types of filament construction are at present in common 
use as light sources for spotlighting: the barrel-shaped (C-5) and 
the monoplane (C-13). The latter predominates in the higher- 
wattage equipment designed for the studio and the theater, and it is 
with that type of spotlighting that the following analysis is chiefly 
concerned. 

Light Source Characteristics. Compared with the monoplane 
filament construction, in which the coils are all placed in one plane 
with intervening dark spaces, the biplane staggered-filament con- 
struction consists of two parallel rows of coils so placed that the 
coils of one plane fill the spaces between the coils of the other, thus 
providing a light source of greater uniformity and increased average 
brightness. For a given electrical rating the biplane source occupies 
approximately half the area and therefore is almost double the 
average brightness of the monoplane filament. 

Fig. 1 illustrates the reduction of the size of the source and the 
increase in brightness and uniformity produced by the biplane 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Westinghouse Lamp Company, Bloomfield, N. J. 

131 



132 



G. MILI 



[J. S. M. P. E. 



(C-13D) construction as compared with the monoplane (C-13) of 
identical electrical rating. Light sources rated at 2 kw., 115 volts, 
were photographed with and without a spherical silvered glass re- 
flector. 

Test Procedure. A series of tests was conducted to determine the 
operating results obtained with the three kinds of spotlight most 

2-Kw. 115-Volt Biplane Filament 
(A) With reflector (B) Without reflector 




2-Kw. 115-Volt Monoplane Filament 
(C) With reflector (>) Without reflector 





Ratio 
A/C 

B/D 



Source Area 

0.56 
0.58 



Brightness 
1.49 

1.80 



FIG. 1. Relative light-source area and uniformity 
of monoplane and biplane filament lamps of the same 
electrical rating. 



commonly used: namely, the lens spotlight, the shallow paraboloid, 
and the stereopticon spotlight. Candle-power measurements were 
made by means of a calibrated light-sensitive cell, the test distance 
being 60 feet for the lens spotlight and 100 feet for the paraboloid. 
Relative measurements of the light output of the stereopticon spot- 
light at various apertures were made with a 30-inch integrator pro- 



>t., 1934] 



BIPLANE FILAMENT IN SPOTLIGHTING 



133 



r ided with a circular diffusing glass window. The test unit was so 
placed that the projected beam came well within the circumference 
of the diffusing window. 

Two-kw , 115-volt spotlight lamps of biplane and monoplane 
filament construction, such as shown in Fig. 2, were used in all tests. 
Lamp A has a monoplane filament; B and C, biplane filaments. 
Lamps A and C are designed to be operated with the base down; 
lamp B, with the base up. 

The Lens Spotlight. Where mobility and great variation of the 
size and intensity of the spot are required, a lens spotlight such as 
illustrated in Fig. 3 is most commonly used. In a unit of this type 




(A) (B} (Q 

FIG. 2. Two-kw., 115-v. spotlight lamps: (A) monoplane; 
(B,C) biplane. 



the intensity and spread of the beam depend upon the distance 
from the filament to the lens. The curves of Fig. 4 show the com- 
parative beam spreads and the intensities at the centers of the 
beams of biplane and monoplane filament lamps for filament-to-lens 
distances ranging from 4 to 13 inches. It is apparent that when the 
lamp is positioned for a relatively small beam spread, the biplane 
filament provides much greater intensities than the monoplane. 
However, there is no appreciable difference of performance between 
the two types of filament when the lamp is drawn close to the lens 
in order to attain a wide spread. As may be noticed in the curves, 
maximum intensity occurs when the filament is focused sharply 



134 



G. MILI 



[J. S. M. P. E. 



in the plane of test. Such a spot, however, is hardly uniform enough 
to warrant its use. Instead, by drawing the filament to a point 
slightly behind the focus, a more uniform spot can be obtained 
without much loss in candle-power. This is the position marked as 
the plane of minimum effective divergence. The candle-power distribu- 
tion of the beam, with the filament at the position of minimum 
effective divergence, is plotted in Fig. 5, the biplane showing a 90 
per cent increase over the monoplane. Fig. 6, showing the beam 
patterns at the position of minimum effective divergence, brings out 
another advantage of the biplane filament when the unit is adjusted 
so as to produce a relatively small spot: namely, the marked uni- 




FIG. 3. Lens spotlight in operation. 



formity of the spot. Actually, the striations shown in the beam 
pattern of the monoplane filament are even more objectionable to 
the eye than they appear in the illustration, because they represent 
not only a variation of intensity but also marked color fringes due to 
chromatic aberrations of the lens. 

The Shallow Paraboloid. For such applications as require a highly 
concentrated beam with extremely high intensities, i. e., several 
million cp., a projector equipped with a parabolic mirror of fairly 
large diameter (18, 24, or 36 inches) may be used to great advantage. 
In Fig. 7 are data obtained with biplane and monoplane filament 
lamps used with a silvered glass parabolic reflector (diam. = 25 in., 
/ = 10 in.) with the projected beam focused in the plane of test. 
The superiority of the biplane type of filament over the monoplane 



Sept., 1934] 



BIPLANE FILAMENT IN SPOTLIGHTING 



135 



both as to intensity and uniformity is again evident. While neither 
spot is perfectly uniform, experience has shown that a plain glass door 
or a slightly convex lens of the pressed type will completely smooth 
out the beam of the biplane filament lamp. The increase in the 
maximum candle-power attained with the biplane filament over the 
monoplane is about 50 per cent. The test projector and the method 




la 10 8 6 

DISTANCE FROM FILAMENT TO LENS IN INCHES 

FIG. 4. Relative cp. and beam spread throughout range 
of lamp movement in lens spotlight equipped with biplane 
and monoplane lamps. [Plano-convex lens (dia. = 6", / = 
12"); 2-kw., 115-v. G-48 bulb spotlight lamp.] Solid curves, 
biplane (C-13D); broken curves, monoplane (C-13). 

of measuring the intensities are illustrated in Figs. 8 and 9, respec- 
tively. 

The Use of an Auxiliary Reflector. When employed with a shallow 
paraboloid or a lens, both monoplane and biplane filament lamps 
can be rendered more efficient by the addition of an auxiliary spherical 
reflector. The auxiliary reflector is so placed as to gather the light 
radiated in the direction opposite to the main optical element, 



136 



G. MILI 



[J. S. M. P. E. 



whether lens or reflector, and is focused to produce an image in 
the plane of the filament. This is illustrated in Fig. 1. The reflected 
light filters through the interstices between adjacent coils, and also 



















1 




















































/ 


N 1 




























s 






















y 




s 


























/ 


























/I 


M 
























/ 






\ 












IS1 


AN 


CE 


r 


/I 

LAME 


NT 


TO 


-Eh 


s 


-- 


_ 











5IS 


TA^ 


ICE f 


IL> 


Mi 


Nl 


Vc 


.E 


IS 


- t: 


f-- 








\ 






















X 










j 
























\\ 










\ 




















I T 
























\\ 










\ 












1 










/ 
























\\ 






























/ 








^ 
















\ 


, x 






^ 














UJ 

a > 8 










u 


/ 


^ 


VX 
















































| / 








V 
















[ 






















o^ 










jly 
























I 












\ 


















y| 




































\ 

" 




















Tj 










\ \ 












I 


\ 




























1 


/ 










V 












1 


\ 






























1 














\ 


\ 










* I 
















V 














1 1 
















v . 








/ 


J 
















\ 


\ 






f 4 






/ 


1 
















\ 


V 




^ 


S 




JL 














^s, 









s 


S 






















1 


f 3 




+ r <f f ', 


J 3* A 


f y ? f o' C 2' ? 4 



ANGULAR SPREAD 



ANGULAR SPREAD 



FIG. 5. In a lens spotlight, with the lamp at position of mini- 
mum effective divergence, a large increase of candle-power is pos- 
sible by substituting a biplane for a monoplane filament lamp. 
[Plano-convex lens (dia. = 6", / = 12"); 2 kw. 115-v. G-48 bulb 
spotlight lamp.] Solid curves, biplane (C-13D); broken curves, 
monoplane (C-13). 



Biplane Filament 



Monoplane Filament 




FIG. 6. Appearance of spot at position of minimum 
effective divergence, showing increase of uniformity at- 
tained with biplane lamp. [Plano-convex lens (dia. = 
6", / = 12"); 2-kw. 115-v. G-48 bulb spotlight lamp.] 

through the spaces between wire turns of the coils themselves, thereby 
increasing the quantity of light directed into the lens or paraboloid. 
As may be seen from Table I, an increase of illumination of 67 per 



Sept., 1934] BIPLANE FILAMENT IN SPOTLIGHTING 

VERTICAL DISTRIBUTION HORIZONTAL DISTRIBUTION 



137 



\ 




iNGULAR SPREAD 



ANGULAR SPREAD 



FIG. 7. In a parabolic projector greater candle-power and 
smaller beam spread may be attained by substituting for a 
monoplane filament lamp a biplane of equal electrical rating. 
[Commercial parabolic silvered glass reflector (dia. = 25", / = 
10"); 2-kw., 115-v. G-48 bulb spotlight lamp.] Solid curves, bi- 
plane (C-13D}\ broken curves, monoplane (C-13). 




FIG. 8. A projector drum containing parabolic reflector, shown on test 
trunnion, which provides angular adjustment in vertical and horizontal planes. 

FIG. 9. Candle-power measurements made with calibrated light- 
sensitive cell. 



138 



G. MILI 



[J. S. M. P. E. 



cent may be attained with the monoplane when the image from a 
silvered glass mirror is enmeshed between the coils ; but the increase 
is only 39.6 per cent when the image is superposed on the coils them- 
selves. Accordingly, to insure the best results and most uniform 
performance with the monoplane, the mirror must be reset accur- 
ately at each renewal of the lamp. With the biplane, where the 




i i 



12345 

AREA OF APERTURE IN SQUARE INCHES 

FIG. 10. The light output of a stereopticon spotlight 
is greater with a biplane than with a monoplane lamp 
throughout the range of operating apertures. [Stere- 
opticon spotlight with deep ellipsoid, square aperture, 
and projection lens (dia. = 8", / = 12"); 2-kw., 115-v. 
T-32 bulb spotlight lamp.] Solid curve, biplane 
(C-13D); broken curve, monoplane (C-I3). 

mirror image falls upon the filament itself, only 35-40 per cent may be 
gained. But, on the other hand, the mirror setting is not so critical 

TABLE i 

Effect of Spherical Mirror on Beam Illumination 
Monoplane Filament Lamps Held at Constant Voltage 

Lamp Current Illumination 

No Mirror 100 100 

Mirror Image between Coils 99.5 167.0 

Mirror Image over Coils 98.7 139.6 






Sept., 1934] 



BIPLANE FILAMENT IN SPOTLIGHTING 



139 



as with the monoplane, and prefocus-base lamps perform satis- 
factorily without necessity of readjusting the mirror when a burned- 
out lamp is replaced by a new one. 

The Stereopticon Spotlight. Stereopticon spotlights may be 
divided into two groups, according to the optics employed in their 
design. The first group duplicates the optics embodied in a motion 
picture projector, except for the fact that the aperture size and 
shape may be varied. The advantages claimed for the biplane in 
motion picture projection 1 apply equally well to this type of spot- 
light. There remains the second group, in which the optical system 
consists, as a rule, of a lamp with the filament placed at the principal 
focus of a deep elliptical reflector, which acts as a light-gathering 
element ; an aperture of varying size and shape at a suitable position 




Fig. 11. Deep ellipsoid Stereopticon spotlight. 

FIG. 12. Integrating photometer used for measurements of light output 
in projected beam. 

near the conjugate focus; and a plano-convex lens that projects an 
enlarged image of the aperture in the plane of illumination. With a 
deep reflector the lamp should be mounted with the plane of the 
filament along the axis of the reflector. 

Two advantages may be claimed for the deep ellipsoid spotlight 
as compared with the lens spotlight: first, the higher efficiency; 
and, second, the sharpness and flexibility of outline of the beam spot. 
The intensity at the center of the beam is the same for all apertures, 
although the edge brightness decreases as the size of the aperture 
increases. Fig. 10 shows graphically, for various apertures, the total 
light output of a unit of this type equipped with biplane and mono- 
plane filament lamps of equal electrical rating. The total light 



140 G. MILI [J. S. M. P. E. 

output with the biplane lamp is about 40 per cent greater than with 
the monoplane. The stereopticon spotlight used in the test, and 
the method of measuring the total light output by means of the 
integrating photometer, are illustrated in Figs. 11 and 12, respec- 
tively. 

Conclusion. The test results and photographs presented show 
the improvement achieved in the performance of the unit by sub- 
stituting the biplane filament for the monoplane, in three types of 
spotlight: namely, the lens spotlight, the shallow paraboloid, and the 
stereopticon spotlight. With the first two types, in which the posi- 
tion of the filament may be varied, the advantages of the biplane 
are most marked when the filament is at or near the optical focus. 
With the stereopticon spotlight, in which the position of the filament 
is fixed, the advantages of the biplane are maintained throughout the 
range of operating apertures. The data presented and the conclusions 
reached will apply equally well to spotlights similar in design to the 
units tested, and to lamps of other wattages. 

REFERENCE 

1 MILI, J. T.: "Biplane Filament Construction A High-Intensity Incan- 
descent Lamp Light-Source for Motion Picture Projection," /. Soc. Mot. Pict. 
Eng., XIX (July, 1932), No. 1, p. 829. 

DISCUSSION 

MR. JOY : The speaker stated that the intrinsic billiancy of a tungsten filament 
is considerably increased by using a coil construction. How great is that increase? 

MR. MILI: The intrinsic brilliancy of a 2-kw. filament such as that used in 
the test is about 1350 candles per sq. cm. on the outside and 3000 candles per 
sq. cm. on the inner surface of the coil. The temperature of the inner surface 
is at most only a few degrees higher than on the outside, and the increase of 
brightness is due almost entirely to the reflection of light made possible by coiling 
the filament. This increase of brightness by means of reflection occurs not only 
at the inner surface, but also at portions of the outer surface adjacent to another 
coil. 

MR. MANHEIMER: Table I indicates that the lamp current is less when a 
spherical reflector is used, the voltage remaining unchanged. Is that due to an 
increase of the filament temperature? 

MR. MILI: The resistance of tungsten wire increases with the temperature. 
Accordingly, a filament that is operated at constant voltage will draw less than 
the rated current when its temperature is raised above normal by some 
external means. As shown in Table I, the heat reflected by the spherical mirror 
will cause a larger decrease of current, and hence a greater increase of filament 
temperature, when the image falls on, instead of between, the coils. The increase 
of temperature due to the mirror image is compensated for when designing the 



Sept., 1934] BIPLANE FILAMENT IN SPOTLIGHTING 141 

lamp, in order that the life of the lamp may be maintained at the established 
figures. 

MR. RICHARDSON: What, in ordinary service, is the rate of deterioration of 
the surface of the auxiliary reflector, and how easily can it be kept clean? 

MR. MILI: In studio spotlighting we deal with lamps that consume power of 
the order of two, five, and ten kilowatts. The auxiliary reflector is placed only 4 
to 6 inches away from the filament, and is subjected to the heat radiated by these 
lamps. On account of the heat, first-surface reflectors are likely to tarnish, at a 
rate that depends upon operating conditions and the kind of metal used. Silvered 
glass mirrors do not tarnish, because the reflecting surface is protected from 
atmospheric action, unless the backing chips off, although the glass may crack if 
strains are caused by the supporting mechanism. Metal reflectors may be 
cleaned with ordinary polishing compounds, whereas occasional wiping with a 
clean cloth will be sufficient to ensure good performance with glass mirrors. 

MR. PALMER: Since the biplane filament is practically a full source of light, 
how is it possible to increase the illumination by using a spherical mirror with the 
biplane filament? Can the projected beam be rendered more uniform by placing 
the mirror image slightly out of focus? 

MR. MILI : The increase of illumination resulting from using a spherical mirror 
with the biplane filament is due partly to the reflected light that filters through 
the coils between turns of the filament, and partly to the light that passes back 
between the coils, especially at lateral angles of 35 to 45 degrees on either side of 
the optical axis; and, finally, to the rise in filament temperature caused by the 
mirror image. 

If the spherical mirror image is focused behind the plane of the filament, the 
reflected light will be localized at the center of the beam, sometimes resulting 
in disturbing filament images. If the image is focused ahead, the reflected beam 
will be wider than the direct beam, thereby causing a dim ring of light around the 
beam spot. 

MR. PALMER: What would be a practical way of positioning a spherical 
mirror with a biplane filament lamp? 

MR. MILI: If prefocus lamps are used, a very practical way would be to 
position the mirror with a monoplane lamp, and then to replace the monoplane 
with the biplane. A more accurate method would be to focus the mirror so as to 
produce an image equal in size to, and at one side of, the filament; and then, by 
revolving the mirror, to superpose the image upon the filament so as to fill the 
spaces between coils at lateral angles from the optical axis. 

MR. TUTTLE: Why is the conventional type of relay system, using a con- 
denser and a field lens, not used more in this sort of spotlighting equipment? 

MR. MILI: Such a system has been suggested, since it would improve the 
uniformity of the spot. The field lens would, however, increase the cost of the 
unit, add weight, and make it appear more complex. 



RECIPROCITY LAW FAILURE IN PHOTOGRAPHIC 
EXPOSURES* 

LOYD A. JONES AND J. H. WEBB** 

Summary. Reciprocity law failure is dealt with from the standpoint of its appli- 
cation to practical photographic exposures. Reciprocity failure and the manner of 
its portrayal are first briefly and simply described. It is then shown how the reci- 
procity failure diagram can be interpreted to show the behavior of time-scale and in- 
tensity-scale H&D curves, with regard to speed and contrast, for widely different 
ranges of intensity corresponding to those existing in certain definite classes of photo- 
graphic work. Actual reciprocity curves for a number of commercial emulsions are 
included in the paper. 

INTRODUCTION 

A perusal of the literature which has appeared during the past 
thirty or forty years relating to the scientific and theoretical aspects 
of photography reveals many references to the "failure of the reci- 
procity law." Much of the earlier investigational work on this sub- 
ject was done by astronomers who were forced to make very long 
exposures with extremely low illuminations on the photographic 
material. It was quite evident from their experimental work that 
a much smaller photographic effect was produced under these condi- 
tions of low illumination than when exposures were made with higher 
illuminations, even though the product of illumination by the ex- 
posure time was kept the same in the two cases. It has been known 
for many years, therefore, that, at least under certain conditions, it 
is not justifiable to assume that the photographic effect produced 
by a constant exposure is independent of the intensity level at which 
the exposure is made. 

In many fields of photographic work, such, for instance, as por- 
traiture, landscape photography, and motion picture photography, 
the variations in the photographic effect resulting from equal expo- 
sures at the various practically available illumination levels are not 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. Communica- 
tion No. 531 from the Kodak Research Laboratories. 

** Eastman Kodak Co., Rochester, N. Y. 
142 



RECIPROCITY LAW FAILURE 143 

sufficiently great to be of much importance. Workers in this field, 
therefore, have not paid much attention to the failure of the reci- 
procity law. The relation between the time and intensity factors 
of exposure are of great interest, however, to those investigators 
chiefly concerned with the theory of photographic exposure and la- 
tent image formation, and a study of the literature shows that many 
investigations of the reciprocity law failure have been made for the 
specific purpose of finding out more about the nature of the latent 
image. 

During recent years developments in various fields of applied 
photography have necessitated the use of shorter and shorter expo- 
sure times at high illumination levels. A study of the data available 
on the reciprocity failure shows that as illumination levels are in- 
creased, reciprocity failure again becomes of considerable magnitude. 
It is becoming more and more evident that the failure of the reci- 
procity law is of importance in some kinds of work, and the primary 
purpose of this paper is to show how the available data can be in- 
terpreted and applied in the case of practical photographic expo- 
sures. As stated previously, the chief interest in the practical as- 
pects of reciprocity law failure has been manifested in astronomical 
work where exposures must be made at very low illumination levels. 
However, under the conditions of high intensity which are now being 
used on certain types of motion picture photography, especially in 
the photographic recording of sound, the reciprocity law failure is 
coming to be recognized as an important factor at high as well as at 
low intensity. 

The reciprocity law failure is an inherent and fundamental char- 
acteristic of all photographic emulsions, although the magnitude of 
the departure from the reciprocity relationship may vary consider- 
ably with different emulsion types. It is, of course, quite evident 
that the reciprocity characteristic of an emulsion must be known in 
order to predict precisely the performance of that emulsion when 
exposed at any particular illumination level. 

HISTORICAL RfiSUMfe 

The fact that the magnitude of the chemical effect produced on a 
light-sensitive substance is not determined solely by the total quantity 
of energy absorbed, but is dependent also upon the rate at which the 
energy is absorbed, seems to have been known almost from the be- 
ginning of photography. 1 Since the first photographic materials 



144 L. A. JONES AND J. H. WEBB [j. s. M. P. E. 

made were extremely slow and this failure to integrate correctly the 
incident radiant energy over an exposure period of finite duration is 
accentuated with slow emulsions, it is natural that the effect should 
have been found and then more or less neglected as the speeding up 
of the emulsions made it less and less troublesome to the average 
photographer. 

In 1876 Bunsen and Roscoe 2 formulated a general law for photo- 
chemical reactions, without specific reference to photography. Their 
statement was: 

Insolation <x Exposure 
Exposure = Intensity X Time 

The term insolation was used by them in referring to the effect, 
the photochemical reaction, produced by the action of radiant energy 
on the photosensitive material. Exposure is defined specifically as 
the product of intensity by time, both factors of which are precisely 
measurable by appropriate physical methods. Exposure must 
therefore be regarded as of a purely causative nature of which the 
effect is referred to as insolation. From the reciprocal relation be- 
tween time and intensity given by the Bunsen-Roscoe formula, it was 
called the reciprocity law, and the deviations from it have been known 
universally as "failure of the reciprocity law." 

In 1892 Abney 3 worked on the problem using two different light 
sources, a candle and an electric spark. He found that when he de- 
creased the illumination on the photographic plate, by increasing 
the distance between the candle and the photographic plate, the 
photographic effect (insolation) decreased faster than it should if the 
Bunsen-Roscoe equation were valid. On the other hand, with con- 
stant values of exposure (I-t) when using the electric spark, an in- 
crease in the energy intensity incident on the plate was followed by 
a decrease in the photographic effect (insolation) . These data pointed 
toward the existence of an intensity which would give a maximum 
photographic effect for a constant value of exposure. 

In 1900 Schwarzschild 4 formulated an empirical expression for use 
in this work. This expression, 

Insolation = / X V 

where p is a constant and usually has been given a value of about 
0.8, was used by him for determination of stellar magnitudes and in 
other work where the intensities under consideration were extremely 
low. The simplicity of the expression and its ease of application, as 






Sept., 1934] RECIPROCITY LAW FAILURE 145 

well as the lack of any other, led to its extension to practically all 
fields of photography. More recent work on the subject has shown 
that Schwarzschild's relationship is entirely inadequate to fit the 
facts over a very wide range of intensities. Even by making the 
exponent p of variable value the observed effects are not well repre- 
sented by an equation of the Schwarzschild type. The use of the 
Schwarzschild relationship has been so wide-spread that we fre- 
quently find references in the literature to it as the Schwarzschild 
law, and many workers still continue to assume that the relationship 
is adequate to represent mathematically the failure of the reciprocity 
relationship. It is unfortunate that this misleading expression has 
received such wide application since its failure to fit the experimental 
facts may introduce serious errors. 

From 1903 to 1906 the work of Mees and Sheppard 5 indicated the 
existence of an intensity at which the photographic effect was a maxi- 
mum. 

The classical work of Kron, 6 in the Potsdam Astrophysical Labo- 
ratory, was done in 1913. This is one of the most complete single 
treatises on the subject. In his exhaustive study of four different 
emulsions, Kron concluded that the experimental data were best 
presented in the form of "curves of constant density;" that is, he 
plotted the logarithm of exposure (I -I), required to produce a constant 
density, against the logarithm of intensity (illumination). For all 
the emulsions studied by him he found an optimal intensity, or an 
intensity at which a minimum amount of exposure was required to 
give a fixed density. Kron found that an analytical expression of a 
hyperbolic form fitted his experimentally observed facts quite well. 
He also suggested an equation of the catenary form but did not find 
that it represented the facts quite as well as the hyperbolic form. 
He noted that optimal intensity was at a lower value for fast emul- 
sions than for slow emulsions and that the optimal intensity in- 
creased with increasing development. Kron's results have been 
applied extensively by Halm. 7 

Although there are many others who have investigated portions 
of the intensity range and who have developed special formulas ap- 
plicable to special problems, the works mentioned seem to be the best 
known and the most general studies of the behavior of commercial 
emulsions up to the year 1921, when the problem was taken up by 
the Kodak Research Laboratories. More complete bibliographies 
will be found in Kron's paper and one by E. A. Baker. 8 



146 



L. A. JONES AND J. H. WEBB 



[j. a M. p. E. 



During the years 1923 to 1927 a group of five papers was published 
by Jones and his collaborators 9 bearing on various phases of the reci- 
procity failure. Their experimental results were most perfectly 
fitted by an equation of the catenary form. 

In 1927 Arens and Eggert 11 published a paper on the reciprocity 
law failure in which a graphical method was presented for showing 
the effect of reciprocity law failure upon the shapes of the intensity- 
and time-scale H&D curves. The method consists in drawing con- 
stant-density curves in the (log /, log /) plane and then constructing 
from these curves the intensity- and time-scale H&D curves in the 
directions of the two coordinate axes of this plane. This method of 
applying the reciprocity data to the exposure curves obtained in 
practice was a step forward. The method given here for applying 
the reciprocity data, while being somewhat similar to that of Arens 
and Eggert, has the added advantage of being more direct and 
simpler to use. 

This brief discussion of the literature of the subject, while not 
particularly complete, will serve to give the reader references in case 
he wishes to delve into the more theoretical aspects of the subject. 

GENERAL DISCUSSION OF THE RECIPROCITY LAW FAILURE 

The practical effect of the reciprocity law failure may be clearly 
illustrated by a simple example. If the aperture of a camera lens 
is changed from //3. 5 to//7.0 (all other factors remaining constant), 
the illumination on the photographic material in the focal plane, 
where the image is formed by the lens, is correspondingly changed to 
one-fourth of its original value. If the reciprocity law were valid, it 
would be necessary to increase the time of exposure to four times the 
value used at//3.5 in order to obtain the same density in the devel- 
oped images. Because of the reciprocity law failure, however, a 
little more or a little less than this exposure time may be required 
in order to maintain equality of density in the developed images. 

In previous work, two methods have been followed generally in 
studying reciprocity law failure. One of them consists in giving to 
an emulsion a series of constant-energy (iXt) exposures in which 
the factors / and / are reciprocally varied as, e. g. (It = 16 X 1, 8X2, 
4X4, 2X8, etc.), and studying the variations in the densities at dif- 
ferent intensities. The other method consists in measuring the 
amounts of exposure (IXt) required to produce a constant density 
at different levels of intensity. The latter of these methods, being 



Sept., 1934] 



RECIPROCITY LAW FAILURE 



147 



somewhat more amenable to analytical treatment, will be used here, 
and the data will be presented by plotting constant-density curves, 
the ordinates of which represent the log It values and the abscissas 
represent log / values. Such curves will be called reciprocity failure 
curves and each will be labeled by the density value for which it was 
constructed. The general shape of such curves, characteristic of all 
emulsions, is illustrated by curve A of Fig. 1. Since ordinates of the 
reciprocity curve represent the log exposure values required to pro- 
duce a constant density, it is obvious that curve A would become the 
horizontal line B if the reciprocity law held rigorously. It is readily 
seen in the case of the actual curve A that there is one intensity level, 
/i, at which a minimal amount of exposure is required. This in- 



<3 o 
o 

J 



T.o - 




3.0 56 20 



FIG. 1. Illustration of the reciprocity failure character- 
istic. 



tensity is known as optimal intensity, and its value changes from one 
emulsion to another. In departing from this optimal intensity and 
going either to higher or to lower intensities, more exposure is re- 
quired to produce the same density. Thus there is one most effi- 
cient intensity for use with a photographic emulsion. The amount 
of the excess exposure required to produce a given density at inten- 
sity /, as compared with the amount required to produce the same 
density at optimal intensity, is usually termed the magnitude of the 
reciprocity law failure. Thus, for example, at the value of 100 units, 
corresponding to log / = 2.0 (see Fig. 1) this excess exposure value 
is represented by the vertical intercept ab. In log units, this amounts 
to 0.5, which corresponds to a numerical factor of 3.16. In other 
words, 3.16 times the exposure is required to produce a given density 
at intensity 100 units as at the intensity of 1 unit. 



148 L. A. JONES AND J. H. WEBB [j. s. M. P. E. 

The reciprocity curve A may vary considerably in shape for differ- 
ent emulsions, some materials possessing very flat curves and others 
very steep curves. Frequently, the reciprocity curves are symmet- 
rical for a considerable interval on either side of optimal intensity, 
usually breaking away from this symmetrical shape, however, and 
turning sharply upward at very low intensities. 

Few general rules have been found which make it possible to cor- 
relate the shape of the reciprocity failure curves with other char- 
acteristic attributes of the emulsion, such as speed, grain size, sen- 
sitization, etc. Some fast materials have a very large failure while 
others have a very small failure, and the same applies to slow emul- 
sions. The effect of development upon reciprocity law failure is 
generally slight. Different developers have been found 9 to shift the 
optimal intensity somewhat, and variation in the extent of develop- 
ment alters the curvature of the curves to a small degree. However, 
for the general considerations of reciprocity law failure to be dealt 
with here, these complications need not be brought in. Also, quality 
of radiation need not be considered here since it has been shown 10 
that the reciprocity characteristic is independent of the quality of 
radiation when points of the same density and exposure time are com- 
pared. 

INTERPRETATION OF RECIPROCITY LAW FAILURE AND ITS APPLICATION TO 
PRACTICAL PHOTOGRAPHIC EXPOSURES 

Speed and contrast of an emulsion are the two factors chiefly af- 
fected by reciprocity law failure, and these are usually the charac- 
teristics of chief importance to the user of photographic emulsions 
for either pictorial or scientific work. By means of reciprocity fail- 
ure curves drawn for a series of densities, it is possible to obtain the 
values of these factors for both intensity- and time-scale H&D curves 
over the range of intensity covered by the reciprocity curves. Fur- 
ther, the variations in these factors with intensity are also available 
and usually a casual inspection of the reciprocity failure curves is 
sufficient to show the general trend of the variations in these factors. 
It will be shown in this section how this information can be read from 
the reciprocity failure curves and how it can then be applied to prac- 
tical photographic exposure. 

For illustrative purposes, the curves of Fig. 2 are presented as 
typical of those from any ordinary photographic emulsion. These 
curves were obtained from an actual emulsion, and were chosen be- 






jpt, 1934] 



RECIPROCITY LAW FAILURE 



149 



mse of a combination of qualities which made them particularly 
suitable for demonstration purposes. These curves are given for 
density values 0.5, 1.0, 1.5, and 2.0, and they cover a range of inten- 
sity values from one to one million. 

In order to read the reciprocity diagram, it is first essential to lo- 
cate and establish on this diagram the lines of constant intensity and 
the lines of constant time. The constant-intensity lines on this dia- 
gram correspond to the time-scale H&D curves, while the constant- 
time lines correspond to the intensity-scale H&D curves. Conse- 
quently, in order to read the speed and contrast values for these two 
types of H&D curves it is necessary to know the course of these curves 
on the reciprocity diagram. It is obvious that any vertical line on 




FIG. 2. Typical reciprocity curves, 7= AD/ A (log It). 

the reciprocity diagram is a constant-intensity line, the abscissa 
values being the same for every point on such a line. Constant-in- 
tensity lines are illustrated in Fig. 2 by the dotted vertical lines. 
Thus, as one proceeds upward along one of these dotted lines, the 
density and the log It values encountered are precisely those which 
would be encountered by proceeding upward along a time-scale H&D 
curve. Indeed, as will be shown later, the time-scale H&D curve 
can be constructed by plotting the values of density vs. log It ob- 
tained from the intersection points of a vertical line with the various 
reciprocity curves. Also, the gamma, or contrast, value can be ob- 
tained for this H&D curve directly from Fig. 2 by dividing the den- 
sity difference between two curves by the vertical intercept in log 



150 L. A. JONES AND J. H. WEBB [J. S. M. P. E. 

It units between the two curves. For example, on the 0.312 m.c. 
constant-intensity line between the reciprocity curves of densities 
1.5 and 1.0, the difference in density is 0.5 and the log // intercept is 
0.38. Therefore, the gamma, or slope, of the H&D curve is 1.31, 
the ratio of these quantities. It is necessary, of course, in comput- 
ing the value of gamma in this manner, that the density values 
chosen (in this case 1.5 and 1.0) both lie on the straight-line portion 
of the characteristic curve. In case they do not, the value obtained 
will be the average slope of the H&D curve between the particular 
density values used. 

The lines of constant time in Fig. 2 are those shown by the 45- 
degree lines. That these lines are constant-time lines can be verified 
by the following argument. Ordinates on the reciprocity diagram 
represent log //, while the abscissas represent log I values. By formal 
analogy with the equation, 

y = x + constant 

which is the equation of a straight line of unit (or 45 degrees if the 
x and y scales are equal) slope in terms of Cartesian coordinates, it is 
readily seen that the equation, 

; log It = log / + log t 

represents a straight line of 45-degree slope on the reciprocity dia- 
gram provided log t is a constant. The value of this constant for 
any 45-degree line is readily determined by choosing a point on that 
line and subtracting its abscissa value, log /, from its ordinate value, 
log //, thus, 

log It log / = log t 

This may be verified by noting that the difference between the or- 
dinate and abscissa value for every point along the one-second line 
is zero, corresponding to the antilog of unity. 

The 45-degree lines drawn in Fig. 2, representing constant-time 
lines at intervals of 10, correspond to the intensity-scale H&D 
curves. Here again, proceeding upward along one of these 45- 
degree lines, the values of density and log It values encountered 
correspond to those along an intensity-scale H&D curve. The con- 
trast value at any point along one of these intensity-scale curves can 
be obtained in the same manner as in the case of a time-scale curve. 
As before, the density difference between two reciprocity failure 
curves is divided by the difference in log It as read from the ordinates 






Sept., 1934] 



RECIPROCITY LAW FAILURE 



151 



of the intersection points of the constant-time line with the reciprocity 
curves. For example, choosing the 100-second, constant-time line, 
the difference in density between the curves for densities 1.5 and 1.0 
is 0.5. The corresponding difference in log It values read from the 
intersection points is 0.31. The ratio of these values gives a gamma, 
or contrast, value of 1.61 for this H&D curve. 

In order to illustrate how it is possible to study from the reciprocity 
diagram the shapes of time-scale and intensity-scale H&D curves, 
as well as their alterations in shape with intensity, several curves of 
each type have been derived from the reciprocity failure curves 
of Fig. 2, and are shown in Fig. 3. Curves of both types have been 
constructed for three widely separated regions of intensity, as follows : 



BELOW OPTIMAL 

28J- C*) TIME: SCALE: i- ooiz MC 
(b) INT SCALE: T 1000 SEC 



GAMMA 
(<x) I 20 
(b) 160 




OPTIMAL 

(a) TIME SCALE I=3IZM 

(b) INT SCALE: T=IO SEC 

GAMMA SPEED 

(a) | 25 T90 

(b) I T>*> 620 




ABOVE OPTIMAL 
(a) TIME SCALE I = 8O M.C 
Cb) INT SCALE T Ol SEC 



GAMMA SPEED 
fa) I Z'b IOO 

(b) *' OO 4OO 




29 



FIG. 3. 



T.6 



Comparison of intensity- and time-scale H&D curves at different 
levels of intensity. 



one well below optimal intensity, one near optimal intensity, and one 
well above optimal intensity. A comparison of the intensity-scale 
curves with the time-scale curves in Fig. 3 will show clearly the dif- 
ferences in speed and gamma obtained with these two types of curves 
and how these quantities change with intensity. The H&D curves 
here presented were obtained by following the constant-intensity 
and constant-time lines on the reciprocity diagram as previously de- 
scribed. The intensity-scale curves were derived from the 1000- 
second, the 1-second, and the 0.01-second lines, respectively. The 
time-scale curves were derived from the 0.0012-m.c., the 0.312-m.c., 
and the 80-m.c. intensity lines, respectively. 
An inspection of these curves will show that in the case of the two 



152 L. A. JONES AND J. H. WEBB [j. s. M. P. E. 

H&D curves below optimal intensity, the intensity-scale, curve is the 
steeper. The gamma values for the two curves are in the ratio 1.60 
to 1.20. In the region of optimal intensity, the gamma values of 
the intensity- and time-scale curves are practically equal, being 1.35 
and 1.25 for the intensity-scale and time-scale curves, respectively. 
In the region above optimal intensity, the gamma values are re- 
versed from what they were below optimal intensity, the time-scale 
curve being here the steeper, as shown by the numerical gamma values 
1.25 and 1.00. It is to be noted that the slope, or gamma, of the time- 
scale curve remains practically unchanged with varying intensity, 
while gamma for the intensity-scale curve changes from 1.60 to 1.00 
over the range of intensity covered by this diagram. 




FIG. 4. Super- Sensitive Motion Picture Panchromatic film; reciprocity 

law failure. 

The behavior of the gamma value for each of the types of H&D 
curves may be seen to be attributable to the shape of the reciprocity 
curves and to the manner in which these curves are crossed by the 
constant-intensity and constant-time lines. At low intensities the 
contant-time lines meet the reciprocity curves more nearly perpen- 
dicularly, and hence the vertical log // intercept encountered in pass- 
ing from one density curve to the next is less than in the region of 
intensity above optimal, where the constant-time lines make a very 
small angle with the reciprocity curves. In the neighborhood of 
optimal intensity, the reciprocity curves are nearly flat, and as a 
consequence, there is little difference between the vertical intercepts 






Sept., 1934] 



RECIPROCITY LAW FAILURE 



153 



on the constant-intensity lines and the constant-time lines. This 
accounts for the practical equality of the gamma values for the in- 
tensity- and time-scale H&D curves in this region. The constancy 
of gamma with intensity for the time-scale H&D curves may also be 
understood from an inspection of the reciprocity curves of Fig. 2. 
Since the reciprocity curves for different densities are nearly parallel 
vertically, the vertical intercept between curves, and thereby the 
gamma value, remains substantially unchanged with changing in- 
tensity. 

The intensity-scale H&D curve is the one which conforms to the 
type of exposure obtained in practical pictorial photography. In 




LOG I (M C.) 



FIG. 5. Eastman 40 plate; reciprocity law failure. 

exposures of this type, the entire area of the exposed emulsion is 
given the same exposure time, the density range being obtained 
through variations in intensity from point to point in the focused 
image. On the other hand, the time-scale H&D curve is the one more 
frequently employed in the sensitometric testing of emulsions be- 
cause of the greater simplicity and accuracy obtainable in time-scale 
instruments. From what has gone before, it is clear that, if control 
test exposures made with time-scale instruments are to yield infor- 
mation of practical value in making exposures, it is necessary to know 
the reciprocity failure characteristics of the emulsion so that the test 
exposures can be correctly interpreted for the practical conditions of 
use. 



154 



L. A. JONES AND J. H. WEBB 



[J. S. M. P. E. 



Further information of practical importance contained in the 
reciprocity failure curves is in regard to the matter of emulsion speed 
at different levels of intensity. In Fig. 3, the values of the H&D 
speed calculated from the relation 10/i are given for the various H&D 
curves presented. The speeds as obtained from both types of curves 
are seen to vary considerably with the intensity level. Moreover, 
the variations in speed are different for the two types of curves. 
This difference in speed variation is due to the difference in the be- 
havior of gamma for the two types of curves, as can be understood 
from the fact that the above manner of determining speed is depen- 
dent upon inertia, and therefore gamma. 

For the technician working in the laboratory in the design or opera- 



uT.i 
I 




21 29 

LOG I CM 



FIG. 6. Eastman 50 plate; reciprocity law failure. 

tion of apparatus for high-intensity exposures, as, e. g., sound record- 
ing apparatus and certain types of printers, it is essential for best 
results to have available information regarding the relative behavior 
of intensity- and time-scale curves at high intensity. The need for 
such information is at once apparent from a comparison of the two 
H&D curves at high intensity shown in Fig. 3. The intensity-scale 
curve has a much lower contrast here than the time-scale curve, 
whereas the opposite was true at low intensities. As for the time- 
scale curve, there is no evidence that there is any loss of contrast at 
the high intensities even though the loss in speed is considerable in 
this region. 

The behavior of the two types of H&D curves of Fig. 3 with chang- 



Sept., 1934] 



RECIPROCITY LAW FAILURE 



155 



ing intensity is typical, qualitatively, for all emulsions. Of course, 
the magnitude of the changes in gamma and speed with intensity, 
and the position of optimal intensity, will change from one emulsion 
to another. In general, then, the behavior of speed and gamma of 
any emulsion can be summed up as follows: The optimal intensity 
of an emulsion occurs in the region for which the exposure time 
necessary to produce a medium density is of the order 0.1 to 10 
seconds. The speed of an emulsion decreases as the exposing inten- 
sity is either increased above, or decreased below its optimal value. 
The gamma value of an intensity-scale H&D curve increases for in- 
tensities below optimal intensity and decreases for intensities above 
optimal intensity. The gamma of the time-scale curve is not greatly 




FIG. 7. Eastman Super-Speed film; reciprocity law failure. 

affected by changes of intensity and usually agrees in value very 
closely with the gamma of the intensity-scale curve in the neighbor- 
hood of optimal intensity. 

THE RECIPROCITY FAILURE CHARACTERISTICS FOR SEVERAL TYPES OF COM- 
MERCIAL EMULSIONS 

Curves of the reciprocity failure characteristic for a number of 
commercial emulsions in common use are exhibited in Figs. 4 to 9. 
The curves of Fig. 4 are for the Super-Sensitive Panchromatic motion 
picture film. As this film is used largely for motion picture and still 
camera photography, the exposures usually are of a duration be- 
tween 0.1 and 0.001 second. It may be seen that this range of ex- 



156 



L. A. JONES AND J. H. WEBB 



[J. S. M. P. E. 



posure time falls in the region of intensities slightly above optimal 
intensity. In this region the time-scale H&D curve would be slightly 
more contrasty than the intensity-scale curve. However, as the reci- 
procity failure curves are not steep in this region neither the change 
in speed nor the variation in contrast over this range is serious. 

The curves of Figs. 5, 6, and 7 are for a group of high-speed ma- 
terials used to a large extent in both pictorial and scientific work. 
The Eastman 40 plate is a high-speed, blue-sensitive emulsion used 
in portraiture work and to a considerable extent in spectroscopy and 
astronomy. It is to be noted that this emulsion has a very flat reci- 
procity characteristic so that it holds its speed well, and changes its 
contrast only slightly, over wide ranges of intensity. The fact that 



r 



EXPOSURE TIME (SEC ) 
IOO IO 




FIG. 8. Motion Picture Positive film; reciprocity law failure. 

this emulsion holds its speed so well at low intensities makes it par- 
ticularly suitable for astronomical exposures. The Eastman 50 
plate is an extremely high-speed orthochromatic plate used in high- 
speed portraiture and to some extent by press photographers. Its 
reciprocity characteristic is rather flat and its optimal intensity is in 
the region for which the exposure time is 0.1 second. This higher- 
than-average value of optimal intensity renders the speed of this 
emulsion near a maximum in the region of exposure times for which 
it is mostly used. The low reciprocity failure for this emulsion at 
low intensities recommends it also for astronomical work. The Su- 
per-Speed portrait film is also a high-speed orthochromatic emulsion 
and its reciprocity failure is seen to be somewhat greater than that 



Sept., 1934] 



RECIPROCITY LAW FAILURE 



157 



for Eastman 40 or Eastman 50 plates. This film being intended es- 
pecially for portrait work, its speed is seen to be near maximum in 
the region of exposure times for which it is mostly used. This fact 
is brought out by the reciprocity failure curves. 

The reciprocity characteristics for two low-speed emulsions are 
shown in Figs. 8 and 9. The Motion Picture Positive film, used in 
the printing of motion pictures for which the exposures are of a dura- 
tion between 0.1 and 0.01 second, is seen to have a relatively high 
speed in this region of exposure times. The closeness of the reciproc- 
ity curves for this emulsion emphasizes its high contrast. The 
curves for Eastman Process plates are shown in Fig. 9. These 



EXPOSURE. TIME fSCC") 
I0 3 IOO 




29 75 

LOG 1 (M O 



FIG. 9. Eastman Process plate; reciprocity law failure. 

plates are used chiefly in copying work, particularly for such as line 
drawings, in which strong contrast is needed. Because of the low 
speed of this emulsion, the exposures are usually of considerable 
duration, being of the order of from 1 to 10 seconds. Neither the 
speed of this emulsion nor its contrast is materially affected by 
reciprocity law failure in this region of exposure times. As in the 
case of the Motion Picture Positive, the extreme contrast of this 
emulsion is manifested by the closeness of the reciprocity curves to 
one another. 

In order to compare the foregoing emulsions with regard to ex- 
posures for optimal speed, a list of optimal exposure times is given 
in the following table. These optimal values of exposure time repre- 



158 L. A. JONES AND J. H. WEBB [j. s. M. p. E. 

sent, for a density value of 1.0, the exposure time for which the speed 
of the film is a maximum. 

Table of Optimal Exposure Times 
Density = 1.0 

Emulsion t upt 

Super-Sensitive Motion Picture Pan 1 . sec 

Eastman 40 1.0 " 

Eastman 50 0.2 " 

Eastman Super-Speed 5.0 " 

Motion Picture Positive 0.1 " 

Eastman Process 0.1 " 

REFERENCES 

1 FIZEAU, A. A. L., AND FOUCAULT, J. B. L.: Comptes Rendus, 18 (1844), p. 746. 

2 BUNSEN, R., AND ROSCOE, H. E. : Pogg. Ann., 108 (1876), p. 193. 

I ABNEY, W. DEW. : Phot. /., 18 (1893-1894), pp. 254-260 and 302-310. 
4 SCHWARZSCHILD, K. : Astrophys. J., 11 (1900), p. 89. 

6 MEES, C. E. K., AND SHEPPARD, S. E. : Phot. J., 43 (1903), p. 48. 
8 KRON, E.: Pub. Astrophys. Obs. Potsdam, N. 67 (1913). 

7 HALM, J. R.: Astronomical Soc. Monthly Notices (June, 1922), p. 473. 

8 BAKER, E. A. : Proc. Roy. Soc., Edinburgh, 45, Part 2 (1924-5), p. 166. 

9 JONES, L. A., AND HCJSE, E.: J. Opt. Soc. Amer. & Rev. Sci. Instr., 7 (1923), 
p. 1070; 11 (1925), p. 319. 

JONES, L. A., H JSE, E., AND HALL, V. C.: /. Opt. Soc. Amer. & Rev. Sci. Instr., 
12 (1926), p. 321. 

JONES, L. A., AND HALL, V. C.: J. Opt. Soc. Amer. & Rev. Sci. Instr., 13 (1926), 
p. 443. 

JONES, L. A., HALL, V. C., AND BRIGGS, R. M.: /. Opt. Soc. Amer. Of Rev. 
Sci. Instr., 14 (1927), p. 223. 

10 WEBB, J. H. : /. Opt. Soc. Amer., 23 (1933), p. 316. 

II ARENS, H., AND EGGERT, J.: Zeit. fur Physikalische Chemie, 131 (1927-28), 
p. 297. 

DISCUSSION 

MR. MITCHELL: Does the fact that the curves slope upward indicate an 
advantageous effect in the case of underexposure? 

MR. JONES: The answer to that question depends upon what is meant by 
underexposure. Referring to Fig. 4, it will be seen that the optimal intensity for 
Super-Sensitive Motion Picture Panchromatic film occurs when log / is equal to 
2.0. If the intensity is either less or greater than that value, then the photo- 
graphic effect for constant exposure is less. It should be remembered, however, 
that the range of intensity values shown in Fig. 4 is very great, approximately 1 to 
1,000,000. In the case of this material, a loss of effective speed, due to failure of 
the reciprocity law, is encountered only when the intensities are so low that the 
exposure times must be very great; for instance, as in astronomical work, where 



Sept., 1934] RECIPROCITY LAW FAILURE 159 

the exposure times may be several hours long. On the other hand, this material 
may be effectively slower where the intensities are so great that the exposure times 
are extremely short; for instance, 0.0001 second. In the case of the material 
illustrated in Fig. 7, the reciprocity failure at low intensities is relatively great. 
The reduction of the intensity level to Vioo of the optimal intensity necessitates 
increasing the exposure time by a factor of 3.5 in order to attain the same photo- 
graphic effect as attained for optimal intensity. 

MR. KELLOGG: If I understand correctly the difference in the time-exposure 
product required to obtain a given film density, between the time of exposure 
for average camera work and the duration of exposure in recording sound on 
positive film, is quite small; perhaps less than 2 to 1. 

MR. JONES: Yes. 

MR. KELLOGG: That is of interest to us who are engaged in sound recording. 
Mr. Blaney, of the RCA Victor Company, has some unpublished figures that 
indicate distinctly lower gammas with very high-intensity, brief -exposure condi- 
tions. Does that check with your curves? Also, does the color of the light have 
very much to do with it? 

MR. JONES : The reciprocity law failure is almost independent of the quality of 
radiation. With regard to the variation of gamma with the intensity or time of 
exposure, the values shown in Fig. 3 indicate the relationship. For instance, 
in the case of density-log E curves, plotted from time-scale sensitometric strips, 
the values of gamma obtained for wide variations of intensity are relatively small, 
being 1.20 for / = 0.0012 meter-candle, 1.25 for / = 0.312, and 1.25 for / = 80. 
On the other hand, if an intensity scale is used, a very marked variation of gamma 
is obtained for different times of exposure. For instance, with exposure time of 
1000 seconds, gamma is 1.60; for an exposure time of 1 second, gamma becomes 
1.35; and for an exposure time of 0.01 second, gamma drops to 1.00. The an- 
swer to your question, therefore, is a bit complicated since we must specify 
whether gamma is evaluated in terms of a time scale or an intensity scale. 

MR. KELLOGG: Your answer suggests the interesting conclusion that those 
working with a light-valve of the Western Electric type, which changes the time of 
exposure, can use the gammas determined by ordinary densitometric measure- 
ments with much longer periods of time and lower intensities; whereas those 
working with a light-valve of the Kerr cell type, which causes changes of intensity, 
for example, would have to use a different gamma. 

MR. JONES: Yes, that is right. 



A MOTION PICTURE NEGATIVE OF WIDER USEFULNESS* 

P. ARNOLD** 

Summary. Super pan negative film represents a refinement in film manufacture 
rather than an invention of startling novelty. The anti-abrasion surface coating 
protects the emulsion from physical harm, and the anti-halation, gray back-coating, 
underlying the emulsion, preserves the definition and photographic quality. Pos- 
sessed of adequately high speed, the emulsion produces superior fine-grain results not 
common to super-sensitive films. A long gradation scale enhances the fidelity of 
tonal rendition, and an especially wide latitude in both exposure and development in- 
creases the range of pictorial possibilities. A high sensitivity to color, carefully 
balanced throughout the visible spectrum, permits normal rendering or the attainment 
of desired color emphasis by the use of filters without demanding serious speed sacri- 
fices. 

The progress and achievements of the motion picture industry 
have been conditioned and governed to a considerable extent by the 
picture-taking abilities or possibilities of the negative films that have 
been provided from time to time by photographic film manufacturers. 
The tremendous improvements made in negative film materials 
during the past several years have practically revolutionized the 
photographic branch of the industry. It may well be expected that, 
for the present, no radically different types of negative films are 
in prospect, but that the progress during the next few years will 
take the form of perfecting and improving the existing types. 

The Agfa Ansco Corporation has recently produced a new and im- 
proved negative material offering a wider range of usefulness for 
35-mm. motion picture work. Several unique improvements have been 
incorporated in the new material, which has been named Agfa Super- 
pan Negative. Its characteristics will be briefly considered, first ac- 
cording to its physical properties, and then according to the emulsion 
properties of speed, gradation, grain size, and color-sensitivity. 

PHYSICAL PROPERTIES OF SUPERPAN NEGATIVE 

The photographic characteristics of Superpan negative are related 
not only to the chemical properties and behavior of the light-sensitive 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Agfa Ansco Corp., Binghamton, N. Y. 
160 






NEGATIVE OF WIDER USEFULNESS 161 



coating, but also to the physical and mechanical structure of the 
material. Superpan is complicated in manufacture in order that it 
may be more simple in use. The base is a clear, almost colorless, 
nitrocellulose film support specially treated and prepared to prevent 
the generation and consequent discharge of static electricity. The 
gray back is an undercoating, not located on the back of the film or 
diffused through the basic stock, but underlying the emulsion itself. 
The emulsion is not only double-coated, but triple-coated, and the 
third coating is of particular merit. (See Fig. 1.) 

The Gray -Back Coating. The gray-back coating is imposed be- 
tween the first emulsion layer and the cellulose film support at the 
place where halation principally arises.* This location of the neutral 
gray layer, with respect to the emulsion coating, effectively prevents 




FIG. 1. Magnified cross-section of Superpan: (a) anti-abrasion coating; 
(6) first emulsion coating; (c) second emulsion coating; (d) gray-back coat- 
ing; (e) base. 

halation by inhibiting the reflection of light back into the emulsion 
from either surface of the film base. The color of the gray backing 
lightens somewhat during developing, but the layer itself has no 
chemical effect upon the developing solution or fixing bath, and in 
turn is not impaired by any unusual condition arising during proc- 
essing that would not also injure an emulsion coating. 

* The location of the dark colored anti-halation layer beneath the emulsion 
rather than on the back of the film is a principle of film manufacture that has been 
successfully applied by Agfa Ansco for several years to 16-mm. reversible film. 
In the latter case, however, the chemical properties of the anti-halation layer are 
much different in order to permit the complete removal or decolorization of the 
backing during the reversal process. A gray tint obviously would be objection- 
able in a film intended finally to serve for projection, because it would greatly 
reduce the screen illumination and lend an undesirable tone to the projected pic- 
tures. 



162 P. ARNOLD [j. s. M. p. E. 

The Three Emulsion Coatings. Superpan negative has two distinct 
sensitized emulsion coatings differing widely in photographic proper- 
ties but adjusted to blend their individual characteristics harmoni- 
ously into a single photographic result. The third coating (placed 
over the second emulsion coating, which is also the more sensitive 
one) consists of an extremely thin layer of clear gelatin. This non- 
sensitive top coating has very specific properties rigidly controlled in 
the coating process, but it has no chemical or optical effect upon the 
emulsion. Its function is to protect the delicate emulsion layer 
from abrasion caused by contact with other surfaces encountered 
in normal handling of the film prior to development. 

EMULSION PROPERTIES OF SUPERPAN NEGATIVE 

The General Sensitivity. The speed of motion picture negative ma- 
terials is a matter that has engrossed our attention for the past several 
years. Today negative films of "super-sensitive" speed have be- 
come familiar almost to the complete exclusion of other types, whereas 
only a few years ago such materials seemed to lie beyond the realm 
of possibility. Superpan negative belongs to this class of modern 
high-speed films. It demands no sacrifice in lens opening and no 
excessive illumination to compensate for a deficiency in sensitiveness. 

However, in producing the Superpan negative film, the aim of the 
manufacturer was not to attain the highest possible speed as a 
primary requisite to be accompanied by acceptable pictorial charac- 
teristics; but, rather, to combine the finest possible pictorial charac- 
teristics of gradation, grain size, and color-sensitivity in a negative 
film of acceptably high speed. That speed, of necessity, was specified 
to lie within the range of the super-sensitive film emulsions. 

Gradation Characteristics. The subject of gradation is of utmost 
importance in making a negative film emulsion because of the great 
effect that gradation characteristics exert upon the ability of an 
emulsion to perform the sort of work for which it is intended. Grada- 
tion is also important from the manufacturer's point of view, because 
of the technical difficulties that must be surmounted in order to pro- 
duce a negative film that will adequately fulfill the requirements of 
not only one photographic condition, but of a wide range of variable 
photographic conditions, and to produce satisfactory results through- 
out that range. 

The gradation of a photographic emulsion may be defined as its 
density response to varying light intensity. By means of the familiar 



Sept., 1934] 



NEGATIVE OF WIDER USEFULNESS 



163 



photometric curve, the gradation characteristics of Superpan nega- 
tive may be viewed in its various relationships (Figs. 2 and 3) . Of 
particular note is the especially long scale of gradation shown by the 



AGFA 
BORAX DEVELOPER 




Loe RELATIVE EXPOSURE * 

FIG. 2. Characteristic curve of Superpan: Agfa borax de- 
veloper. 

extended straight-line portion of the curve. Naturally, a material 
with such a gradation range is adaptable to a great variety of lighting 
conditions and to a wide range of light intensity. The long scale 




D-76 
BORAX DEVELOPER 



Loe RELATIVE EXPOSURE' 
FIG. 3. Characteristic curve of Superpan: D-76 developer. 

provides the means for faithful tonal reproduction throughout ex- 
tremes of illumination. 
A second advantage is the increase in exposure latitude afforded 



164 



P. ARNOLD 



[J. S. M. P. E. 



by the long scale; but this possibility may not be, to the skilled 
cameraman, of so much practical importance as the improvement in 
rendering fine details and the modulation in the highlights of a sub- 
ject afforded by the extended upper range of the linear portion of the 
curve, where the highlights are recorded. Extension of the straight- 
line portion of the curve facilitates the faithful registration of densities 
over a wider range of subjects and light intensities than would be 
possible without tonal distortion with a film of shorter scale. 

Development Characteristics. The development requirements of 
Superpan negative film are not exclusive or restricted, for any good 
developing formula may be used, with the type of results common to 
that developer. The negative responds to the developer more or 



5 10 15 20 29 30 

DEVELOPING TIME IN MINUTES 

FIG. 4. Relation of gamma of Superpan to developing 
time: Agfa borax developer. 

less in the manner typical of highly sensitive, silver halide emulsions. 
However, the time-gamma curve and the threshold response to de- 
veloping time offer interesting possibilities (Fig. 4) . 

The threshold of sensitivity, or the toe of the photometric curve, 
advances with the developing time, thus increasing the effective 
speed of the emulsion by over-development. The increase of gamnu 
with the time of development may be plotted as a smooth curve. 
Any gamma from 0.5 to 1.4 may be attained, a range that is particu- 
larly valuable when the film is used for background shots. In such 
work the subject is customarily lighted more brilliantly to compensate 
for the loss of definition through diffusion. 

Fine-Grain Properties. The matter of grain size has become in- 
creasingly important in motion picture technic. Applied to a photo- 






Sept., 1934] NEGATIVE OF WIDER USEFULNESS 165 

graphic emulsion, the term "grain" refers to the lack of continuity 
within given densities in an image projected to many times its normal 
size, an effect produced by the grouping of silver particles about 
developing nuclei in the film. Fundamentally, the graininess ap- 
parent in motion picture projection is a product of the negative. 
Grain begins in the negative. Subsequent printing and duplicating 
processes tend to multiply the effect rather than merely to perpetu- 
ate it. Any considerable correction for graininess in motion picture 
projection, therefore, must begin with the original negative. 

Superpan negative film provides the professional motion picture 
industry with a very fine-grained, super-sensitive type of film.* It 
provides, in a high-speed negative, a fine-grain quality that has been 
regarded in the past as incompatible with extremely rapid emulsions. 
It is the successful culmination of a long period of experimentation 
and research and the development of an entirely new technic in 
photographic emulsion making. 

Color- Sensitivity. Apart from its great importance in natural color 
photography, the subject of color-sensitivity of a new motion picture 
negative film is of particular interest in black-and-white reproduction. 
The mastery of panchromatic technic still engages the interest and 
efforts of cameramen, make-up experts, and others engaged in motion 
picture photography. It can not yet be regarded as a finished art, 
for the pictorial possibilities of modern panchromatic emulsions have 
not yet been completely explored 

Basically, the color response of Superpan negative film is far re- 
moved from the color-sensitivity pattern of the older super-sensitive 
panchromatic film that preceded it the film with the panchromatic 
sensitivity that made the word "super-sensitive" almost synonymous 
with "super-red-sensitive." The limitations and technical difficulties 
imposed by highly red-sensitive emulsions were tolerated because of 
the tremendous speed advantages those emulsions possessed in com- 
parison with earlier types of negative film. But they did usher in 

* It is well known that in the reversal process fine-grain results are attained 
that are superior to those attainable with negative films. This decrease in grain 
size is effected by the reversal process itself, which removes the more coarsely 
grained image and leaves a positive image composed only of the fine-grain con- 
stituents of the original emulsion. However, the reversal process has not been 
extensively applied to professional motion pictures. Experiments are under way 
with 35-mm. Agfa Reversible Superpan film that offer promise of successful appli- 
cation to professional motion picture photography where extremely fine-grain 
results should be attained. 



166 P. ARNOLD 

a new era in sensitization by stimulating manufacturers in the search 
for and discovery of new sensitizing agents (Fig. 5). 

The term "panchromatic" has ceased to be a definition for a single 
type of emulsion. It is now possible to make a silver halide emulsion 
sensitive to almost any given band of wavelengths, within the visible 
spectrum and beyond, into the infra-red. It is also possible to pro- 
duce a maximum, or peak, of sensitivity at practically any desired 
region within that range.* The task of the film manufacturer has 
become one of synthesis rather than one of discovery. The emulsion 
chemist today has at his command an extensive array of specific 
sensitizers which he can combine in innumerable degrees and pro- 
portions. Almost any desired pattern of sensitivity can be produced. 

Into a market already supplied with two popular types of high- 
speed panchromatic emulsions, similar in range of sensitivity but 




FIG. 5. Spectral sensitivity of Superpan. 

differing in their maximum response, no hesitancy is felt in introduc- 
ing a third type with its own individual sensitivity characteristics. 
The spectral sensitivity of Superpan negative was not designed to be 
identical to the color response of the human eye under a specific 
light condition. It is, however, quite possible to arrange illumina- 
tion under which Superpan would exhibit exactly the same color 
response as the retina. Realizing that the faithfulness of black- 
and-white rendition is largely determined by the quality of illumina- 
tion, the endeavor has been to produce a combination of specific 
sensitivities that would afford the widest possible latitude in color 
rendition to complement its wide latitude in exposure and develop- 
ment, and to produce a negative material of maximum usefulness. 

* The ability of the modern emulsion maker to sensitize at will is illustrated by 
the recent development of a new Agfa 16-mm. reversible film. The requirements 
of the amateur cinematographer for outdoor work during the spring and summer 
months are most adequately met by a film of high speed and high sensitivity to 
yellow and green colors without red sensitization. Fine-grain Plenachrome Re- 
versible film has been given such a high sensitivity to yellow and green that it 
gives very good correction for the colors most predominant in summer landscapes 
even without the use of filters. 



RECENT OPTICAL IMPROVEMENTS IN SOUND- 
FILM RECORDING EQUIPMENT* 

W. HERRIOTT** AND L. V. FOSTERf 



Summary. Improvements in sound-film recording equipment relating to in- 
creased high-frequency response and volume range are discussed. New low power 
exciter lamps and new types of recording objective lenses have been developed. A 
lamp adjustment optical system and split-beam monitoring equipment are described. 



Improvements in Western Electric sound-film recording equipment 
have recently been effected which offer greater convenience of operation 
and superior frequency response characteristic and volume range. 
These improvements relate to the development of new exciter lamps, 
a lamp adjustment optical system, split-beam monitoring equip- 
ment, and two new types of recording objective lenses. 

The maximum area of the light-valve aperture which it is required 
to illuminate is 0.250 inch by 0.002 inch. The condensing lens has a 
magnification of approximate unity, and it is obvious that only a 
small area of the filament is effective in illuminating the light -valve 
aperture. 

In Fig. 1 are shown five types of exciter lamps that have been 
employed either in commercial or experimental light-valve recording. 
An effort has been made to reduce the high power requirement of 
lamps of the early types, and it has been found possible to employ 
lamps of much lower current rating, making use of filaments of the 

I coiled type rather than of the ribbon type, which impose an ab- 
normal drain upon the battery supply, and a resulting high cost 
for power. The 9.5-ampere, 85-watt coiled filament lamp shown 
fourth from the left in Fig. 1 is used in studio recording, but the 4.0- 
ampere, 8.5-volt coiled filament lamp is now being introduced into 
commercial practice. Satisfactory recordings have been made 
with the 2-ampere lamp shown at the extreme left. The reduction in 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Bell Telephone Laboratories, New York, N. Y. 
t Bausch & Lomb Optical Co., Rochester, N. Y. 

167 



168 



W. HERRIOTT AND L. V. FOSTER 



[J. S. M. P. E. 



the current demand accomplished in successive developments has 
resulted largely from redesigning the filament from the standpoint of 
the tungsten area required to illuminate properly the image of the 
light-valve formed by the objective lens at the film plane. 

The length of the filament is established largely by lens and light- 
valve aperture considerations, from the standpoint of the minimum 
loss of exposure that can be tolerated at the sides of the sound track. 
The influences of end-cooling and of partial pencils transmitted by 
the optical system are two of the factors involved. 

The height of the tungsten area is established largely by the re- 




FIG. 1. Five types of exciter lamps used for commercial or 
experimental light-valve recording. 

quirement of ease of adjusting the exciting lamp with reference to its 
image at the aperture of the light- valve. If the coil diameter or the 
filament height is too small the adjustment of the height of the lamp 
and its orientation become critical. 

Excessive filament area is useless, especially in the ribbon filament 
type of lamp adjusted to the focal position. Coiled filament lamps 
are employed in an out-of-focus position, being moved toward the 
condensing lens a short distance, just sufficient to avoid imaging the 
coil structure upon the unmodulated sound track. 

Fig. 2 shows a series of approximately full-sized images obtained 



Sept., 1934] IMPROVEMENTS IN RECORDING EQUIPMENT 169 

with the 4-ampere, coiled filament lamp for a number of different 
conditions of focus, showing that a reasonably uniform exposure is 
possible over the area of the light- valve aperture. No loss of image 
brightness results from using the exciter lamp in an out-of-focus 
position if the filament is of the correct size, although a small de- 
crease of efficiency due to the smallness of the filament is easily com- 
pensated for by operating the lamp at a slightly higher color-tempera- 
ture. 

In Fig. 3 are shown microdensitometric traces of unmodulated 
sound tracks made with the lamp in several positions. The coil 
structure is very apparent in the focal position, but becomes obscure 
to a satisfactory degree as shown in the lower curves of Fig. 3. Visual 




FIG. 2. A series of approximately full-sized images 
obtained with a 4-ampere, coiled filament lamp for different 
conditions of focus. 



examination of the sound track exposed with the lamp properly ad- 
justed shows no trace of striation due to the coil structure. 

Small coiled filament lamps may be used if screws are provided for 
adjusting the lamp mounting and if use is made of a simple optical 
device for determining the correct position of the lamp and permitting 
the accurate replacement and adjustment of new lamps in a simple 
manner. This "lamp adjustment optical system" is shown in Fig. 4. 
It consists of an objective lens at the rear of the exciter lamp for 
imaging the filament upon a ground-glass screen on which cross-lines 
are etched. The exciter lamp with the small coiled filament is first 
adjusted to record satisfactorily in the desired out-of-focus position. 
The objective lens of the lamp adjustment system is adjusted to 



170 



W. HERRIOTT AND L. V. FOSTER 



[J. S. M. p. E. 



image the lamp filament sharply upon the ground-glass screen. The 
crossed-line screen is then adjusted so that the horizontal line bisects 
the image of the coil axially and the vertical line bisects the image 
longitudinally. The device has proved very convenient for replacing 
and inspecting low-power recording lamps. 

Improvements in monitoring systems have been effected by re- 
moving the photoelectric cell from its position behind the film, where 
it was subject to mechanical vibration and where it could be acted 




FIG. 3. Microdensitometric traces of unmodulated 
sound tracks made with the recording lamp in several 
positions. 



upon only by light that was transmitted by the raw-stock film. Both 
these objections served to impair the sound quality by introducing 
noise. A system of split-beam monitoring has been developed in 
which a portion of the modulated light passed by the light-valve is 
intercepted and deflected to the photoelectric cell. The lamp, con- 
denser lens, and the light-valve apertures can be so designed that a 
large proportion of the modulated light will be available for the 
purpose. It is quite possible to utilize as much light for the monitor- 
ing as is required for exposing the sound-film record, or even more. 



Sept., 1934] IMPROVEMENTS IN RECORDING EQUIPMENT 



171 



Fig. 5 illustrates one form of the split-beam monitoring system, in 
which the condensing lens is purposely over-apertured in order to 
transmit through the valve a beam of modulated light having a large 
dispersive angle. Only the central portion of the beam reaches the 
objective lens (shown on the right), the remainder being reflected by 



LIGHT 
VALVE 




RECORDING 
OBJECTIVE 



CROSS LINE SCREEN 

FIG. 4. 



The lamp adjustment optical system. 



a concave annular mirror to a small prism having a collective lens 
cemented to its surface of emergence. The light rays are therefore 
collimated, and directed toward the photoelectric cell shown in 
dotted outline on the schematic drawing. Other devices essentially 
similar to this have been adopted and have given satisfaction in 
service. 




FIG. 5. One form of the split-beam monitoring system. 

The objective lens employed in the sound-film recorder must 
accurately image the aperture formed by the light- valve ribbons upon 
the layer of emulsion on the photographic film. The use of the 
tungsten lamp as a light source imposes an additional requirement, 



172 



W. HERRIOTT AND L. V. FOSTER 



[J. S. M. P. E. 



that the relative aperture of the lens must be fairly great in order to 
attain an adequate exposure with a reasonable lamp life. This 
condition applies particularly when positive, or blue-sensitive, film is 
used as the recording medium. 




1000 2000 



3000 4000 5000 6000 7000 8000 
FREQUENCY IN CYCLES PER SECOND 



9000 10,000 



FIG. 6. Chromatic correction of lens to match color-sensitivity of posi- 
tive film. 

FIG. 7. The improvement achieved in high-frequency response with 
the objective lens corrected for chromatic aberration as in Fig. 6. 

The height of the light-valve aperture varies from 0.000 inch to 
0.002 inch for full modulation. The average, or unmodulated, spac- 
ing is 0.001 inch, for systems not employing noise-reduction methods, 
and approximately 0.0003 inch when noise-reduction methods are 




FIG. 8. Photographs of a ruled grating made with (a) a new lens cor- 
rected for chromatic aberration as in Fig. 6, and (6) an old lens. 



applied. In the latter case, the modulation ranges about this small 
spacing for low levels of applied signal. To those unfamiliar with 
the difficulties of imaging small objects, the problem may not appear 
to be particularly troublesome ; but the lens designer realizes that he 



Sept., 1934] IMPROVEMENTS IN RECORDING EQUIPMENT 



173 



is definitely limited in attaining accurate images of the light-valve 
aperture at every instant of its cycle of operation. 

In the first place, as noted before, the requisite relative aperture of 
the lens is fairly large, which condition demands careful correction of 
spherical and chromatic aberration, in order that the circles of con- 
fusion may be reduced to a minimum size. In addition, the image of 



f/G. 

9 




1000 2000 



300O 4000 5000 6000 7000 
FREQUENCY IN CYCLES PER SECOND 



8000 9000 10,000 




60001 5500 5000| 4500 

D F G 

WAVELENGTH IN ANGSTROMS 



3500 



10 

la 

Old 
UJ? 

>!-> 5 



FIG. 




1000 2000 



3000 4000 5000 6000 700O 
FREQUENCY IN CYCLES PER SECOND 



8000 9000 10,000 



FIG. 9. Improvement in frequency response achieved with a lens of 
shorter focal length developed for use in small modulator units employing 
only positive film. 

FIG. 10. Correction of apochromatic lens for use with panchromatic 

film. 

FIG. 11. Improvement in frequency response achieved with corrected 
apochromatic lens over the old achromatic objectives used with panchro- 
matic film in portable recorders. 



such a small aperture can not be perfect because of the diffraction that 
occurs when light passes through very small openings. That diffi- 
culty is, of course, beyond the control of the lens designer, and his 
only recourse is to choose the largest practicable aperture for the lens 
system compatible with the adequate correction of spherical and 
chromatic aberration. 

Practically all sound records are made on either positive or panchro- 



174 W. HERRIOTT AND L. V. FOSTER 

matic film. Early objective lenses used for recording sound were 
corrected for chromatic aberration in the classical manner, in which 
the yellow and the blue images are made to coincide. Images corre- 
sponding to other colors do not lie in the same plane as the yellow 
and the blue images, but lie some nearer the lens and some farther 
from it. Positive film, however, is sensitive principally to a band of 
spectral radiations of somewhat shorter wavelength than that of the 
blue selected for chromatic correction of the early recording lenses. 
It seemed advisable, therefore, to experiment with a lens corrected 
specifically for the limited spectral band to which the film is most 
sensitive in order to determine whether the improvement to be ex- 
pected on theoretical grounds might be realized in practice. A lens 
was made with the chromatic correction shown in Fig. 6, wherein the 
image distances for 4040 and 4860 A are equal. The result was a 
decided improvement in high-frequency response (Fig. 7). 

Photographs made in the focal region with both lenses are shown in 
Fig. 8. These are photographs of a ruled grating on a plate inclined 
at a very small angle to the axis of the lens in such a manner that part 
of the plate is ahead of the true focal plane and part of the plate is 
behind it : (a) was photographed with the new lens ; (b) with an old 
lens. A similar lens of shorter focal length has been developed for 
small modulator units employing only positive film. The improve- 
ment in the frequency response characteristic of this lens is shown 
in Fig. 9. 

When the picture and the sound track are recorded on the same 
film, as in the newsreel type of equipment, the film must be panchro- 
matic or orthochromatic, in view of the picture requirements. This 
necessitates, in the case of panchromatic film, recording a sound track 
on an emulsion that is sensitive to the entire visible spectrum, instead 
of to a relatively narrow band in the blue. The apochromatic lens 
provides the closest possible approach to the ideal for panchromatic 
film, so a lens of that character was designed with a chromatic correc- 
tion such as shown in Fig. 10. The improvement in response with the 
apochromatic over the old achromatic objective with panchromatic 
film is shown in Fig. 11. 

REFERENCE 

1 HERRIOTT, W.: "A Method of Measuring Axial Chromatic Aberration of an 
Objective Lens," /. Opt. Soc. Amer., 23 (April, 1933), No. 4, p. 123. Also /. Soc. 
Mot. Pict. Eng. t XX (April, 1933), No. 4, p. 323. 



PIONEERING INVENTIONS BY AN AMATEUR* 
FREDERIC E. IVES** 



Summary. A short account of the early scientific interests of the author, an 
honorary member of the Society of Motion Picture Engineers and one of the pioneers 
in color photography, is followed by a brief description of his important accomplish- 
ments and patents. 

The well-balanced and conventionally educated man can do 
many things well, and usually makes a useful citizen. Some men, 
by freak of heredity, are conspicuously better equipped for special 
accomplishment. Thus we find that some are instinctively poli- 
ticians, merchants, mechanics, poets, artists, fiction writers, etc., and 
in order to distinguish themselves, must work assiduously along the 
line of their special talents. If they attempted to excel in several 
fields at once, life would be too short for sustained achievement in 
any one field. 

My own case is one of predominant eye-mindedness as distinguished 
from ear-mindedness. As a child, I could never learn anything word 
for word by oral teaching, but would repeat the thought in my own 
language. On the other hand, I could so fix the image of a printed 
or written paragraph in my mind as to be able to recall and read 
it off as though it were in front of my eyes. My thoughts were in 
ideas and images, and not in sounds, and it would have been a hope- 
less task to undertake to make a musician out of me. But I could 
visualize and see the relationship of material things as though they 
were before my eyes. About as soon as I commenced to talk, I could 
draw pictures, and when, at the age of seven, I made a fairly correct 
detailed drawing of a steam locomotive from memory, my father tore 
it up and scolded me for so wasting my time. He said I was big 
enough to begin doing useful work on the farm, and proceeded to 
teach me how to spread fertilizer. The fact is that my characteristic 
instincts and talents were inherited from my mother, while an inces- 
sant effort to do useful work was characteristic of my father. 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Philadelphia, Pa. 

175 



176 F. E. IVES [J. S. M. P. E. 

EARLY INTEREST IN COLOR IN NATURE 

One of my earliest and most impressive dreams was that of seeing 
the earth and the skies as one glorious pageant of color, since when 
I have always been very color-conscious. I might have become an 
artist but for the fact that I did not possess the poetic imagination, 
and was drilled to think that everything must have practical value. 

My father, on account of ill health, gave up his farm and became 
a country village storekeeper when I was ten years of age, and I 
found my first great interest in life in reading an old copy of a school- 
book on natural philosophy, which had somehow gotten into the 
stock of the store. Then I became possessed of a one-inch focus, 
double convex lens, and developed an interest in optics that became 
almost a passion. My father thought I was wasting my time and 
sent me to live with a farmer relative. My schooling, over brief 
periods and in different places, never carried me through pri- 
mary arithmetic. Professor Michelson once asked me how I ever 
came to do the work I did in applied optics without the aid of mathe- 
matics. I reminded him of Robert Louis Stevenson's explanation of 
his father's similar activity as being due to a "sentiment" for optics. 
The fact was that I could so clearly visualize the path of light through a 
refracting medium that a little trial-and-error experimentation brought 
sufficiently accurate results for my purposes. Edison's method of 
"calculating" the cubic capacity of a lamp bulb, for example, was to 
fill it with water and pour the water into a graduate. 

FIRST INTEREST IN PHOTOGRAPHY 

Just prior to his death, at the age of 34, my father solemnly advised 
me to "stay on the farm." Instead, I became a clerk in a country general 
store and an amateur printer. Before I was quite 14 years of age, I 
apprenticed myself in the printing office of the Litchfield, Connecticut, 
Enquirer, and was a full-fledged journeyman printer before I was 17. 

While still a printer's apprentice, I made my first photographs, 
by the old wet-plate process, with a camera that I constructed from 
a cigar-box and a spectacle lens, using some of my grandmother's 
kitchen crockery for chemical containers. Attempting to teach my- 
self wood engraving, I dreamed of making printing plates by a photo- 
graphic process. 

WORK AT PHOTOGRAPHIC LABORATORY, CORNELL UNIVERSITY 

At the age of 19, I applied for the position of photographer in the 
photographic laboratory at Cornell University. There I invented 



Sept., 1934] PIONEERING INVENTIONS 177 

and demonstrated photo-engraving processes, and made the first 
successful commercial use of color-sensitive photographic plates. 
The discovery by Vogel, in 1873, that some English collodion dry 
plates that had been stained with corallin dye to prevent halation, 
were sensitive to the blue-green spectral rays, a fact then regarded 
as only of scientific interest, spurred me to experiments that resulted 
in a commercially practical and useful process with wet collodion sil- 
ver bromide plates bathed in an alcoholic solution of blue-myrtle 
chlorophyll, washed, exposed, and developed without drying, and 
used with a glass tank filled with potassium bichromate solution as 
a color screen. 

This process provided sensitivity throughout the spectrum, and 
was fast enough for landscape and commercial photography with 
sunlight illumination. (!VES, F. E.: "On Photographing Color," 
Phil. Phot., 16 (Dec., 1879), p. 365.) 

Having proceeded so far, I prophesied to a group of students that 
within 10 years photographic processes would supersede wood engrav- 
ing and chromo-lithography. I made too little allowance for the 
conservatism of established custom and opinion, but I had the true 
vision. 

My first color-separation negatives for three-color photography 
and three-color halftone plates were made on the chlorophyll plates 
and with successive exposures with red, green, and blue filters in 
the form of liquid solutions in the glass tank. 

MANUFACTURE OF FIRST HALFTONE PLATES 

In 1881 I was the first to manufacture cross-line halftone process 
plates to order for printers and publishers, and made the first three- 
color halftone process prints. That was the practical beginning of a 
great revolution in the printing and publishing business, but was slow 
to develop extended use because its full success in large-scale produc- 
tion as we know it today depended upon adapting printing machinery, 
inks, ink distribution, paper, etc., to meet the special requirements of 
the processes. 

The three-color halftone specimen made at that time was a repro- 
duction of a chromolithograph and had all the characteristics of 
present-day practice, but it was realized that the time and conditions 
were not then ripe for its commercial exploitation. I have none of 
the prints left, but one that had the date of printing endorsed on its 
back was deposited in the print room of the Smithsonian Institution 




178 



F. E. IVES 



[J. S. M. P. E. 



some years ago. Printing press, ink and paper manufacturers, and 
pressmen resented the necessity for the changes required to do justice 
to the processes and were slow to adopt them. 

DEMONSTRATION OF ADDITIVE TRICOLOR PHOTOGRAPHY 

While that was going on, I made the first convincing demonstra- 
tion of additive process trichromatic photography at the Franklin 
Institute in February, 1888 a reproduction by triple lime light lan- 
tern projection of an autumn landscape, the negatives for which I 
had made in 1880 on my chlorophyll plates. It was heralded in 
the newspapers of that day as a perfectly convincing demonstration 
of the reproduction of natural colors by a photographic process. A 
diagram of the lantern is shown in Fig. 1. 




FIG. 1. 



Triple lime light projector for three- 
color additive process. 



A travel lecture on Yellowstone Park was given by W. N. Jennings 
at the Franklin Institute on December 18, 1891, illustrated by my 
subtractive process, natural color lantern slides, made by superposed 
dyed gelatin photo relief prints. 

These prints were made by coating celluloid sheets with bichro- 
mated gelatin and exposing them to sunlight partially through the 
celluloid film held against the negatives (a single 3-inch glass negative 
made in the camera described in my U. S. Pat. 475,084 was then used). 
The three transparent relief images were dyed, respectively, minus 
red (cyan blue), minus green (carmine or eosine), and minus blue 
(yellow), and superposed in register between glasses with Canada 
Balsam cement to eradicate refracting effects of the rather high relief. 
The process was subsequently improved by using a coating of silver 
bromide gelatin emulsion, and still later by incorporating a soluble 



Sept., 1934] 



PIONEERING INVENTIONS 



179 



yellow dye to limit the penetration of light and to make the reliefs 
so tenuous that, when varnished, they did not have to be sealed with 
balsam. The results, on projection, were the same in either case. 

Very favorable accounts of the Franklin Institute lecture were 
published in the Philadelphia Inquirer, Dec. 19, 1891, and many other 
papers. Some of the same lantern slides were shown at the Royal 
Institute in London, May 17, 1892, and described in the London 
Daily Graphic of May 18, 1892. 

Following the lecture at the Franklin Institute, the announcement 
was made of my first camera producing three geometrically equal 




FIG. 2. Photochromoscope viewing device. 

images on one plate at one exposure. This camera was used in 

Yellowstone Park in 1890, and a patent for it issued May 17, 1892. 

The same optical system was used in my first form of photochromo- 

scope, with three images on a single glass plate (Fig. 2). 
The following inventions appeared from time to time: 
The stereoscopic photochromoscope (and camera) with colored 

glass transparent reflectors and folding chromograms (U. S. Pat. 

531,040, issued Dec. 18, 1894). 

Transparent refracting line-screen with particolored light source 

and juxtaposed line color records (U. S. Pat. 666,424, issued Jan. 22, 



180 F. E. IVES [J. S. M. P. E. 

1901), a significant fore-runner of the Kodacolor amateur motion pic- 
ture process, and recently adapted by Dr. Herbert Ives as a conveni- 
ent pocket-sized device for viewing Kodacolor "stills." 

Trichromatic plate pack with superficial dye screen coating on 
face of emulsion an element in all bipacks and tripacks (U. S. Pat. 
927,144, issued July 6, 1909). 

Production of tenuous photographic relief prints, in bichromated 
gelatin by incorporating a non-actinic dye to limit penetration of 
the light in printing followed by dye coloring (U. S. Pat. 980,962, 
issued Jan. 10, 1911). 

Production of microscopically sharp dye prints by imbibition print- 
ing (Pat. applications March 9, 1912, and July 12, 1912; U. S. Pats. 
1,106,816, Aug. 11, 1914, and 1,121,187, Dec. 15, 1914). 

A light-splitting element adapted to produce two geometrically 
alike but different color-selection images from one point of view upon 
one plane in a motion picture camera (Pat. application July 26, 1913; 
U. S. Pat. 1,169,161, issued Jan. 25, 1916). 

Dichroic light-splitting reflector in color cameras (Pat. application 
March 11, 1914; U. S. Pat. 1,238,775, Sept. 4, 1917). 

In February, 1914, first two-color motion pictures produced in a 
single coating of ordinary motion picture positive film, one image 
made from an insoluble color and the other from a soluble dye- 
stuff (Pat. application July 1, 1914; U. S. Pats. 1,170,540, Feb. 8, 
1916; 1,278,667; 1,278,668; 1,306,616; 1,306,904). 

Tenuous gelatin relief prints by "gaslight" printing,, development, 
bleach-selective hardening, and warm water development (Pat. 
application March 13, 1915; U. S. Pat. 1,186,000, issued June 6, 
1916). 

Two-color cinematograph prints made by cementing two differently 
colored strips of images together (Pat. application, Feb. 4, 1916; U. S. 
Pat. 1,248,864, Dec. 4, 1917). 

Successful motion picture negatives made with bipack films (Pat. 
1,320,760, issued Nov. 4, 1919). 

Dichroic red-to-yellow image, applied in perfected cine and poly- 
chrome print processes (Pat. 1,376,940 issued May 3, 1921). 

Light-splitting attachment for cinematograph camera permitting 
the use of large aperture lenses (Pat. application Sept. 13, 1919; 
U. S. Pat. 1,383,543, July 5, 1921). 

Dye toning of bleached silver images bleached with ferricyanide- 
chromic acid (several formulas; no patent applied for). 



Sept., 1934] PIONEERING INVENTIONS 181 

Perfected polychrome process for prints for the album or framing. 
J. Opt. Soc. ofAmer., 22 (April, 1932), No. 4. 

A list of other inventions include the following : 

The now universally used cross-line screen and diaphragm control 
halftone process. 

A practical suggestion for transmission of photographic images by 
wire. 

Glass-sealed gelatin and collodion color-screens (ray filters). 

Photogravure printing plates. 

Parallax stereogram and changing pictures. 

Modern type of short- tube, single-objective binocular microscope. 

Glass-sealed diffraction grating replicas. 

Diffraction photochromoscope. 



SOCIETY ANNOUNCEMENTS 

NOMINATIONS OF OFFICERS FOR 1935 

At the last meeting of the Board of Governors the following were nominated for 
office in the Society for the year 1935: 

H. G. TASKER, President 

E. HUSE, Executive Vice- President 

J. I. CRABTREE, Editorial Vice- President 

W. C. KUNZMANN, Convention Vice- President 

J. H. KURLANDER, Secretary 

T. E. SHEA, Treasurer 

M. C. BATSEL, Governor 

S. K. WOLF, Governor 

H. RUBIN, Governor 

T. RAMSAYE, Governor 

Ballots for voting on the nominations will be mailed to the Honorary, Fellow, 
and Active members of the Society about September 15th. Of the four nominees 
for Governor, two are to be elected. The President, Executive Vice-President, 
Secretary, and Treasurer hold office for one year; the other Vice-Presidents and 
the Governors, for two years. Ballots will be counted, and the results announced, 
at the Fall, 1934, Convention, on October 29th, at the Hotel Pennsylvania, New 
York, N. Y. The successful candidates will assume office on January 1, 1935. 

Members of the Board of Governors whose terms do not expire until January 
1, 1936, exclusive of the Chairmen of Local Sections, whose terms expire Jan- 
uary 1, 1935, are as follows: 

L. A. JONES, Engineering Vice-President 
O. M. GLUNT, Financial Vice-President 
A. S. DICKINSON, Governor 
H. GRIFFIN, Governor 
W. B. RAYTON, Governor 



SECTIONAL COMMITTEE ON STANDARDIZATION 

In the past, standards formulated and proposed by the Society of Motion 
Picture Engineers have cleared through the American Standards Association, 
assuming the status of national standards through what was known as the "pro- 
prietary sponsorship plan." 

The Society has recently sponsored a proposal to the A. S. A. that the project 
be changed from the proprietary plan to the administrative sectional committee 
method, under which a committee would be formed consisting of representatives 
of large and important groups of the industry interested in standardization, and 
would act to nationalize proposed standards after they have cleared through the 
S. M. P. E. as the sponsor. Discussions concerning the formation of the sectional 
committee are now going forward. 
182 



SOCIETY ANNOUNCEMENTS 183 

FALL CONVENTION, 

OCTOBER 29TH TO NOVEMBER 1ST, INCL., 

HOTEL PENNSYLVANIA, 

NEW YORK, N. Y. 

Details concerning the approaching Convention will be mailed to the member- 
ship of the Society in the near future. Attention is called to the fact that the date 
of the Convention was erroneously given in the August issue of the JOURNAL, and 
that the correct dates are as here stated. 

The Convention will begin Monday morning, Oct. 29th, with Society business 
and reports of Committees, followed by an informal get-together luncheon at 
noon, at which the members will be addressed by several prominent speakers. 

All technical sessions and film programs will be held in the Salle Moderne, on 
the eighteenth floor of the Hotel, where will also be located the registration head- 
quarters, apparatus exhibit, and other activities. Plans are being made to include 
several interesting lectures on topics of current interest by prominent engineers of 
the industry, as well as tours of inspection to important studios, laboratories, or 
manufactories in the New York district. 

The S. M. P. E. Semi-Annual Banquet will be held on the evening of Wednes- 
day, Oct. 31st: an evening of dancing and entertainment. The exhibit of newly 
developed motion picture apparatus will be held on the Convention floor of the 
Hotel, and is open to all manufacturers or distributors of equipment. Arrange- 
ments for entering the exhibit can be made by addressing the General Office of 
the Society at the Hotel Pennsylvania, New York, N. Y. 

Excellent accommodations are assured by the Hotel management, and mini- 
mum rates are guaranteed to delegates to the Convention. Reservations should 
be made as early as possible in order to be assured of satisfactory accommodations. 

A detailed program of the Convention will be mailed to the members in the 
near future. An interesting technical program is being arranged by the Papers 
Committee, under the direction of Mr. J. O. Baker, Chairman, and Mr. J. I. 
Crabtree, Editorial Vice- President. Mr. W. C. Kunzmann is attending to the 
various facilities of the Convention, assisted by Mr. H. Griffin, in charge of pro- 
jection, Mr. J. Frank, Jr., in charge of the Apparatus Exhibit, and Mrs. O. M. 
Glunt, Hostess. 



STANDARD S. M. P. E. 

VISUAL AND SOUND TEST REELS 

Prepared under the Supervision 

OF THE 
PROJECTION PRACTICE COMMITTEE 

OF THE 
SOCIETY OF MOTION PICTURE ENGINEERS 



Two reels, each approximately 500 feet long, of specially pre- 
pared film, designed to be used as a precision instrument in 
theaters, review rooms, exchanges, laboratories, and the like 
for testing the performance of projectors. The visual section 
includes special targets with the aid of which travel-ghost, 
lens aberration, definition, and film weave may be detected 
and corrected. The sound section includes recordings of 
various kinds of music and voice, in addition to constant 
frequency, constant amplitude recordings which may be used 
for testing the quality of reproduction, the frequency range 
of the reproducer, the presence of flutter and 60-cycle or 96- 
cycle modulation, and the adjustment of the sound track. 
Reels sold complete only (no short sections). 

PRICE $37.50 FOR EACH SECTION, 
INCLUDING INSTRUCTIONS 

(Shipped to any point in the United States) 

Address the 

SOCIETY OF MOTION PICTURE ENGINEERS 

HOTEL PENNSYLVANIA 
NEW YORK, N. Y. 



JOURNAL 



OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 

Volume XXIII OCTOBER, 1934 Number 4 






CONTENTS 

Page 

Piezoelectric Frequency Control F. R. LACK 187 

Piezoelectric Microphones A. L. WILLIAMS 196 

Recent Improvements in Equipment and Technic in the Pro- 
duction of Motion Pictures. E. A. WOLCOTT 210 

List of Members of the Society 215 

Fall Convention, Hotel Pennsylvania, New York, N. Y., 

Oct., 29-Nov. 1, 1934 241 

Society Announcements 243 



JOURNAL 

OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 



SYLVAN HARRIS, EDITOR 

Board of Editors 
J. I. CRABTREE, Chairman 

O M. GLUNT A. C. HARDY L. A. JONES 

J. O. BAKER 



Subscription to non-members, $8.00 per annum; to members, $5.00 per annum, 
included in their annual membership dues; single copies, $1.00. A discount 
on subscriptions or single copies of 15 per cent is allowed to accredited agencies. 
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton 
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y. 

Published monthly at Easton, Pa., by the Society of Motion Picture Engineers 

Publication Office, 20th & Northampton Sts., Easton, Pa. 
General and Editorial Office, Hotel Pennsylvania, New York, N. Y. 
Entered as second class matter January 15, 1930, at the Post Office at Easton, 
Pa., under the Act of March 3, 1879. Copyrighted, 1934, by the Society of 
Motion Picture Engineers, Inc. 

Papers appearing in this Journal may be reprinted, abstracted, or abridged 
provided credit is given to the Journal of the Society of Motion Picture Engineers 
and to the author, or authors, of the papers in question. Exact reference as to 
the volume, number, and page of the Journal must be given. The Society is 
not responsible for statements made by authors. 



Officers of the Society 

President: ALFRED N. GOLDSMITH, 444 Madison Ave., New York, N. Y. 
Executive Vice-P resident: HAROLD C. SILENT, 7046 Hollywood Blvd., Los 

Angeles, Calif. 

Engineering Vice-President: LOYD A. JONES, Kodak Park, Rochester, N. Y. 
Editorial Vice-President: JOHN I. CRABTREE, Kodak Park, Rochester, N. Y. 
Financial Vice-P resident: OMER M. GLUNT, 463 West St., New York, N. Y. 
Convention Vice-President: WILLIAM C. KUNZMANN, Box 400, Cleveland, Ohio. 
Secretary: JOHN H. KURLANDER, 2 Clearfield Ave., Bloomfield, N. J. 
Treasurer: TIMOTHY E. SHEA, 463 West St., New York, N. Y. 

Governors 

EUGENE COUR, 1029 S. Wabash Ave., Chicago, 111. 
ARTHUR S. DICKINSON, 28 W. 44th St., New York, N. Y. 
RALPH E. FARNHAM, Nela Park, Cleveland, Ohio. 
HERBERT GRIFFIN, 90 Gold St., New York, N. Y. 
EMERY HUSE, 6706 Santa Monica Blvd., Hollywood, Calif. 
WILBUR B. RAYTON, 635 St. Paul St., Rochester, N. Y. 
HOMBR G. TASKBR, 41-39 38th St., Long Island City, N. Y 



PIEZOELECTRIC FREQUENCY CONTROL* 
F. R. LACK** 

Summary .This paper discusses the use made of the piezoelectric effect in de- 
signing sub-standard timekeepers and frequency generators. The nature of the 
piezoelectric effect is outlined and mention is made of the various classes of crystals 
in which it is found. The technic of setting up, electrically, various types of me- 
chanical vibrations in piezoelectric crystals is described together with methods of 
obtaining very high frequencies. Other applications of the piezoelectric effect, such 
as to loud speakers, submarine signaling, etc., are briefly reviewed. 

With the advent of high-frequency carrier communication, both 
wire and radio, the development and wide distribution of electric 
clocks, and the increasing demand for synchronizing motion at a 
distance, has come a need for extending and refining our methods 
of measuring time and frequency. The world standard of time is 
astronomical, and depends upon the period of rotation of the earth. 
Sub-standard chronometers of various forms are used to divide the 
period of rotation into usable hours, minutes, and seconds, and 
are, for the most part, mechanical vibrating or oscillating systems 
having very constant periods of oscillation. Every system is equipped 
with some means of integrating or counting the number of oscilla- 
tions in a 24-hour period. 

Probably the best-known mechanical oscillator is the pendulum, 
the classical timekeeper. The period of oscillation of a pendulum 
depends, to a first approximation, only upon the force of gravity 
and the length of the pendulum. Because the gravitational force is 
constant and the length of the pendulum can be maintained constant 
to a high degree of precision, a pendulum constitutes a very accurate 
timekeeper. Such oscillators may be, of course, frequency genera- 
tors as well as timekeepers. Most pendulum systems are so ar- 
ranged as to be able to produce one or more electrical impulses per 
second. Although second impulses may be used to synchronize 
other clocks, when such a generator is used to produce higher fre- 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Bell Telephone Laboratories, New York, N. Y. 

187 



188 F. R. LACK [J. S. M. P. E. 

quencies, considerable complication of apparatus ensues. Hence, 
when the demand arose for producing accurately known audio fre- 
quencies, the pendulum was replaced by magnetically or electro- 
statically excited tuning-forks. 

The period of oscillation of a tuning-fork depends upon its di- 
mensions and the density and mechanical elasticity of the material 
of which it is made. For frequency stability, therefore, those proper- 
ties must not vary. The metal used for the forks must be carefully 
aged, and some form of temperature control provided in order to 
attain adequate precision. Forks can be constructed for frequencies 
up to 10 kc. and beyond, although above 10 kc. the dimensions of 
the fork become very small. 

To check the frequency of such a system it is customary to count 
the number of cycles in an interval of standard time. In order to do 
so, the generated frequency is stepped down electrically in exact 
submultiples to a value suitable for operating a synchronous-motor 
clock. The clock is compared with time signals based upon astro- 
nomical observations. A tuning-fork system, carefully designed, can 
be made as good a timekeeper as the best pendulum. 

With the advent of carrier telephony and radio, a demand arose 
for generators capable of producing currents of accurately known 
frequencies much greater than those readily obtainable with forks. 
To fulfill the demand, oscillators employing piezoelectric crystals 
have been used with considerable success. Such generators differ 
from the pendulum and the fork only in the mechanism used to 
sustain' the oscillation. Instead of employing mechanical or magne- 
tic forces for driving the fork, the piezoelectric effect is utilized. 
By "piezoelectric effect" is meant the property of certain crystals by 
virtue of which a mechanical stress produces an electrical charge, 
and vice versa. The effect was first discovered in crystalline quartz 
by the Curies 1 in 1880, in connection with their initial studies of 
radium. Experimental and theoretical extensions by Lippmann, 
Pockels, Voigt, 2 and others established a definite set of laws relating 
the effect to the type of crystal structure and the elasticity equations 
of the material. 

From those laws we learn that all crystals that do not possess a 
center of symmetry can be expected to exhibit the piezoelectric 
effect. Of the 32 classes of crystal structure, 20 fall into such a group, 
and hence should be piezoelectric. Only 10 per cent of the known 
minerals, however, belong to the asymmetric classes. Most of them 






Oct., 1934] 



PIEZOELECTRIC CONTROL 



189 



are unsuitable for precision oscillators, either because they are 
available only in minute specimens, or because they possess un- 
suitable mechanical properties. 

There are a few, however, that are useful. By far the most im- 
portant at the present time is quartz (Fig. 1), which is readily ob- 
tainable in large quantities at reasonable cost, and has excellent 
mechanical properties; that is, it is hard, does not change its char- 
acteristics with age, and is not hygroscopic. It is not as active 
piezoelectrically as some of the chemical crystals, but for most pur- 
poses that is not a serious disadvantage. 

For oscillators generating very high frequencies, tourmaline is 
beginning to find some application. 
Tourmaline possesses approximately 
the same properties as quartz, but 
occurs only in small crystals; and, 
as it is regarded as a semi-precious 
stone because of its color, it is quite 
expensive. There are some other 
minerals, such as boracite, scolecite, 
etc., in the same category, that could 
be used if necessary, but as they 
also occur only in minute crystals 
they are not worth considering as 
long as quartz is readily available. 

There is also a large group of 
chemical crystals, so called in order 
to distinguish them from the natural 
mineral crystals. At the head of the 
group is Rochelle salt, which is the 

most active of all known piezoelectric crystals. It is approximately 
1000 times as active as quartz. Up to now it has not been used 
for precision oscillators because of its relatively poor mechanical 
properties. However, recent improvements in the technic of grow- 
ing the crystals may lead to their reconsideration as frequency gen- 
erators. In the same group are tartaric acid, cane sugar, sodium 
chlorate, benzil, and many others. 

Before discussing the form of the piezoelectric frequency genera- 
tor, it may be well to review briefly the technic of producing me- 
chanical vibrations by means of an electrical field. 

The plates or bars that are used as vibrators may be cut from the 




FIG. 1. Typical quartz crystal 
from Brazil. 



190 



F. R. LACK 



[J. S. M. P. E 



crystal in a number of different ways, depending upon the kind of 
vibration desired, its frequency-temperature coefficient, and the 
relation of the piezoelectric effect to the axis of the crystal. In using 

2 



OPTIC AXIS 




X CUT 



FIG. 2. (upper) Relation of Jt-cut 
quartz plate to axes of mother crystal. 

FIG. 3. (lower) Application of elec- 
trodes to X-cut quartz plate. 



CUT 



FIG. 4. (upper) Relation of F-cut 
quartz plate to axes of mother crystal. 

FIG. 5. (lower) Application of elec- 
trodes to F-cut quartz plate. 



quartz for some purposes, a section (called the X cut) is cut from the 
mother crystal as shown in Fig. 2. If the electrodes are applied 
so that an electric field is established in the quartz parallel to the X 



Oct., 1934] 



PIEZOELECTRIC CONTROL 



191 





is (see Fig. 3), then there will be a mechanical expansion (or 
traction) along the Y axis, a contraction (or expansion) along the 
axis, and a shear in the YZ plane. Conversely an expansion, 
contraction, or shear of the crystal will produce an electric potential. 

Such a bar has a number of free mechanical periods. One period 
corresponds to a longitudinal vibration along the Y axis, the center 
of the bar being the node (or region 
of no motion) while the ends expand 
and contract along the Y direction. 
The frequency of vibration depends 
upon the density of quartz, its 
elasticity in the Y direction, and the 
length of the bar. As motion along 
the Y axis causes a difference of 
potential between the electrodes, by 
connecting the latter to an appro- 
priate electric circuit capable of 
supplying energy, the longitudinal Y 
vibration in the bar can be sus- 
tained electrically in much the same 
fashion as a clock-spring maintains 
a pendulum in motion through the 
escapement mechanism. 

In the same way longitudinal vi- 
brations can be set up in the X 
direction, and shear or flexural vibra- 
tions in the YZ plane. If the plate 
is cut from the crystal as shown in 
Fig. 4 (the Y cut), the electrodes 
being applied as shown in Fig. 5, 
longitudinal vibrations can no longer 
occur. Because of the shift in 
orientation, they are replaced by 
shear vibrations in the ZX and XY 

planes. The motion of the particles in a shear vibration is per- 
pendicular to the direction of propagation of the wave-front, hence 
constituting an acoustical analogue of transverse light- waves. 

For very high frequencies the dimensions of the vibrators become 
very small; hence some difficulty is experienced in preparing them. 
As the frequency depends directly upon the square root of the 




HIGH FREQUENCY TOURMALINE CUT 

FIG. 6. (upper) Crystal struc- 
ture of tourmaline. 

FIG. 7. (lower) Application of 
electrodes to high-frequency tour- 
maline plates. 



192 



F. R. LACK 



[J. S. M. p. E. 



modulus of elasticity and inversely upon the dimensions, the latter 
can be increased for a given frequency if, by some means (choice 
of orientation of axes, or different type of crystal), the elasticity 
can be increased. It so happens that in tourmaline the modulus of 
elasticity along the Z axis is approximately twice that along the X 
axis in quartz. Hence, for ultra-high frequencies (10 megacycles 
and above) plates are sometimes cut from tourmaline with the major 
face perpendicular to the Z axis. The electrodes are applied as 
shown in Fig. 7 and the longitudinal vibration in the Z direction 




FIG. 8. Crystal frequency generator with cover re- 
moved, showing crystal holder and oven for controlling 
temperature. 

utilized. The thickness of such a plate for a given frequency is 
approximately 40 per cent greater than that of a corresponding 
quartz plate, which is a real advantage when the plates are only a 
few thousandths of an inch thick. 

Using one of these types of vibration, it is possible to construct a 
frequency generator consisting of a piece of quartz or tourmaline, 
a vacuum tube, and a few simple electrical circuit elements. If 
carefully mounted in a temperature-controlled compartment, such a 



Oct., 1934] 



PIEZOELECTRIC CONTROL 



193 



generator would have a high degree of precision. The Bell System 
frequency standard is of such a form. 3 The crystal is of quartz, 
and the frequency of vibration is 100,000 cycles per second. A 
precision of the order of 1 part in 10,000,000 is attained; or, in terms 
of time-keeping, it never deviates more than Viooth of a second in a 
day. 

The standard frequency generator has many uses: it is supplied 
to the telephone operating companies and is used by them to cali- 
brate the carrier frequencies of their wire and radio communication 
circuits; it is supplied to electric power companies who use it to set 



11111 




FIG. 9. Cross-sectional view of crystal holder and oven 
system of crystal frequency generator: ( 1 ) quartz crystal 
plate forming vibrating system; (2) electrodes; (3) and 
(4) details of crystal holder; (5) heat filter to prevent 
thermal cycle of thermostat and heater from reaching 
crystal; (6) thermostat; (8) electric heater controlled by 
thermostat; (10) external casing of oven. 



the frequency of generators of electric power; to watchmakers who 
use it to regulate watches; to broadcast stations when it is necessary 
to control the frequency of two stations from a single source; etc. 
For maintaining the frequency of radio stations, fixed or mobile, to 
their assigned values within very close limits, the piezoelectric gen- 
erators can be made in very compact form. Figs. 8 and 9 show 
the details of such a generator capable of a precision of 1 part in 
100,000 ; or, in terms of time-keeping, better than one second a day. 



194 F. R. LACK [j. s. M. p. E. 

In addition, the piezoelectric crystal finds many other applications. 
Rochelle salt crystals are used as loud speakers, microphones, phono- 
graph pick-ups, 4 and oscillographs. As they can be made to vibrate 
mechanically, they can be used as sources of sound. Sound waves 
so generated can be used for submarine communication between 
ships, marine depth finding, etc. If generated with sufficient in- 
tensity the waves are capable of breaking up the cell structure of 
living organisms. One practical application has been made of this 
fact in a device for pasteurizing milk by supersonic sound waves 
generated by a quartz crystal. The complete list of applications of 
the piezoelectric crystal is a long one and is being rapidly enlarged as 
the capabilities of the device become more generally known. 

REFERENCES 

1 CURIE, P. AND J.: "Hemihedral Crystals," Comptes Rendus, 01 (1880), pp. 
294, 383, 387. 

2 VOIGT, W. : Lehrbuch der Kristallphysik ( 1928) . 

3 HARRISON, W. A.: "A High-Precision Standard of Frequency," Bell Syst. 
Tech. J., 8 (July, 1929), No. 3, p. 493. 

4 NICHOLSON, A. M.: "The Piezoelectric Effect in the Composite Rochelle 
Salt Crystal," Proc. A.I.E.E., 38 (Nov., 1919), No. 11, p. 1315. 

BALLANTINE, S. : "High-Quality Radio Broadcast Transmission and Re- 
ception," Proc. I. R. E., 22 (May, 1934), No. 5, p. 564. 

WILLIAMS, A. L.: "Piezoelectric Loud Speakers and Microphones," Elec- 
tronics, 4 (May, 1932), No. 5, p. 166. 

WILLIAMS, A. L.: "Piezoelectric Microphones," J. Soc. Mot. Pict. Eng. 
XXIII (Oct., 1934), No. 4, p. 196. 

DISCUSSION 

MR. CRABTREE: Perhaps Mr. Lack might explain a little more clearly exactly 
how the crystal acts as a timekeeper. 

MR. LACK: A frequency generator, with an integrating device for counting 
the number of vibrations, can be used as a timekeeper. 

MR. CRABTREE: If the vibrations are of the order of, say, ten million per 
second, how are they integrated? 

MR. LACK: Just as 35-mm. film is reduced to 16-mm. film or vice versa, so 
frequencies can be stepped up or down at will. In the Bell System standard, 
which operates at 100,000 cycles, the frequency is stepped down successively to 
10,000 cycles, 1000 cycles, and 100 cycles. At 100 cycles or less a syn- 
chronous motor can be driven, with which, by means of a revolution counter, the 
number of vibrations over a 24-hour period can be integrated. Checking 
the 24-hour period against the astronomical time from Washington, the fre- 
quency standard forms an interpolating device which will accurately break up the 
period of rotation of the earth into hours, minutes, and seconds. 



Oct., 1934] PIEZOELECTRIC CONTROL 195 

MR. ROSENBERGER: Can the crystals be used to control the frequency of slow- 
motion pictures? 

MR. LACK: Yes, but I fail to see why such a high order of precision is neces- 
sary. Eventually it is hoped that power companies will tie in their 60-cycle power 
with some form of frequency standard. That is being attempted at the present 
time with some success. I should think that the 60-cycle source would provide a 
more convenient means of getting an accurate speed than by using a crystal, 
stepping it down to the low frequency and amplifying it sufficiently to operate the 
motor. If the 60-cycle power is unsatisfactory for some reason or other, and a 
local frequency standard must be used, a tuning-fork would appear to be more 

litable for the purpose than a crystal, on account of the low frequency. 

MR. CRABTREE : How do the broadcasting stations control their frequencies by 
using this crystal. 

MR. LACK: A specific crystal is supplied to each broadcasting station, which 
serves as a fundamental frequency generator and determines whether the radiated 
frequency will be, say, 495 kilocycles or 496. 

MR. CRABTREE : How is the crystal calibrated? 

MR. LACK: The frequency depends upon the dimensions and elasticity of the 
crystal. The size of the crystal, for a given frequency, can be predicted, and the 
crystal is ground to that size. 

MR. CRABTREE: Is it like grinding a lens in the early days; by trial and 
error? 

MR. LACK: No; crystals can be ground to within a few hundred cycles by 
machine and micrometer entirely. The final calibration is done by hand. 

MR. CARPENTER: How are the raw crystals selected? 

MR. LACK: If one can assure himself that the quartz is free from such defects 
as twinning, bubbles, cracks, and so forth, it can be assumed that the performance 
of the crystals is predictable. 

To eliminate the defects, careful examination of the raw material is necessary. 
With experience, one can predict pretty well just how much twin material will 
be found in a given crystal when it is cut, from the external markings on the 
natural crystal surface. 

As for the bubbles and cracks, a high-intensity arc can be used to look into the 
raw crystal, which usually has a number of faces clear enough for the purpose. 

MR. TUTTLE: What is the order of the temperature effect upon the frequency 
of a given piece of quartz? 

MR. LACK: Inasmuch as frequency depends upon the elasticity along the 
axis of vibration, it depends upon the type of vibration. Crystals can be pro- 
duced having a temperature coefficient less than one part in a million, per degree 
centigrade. The average commercial crystal will have a higher coefficient than 
that. The maximum is around 100 cycles per million per degree of centigrade. 



PIEZOELECTRIC MICROPHONES* 

A. L. WILLIAMS** 

Summary The development of the Rochelle salt crystal microphone, with particu- 
lar reference to the grille and sound-cell type, is described; and the construction of the 
sound-cells and the method employed for rendering them air-tight and water-proof 
are explained. Due to the small size of the microphones they are relatively free from 
distortion arising from cavity resonance, diffraction, and phase-shift, and are non- 
directional. 

Comparative response curves ranging in frequency from 50 to 10.000 cycles per 
second are presented. Special types of piezoelectric microphones for sound picture 
recording, radio broadcasting, and theater sound-reenforcing systems are described. 
Some of their physical, electrical, and acoustical characteristics are discussed, in- 
cluding those of a new unidirectional instrument. 

Due to the increasing use of piezoelectric microphones in the 
various fields concerned with the measurement, recording, and re- 
production of sound, and as their commercial development is com- 
paratively new, it is the object of this paper to outline briefly the 
history of piezoelectricity, particularly as manifested in homogeneous 
crystals of Rochelle salt, and to discuss the design and construction 
of microphones based on this principle. 

Piezoelectricity, or pressure electricity, is said to have been known 
to Coulomb, as early as 1780, who discovered that certain substances, 
when subjected to pressure, exhibited an electrical charge upon 
opposing surfaces. Later work by Becquerel, 1 about 1833, led to his 
report of the measurement of this effect in various substances. He 
investigated a large number of substances and was disappointed 
when he found that oranges lost their piezoelectric effect upon drying. 

In 1880, the Curies, 2 studying the relationship between piezo- 
electricity and pyroelectricity, published the results of their work 
with quartz and other substances in which they determined the 
voltage generated by unit pressure along various crystallographic 
axes. They derived the "law" that the potential generated was pro- 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Brush Development Co., Cleveland, Ohio. 

196 



PIEZOELECTRIC MICROPHONES 197 

portional to the pressure, and determined the piezoelectric constants 
of about thirty materials. 

This work of the Curies is the important phase of the early work 
in piezoelectricity from the point of view of present-day microphone 
developments. It is interesting to note that very soon the Curies 
were able to show that if a substance produced a voltage under 
pressure, then, in accordance with the law of the conservation of 
energy, the converse was likewise true that an applied voltage 
produced a distortion in the same substance. 

Rochelle salt crystal, however, was recognized to be superior in 
piezoelectric effect to any other crystal known, 3>4>5 and was found 
to have a piezoelectric constant more than 1000 times as great as that 
of quartz (Table I). 

TABLE I 

Piezoelectric Constants 

, e. s. u. per sq. cm. 

Substance d = 

dynes per sq. cm. 

Tourmaline +5.78 X 10 ~ 8 

Quartz -6.94 X 10 ~ 8 

Rochelle salt at 20C. +8100 X 10 ~ 8 

That might have made Rochelle salt extremely interesting, except 
for the facts that clear homogeneous crystals of useful size were not 
available, and Rochelle salt was regarded as too weak and imper- 
manent. Moreover, there was a general lack of appreciation of the 
sensitiveness of clear crystals of Rochelle salt. In 1919, Nicolson 
published results achieved by using rapidly grown composite Rochelle 
salt crystals. The entire crystal was utilized, and the unhomogeneous 
portion apparently played a part in the effect attained. 6 

It is not necessary to discuss the years of work that were involved 
in developing a process of making useful Rochelle salt crystals and 
methods of fabricating them. Suffice it to say that, to the far-seeing, 
commercial opportunities were present, if only such processes and 
methods could be developed. Moreover, crude Rochelle salt was 
produced as a by-product in manufacturing warming wines, and its 
availability was not dependent upon natural crystalline deposits 
in the earth. 

Theoretical and practical experimentation with crystal blocks and 
slabs of Rochelle salt brought to light serious difficulties in applying 
the material commercially (Valasek, Isley, Frayne, etc.). Outstand- 
ing among the difficulties were saturation and hysteresis, wide varia- 



198 



A. L. WILLIAMS 



[J. S. M. p. E. 



tions in the piezoelectric performance of the crystal at different 
temperatures, and different crystals produced different results at 
identical temperatures. 

It has been shown by C. B. Sawyer 7 that when two plates of Ro- 
chelle salt crystal, with electrodes attached, are cemented together 
in a suitable manner, if a voltage is applied to the electrodes one 
plate will tend to expand and the other to contract, causing a bending 
of the whole unit in a manner similar to a bimetallic thermostat. 
Saturation and hysteresis almost completely disappear and the 
temperature effect is considerably reduced. Such a combination is 
nicknamed a "bimorph" element, and may operate either by bending 




FIG. 1. The three axes of a homogeneous Rochelle 
salt crystal. 

or by twisting, according as the construction employs "bending 
elements" or "torque elements." 

Fig. 1 shows the a, b, and c axes of a homogeneous Rochelle salt 
crystal. Long crystalline plates of Rochelle salt cut perpendicularly 
to the a axis and with edges 45 degrees to the c axis, expand and con- 
tract longitudinally in response to varying applied electric potentials. 
Consequently, a bimorph element consisting of two such plates 
cemented together and provided with appropriate electrodes will, 
when held at one end and electrically charged, bend and move 
perpendicularly to its major surfaces and parallel to the a axis. 
Conversely, when mechanically deformed in such a manner, a differ- 



Oct., 19341 



PIEZOELECTRIC MICROPHONES 



199 



ence of potential will be produced between the electrodes. It is 
evident that a substance that is capable of reproducing in motion 
variations of electrical potential applied to it, and, conversely, of 
reproducing in voltage variations mechanical distortion to which it is 
subjected, should prove immediately applicable in the field of acous- 
tical reproduction, particularly in loud speakers, phonograph pick- 
ups, and microphones. 

In practice, a special bimorph element is frequently employed, 
in which a double curvature of the element is produced and utilized. 
Such double curvature is easily attained with Rochelle salt in conse- 
quence of the fact that, when the 45-degree diagonal of a plate cut 
perpendicularly to the a axis expands, the other diagonal, 90 degrees 
from the first, contracts. Consequently, and for example, a wider 
bimorph element composed of two rectangular Rochelle salt plates 
will, upon being electrified, assume a double curvature. If the curva- 
ture along the 45-degree diagonal at any time is convex, the curvature 
along the complementary diagonal is concave. When such a wide 
bimorph element, in an electrically neutral condition, is supported at 
the centers of two opposite edges and pressure is applied over the 
whole of one of the broad surfaces, this double distortion will 
result, and a voltage will be generated in proportion to the magni- 
tude of the distortion. 

Before leaving the specific discussion of Rochelle salt crystal 
and crystal elements, attention should be called to the success that 
has attended our efforts to overcome effects of excessive temperature 
and humidity upon the crystal microphone. Though Rochelle salt 
crystal is certainly soluble in water, it is also as certain that neither 
water nor water vapor can dissolve crystal that it can not touch. 
Various water-proofed papers, waxes, etc., provide insulation against 
moisture to such an extent that a microphone is not rendered in- 
operative even after hours of total immersion in water. Moreover, 
although Rochelle salt melts at 165F., and becomes inoperative 
if maintained at a temperature of 131F. for a considerable period 
of time, experience has proved that those limitations do not interfere 
with its use. 

Valasek 8 has shown that in Rochelle salt crystal there is a very 
interesting value of temperature (22 C., or 72 F.) known as the 
Curie point, at which the piezoelectric effect is greatest, indicating 
that the piezoelectric "constant" of Rochelle salt varies greatly with 
the temperature. The bimorph construction, however, assisted by 



200 A. L. WILLIAMS [j. S. M. P. E. 

using very thin sections of the crystal, has so reduced the tem- 
perature effect that tests have shown a microphone to vary only 
2 db. in a range from 40 below zero to 120 above zero Fahren- 
heit. The decrease in the temperature effect resulting from the 
bimorph construction has been pointed out by Ballantine 9 in con- 
nection with the much thicker sections used in loud speakers. 

Crystal Microphones. The more conventional type of crystal 
microphone, in which the energy absorbed by a separate diaphragm 
is converted into electricity by means of a suitable crystal unit, 
presents variations in design and construction that are nearly un- 
limited, but such designs may be divided into two main classes: 
the first, in which the diaphragm is rigidly connected to the crystal ; 
and the second, in which the diaphragm exerts a varying pressure 
upon the crystal unit through a resilient intermediate member. 

In the former case, the mass and elasticity (restoring force) of the 
diaphragm and crystal must be considered together when calculating 
the natural period and mechanical impedance of the assembly. 
A fairly flexible bending bimorph unit is now being used, which 
is supported at one end, the other end being attached to the center 
of a flexibly mounted, stiff diaphragm. In the commercial model, 
illustrated in Fig. 2, the diaphragm is of formed duralumin. 

If a resilient coupling is used between the diaphragm and the 
crystal unit, the crystal can, without loss of efficiency, be considerably 
stiff er, thus having a higher natural period than the diaphragm. 
The final acoustical characteristic of such an instrument will depend 
upon the judicious selection of the various variables, sometimes with 
the assistance of damping applied at the proper place. 

To reduce the number of parts, it is possible to make the diaphragm 
itself out of crystal. One way in which to do that is to attach the 
electrodes to a Rochelle salt bimorph disk in four sections, in such a 
way that pressure at the center of the diaphragm will produce 
a voltage on each quadrant. When suitably supported in a case, a 
lV2-inch disk, 0.020 inch thick, makes a good average microphone 
when a fraction of the output is sacrificed in the interest of reducing 
mechanical resonance and improving fidelity. Such a unit, however, 
still retains its point of resonance within the musical range and 
suffers from pressure doubling due to reflection. It is not regarded 
satisfactory from the laboratory view-point, although it was marketed 
commercially and a number of them were very successfully used. 

Spherical Microphones. To avoid those defects, a spherical 



Oct., 1934] 



PIEZOELECTRIC MICROPHONES 



201 



microphone was developed, having a band of rectangular crystal 
diaphragms on its equator, each crystal of such size that its natural 
period was above the range for which it was designed. If the works 
of Rayleigh, 10 Stewart, 11 and Ballantine 12 are studied, it will be seen 
that such a band on the surface of a sphere 3 inches in diameter shows 
very little frequency discrimination. However, this type was never 
introduced commercially because of the superior theoretical and 
practical advantages of the sound-cell. 

Sound-Cell and Grille Type Microphones. Fig. 3 shows the con- 
struction of the piezoelectric sound-cell. It consists of a rectangular 
frame, usually of bakelite, in each side of which is supported a thin 
Rochelle salt crystal bimorph unit. The crystals are supported by 





FIG. 2. (Upper] Diaphragm type crystal 
microphone. 

FIG. 3. (Lower} Section through piezoelectric 
sound-cell (four times actual size). 



the frame at two points, and a clearance is provided between the frame 
and the crystal sealed by a flexible, air-tight annulus, thus leaving 
the crystal free to be distorted by variations of pressure. Silver leads 
are brought out from the crystals at the point of support and are 
usually connected in parallel. The whole cell is then impregnated 
with wax at 140 F., in order to render it air-tight and moisture- 
proof. The result is a small, flat, hollow, air-tight box, the two major 
sides of which generate voltage in proportion to the pressure, the 
voltage generated by one side being in phase with that of the other 
when caused by sound, and out of phase when caused by mechanical 
shock or vibration. 

One of the major considerations governing the size of an indi- 
vidual sound-cell is that the mechanical resonance of the crystal 



202 A. L. WILLIAMS [J. S. M. p. E. 

units should be above the highest frequency to be reproduced, an 
objective that must be attained without sacrificing much sensitivity. 
In present commercial sound-cells, the crystal units are 7 /ie inch 
square and 0.020 to 0.030 inch thick over-all, which means that the 
two separate slabs composing the bimorph unit, without their elec- 
trodes, are about 0.006 inch thick. The units are designed to resonate 
just over 10,000 cycles per second, causing the characteristic to rise 
at the upper end. This increased output is usually found useful 
in compensating for high-frequency loss in associated equipment, but 
may easily be compensated for in the amplifier. 

The second consideration governing the size is that the dimension 
of the sound-cell in any direction should be considerably smaller 
than the shortest sound-wave to be reproduced. Consider a plane 
wave normally incident to a major surface of the unit: it has been 
shown by Rayleigh that an increase of pressure will occur due to re- 
flection when the length of the sound-wave approaches the size of 
the unit. When considering the effect, it must be remembered that 
the whole area of the sound-cell, including the frame, must be taken 
into account, as the frame acts as a baffle. For general purposes, 
the cell utilizing the 7 /i 6 -inch square crystal, already mentioned, is 
3 / 4 inch square over-all. 

H. C. Harrison and P. B. Flanders 13 have computed the diffraction 
from Ballantine's equation, 12 and the result is shown in Fig. 4 for 
sound approaching at angles of zero and 90 degrees to the surface. 
Actually, the curves shown are computed for a rigid sphere, but they 
may be regarded as sufficiently close approximations for showing 
that, even for a microphone as small as 3 /4 inch square, the distortion 
resulting from diffraction will be very appreciable at high frequencies 
for sound-waves approaching from a direction normal to the surface ; 
but small for waves 90 degrees from the normal. For that very important 
reason the cells are mounted edgewise; and, where a number are 
mounted in a single case, in the form of a grille. 

In a larger microphone, the use of the instrument at the 90-degree 
angle to the source introduces another serious form of distortion, 
due to phase-shift. Fig. 5, also due to Harrison and Flanders, 13 
shows the loss of response at the high frequencies from that cause 
up to a frequency of 10,000 cycles for a sound-cell whose active sur- 
face is 7 /ie inch, and for a lV 2 -inch diaphragm, which is a common 
size for commercial carbon, condenser, and dynamic microphones. 
It will be seen that the effect due to phase-shift tends somewhat to 



(vi. f 



PIEZOELECTRIC MICROPHONES 



203 



cancel that due to diffraction and that the total error from the two 
causes is small. 

As mentioned before, the voltage output of a sound-cell will 
increase at the resonance frequency of the crystal element. In a 
sound-cell employing crystals 7 /ie inch square by 0.030 inch thick, 



ETLATIVE RESPONSE IN DB 

i\s o r -W 


































- 


n 








n 















= ^ 


y 
* Z. 











3 


O 




a 













/ 




^ 






















^ 


/ 




e 


<c 


\* 































































too 



jooo 

IN CVCLES PER SECOND 



10000 



Ill 

r< 
?. 



a 



" 



> 

P - 



( |OO IOOO IOOOO 

FREQUENCY \N CYCLED PE/? SECOND 

FIG. 4. (Upper) Effect due to diffraction in a 3 / 4 -inch square 
sound-cell. 

FIG. 5. (Lower) Effect due to phase-shift when the sound ap- 
proaches from a direction in the plane of the sensitive surface, for 
a standard sound-cell and for a lV2-inch diaphragm. 

the increase in the output will amount to about 2 db. at 10,000 cycles. 
When two or more sound-cells are connected in series, the effect will 
increase proportionately, whereas a parallel connection will cause it to 
decrease. Fig. 6 shows a conventional resistance-capacity coupled 
amplifier suitable for use with such a microphone, in which is indi- 
cated, at X, a condenser in the grid circuit of the second tube, ar- 



204 



A. L. WILLIAMS 



[J. S. M. P. E. 



ranged to compensate for the increase in output at the high fre- 
quencies. 

In the commercial grille microphones, in order that the impedance 
may be low enough to permit using a reasonable length of cable 
between the microphone and the amplifier, enough cells are connected 
in parallel to make it unnecessary, in most cases, to employ special 
compensation. 

For use as laboratory standards, sound-cells as small as one- 
half the usual size have been made. In a typical example of such a 
unit, the bimorph crystals are 7 /32 inch square by 0.010 inch thick, 
and are designed to resonate above 20,000 cycles. 

Electrical Characteristics. In the usual commercial sound-cell, 




FIG. 6. 



Conventional resistance-capacity coupled amplifier circuit, 
suitable for use with the sound-cell. 



the two bimorph crystal units are connected in parallel in such a 
way that when strained by mechanical shock the respective outputs 
tend to cancel, but when strained by pressure due to a sound-wave, 
the outputs are additive. Such a construction has the very practical 
advantage of allowing the unit to be handled during operation 
without having to use elaborate methods of suspension, and renders 
it remarkably quiet in a wind. 

The electrical impedance of a sound-cell below its point of me- 
chanical resonance may be represented by a capacity of about 
0.003 microfarad in series with a small resistance. A single sound- 
cell has an output of approximately 0.125 millivolt per bar. As the 
impedance is almost always capacitive, little frequency discrimina- 
tion due to the capacity of the leads between the microphone and the 



Oct., 1934] 



PIEZOELECTRIC MICROPHONES 



205 



grid of a tube is noticeable, although such capacity will reduce 
the useful available voltage. It is not, therefore, necessary to use a 
transformer to step down the output voltage in order to eliminate the 
effects due to the capacity of the cable; and owing to the frequency 
differentiation between the cable capacitance and the leakage re- 
actance of the transformer, it is generally undesirable to do so. 

It will be seen from the foregoing that a sound-cell 
is a complete but very small microphone, requiring 
neither polarizing voltage nor exciting current. It is 
entirely a pressure-operated device; and as piezoelec- 
tricity (as its name implies) is a pressure, and not a ve- 
locity phenomenon, there is no low-frequency cut-off. 
On open circuit, a sound-cell can respond as well at 1 
cycle as at 1000. The cell is so small that it is almost 
free from distortion due to cavity resonance, phase- 
shift, or diffraction. It is non-directional in the plane 
of its major surface. The limitation in the output of 
the single sound-cell is overcome by using a number of 
cells to the microphone, from four to twenty-four, con- 
nected in series-parallel when long leads are to be used, 
or simply in series when the microphone is situated 
near the amplifier tube. 

Fig. 7 illustrates a type G-4S6P grille type micro- 
phone containing twenty-four cells. 

A sound-cell, being only l / 8 inch thick, may be 
mounted close enough to a large reflecting surface 
to avoid audible frequency discrimination caused by 
a train of waves meeting their own reflection. The 
practical result, in such a case, is an increase in output 
to a value double that of the output of the same unit 
in free air. Advantage has been taken of that fact 
in designing the L-2S2P, T-2S4P microphones, and, 
to a certain extent, in the D-2S2P microphone. The 
first is a small, flat unit containing four standard cells, 
connected two in series and two in parallel, mounted Vie inch from 
the back of the case. It may be placed upon a table, wall, or floor, 
as when it is required to conceal the microphone in motion picture 
recording. It may also be used as a lapel microphone. 

The T-2S4P (Fig. 8) has twice as many cells in parallel, so that two 
or three may be connected in series without permitting the impedance 



FIG. 7. 
TypeG-4S6P 
microphone. 



206 A. L. WILLIAMS [J. S. M. p. E. 

and the consequent loss of voltage in the leads to become too great. 
The cells are similarly mounted in a cast metal case, primarily de- 
signed for installation near the front of a stage for sound reenforce- 
ment, and are also useful in churches, mounted on the pulpit, for 
example. When used on the stage, they may be spaced 10 feet apart 
along the footlights; four will comfortably cover a 60-ft. stage, 
allowing 15 feet at each end, although in the installation in the Roxy 
Theater at New York, four are successfully used to cover an 85-ft. 
stage. 

To fill the demand of the motion picture industry and others for 




FIG. 8. Type T-2S4P microphone for theatrical sound re- 
enforcement. 

a more completely directional microphone, considerable work has 
been done by the Brush Development Company toward producing 
a unit in which the output of some of the sound-cells in the micro- 
phone is shifted in phase by means of resistances and condensers, 
so that a sound-wave coming from one direction will produce an 
additive effect, and one coming from the opposite direction will 
produce a subtractive effect on the output of the remainder of the 
sound-cells over a comparatively wide frequency range. 

Performance. The curves of Fig. 9, due to Ballantine, 14 show the 
free-space calibration of three of these microphones; and those of 
Fig. 10, of five other commercial types. The dotted curve of Fig. 9 



Oct., 1934] 



PIEZOELECTRIC MICROPHONES 



207 



shows the increase of output at high frequencies due to mechanical 
resonance when four cells are used in series without compensation. 



BRC CRYSTAL MICROPHONE 
TYPE IOOA 



a 

4 

a -8 

















| 


Ml 1 


1 








.' 








WAVE 


RESPONSE 


OF 


THREE INSTRUMEf 


OS 


















































H^ .__;__ 


_ 


.... 











"Z. > 















































3RIZONT/S 


L 




























INCIDENCE ~ 


































1 1 1 

















50 



100 



1000 
FREQUENCY 



10000 



20 




















































































































*ESPON< 
AZIMUTH 


E 














>*-~ 
































^ 


w ' 






10 




















zz. 




"V 






r 
























,s / 




































^ / '" 


--'" 


X N 






v,^ 




























S"~ s' 


\ 




\ 




^ 














f- 


\ 


' 




^ 


^' 


J N 





s. 


/ 


\ 


RESPON! 
5 




























































7 OR 600A 
3.94 

: ee* 


x ^ 








- RCA-VICT03 


" CONDENSER TYPE 
i WO'. iNC-CO:L TYP 
CONDE.NSER TYPE 4* 
VELOCITY TYPE 44A 
1 
















3 








4 








5 




























| 


I 








_L 



50 100 1000 10000 


FREQUENCY 




z 5 




113' 








































v x 


RE3PON5E 

^ o 




B. 


ae, 


k 




_Mk^: 


=i 







b= 


i. 


b. 








^=_=i 


s^ 


j 


ri 


- ^ 


'**' 






































O IOO 1OOO lOdOO 

FREQUENCY IN CYCLES PER SECOND 



FIG. 9. (Upper} Free-space calibration of three sound-cell 
microphones. 

FIG. 10. (Center) Free-space calibration of five other commercial 

types. 

FIG. 11. (Lower] Effect of temperature upon a standard 4-cell 
microphone (type G-2S2P). 

Fig. 11 shows the effect of temperature upon a standard four-cell 
icrophone (type G-2S2P), which employs bimorph elements 
.020 inch thick. It may be expected that the use of 0.030-inch 



208 A. L. WILLIAMS [J. S. M. P. E. 

elements would not show a very much greater deviation from the 
normal. The upper curves were obtained by placing the microphone 
in a stream of hot air; the lower curve by cooling with "dry-ice." 
The temperature was measured by means of two thermometers in 
contact with the unit, and the output across a 5-megohm resistance 
was compared with that of a similar microphone at room temperature 
(65 F.). Less accurate cold tests made on the microphones for the 
Byrd Antarctic Expedition showed no further reduction of output 
above a temperature of 40 F., below which point the output fell 
off rapidly. 

REFERENCES 

1 BECQUEREL, A. E. : Annales de Chemie et de Physique, 22 (1833), p. 5. 

2 CURIE, J. AND P.: "Hemihedral Crystals," Compte Rendu, No. 91, pp. 294, 
383, 387. 

3 REICKE AND VOIGHT: Annalen der Physik und Chemie, 45 (1892), p. 523. 

4 CURIE, J. AND P. : "Traite de Radioactivite" (1908). 
6 VALASEK, J. : Phys. Rev., 20 (1922), p. 639. 

6 NICHOLSON, A. M.: "The Piezoelectric Effect in the Composite Rochelle 
Salt Crystal," Proc. A.I.E.E., 38 (Nov., 1919), No. 11, p. 1315. 

7 SAWYER, C. B.: "The Use of Rochelle Salt Crystals for Electrical Repro- 
ducers and Microphones," Proc. I. R. E., 19 (Nov., 1931), No. 11, p. 2020. 

8 VALASEK, J.: Phys. Rev., 19 (1922), p. 478. 

9 BALLANTINE, S.: "A Piezoelectric Loud Speaker for the Higher Audio 
Frequencies," Proc. I. R. E., 21 (Oct., 1933), No. 10, p. 1406. 

10 RAYLEIGH, LORD: "Theory of Sound," II, p. 274. 

11 STEWART, G. W. : Phys. Rev., 33 (1911), p. 467. 

12 BALLANTINE, S. : Phys. Rev., 32 (1928), p. 988. 

13 HARRISON, H. C., AND FLANDERS, P. B. : "An Efficient Miniature Condenser 
Microphone System," Bell Sys. Tech. J., II (July, 1932), No. 3, p. 451. 

14 BALLANTINE, S.: "High-Quality Radio Broadcast Transmission and Re- 
ception," Proc. I. R. E., 22 (May, 1934), No. 5, p. 589. 

DISCUSSION 

MR. KELLOGG : How is the crystal made so nearly independent of temperature. 
Also, how is the unidirectional effect achieved? 

MR. WILLIAMS: The temperature effect is largely annuled by the bimorph 
construction, in which two sections of crystal are put together in opposition. 
It appears that if the crystals are completely restrained from moving in the di- 
rection in which they tend to move, the temperature effect becomes negligible. 
In the bimorph construction, this restraint would not be perfect unless the 
crystals were infinitely thin. In other words, the thinner the unit, the better is 
the compensation. For example, in a quarter-inch thick bimorph, the fall-off 
due to temperature is very noticeable over 100 F. With a Vs-inch bimorph, 






Oct., 1934] 



PIEZOELECTRIC MICROPHONES 



209 



it is much less, and with one 0.0020 inch thick, as used in these microphones, it is 
almost negligible. 

As regards the uni-directional microphone, it is a matter of phase-shift in 
some of the cells. 

MR. TASKER: Is there any particular limit to the size to which Rochelle 
salt crystals can be grown? 

MR. WILLIAMS: No, but there are certain economical sizes. 

MR. CARPENTER: Is the performance uniform throughout the crystal? 

MR. WILLIAMS: Yes. 

MR. CRABTREE: If a voltage is applied to the crystal, what is the amplitude 
of vibration of the crystal? 

MR. WILLIAMS: That depends upon the voltage and the thickness of the 
crystal. In a piece 2 l / 2 inches square and a quarter-inch thick, made of four 
layers of crystal, it is about three-thousandths of an inch per hundred volts 
applied. As much as 300 volts can be applied. 

MR. CRABTREE: Are the loud speakers available commercially? 

MR. WILLIAMS: Yes. We are trying them out in quite large numbers- 
small compared with dynamic speakers, but up to 200 a week. 

MR. COFFMAN: Have any comparative measurements been made between 
the output of such a microphone as you have described and those of the more 
common types that have been used in the past, the velocity or the electrodyn'amic 
type of microphone? 

MR. WILLIAMS: As I mentioned in the paper, the output of a single standard 
sound-cell of the size described is Vs millivolt per bar. Two or four cells are 
usually used in series, making the output as great as J /2 millivolt per bar. That 
is lower than the dynamic microphone, which is about 9 millivolts per bar. I 
believe the velocity microphone is about 1 millivolt per bar. As the sound-cell 
is non-directional, the average pick-up of sound is much greater, which tends to 
produce a larger electrical output and is quite sufficient for use with standard 
amplifiers today. 



RECENT IMPROVEMENTS IN EQUIPMENT AND TECHNIC 
IN THE PRODUCTION OF MOTION PICTURES* 

E. A. WOLCOTT** 



Summary. Many improvements have been made in recent years in the equipment 
used in producing motion pictures. This paper describes some of the uses and 
advantages of the new equipment, and the problems involved in adapting it; and refers 
to the personnel of the sound crew, the use of velocity microphones, a new kind of 
visual amplitude indicator, the use of cloth and hard surfaces in set construction, 
the advantages of process projection, and the new silent Debrie motion picture camera. 

Sound engineers have realized for a long time that theater audiences 
are becoming increasingly critical of the quality of the sound in a 
motion picture. As a result, new refinements in sound recording 
and reproducing equipment have been found necessary; in par- 
ticular, recording and reproducing equipment for extending the fre- 
quency range. 1 ' 2 ' 3 

The application of the new sound recording equipment in making 
motion pictures demands considerable precision in operating the 
various devices, controls, etc., particularly in connection with the 
manipulation and placement of the velocity microphones 4 furnished 
with one system of extended frequency-range equipment. 

During the filming of a picture, the sound crew consists of the 
following members : 

(1) The first sound man, usually termed the "mixer" or "recordist." 

(2) The second sound man, or "stage man." 

(3) The third sound man, or "assistant." 

(4) The fourth sound man, also known as "stage electrician." 

The mixer is in charge of the sound crew, and is directly responsible 
for the quality and volume of the recorded sound. It is his duty also 
to see that harmonious relations exist at all times between the sound 
crew and the other members of the company producing the picture. 

The stage man operates the boom to which the microphone is 
attached. The work calls for considerable skill, particularly in 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** RKO Studios, Hollywood, Calif. 
210 



IMPROVEMENTS IN PICTURES 



211 



raking moving or dolly shots, and whenever the actors have occa- 
sion to move about the stage during dialog sequences. In some of 
the large studios in Hollywood he acts also as contact man between 

ic recordist and the director of the picture. 

The assistant has charge of the film recording machine, which is 
isually located in a permanent booth some distance from the mixing 
)th. His duties consist in loading the recorders, keeping a com- 
plete log or report of the operations of the sound crew throughout 
the day, and also aiding the recordist to keep a careful check on the 
ition of the anti-ground-noise device. 

The fourth sound man, or stage electrician, operates a starting 
panel on which are placed suitable controls for starting the cameras 
md recorders and placing the synchronizing marks upon the edges 
of the sound and picture negatives by means of an electrical marking 

rstem. He also aids the stage man in connecting the cables and 

ispending the microphones in the various requisite positions on the 

t. 

Extended frequency-range sound recording equipment is par- 
ticularly suitable for the velocity microphone, although the standard 
condenser type may be used. The directional properties of velocity 
microphones are very advantageous, particularly when it becomes 
necessary to pick up and record a dialog spoken in the midst 
of a large group of persons, such as in a mob scene. Another ad- 
vantage is the possibility of achieving what is known as "close-up 
quality" during the filming of a scene, using two or more cameras, 
one camera photographing a fairly long shot and the other a medium 
shot. Usually when the picture is edited, the medium shot is used 
for the greater part of the scene, and it is necessary to match the 
perspective of the sound to the closer camera as much as possible. 
In a recent feature picture,* this characteristic was very helpful, 
inasmuch as practically all the scenes consisted of medium and long 
shots, very few of them being close-ups. 

When using the velocity microphone, it is important that some 
means be provided to rotate it, so that it may always be directed 
toward the source of the sound. The device for rotating the con- 
denser microphones, as used in the past in practically all the major 
studios in Hollywood, is quite satisfactory for rotating the velocity 
microphones. However, due to the greater sensitivity of the ve- 

Frankie and Johnnie. 



212 E. A. WOLCOTT [J. S. M. P. E. 

locity microphone to transmitted shocks, or to vibrations generated 
in the boom that carries it, a new kind of suspension was required. 
A suspension developed by the RCA Victor Company consists of an 
inverted metal yoke to which the microphone unit is attached by 
means of a 4-point rubber suspension. It possesses excellent qualities 
as a mechanical filter, and is quite satisfactory for all practical 
purposes. When using the velocity microphone in motion picture 
work, it is very important that the operator of the microphone 
boom be very adept in manipulating it. He must remember the 
actors' cues so that the microphone may always be aimed at the 
person speaking. If the source of sound is outside the beam or area of 
sensitive coverage, a considerable loss of volume will occur, although 
no great change of quality will be noticed. 

Recently, the directional properties of velocity microphones 
have been utilized to control the brilliance, or the reverberant energy 
"pick-up," in a room in which orchestral recordings are made. 
For such purpose, two microphones are used; one is aimed at the 
orchestra in the usual manner, and the other is so placed as to pick 
up the reverberant energy. The output of each microphone is fed 
into separate positions on the mixing panel, and the gain of each 
adjusted to afford the proper "life" or brilliance to the recording. 

Occasionally, the directional characteristic of the velocity micro- 
phones becomes a slight handicap, particularly in a close-up shot, 
when the director wishes to include the lines of an actor not in the 
scene being photographed. Such a difficulty is solved by using an 
additional microphone, so placed as to provide the proper volume 
and quality for the off-stage voice. 

Another recent development is the device known as the visual 
amplitude indicator, which makes use of a series of small neon glow 
lamps arranged on a panel attached to the mixing panel and im- 
mediately above it. The voltages necessary to operate the lamps 
are obtained from an additional amplifier which utilizes a small 
part of the output signal of the standard recording amplifier. Sixteen 
glow lamps are suitably arranged to indicate a total volume range of 
53 decibels. A gain control is incorporated in the additional ampli- 
fier in order that the amplitude indication of the instrument may be 
adjusted to correspond to the amplitude of the sound track. 

The uses of the amplitude indicator are quite varied. It is par- 
ticularly adaptable to motion picture sound recording and broad- 
casting. It is also very useful for restricting the volume range of 



Oct., 1934] IMPROVEMENTS IN PICTURES 213 

large symphony orchestras within certain required limits. The 
calibration of the instrument was checked several times a day over a 
period of several weeks of motion picture production, and the maxi- 
mum deviation from the original calibration was not more than 
*V,db. 

Another important factor in recent years that has contributed 
considerably to the improvement in sound recording, is the use of 
sets made of cloth. Cloth of the proper color, conforming to the 
specifications of the art director, is stretched over wooden frames, 
care being taken to brace the frames securely when they are placed in 
position, particularly those sections adjacent to doorways in the 
scene. As the cloth used for the purpose is of a fairly thin texture, 
it is necessary to cover the back of each frame with black cloth, so 
as to prevent any light from shining through. This type of set 
construction is particularly satisfactory for scenes of small rooms, 
in which hard walls would impart a very disagreeable booming 
quality to the recording. It is still common practice, however, to 
use hard walls for very large sets, such as ballrooms, churches, theaters, 
etc., which is quite all right from a sound standpoint, as a fairly 
brilliant quality is necessary in order to produce the proper illusion. 
This is particularly true in recording music, in which case the bril- 
liance resulting from the reverberation often improves the final 
result. 

Process projection, 5 recently introduced in making motion pictures, 
has made it very simple to record many scenes which heretofore 
were practically impossible to record. For instance, dialog scenes 
in flying airplanes, speed boats, racing automobiles, and many 
others, can now be photographed on the sound stage, where the 
recording conditions are ideal. The real sound effects can be added 
later, thus lending a degree of reality to the scene heretofore un- 
attainable. Examples of what can be accomplished with the process 
are illustrated in several recent feature productions.* Process 
projection is comparatively simple; the essential requirements are a 
projector, a camera, and a suitable translucent screen. The camera 
and projector must be equipped with interlocking motors so that 
their respective shutters operate synchronously. A translucent 
screen developed for the purpose at the RKO Studios was found to be 
exceptionally well suited for this type of work. 

* Flying Down to Rio and King Kong. 



214 E. A. WOLCOTT 

Recently in New York, the new silent Debrie cameras 6 were used 
with extended frequency-range sound recording equipment in the 
regular production of motion pictures. The camera is self-contained, 
no silencing blimp being necessary. The camera is practically 
silent, and it is possible to record normal dialog with the camera at a 
distance of only three feet from the microphone, without introducing 
perceptible camera noise in the recording. It is light in weight, and is 
equipped with a base or tripod capable of adjustment to various 
camera heights. The base is also equipped with suitable mechanism 
so that it may be used for moving or dolly shots, and is adaptable to 
the standard Mole-Richardson camera dolly used in many of the 
major studios. 

REFERENCES 

1 DIMMICK, G. L., AND BELAR, H.: "Extension of the Frequency Range of 
Film Recording and Reproduction," /. Soc. Mot. Pict. Eng., XIX (Nov., 1932), 
No. 5, p. 401. 

2 ZIMMERMAN, A. G.: "Film Recorders," /. Soc. Mot. Pict. Eng., XX (March, 
1933), No. 3, p. 211. 

3 READ, S., JR.: "RCA Victor High-Fidelity Film Recording Equipment," 
J. Soc. Mot. Pict. Eng., XX (May, 1933), No. 5, p. 396. 

4 OLSON, H. F.: "The Ribbon Microphone," /. Soc. Mot. Pict. Eng., XVI 
(June, 1931), No. 6, p. 695. 

5 WALKER, V.: "Special Process Technic," /. Soc. Mot. Pict. Eng., XVIII 
(May, 1932), No. 5, p. 662. 

6 KOSSMAN, H. R.: "A Silent Camera," /. Soc. Mot. Pict. Eng., XXI (Nov., 
1933), No. 5, p. 420. 



LIST OF MEMBERS 



AALBERG, J. O. (M) 

157 S. Martel St., Los Angeles, Calif. 
ABRIBAT, M. (M) 

Kodak Pathe Research Labs., 30 Rue 
des Vignerons, Vincennes (Seine), 
France. 
ADAIR, S. E. (F) 

Jenkins & Adair, Inc., 3333 Belmont 

Ave., Chicago, 111. 
ADATTE, A. L. (A) 

Pathe Exchange, Inc., Bound Brook, 

N.J. 
AHLUWALIA, B. S. (M) 

RCA Victor Co., Inc., Camden, N. J. 
ALBIN, F. G. (A) 

United Artists Studio Corp., 1041 N. 

Formosa Ave., Hollywood, Calif. 
ALDERSON, R. G. (4) 

British International Pictures, Ltd., 

Elstree, Herts, England. 
ALEXANDER, D. M. (M) 

1830 Wood Ave., Colorado Springs, 

Colo. 
ALEXANDER, J. M. (A) 

Photo Sound Corp., 1075 Beaver 
Hall Hill, Montreal, P. Q., Canada. 
ALLER, J. (M) 

Consolidated Film Labs., 933 Seward 

St., Hollywood, Calif. 
AMES, M. H. (A) 

1343 Thayer Ave., Los Angeles, 

Calif. 
ANDERS, H. (4) 

Jam Handy Picture Service, 6227 

Broadway, Chicago, 111. 
ANDERSON, E. L. (4) 
U. S. S. Herbert # 160, 

% Postmaster, New York, N. Y. 

* (A) Associate Member 
(F) Fellow 

(H) Honorary Member 
(Af) Active Member 



ANDRES, L. J. (M) 

Automatic Musical Instrument Co., 
1500 Union Ave., S. E., Grand 
Rapids, Mich. 
ARAKI, J. K. (A) 

P. O. Box 513, Honolulu, Hawaii. 
ARMAD, V. (A) 

Famous Players Canadian Corp., 
Ltd., Capitol Theatre Bldg., Win- 
nipeg, Canada. 
ARMSTRONG, H. L. (A) 

Allentown, N. J. 
ARNSPIGER, V. C. (A) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
ASANO, S. (A) 

7-12 1 chome Feijimicho Koji- 

machiku, Tokyo, Japan. 
ATKINSON, S. C. (4) 

Regina Photo Supply, Ltd., 1924 

Rose St., Regina, Sask., Canada. 
AUGER, E. (A) 

RCA Victor Co., Inc., Camden, N. J. 
AVIL, G. (A) 

18500 Scarsdale Rd., Detroit, Mich. 



BADGLEY, F. C. (F) 

Canadian Govt. Motion Picture 

Bureau, Ottawa, Canada. 
BAIRD, H. (A) 

Shortwave & Television Corp., 70 

Brookline Ave., Boston, Mass. 
BAKER, G. W. (M) 

20 McEldowny St., Chicago Heights, 

111. 
BAKER, J. O. (M) 

RCA Victor Co., Inc., Camden, N. J. 
BAKER, R. J. (A) 

1911 Kalakaua Ave., Honolulu, 
Hawaii. 

215 



216 



LIST OF MEMBERS 



[J. S. M. P. E. 



BAKER, T. T. (A) 

The Hut, Hatch End, Middlesex, 

England. 
BAKER, W. R. G. (F) 

RCA Victor Co., Inc., Camden, N. J. 
BAKHSHI, M. N. (4) 

Block No. 97, Jermahal, Bombay, 2, 

India. 
BALDWIN, W. R. (A) 

2 Central Ave., East Newark, N. J. 
BALKAM, H. H. (A) 

Brooklyn Edison Co., 380 Pearl St., 

Brooklyn, N. Y. 
BALL, J. A. (F) 

Technicolor Motion Picture Corp., 
823 N. Seward St., Hollywood, 
Calif. 
BALTIMORE, D. M. (A) 

315 Washington St., Elmira, N. Y. 
BAMFORD, W. B. (A) 

614 Tenth Ave., Belmar, N. J. 
BANKS, C. (M} 

Regent Theater, Gisborne, New 

Zealand. 
BARBER, C. E. (A) 

ll l /-i N. Lee Ave., Oklahoma City, 

Oklahoma. 
BARKMAN, C. (A) 

Strand Theatre, Cumberland, Md. 
BARRELL, C. W. (F) 

Western Electric Co., 6 Grove St., 

New York, N. Y. 
BARROWS, T. C. (M) 

Metropolitan Theater, Boston, Mass. 
BARTH, A. (M) 

Carl Zeiss, Inc., 485 Fifth Ave., 

New York, N. Y. 
BARZEE, G. W. (A) 

Western Electric Co., Caixa Postal 
494, Sao Paulo, Brazil. 

BASS, C. (M) 

Bass Camera Co., 179 W. Madison 

St., Chicago, 111. 
BATSEL, C. N. (M) 

RCA Victor Co., Inc., Camden, N. J. 
BATSEL, M. C. (F) 

RCA Victor Co., Inc., Camden, N. J. 



BAUER, K. A. (A) 

Carl Zeiss, Inc., 485 Fifth Ave., New 

York, N. Y. 
BAUMANN, H. C. (A) 

829 Emerson Ave., Elizabeth, N. J. 
BEACH, F. G. (A) 

Room 511, 105 W. 40th St., New 

York, N. Y. 
BEAN, D. P. (A) 

The University of Chicago Press, 

5750 Ellis Ave., Chicago, 111. 
BECKER, A. (A) 

500 Pearl St., Buffalo, N. Y. 
BEERS, N. T. (M) 

420 Clinton Ave., Brooklyn, N. Y. 
BEETSON, F. W. (M) 

Associated Motion Picture Producers 
& Distributors of America, 5504 
Hollywood Blvd., Hollywood, 
Calif. 
BEGGS, E. W. (M} 

Westinghouse Lamp Co., Bloomfield, 

N.J. 
BEHR, H. D. (A) 

135-07 234th Place, Laurelton, Long 

Island, N. Y. 
BELL, A. E. (A) 

511 Bard Ave., West New Brighton, 

N. Y. 
BELL, D. T. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
BELTZ, W. H. (M) 

RCA Victor Co., Inc., 235 Mont- 
gomery St., San Francisco, Calif. 
BENDHEIM, E. McD. (A) 
21-24 31st St., Astoria, Long Island, 

N. Y. 
BENNETT, D. P. (M) 

581 Maywood Ave., Maywood, N. J. 
BENNETT, R. C. (10 

4327 Duncan Ave., St. Louis, Mo. 
BERG, B. (A) 

Fox Film Corp., 1401 N. Western 

Ave., Los Angeles, Calif. 
BERNDT, E. M. (M) 

112 E. 73rd St., New York, N. Y. 



)ct.. 1934] 



LIST OF MEMBERS 



217 



BERRY, R. C. (A) 

1148 E. 19th St., Brooklyn, N. Y. 
BERTIN, H. (M) 

79 Blvd. Haussmann, Paris, France. 
BETTS, W. H. (M) 

!Bell Telephone Labs., Inc., 463 West 
St., New York, N. Y. 
j BIDDY, R. (A} 

2995 Taylor St., Detroit, Mich. 
BIELICKE, W. F. (F) 
Astro-Gesellschaft m. b. h., Berlin- 
Neuckolln, Lahnstr. 30, Germany. 
BIELICKE, W. P. (M) 
405 N. Formosa Ave., Los Angeles, 

Calif. 
BISHOP, G. A., JR. (A) 

77 Conant Street, Fall River, Mass. 
BLAIR, G. A. (F) 

Eastman Kodak Co., 343 State St., 

Rochester, N. Y. 
BLAKE, E. E. (A) 
Kodak, Ltd., 63 Kingsway, W. C. 2, 

London, England. 
BLESSINGTON, E. (A) 

1618 Argyle St., Hollywood, Calif. 
BLINN, A. F. (A) 

5045 Franklin Ave., Hollywood, 

Calif. 
BLIVEN, J. E. (M) 

16 Waldo St., New London, Conn. 
BLOOMBERG, D. J. (M) 
RCA Victor Co., Inc., 411 Fifth Ave., 

New York, N. Y. 
BLOOMER, K. V. (A) 

Mount Kisco National Bank, Mount 

Kisco, N. Y. 
BLUMBERG, H. (4) 

National Theatre Supply Co., 1317 

Vine St., Philadelphia, Pa. 
BOEHM, H. (M) 

Lackierergasse 1, Vienna, IX, 

Austria. 
BOLTON, W. A. (A] 

205 Haines Ave., Barrington, N. J. 
BONN, L. A. (M) 
Chappaqua, N. Y. 



BORGESON, L. G. (A) 

680 Santa Barbara St., Pasadena, 

Calif. 
BOYLEN, J. C. (M) 

44 Thornhill Ave., Toronto, 9, On- 
tario, Canada. 
BRADFORD, A. J. (F) 

12110 Kentucky Ave., Detroit, Mich. 
BRADSHAW, A. E. (M) 

802 S. Ainsworth St., Tacoma, Wash. 
BRADSHAW, D. Y. (M} 
Fox Hearst Corp., 460 W. 54th St., 

New York, N. Y. 
BRADY, S. S. (4) 

Times Plaza Hotel, 510 Atlantic 

Ave., Brooklyn, N. Y. 
BRAGGIO, J. C. (A) 

Companhia Radio Internacional do 
Brasil, Caixa Postal 709, Rio de 
Janeiro, Brazil. 
BREITENSTEIN, S. (M) 

198 Johnson Ave., Teaneck, N. J. 
BRENKERT, K. (M) 

Brenkert Light Projection Co., 7348 

St. Aubin Ave., Detroit, Mich. 
BREWSTER, P. D. (F) 

Brewster Color Film Corp., 58 First 

St., Newark, N. J. 
BRIDGE, W. E. (A) 

1041 N. Formosa St., Hollywood, 

Calif. 
BROCK, G. F. O. (M) 

528 Riverside Dr., New York, N. Y. 
BROOKS, G. E. (4) 

Box 95, Longton, Kansas. 
BROWN, J. C. (M) 

704 S. Spring St., Los Angeles, Calif. 
BUCEK, H. (A) 

41 Schubertstr, Moedling, Austria. 
BUENO, P. G. (A) 

S. I. C. E., Apartado 990, Madrid, 

Spain. 
BUENSOD, A. G. (M) 

Carrier Engineering Corp., Chrysler 
Bldg., New York, N. Y. 

BURCHETT, C. W. (M} 

Box 491, San Francisco, Calif. 



218 



LIST OF MEMBERS 



IJ. vS. M. P. E. 



BUREL, L. H. (A) 

5 Rue Leon Coquiet, Paris, XVII, 

France. 
BURGUNDY, J. J. (A) 

2434 Prospect Ave., New York, N. Y. 
BURNAP, R. S. (70 

RCA Radiotron Co., Harrison, N. J. 
BURNAT, H. (A) 

70 Rue Lauriston, Paris, 16e, France. 
BURNETT, J. C. (F) 

Burnett-Timken Research Lab., Al- 
pine, N. J. 
BURNS, J. J. (A) 

3 Ridley St., Toronto, Ontario, 

Canada. 
BURNS, S. R. (F) 

International Projector Corp., 90 

Gold St., New York, N. Y. 
BUSCH, G. A. (If) 

76 Hillside Ave., Teaneck, N. J. 
BUSCH, H. (A) 

1306 S. Michigan Ave., Chicago, 111. 
BUSCH, L. N. (M) 

Kodak A. G., Friedrichshagenerstr. 

9, Berlin-Copenick, Germany. 
BUSSE, F. (F) 

I. G. Farbenindustrie, Kamerawerk, 
Tegernseerlandstr. 161, Muenchen, 
Germany. 
BUSSELL, E. J. (4) 

6342 W. 6th St., Los Angeles, Calif. 
BUTTOLPH, L. J. (F) 

General Electric Vapor Lamp Co., 

410 Eighth St., Hoboken, N. J. 
BYRUE, W. W. (A) 

2054 East 67th St., Brooklyn, N. Y. 

CABIROL, C. (M) 

Pathescope, Ltd., 5 Lisle St., Leices- 
ter Sq., London, W. C. 2, England. 
CAHILL, F. E., JR. (M) 
Warner Bros. Theaters, Inc., 321 W. 

44th St., New York, N. Y. 
CAMERON, J. R. ( F) 
Woodmont, Conn. 
CANADY, D. R. (M} 

19570 S. Sagamore Rd., Cleveland, 
Ohio. 



CANTOR, O. E. (4) 

98 Willington Hall St., Mattapan, 

Mass. 
CANTRELL, W. A. (A) 

503 East Prescot Rd., Knotty Ash, 

Liverpool, England. 
CAPSTAFF, J. G. (F) 

Research Labs., Eastman Kodak Co., 

Rochester, N. Y. 
CARLSON, F. E. (A) 

Eng. Dept., General Electric Co., 

Nela Park, Cleveland, Ohio. 
CARPENTER, A. W. (A) 

United Research Corp., 41-40 Har- 
old Ave., Long Island City, N. Y.; 
CARPENTER, E. S. (M) 

Escar Motion Picture Service, Inc., 
10008 Carnegie Ave., Cleveland, 
Ohio. 
CARSON, W. H. (F) 

The Barclay, 111 E. 48th St., New 

York, N. Y. 
CARTER, W. S. (A) 

381 Third Avenue, Ottawa, Canada. 
CARULLA, R. (M) 

1254 E. 31st St., Brooklyn, N. Y. 
CARVER, E. K. (F) 

Eastman Kodak Co., Kodak Park, 

Rochester, N. Y. 
CASTAGNARO, D. (A) 

1726 75th St., Brooklyn, N. Y. 
CECCARINI, O. O. (M) 

Metro-Goldwyn-Mayer Studios, Cul- 
ver City, Calif. 
CECCHI, U. (A) 

Cinemeccanica, S. A., Viale Cam- 
pania, 25, Milan, Italy. 
CERVENY, C. E. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
CHAMBERS, G. A. (M) 
Eastman Kodak Co., 6706 Santa 

Monica Blvd., Hollywood, Calif. 
CHANIER, G. L. (F) 
Old Short Hills Rd., Short Hills, 
N.J. 



t., 1934] 



CHAPMAN, A. B. (A) 

RCA Victor Co., Santa Fe Building, 

Dallas, Texas. 
CHAPMAN, C. T. (A) 

1212 Noyes St., Evanston, 111. 
CHARNEY, F. A. (M) 
8827 Woodhaven Blvd., Woodhaven, 

Long Island, N. Y. 
CHASE, L. W. (A) 

Eastman Kodak Company, 6706 
Santa Monica Blvd., Hollywood, 
Calif. 
! CHEFTEL, A. M. (M) 

22 Rue de Civry, Paris, XVII, 
France. 

CHRETIEN, H. (F) 

23 Rue Preschez, St. Cloud, France. 
CIFRE, J. S. (M) 

National Theater Supply Co., 211 

Columbus Ave., Boston, Mass. 
CLARK, L. E. (M) 
2327 Glendon Ave., West Los 

Angeles, Calif. 
CLARK, W. (/O 
Research Labs., Eastman Kodak Co., 

Rochester, N. Y. 
CLAYTON, J. (M) 
31-45 Tibbett Ave., Elmhurst, Long 

Island, N. Y. 
COHAN, E. K. (M) 

Columbia Broadcasting System, Inc., 
485 Madison Ave., New York, 
N. Y. 
COHEN, C. (A) 

1821 Roselyn St., Philadelphia, Pa. 
! COHEN, J. H. (M) 

Atlantic Gelatine Co., Hill St., 

Woburn, Mass. 
COLES, F. A. (A) 
Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
COMSTOCK, T. F. (A) 

Pathescope Co. of America, Inc., 

33 W. 42nd St., New York, N. Y. 
CONTNER, J. B. (M) 
Blue Seal Sound Devices, Inc., 
130 W. 46th St., New York, N. Y. 



LIST OF MEMBERS 



219 



COOK, A. A. (M) 

Bausch & Lomb Optical Co., 635 

St. Paul St., Rochester, N. Y. 
COOK, H. R., JR. (A) 

68 Harrington Ave., West wood, 

N.J. 
COOK, O. W. (M) 

Eastman Kodak Co., Kodak Park, 

Rochester, N. Y. 
COOK, W. B. (F) 

Kodascope Libraries, 33 W. 42nd 

St., New York, N. Y. 
COOLEY, W. D. (A) 

RCA Victor Co. of China, Shanghai, 

China. 
COOPER, J. A. (A) 

1909 Metropolitan B uilding, Toronto, 

Ontario, Canada. 
CORBIN, R. M. (M) 
Kodak Japan, Ltd., 3 Nishiroku 
Chome Ginza, Kyobashi, P. O. 
Box 28, Tokyo, Japan. 

CORRIGAN, J. T. (M) 

1819 G St., N. W., Washington, 

D. C. 
COUR, E. J. (F) 

1029 S. Wabash Ave., Chicago, 111. 
COURCIER, J. L. (M) 
J. E. Brulatour, Inc., 6700 Santa 

Monica Blvd., Hollywood, Calif. 
COUSINS, V. M. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
COWAN, L. (M) 

1049 N. Las Palmas Ave., Holly- 
wood, Calif. 
COWLING, H. T. (F) 

4700 Connecticut Ave., Washington, 
D. C. 

COWPERTHWAIT, F. N., JR. (4) 

Weston Electrical Instrument Corp., 
614 Frelinghuysen Ave., Newark, 
N.J. 
COZZENS, L. S. (M) 

Dupont Film Mfg. Co., Parlin, N. J. 
CRABTREE, J. (F) 

Bell Telephone Labs., Inc., 463 West 
St., New York, N. Y. 



220 



LIST OF MEMBERS 



[J. S. M. P. E. 



CRABTREE, J. I. (F) 

Research Labs., Eastman Kodak Co., 

Rochester, N. Y. 
CRABTREE, T. H. (4) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
CRAPP, G. L. (M) 

Shirley Court, Stonehurst, Pa. 
CRENNAN, O. V. (4) 

200 Eastchester Rd., New Rochelle, 

N. Y. 
CROWE, H. B. (A) 

Ritz Theatre, Elizabethton, Tenn. 
CROWLEY, J. E. (4) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
CUNNINGHAM, O. J. (4) 

18485 Lake Shore Blvd., Cleveland, 

Ohio. 
CUNNINGHAM, R. G. (M] 

2409 6th St., Coytesville, N. J. 
CUNNINGHAM, T. D. (A) 

732 Mt. Vernon Ave., Haddonfield, 

N.J. 
CURTIS, E. P (F) 

Eastman Kodak Co., 343 State St., 
Rochester, N. Y. 

CUTHBERTSON, H. B. (M) 

Paramount News, 544 W. 43rd St., 
New York, N. Y. 



DAEHR, H. (A) 

I. G. Farbenindustrie Aktiengesell- 
schaft., Kine Technical Dept., Ber- 
lin S. O. 36, Germany. 
DALOTEL, M. (M) 

Materiel Cinematographique, 111- 
113 Rue St. Maur, Paris, XIE, 
France. 
DANASHEW, A. W. (.4) 

82 Prospect of the 25th October, 

Apt. 6, Leningrad, U. S. S. R. 
DANIELSON, D. (^4) 

1002 North Main St., Russell, Kansas. 
DARBY, E. (A) 

2 Maidstone, Park Road, S. E. 1, 
Auckland, New Zealand. 



D'ARCY, E. W. (A) 

7022 Birchwood Ave., Niles, Nor- 
wood Park, 111. 
DASH, C. C. (M) 

Hertner Electric Co., 12690 Elm- 
wood Ave., Cleveland, Ohio. 
DAVEE, L. W. (F) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
DAVIDGE, L. C. (F) 

Roy Davidge Film Lab., 6701 Santa 

Monica Blvd., Hollywood, Calif. 
DAVIS, D. (A) 

RCA Victor Co., Inc., 1704 Wyan- 

dotte St., Kansas City, Mo. 
DAVIS, J. B. (A) 

3 Riggs Court, N. W., Washington, 

D. C. 
DE BRETAGNE, J. (A) 

Paris Studio Cinema, 50 Quai Point 
du Jeur , B illancourt ( Seine) , France . 
DEBRIE, A. (F) 

111-113 Rue St. Maur, Paris, 

France. 
DEFEO, L. (M) 

Roma- Villa Medioevale Torionia, 
via Lazzaro Spallanzani La, Rome, 
Italy. 
DEFRENES, J. (M) 

DeFrenes & Co., 1909 Buttonwood 

St., Philadelphia, Pa. 
DEGHUEE, C. M. (A) 

101 Liberty Ave., Mineola, Long 

Island, N. Y. 
DELVIGNE, A. F. (A) 

75 Avenue Legrand, Brussels, Bel- 
gium. 
DEMALLIE, R. B. (M) 

Kodak Japan, Ltd., 3 Nishiroku- 

chome, Ginza, Tokyo, Japan. 
DEMoos, C. (M) 

Dupont Film Mfg. Co., Parlin, N. J. 
DEPUE, B. W. (M) 

Burton Holmes Lectures, Inc., 7510 

N. Ashland Ave., Chicago, 111. 
DEPUE, O. B. (F} 

7512 N. Ashland Ave., Chicago, 111. 



Oct., 1934] 



LIST OF MEMBERS 



221 



DEROBERTS, R. (M) 

Gevaert Co. of America, Inc., 423 

W. 55th St., New York, N. Y. 
DEURGOITI, R. M. (M) 

Filmofono, S A, 4 Plaza del Callao, 

Madrid, Spain. 
DEUTSCHER, D. (A) 

33 Prospect Ave., Lynbrook, Long 

Island, N. Y. 
DEVRY, H. A. (F) 

1111 Center St., Chicago, 111. 
DICKINSON, A. S. (F) 

Motion Picture Producers & Dis- 
tributors of America, Inc., 28 W. 
44th St., New York, N. Y. 
DICKINSON, E. A. (4) 

10 Hawthorne Place, East Orange, 

N.J. 
DICKSON, W. K. L. (H) 

Montpelier House, Twickenham, 

Middlesex, England. 
DIDIEE, L. J. J. (A) 

Societe Kodak Pathe, 39 Ave. Mon- 
taigne, Paris, France. 
DIETERICH, L. M. (M} 

9165 Cordell Dr., Hollywood, Calif. 
DIMMICK, G. L. (A) 

RCA Victor Co., Inc., Camden, N. J. 
DINGA, E. W. (A) 
4514 43rd St., Long Island City, 

N. Y. 
Dix, H. W. (F) 

Austin & Dix, 120 Broadway, New 

York, N. Y. 
DOBSON, G. (M} 

494 Dwas Line Road, Clifton, N. J. 
DODDRELL, E. T. (A) 

151 Wainui Rd., Kaiti, Gisborne, 

N. Z. 
DOIRON, A. L. (A) 

Metro-Goldwyn-Mayer Studios, Cul- 
ver City, Calif. 
DONALD, J. McL. (A) 

Cu-tone Precision Engineers Ltd., 
542 Manukau Rd., Epsom, Auck- 
land, N. Z. 



DOWNES, A. C. (F) 

National Carbon Co., Cleveland, 

Ohio. 
DREHER, C. (F) 

RKO Studios, 780 Gower St., 

Hollywood, Calif. 
DUBRAY, J. A. (F) 

Bell & Howell Co., 716 N. LaBrea 

Ave., Hollywood, Calif. 
DUDIAK, F. (A) 

Fairmont Theater, Fairmont, W. Va. 
DUFFY, C. (^4) 

83 Franklin St., Providence, R. I. 
DUISBERG, W. H. (A} 

Patent Research, Inc., 521 Fifth 

Ave., New York, N. Y. 
DUNNING, C. H. (F) 

Dunning Process Co., 932 N. LaBrea 
Ave., Hollywood, Calif. 

DUNNING, O. M. (A) 

Thomas A. Edison, Inc., Orange, 

N.J. 
DUSMAN, J. F. (A) 

213 N. Calvert St., Baltimore, Md. 
DUTTON, W. P. (M) 

RCA Victor Co., Inc., Camden, N. J. 
DWYER, R. J. (A) 

180 Spruce Ave., Rochester, N. Y. 
DYKEMAN, C. L. (M} 

Dyke Cinema Products Co., 133-12 

228th St., Laurelton, N. Y. 
DYSON, C. H. U) 

47 New St., Brighton Beach, Mel- 
bourne, S. 5, Australia. 



EAGER, M. (4) 

75 Abbott Rd., Wellesley Hills, 
Mass. 

ECKARDT, H. (4) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
ECKLER, L. (M) 

Agfa Ansco Corp., Binghampton, 

N. Y. 
EDISON, T. M. (A) 

Thomas A. Edison, Inc., West 
Orange, N. J. 



222 



LIST OF MEMBERS 



[J. S. M. P. E. 



EDOUART, A. F. 

Paramount Publix Corp., 5451 Mara- 
thon St., Hollywood, Calif. 
EDWARDS, G. (F) 

49 Trafalgar Sq., Lynbrook, Long 

Island, N. Y. 
EGROT, L. G. (M) 

52 Avenue des Charmes, Vincennes, 

Seine, France. 
EHLERT, H. H. (A) 

2900 E. Grand Blvd., Detroit, Mich. 
ELDERKIN, J. K. (M) 

145 Valley St., Belleville, N. J. 
ELLIS, E. P. (A) 

19 Curtis Place, Maplewood, N. J. 
ELLIS, F. E., JR. U) 

717 W. Wells St., Milwaukee, Wis. 
ELLISON, M. (M) 

922 x /2 Maltman Ave., Los Angeles, 

Calif. 
ELMER, L. A. (M) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
ELWELL, C. F. (M) 

Chestnut Close, Kingswood, Surrey, 

England. 
ENGL, J. B. (F) 

97 Bismarkstrasse, Berlin-Charlot- 

tenburg, Germany. 
EPSTEIN, F. (4) 

Wilcza Str. 29a/12, Warsaw, Poland. 
ESSIG, A. G. (4) 

924 Foulkrod St., Philadelphia, Pa. 
EVANS, P. H. (F) 

Warner Bros. Pictures, Inc., 1277 

E. 14th St., Brooklyn, N. Y. 
EVANS, R. (F) 

Division of Motion Pictures, U. S. 
Dept. of Agriculture, Washington, 
D. C. 
EVANS, R. M. (F) 

110 Morningside Dr., New York, 
N. Y. 

FAITHFULL, G. (Af) 

Archibald Nettlefold Productions, 
The Studios, Hurst Grove, Wai- 
ton-on-Thames, England. 



FALQUET, A. (A) 

Kodak S. P. z. o. o., 5 Place Napo- 

leon, Warsaw, Poland. 
FAMULENER, K. (^4) 

395 Fort Washington Ave., New 

York, N. Y. 
FARNHAM, R. E. (F) 

General Electric Co., Cleveland, 

Ohio. 
FARRAND, C. L. (/O 

United Research Corp., 321 W. 44th 

St., New York, N. Y. 
FAULKNER, T. (M) 

514 W. 57th St., New York, N. Y. 
FELTHOUSEN, A. J. (4) 

1114 N. Everett St., Glendale, Calif. 



FENIMORE, R. W. 

1776 Stanford Rd., Berkeley, Mich. 
FERGUSON, D. C. (4) 

118 W. 57th St., New York, N. Y. 
FERNANDEZ, M. A. (A) 

Ave Rep. Argentina 91-93 Mexico, 

D. F. 
FINN, J. J. (Jlf) 

580 Fifth Ave., New York, N. Y. 

FlTZPATRICK, J. M. S. (A) 

Kodak Ltd., Wealdstone, Middlesex, 

England. 
FLANAGAN, J. T. (Af) 

Tri-State Motion Picture Co., 2108 

Payne Ave., Cleveland, Ohio. 
FLANNAGAN, C. (F) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
FLEISCHER, M. (F) 

Fleischer Studios, 1600 Broadway, 

New York, N. Y. 
FLINT, A. (M) 

8 Jochum Ave., Larchmont, N. Y. 
FLORY, L. P. (AT) 

Boyce-Thompson Institute, 1086 N. 

Broadway, Yonkers, N. Y. 
FOLEY, T. E. (A) 

Box 682, Kelowna, B. C., Canada. 
FONDA, J. C. (A] 

234 White Plains Road, Tuckahoe, 
N. Y. 



Oct., 1934] 



LIST OF MEMBERS 



223 



FOOTE, P. C. (A) 

Bell & Howell Co., 4045 N. Rockwell 

St., Chicago, 111. 
FORD, W. B. (A) 

3 Belmont House, Candover St., 

London, W. 1., England. 
FOSTER, W. D. (F) 

Kinatome Patents Corp., 45 N. 

Broad St., Ridgewood, N. J. 
FRACKER, E. G. (M) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
FRANK, J., JR. (M) 

RCA Victor Co., Inc., Camden, N. J. 
FRANK, K. G. (M) 

729 Seventh Ave., Rm. 604, New 

York, N. Y. 
FRANKLIN, H. B. (F) 

RKO Pictures, Inc., 1260 Sixth Ave., 

New York, N. Y. 
FRAYNE, J. G. (F) 

Electrical Research Products, Inc., 
7046 Hollywood Blvd., Los Ange- 
les, Calif. 
FREEDMAN, A. E. (70 

De Luxe Labs., Inc., 441-461 W. 

55th St., New York, N. Y. 
FREEMAN, A. B. (4) 

2425 N. 54th St., Philadelphia, Pa. 
FREERICKS, B. (M) 

8956 Dicks St., West Hollywood, 

Calif. 
FREIMANN, F. (F) 

Electro Acoustic Products Co., 2131 

Bueter Rd., Fort Wayne, Ind. 
FREUND, K. (4) 

12730 Hanover St., Los Angeles, 

Calif. 
FRITTS, E. C. (F) 

Eastman Kodak Co., Inc., 343 State 
St., Rochester, N. Y. 

GAGE, H. P. (F) 

Corning Glass Works, Corning, N. Y. 
GAGE, O. A. (M) 

Corning Glass Works, Corning, N. Y. 
GALE, E. (A) 

2823 Hubbard St., Brooklyn, N. Y. 



GALLO, R. 04) 

Quigley Publications, 1790 Broad- 
way, New York, N. Y. 
GANSTROM, R. G. (A) 

15087 Winthrop Ave., Detroit, Mich. 
GARLING, W. F. (M) 

RCA Photophone, Inc., Film House, 

Wardour St., London, England. 
GASKI, T. J. (M) 

26 Henry Ave., Palisade Park, N. J. 
GEIB, E. R. (F) 

National Carbon Co., Cleveland, 

Ohio. 
GELMAN, J. N. (M) 

3439 Jays St., Cincinnati, Ohio. 
GENOCK, E. P. (A) 

28 Dorset Rd., Merton Park, Surrey, 

S. W. 19, England. 
GENT, E. W. (M) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
GEORGENS, G. R. (M) 

3109 17 St., N. E., Washington, 

D. C. 
GERMAINE, M. 04) 

702 E. 10th St., Brooklyn, N. Y. 
GERMAN, W. J. (M) 

J. E. Brulatour, Inc., 154 Crescent 

St., Long Island City, N. Y. 
GERNOLLE, N. (A) 

Paris Studio Cinema, 50 Quai Point 
du Jeur, Billancourt (Seine), 
France. 
GEYER, K. (M) 

Geyer-Werke, A. G., Harzerstrasse 
39/42, Berlin, S. O. 36, Germany. 
GEYER, W. (M) 

Am. Treptower Park 59, Berlin, 

S. 0. 36, Germany. 
GIBBONS, J. M. 04) 

825 Nantasket Ave., Allerton, Mass. 

GIBSON, G. H. (A) 

J. E. Brulatour, Inc., 6700 Santa 

Monica Blvd., Hollywood, Calif. 
GIESKIENG, M. W. (A) 

901 Booker St., Little Rock, Ark. 



224 



LIST OF MEMBERS 



[J. S. M. P. E. 



GIHBSSON, L. (A) 

J. L. Nerlien, Ltd., Nedre Slotsgate 

13, Oslo, Norway. 
GILMOUR, J. G. T. (M) 

General Electric Co., Schenectady, 

N. Y. 
GLASSER, N. (M) 

Warner Bros. Theaters, 932 F St., 

N. W., Washington, D. C. 
GLAUBER, S. (A) 

2062 E. 37th St., Brooklyn, N. Y. 
GLEASON, C. H. (A) 

14 North Hancock St., Lexington, 

Mass. 
GLICKMAN, H. (M} 

789 Saint Marks Ave., St. Johns, 

Brooklyn, N. Y. 
GLOVER, C. W. (M) 

Abbey House, Westminster, London, 

S. W. 1, England. 
GLUNT, O. M. (70 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
GOLDBERG, J. H. (M) 

822 S. Wabash Ave., Chicago, 111. 
GOLDIN, H. (A) 

Northern Electric Co., Ltd., 1261 
Shearer St., Montreal, P. Q. 

GOLDSCHNEIDER, G. (A) 

1208 Vyse Ave., The Bronx, N. Y. 
GOLDSMITH, A. N. (F) 

444 Madison Ave., New York, 

N. Y. 
GOOKIN, F. M. (A) 

22 Eddy St., N. Attleboro, Mass. 
GRAHAM, H. (A) 

546 Lincoln St., Denver, Col. 
GRASS, R. L. (A) 

1064 E. 28th St., Brooklyn, N. Y. 
GREEN, N. B. (F} 

Camera Works, Eastman Kodak Co., 

Rochester, N. Y. 
GREENE, C. L. (F) 

2722 S. Harriet Ave., Minneapolis, 

Minn. 
GREENE, P. E. (A) 

458 Park Ave., East Orange, N. J. 



GRIFFIN, H. (F) 

International Projector Corp., 90 

Gold St., New York, N. Y. 
GRIFFITH, L. M. (M) 

8000 Blackburn Ave., Los Angeles, 

Calif. 
GRIFFITHS, P. H. (M} 

Briar Lea, Norbreck Rd., Blackpool, 

England. 
GROTE, W. G. (A) 

Paramount Productions, Inc., 5451 
Marathon St., Hollywood, Calif. 
GROVER, H. G. (M) 

570 Lexington Ave., New York, 

N. Y. 
GUINTINI, C. (A) 

P. O. Box 411, Los Banos, Calif. 
GUNN, A. H. (A) 

6 Sibley Place, Rochester, N. Y. 

HACKEL, J. (M) 

120 E. 41st St., New York, N. Y. 
HAEFELE, N. C. (M) 

417 St. Paul St., Baltimore, Md. 
HALBERTSMA, N. A. (.4) 

Philips Glowlamp Works, Ltd., Eind- 
hoven, Holland. 
HAMPTON, L. N. (M) 

246 E. Tremont Ave., Bronx, N. Y. 
HANABERY, J. E. (A) 

8310 35th Ave., Jackson Heights, 

Long Island, N. Y. 
HANDA, D. (A) 

c/o S. R. Handa, Roads Engineer, 

Jaipur State (Rajputana), India. 
HANDA, G. C. (A) 

D. 96, Model Town, Lahore, Punjab, 

India. 
HANDLEY, C. W. (M) 

1960 W. 84th St., Los Angeles, Calif. 
HANNA, C. R. (70 

Westinghouse Electric & Mfg. Co., 

East Pittsburgh, Pa. 
H ANNAN, J. H. U) 

P. O. Box 41, Golden, Col. 
HARCUS, W. C. (M) 

14410 Burbank Blvd., Van Nuys, 
Calif. 



Oct., 1934] 



LIST OF MEMBERS 



225 



HARDINA, E. (A) 

Warner Bros. Pictures, Inc., 1277 E. 

14th St., Brooklyn, N. Y. 
HARDING, H. V. (A) 

186 Pinehurst Ave., New York, N. Y. 
HARDMAN, W. F. (A) 

St. Charles Hotel, Pierre, S. D. 
HARDY, A. C. (F) 

Massachusetts Institute of Tech- 
nology, Cambridge, Mass. 
HARLEY, J. B. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
HARLOW, J. B. (M) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, 

N. Y. 
HARRINGTON, T. T. (M) 

647 Cragmont Ave., Berkeley, Calif. 
HARRISON, H. C. (F) 

94 Bayview Ave., Port Washington, 

Long Island, N. Y. 
HART, K. R. M. U) 

P. N. Russell School of Engineering, 
University of Sydney, N. S. W., 
Australia. 
HARUKI, S. (F) 

The Fuji Photo Film Co., Near 

Odahara, Kanagawaken, Japan. 
HARVEY, A. E. (4) 

Harvey Amusement Co., Newman, 

Calif. 
HECK, F. P. (M) 

Da-Lite Screen Co., Inc., 2723 N. 

Crawford Ave., Chicago, 111. 
HELLOWELL, T. (A) 

50 Clyde St., Bondi North, Sydney, 

N. S. W., Australia. 
HENKEL, J. F. U) 

11 George St., Brooklyn, N. Y. 
HENNESSY, W. W. (M) 

250 Mamaroneck Ave., White Plains, 

N. Y. 
HERRIOTT, W. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
HEWSON, J. H. (A) 
478Sunnyside Ave., Ottawa, Canada. 



HEYL, E. O. (A) 

RCA Victor Co., Inc., Camden, N. J. 
HIATT, A. (M) 

Pathe News, Inc., 35 W. 45th St., 

New York, N. Y. 
HICKMAN, C. N. (A) 

35-36 79th St., Jackson Heights, 

Long Island, N. Y. 
HICKMAN, K. (F) 

Research Labs., Eastman Kodak Co., 

Rochester, N. Y. 
HIGGINS, T. G. (A) 

69 Gouett St., Randwick, Sydney, 

Australia. 
HILL, M. H. (A) 

Butlers, Inc., 415 Market St., Wil- 
mington, Del. 
HILTON, R. B. (A) 

30 W. 54th St., New York, N. Y. 
HOCH, W. C. (A) 

1030 Monument St., Pacific Pali- 
sades, Calif. 
HOFFMAN, L. B. (M) 

92 Hickory Grove Dr., Larchmont, 

N. Y. 
HOGE, J. F. D. (F) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
HOLDEN, H. C. (M) 

224 Union St., Schenectady, N. Y 
HOLLANDER, H. (M} 

2146 Barnes Ave., The Bronx, N. Y. 

HOLLEBONE, S. H. (^4) 

214 Hohnwood Ave., Ottawa, Can- 
ada. 
HOLMAN, A. J. (M) 

57 N. 22nd St., East Orange, N. J. 
HOLSLAG, R. C. (Af) 

120 W. 228th St., New York, N. Y. 
HOPKINS, J. J. (10 

29-41 167th St., Flushing, Long 

Island, N. Y. 
HOPKINS, T. L. (A) 

1203 Quincy St., N. W., Washington, 

D. C. 
HOPPIN, C. (A) 

145 bis Rue D'Alesia, Paris, France. 



226 



LIST OF MEMBERS 



[J. S. M. P. E. 



HORNIDGE, H. T. (M) 

Kiddle, Margeson & Hornidge, 511 

Fifth Ave., New York, N. Y. 
HORNSTEIN, J. C. (M) 

Warner Bros. Pictures, Inc., 321 W. 

44th St., New York, N. Y. 
HORSTMAN, C. F. (M) 

Radio-Keith-Orpheum Corp., 1560 

Broadway, New York, N. Y. 
HOTCHKISS, F. H. (M) 

Societe de Materiel Acoustique, 
1 Blvd. Haussman, Paris, France. 
HOWELL, A. S. (F) 

Bell & Howell Co., 4045 N. Rockwell 

St., Chicago, 111. 
HUBBARD, B. L. (M) 

140 Marne Ave., Haddonfield, N. J. 
HUBBARD, R. C. (70 

American Record Corp., Scranton 

Life Bldg., Scranton, Pa. 
HUDSON, G. (A) 

Ilford, Ltd., Selo Works, Brentwood, 

Essex, England. 
HUDSON, W. (A) 

2174 S. 85th St., West Allis, Wis. 
HULAN, A. G. (M) 

100 N. Goodman Ave., Kerens, 

Texas. 
HUMPHREY, G. H. (A) 

Adcraft Film Service, 1312 Oswego 

St., Utica, N. Y. 
HUNT, F. L. (F) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
HUNT, H. H. (A) 

2312 Cass St., Detroit, Mich. 
HUSE, E. (F) 

Eastman Kodak Co., 6706 Santa 

Monica Blvd., Hollywood, Calif. 
HYNDMAN, D. E. (F) 

Eastman Kodak Co., 350 Madison 
Ave., New York, N.Y. 



INGMAN, T. M. (M) 

6100 Glen Oaks, Hollywood, Calif. 
IRBY, F. S. (M) 

400 E. 58th St., New York, N. Y. 



IVES, F. E. (H) 

1753 N. 15th St., Philadelphia, Pa. 
IVINS, C. F. (A) 

Pathescope Co. of America, 35 W. 
42nd St., New York, N. Y. 



JACHONTOW, E. G. (M) 

The Optical Institute, Birjevaya 

Linia 12, Leningrad, U. S. S. R. 
JAMES, F. E. (M) 

General Electric Co., 5201 Santa Fe 

Ave., Los Angeles, Calif. 
JAMIESON, H. V. (M} 

2212 Line Oak St., Dallas, Texas. 
JARRETT, G. J. (M) 

Metropolitan Motion Picture Co., 
1745 Grant Blvd., E., Detroit, 
Mich. 
JAY, R. L. (M) 

Jay's Film Service, 17 Blythswood 

Square, Glasgow, C. 2, Scotland. 
JEFFERY, F. A. (A ) 

9 Giles St., Toorak, Adelaide, Aus- 
tralia. 
JENSEN, G. K. (M ) 

12a Putney Hill, London, S. W. 15, 

England. 
JOACHIM, H. E. A. (F) 

Zeiss Ikon A. G., Schandauerstr. 76, 

Dresden, A. 21, Germany. 
JOHN, W. E. (M} 

Standard Bank of S. A. Ltd., 
Northumberland Ave., London, 
W. C. 1, England. 
JONES, E. H. (A) 

6 Hobart Ave., Summit, N. J. 
JONES, J. G. (F) 

Eastman Kodak Co., Kodak Park, 

Rochester, N. Y. 
JONES, L. A. (F) 

Research Labs., Eastman Kodak Co., 

Rochester, N. Y. 
JOY, D. B. (A) 

National Carbon Co., Fostoria, Ohio. 
JOY, J. M. (M) 

12 Fairview Ave., Nepperham 
Heights, Yonkers, N. Y, 



Oct., 1934] 



LIST OF MEMBERS 



227 



JUDGE, P. E. (A) 

22 Fay Ave., Peabody, Mass. 

KALMUS, H. T. (F) 

Technicolor, Inc., 823 N. Seward 

St., Hollywood, Calif. 
KAMEI, K. (A) 

396-2 Miyananoue Morigu; Nishi- 

nomiya City, Japan. 
KAPLAN, L. (M) 

Panama Canal Dept. of Motion 
Picture Service, Quarry Heights, 
Panama Canal Zone. 
KEIRNAN, F. K. (A) 

Room 1101, 52 Vanderbilt Ave., 

New York, N. Y. 
KEITH, C. R. (M ) 

Western Electric Co., Ltd., Coles 
Green Rd., London, N. W. 2, 
England. 
KELLER, A. C. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
KELLEY, W. V. D. (F) 

2228 Holly Dr., Hollywood, Calif. 
KELLOGG, E. W. (4) 

RCA Victor Co., Inc., Camden, N. J. 
KENDE, G. (M) 

210 Sixth Ave., New York, N. Y. 
KERSHAW, C. (F) 

A. Kershaw & Son, 200 Harehills 

Lane, Leeds, England. 
KESSEL, N. (A) 

84 Cedar St., Brooklyn, N. Y. 
KEUFFEL, C. W. (M) 

Keuffel & Esser Co., 3rd & Adams 
Sts., Hoboken, N. J. 

KlENNINGER, J. F. (M) 

Technicolor Motion Picture Corp., 
1016 North Cole Ave., Hollywood, 
Calif. 

KlMBERLEY, P. (M) 

National Screen Service, Ltd., 25 
Denmark St., London, W. C. 2, 
England. 
KING, F. M. (M} 

36 Crestwood Ave., Buffalo, N. Y. 



KING, H. V. (A) 

British Lion Studios, Beaconsfield, 

Bucks, England. 
KLAUSSEN, B. (A) 

332 Stratford Rd., Brooklyn, N. Y. 
KLEBER, J. O. (M} 

Room 1154, 125 E. 46th St., New 

York, N. Y. 
KLEERUP, B. J. (M) 

Society for Visual Education, 327 

LaSalle St., Chicago, 111. 
KNOX, H. G. (M) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
KOHLER, J. J. (A) 

4542 44th St., Sunnyside, Long 

Island, N. Y. 
KONDO, T. (A) 

2-17 Itahashicho Itahashiku, Tokyo, 

Japan. 
KOSSMAN, H. R. (A) 

Andre Debrie, Inc. 115 W. 45th St., 

New York, N. Y. 
KRAEMER, G. I. (Jlf) 

16 Rue de Chateau dun, Asnieres 

(Seine), France. 
KRASNA-KRAUS, A. (M) 

Filmtechnik, Friedrichstrasse 46, 

Berlin, S. W. 68, Germany. 
KRUGERS, G. E. A. (M) 

Westhofweg 18, Bandoeng, Java, 

D.E.I. 
KUHN, J. J. (M) 

Bell Telephone Labs., Inc., 463 West 
St., New York, N. Y. 

KUNZMANN, W. C. (F) 

Box 400, Cleveland, Ohio. 

KURLANDER, J. H. (F) 

Westinghouse Lamp Co., Bloom - 
field, N. J. 

LACHAPELLE, L. (M) 

Consolidated Amusement Co., Ltd., 
P. O. Box 2425, Honolulu, Hawaii. 
LAIR, C. (M) 

Kodak-Pathe, 30 Rue des Vignerons, 
Vincennes (Seine), France. 



228 



LIST OF MEMBERS 



[J. S. M. P. E. 



LAKEWITZ, F. S. (4) 

41-4:2 42nd St., Long Island City, 

N. Y. 
LAL, G. D. (M) 

RCA Victor Co., Inc., Camden, N. J. 
LAMB, E. E. (Af) 

Bell & Howell Co., 320 Regent St., 

London, W. 1, England. 
LAMBERT, K. B. (F) 

Metro-Goldwyn-Mayer Studios, Cul- 
ver City, Calif. 
LANE, A. L. (M} 
4205 LaSalle Ave., Culver City, 

Calif. 
LANE, G. (M) 

Audio Productions, Inc., 250 W. 57th 

St., New York, N. Y. 
LANE, W. H. (If) 

189 Patterson Ave., Ottawa, Ontario, 

Canada. 
LANG, A. (A) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, 
N. Y. 
LANGFORD, L. P. (M) 

11733 Edgewater Dr., Lakewood, 

Ohio. 
LANSING, D. W. (M) 

RCA Victor Co., Inc., Camden, N. J. 
LAPORTE, N. M. (M) 

Paramount Publix Corp., 1501 Broad- 
way, New York, N. Y. 
LARSEN, P. J. (F) 

55 W. 42nd St., New York, N. Y. 
LARSON, I. J. (A) 

218 Knox Ave., Grantwood, N. J. 
LARUE, M. W. (A) 

6157 N. Artesian Ave., Chicago, 111. 
LASKY, J. L. (M} 

Fox Films, Drawer K, Hollywood, 

Calif. 
LAUSTE, E. A. (H) 

12 Howard St., Bloomfield, N. J. 
LAWLEY, H. V. (M} 

Lawley Apparatus Co., Ltd., 26 
Church St., Charing Cross Rd., 
London, W. 1, England. 



LEARN ARD, H. P. (A) 

Consolidated Amusement Co., Hono- 
lulu, Hawaii. 
LECOQ, J. U) 

116 rue de la Convention, Paris 15e, 

France. 
LEE, A. E. (A) 

Gaumont British Picture Corp. of 
America, 226 W. 42nd St., New 
York, N. Y. 
LEISHMAN, E. D. (M} 

Radio Keith Pictures, Ltd., P. O. 

Box 454, Calcutta, India. 
LENZ, F. (A) 

116-40 227th St., St. Albans, Long 

Island, N. Y. 
LESHING, M. S. (F) 

Fox Films, Inc., 1401 N. Western 

Ave., Los Angeles, Calif. 
LEVENTHAL, J. F. (F) 

175 Varick St., New York, N. Y. 
LEVINSON, N., (A) 

1761 N. Van Ness Ave., Hollywood, 

Calif. 
LEWIS, B. C. (A) 

Northern Electric Co., 1261 Shearer 

Street, Montreal, Canada. 
LICHTE, H. ( F) 

Tautenbergerster 33, Berlin-Lank- 

witz, Germany. 
LIDDLE, A. J. (M) 

S. Guiterman & Co., Ltd., 36 Alder- 
manbury, London, E. C. 2, Eng- 
land. 

LlNDERMAN, R. G. (M) 

205 Edison Bldg., Fifth and Grand 

Ave., Los Angeles, Calif. 
LINGG, A. (4) 

I. G. Farbenindustrie Aktiengesell- 
schaft, Camerawerk, Tegernseer- 
landstr. 161, Munich, Germany. 
LINS, P. A. (M} 

Madison Mart, Inc., 403 Madison 

Ave., New York, N. Y. 
LITTLE, W. F. (F} 

Electrical Testing Labs., 80th St. & 
East End Ave., New York, N, Y. 



Oct., 1934] 



LIST OF MEMBERS 



229 



LlVERMAN, C. 04) 

9 rue Paul Feval, Paris, France. 
LOOTENS, C. L. (Af) 

175 Ames Ave., Leonia, N. J. 
LOY, L. C. (A) 

16126 Griggs Ave., Detroit, Mich. 
LUCAS, G. S. C. (Af) 

British-Thomson-Houston Co., Ltd., 

Rugby, England. 
LUHAR, C. M. (Af) 

Mehta-Luhar Productions, 176 Main 

Rd., Dadar, Bombay, 14, India. 
LUKE, E. (Af) 
Kenton House, Upper Shirley Rd., 

Croydon, Surrey, England. 
LUKES, S. A. (A) 

6145 Glenwood Ave., Chicago, 111. 
LUMIERE, L. (H) 

156 Blvd. Bineau A. Neuilly, Paris, 
France. 

LUMMERZHEIM, H. J. (Af) 

I. G. Farbenindustrie Aktiengesell- 
schaft, Berlin, S. O. 36, Germany. 
LUNDAHL, T. (Af) 

4404 Sixth Ave., Brooklyn, N. Y. 
LUNDIE, E. S. (A ) 

United Research Corp., 4139 38th 

St., Long Island City, N. Y. 
LUTTER, H. (A) 

59 Peck Ave., Newark, N. J. 
LYON, L. H. (4) 

402 Shirley St., Marshall. Texas. 

MAAS, A. R. (A) 

A. R. Maas Chemical Co., 308 E. 8th 
St., Los Angeles, Calif. 

MAClLVAIN, K. H. (A) 

41 Nassau Ave., Malverne, Long 

Island, N. Y. 
MACKENZIE, D. (F) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
MACLEOD, J. S. (M) 

Metro - Goldwyn - Mayer Pictures, 
1540 Broadway, New York, N. Y. 
MACNAIR, W. A. (F) 

Bell Telephone Labs., Inc., 463 West 
St., New York, N. Y. 



MACOMBER, W. W. (4) 

Box 3304, Chicago, 111. 
MAIRE, H. J. (Af) 

5640 Kingsessing Ave., Philadelphia, 

Pa. 
MALHTRA, M. N. (A) 

Jai Krishanian St., Machi Hatta 

Bazar, Lahore, India. 
MANCHEE, A. W. (Af) 

91 Prospect St., East Orange, N. J. 
MANHEIMER, J. R. (Af) 

E. J. Electrical Installation Co., 227 

E. 45th St., New York, N. Y. 
MANN, R. G. (A) 

Pathe News, 35 W. 45th St., New 

York, N. Y. 
MARCHESSAULD, C. E. (^4) 

151-22 85 Drive, Jamaica, Long 

Island, N. Y. 
MARESHCAL, G. (A) 

30 Rue de la Garenne Sevres (Seine 

et Oise), France. 
MARETTE, J. (Af) 

Pathe Cinema, 6 Rue Leconte de 

Lisle, Paris, France. 
MARGOSSIAN, M. (A) 

2451 Le Conte Ave., Berkeley, Calif. 
MARSH, H. N. (A) 

Hercules Powder Co., Wilmington, 

Del. 
MASAOKA, K. (A) 

82 Shimokamotakagicho Sakyoku, 

Kyoto, Japan. 
MASUTANI, R. (-4) 

Kinutamura Kitatamagun, Tokyo 

Prefecture, Japan. 
MATHOT, J. A. (Af) 

Eclair Tirage, 34a 42 Av. d'Enghein 

Epinay sur Seine, France. 
MATLACK, C. C. (Af) 

249 E. Flagler St., Miami, Fla. 
MATTHEWS, G. E. (F) 

Research Labs., Eastman Kodak 

Co., Rochester, N. Y. 
MAURAN, J. (A ) 

537 Statler Building, Boston, Mass 
MAURER, J. A. (A) 

554 W. 114th St., New York, N. Y. 



230 



LIST OF MEMBERS 



[J. S. M. p. E. 



MCAULEY, J. E. (F) 

McAuley Mfg. Co., 552 W. Adams 
St., Chicago, 111. 

MCBURNEY, J. W. (M ) 

41 Floral Ave., Binghampton, N. Y. 
McCANN, F. D. (M) 

Westinghouse Electric & Mfg. Co., 

30 Rockefeller Plaza, New York, 

N. Y. 

MCCLINTOCK, N. (M) 

Rutgers University, New Brunswick, 
N.J. 

McCROSKEY, H. E. (M) 

5451 Marathon St., Hollywood, 
Calif. 

McCULLOUGH, R. (F) 

1833 S. Vermont Ave., Los Angeles, 
Calif. 

MCDOWELL, J. B. (4) 

Agfa Ltd., 1-4 Lawrence St., High 

St., London, W. C. 2, England. 
McGiNNis, F. J. (A) 

Box 2387, Palm Beach, Fla. 
McGuiRE, P. A. (F) 

International Projector Corp., 90 
Gold St., New York, N. Y. 

McLEMORE, R. (4) 

Electrical Research Products, Inc., 
1435 G St., N. W., Washington, 
D. C. 
McM ASTER, D. (F) 

Eastman Kodak Co., 343 State St., 

Rochester, N. Y. 
McMATH, R. R. (M) 

Motors Metal Mfg. Co., 5936 Mil- 
ford Ave., Detroit, Mich. 
McNABB, J. H. (F) 

Bell & Howell Co., 1801 Larchmont 
Ave., Chicago, 111. 

MCNAMARA, D. T. (A) 

7 Baker Ave., East Lexington, Mass. 
McNicoL, D. (F) 

132 Union Rd., Roselle Park, N. J. 
McRAE, D. (M) 

99 Melrose St., Melrose, Mass. 
MECHAU, E. (F) 

Albrechtstrasse 60 A, Berlin-Sudende, 
Germany. 



MEES, C. E. K. (F) 

Research Labs., Eastman Kodak Co., 

Rochester, N. Y. 
MEHTA, H. S. (M) 

Lilwati Terrace, Bombay, 4, India. 
MESSITER, H. M. (A) 

P. O. Box 165, Scarsdale, N. Y. 
METZGER, M. (A) 

Associated Screen News Ltd., West- 
ern Ave. & Delcarie Blvd., Mon- 
treal, Canada. 
MEYER, H. (F) 

1426V2 No. Beachwood Ave., Holly- 
wood, Calif. 
MIEHLING, R. (M) 

1766 Amsterdam Ave., New York, 

N. Y. 
MILI, G. (A) 

Westinghouse Lamp Co., Bloom- 
field, N. J. 
MILLER, A. W. (A) 

47 Westfield Ave., E., Roselle Park, 

N.J. 
MILLER, J. A. (F) 

46-27 193rd St., Flushing, L. I. 
MILLER, O. E. (4) 

588 Magee Ave., Rochester, N. Y. 
MILLER, R. (A ) 

R. No. 1, Box 131, Salem, Oregon. 
MILLER, R. A. (M) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
MILLER, V. E. (A) 

1247 N. Detroit St., Hollywood, 

Calif. 
MILLER, W. C. (F) 

Metro-Goldwyn-Mayer, Culver City, 

Calif. 
MINO, T. J. (A) 

3812 Oakwood Ave., Los Angeles, 

Calif. 
MINNERLY, N. H. (A ) 

c/o Willman, 310 W. 95th St., New 

York, N. Y. 
MISTRY, D. L. (M) 

24 Nepean Road, Malabar Hill, 
Bombay, 6, India. 



Oct., 1934] 



LIST OF MEMBERS 



231 



MISTRY, M. L. (M) 

24 Nepean Rd., Malabar Hill. 

Bombay, 6, India. 
MITCHELL, G. A. (F) 

Mitchell Camera Company, 665 N. 
Robertson Blvd., West Hollywood, 
Calif. 
MITCHELL, M. N. (A) 

Monroe Theatre, Rochester, N. Y. 
MITCHELL, R. F. (F) 

4230 N.Winchester Ave., Chicago, 111. 
MOLE, P. (F) 

Mole-Richardson, Inc., 941 No. Syca- 
more Ave., Hollywood, Calif. 
MOORE, T. (M) 

The Westchester, Washington, D. C. 
MORENO, R. M. (M) 

DuPont Film Mfg. Corp., Parlin, 

N.J, 
MORGAN, K. F. (F) 

Electrical Research Products, Inc., 
7046 Hollywood Blvd., Los Ange- 
les, Calif. 
MORRIS, L. P. (A) 

3408 Parker Ave., Chicago, 111. 
MORTON, H. S. (M) 

5650 Grand River Blvd., Detroit, 

Mich. 
MORTON, T. (A) 

Kodak Ltd., Postafiok 146, Buda- 
pest, IV, Hungary. 
MORTON, W. M. (A) 

R. F. D. No. 7, Knoxville, Tenn. 
MOSKOWITZ, J. H. (A} 
Amusement Supply Co., 341 W. 44th 

St., New York, N. Y. 
MOTWANE, V. G. (M) 

193 Hornby Road, Fort, P. O. Box 

459, Bombay, India. 
MOYSE, H. W. (F) 

Smith & Aller, Ltd., 6656 Santa 

Monica Blvd., Hollywood, Calif. 
MUELLER, W. A. (M ) 

5011 N. Ambrose Ave., Hollywood, 
Calif. 

MULLER, J. P. (M) 

5738 Stony Island Ave., Chicago, 
111. 



MURDOCH, S. E. (A) 

3 Cabramatta Rd., Mosman, Sydney, 

N. S. W., Australia. 
MURPHY, G. D. (A) 

3148 O St., N. W., Washington, 

D. C. 
MURRAY, A. P. (A) 

14 Chilton Road, West Roxbury 
Mass. 



NADELL, A. (M) 

494 Hendrix St., Brooklyn, N. Y. 
NAGASE, T. (M) 

D. Nagase & Co., Ltd., 7 Itachibori- 
minamidori-Nishiku, 1 Chome, 
Osaka, Japan. 
NANGLE, W. O. (A ) 

General Delivery, Champaign, 111. 
NELSON, E. W. (A) 

3910 Wellington Ave., Chicago, 111. 
NELSON, O. (M) 

National Cash Register Co., Dayton, 

Ohio. 
NEU, O. F. (M) 

Neumade Products Corp., 442 W. 

42nd St., New York, N. Y. 
NICHOLSON, R. F. (F) 

1569 E. 27th St., Brooklyn, N. Y. 
NICKOLAUS, J. M. (F) 

Metro-Goldwyn-Mayer Studios, Cul- 
ver City, Calif. 
NIELSEN, J. F. (A) 

United Research Corp., 41-39 38th 

St., Long Island City, N. Y. 
NIEPMANN, C. H. (M) 

Kandem Electrical Ltd., 711 Ful- 
ham Road, London S. W. 6, Eng- 
land. 
NIGAM, C. S. (A) 

East India Film Co., Regent Park, 

Tollygunge, Calcutta, India. 
NIXON, I. L. (F) 

Bausch & Lomb Optical Co., Roches- 
ter, N. Y. 
NORLING, J. A. (M) 

Loucks & Norling, Inc., 245 W. 55th 
St., New York, N.Y. 



232 



LIST OF MEMBERS 



[J. S. M. p. E 



NOURISH, B. E. (Jlf) 

Associated Screen News of Canada, 
Ltd., Western Ave. & Delcarie 
Blvd., Montreal, Canada. 
NORTON, R. (A) 

2013 N. 63rd St., Philadelphia, Pa. 
NORWOOD, D. W. (M) 

Chanute Field, Rantoul, 111. 



OAKLEY, N. F. 

DuPont Film Mfg. Corp., Parlin, 
N.J. 

O'BOLGER, R. E. (M) 

Eastman Kodak Co., 24 Yuen Ming 

Yuen Rd., Shanghai, China. 
O'BRIEN, M. D. (A) 

Park Ave., Merrick, N. Y. 
OHTA, V. (A) 

1 Tsukudocho Ushigomeku Tokyo, 
Japan. 

O'KEEFE, G. A. (A) 

132 Bank St., New York, N. Y. 
OLIVER, W. J. (-4) 

328a 8th Ave., West Calgary, 

Canada. 
OLMSTEAD, L. B. (A) 

435 Van Cortlandt Park Ave., 

Yonkers, N. Y. 
OLSON, O. E. (A) 

Local 164 IATSE, 344 Commerce 

Bldg., Milwaukee, Wis. 
ORAM, E. (A) 

"Poole," Shakespeare Rd., Mill Hill, 

London, N. W. 7, England. 
OSAWA, Y. (M} 

J. Osawa & Co., Ltd., Sanjo Kobashi, 

Kyoto, Japan. 
OSBORNE, A. W. (M) 

"Hilton" North Dr., Ruislip, Middx., 

England. 
OSTER, E. (4) 

5070 Woodley Ave., Van Nuys, 

Calif. 
OWENS, F. H. (A) 

2647 Broadway, New York, N. Y. 

PACENT, L. G. (F) 

Pacent Engineering Corp., 79 Madi- 
son Ave., New York, N. Y. 



PACHOLKE, F. (A) 

508 Winthrop Ave., Jackson, Mich. 
PADEN, C. B. (A) 

146 Leavenworth St., San Francisco, 

Calif. 
PAGE, L. I. (A) 

RKO Studios, Inc., 780 Gower St., 

Hollywood, Calif. 
PALMER, M. W. (F) 

Motion Picture Lighting and Equip- 
ment Co., 318 W. 48th St., New 
York, N. Y. 
PARKER, O. B. (M) 
46-07 260th St., Little Neck, Long 

Island, N. Y. 
PARKINS, C. F. (M) 

Studio Film Labs., Ltd., 80 Wardour 

St., London, W. 1, England. 
PARRISH, H. C. (A) 

Berk House, 76 William St., Sydney, 

N. S. W., Australia. 
PARSHLEY, C. W. (A) 

University Theatre, Cambridge, 

Mass. 
PATEL, K. K. (A) 

1598 Raipur Zadken, St. Ahmeda- 

bad, India. 
PATEL, M. B. (A) 

Krishna & Gujrat Studios, 162 Dadar 

Rd., Dadar, Bombay, India. 
PATTON, G. E. (If) 

Ontario Govt. Mot. Pict. Bureau, 
Parliament Bldgs., Toronto, 
Canada. 
PECK, W. H. (A} 

Peck Television Corp., 33 W. 60th 

St., New York, N. Y. 
PERSE, I. S. (A) 

Capitol Motion Picture Supply Corp., 
630 Ninth Ave., New York, N. Y. 
PETERSEN, F. W. (M) 

I. G. Farbenindustrie Aktiengesell- 
schaft Kinetechnische, Abetiling, 
Berlin, S. O. 36, Germany. 
PFANNENSTIEHL, H. (M) 

Bell Telephone Labs., Inc., 463 West 
St., New York, N. Y. 



Oct., 1934] 



LIST OF MEMBERS 



233 



PHELPS, L. G. (Af) 

Phelps Films, Inc., 27 Harmon St., 

New Haven, Conn. 
PHILLIPS,!. H., JR. (A) 

1455 Gordon St., Hollywood, Calif. 
PIERCE, S. L. (A) 

1813 Penfield St., Philadelphia, Pa. 
PIROVANO, L. (A) 

219 Harvard St., Brookline, Mass. 
PLANSKOY, L. (M) 

142 Camden Rd., London, N. W. 1, 

England. 
POHL, W. E. (A) 

Box 616, Redlands, Calif. 
PONTIUS, R. B. (A) 

Jesus College, Oxford, England. 
POPOVICI, G. G. (M) 

Eastern Service Sound Studios, 
35-11 35th Ave., Long Is' and 
City, N. Y. 
PORTER, C. D. (A) 

869 Parkway Dr., N. E., Atlanta, 

Ga. 
PORTER, G. C. (A) 

Box 1, Wortendyke, N. J. 
PORTER, L. C. (F) 

General Electric Co., Cleveland, 

Ohio. 
PREDDEY, W. A. (A) 

187 Golden Gate Ave., San Francisco, 

Calif. 
PRESGRAVE, C. (A) 

P. O. Box 4372, Chestnut Hill, 

Philadelphia, Pa. 
PRESIDENT, THE (H) 

Deutsche Kinotechnische Gesell- 
schaft, Stallschreiberstr. 33 Hog- 
gachtungsvoll, Berlin, S. W. 19, 
Germany. 

PRESIDENT, THE (H) 
Royal Photographic Society, 35 
Russel Square, London, W. C. 1, 
England. 
PRESIDENT, THE (H) 

Societe Francaise De Photographic, 
Rue De Clichy 51, Paris, 9 EME, 
France. 



PRICE, A. F. (M) 

Bell Telephone Labs., Inc.. 463 West 

St., New York, N. Y. 
PRICE, G. W. (A) 
2406 Montclair Ave., Cleveland, 

Ohio. 
PRINCE, L. S. (A] 

261 Seaman Ave., New York, N. Y. 
Pu, M. N. (A) 

Burmese Favourite Co., 51 Sule 
Pagoda Rd., Rangoon, Burma, 
India. 
PULLER, G. (A) 

32 Park Ave., Port Washington, 
Long Island, N. Y. 

QUICK, C. J. (M) 

49 Vaughan St., Ottawa, Ontario, 

Canada. 
QUINLAN, W. (M) 

Fox Film Corp., 1401 Northwestern 

Ave., Hollywood, Calif. 
QUINN, E. H. (M} 

Hotel Victoria, 785 Seventh Ave., 
New York. N. Y. 



RABINOWITZ, D. J. (4) 

M. Rabinowitz & Sons, Inc., 1373 

Sixth Ave., New York, N. Y. 
RACKETT, G. F. (F) 

Technicolor Mot. Pict. Corp., Box 

1200, Hollywood Station, Calif. 
RAMSAYE, T. (F) 

Motion Picture Herald, 1790 Broad- 
way, New York, N. Y. 
RAMSEY, R. W. (A) 

Carolina Hotel, Winston-Salem, 

N. C. 
RASMUSSEN, R. T. (M) 

Beaded Screen Corp., Roosevelt, 

N. Y. 
RAVEN, A. L. (M) 

Raven Screen Corp., 147 E. 24th 

St., New York, N. Y. 
RAY, R. H. (M) 

Ray-Bell Films, Inc., 817 University 
Ave., St. Paul, Minn. 



234 



LIST OF MEMBERS 



[J. S. M. P. E. 



RAYTON, W. B. (F) 

Bausch & Lomb Optical Co., Roches- 
ter, N. Y. 
READ, E. A. 04) 

1125 Cleveland Ave., N. W., Canton, 

Ohio. 
REEB, O. G. L. (M) 

Rotherstrasse 20-23, Berlin, O. 17, 

Germany. 
REEVES, A. (H) 

Hollywood Mot. Pict. Equip. Co., 
645 N. Martel Ave., Hollywood, 
Calif. 
REIFSTECK, C. N. (F) 

RCA Victor Co., Inc., Camden, N. J. 
REMERSCHIED, H. W. (M) 

907 N. Edinborough, Hollywood, 

Calif. 
RENIER, A. H. 04) 

Renier Mfg. Co., 940 N. 21st St., 

Milwaukee, Wis. 
RENKE, A. 04) 

General Talking Picture Corp., 218 

W. 42nd St., New York, N. Y. 
RENWICK, F. F. (F) 

Ilford Ltd., Ilford, Essex, England. 
REPP, W. H. (M) 

Projection Optics Co., 330 Lyell 

Ave., Rochester, N. Y. 
REYNOLDS, J. L. (M) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
RICHARD, A. J. (M) 

544 W. 43rd St., New York, N. Y. 
RICHARDSON, E. C. (M} 

Mole-Richardson, Inc., 941 N. Syca- 
more Ave., Hollywood, Calif. 
RICHARDSON, F. H. (F) 

3 Tudor Lane, Scarsdale, N. Y. 
RICHMOND, J. 04) 

5725 Windsor Place, Philadelphia, 
Pa. 

RlCHTER, A. 04) 

920 Kelly St., The Bronx, N. Y. 
RICKARDS, H. B. (A) 

2900 E. Grand Blvd., Detroit, Mich. 
RICKER, M. (M) 

39-41 Fifty-Eighth St., Woodside, 
Long Island, N. Y. 



RICKS, H. M. (M) 

Weston Electrical Instrument Corp., 
614 Frelinghuysen Ave., Newark, 
N.J. 

RlNALDY, E. S. (A) 

Chester, N. J. 
RIPLEY, P. L. 04) 

Warner Bros. Pictures, Inc., 1277 E. 

14th St., Brooklyn, N. Y. 
RISEWICK, W. J. (A) 

358 Adelaide St. W., Toronto, On- 
tario, Canada. 
RIST, K. (A) 

3210 Avenue P, Brooklyn, N. Y. 
Rizzo, C. (A) 

255 N. 13th St., Philadelphia, Pa. 
ROCHOWICZ, S. 04) 

Kodak Pathe, Chimielna 29 M. 29, 

Warzawa, Poland. 
ROGERS, J. E. (M) 

"Cluny," Deacons Hill Rd., Elstree, 
Herts, England. 

ROHDE, G. 04) 

Associated Optical Co., 542 S. 

Broadway, Los Angeles, Calif. 
ROLAND, E. C. (A) 

Ilex Optical Co., 726 Portland Ave., 

Rochester, N. Y. 
ROSEMAN, I. (M) 

Kodak, A.-G., Markgrafenstrasse 
7-6, Berlin, Germany. 

ROSENBERGER, H. (F) 

Sandy Hook, Conn. 

ROSENSWEIG, M. (M) 

H. E. R. Labs., Inc., 457 W. 46th St., 
New York, N. Y. 

ROSENTHAL, A. (A) 

Zimmerstrasse 35, Berlin, S. W. 68, 
Germany. 

Ross, A. 04) 

Warner Bros. Pictures, Inc., 1277 E. 

14th St., Brooklyn, N. Y. 
Ross, C. (M) 

Motion Picture Service Co., 318 W, 
48th St., New York, N.Y. 

Ross, C. H. (A) 

1921 Ave. K, Brooklyn, N. Y. 



Oct., 1934] ' 



LIST OF MEMBERS 



235 



Ross, E. (M) 

United Research Corp., 41-39 38th 

St., Long Island City, N. Y. 
Ross, O. A. (M) 

198 Broadway, New York, N. Y. 
ROUSE, J. J (M) 

Kodak Australasia Pty Ltd., 379 
George St., Sydney, N. S. W., 
Australia. 
ROWSON, S. (F) 

62 Shaftesbury Ave., London, W. 1, 

England. 
RUBEN, M. (M) 

Amusement Supply Co., Film Build- 
ing, Detroit, Mich. 
RUBIN, H. (F) 

Paramount Publix Corp., Paramount 

Bldg., New York, N. Y. 
RUBLY, H. C. (A) 

890 Ridgewood Rd., Millburn, N. J. 
RUDOLPH, W. F. (M) 

Paramount Publix Corp., 5451 Mara- 
thon St., Hollywood, Calif. 
Ruox, M. (F) 

Kodak Japan Ltd., Kyobashi P. O. 

Box 28, Tokyo, Japan. 
RUSHWORTH, M. (.4) 

531 South Longwood St., Baltimore, 

Md. 
RUSSELL, K. B. (A) 

3632 Detroit Ave., Toledo, Ohio. 
RUSSELL, W. F. (M) 

Hall & Connolly, Inc., 24 Van Dam 

St., New York, N. Y. 
RUTH, C. E. (A) 

2100 E. Washington St., Pasadena, 

Calif. 
RYAN, H. (A) 

8053 S. Paulina St., Auburn Park 

Station, Chicago, 111. 
RYDER, L. L. (M) 

Paramount Publix Corp., 5451 Mara- 
thon St., Hollywood, Calif. 

SAILLIARD, J. H. (^4) 

Bell Telephone Labs., Inc., 463 West 
St., New York, N. Y. 



SALVING, S. (A) 

2070 E. 22nd St., Brooklyn, N. Y. 
SAMUELS, I. (Af) 

Automatic Devices Co., Hunsicker 

Bldg., Allentown, Pa. 
SANDVIK, O. (F) 

Research Labs., Eastman Kodak Co., 

Rochester, N. Y. 
SANIAL, A. J. (M) 

140-31 58th Rd., Flushing, Long 

Island, N. Y. 
SANTEE, H. B. (M) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
SATTAN, G. D. (A) 

325 Van Hauten Ave., Passaic, N. J. 
SAVINA, J. F. (A) 

7 Jay St., Cambridge, Mass. 
SAUNDERS, R. (M) 

1023 S. Wabash Ave., Chicago, 111. 
SAWYER, J. W. (A) 

14 Groveland Ave., Buffalo, N. Y. 
SCANLON, E. J . (A} 

40 l /2 Lyman St., Holyoke, Mass. 

SCHAEFFER, F. H. (A) 

4129 46th St., Long Island City, 

N. Y. 
SCHEL, H. A. (A) 

G. M. Film, 12 Rue Carducci, Paris, 

France. 

vSCHELDORF, M. W. (^4) 

313 3rd Ave., Haddon Heights, 
N.J. 

SCHLANGER, B. (M) 

70 E. 45th St., New York, N. Y. 
SCHMID, F. (M) 

C. P. Goerz Amer. Optical Co., 317 

E. 34th St., New York, N. Y. 
SCHMIDT, W. A. (F) 

Agfa Ansco Corp., Binghampton, 

N. Y. 
SCHMIDT, W. E. (A) 

Ritz Theatre, Scranton, Pa. 
SCHMINKEY, H. K. (A) 

821 Wellington St., Baltimore, Md. 
SCHMITZ, E. C. (Af) 

Kodak Co., 39 Ave. Montaigne, 
Paris, France. 



236 



LIST OF MEMBERS 



[J.'S. M. P. E. 



SCHMITZ, W. J. U) 

61 Oakdale Blvd., Royal Oak, Mich. 

SCHOONOVER, D. J. (^4) 

234 White Plains Rd., Tuckahoe, 

N. Y. 

SCHROTT, P. R. VON (4) 

Getreidemarkt, 9, Vienna IV, Aus- 
tria. 

SCHWENGELER, C. E. (M) 

34-14 Parsons Blvd., Flushing, Long 

Island, N. Y. 
SCRIVEN, E. O. (F) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
SEASE, V. B. (F) 

DuPont Film Mfg. Corp., Parlin, 

N.J. 
SEIFFERT, S. A. (A) 

P. O. Box 65, Easton, Pa. 
SERRURIER, I. (M) 

Moviola Co., 1451 Gordon St., Holly- 
wood, Calif. 
SHAFER, L. J. (4) 

Rialto Theatre, West 25th St. & 

Bridge Ave., Cleveland, Ohio. 
SHALKHAUSER, E. G. (M) 

147 Cooper St., Peoria, 111. 
SHAPIRO, A. (M] 

Ampro Corp., 2839-51 Northwest- 
ern Ave., Chicago, 111. 
SHEA, T. E. (F) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
SHEARER, B. F. (A) 

2318 2nd Ave., Seattle, Washington. 
SHEPPARD, S. E. (F} 

Research Labs., Eastman Kodak Co., 
Rochester, N. Y. 

SHIRAS, A. (^4) 

841 Ellsworth Ave., Pittsburgh, Pa. 
SHULTZ, E. P. (M) 

1016 No. Sycamore Ave., Holly- 
wood, Calif . 
SILENT, H. C. (F) 

Electrical Research Products, Inc., 
7046 Hollywood Blvd., Los Ange- 
les, Calif . 



SINGER, K. (A) 

229 W. 70th St., New York, N. Y. 
SKITTRELL, J. Y. (M) 

Olympic Kinematograph Labs., 
School Rd., London W. 10, Eng- 
land. 
SMACK, J. C. (A) 

S. S. White Dental Mfg. Co., 152 

West 42nd St., New York, N. Y. 
SMITH, J. E. (M} 

National Radio Institute, P. O. Box 

3046, Washington, D. C. 
SMITH, J. W. (A) 

23 Purley Ave., Cricklewood, Lon- 
don, N. W. 2, England. 
SMOLINSKI, B. P. (A) 

462 E. 48th St., Hollywood, Calif. 
Soi, B. M. U) 

International House, 500 Riverside 

Drive, New York, N. Y. 
SOLOW, S. P. (-4) 

2720 Hudson Boulevard, Jersey City, 

N.J. 
SOPER, W. E. (A) 

P. O. Box 245, Ottawa, Canada. 
SPENCE, J. L., JR. (F) 

Akeley Camera, Inc., 175 Varick St., 

New York, N. Y. 
SPENCER, D. A. (M) 

Murray Bull and Spencer Ltd., 118 
Fulham Rd., London, S. W. 3, 
England. 
SPONABLE, E. I. (F) 

Fox Film Corp., 850 10th Ave.. New 

York, N. Y. 
SPRAY, J.H.(F) 

Warner Bros. Pictures, Inc. 1277 E. 

14th St., Brooklyn, N. Y 
STAFFORD, J. W. (A) 

1237V N. Ogden Dr., Hollywood, 

Calif. 
STECHBART, B. E. (F) 

Bell & Howell Co., 1801 Larchmont 

Ave., Chicago, 111. 
STEDEROTH, F. F. (A) 

41 Watsessing Ave., Bloomfield, 
N.J. 



Oct., 1934] 



LIST OF MEMBERS 



237 



STEELE, L. L. (M) 

S. M. Chemical Co., Inc., 514 W. 

57th St., New York, N. Y. 
STEELY, J. D. (A) 

801 Third St., Marietta, Ohio. 
STEPHAN, C. F. (A) 

7 Mountwell Ave.,Haddonfield, N. J. 
STEPONAITIS, A. (A) 

18 Monrie St., Mount Vernon, N. Y. 
STOLLER, H. M. (F) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
STONE, C. H. (M} 

120 E. Delaware PL, Ft. Dearborn 

St., Chicago, 111. 
STONE, E. C. (4) 

7803 Cedar Brook Ave., Philadel- 
phia, Pa. 
STONE, R. Q. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
STONE, W. P. (A) 
Asheboro, N. C. 
STRICKLER, J. F. (M) 

2900 East Grand Blvd., Detroit, 

Mich. 
STROCK, R. O. (Jlf) 

Eastern Service Studios, Inc., 35-11 
35th Ave., Astoria, Long Island, 
N. Y. 
STRONG, H. H. (F} 

Strong Electric Co., 2501 LaGrange 

St., Toledo, Ohio. 
STRUSS, K. (F) 

1343 North Orange Grove Ave., 

Hollywood, Calif. 
STRYKER, N. R. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
STUBBE, G. (^4) 

1608 S. Michigan Ave., Chicago, 111. 
SUBEDAR, J. C. (A) 

Seva Sadan, Vincent Road, Dadar, 

G. I. P. RQ, Bombay, India. 
SUGUIRA, R. (M) 

R. Konishi & Co., 18 Honcho, 
2-chome, Nihonbashi-ku, Tokyo, 
Japan. 



SUMNER, S. (M) 

University Theatre, Cambridge, 

Mass. 
SUNDE, H. E. (A) 

RCA Victor Co., Inc., Camden, N. J. 

SUTARIA, S. F. (A) 

Saroj Movietone Studio, Amboli 

Road, Andheri, India. 
SWARTZ, E. M. (M) 

Keystone Manufacturing Co., 288 A 

St., Boston, Mass. 
SWIST, T. P. (A) 

306 Lowell St.. Manchester, N. H. 

TANN, W. L. (A) 

3420 89th St., Jackson Heights, 

N. Y. 
TASKER, H. G. (F) 

United Research Corp., 41-39 38th 

St., Long Island City, N. Y. 
TEITEL, A. (^4) 

Protecto Films, Inc., 105 W. 40th St., 

New York, N. Y. 
TERRANEAU, R. (M) 

George Humphries & Co., 10 North- 
court, Chitty St., Tottenham 
Court Rd., London W. 1, England. 
TERRY, R. V. (M) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
THAYER, W. L. (A) 

Paramount Publix Corp., 5451 Mara- 
thon St., Hollywood, Calif. 
THEISEN, W. E. (if) 

809 West 68th St., Los Angeles, 

Calif. 
THOMAS, A. R. (A) 

Princess Theatre, Shelbyville, Term. 
THOMAS, J. L. (4) 

13360 Lauder Ave., Detroit, Mich. 
THOMAS, W. F. (4) 

352 Drexel Ave. S., Detroit, Mich. 
THOMPSON, L. (A} 

B. M. A. Building, Kansas City, Mo. 
THOMPSON, W. S. (A) 

United Research Corp., 41-39 38th 
St., Long Island City, N. Y. 



238 



LIST OF MEMBERS 



[J. S. M. P. E. 



TlLDEN, A. M. (.4) 

1518 Wilder Ave., Honolulu, Hawaii. 
TORNEY, R. G. (A) 

Saraswati Cine tone Co., Walker 
House, Lamington Rd., Bombay, 
4, India. 
TOUZE, G. (M) 

Pathe Pictures Ltd., 103 Wardour 

St., London, W. 1, England. 
TREACY, C. S. (A) 

315 Heathcote Rd., Scarsdale, N. Y. 
TREEN, C. W. (A) 

6726 Sprague St., Philadelphia, Pa. 
TRONOLONE, N. (M) 

1059 Briar Way, Palisade, N. J. 
TSUCHIHASHI, H. (A) 

60 Misono-Machi, Kamata-ku, 

Tokyo, Japan. 
TULPAN, S. (A) 

H. E. R. Labs., Inc., 437 W. 46th St., 

New York, N. Y. 
TUTTLE, C. M. (M) 

Research Labs., Eastman Kodak Co., 

Rochester, N. Y. 
TUTTLE, H. B. (F) 

Eastman Kodak Co., 343 State St., 
Rochester, N. Y. 

UNDERBILL, C. R., JR. (A} 

708 2nd Ave., Westmont, Johnstown, 

Pa. 
UNDERBILL, J. L. (M) 

RCA Photophone Ltd., Film House, 
Wardour St., London, England. 

VAUGHAN, R. (M) 

Filmcraft Labs., 35-39 Missenden 
Rd., Camperdown, Sydney, Aus- 
tralia. 
VENARD, C. L. (A) 

702 S. Adams St., Peoria, 111. 
VENTIMIGLIA, G. (A) 

Via Emanuele Filiberto, 100, Rome, 

Italy. 
VERLINSKY, V. (A) 

Amkino Corp., 723 Seventh Ave., 
New York, N. Y, 



VICTOR, A. F. (F) 

Victor Animatograph Co., 242 W. 
55th St., New York, N. Y. 

VlETH, L. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
VOLCK, G. A. (M) 

9441 Wilshire Blvd., Beverly Hills, 

Hollywood, Calif. 

WADDELL, J. H. (A) 

18 Curtiss Place, New Brunswick, 

N. J. 
WADDINGHAM, A. G. (M) 

Photocolor Corp., Irvington-on-Hud- 

son, N. Y. 
WADE, F. H. (A) 

Warner Bros. Pictures, Inc., 1277 E. 

14th St., Brooklyn, N. Y. 
WAGNER, V. C. (A} 

908 N. 4th Ave., Knoxville, Tenn. 
WAIDE, M. (M) 

General Pictures, Inc., 43-77 Vernon 

Ave., Long Island City, N. Y. 
WALDROP, J. P. (A) 
Lewisburg, Tenn. 
WALL, J. M. (F) 

J. M. Wall Machine Co., 101 Court 

St., Syracuse, N. Y. 
WALL, W. I. (A) 

Mayflower Apts., Joplin, Mo. 
WALLER, F. (M) 

R. F. D. No. 2, Huntington, Long 

Island, N. Y. 
WALTER, H. L. (-4) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
WALTER, O. L. (A) 

Bell Telephone Labs., Inc., 463 West 

St., New York, N. Y. 
WALTERS, H. (A) 

136 N. Windsor Ave., Atlantic City, 

N.J. 
WARD, E. J. (M) 

Eastman Kodak Company, Kodak 
Park, Rochester, N. Y, 



Oct., 1934) 



LIST OF MEMBERS 



239 



WARD, J. S. (F) 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
WARMISHAM, A. (F) 

Bell & Howell Co., 4045 N. Rockwell 

St., Chicago, 111. 
WASCHNECK, K. (M) 

Aktiengesellschaft fur Film Fabrika- 
tion, Victoria Strasse 13/18, Ber- 
lin, Tempelhof, Germany. 
WATKINS, R. H. (A) 

R. H. Watkins Co., P. O. Box 233, 

Winona, Minn. 
WATKINS, S. S. A. (F) 

Western Electric Co., Bush House, 
Aldwych, London, W. C. 2, Eng- 
land. 
WATSON, E. M. (A) 

Lamp Development Labs., General 

Electric Co., Cleveland, Ohio. 
WATSON, J. S., JR. (F) 

6 Sibley Place, Rochester, N. Y. 
WEBER, C. M. (F) 
Weber Machine Corp., 55 Bengal 

Terrace, Rochester, N. Y. 
WEIL, N. (A) 

P. O. Box 1472, Atlanta, Ga. 
WELMAN, V. A. (M} 

207 Finance Bldg., Cleveland, Ohio. 
WENTE, E. C. (F) 

Bell Telephone Labs., Inc., 463 West 
St., New York, N.Y. 

WENZ, A. (A) 

Warner Bros. Pictures, Inc., 1277 E. 

14th St., Brooklyn, N. Y. 
WERNLEIN, C. E. (A) 

P. O. Box 74, Malverne, Long Island, 

N. Y. 
WESTON, J. C. (A) 

66-20 53rd Ave., Maspeth, Long 

Island, N. Y. 
WESTWATER, W. (M} 

Research Labs., Eastman Kodak 

Co., Rochester, N. Y. 
WHITE, D. R. (F) 

Redpath Labs., DuPont Film Mfg. 
Corp., Parlin, N. J. 



WHITMORE, W. (M) 

Western Electric Co., 195 Broadway, 

New York, N. Y. 
WILD, G. (M) 

22 rue Cambaceres, Paris, France. 
WILDING, N. E. (M) 

7635 Grand River Blvd., Grand 

River, Mich. 
WILDUNG, F. H. (M) 

708 Butternut St., N. W., Washing- 
ton, D. C. 

WlLLARD, T. W. (A) 

Five Center Knolls, Bronxville, N. Y. 
WILLIAMS, S. B. (A) 

366 Clermont Ave., Brooklyn, N. Y. 
WILLIAMSON, T. H. (A) 

18 Priory Court, West Hampstead, 

London, N. W. 6, England. 
WILLIFORD, E. A. (F) 

National Carbon Co., Box 400, 

Cleveland, O. 
WILLMAN, R. C. (M) 

RCA Victor Co., 1016 N. Sycamore 

Ave., Hollywood, Calif. 
WILMOT, H. T. (A) 

Craig Movie Supply Co., 1031 S. 

Broadway, Los Angeles, Calif. 
WILSON, C. K. (M) 

Warner Bros. Pictures, Inc., 1277 E. 

14th St., Brooklyn, N. Y. 
WILSON, S. K. (A) 

12 Whitehall Rd., Harrow Middx., 

England. 
WILZCEK, L. A. (A) 

Carbon Products, Inc., 324 W. 42nd 

St., New York, N. Y. 
WINN, C. B., JR. (A) 

421 East "J" St., Ontario, Calif. 

WlNTERMAN, C. (M) 

Topical Film Co., Ltd., Brent Labs., 
North Circular Rd., London, 
N. W. 2, England. 
WISE, A. G. (M) 

8970 Kelson Ave., Los Angeles, 
Calif. 

WlSSMANN, J. (A} 

Rockland Ave., New Springville, 
Staten Island, N. Y. 



240 



LIST OF MEMBERS 



WOLCOTT, E. A. (Af) 

2065V4 Hillhurst Ave., Hollywood, 

Calif. 
WOLF, S. K. (A} 

Electrical Research Products, Inc., 
250 W. 57th St., New York, N. Y. 
WOLFERZ, A. H. (Af) 

Weston Electrical Instrument Corp., 
614 Frelinghuysen Ave., Newark, 
N.J. 

WORSTELL, R. E. (A) 

General Electric Co., Cleveland, O. 
WRATTEN, I. D. (F) 

Kodak Ltd., Kingsway, London, 

England. 
WRIGHT, A. 04) 

Palais Pictures, St. Kilda, Mel- 
bourne, Australia. 

YAGER, H. B. (Af) 

61 Morton St., New York, N. Y. 
YASUI, S. 04) 

Katabiragaoka Usuniasa Ukyoku, 
Kyoto, Japan. 



YATES, E. C. (A\ 

Post Box 564, Singapore, S. S. 
YOUNG, H. A. (A) 

818 55th St., Brooklyn, N. Y. 

ZATORSKY, E. F. (A) 

Seward Hotel, Seward Ave., Detroit, 

Mich. 
ZAUGG, A. (A) 

1830 Ridgeley Dr., Los Angeles, 

Calif. 
ZEPPELIN, H. V. (A) 

Western Electric Co. of Spain, Plaza 

de Cataluna, Barcelona, Spain. 
ZERK, O. U. (Af) 

3206 Palmolive Bldg., Chicago, 111. 
ZIEBARTH, C. A. (Af) 

Bell & Howell Co., 1801 Larchmont 

Ave., Chicago, 111. 
ZOELTSCH, W. F. (A) 

Box 73, Main Office, Union City, 

N.J. 
ZUBER, J. G. (Af) 

Bell & Howell Company, 1801 Larch- 
mont Ave., Chicago, 111. 



FALL CONVENTION 

HOTEL PENNSYLVANIA, NEW YORK, N. Y. 
OCTOBER 29-NOVEMBER 1, 1934 

CONVENTION ARRANGEMENTS COMMITTEE 

W. C. KUNZMANN, Chairman 
H. GRIFFIN J. H. KURLANDER M. W. PALMER 

LOCAL ARRANGEMENTS COMMITTEE 

H. GRIFFIN, Chairman 

J. O. BAKER J. H. KURLANDER H. RUBIN 

A. S. DICKINSON O. F. NEU T. E. SHEA 

O. M. GLUNT M. W. PALMER J. H. SPRAY 

PROJECTION COMMITTEE 

H. GRIFFIN, Chairman 

F. E. CAHILL, JR. J. FRANK, JR. M. D. O'BRIEN 

G. C. EDWARDS H. F. HEIDEGGER H. RUBIN 

Officers and Members of New York Local No. 306, I.A.T.S.E. 
LADIES' COMMITTEE 

MRS. O. M. GLUNT, Hostess 

Assisted by 

MRS. G. C. EDWARDS MRS. J. H. KURLANDER MRS. M. W. PALMER 

MRS. H. GRIFFIN MRS. M. D. O'BRIEN MRS. O. F. NEU 

MRS. J. FRANK, JR. MRS. E. I. SPONABLE 

OPENING OF CONVENTION 

The Convention will begin at 10:00 A.M., Monday, October 29th, at the Hotel 
Pennsylvania, in the Salle Moderne, on the eighteenth floor. At noon of the 
opening day there will be an informal get-together luncheon, during which the 
members of the Society will be addressed by several prominent speakers. The 
morning preceding the luncheon will be devoted to registration, Society business, 
and reports of technical committees. 

SESSIONS 

Technical sessions and film programs will be held in the Salle Moderne, adjacent 
to which will be located the registration headquarters. The sessions will be held 
on the mornings of Monday, Tuesday, Wednesday, and Thursday; and on the 
afternoons of Monday, Tuesday, and Thursday. Wednesday afternoon, pre- 
ceding the semi-annual banquet, will be devoted to visits to various laboratories, 

241 



242 FALL CONVENTION 

studios, theaters, and equipment and instrument manufactories in the New York 
area. The film programs of recently produced outstanding features and shorts 
will be held on Monday and Tuesday evenings. Interesting semi-technical lec- 
tures by well-known scientists will also be presented on those evenings preceding 
the film programs. Mr. J. I. Crabtree, Convention Vice-President, and Mr. J. O. 
Baker, Chairman of the Papers Committee, are in charge of the technical program . 

HALLOWE'EN BANQUET AND DANCE 

The S. M. P. E. Semi-Annual Banquet and Dance will be held in the Grand 
Ballroom of the Hotel on Wednesday, October 31st, at 7:30 P.M. an evening of 
dancing, movies, and entertainment. Several addresses will be made by eminent 
members of the motion picture industry. Banquet tickets should be obtained in 
advance at the registration headquarters: tables reserved for six or eight persons. 

HOTEL RATES 

Excellent accommodations are assured by the management of the Hotel, and 
minimum rates are guaranteed. Room reservation cards mailed to the member- 
ship of the Society should be returned immediately in order to be assured of satis- 
factory reservations. Special garage rate, $1.25. 

European Plan 

Single: $3.50 per day; one person, single bed. 
Double: $5.00 per day; two persons, double bed. 
Double: $6.00 per day; two persons, twin beds. 

LADIES' HEADQUARTERS 

A reception suite will be provided for the ladies attending the Convention, and 
an attractive program for their entertainment is being prepared by the Ladies' 
Committee. 

EXHIBIT OF MOTION PICTURE APPARATUS 

Arrangements are being made to conduct an exhibit of newly developed motion 
picture apparatus, in order to acquaint the members of the Society with the newly 
devised tools of the industry. The exhibit will not be of the same nature as the 
usual trade exhibit; there will be no booths, but each exhibitor will be allotted 
definite space, and all exhibits will be arranged in a single large room. Requests 
for space should be directed to the General Office of the Society at the Hotel 
Pennsylvania, New York, N. Y., stating the number and nature of the items to be 
exhibited. The charges for space will be as follows : up to 20 sq. ft., $10; every 
additional 10 sq. ft.. $5. 

W. C. KUNZMANN, Convention Vice-President 
J. I. CRABTREE, Editorial Vice-President 



SOCIETY ANNOUNCEMENTS 
FALL CONVENTION 

As announced in the preceding section of this issue of the JOURNAL, the Fall, 
1934, Convention will be held at the Hotel Pennsylvania, New York, N. Y., 
October 29th-November 1st. Members are urged to make every effort to at- 
tend the Convention, and to participate in the very attractive and interesting 
programs that are being arranged. 

ELECTION OF OFFICERS FOR 1935 

Ballots for voting for the 1935 officers of the Society were recently mailed to 
the voting membership of the Society, and will be counted on October 29th, 
the first day of the Fall Convention. The names of the successful candidates will 
be announced at that time, but officers-elect will not assume office until January 
1st, in accordance with the provisions of the recent revision of the Constitution 
and By-Laws. 

PROJECTION PRACTICE COMMITTEE 

At a meeting held at New York, N. Y., on September 12th, an outline of the 
report to be presented at the forthcoming Convention was prepared. At the 
next meeting of the Committee, to be held on October 24th, the draft of the report, 
based on the outline, will be edited by the Committee and put into final shape. 

JOURNAL AWARD COMMITTEE 

In accordance with an enactment of the Board of Governors on April 22, 1934, 
the JOURNAL Award was revived. It consists of a cash award of $50, accompanied 
by an appropriate certificate to the author or authors of the "most outstanding 
paper originally published in the JOURNAL during the preceding calendar year." 

The Committee will report its findings to the Board of Governors at the next 
meeting, October 28th, and the award will be made some time during the Con- 
vention beginning on the following day. 

STANDARDS 

An up-to-date revision of the Standards Booklet, including all the standards 
that have been approved by the Society up to the present moment, and upon 
which the Standards Committee has been working for almost two years, will be 
ready for publication in the next issue of the JOURNAL. In addition to being 
published in the JOURNAL, reprints will be available shortly after. 

The plan of changing the standardization of motion picture projects from the 
proprietary method to the administrative sectional committee method, sponsored 
by the S. M. P. E., according to the procedure of the American Standards As- 
sociation, has been approved by the Standards Council of the latter body. 

Plans for forming the Sectional Committee are going forward, and the 
S. M. P. E. Board of Governors at its next meeting on October 28th will take 
whatever steps may be necessary to enable the Committee to begin its work. 

243 



STANDARD S. M. P. E. 

VISUAL AND SOUND TEST REELS 

Prepared under the Supervision 

OF THE 
PROJECTION PRACTICE COMMITTEE 

OF THE 
SOCIETY OF MOTION PICTURE ENGINEERS 



Two reels, each approximately 500 feet long, of specially pre- 
pared film, designed to be used as a precision instrument in 
theaters, review rooms, exchanges, laboratories, and the like 
for testing the performance of projectors. The visual section 
includes special targets with the aid of which travel-ghost, 
lens aberration, definition, and film weave may be detected 
and corrected. The sound section includes recordings of 
various kinds of music and voice, in addition to constant 
frequency, constant amplitude recordings which may be used 
for testing the quality of reproduction, the frequency range 
of the reproducer, the presence of flutter and 60-cycle or 96- 
cycle modulation, and the adjustment of the sound track. 
Reels sold complete only (no short sections). 

PRICE $37.50 FOR EACH SECTION, 
INCLUDING INSTRUCTIONS 

(Shipped to any point in the United States) 

Address the 

SOCIETY OF MOTION PICTURE ENGINEERS 

HOTEL PENNSYLVANIA 
NEW YORK, N. Y. 



JOURNAL 

OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 

Volume XXIII NOVEMBER, 1934 Number 5 



CONTENTS 

Page 
Standards Adopted by the Society of Motion Picture Engineers 247 

Stroboscopic-Light High-Speed Motion Pictures 

H. E. EDGERTON AND K. J. GERMESHAUSEN 284 

A Sweep Oscillator Method of Recording Wide Frequency-Band 
Response Spectra on Short Lengths of Motion Picture Film . 

J. CRABTREE 299 

Program of the Fall Convention at New York 302 

Society Announcements 305 



JOURNAL 

OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 



SYLVAN HARRIS, EDITOR 

Board of Editors 
J. I. CRABTRBB, Chairman 

O. M. GLUNT A. C. HARDY L. A. JONES 

J. O. BAKER 



Subscription to non-members, $8.00 per annum; to members, $5.00 per annum, 
included in their annual membership dues; single copies, $1.00. A discount 
on subscriptions or single copies of 15 per cent is allowed to accredited agencies. 
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton 
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y. 

Published monthly at Easton, Pa., by the Society of Motion Picture Engineers 

Publication Office, 20th & Northampton Sts., Easton, Pa. 
General and Editorial Office, Hotel Pennsylvania, New York, N. Y. 
Entered as second class matter January 15, 1930, at the Post Office at Easton, 
Pa., under the Act of March 3, 1879. Copyrighted, 1934, by the Society of 
Motion Picture Engineers, Inc. 

Papers appearing in this Journal may be reprinted, abstracted, or abridged 
provided credit is given to the Journal of the Society of Motion Picture Engineers 
and to the author, or authors, of the papers in question. Exact reference as to 
the volume, number, and page of the Journal must be given. The Society is 
not responsible for statements made by authors. 



Officers of the Society 

President: ALFRED N. GOLDSMITH, 444 Madison Ave., New York, N. Y. 
Executive Vice-President: HAROLD C. SILENT, 7046 Hollywood Blvd., Los 

Angeles, Calif. 

Engineering Vice-President: LOYD A. JONES, Kodak Park, Rochester, N. Y. 
Editorial Vice-President: JOHN I. CRABTREE, Kodak Park, Rochester, N. Y. 
Financial Vice-President: OMER M. GLUNT, 463 West St., New York, N. Y. 
Convention Vice-President: WILLIAM C. KUNZMANN, Box 400, Cleveland, Ohio. 
Secretary: JOHN H. KURLANDER, 2 Clear-field Ave., Bloomfield, N. J. 
Treasurer: TIMOTHY E. SHEA, 463 West St., New York, N. Y. 

Governors 

EUGENE COUR, 1029 S. Wabash Ave., Chicago, 111. 
ARTHUR S. DICKINSON, 28 W. 44th St., New York, N. Y. 
RALPH E. FARNHAM, Nela Park, Cleveland, Ohio. 
HERBERT GRIFFIN, 90 Gold St., New York, N. Y. 
EMERY HUSE, 6706 Santa Monica Blvd., Hollywood, Calif. 
WILBUR B. RAYTON, 635 St. Paul St., Rochester, N. Y. 
HOMBR G. TASKER, 41-39 38th St., Long Island City, N. Y. 



STANDARDS ADOPTED BY THE 
SOCIETY OF MOTION PICTURE ENGINEERS 

The preceding edition of this booklet, known as the "Standards Adopted by the 
Society of Motion Picture Engineers," published originally in J. Soc. Mot. Pict. 
Eng., XIV (May, 1930), No. 5, p. 545, and approved by the American Standards 
Association September 20, 1930, contained the first fifteen of the following 
charts. Although in this revised edition of the booklet some of those charts have 
been superseded, they have been retained for purposes of reference, the original chart 
numbers being unchanged. Some of the changes involved new dimensions, whereas 
others involved merely a new and clearer presentation of the existing dimensions; in 
any case, the captions following the chart numbers indicate the new charts to be 
consulted. 

The present revision of the booklet was completed by the Standards Committee 
in October, 1934, with the addition of Charts 16 to 32, inclusive. 

DIMENSIONAL STANDARDS 

1. Dimensions of Newly Cut and Perforated Film. 

(a) Standard 3 5 -mm. film. 

Chart 16, for positive and negative stock; super- 
seding Charts 1 and 2. See also Chart 23. 

(b) Standard 2 8 -mm. film. (Not in general use.) 

Chart 3. 

(c) Standard 16 -mm. film. 

Chart 17, for positive and negative film; super- 
seding Chart 4. See also Chart 27. 

2. Perforations. 

(a) Standard 3 5 -mm. film. 

A single style of perforation shall be used for all 
35-mm. film, to be the same as the perforation known 
prior to July 14, 1933, as the standard positive per- 
foration, and to be known thereafter as the standard 
S. M. P. E. perforation. See Charts 16 and 23. 

N. B. Readers of the JOURNAL are invited to submit comments on this re- 
port to the General Office of the Society. 

247 



248 STANDARDS OF THE SOCIETY [J. S. M. P. E. 

3. Film Splicing Specifications, for Laboratories and Exchanges. 

(a) 35-Mm. film. 

Chart 18, superseding Chart 5. 

(b) 16-Mm.film. 

Chart 12. 

4. 35-Mm. Projector Sprockets. 

(a) Take-up sprocket. 

Chart 19, superseding Chart 6. The take-up 
sprocket, which is a hold-back sprocket in the motion 
picture projector, should have the same pitch as the 
perforations of film that has shrunk to the maximum 
extent found in films supplied by exchanges in a 
commercially useful condition. Such shrinkage is 
accepted as 1.5 per cent, for which value the dimen- 
sions given in the chart were computed. 

(b) Intermittent and feed sprockets. 

Chart 19, superseding Chart 7. The intermittent 
and feed sprockets should have the same pitch as the 
perforations of film that has shrunk 0.15 per cent, for 
which value the dimensions given in the chart were 
computed. The transverse distance between sprocket 
teeth has been calculated on the bases of film shrink- 
age of 1.13 per cent maximum. 

5. 16-Mm. Projector Sprockets. 

(a) Feed sprockets. 

Chart 20, superseding Chart 8. 

(b) Take-up (hold-back) sprockets. 

Chart 21, superseding Chart 9. 

(c) Combination sprockets. 

Chart 22, superseding Chart 10. 

6. Width of Film Track in 16-Mm. Cameras and Projectors. 

A clearance of 0.005 inch (0.13 mm.) shall be 
allowed in designing the film track in cameras and 
projectors. 



Nov., 1934] STANDARDS OF THE SOCIETY 249 

7. Frame Line. 

(a) Standard 35-mm. film. 

The center of the frame line shall be midway be- 
tween two successive perforations on each side of the 
film. 

(b) Standard 16-mm. film. 

The center of the frame line shall pass through the 
center of a perforation on each side of the film. 

8. Camera and Projector Apertures. 

(a) Standard 35-mm. film. 

Charts 23, 24, and 25. 

(b) Standard 16-mm. film. 

Charts 11, 27, 28, and 29. 

9. Scanning Beam and Sound Track. 

(a) Standard 35-mm. film. 

Charts 23 and 26, superseding Charts 13 and 14. 

(b) Standard 16-mm. film. 

Charts 27 and 30. 

10. Sound Film Speed. 

(a) Standard 35-mm. film. 

24 Frames per second. 

(b) Standard 16-mm. film. 

24 Frames per second. 

11. Sound Record Relative to Picture Aperture. 

For 35-mm. sound film, the center of any picture 
shall be 20 frames farther from the beginning of the 
reel than the corresponding modulation of the sound- 
track. In other words, the "sound start" mark shall 
be twenty frames nearer the beginning of the reel 
than the "picture start" mark. 

For 16-mm. sound film, the center of any picture 
shall be 25 frames farther from the beginning of the 



250 STANDARDS OF THE SOCIETY [j. s. M. P. E. 

reel than the corresponding modulation of the sound- 
track. The "sound start" mark shall be 25 frames 
nearer the beginning of the reel than the "picture start" 
mark. 

12. External Diameter of Projection Lenses. 

(a) No. 1 projection lens. 

External diameter of lens barrel 2Vs2 inches 
(51.59 mm.). 

(b) No. 2 projection lens. 

External diameter of lens barrel 2 25 / 32 inches 
(70.65 mm.). 

13. Lantern Slide Mat Opening. 

3.0 Inches (76.20 mm.) wide, by 2.35 inches (59.69 
mm.) high. 

14. Unit of Photographic Intensity. 

The unit of photographic intensity adopted by the Inter- 
national Congress of Photography in 1933 shall be adopted 
for negative materials. 

DEFINITIVE SPECIFICATIONS 

1. Number of Teeth in Mesh. 

The number of teeth in mesh with the film (commonly 
referred 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 Chart 15 

2. Safety Film. 

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) support 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) un- 



Nov., 1934] STANDARDS OF THE SOCIETY 251 

coated 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 Underwriters Labora- 
tory. 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 thickness and width at 
which the particular material is used in practice. 

RECOMMENDED PRACTICE 

1. Leaders and Trailers. 

The Standard Release Print adopted by the Academy of 
Motion Picture Arts and Sciences in 1930 is shown in Chart 
32 (Seventh revision; April 1, 1934). Manufacturers of 
sound film should place a leader on each roll of film, on 
which is designated the framing of the picture and the cor- 
responding sound. 

2. Thumb Mark. 

The thumb mark on a lantern slide should be located in 
the lower left-hand corner adjacent to the reader when the 
slide is held so that it can be read normally against the light. 

3. Projection Lens Height. 

The standard height from the floor to the center of the 
projection lens of a motion picture projector should be 48 
inches. 

4. Projection Angle. 

This should not exceed 12 degrees. 

5. Observation Port. 

Observation ports should be 12 inches wide and 14 inches 
high and the distance from the floor to the bottom of the 



252 STANDARDS OF THE SOCIETY [j. S. M. P. E. 

openings shall be 48 inches. The bottom of the opening 
should be splayed 15 degrees downward. In cases where 
the thickness of the projection room wall exceeds 12 inches, 
each side should be splayed 15 degrees. 

6. Projector Lens Mounting. 

The projector lens should be mounted in such a manner 
that the light from all parts of the aperture shall traverse an 
uninterrupted path to the entire surface of the lens. 

7. Projection Lens Focal Length. 

The focal length of motion picture projection lenses should 
increase in l / 4 -inch steps up to 8 inches, and in V2-inch steps 
from 8 to 9 inches. 

8. Project on Objectives, Focal Markings. 

Projection objectives should have the equivalent focal 
length marked thereon in inches, quarters, and halves of an 
inch, or in decimals, with a plus (+) or minus () tolerance 
not to exceed 1 per cent of the designated focal length also 
marked by proper sign following the figure. 

9. Sensitometry. 

The principle of non-intermittency shall be adopted as 
recommended practice in making sensitometric measure- 
ments. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



253 



. STANDARD 35 M / M NEGATIVE FILM 
CvniKSat' '-^795"_^ .65* 




.1 



tf 



/ 



CUTTING & 



SIZE.. 



CHART 1. Superseded April, 1934, by Chart 16. 



254 



STANDARDS OF THE SOCIETY [J. S. M. p. E. 



STANDARD 35 M / M POSITIVE FILM 



CUTTING-SIZE. 



1.57735" 



/.3759Q 




q 

cj 
-ED" 



q 
a 
a 



(34.35V.) 



T 



(l 5.375%) 

L..L 



a 

"JD 

b 

b 

H- 

.w 

f3-- 

b 
P 

P 

a 
o 



ALTERNATIVE. 



APPROX. 



. f ] -^g s^ 

' ; I JJ5 ii: 

k/70-H I 
G?.73'%) 



(5%) 



CUTTINGS, PERFORATING SIZE. 



CHART 2. Superseded April, 1934, by Chart 16. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



255 



SAFETY STANDARD 28 M / M POSITIVE 
AND NEGATIVE FILM 



f^llTTIM^ ^/7f 


1.10256 


, i 


L UTTING O/Zc 


1.10053" 

" 


r. 




-F5 O 


i 


i 


i 

o! !o 

O! JO 


.1' 




bj jo 

o! !o 
i i 


~T 




o a 



3 





APPKOX. 
(.38/7',) 



(i.m.) 
CUTTING PERFORATING S/zc. 



CHART 3. (Not in general use.) 



256 



STANDARDS OF THE SOCIETY [j. S. M. p. E. 



STANDARD 16 M / M POSITIVE AND 
NEGATIVE FILM 



CUTTING SIZE rH^ 



.62795 



o o 

o 

Or ------- 



O O 

O 

o 



(167*,} 
(15.95%,) 






(f&49%) 

DIOl'RAD.-^^ 

APPROX. 
(.57%) L 



-J^U 

(/.829%) 

CUTTING & PERFORATING SIZE. 



CHART 4. Superseded April, 1934, by Chart 17. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



257 



NEGATIVE AND POSITIVE SPLICES 



NEGATIVE SPLICE 



, 



^ 



o 



_ 

7 7 / 77'/S7/S7?/77/ 77/77/77'/77/77/77'//7?/77/77//7/'/77/S7'//77/ 



o 
o 



'-7/J7/M 



PICTURE FRAME LINE. 




i 



FULL HOLE POSITIVE SPLICE 



PICTURE FRA ME L INE. 




7 



CHART 5. Superseded April, 1934, by Chart 18. 



258 



STANDARDS OF THE SOCIETY [j. s. M. p. E. 



TAKE-UP (HOLD-BACK) SPROCKET 

16 TEETH /v _u. ^ 35 % FILM 




-.9521 BASED/A: 
1.032 



APPROX..OIO"RAD. (/. 



r 



I. I 07' TOOTH GAUGE. 

(28.12%) 




~A 




CHART 6. Superseded April, 1934, by Chart 19. 



Nov., 1934] STANDARDS OF THE SOCIETY 



259 



INTERMITTENT AND FEED SPROCKETS 

16 TEETH ^ ^A-^ 35% FILM 




\ 



\ 



-9452 BASE D/A.- 

(24.01%) 
1.044 



-\ * 004 lt~^~ 

ROUND CORNERS .075 RAD. }/o%) 

^ooony nin"0Ar> (/W\ ^V u/atl i. 



APPRO/.. 010 RAD. (ts/%) 



/ 107 TOOTH GAUGE 



m 




CHART 7. Superseded April, 1934, by Chart 19. 



260 



STANDARDS OF THE SOCIETY 



[J. S. M. p. E. 



16 M /M FILM 
STANDARDIZED SPROCKET SIZES 



F&D SPROCKETS 



.050R. 



\ 1 
/^STT 

Q 


NUMBER OF TCTH/N CONTACT WITH FILM. 


a 


3 


4 


D' 

INCHR 


t 

INCHK 


RANGE 

OTOMAX. 
SHfllltKASL 


D' 

INCHES 


t 

INCHES 


RANGE 

OTOMAX. 

SHRIMML 


D' 

INCHES 


t 

INCUR 


RANGE 
To MAX. 

SumKt 


NaSmcKcrTecni 


5 


4714 


039 




1.547. 


4714 


034 



7.573 








040 


.035 


6 


3663 


039 



1.54% 


5663 


034 



1.57% 


5669 


.030 



1.52% 


D40 


035 


031 


7 


6624 


039 



1.547. 


6624 


.034 



1.577. 


6624 


mo 



1.527. 


040 


D35 


(031 


8 


7579 


033 
040 



1.547. 


7573 


D34 



1.577. 


7579 


030 



1.52% 


.035 


031 



/ROUND CORNERS 
APPBOX..OOS"RAO, 



048- 

r\ 
1 




CHART 8. Superseded April, 1934, by Chart 20. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



261 



16 M / M FILM 
STANDARDIZED SPROCKET SIZES 



UP (HOLD BA CK) 
05OR. 



4( > 
1\_A 


NUMBEROFTKTH IN CONTACT WITH FILM 


2. 


3 


4 


D' 

/NCHCS 


t 

It/CHCS 


PAN<? 

SHRIHKASL 


D 

INCHES 


t 

IHCKK 


PAW 

SHRINMSt. 


D 

INCHES 


t 

INCH& 


RANGE 

SWWAX 


NO.SPmCKTT[TH 


5 


4643 


037 
038 


/.50% 


4643 


.051 
.032 



1.50% 








6 


6584 


037 
058 



1.50% 


$584 


031 
032 



/.50% 


5564 


030 
03/ 



/.50% 


7 


6524 


.037 
038 



1.50% 


6514 


.031 
.032 



t.50% 


6524 


030 
,03/ 



/.60% 


8 


7464 


037 
038 



t.50% 


7464 


.031 
.032 



{.50% 


7464 


030 
03/ 



/.60% 



/ROUND CORNERS 
APPRO*.. 005"#AD. 



r 



048 

r\ 



1 




CHART 9. Superseded April, 1934, by Chart 21. 



262 



STANDARDS OF THE SOCIETY 



[J. S. M. P. E. 



16 M / M FILM 
STANDARDIZED SPROCKET SIZES 



COMB/NATION SPROCKETS 



.QSOR. 



K )} 


NUMBER OFTEETH IN CONTACT WITH HLM. 


2 


3 


4 


D' 

/MCHCS 


t 

INCHES 


RANGE 

SHRHKW. 


D' 

INCHES 


t 

INCHES 


RANGE 

SHRIW& 


D 1 

INCHES 


t 

iHCHtS 


RANGE 

Smwst 


NaSppocKcrTtCTH 




5 


4691 


.042 



1.55% 


4691 


.039 



1.52% 








.045 


.040 


6 


5641 


042 



1.55% 


5641 


039 



1.52% 


5641 


036 



/.52% 


.043 


040 


037 


7 


6591 


.042 



/.55% 


6591 


039 



J.52% 


6591 


.036 



1.52% 


.043 


040 


051 


8 


7541 


.042 



1.55% 


1541 


039 



1.52% 


7541 


036 



1.52% 


.043 


040 


057 



r 



/ROUND CORNERS 
APPRO*. OOS'ffAD. 



048 

r\ 





CHART 10. Superseded April, 1934, by Chart 22. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



263 



STANDARD 
16 M / M APERTURES 



PROJECTOR 









3.65 m /m t 



0380" 



CAMERA 



M 



0.41 



0./009 



CD 


O'C* 



M 



10.41 



0.41 



Z79 m lm 



0.1003 



CHART 11. See also Charts 27, 28, and 29. 



264 



STANDARDS OF THE SOCIETY 



[J. S. M. P. E. 



16 M / M FILM SPLICES 

DIAGONAL SPLICE 




00 



STRAIGHT SPLICE 




CHART 12 



Nov., 1934 J 



STANDARDS OF THE SOCIETY 



265 



POSITION AND DIMENSION OF 


SCANNING LINE 


1 


-.OSOH'.OSO'H 

- -.100"-^ 


OUlPtV E-WCrfc. 




SOU 


NP 




. 




TRACK 








ARE.A 








SCANNWG LIKE. L 
\ 




















MAX.-001 f jjj^ 

kos 
c.u. or SOUWP "^ 


^ ,., 






.E43 




TRACK AREA I 












AMP OF [ 












5CAMN\NG UtAE. J 











1 




/l^ 








GUIPING EPGE 




OF SOUNP GATE 





CHART 13. Superseded April, 1934, by Charts 23 and 26. 



266 



STANDARDS OF THE SOCIETY [j. s. M. p. E. 



SOUND TRACK ON 35 M / M SOUND AND 
PICTURE POSITIVE 




CHART 14. Superseded April, 1934, by Charts 23 and 26. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



267 



NUMBER OF TEETH IN MESH 




CHART 15. 



268 



STANDARDS OF THE SOCIETY 



[J. S. M. p. E. 



STANDARD 35-MM. 


FILM 


CUTTING AND PERFORATING DIMENSIONS 


OF NEGATIVE AND POSITIVE RAW STOCK 


These dimensions and tolerances apply to the material im- 


mediately after cutting and perforating. 
^s\ 






pX V/^^x-^^xX^- 

CD 


^ v^V 

o 
















c 


D 






1 D 




c 


^ 


D 






< 


c 


D 






-i -4 




"1 




-ty- -j- 






L 




1 G 






L> 






-- 


^ 


t. 


{ 


T^R 








F 
T~ 


_Lu 

|_ , 1 ^f^^ 


C 

^^~ ^^. 


D 




l v ~\ ~^r ^-v. x -. x 

HEK 


x ^^^- 


Indus 


Millimeter* 


A 1.378 + 0.000 


35.00 + 0.00 


- 0.002 


- 0.05 


B 1.109 0.002 


28.17 0.05 


C 0.134 0.002 


3.40 =*= 0.05 


D 0.187 0.0005 


4.75 0.013 


E 0.110 =*= 0.0003 


2.79 0.008 


F 0.078 0.0003 


1.98 0.008 


G Not > 0.001 


Not > 0.025 


R 0.020approx. 


0.51 approx. 


L* 18-70 0.015 


475.0 == 0.381 


* L = the length of any 100 consecutive perforation intervals. 



CHART 16. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



269 



These die 
mediately a 

i_ 


STANDARD 16-MM. FILM 

CUTTING AND PERFORATING DIMENSIONS 
OF NEGATIVE AND POSITIVE RAW STOCK 

aensions and tolerances apply to the 
r ter cutting and perforating. 

C) D 

A ~~ 


material im- 


G 


/-i 




C 

3- 


i .J 


-E 

-e 

f ^~ 


J 7 
G 


D 

1 


F 


(_ 




x 




T~ 


1 .^-^ 


qTF - 


Inches 


Millimeters 


A 0.630 + 0.000 
- 0.002 
B 0.485 =*= 0.001 
C 0.072 0.002 
D 0.300 0.0005 
0.072 0.0002 
F 0.050 0.0002 
G Not > 0.0005 
R . 010 approx. 
L* 30.0 =t 0.03 


16.00 + 0.00 
- 0.05 
12.32 0.025 
1.83 0.05 
7.62 0.013 
1.83 0.005 
1.27 0.005 
Not > 0.013 
0.25 approx. 
762.0 0.76 


* L = the length of any 100 consecutive perforation intervals. 



270 



STANDARDS OF THE SOCIETY 



[J. S. M. P. E. 



35-MM. FILM SPLICES 



NEGATIVE SPLICE 




REGULAR POSITIVE SPLICE 



O'v. 




o 







Q i Projct< 



FULL HOLE POSITIVE SPLICE 




Splice 



aoso* 

.91 MM 



Splice 



J07Z 
1.83 MM 



Splice 



.156" 
3.9b MM 



CHART 18. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



271 



STANDARD 35-MM. SPROCKETS 

PROJECTOR FEED AND HOLD-BACK SPROCKETS 

(Not Sound Sprockets) 

16 TEETH 






Feed Sprocket 


Int. Sprocket 


Hold-Back Sprocket 




Inches 


mm. 


Inches 


mm. 


Inches 


mm. 


A 


1.097 .001 


27.86 .025 


1.097 .001 


27.86 .025 


1.097 .001 


27.86 .025 


B 


.945 .001 


24.00 .025 


.945 .0002 


24.00 .005 


.932 .001 


23.67 .025 


C 


.935 .002 


23.75 .051 


.935 .002 


23.75 .051 


.922 .002 


23.42 .051 


D 


1.045 .002 


26.54 .051 


1.045 .002 


26.54 .051 


1.032 .002 


26.21 .051 


R 


.055 + .000 


1.4 +.000 


.055 + .000 


1.4 +.000 


.055 + .000 


1.4 +.000 




- .002 


- .051 


- .002 


- .051 


- .002 


- .051 


F 


.040 .002 


1.02 .051 


.040 .002 


1.02 .051 


.040 .002 


1.02 .051 


G 


.055 + .000 


1.4 +.000 


.055 + .000 


1.4 +.000 


.055 + .000 


1.4 +.000 




-.002 


- .051 


- .002 


.051 


- .002 


- .051 


H 


.139 + .000 


3.531 + .000 


.139 + .000 


3.531 + .000 


.139 + .000 


3.531 + .000 




-.001 


- .025 


- .001 


-.025 


- .001 


- .025 


K 


22 Deg. 30 Min. 1.5 Min. 


22 Deg. 30 Min. .75 Min.* 


22 Deg. 30 Min. 1.5 Min. 



* The accumulated error over 16 teeth not to exceed 4.00 min. 

Note. -The center about which the tooth radius is drawn is located 0.004" 
below the periphery of the drum. 



=0.0002' 



CHART 19. 



272 



STANDARDS OF THE SOCIETY 



[J. S. M. P. E. 



STANDARD 16-MM. SPROCKETS 

FEED SPROCKETS 

(Not Sound Sprockets) 

.050" 






Number of Teeth in Mesh 


3 


4 


5 


6 


AT 


D' 


t 


t 


t 


t 


t 


/ 


t 


t 








in. 


mm. 


in. 


mm. 


in. 


mm. 


in. 


mm. 




in. 




















6 


0.566 


14.38 


0.040 


1.02 














8 


0.757 


19.23 


0.040 


1.02 


0.036 


0.91 










12 


1.139 


28.93 


0.040 


1.02 


0.036 


0.91 


0.031 


0.79 


0.027 


0.69 


16 


1.521 


38.63 


0.040 


1.02 


0.036 


0.91 


0.031 


0.79 


0.027 


0.69 



R = Round corners with approximately 0.005" radius 

N = Number of teeth on sprocket. 

Tolerances for D' and t = +0.000", -0.001". 

Maximum allowable film shrinkage = 1.50%. 

Values given for D' are 0.001" less than he theoretical. 

Values of t are not given in cases where the number of te?th in mzsn as related 
to N, the number of teeth on the sprocket, is such that the wrap of the film on 
the sprocket would be greater than 180. 



CHART 20. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



273 



STANDARD 16-MM. 


SPROCKETS 


TAKE-UP (HOLD BACK) SPROCKETS 


( Not Sound Sprockets} 


.050" 




A 


/\XJ*\ 


^ 

A 


/* 




^ 


^ f Tl 


*-==^ 


r 


l 




IT " 


Jo48 


.4 

n I2> ' 


81" H 
22% 














1 1.22% F M 












^ 










1 












i 


'///\ y/fi, 




v/fflfyfflfflfr 






_^ 1 




\j 


















Number of Teeth in Mesh 






3 


4 5 


6 


D 1 


t t 


t 


t t i 


\ t t 


N 




in. 


mm. 


in. mm. in. 


mm. in. m 


*n. in. mm. 


6 0.557 


14.15 


0.040 1.02 






8 0.745 


18.92 


0.040 1.02 0.036 


0.91 




12 1 . 122 


28.50 


0.040 1.02 0.036 


0.91 0.031 0. 


79 0.027 0.69 


16 1.498 


38.05 


0.040 1.02 0.036 


0.91 0.031 0. 


79 0.027 0.69 


R = Round corners with approximately 


0.005" radius. 




N = Number of teeth on sprocket. 


Tolerances 


for D' and t = +0.000", -0. 


001". 




Maximum 


allowable film shrinkage = 1.50%. 


Values given for D 


' are 0.001" less than the theoretical. 


Values of t are not given in cases where the number of teeth in mesh as related 


to N, the number of teeth on the sprocket, is 


such that the wrap of the film on 


the sprocket would be greater than 180. 



CHART 21. 



274 



STANDARDS OF THE SOCIETY 



[J. S. M. p. E. 



STANDARD 16-MM. SPROCKETS 

COMBINATION SPROCKETS 

(Not Sound Sprockets) 

.050" 
1.27% 






Number of Teeth in Mesh 


3 


4 


5 


6 


N 


D' 


t 
in. 


t 
mm. 


t 
in. 


t 
mm. 


t 
in. 


/ 
mm. 


/ 

in. 


t 
mm. 


in. 


mm. 


6 
8 
12 
16 


0.563 
0.753 
1.133 
1.513 


14.30 
19.13 
28.78 
38.43 


0.043 
0.043 
0.043 
0.043 


1.09 
1.09 
1.09 
1.09 


0.040 
0.040 
0.040 


1.02 
1.02 
1.02 


0.037 
0.037 


0.94 
0.94 


0.034 
0.034 


0.86 
0.86 



R Round corners with approximately 0.005" radius. 

N = Number of teeth on sprocket. 

Tolerances for D' and t = +0.000", -0.001". 

Maximum allowable film shrinkage = 1.50%. 

Values given for D' are 0.001" less than the theoretical. 

Values of t are not given in cases where the number of teeth in mesh as related 
to N, the number of teeth on ttiz sprocket, is such that the wrap of the film on 
the sprocket would be greater than 180. 



CHART 22. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



275 



STANDARD 35-MM. SOUND FILM 

CAMERA APERTURE, PROJECTOR APERTURE, AND SCANNED AREA 

These dimensions and locations are shown relative to unshrunk 
raw stock. Positive; emulsion side up. Negative; emulsion 
side down. 



.134 
3.40M/1 




Camera Aperture Perforation 



In the camera the emulsion side of the film faces the objective, 
from the objective the sound track is to the left. 

In the projector the emulsion side of the film faces the light source, 
from the light source the sound track is to the right. . 



Projector Aperture 

Viewed 
Viewed 



CHART 23. 



276 



STANDARDS OF THE SOCIETY 



[J. S. M. p. E. 



STANDARD 35-MM. SOUND FILM 


CAMERA APERTURE 


These dimensions and locations are shown relative to unshrunk 


raw stock. Negative; emulsion side down. 


<t of Camera Aperture 






1 >^ J x 
r~ll 


^y ^~ ' 

J n 


Guided 












Edqe 


C_) 




u 






* 


D fc 
^ 






-f- 






A-* a 


Travel 


















a 








B 








n 


I 


, m 






c 


*R 






_J(J ^-^^ 


1 U 




l^tof Film 


a> = b = l /2 longitudinal perforation pitch. 




Inches 


Millimeters 


A 


0.868 


22.05 


B 


0.631 


16.03 


C 


0.117 


2.97 


D 


0.744 


18.90 


R 


0.031 


0.79 


In the camera the emulsion side of the film faces the objective. Viewed 


from the objective the sound track is to the 


left. 



CHART 24. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



277 



STANDARD 35-MM. SOUND FILM 

PROJECTOR APERTURE 

These dimensions and locations are shown relative to unshrunk 
raw stock. Positive; emulsion side up. 

C of Projtctor Aptriur* fc 


T 


f T 

( 1 1 


^/ 


x- 


T^ 
* a 


^Guided 


V ; 


f' 






Edo|e 
Travl 


' 




r\ 




V 

A- 


a 








i 


n - 


B 


\ 

Q 


a 

> o 


i ) 


C 




S. 




a = b 


^-L - 






-^r 

= l /2 longitud 


Jfc of Film 


inal perforation pitch. 




Inches 


Millimeters 


A 

B 
C 
D 
R 


0.825 
0.600 
0.147 
0.738 
0.047 


20.96 
15.24 
3.73 
18.74 
1.19 


In the projector the emulsion side of the film faces the light source. Viewed 
from the light source the sound track is to the right. 



CHART 25. 



278 



STANDARDS OF THE SOCIETY 



[J. S. M. P. E, 



STANDARD 35-MM. SOUND FILM 

SOUND RECORDS AND SCANNED AREA 

These dimensions and locations are shown relative to unshrunk 
raw stock. Positive ; emulsion side up. The dimensions as shown 
include the necessary allowance for film weave. 



\fJidth of Sound fecora 
100*1 Modulation 



VARIABLE WIDTH 

AND 
VARIABLE DENSITY 




.30f1f1 



CHART 26. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



279 



STANDARD 16-MM. SOUND FILM 

CAMERA APERTURE, PROJECTOR APERTURE, AND SCANNED AREA 

These dimensions and locations are shown relative to unshrunk 
raw stock. Positive; emulsion side up. Negative; emulsion 
side down. 



Film 
t Cam 
t Proj 


.072" 
L43MAI 

> 
orfi Aoprt \ 


< 


. "TF^r 


7?-a 

Camen 


vel 
y Apert. 


C 








; 


I 


|| 


ectorApert) 


a 


'*^ 
8 


F^ 


~ ~ "N" 






i 

j. 


^ 




fitQ * 








t ^j 

L^aU-4 


^ 

^ 
/ 

/ 

/ 
/ 


1 




/7^ c" 






/ 

y 
/ 
y 




n9/^" 




Projector Apert. 

-i Guided Edge 
ots" 


"1 

s 

8 


N 

K 

IK 


l i 


" TT 

i 






JT 


-***. 


^^^ ( 


Scanned Area 




/.65 MM 
.056" 


(Posrtive Film) *" 


U7 MH 




.4/0" 


., 


10.41 nn 


.51 HM \ 





Projector Aperture 



Perforation 



Camera Aperture 



In the projector the base (not emulsion) side of the positive, made either 
by the reversal process or by optical printing from 35-mm. negatives, or from 
negatives produced by optical printing from 35-mm. film, faces the light source. 
Viewed from the light source, the sound track is to the left. 

The emulsion side of the films used for color systems employing lenticulated 
film processes or screen-plate processes, and contact prints made from original 
16-mm. negatives, must face the light source. 



CHART 27. 



280 



STANDARDS OF THE SOCIETY 



[J. S. M. P. E 



STANDARD 16-MM. SOUND FILM 

CAMERA APERTURE 

These dimensions and locations are shown relative to unshrunk 
raw stock. Negative; emulsion side down. 



pf Camera Aperture 




a = b = 1 / 2 perforation pitch. 





Inches 


Millimeters 


A 
B 
C 
R 


0.410 
0.294 
0.006 
0.020 


10.41 
7.47 
0.15 
0.51 



In the camera the emulsion side of the film faces the objective. Viewed 
from the objective the sound track is to the right. 



CHART 28. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



281 



STANDARD 16-MM. SOUND FILM 

PROJECTOR APERTURE 

These dimensions and locations are shown relative to unshrtmk 
raw stock. Positive; emulsion side up. 

of Projector Aperture 



Guided 




Edge 



Travel 



a = b = l / 1 perforation pitch 





Inches 


Millimeters 


A 
B 
C 
R 


0.380 
0.284 
0.016 
0.020 


9.65 
7.21 
0.41 
0.51 



In the projector the base (not emulsion) side of the positive, made either 
by the reversal process or by optical printing from 35-mm. negatives, or from 
negatives produced by optical printing from 35-mm. film, faces the light source. 
Viewed from the light source, the sound track is to the left. 

The emulsion side of the films used for color systems employing lenticulated 
film processes or screen-plate processes, and contact prints made from original 
16-mm. negatives, must face the light source. 



CHART 29. 



282 



STANDARDS OF THE SOCIETY 



[J. S. M. P. E- 



STANDARD 16-MM. FILM 

SOUND RECORDS AND SCANNED AREA 

These dimensions and locations are shown relative to unshrunk 
raw stock. Positive; emulsion side up. 




VARIABLE DENSITY 
W/Cttn Of 



Sound Record 



.53 MM 
.O&o" 



203 MM 
tof 



Scanned Area 



VARIABLE WIDTH 

AND 

VARIABLE DENSITY 




In the projector the base (not emulsion) side of the positive, made either 
by the reversal process or by optical printing from 35-mm. negatives, or from 
negatives produced by optical printing from 35-mm. film, faces the light source. 
Viewed from the light source, the sound track is to the left. 

The emulsion side of the films used for color systems employing lenticu- 
lated film processes or screen-plate processes, and contact prints made from 
original 16-mm. negatives, must face the light source. 



CHART 30. 



Nov., 1934] 



STANDARDS OF THE SOCIETY 



283 



16-MM. SOUND FILM 

Non-recommended Specification 

CAMERA APERTURE, PROJECTOR APERTURE, AND SCANNED AREA 

These dimensions and locations are shown relative to unshrunk 
raw stock. Positive ; emulsion side up. 



JQ7Z* r 
1.63 MM 

Film 


m 


-- 


IfcMM ( 
.4.6S" 


[IZ.32 MM 
I0.49MM)- 
.315- 


)- 

* 


* 


..07Z' 
1.63 MM 

TRAV 

^Guided Edqe 


fl 


1 Camera Apert 








8MM 






c 










1 


D 


^J 1347" 




/ \ 


jg 


8.81 MM 
I 


r 
/ 


D 


Camera Apert. 


F 




~i t 


1 


r v 


' 


r 




.03 fe 




< 


015" 


X>72 
OOI 


H 










/ ^ 




.03(> 






1 


^ 

^ 


i 


OT?" 






J 




Projector Apert. 





"A 


- 




X 
.9 


r 
>3tf 1 

ImT 


9- 




"o 

8 


1 
1 
1 


t Scanned Area 


- ^~ 


n 


(Positive Film) 




_c 


D^: 


j 

-^ 

n" 





^o 



.347" 



6.61 MM 




Camera Aperture 



Perforation 



Projector Aperture 



In the projector the base (not emulsion) side of the positive, made either 
by the reversal process or by optical printing from 35-mm. negatives, or from 
negatives produced by optical printing from 35-mm. film, faces the light 
source. Viewed from the light source, the sound track is to the left. 

The emulsion side of the films used for color systems employing lenticulated 
film processes or screen-plate processes, and contact prints made from original 
16-mm. negatives, must face the light source. 



CHART 31 



STROBOSCOPIC-LIGHT HIGH-SPEED MOTION PICTURES* 
H. E. EDGERTON AND K. J. GERMESHAUSEN** 

Summary. A discussion of various methods of producing motion pictures at 
speeds higher than at present attainable with intermittent mechanisms; followed by 
a description of a high-speed motion picture camera (1200 frames a second, on 
35-mm. film) using intermittent light from mercury-arc stroboscope lamps developed 
at the Massachusetts Institute of Technology. Several examples of the use of the 
lamp are given. 

The development of the motion-picture camera provided an ex- 
cellent means for recording the motions of objects and for reproducing 
them whenever desired. Furthermore, it provided a means of chang- 
ing the time-scale so that actions too slow to be seen in life (like the 
growth of a flower) or too fast (like the splash of a drop of liquid) 
might be projected upon the screen at such a rate that the eye would 
be able to see and the mind to comprehend. The usual type of 
intermittent-motion camera, when carefully designed and con- 
structed, is able to take pictures at rates up to about 200 per second. 
Motion pictures taken at 200 frames per second and projected at 16 
per second portray on the screen the motion of the subject slowed 
down by a factor of about 12.5 times. 

The value of high-speed photography in its varied forms has long 
been recognized. From 1878, when Muybridge 1 first used a number 
of cameras tripped in succession to study the action of running horses, 
to the present day there has been a steady effort to develop photo- 
graphic technic to enable one to see and record events too quick for 
the eye. 

For many subjects the number of pictures per second attained by 
intermittent mechanisms is sufficient. Slow-motion pictures taken 
at such speeds have proved valuable for making time-motion studies 
of people doing production work, recording the winners of races, 
studying the movements of athletes, and for measuring the actions of 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Massachusetts Institute of Technology, Cambridge, Mass. 
284 



STROBOSCOPIC-LIGHT PICTURES 285 

machinery. There are, however, many problems that require a far 
greater speed than is practicable with the intermittent-type of cam- 
era, and a great deal of thought and effort has been applied to speed 
up the camera mechanism. Intermittent mechanisms were aban- 
doned for speeds above about 200 frames per second because of the 
mechanical difficulties involved in accelerating the film between pic- 
tures, and cameras that employed film moving at a constant speed 
were designed. 

There are two general methods of making exposures on a continu- 
ously moving film: 

(1) Those employing a moving optical system, which holds the image sta- 

tionary with respect to the film during the exposure time. 

(2) Those employing a source of stroboscopic light, the flashes of which are 

of sufficiently brief duration to produce a sharp image on a moving film. 

High-speed motion-picture cameras have been constructed utiliz- 
ing one or the other of the two methods, or both. Each method has 
advantages and disadvantages, which must be carefully considered 
with respect to the particular problem at hand. The first type of 
camera 2 ' 3 - 4 ' 5 ' 6 is especially adapted to studying subjects that produce 
their own light or are brightly illuminated, common examples of which 
are the burning of vapors, the action of explosives, the movements 
of an electric arc, the reactions in a photoflash lamp, and many others. 
The stroboscopic-light type of camera is of very limited use in the 
study of such problems. 

The principal advantage of the stroboscopic-light type of cam- 
era 7 ' 8 ' 9 ' 10 over the moving-optical-system type is that the exposure 
time may be made so short as effectively to stop the motion of rapidly 
moving objects. The stroboscopic light in its present state of de- 
velopment makes an exposure of a few millionths of a second, which 
is considerably shorter than is feasible by the moving-optical-system 
method; especially because as long an exposure as possible is usually 
desired in the moving-optical-system method in order to attain suf- 
ficient density of image on the film. In high-speed cameras employ- 
ing stroboscopic light, the film is moved past the lens at a constant 
speed; and each time the film has moved the distance occupied by 
one frame, the subject is illuminated by a short brilliant pulse of 
light. The time at which the flash occurs is controlled by a com- 
mutator rigidly attached to the film-driving mechanism, and the 
duration of the flash is so short that no appreciable blurring of the 
picture occurs. Normal illumination such as that encountered in- 



286 H. E. EDGERTON AND K. J. GERMESHAUSEN [J. S. M. P. E. 

doors is insufficient to fog the film in a stroboscopic-light camera be- 
cause the film passes the lens so rapidly. 

When motion pictures are taken at high speed with any type of 
camera* the film must move rapidly, and one of the important 
problems in the design of either type of cameras is to make the film 
travel at the requisite speed without vibrating, fluttering, or break- 
ing. The rapidly moving film must be guided properly, but the 
friction in sliding contacts may generate enough heat to ignite it. 
Static charges of electricity resulting from the friction must also be 
avoided, as they cause dendriform exposures on the film. Further 
than simply traveling smoothly at a high speed, it is important that 
the film accelerate rapidly so that it will attain the proper speed be- 
fore much of it has passed through the camera. The acceleration 
must be uniform as well as rapid, as sudden jerks are likely to break 
the film. 

TABLE I 

Speed of Film in Terms of Frame Height and Rate of Exposure 

Frame Exposures per Second 

Height, 500 1000 2000 4000 8000 16,000 32,000 64,000 

(inches) Film Velocity (Ft. per Sec.) 

0.75 31.25 62.5 125.0 250 500 1000 2000 4000 

0.30 6 12.50 25.0 50.0 100 200 400 800 1600 

0.15 6.25 12.5 25.0 50 100 200 400 800 

0.075 3.175 6.25 12.5 25 50 100 200 400 



a Standard 35-mm. frame height. 
6 Standard 16-mm. frame height. 

The height of the frame as well as the rate of making exposures is 
a factor influencing the film speed, since it is not necessary for the 
film to move as rapidly for a small frame as for a large one. Most 
of the very high-speed pictures are small in size, in some cases so 
minute as to be of little use in presenting detail even after enlarge- 
ment. Conversely, if the film speed is increased in order to produce 
larger pictures, the camera becomes so bulky that it is no longer port- 
able, and the subjects must be brought to the camera a serious 
limitation to its usefulness. Table I shows the speed of the film in 
feet per second as a function of the height of the frame and the num- 
ber of exposures per second. 

* Possible exceptions are those high-speed cameras employing stationary film 
and a large number of lenses, 11 or a number of spark sources of light (method of 
Cranz, 8 described by Ende 6 ). 



Nov., 1934] SxROBOSCOPIC-LlGHT PICTURES 287 

When film speeds higher than about 150 or 200 ft. per sec. are de- 
sired, the film is usually placed on the periphery of a drum. 3 ' 4 - 7 ' 8 ' 9 
The length of film that can be used is limited to the circumference of 
the drum, but very high film velocities can be attained in this way 
more easily than with a long strip. There are no acceleration prob- 
lems, since the film may be brought up to speed as slowly as desired. 
Cameras of this type require a shutter that remains open during one 
revolution only, to prevent multiple exposure of the film. 

In motion picture photography a certain amount of blurring of 
the images of moving objects is desirable, since the blurring produces 
the proper impression to the eye when the pictures are projected. If, 
however, the pictures are to be used to obtain scientific or engineering 
data from a frame-by-frame study, then maximum sharpness is de- 
sirable. 

The exposure time of cameras employing a moving optical system 
usually is from one-half to two-thirds of the time elapsing between 
successive frames, although in some cameras the exposures may be 
longer than the interval between the pictures, as described by Jen- 
kins. 2 It is possible to design the optical system for short exposure, 
but this leads to the difficulty of lighting the subject adequately. 
Light of high intensity is accompanied by heat, which may prove 
detrimental to the subject. Shadow or silhouette photographs are 
often employed for high-speed motion pictures, because the amount 
of light required is much less than that required for taking photo- 
graphs by reflected light. However, this technic has its limitations, 
because the arrangement of the subject or the character of the re- 
sults desired may often prevent its being employed. 

The exposure time for the stroboscopic-light camera is usually 
less than Vioo.oooth of a second. It can not be made longer, as the 
motion of the film during exposure would blur the picture. Pictures 
taken with the stroboscopic-light camera will never for that reason 
show a moving object blurred by the motion of the object, except for 
such very high velocities as are attained by bullets or for close-ups 
of very rapidly moving subjects. The heat of the stroboscopic light 
is less than of a continuous light, as the light is extinguished between 
exposures. 

A stroboscopic light that has been extensively used is the electric 
spark in air 7 ' 8 ' 9 produced when an electrical condenser discharges 
into an open air-gap. The duration of the flash can be made as short 
as Vi,ooo,oooth of a second, or less. A spark-gap, however, pre- 



288 H. E. EDGERTON AND K. J. GERMESHAUSEN [J. S. M. p. E. 

sents serious problems when it is desired to produce enough light to 
illuminate an area two or three feet square 1000 or more times a 
second, because of the great power required and the difficulty of con- 
trolling it. Although a spark is not an efficient source of light, it 
is sufficient for some purposes. The light is highly concentrated, 
having a high intrinsic brilliancy which permits the use of reflectors 
and condensing lenses. 

The discharge of electrical condensers through mercury lamps 
has proved a very useful source 10 of intermittent light, since they 
may be easily and accurately controlled, and the light produced by 
them is very actinic. The lamp is connected to a condenser and is 
made to flash at the desired instant by charging an external grid to 
a suitable potential. The voltage is produced by a pulse amplifier 
by means of which a large amount of power in the lamp can be con- 
trolled by a very small pulse. Any number of lamps may be con- 
nected in parallel and all flashed at the same instant, making it pos- 
sible to build up the desired amount of illumination. The lamps 
used at present have a light-duration time of from one to ten micro- 
seconds, and may be flashed as often as 6000 times a second with 
suitable control circuits. 

A Stroboscopic-Light High-Speed Camera. Fig. 1 shows a strobo- 
scopic-light camera for taking high-speed motion pictures on continu- 
ously moving film, developed at the Massachusetts Institute of 
Technology. The camera is simple in construction, consisting of a 
supply reel, a take-up reel, and one large sprocket. The supply reel 
is at the top, the film passing down over the sprocket to the take-up 
reel at the bottom. The reels are interchangeable, and have a core 
diameter of 2 l / 2 inches and an outside diameter of 4V 2 inches, with 
a film capacity of 135 feet. The core diameter was made larger 
than usual in order to reduce the speed of rotation and to lessen the 
difference between the speed of the full and that of the empty reel. 

Because of the difficulty of decelerating the moving parts, no at- 
tempt has been made to stop the film after part of it has been exposed. 
All the film is run through for each shot, the length that is used de- 
pending upon the subject. Either 16-mm. or 35-mm. film can be 
used in the camera, since reels and sprockets are available for both 
sizes and are interchangeable. The camera in Fig. 1 is equipped with 
35-mm. reels and sprocket, the 16-mm. equipment lying next to the 
camera. An appropriate aperture plate and lens mount are also 
available for both sizes of film, 



Nov., 1934] SXROBOSCOPIC-LIGHT PICTURES 289 

The drive for the camera was designed with two objects in view: 
first, to accelerate the film rapidly; and, second, to move the film at 
a constant speed after the acceleration period. Two motors are 
used, one being a series motor connected directly to the take-up reel, 
and the other an induction motor belted to the sprocket shaft. The 
function of the series motor is to take up the film as it comes from the 
sprocket, and also to assist the other motor in pulling the moving 
parts of the camera up to speed quickly. A series motor is especially 
adapted to drive the take-up reel, because it has a large starting 
torque and a drooping speed- torque characteristic. The second 




FIG. 1. Continuously moving-film type of high-speed 
motion picture camera constructed at the Massachusetts 
Institute of Technology for use with stroboscopic light. 

motor is a three-phase induction motor rated at 3600 rpm., */4 hp- 
It is connected to the sprocket shaft by means of a F-belt, which 
affords a convenient means of changing the speed by using different 
pulleys. Experiment shows that when double voltage is applied to 
both the motors, the film accelerates to a speed of 75 ft. per sec. 
while 10 feet of film pass through the camera. At that speed the 
camera takes 1200 35-mm. or 3000 16-mm. frames per second. 

The film does not slide through a gate or against any stationary 
part in the camera, because friction at such high speeds would gener- 



290 H. E. EDGERTON AND K. J. GERMESHAUSEN [J. S. M. p. E. 

ate heat and electrostatic charges. The camera shown in Fig. 1 is 
constructed in such a manner that during exposure the film lies against 
a large moving sprocket instead of against a gate. The sprocket must 
be large enough to prevent the curvature of the film from throwing 
the image appreciably out of focus, but not so large as to introduce 
difficulties in acceleration or to make the camera bulky and awkward. 
A consideration of those and other factors leads to a compromise, 
resulting in a sprocket of about 5 inches in diameter with twenty 
35-mm. frames around its periphery; or, in the case of 16-mm. film, 
fifty frames. An aluminum roller is pressed by a spring against the 
sprocket in order to force the film down to the base of the teeth as it 
comes from the supply reel. A metal plow is located at the bottom 
of the sprocket to peel off the film from the teeth in case the take-up 
motor should not exert enough pull. 

Two square holes cut into the sprockets conveniently permit lining 
up the camera and adjusting the focus, since a clear view of the image 
cast by the lens on the film may be viewed through the film from the 
back. A telescope is mounted through the rear of the camera in 
such a way as to afford an enlarged view of the center of the frame 
for finally adjusting the focus critically just before starting the camera. 

The location of the pictures on the film is determined by the po- 
sition of the film at the instant the stroboscopic lights flash. For 
satisfactory projection the pictures must be accurately and definitely 
located with respect to the sprocket holes ; so, to accomplish this, a 
commutator is located on the same shaft as the sprocket, having as 
many contacts as there are frames around the sprocket. In order 
to eliminate vibration, the commutator must be carefully and ac- 
curately made, so that the segments are uniform and the surface is 
smooth. Only a small amount of power is needed to trip the electri- 
cal circuits, and therefore the brush may be light in construction. 
The brushes are adjusted when the camera is at rest, as there is no 
appreciable time-lag in the electrical circuits after the brush makes 
contact. 

The source of stroboscopic light that has made this type of 
camera possible consists of mercury-arc tubes through which elec- 
trical condensers are discharged. Its important properties are: (1) 
the light is actinic; (2) the discharge time is short; (3) the timing 
of the flashes may be accurately controlled by a small amount of 
power; (4) the tubes are relatively simple; and (5) as many tubes 
may be operated in parallel as desired. 



Nov., 1934] 



SXROBOSCOPIC-LIGHT PICTURES 



291 



Fig. 2 is the wiring diagram of the stroboscope. A polyphase 
rectifier unit supplies about 10 kw. of power at 1000 volts to charge 
the condensers. In series with each condenser is a resistor large 
enough to limit the current from the source of power at the instant 
of discharge, but still small enough to allow the condenser to charge 
for the succeeding flash. 

The power required to operate a camera of the stroboscopic type 
depends upon the subject being photographed The size and color 
of the subject are the primary factors that determine the amount of 
light necessary for each exposure. The power is, of course, propor- 
tional to the number of exposures per second. The number of ex- 
posures required depends upon the degree to which it is desired to 
slow down the motion. To illuminate an area of a few square feet 




FIG. 2. Wiring diagram of stroboscopic lighting source for taking high- 
speed pictures. 

with subjects of fairly light color requires a bank of at least four 12- 
inch tubes with condensers of 2 microfarads' capacity connected to 
each, charged to 1000 volts. At 1200 flashes per second nearly 10 
kilowatts of power are required to operate this bank of lamps. 

The circuit diagram of the pulse amplifier is shown in the lower 
part of Fig. 2. The operation is as follows: The commutator on 
the camera has narrow segments that close the circuit so marked at 
the right of the diagram. The grid of the thyratron, an FG-67 tube, 
is thus made positive for a few microseconds. Energy stored in the 
condenser C then discharges through the primary of the step-up 
transformer T. The high potential induced in the secondary of T 
is led to external starting bands or grids on the mercury-lamp tubes 



292 H. E. EDGERTON AND K. J. GERMESHAUSEN [J. S. M. p. E. 

at the junction of the mercury and the glass. Such a high potential 
applied suddenly at that point starts a cathode spot in the liquid 
mercury where it touches the glass, which supplies the electron emis- 
sion for the large peak currents in the mercury-arc stroboscope tube. 
Immediately after the condenser C discharges through the trans- 
former and thyratron, a negative bias appears upon the grid of the 
thyratron, which thus regains control. Between flashes the con- 
densers throughout the circuit accumulate charges, so that they are 
prepared for the next flash. 

Uses of High-Speed Motion Pictures, and Examples. The most 
obvious use of the high-speed camera is for taking motion pictures 
of fast or complicated motions in order that they may be slowed 
down, when projected on the screen, to such a speed that the eye is 
able to see and the mind to comprehend. Subsequent showings often 
bring out obscure but important details that were not noticed during 
previous projections. The motion picture can be kept for reference 
to refresh the memory or as a record of the motion at the particular 
time of the exposure. 

A second use of the high-speed motion picture camera, perhaps 
more important than the first for engineering purposes, is its ability 
to permit making measurements of position as a function of time. 
The individual frames of the moving-picture film record the instan- 
taneous position and form of the object being photographed with 
time interval between frames depending upon the rate at which the 
camera is run. The stroboscopic-light camera, when used for .such 
work, may be arranged so that the time between flashes is accurately 
determined by a constant-frequency source of power instead of by 
the synchronizing commutator on the camera. The advantage of 
using an accurately timed flashing light lies in the fact that the speed 
of the film does not enter into the measurements. Needless to say, 
the pictures can not be projected, as they are not placed in the proper 
relationship to the sprocket holes. However, should it be desired 
to project them, they may be thrown upon a screen with respect to a 
stationary reference, and recopied frame by frame. 

The velocity of a moving object may be determined from a motion 
picture film by measuring the difference in the position of the image 
between two successive frames and dividing by the time interval be- 
tween the pictures. The accuracy of the results is influenced both 
by the accuracy of measurement of the displacement and the accuracy 
of determination of the time interval. Usually the former involves 



Nov., 1934] 



STROBOSCOPIC-LIGHT PICTURES 



293 



the larger error because of the difficulty of measuring the displace- 
ment on account of the smallness of the pictures, the blur if the ex- 
posure is long, and the size of the silver grains. The film shrinks as 
it ages, so that the photographs should have a distance reference 
upon them in order that the result of the measurement may be inde- 
pendent of the state of the film. The accuracy of determining the 
velocity is improved by taking close-up pictures, showing greater 
displacements between images. 
The short exposure time of the 
stroboscopic light is especially 
advantageous for velocity 
measurements, since the pic- 
tures are not blurred by motion 
of the object during exposure. 

Acceleration measurements 
follow from the velocity de- 
terminations, since the accelera- 
tion is the change of the 
volocity with time. The slope 
of the velocity-time curve is 
therefore the acceleration, and 
the accuracy of the measure- 
ment depends upon the ac- 
curacy of measurement of 
velocity and time, and the ad- 
ditional difficulty of measuring 
the slope of the curve. 

A very good example to illus- 
trate the method of measuring 
velocities is the analysis 13 of a 
golf stroke. Fig. 3 is a series 
of pictures taken at a rate of 
960 per second. The velocities 

of the ball and club are obtained by measuring the displace- 
ment between pictures and then multiplying by 960. Measure- 
ments of displacement by means of a comparator permit the 
determination of the velocities of the club and ball, both be- 
fore and after impact, with an accuracy of about 2 per cent. An 
analysis of the photograph shown as Fig. 5 resulted in the following 
data: 




FIG. 3. Enlarged section of 35-mm. 

film made for the measurin g velocities 
of golf clu ^ and ball Interval of time 

between pictures, 1 / 96 o second. 



294 H. E. EDGERTON AND K. J. GERMESHAUSEN [J. S. M. P. E. 

Club velocity just before impact 151 ft. /sec. 

Club velocity just after impact 113 ft./sec. 

Ball velocity 186 ft./sec. 

Spin of the ball 5000 r.p.m. 

As the mass of the ball and the club-head are known, there is suf- 
ficient information to calculate the energy lost by the club-head and 
the energy gained by the ball, as well as to calculate the energy 
stored in rotation. In addition, the pictures show definitely that 
the ball and club are in actual contact for less than Vioooth of a 
second, since the impact occurs during the interval between pictures. 




FIG. 4. Camera in position for taking silhouette pictures of index 
pointer on the pendulum of a Charpy impact-testing machine. 



It is not possible to measure the accelerations of the club and ball 
from these pictures, since the acceleration of the ball was completed 
between frames. 

The Charpy impact machine for testing materials has been studied 
by high-speed pictures taken at 6000 per second. Fig. 4 shows the 
camera arranged to take silhouette pictures of the impact pendulum. 
The arrangement of the light and camera is similar to that used by 
Bull 7 and Cranz 9 and offers many advantages in problems where a 
silhouette is sufficient. The depth of field is very great, correspond- 
ing to that obtained by a pinhole, and the utilization of light is ef- 



Nov., 1934] STROBOSCOPIC-LIGHT PICTURES 295 

ficient. The light source for the set-up shown in Fig. 4 is a spark 
gap, with brass electrodes spaced about 1 mm. The gap is connected 
in series with a mercury lamp which, besides timing the instant of 
flash, also acts as a rectifier to prevent the current from oscillating 
in the gap, as it normally does. A 1 / 2 -microfarad condenser charged 
to 1000 volts in this case furnished sufficient light to produce a good 
density on positive film with an exposure time of about 10 ~ 6 second. 
Fig. 5 shows some of the 6000-per-second pictures of a stationary 
reference point and a pointer on the moving pendulum. The pictures 
are only 8 mm. high, but extend across the entire 35-mm. frame, 
permitting the motion of the pendulum to be followed over a greater 
portion of its swing. 

A few preliminary experiments have 
been made with a bow and arrow, using 
the high-speed camera to determine 
velocities and accelerations of the arrow. 
The arrow was provided with an accurate 
scale along its length, and the camera 
arranged to photograph about two inches 
of the scale. (See Fig. 6.) A close view 
is needed to attain sufficient accuracy in 
displacement measurements to enable the p IG . 5. High-speed 

velocity and acceleration to be deter- motion pictures taken 

, ~, . , , with the set-up shown in 

mined. The mercury lamp was placed Fig. 4 at 6000 per second, 

close to the section to be photographed, for determining the action 

t . . , . of a metal during impact 

reducing the power required to illuminate tension. 

the subject. 

A photographic study of an automatic tapping machine furnished 
some interesting results indicating an advantage in increasing the 
speed of the cycle. Motion pictures at the rate of 1020 per second 
were taken of a light aluminum sectored disk about 4 inches in diame- 
ter attached to the chuck, making it possible to determine the speed 
of rotation as a function of time. The velocity-time curve of the 
cycle showed the manner in which the chuck was accelerated by the 
clutch, the decrease in speed during the time the threads were tapped, 
the deceleration period, and the withdrawal of the tap from the work. 

The Aeronautical Engineering Laboratory of the Massachusetts 
Institute of Technology employed a high-speed camera to photo- 
graph the spray from solid injection Diesel jets. The mercury-arc 
lamp for this problem was shaped like a doughnut and fitted inside 




296 



H. E. EDGERTON AND K. J. GERMESHAUSEN [J. S. M. P. E. 




.FiG. 6. High-speed camera arranged for a close-up of shot and 
arrow, for analyzing its motion. 

a pressure chamber filled with carbon dioxide. In ; one. end of the 
chamber was a heavy glass window through which the camera could 
be directed at the? spray. The camera was operated at the rate of 




FIG. 7. Frames from 3 5-mm. 
film taken with ordinary 
camera, of vortices at the 
blades of an electric fan. A 
stroboscope was used for illu- 
mination, synchronized with 
the fan. 



about 2000 pictures per second, and from the photographs it was pos- 
sible to determine the velocities of various portions of the spray and 
to examine the form of the charge as it diffused through the chamber. 
Rotary and vibratory motions of a repetitive nature too fast for 



Nov., 1934] SxROBOSCOPIC-LlGHT PICTURES 297 

the eye to see may be very effectively studied by means of the strobo- 
scope, 12 and since the method is relatively simple it should be used 
instead of the high-speed camera, wherever possible. The use of the 
stroboscope depends upon the persistence of vision of the eye. Flashes 
of light are made to occur at the same frequency as that of the mo- 
tion being studied. The eye, since it sees the object at only a single 
instant during each cycle, receives each view of the image at the same 
relative instant of the cycle; hence the object appears to be station- 
ary. The motion of the object may be made to appear to pass 
through its cycle of events slowly by adjusting the frequency of the 
light to a value slightly different from what is required to stop the 
motion. It is thus possible to slow down the apparent motion. 
An ordinary motion picture camera may be used to make such a slow- 
motion record if the frequency of the stroboscopic light is sufficiently 
high to expose every frame of the motion picture film. Fig. 7 shows 
a section of a film taken in such a manner, showing the flow of air 
through a fan blade. Titanium tetrachloride was used to produce 
the smoke for rendering the filaments of air visible. 

The examples described in this paper are examples of subjects to 
which the camera may be applied, and emphasize those types of prob- 
lems for which the stroboscopic-light high-speed camera is especially 
adaptable. 

REFERENCES 

1 MUYBRIDGE, E. : "Animals in Motion," Wm. Clowes & Son, London, 1899. 
MAREY, E. J.: "Movement," E. Appleton & Co., New York, N. Y., 1895, 

p. 196. 

2 JENKINS, C. F. : "Motion Picture Camera Taking 3200 Pictures per Second," 
Trans. Soc. Mot. Pict. Eng., VII (1923), No. 17, p. 77. 

JENKINS, C. F.: "The Chronoteine Camera for High-Speed Motion Picture 
Studies," Trans. Soc. Mot. Pict. Eng., X (1926), No. 25, p. 25; /. Soc. Automot. 
Eng., 22 (Feb., 1928), p. 200. 

3 CONNELL, W. H.: "The Heape and Grylls Machine for High-Speed Pho- 
tography," /. Sci. Instr. (Dec., 1926), No. 4, p. 82. 

4 KLEMIN, A. : "Kinematograph Studies in Aerodynamics," J. Soc. Mech. 
Eng. (March, 1928), No. 50, p. 217. 

SUHARA, T.: "New High-Speed Kinematographic Camera," Proc. Imp. Acad. 
(Tokyo} (Oct., 1929), No. 5, p. 334. 

SUHARA, T., SATO, N., AND KAMEI, S.: "New Ultra-Speed Kinematographic 
Camera," Report, Aeronaut. Research Inst., Univ. of Tokyo (May, 1930), No. 60, 
p. 187. 

6 TUTTLE, F. E. : "A Non-Intermittent High-Speed 16-Mm. Camera," /. 
Soc. Mot. Pict. Eng., XXH (Dec., 1933), No. 6, p. 474. 



298 H. E. EDGERTON AND K. J. GERMESHAUSEN 

6 TnuN: "Anwendung und Theorie der Zeitdehner," V.D.I. Zeitsch. (1926), 
No. 70, p. 1356. 

A. E. G. Zeitdehner, A. E. G. Mitteilungen (Nov., 1933). 

ENDE, W.: "Theorie des Thunschen Zeitdehners und Ihre Anwendung in 
der Aufnahme Praxis," Zeitsch. fur Tech. Physik (1930), No. 10, p. 394. 

7 ABRAHAM, H., BLOCH, E., AND BLOCK, L.: "Ultra-Rapid Kinematograph," 
Comptes Rendus (Dec. 1, 1919), No. 169, p. 1031; Reported in Scientific Amer. 
Monthly, I (March, 1930), No. 3, p. 217, referring also to camera built and used 
at the Marey Institute, Paris, by L. Bull. 

8 CRANZ, C.: "Lehrbuch der Ballistik," Vol. 3, Chapt. 8, Julius Springer, 
1926. 

9 BEARDSLEY, E. G. : "The N. A. C. A. Photographic Apparatus for Studying 
Fuel Spray from Oil-Engine Injection Valves and Test Results from Several 
Researches," N. A. C. A. Tech. Report, No. 247 (1927). 

ROTHROCK, A. M. : "The N. A. C. A. Apparatus for Studying the Formation 
and Combustion of Fuel Sprays and the Results from Preliminary Tests," 
N.A.C.A. Tech. Report, No. 426 (1932). 

10 EDGERTON, H. E.: "Stroboscopic and Slow-Motion Pictures by Means of 
Intermittent Light," J. Soc. Mot. Pict. Eng., XVIII (March, 1932), No. 3, p. 356. 

EDGERTON, H. E., and GERMESHAUSEN, K. J.: "The Mercury Arc as an 
Actinic Stroboscopic Light Source," Rev. Sci. Instr., 3 (Oct., 1932), No. 10, 
p. 535; Electronics (July, 1932), p. 220. 

11 LEGG, J. W. : Electric Journal (1919), p. 509. 

12 "The Stroboscope," General Radio Experimenter, Cambridge, Mass., Dec., 
1932. 

18 EDGERTON, H. E., AND GERMESHAUSEN, K. J. : "Catching the Click with 
a Stroboscope," American Golfer, Nov., 1933. 

DISCUSSION 

MR. ROSENBERGER: Can the mercury lamps be used to furnish Stroboscopic 
illumination for a microscope? 

MR. EDGERTON: The mercury-arc lamp is not very suitable for use as a source 
of illumination for a microscope, because its brightness is relatively low. How- 
ever, we have used light from the end (looking down the axis) of a specially 
constructed tube with some success. A spark in series with a mercury-arc 
tube as a control element is quite a satisfactory method of taking high-speed 
motion pictures through a microscope, because the spark is a concentrated source 
of light and the instant of starting the spark is under control. 

MR. McGuiRE: Would it be possible to increase indefinitely the speed of 
taking motion pictures by the Stroboscopic -light method? 

MR. EDGERTON: Several factors limit the upper speed at the present time, 
but further developmental work will increase the upper value. One factor is 
the problem of accelerating the film and running it at a high velocity. Another 
is the tendency of the mercury tube to "hold-over"; that is, to fail to oscillate 
at high speed. The highest speed at which we have operated the camera de- 
scribed in this paper is 6000 frames per second, taking pictures having one-fifth 
the height of a standard 35-mm. frame. 



A SWEEP OSCILLATOR METHOD OF RECORDING WIDE 

FREQUENCY-BAND RESPONSE SPECTRA ON SHORT 

LENGTHS OF MOTION PICTURE FILM* 

J. CRABTREE** 

Summary. A rapid small-scale method of determining frequency response char- 
acteristics, of particular application to cases in which a large number of conditions 
are to be compared. 

An important measurement frequently involved in the study of 
sound-film records is that of determining frequency response char- 
acteristic. The method usually employed is cumbersome, involving 
the use of long lengths of film. Enough footage of each frequency 
must be recorded and printed to enable a measurement of response to 
be made in the reproducer. At a reproduction speed of 90 feet per 
minute, at least 15 feet of film of each frequency will be required, 
involving for 6 frequencies a total length of film of about 100 feet. 
For processing such a length of film in a uniform manner, a continuous 
developing machine is essential. 

In the Sound Picture Laboratory of Bell Telephone Laboratories 
it was desired to investigate in detail the possibility of improving the 
frequency response characteristic of recordings by modifying the 
processing, which is here meant to include the developing, fixing, 
washing, and drying operations. This involved the study of the 
influence of a number of different developers upon the frequency 
response characteristic; and, since the minimum volume of develop- 
ing solution required for the processing machines in this Laboratory is 
75 gallons, it was obvious that an extended investigation using the 
customary machine processing methods was not feasible. 

It was decided to record the desired frequency spectrum on short 
lengths of film which could be processed in small trays, glass cylinders, 
or in a bench-model developing machine, and to determine the re- 
sponse characteristic by measuring the amplitudes of the developed 
record at the various frequencies in a recording microdensitometer. 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Bell Telephone Laboratories, New York, N. Y. 

299 



300 J. CRABTREE [J. S. M. P. E. 

Since the microdensitometer to be used accommodated a maximum 
length of film of 2*/4 inches, the entire sound spectrum desired had to 
be recorded within that length. There were several methods by 
means of which that could be done. The one adopted was to rotate 
the rotor of a heterodyne oscillator at a suitable speed and record the 
output on film by means of the light-valve in the usual manner. 
The oscillator that was used had a frequency range of 20 to 9500 
cycles, and was readjusted to a minimum frequency of 500 cycles, 
thus covering a range of 500 to 10,000 cycles. One revolution of the 
rotor varied the output continuously from 500 to 10,000 cycles. 



FIG. 1. Developed image of a 500- to 10,000-cycle band on a 2V4-inch 

length of film. 



FIG. 2. Trace of image in Fig. 1 produced by scanning in 
microdensitometer . 



In order to record the 500- to 10,000-cycle band within the limits 
of the 2 1 /4-inch length of film, it was necessary to rotate the oscillator 
rotor at 360 rpm. The developed image of the record had the ap- 
pearance of Fig. 1. When scanned in the microdensitometer, it 
produced the trace shown in Fig. 2. 

The response at any frequency is assumed to be indicated by the 
amplitude of the trace at that frequency, although, strictly speaking, 
that would be true only in the case of a print at reciprocal gamma or 
in the case of a "toe" record. However, as the records are used quali- 
tatively, the assumption is permissible. 

The wave-form is complex, for the reason that the frequency is 
constantly changing at a rapid rate. Purity of wave-form, however, 



Nov., 1934] SWEEP OSCILLATOR RECORDING 301 

is not an essential, the chief requisite being a range of frequencies 
easily and consistently reproducible at any time. 

It will be noted that very little frequency loss is shown in Fig. 2, 
despite the constancy of the input to the light- valve. This is due to 
the fact that the high-frequency loss inherent in the film is equalized 
by valve resonance. It is possible to vary the high-frequency content 
of the record by suitably choosing the tuning frequency. In practice, 
the valve is tuned to 11,000 cycles, and a length of film recorded at a 
level below valve clash. The undeveloped film containing a large 
number of successive exposures is stored, and short lengths are de- 
tached as needed. The exposed lengths of film are subjected to 
various conditions to be studied, and the recorded image is scanned 
in the microdensitometer and the traces compared. It is possible in 
such a manner to conduct an investigation of the above type 
in a fraction of the time required for full-scale experiments. Promis- 
ing leads may be selected and studied further on a large-scale basis. 



PROGRAM OF FALL, 1934, CONVENTION 
HOTEL PENNSYLVANIA, NEW YORK, N. Y. 

MONDAY, OCTOBER 29th 

10:00 a.m. Salle Moderne. Business and Technical Session, President A. N. 
Goldsmith, presiding. 

Society Business; election of officers for 1935. 

"Current Developments in Production Methods in Hollywood"; H. G. Tasker, 
United Research Corp., Long Island City, N. Y. 

"The Use of Motion Pictures for Visual Education in the New York Schools"; 
Miss R. Hockheimer, Director of Visual Education, New York, N. Y. 

Motion Picture: "Fundamentals of Acoustics"; Introduced by H. A. Gray, 
Erpi Picture Consultants, Inc., New York, N. Y. 

"The Motion Picture Industry in Soviet Russia"; V. I. Verlinsky, Amkino 
Corp., New York, N. Y. 

Report of the Standards Committee; M. C. Batsel, Chairman. 

Report of the Non-Theatrical Equipment Committee; R. F. Mitchell, Chair- 
man. 

Report of the Historical and Museum Committee; W. E. Theisen, Chairman. 

1:00 p.m. Roof Garden. Informal Get-Together Luncheon. 
For members, their families, and guests. Speakers: 

Mrs. Frances Taylor Patterson, Director of Photoplay Appreciation, Colum- 
bia University, New York, N. Y. 

Mr. Martin Quigley, Quigley Publications, New York, N. Y, 
Col. R. W. Win ton, Managing Director, Amateur Cinema League, Inc., 
New York, N. Y. 

2:30 p.m. Salle Moderne. Photographic Session, Mr. H. G. Tasker, presiding. 
"New Developments in Micro Motion Picture Technic"; H. Rosenberger, 

Sandy Hook, Conn. 
"Some Technical Aspects of Wild Animal Photography"; Martin Johnson, 

New York, N. Y. 
"The Theatergoer's Reaction to the Audible Picture as It Was and Now"; 

Mordaunt Hall, New York, N. Y. 
"Historical Notes on X-Ray Cinematography"; R. F. Mitchell, Bell & 

Howell Co., Chicago, 111., and L. G. Cole, New York, N. Y. 
"Roentgen Cinematography"; R. F. James, Westinghouse Lamp Co., Bloom- 
field, N. J. 
"Application of X-Ray Photography in Industrial Development Work"; J. R. 

Townsend and L. E. Abbott, Bell Telephone Laboratories, Inc., New York, 

N. Y. 

8:00 p.m. Salle Moderne. Lecture and Motion Pictures. 
"Some Photographic Aspects of Sound Recording"; C. E. K. Mees, Eastman 
Kodak Co., Rochester, N. Y. Exhibition of Recent Outstanding Motion 
Pictures. 
302 



PROGRAM OF THE CONVENTION 303 

TUESDAY, OCTOBER 30th 

9:15 a.m. Salle Moderne. Sound Session, Treasurer T. E. Shea, presiding. 

"Piezoelectric Loud Speakers"; A. L. Williams, Brush Development Co., Cleve- 
land, Ohio. 

Motion Picture: "Sound Waves and Their Sources"; Introduced by H. A. 
Gray, Erpi Picture Consultants, Inc., New York, N. Y. 

"Performance and Use of Wave Filters, and a Mechanical Demonstration of 
Their Characteristics"; C. E. Lane, Bell Telephone Laboratories, Inc., New 
York. N. Y. 

"Applications of High-Speed Motion Picture Photography in Industrial De- 
velopment Work"; H. I. Day, Electrical Research Products, Inc., New York, 
N. Y. 

"Some Characteristics of 16-Mm. Sound by Optical Reduction and Re-Record- 
ing"; C. N. Batsel and L. T. Sachtleben, RCA Victor Co., Camden, N. J. 

"The Need for Uniform Density in Variable Density Sound Tracks"; F. H. 
Richardson, Scarsdale, N. Y. 

1:30 p.m. Salle Moderne. Theater and Projection Session, President A. N. 
Goldsmith, presiding. 

"Possibilities of Engineering Developments in the Motion Picture Industry"; 
A. N. Goldsmith, New York, N. Y. 

Report of the Projection Practice Committee; H. Rubin, Chairman. 

Report of the Projection Screens Committee; J. H. Kurlander, Chairman. 

"Proposed Architectural, Acoustic, and Optical Standards in Motion Picture 
Design"; B. Schlanger, New York, N. Y.; S. K. Wolf, Electrical Research 
Products, Inc., New York, N. Y.; and L. A. Jones, Eastman Kodak Co., 
Rochester, N. Y. 

"Electronic Tube Control for Theater Lighting"; J. R. Manheimer and T. H. 
Joseph, E-J Electric Installation Co., New York, N. Y. 

"Luminous Fronts for Theaters"; C. M. Cutler, General Electric Co., Cleve- 
land, Ohio. 
8:00 p.m. Salle Moderne. Eixhbition of Recent Outstanding Motion Pictures. 

WEDNESDAY, OCTOBER 31st 

9:15 a.m. Salle Moderne. Photographic Session, Mr. L. A. Jones, presiding. 

"International Sensitometric Standardization"; W. Clark, Eastman Kodak 
Co., Rochester, N. Y. 

Report of the Color Committee, C. Tuttle, Vice- Chairman. 

Report of the Membership and Subscription Committee, E. R. Geib, Chairman. 

"Some Factors in Photographic Sensitivity"; S. E. Sheppard, Eastman Kodak 
Co., Rochester, N. Y. 

"Rear Projection for Process Photography"; G. G. Popovici, Eastern Service 
Studios, Inc., Long Island City, N. Y., and H. Griffin, International Projec- 
tor Corp., New York, N. Y. 

"The 16-Mm. Sound-Film Outlook"; W. B. Cook, Kodascope Libraries, New 
York, N. Y. 

"The Non-Rotating High-Intensity D-C. Arc for Projection"; D. B. Joy and 
E. R. Geib, National Carbon Co., Cleveland, Ohio. 



304 PROGRAM OF THE CONVENTION 

"The Stablearc-Unitwin Motor-Generator for the Non-Rotating High-In- 
tensity D-C. Arc"; I. Samuels, Automatic Devices Co., Allentown, Pa. 
2:00 p.m. Inspection Trips to the Plants and Laboratories of: 

International Projector Corp. 

Weston Electrical Instrument Corp. 

Museum of Science and Industry 

Eastern Service Studios, Inc. 

De Luxe Laboratories. Inc. 

Biograph Studios 

Ft. Lee Laboratory of Consolidated Film Industries, Inc. 
7:30 p.m. Grand Ballroom. Semi-Annual Banquet and Dance. 
Address by Dr. F. B. Jewett, Vice-Preside nt of the American Telephone & 

Telegraph Co.. and President of Bell Telephone Laboratories. Inc. 

THURSDAY, NOVEMBER 1st 
9:15 a.m. Salle Moderne. Studio and Lighting Session, President A. N. 

Goldsmith, presiding. 
Apparatus Symposium 

Moviola Co., Hollywood, Calif. 

H. A. DeVry, Inc., Chicago, 111. 

Weston Electrical Instrument Corp.. Newark, N. J. 

Roy Davidge Co., Hollywood, Calif. 

Akeley Camera Co., New York, N. Y. 

"What Is Light?"; S. G. Hibben, Westinghouse Lamp Co., Bloomfield, N. J. 
"High-Intensity Mercury and Sodium Arc Lamps"; L. J. Buttolph, General 

Electric Vapor Lamp Co., Hoboken, N. J. 

"The Use of the High-Intensity Mercury Vapor Lamp in Motion Picture Pho- 
tography"; M. W. Palmer, Motion Picture Lighting and Equipment Corp., 

New York, N. Y. 
"Recent Developments in the Use of Incandescent Lamps for Color Motion 

Picture Photography"; R. E. Farnham, General Electric Co., Cleveland, Ohio. 
"Reflecting Surfaces of Aluminum"; J. D. Edwards, Aluminum Co. of America, 

New Kensington, Pa. 
1 :30 p.m. Salle Moderne. Laboratory Session. Vice-President J. I. Crabtree, 

presiding. 
"A Revolving Lens for Panoramic Pictures"; F. Altman, Hawk-Eye Works, 

Eastman Kodak Co., Rochester, N. Y. 
"A New Method for the Control of Humidity"; F. R. Bichowsky, Surface 

Combustion Corp., Toledo, Ohio. 
Symposium on Construction Materials for Motion PictureProcessing Apparatus : 

International Nickel Co., New York, N. Y. 

Carnegie Steel Co., New York, N. Y. 

Synthane Corp., Oaks, Pa. 

"A Roller Developing Rack for Continuously Moving the Film during Process- 
ing by the Rack-and-Tank System"; C. E. Ives, Eastman Kodak Co., 

Rochester, N. Y. 

"Training Future Cameramen" ; H. C. McKay, New York Institute of Photog- 
raphy, New York, N. Y. 



SOCIETY ANNOUNCEMENTS 
ATLANTIC COAST SECTION 

At a meeting held at the Hotel Pennsylvania, New York, N. Y., October 10th, 
Mr. A. T. Williams, of the Weston Electrical Instrument Corp., Newark, N. J., 
presented a paper on the subject of "Photronic Exposure Meters," in which the 
many changes and improvements that have been made in those instruments 
during the past few years were discussed. 

The meeting was well attended. Plans were announced for future meetings 
of the Section. Ballots for the election of Section officers and Managers for 
1935 recently mailed to the voting membership of the Section included the 
following names: 

Chairman: L. W. DAVEE 

J. H. SPRAY 

Sec.-Treas.: D. E. HYNDMAN 
Manager: J. A. NORLING 
H. GRIFFIN 

The Chairman and Secretary-Treasurer are to be elected for one-year terms; 
the Manager for a two-year term. The other Manager, whose term does not 
expire until December 31, 1935, is M. C. Batsel. Mr. H. G. Tasker, present 
Chairman of the Section, will remain a member of the Board of Managers, as 
Past-Chairman. 

SOUND COMMITTEE 

The results of calibrations of a Standard S. M. P. E. Sound Test Film in various 
sound laboratories were compared at a recent meeting and further plans were 
made for continuing and completing the work, with the view of eventually 
establishing a standard of sound recording that will permit direct comparison 
of recordings made under different conditions and in different studios on an in- 
variable and mutual basis. 



The Society regrets to announce the deaths of two of its members, 

WILLIAM V. D. KELLEY 
September 30, 1934 

and 
GEORGE K. JENSON 



305 



There's No Need 
To Gamble 



A DAPTABILITY to every kind of 
shot . . . wide opportunity for 
creative artistry . . . dependable uni- 
formity . . . Eastman Super-Sensitive 
"Pan" gives you all these. Results 
prove it every day. Just choose this 
famous Eastman film . . . and stick to 
it. There's no need to gamble. 



J. E. BRULATOUR, INC. 

New York Chicago Hollywood 



JOURNAL 



OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 

Volume XXIII DECEMBER, 1934 Number 6 



CONTENTS 

Page 

The Effect of Aperture Lenses on Illumination . . W. B. RAYTON 309 

The Microdensitometer as a Laboratory Measuring Tool 

W. R. GOEHNER 318 

A Rotating Mirror Oscilloscope R. F. MALLINA 328 

Some Technical Aspects of Theater Operation 

H. M. WILCOX AND L. W. CONROW 338 

Problems in Motion Picture Engineering. . . . A. N. GOLDSMITH 350 

Motion Picture Apparatus : 

A Small Developing Machine H. R. KOSSMAN 356 

The New Klieglight H. KLIEGL 359 

Highlights of the New York Convention, Oct. 29 to Nov. 1, 1934 363 

Society Announcements 366 

Author Index, Vol. XXIII, July-December, 1934 368 

Classified Index, Vol. XXIII, July-December, 1934 370 



JOURNAL 

OF THE SOCIETY OF 

MOTION PICTURE ENGINEERS 



SYLVAN HARRIS, EDITOR 

Board of Editors 
J. I. CRABTRBE, Chairman 

O. M. GLUNT A. C. HARDY L. A. JONES 

J. O. BAKER 



Subscription to non-members, $8.00 per annum; to members, $5.00 per annum, 
included in their annual membership dues; single copies, $1.00. A discount 
on subscriptions or single copies of 15 per cent is allowed to accredited agencies. 
Order from the Society of Motion Picture Engineers, Inc., 20th and Northampton 
Sts., Easton, Pa., or Hotel Pennsylvania, New York, N. Y. 

Published monthly at Easton, Pa., by the Society of Motion Picture Engineers 

Publication Office, 20th & Northampton Sts., Easton, Pa. 
General and Editorial Office, Hotel Pennsylvania, New York, N. Y. 
Entered as second class matter January 15, 1930, at the Post Office at Easton, 
Pa., under the Act of March 3, 1879. Copyrighted, 1934, by the Society of 
Motion Picture Engineers, Inc. 

Papers appearing in this Journal may be reprinted, abstracted, or abridged 
provided credit is given to the Journal of the Society of Motion Picture Engineers 
and to the author, or authors, of the papers in question. Exact reference as to 
the volume, number, and page of the Journal must be given. The Society is 
not responsible for statements made by authors. 



Officers of the Society 

President: ALFRED N. GOLDSMITH, 444 Madison Ave., New York, N. Y. 
Executive Vice-President: HAROLD C. SILENT, 7046 Hollywood Blvd., Los 

Angeles, Calif. 

Engineering Vice-President: LOYD A. JONES, Kodak Park, Rochester, N. Y. 
Editorial Vice-President: JOHN I. CRABTREE, Kodak Park, Rochester, N. Y. 
Financial Vice-President: OMER M. GLUNT, 463 West St., New York, N. Y. 
Convention Vice-President: WILLIAM C. KUNZMANN, Box 400, Cleveland, Ohio. 
Secretary: JOHN H. KURLANDER, 2 Clearneld Ave., Bloomfield, N. J. 
Treasurer: TIMOTHY E. SHEA, 463 West St., New York, N. Y. 

Governors 

EUGENE COUR, 1029 S. Wabash Ave., Chicago, 111. 
ARTHUR S. DICKINSON, 28 W. 44th St., New York, N. Y. 
RALPH E. FARNHAM, Nela Park, Cleveland, Ohio. 
HERBERT GRIFFIN, 90 Gold St., New York, N. Y. 
EMERY HUSE, 6706 Santa Monica Blvd., Hollywood, Calif. 
WILBUR B. RAYTON, 635 St. Paul St., Rochester, N. Y. 
HOMER G. TASKER, 41-39 38th St., Long Island City, N. Y. 



THE EFFECT OF APERTURE LENSES ON ILLUMINATION* 

W. B. RAYTON** 

Summary. The complexity of the geometrical optics involved in a motion picture 
projector leads to numerous proposals for improving illumination in some respect that 
look plausible at first glance but generally fail in practice. Among such proposals we 
might consider the addition of a small collective lens in the immediate neighborhood of 
the film gate. Careful study of the transmission of light from source to screen reveals 
the fact that in some reflector arcs such a lens can improve evenness of illumination and 
in some cases raise the general level, although the latter could have been taken care of in 
the design of the lamp. In a typical condenser equipment with the 13.6-mm. high- 
intensity arc no possibility of improvement was found either in an analytical study or 
in experimental tests. 

The illumination of a projected motion picture image for any given 
combination of light source, light collector, and projection lens is a 
subject so complex that any approach to full comprehension of all its 
details can be attained only after prolonged study. This fact may be 
responsible for the proposal of numerous schemes for improving illumi- 
nation, either by increasing its total quantity or by improving its dis- 
tribution, that at first sight look plausible, but do not always work 
out as expected. It is to the application of one such proposal in the 
projection of standard 35-mm. film that attention is here directed. 
It is a suggestion the principal aim of which is to improve evenness 
of illumination. Since relatively few have occasion to keep in 
mind all the details of motion picture illumination it seems advis- 
able first to outline briefly the two types of illuminators in common 
use. 

The ideal illuminator for motion picture projection would be a light 
source of uniform and sufficient brightness and as large as the aperture 
in the film gate, but not so hot as to damage film when placed prac- 
tically in contact with it. If such a light source were available, a 
motion picture projector would reduce to the form shown in Fig. 1. 
Illumination would be even over the area of the picture except for 
two facts, one of which we shall ignore, and the other of which is 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Bausch & Lomb Optical Co., Rochester, N. Y. 

309 



310 



W. B. RAYTON 



[J. S. M. P. E. 



demonstrated in the figure. It is much more convenient in studying 
this problem to think of the light sometimes as traveling from the 
screen to the film ; at other times it may be more convenient to think 
of it as traveling from the light source to the screen, in the normal 
manner. The reversibility of a light path makes such a procedure 
entirely justifiable. At present we shall think of it as traveling from 
the screen toward the light source. In Fig. 1 two beams of light are 
shown, one focusing at the center and the other at the corner of the 
aperture. The one that focuses at the center of the film aperture 
fills the front of the projection lens, but the oblique beam does not. 
Any light belonging to the latter beam that falls on the front lens 
higher than the upper ray shown will be stopped by the mounting of 
the rear lens. In a few cases there may be none of this vignetting of 
the oblique beams but it is generally found in lenses of any consider- 




PROJECTION 



FIG. 1. Ideal projection system; source of light as- 
sumed large and bright enough to illuminate the whole 
aperture, and not so hot as to damage film. 



able length. This reduction in the effective aperture of the lens for 
oblique beams results in a reduction of brightness at the margin as 
compared with the center, even if the source of light were ideal, as 
here assumed. 

Unfortunately, no source of light even remotely approaches such 
conditions. Available sources that are bright enough are not only 
tremendously hot, but are also too small, so the science of optics is 
called upon to make the available sources of light serve our purpose. 
To get away from the danger due to heat, it is obvious that it is neces- 
sary to move the source of light farther from the film. To overcome 
the difficulty due to the insufficient size of sources the well- 
known optical law is applied; stating, that by means of a collective 
element, such as a condenser lens or a concave mirror, a source of light 
can be made to behave as though it were of any desired size, without 
any more than a minor reduction in its intensity. With a given light 



Dec., 1934] 



EFFECT OF APERTURE LENSES 



311 



collector, the maximum size the source may be made to appear is the 
diameter of the collector (condenser lens or mirror) . In practice it is 
not always possible to make the light source appear as large as desired 
because practical considerations limit the size of the light-collector. 
The laws of optics set a definite limit to the size attainable in condens- 
ers and mirrors of a given focal length; and, generally, the laws of 
economic limitations become effective before the optical limitations 
do. Larger condensers and mirrors could be made and some improve- 
ment in illumination achieved thereby, but the cost would become 
prohibitive. 

Since light collectors can not be made as large as they should be 
made, certain undesirable consequences follow, which will now be 




FIG. 2. Typical reflector arc ; 5-inch projection lens, 1 1-mm. carbon, 
11.5-inch diameter elliptical reflector: (a) central beam; (6) oblique 
beam. 

examined briefly. There are two cases. The simpler one is pre- 
sented by customary practice in reflector arcs and will be considered 
first. Fig. 2 represents an assembly of a 5-inch projection lens of the 
Cinephor type, a standard aperture, an arc with an 11-mm. positive 
carbon, and an elliptical mirror 11.5 inches in diameter. The arc is 
imaged in the plane of the film or very near it. To study this case it 
is helpful again to consider the light as proceeding from the screen to 
the arc. 

Fig. 2a shows the beam of light involved in imaging the center of 
the picture and Fig. 2b an oblique beam that images a point at the 
corner of the picture. For the center of the picture the mirror is large 
enough to fill an area of the lens corresponding to a relative aperture 
of about //2.8. A beam of light of that diameter entering the lens 



312 W. B. RAYTON [j. s. M. P. E. 

would focus at the center of the film aperture, diverge from the focal 
point, and just fill the mirror. Since film aperture and arc crater are 
conjugate foci, the beam after reflection by the mirror would come to 
a focus again at the center of the crater. 

The oblique pencil of light is indicated by three rays 1, 2, 3, which 
divide the beam into two zones. Ray 2 is a limiting ray, the position 
of which is found by joining the upper edge of the mirror to the corner 
of the film aperture. Ray 1 is another limiting ray, the highest ray 
that will pass through the projection lens at that angle. The two 
rays, and any that lie between them, will participate in imaging the 
corner of the aperture upon the screen, but they do not include the 
whole lens aperture. Rays between 2 and 3 are unavailable because 
the mirror is too small. The oblique beam is limited on one side by 
the size of the mirror and on the other by the construction of the 
projection lens. It is smaller than the central beam, and the illumi- 
nation at the edge of the screen is correspondingly less than at the 
center. 

It should be noted that an additional complication is introduced by 
the obstruction of light by the carbons and carbon-holder. As a con- 
sequence, both central and oblique beams have irregularly shaped 
holes in the center. The obstruction is slightly greater for oblique 
than for central beams. The difference is not great from the absolute 
standpoint, but inasmuch as the oblique beam is of smaller cross- 
section than the central one, the relative reduction is considerably 
greater in the former. If, as in this case, the arc is imaged at the film, 
the question of arc size is easily settled. If the image of the arc fills 
the aperture, it is large enough; otherwise it is not, and the margin 
of the picture will receive no direct illumination. 

The question of arc size is not so easily disposed of in the next case, 
however, which is typical of all condenser combinations. Because of 
insufficient magnification, the source can not be imaged in the plane 
of the aperture but must be imaged at some distance ahead of it in 
order to get light to the margin of the picture, making the geometrical 
optics somewhat more complicated than in the case of the reflector 
arc. Illumination in the center of the field may be limited either by 
the size of the condenser or by the size of the light source ; according 
to adjustment it will be one or the other, but not both. In the margin 
of the field both size of condenser and size of source are likely to be 
limiting factors. The conditions are brought out in Fig. 3, which 
shows the combination of a 5-inch Super- Cinephor projection lens, 



Dec., 1934] 



EFFECT OF APERTURE LENSES 



313 



the most efficient condenser system in common use, 6 inches in diam- 
eter, and a 13.6-mm. high-intensity carbon arc as source. Fig. 3a 
shows the beam of light concerned in imaging the center of the field, 
Fig. 3b that concerned in imaging the corner of the picture. The 
drawings are made to scale. The lens has a relative aperture of //2.3 ; 
the condenser, with reference to the center of the film aperture, of 
//2.37. The condenser is, therefore, large enough practically to fill 
the aperture of the projection lens for the central point of the image. 
If we trace the rays limiting a beam of f/2.37 through the system, they 
fail completely to strike the crater of the arc, proving that the crater 
of the 13.6-mm. carbon is not large anough to utilize the full aperture 
of the projection lens. If we seek the location of the rays that just 
strike the edge of the crater of the arc, we find that they occupy the 




FIG. 3. Typical condenser illumination; 5-inch projection lens, //2.3 
6-inch diameter aspheric condensers, 13.6-mm. carbon: (a) central beam; 
(6) oblique beam. 



positions marked B, B, and that the beam of light they enclose corre- 
sponds to a relative aperture of //4.8 in the plane of the drawing and 
//6.7 in a plane at right angles to the drawing, the difference being due 
to the fact that the back lens of the condenser is a cylinder. It would 
seem from the drawing that all that would be required to utilize the 
aperture of f/2.37 would be to pull the arc back from the condenser to 
the point where the limiting rays A, A intersect. This is true, but it 
would leave the margin of the picture with little or no illumination. 
The position chosen for the arc is the result of a compromise between 
central and marginal illumination. 

To digress a moment, the dimensions of the actual source of light 
in the case of the high-intensity arc are rather indefinite. The di- 
ameter of the hottest central area for the 13.6-mm. carbon is 8 milli- 



314 W. B. RAYTON [j. s. M. P. E. 

meters, as nearly as can be measured. This is surrounded by a ring 
about 2.2 millimeters wide which must also contribute considerable 
light, but is by no means as bright as the central area. The relative 
apertures just mentioned are computed for the central 8-mm. area 
from which most of the light emanates ; but the figures do not repre- 
sent the complete story, because zones of the lens not active accord- 
ing to this analysis actually do transmit light to the screen from the 
ring of carbon surrounding the central gas-ball. As experiment sup- 
ports the conclusions drawn from a study of the problem in which the 
8-mm. central area was regarded as the sole source of light, we can 
feel fairly safe in ignoring such light as is contributed by the outer 
ring of the crater. 

Referring again to Fig. 3b, four rays are shown. Ray 1 is the high- 
est ray that can pass through the projection lens and arrive at the 
corner of the aperture. Continued through the condenser we find 
that it will not strike the crater of the arc; therefore it can not exist 
in actual projection. Ray 2, after being refracted through the lens 
and passing the corner of the aperture, is refracted by the condenser 
to the lower edge of the crater. The useful area of the lens on the 
lower side is limited by the size of the crater. Ray 3 is determined by 
a line joining the corner of the aperture with the edge of the free aper- 
ture of the condenser. After refraction by the condenser it strikes 
the arc, and therefore it exists in actual projection. Any ray lower 
than 3, such as ray 4, fails to strike the condenser; therefore ray 3 
limits the useful area of the lens on the lower side and ray 3 is deter- 
mined by the size of the condenser. The zone between rays 1 and 2 
is useless because the light source is not large enough, and the zone 
between rays 3 and 4 because the condenser is not large enough. This 
setting of the arc-to-condenser distance is found, however, to be about 
the best compromise between the desire for maximum illumination 
and even illumination. Such an adjustment will afford an illumina- 
tion at the edge of the picture of approximately two-thirds that at the 
center. By pulling the arc back somewhat, the brightness at the 
center can be increased, but the brightness at the margin of the pic- 
ture will suffer. 

The ratio of the useful areas of the lens for central and marginal 
image points, is found, for this adjustment, to be practically the same 
regardless of the type of projection lens, at least for projection lenses 
as different in form as the Super-Cinephor, the Cinephor, and the type 
consisting of two widely separated cemented doublets. 



Dec., 1934] 



EFFECT OF APERTURE LENSES 



315 



It is practically inevitable under the conditions thus set forth that 
the illumination should be brighter at the center of the picture than 
at the edge. By suitable adjustment it is sometimes possible to ap- 
proach equality of illumination over the whole screen area, but only 
by sacrificing in total illumination. Unevenness of illumination has 
been especially troublesome in projection from behind a translucent 
screen, where the center of the picture usually appears so much 
brighter than the edge that the question promptly arises as to whether 
something can not be done about it in the projector. Usually noth- 
ing can. The effect is almost entirely due to the character of the 
space distribution of light transmitted through the screen. With a 
screen that is a perfect diffuser no serious trouble would exist, but a 




FIG. 4. Reflector arc with supplementary condenser at aperture 
(aperture lens) ; (a) central beam; (6) oblique beam. 

perfectly diffusing screen would transmit so little light in any one 
direction that the image would appear too dark to be satisfactory. 

One of the suggestions that have been made is to place a collective 
lens close to the film. Such lenses have been called aperture lenses. 
In so far as any effect on illumination is concerned, they might be 
placed ahead or behind the film with equal effect; but since, if placed 
ahead of the film, they would become essentially a part of the projec- 
tion lens and have a bad effect upon the image quality, it is imprac- 
ticable to .place them there. 

Fig. 4 shows the application of a lens of this kind to the optical 
system shown in Fig. 2. Two interesting results follow. In the first 
place, the angular aperture of the beam of light converging to the 
central point of the film aperture is increased, with the result that a 
greater area of the projection lens is used and there will be more light 



316 W. B. RAYTON [J. S. M. p. E. 

at the center of the screen. This is shown in Fig. 4a. This result is 
misleading, for it is accompanied by a reduction in the size of the 
image of the arc formed by the combined reflector and condenser. If 
that image were originally of just sufficient size to cover the aperture 
it would no longer cover it, and the distance from the mirror to the 
aperture would have to be increased to restore the arc image to the 
necessary size. The gain in illumination apparently attained would 
be lost by the readjustment. If the arc image were originally larger 
than necessary, the same gain in illumination might have been at- 
tained without the aperture lens, by decreasing the distance from the 
mirror to the aperture and re-focusing the arc, thus reducing the size 
of the arc image and increasing the angle of convergence of the beam 
of light. These effects are exactly compensatory, and the conclusion 
is that no gain in illumination at the center of the field is to be achieved 
by means of an aperture lens that could not have been attained by a 
different adjustment of the distances from arc to reflector and re- 
flector to aperture. Since the necessary degree of freedom of adjust- 
ment may not be present in a given lamp, however, it would not be 
safe, in any particular case, to conclude that an aperture lens would 
not provide increased illumination. 

A comparison of Figs. 2b and 4&, however, discloses an undeniable 
advantage in the use of the aperture lens. Whereas without the 
aperture lens the oblique beam, because of its inclination to the axis, 
in part fails to strike the reflector and in part fails to utilize other 
areas of the mirror, the addition of an aperture lens of appropriate 
power will deviate the entire beam, causing ray 4 (Fig. 2b) to strike 
the mirror and lowering the point of incidence of ray 1 . In fact, the 
whole area of the mirror may be made to contribute to the formation 
of the image of a point in the margin of the field; leading, therefore, 
to a level of illumination at the edge more nearly equal to that at the 
center. In addition to that effect, which is 'inevitable, there may be 
in some cases an increase in illumination at the edge of the field of the 
same nature as that described above as possible for the center of the 
field. Actual tests with an llVt-inch elliptical reflector, an 11 -mm. 
carbon at 70 amps., and a 5-inch Super-Cinephor projection lens led 
to an increase in average brightness over the entire area of the screen 
of 25 per cent. 

On the other hand, the condition represented in Fig. 3 can not be 
improved by the addition of an aperture lens. By examining Fig. 3 
it can be seen at a glance that a collective lens placed immediately 



Dec., 1934] EFFECT OF APERTURE LENSES 317 

back of the aperture could indeed change the direction of ray 4 and 
all other rays between 3 and 4 sufficiently to cause them to strike the 
condenser, whereas they now miss it completely. The gain, however, 
is offset by the fact that ray 2, which is now a limiting ray of the 
active beam, determined by the fact that it is the highest ray that will 
actually strike the crater of the arc, will not meet the arc if an aperture 
lens be introduced. The highest ray that will strike the arc will be 
lower than ray 2, and what is gained by an apparent widening of the 
useful beam on the lower side is compensated by a loss on the upper 
side. The only change is that we shall now be using a different area 
of the lens for imaging the corner of the picture. 

The essential difference between the two typical cases is that in the 
first case the only limitation of the size of the beam of light, both at 
the center and at the margin of the picture, is imposed by the size of 
the light collector. In the second case, both the light collector and 
the light source are too small for the conditions under which they are 
used. In the former case an aperture lens improves evenness of illumi- 
nation, and in case the light source is large enough it can increase the 
illumination over the whole picture more economically than by in- 
creasing the diameter of the reflector. In the second case, the intro- 
duction of an aperture lens does not appear profitable from theoretical 
considerations, a conclusion which is supported by experimental 
observations. 



THE MICRODENSITOMETER AS A LABORATORY 
MEASURING TOOL* 



W. R. GOEHNER** 



Summary. The microdensitometer is extensively used in studying a variety of 
problems of sound-film recording and reproducing: in studying the operating char- 
acteristics of light-modulating devices; in plotting variations of light transmission 
of sound-tracks in respect to the harmonic content of film records; in establishing 
correct operating technic in film processing; in studying the photographic character- 
istics of film as regards its ability to record high frequencies; and many other aspects 
of sound recording and reproducing. 

The commercially available microdensitometer s are not well suited to making such 
studies unless proper means are taken to assure correct comparisons with data ob- 
tained with a calibrated reproducer. The present paper describes the modifications 
of a Moll microdensitometer that have converted it into a satisfactory instrument for 
sound-picture investigations. 

Measured values of light transmission of photographic sound- 
films are used for evaluating and controlling various photographic 
and optical factors that influence the fidelity of photographic sound- 
records. Visual measurements of photographic density by means 
of a densitometer are satisfactory when relatively large areas of 
uniform density, such as provided by sensitometric exposures, are 
considered; but such measurements have little or no value when 
studying density variations of the sound-signal type. Recording 
densitometers are much more satisfactory because a greatly amplified 
record of the shape of the transmission wave of the signal is obtained. 
The resulting continuous record is more satisfactory for harmonic 
analysis than the measurement of the transmission at discrete points 
along the wave. 

Devices for determining the light transmission of small areas of 
photographic images have been developed, particularly for deter- 
mining the transmission and spacing of the lines of spectrograms. 
Many different kinds of apparatus have been described in the litera- 
ture as microphotometers or microdensitometers. Several types 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Bell Telephone Laboratories, New York, N. Y. 
318 



MlCRODENSITOMETER FOR MEASURING 



319 



are commercially available; in general, they provide a means of 
causing the photographic image to move in the plane of a narrow 
line of light. If variations of light transmission occur in the image, 
the light reaching the light-sensitive receiver will vary in proportion 
to the integrated value of the transmission over the area of the 
photographic film covered by the scanning image. The light-sensitive 
receiver converts the light fluctuations into electrical currents which 
actuate a sensitive galvanometer. 




FIG. 



The Moll Microphotometer, modified to permit direct readings in 
sound-film measurements. 



In the recording microphotometer, the deflection of a galvanometer 
is recorded on a photographic paper, or film, which is moved ac- 
curately in relation to the record being scanned. The linear scale 
of the original is magnified 50 or more times by mechanical means, 
so as to spread out the wave envelope to a convenient size for in- 
spection or measurement. It is evident that the mechanical linkage 
employed must be made very accurately to preserve the original 



320 



W. R. GOEHNER 



[J. S. M. P. E. 



wave-shape in the magnified record. One instrument maker guar- 
antees an accuracy of 0.001 mm. for a film-driving screw having a 
pitch of 1.0 mm.; another has devised a film-propelling system 




PHOTOELECTRIC 



FIG. 2. Standard reproducing optical system, replacing the Moll optical 

i system. 

employing a steel ribbon attached to rotating cylinders, which is 
independent of the precision of screws or gears. 1 Sandvik 2 has 
described a recording microdensitometer designed to record con- 



9000 



litiiiiiliiiliU 

7000 



5000 3000 

FREQUENCY IN CYCLES PER SECOND 



1000 



FIG. 3. Microdensitometric record of line-grating test-screen. 

tinuously the variations of transmission in a manner related to the 
projection characteristics of the standard reproducer optical system 
and photoelectric cell. 

During the early development of the photographic method of 



Dec., 1934] 



MlCRODENSITOMETER FOR MEASURING 



321 



PHOTOELECTRIC 
CELL 




FIG. 4. Schematic circuit of d-c. amplifier between photoelectric cell and 

galvanometer. 

recording sound at Bell Telephone Laboratories, density variations 
of photographic sound-tracks were analyzed by means of a micro- 
densitometer used for spectrophotographic work. Correlation of 












0.5 1.0 1.5 2.0 2.5 

CURRENT INPUT IN MICROAMPERES 



FIG. 5. Characteristic of d-c. amplifier for various photoelectric cell currents. 



322 W. R. GOEHNER [J. S. M. P. E. 

the resulting measurements with those of actual sound projection 
practice proved difficult because of certain fundamental differences 
between the analyzing instrument and the standard sound-film 
projection system. The principal differences were: 



9000 7000 5000 3000 1000 

FREQUENCY IN CYCLES PER SECOND 

FIG. 6. (A) Microdensitometric record of line-grating frequency char- 
acteristic exposed on positive film; (B} photographic frequency character- 
istic of a grainless type of film, obtained by the line-grating test object 
method. 

(1) The spectral sensitivity of the thermopile used in the microdensitometer 
differed from that of the projector photoelectric cell. 

(2) The optical system of the microdensitometer accentuated the specular 
transmission of the film so as to increase the effective projection cotnrast factor. 

(3) The recorded amplitudes for high-density films were inadequate. 



1000 3000 5000 7000 900O 

FREQUENCY IN CYCLES PER SECOND 

FIG. 7. Microdensitometric record of short section of positive print of a 
variable-density frequency record. 

The difficulty of correlating data obtained with the Moll micro- 
densitometer with those obtained with the standard projection 
system indicated that modifications were necessary to convert it 



Dec., 1934] 



MlCRODENSITOMETER FOR MEASURING 



323 



into a direct-reading instrument for sound-film measurements. 
Fig. 1 shows the Moll microphotometer so modified. The magazines 
accommodate full reels of motion picture film so as to facilitate the 
handling of long lengths of film. The Moll optical system has been 
replaced by the standard Western Electric reproducing optical 
system (Fig. 2) consisting of an 8.5-volt 4.0-ampere lamp, a lens 
and slit assembly, and a No. 3-A photoelectric cell. The standard 



LAMP IN FOCUS 







2 MM OUT OF FOCUS 



\ 





4 MM OUT 


OF FOCUS 




\ 








\ 






/ 
X 



FIG. 8. 



Variations of transmission across sound-track recorded with ex- 
perimental coiled filament recording lamp. 



lens and slit assembly provides a scanning image 0.001 inch wide. 
Stryker 3 has published values of reproduction loss at high frequencies 
due to the finite width of the scanning slit: an 0.001-inch scanning 
image introduces a loss of 5 db. at 10,000 cycles. In experimental 
work the desirability of maintaining high recording amplitudes at 
the higher frequencies led to a modification of the optical system to 
provide a scanning image having a width of 0.003 inch, reducing the 



324 W. R. GOEHNER [J. S. M. P. E. 

theoretical scanning loss at 10,000 cycles to approximately 0.5 db. 
In order to measure the loss introduced by the optical system, a 
specially prepared line grating test-screen was scanned in the micro- 
densitometer in the same manner as for a sound film. The test- 
screen is a series of opaque lines ruled on a glass plate, spaced at 
intervals corresponding to wavelengths of 1000, 3000, 5000, 7000, 

FREQUENCY =100 CYCLES PER SECOND 

RECORDING LEVEL RELATIVE TO RELATIVE REPRODUCED 

OVERLOAD LEVEL IN DECIBELS OUTPUT IN DECIBELS 

-2.0 



+2.0 



4-4.0 



i 



48.0' / \ / +8.0 






FIG. 9. Microdensitometric records of recordings made with several levels 
of input to the light- valve. 

and 9000 cycles per second. Fig. 3 shows the microdensitometric 
record obtained by scanning the test-screen; it will be observed that 
the relative amplitudes at 9000 cycles compared with those at 1000 
cycles indicate a loss approximating the theoretical scanning loss 
determined for the 0.0003-inch scanning image. The adjustment 
of focus and azimuth of the slit and lens assembly must be accurately 



Dec., 1934] MlCRODENSITOMETER FOR MEASURING 325 

maintained to prevent false indications of loss at high frequencies. 
Provision is made in the film-supporting mechanism to maintain the 
focus and azimuth unaltered when films are interchanged. 

By using the 0.0003-inch scanning slit the light input to the photo- 
electric cell was reduced by approximately 10 db., compared with 
the output obtained with the standard optical system, thereby 
reducing the galvanometer deflections to low values for high-density 
films. Larger galvanometer currents were attained by inserting 
a balanced d-c. amplifier between the photoelectric cell and the 
galvanometer. A schematic circuit of the amplifier is shown in 
Fig. 4. The maximum current amplification is 40 db., which is 





\IUfUi 



FIG. 10. Microdensitometric record of the letter O; (A) covering 0.017 
sec.; (B) covering 0.123 sec. 

sufficient to cause a deflection of 1.0 cm. when a film having a trans- 
mission of one per cent is introduced into the scanning beam. The 
linearity of the amplifier for a range of cell currents is shown by 
Fig. 5. 

The time-constant of the galvanometer system limits the speed of 
scanning, and the microdensitometer has been equipped with a 
galvanometer having a damped period of 0.2 second. It has been 
our experience that that speed is sufficient for scanning 2.2 inches of 
high-frequency film in ten minutes without permitting the results to 
be affected appreciably by galvanometer lag. 

The microphotometer is arranged for two values of linear magni- 



326 W. R. GOEHNER [j. s. M. P. E. 

fication. When the recording drum is connected to the high-speed 
gear the magnification is 50, so that a 15-inch record represents ap- 
proximately 0.3 inch of film, corresponding to one wavelength of a 
60-cycle constant-frequency film record. When the recording drum 
is connected to the low-speed gear, the magnification is approximately 
7, so that the 15-inch record represents about 2.1 inch of film. 

Microdensitometric records showing the characteristics of film 
materials in regard to high-frequency response have been made by 
scanning contact prints of the line-grating test object. The use of 
the line-grating test object in studying photographic frequency loss 
characteristics eliminates problems of optical definition and control 



50 AND 5000 





FIG. 11. Microdensitometric record of (A) recording made with equal 
levels of 2000- and 2100-cycle waves applied to the light- valve simultane- 
ously; (5) of a similar record obtained with 50- and 5000-cycle waves. 

of light modulation, which must be considered when the films are 
exposed in a standard recording machine. The line-grating test 
method has the further advantage of being able to cover the desired 
acoustical wavelength range in a film 2.25 inches long, whereas 
several feet of film are required for a single frequency recorded in 
the usual manner. It should be noted that the line-grating test 
object gives a square-topped wave of exposure which is not equivalent 
to the normal frequency recording but which does approximate a 
type of signal that is more difficult to record and reproduce a 
steep wave-front signal. Fig. 6A is a microdensitometric record of 
a line-grating frequency characteristic exposed on positive film. 
The loss of amplitude at the high frequencies should be com- 



Dec., 1934] MlCRODENSITOMETER FOR MEASURING 327 

pared with the loss obtained by scanning the line-grating test object. 

Fig. SB shows the photographic frequency characteristic of a 
grainless type of film, obtained by the line-grating test object method. 
The photographic sensitivity of the material is very low compared 
with the sensitivity of positive film, and it is evident, therefore, 
that difficulty would be experienced in recording a normal frequency 
record on that kind of material. The microdensitometer and the 
line-grating test object offer a convenient means for investigating 
the frequency characteristic of a wide variety of materials. 

Fig. 7 is a microdensitometric record of a short section of a positive 
print of a variable-density frequency record. The negative was 
recorded in a standard recording machine; the record shows the 
wave-shape for sinusoidal exposure of the negative. 

Problems relating to the illumination efficiency of recording and 
reproducing optical systems have been investigated by the micro- 
densitometric method. Fig. 8 is the record of variations of trans- 
mission across a sound-track recorded with an experimental coiled 
filament recording lamp. The influence of coil spacing in producing 
striations on the sound track is shown by the peaks and valleys of 
transmission across the track when the lamp is operated "in focus." 

Fig. 9 shows microdensitometric records of recordings made with 
several levels of input to the light- valve. The non-linear distortion 
resulting from light overload is indicated by the departure from the 
sinusoidal form as the level is increased beyond the overload point. 

The microdensitometer may be used to study individual sounds 
selected from speech or music records. For example, Fig. 10 shows 
the scanning of the letter taken from one of the character films 
used on the call announcer described by Matthies. 4 Record A 
covers a period of 0.017 second; record B covers 0.123 second; the 
total time taken by the complete letter is 0.27 second. Fig. 1L4 
is a record of equal levels of 2000- and 2100-cycle waves applied 
simultaneously. Fig. 1 IB is a similar record of 50 and 5000 cycles. 

REFERENCES 

1 WEIGLE, J.: "A New Microphotometer," Rev. Sci. Instr., 4 (Nov., 1933), 
No. 11 (New Series), p. 595. 

2 SANDVIK, O. : "Apparatus for the Analysis of Photographic Sound Records," 
/. Soc. Mot. Pict. Eng., XV (Aug., 1930), No. 2, p. 201. 

3 STRYKER, N. R.: "Scanning Losses in Reproduction," /. Soc. Mot. Pict. 
Eng., XV (Nov., 1930), No. 5, p. 610. 

4 MATTHIES, W. H.: "The Call Announcer," Bell Lab. Record, 8 (Jan., 1930), 
No. 5, p. 210. 



A ROTATING MIRROR OSCILLOSCOPE* 

R. F. MALLINA** 

Summary. When studying sound it is sometimes useful to project the wave-form 
of electrical or acoustical phenomena on a screen. A rotating mirror in combination 
with a vibrating mirror and a light source provide a convenient means of showing such 
waves. The problem of building an instrument for such a purpose is comparatively 
simple if a small screen is used in a dark chamber. However, when the screen is 
large enough to be viewed by a dozen or more persons, many difficulties arise. 

The paper describes how the various parts of the apparatus may be coordinated in 
order to produce a comparatively bright, clearly defined wave with a small incan- 
descent lamp in a room of average illumination. The vibrator used in the apparatus 
may be so constructed that its response is either inversely proportional to or inde- 
pendent of the frequency. 

One of the most instructive methods of demonstrating the char- 
acteristics of trains of sound waves, as of speech or music, is to 
project optically a corresponding wave on a screen. A cathode ray 
oscillograph is admirably suited for such demonstrations provided 
the wave is either steady or is viewed in short sections. If 
we wish to show the transitional states as well as the comparatively 
steady portions of such sound waves, we must project upon the 
screen a much longer section of the wave than can be displayed by 
the cathode ray oscillograph. In this paper the construction of a 
simple portable oscilloscope is described, with which relatively long 
trains of waves may be projected upon a screen so as to be visible 
to a group of persons in a room lighted in the ordinary manner. 
The various factors that should govern the design of such an in- 
strument for best visibility of the wave will be emphasized. 

The oscilloscope includes a vibrating mirror actuated electrically 
by a microphone and amplifier, and a scanning-mirror system 
rotating at a constant speed. The general arrangement of the 
mirrors and the screen is shown in Fig. 1, and is the same as that 
commonly employed in vibrating-mirror oscillographs. There are 
two principal forms in which a rotating-mirror oscilloscope may be 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Bell Telephone Laboratories, New York, N. Y. 
328 



ROTATING MIRROR OSCILLOSCOPE 



329 



built. The vertical arrangement (Fig. la) is preferable from the 
point of view of compactness, but unless the screen has a cylindrical 
form, the axis of the wave traced by the spot of light upon the screen 
will be distorted into an upwardly concave arc which may become 
objectionable when a wide screen is used. With the horizontal 
arrangement (Fig. Ib) this distortion is avoided. Theoretically, the 
screen should be spherical in either arrangement so that the light 
spot will be in focus at all times. However, since the distance from 



VERTICAL ARRANGEMENT 




HORIZONTAL ARRANGEMENT 

/VIBRATING 
MIRROR 




PLAN VIEW 



PLAN VIEW 





SIDE VIEW SIDE VIEW 

(a) (b) 

FIG. 1. (a) The path of the light ray in the vertical arrangement; 
(b) in the horizontal arrangement. 

the vibrating mirror to the screen is great, as a rule, the change of 
focal length is small and can not be noticed. 

The Scanning Mirror. Although the principle of an oscilloscope 
is quite simple, the function of the rotating mirror is sometimes not 
clearly understood. Assume for the moment that there is only one 
mirror in the rotating-mirror assembly and that the vibrating mirror 
has a sinusoidal motion. As the beam of light reflected from the 
rotating mirror passes across the screen we see a sine wave projected. 
The length of the visible wave will depend upon the angular velocity 
of the rotating mirror. If the angular velocity is such that the 



330 R. F. MALLINA [j. s. M. P. E. 

entire width of the screen is traversed in Vie of a second, then we 
see the wave extend over the whole width of the screen, since the 
average time of persistence of vision is about Vie of a second. If 
the velocity is less than that (say, the light beam covers only x /4 of 
the screen in Vie of a second), the length of the observed wave is 
*/4 the width of the screen and we receive the impression that this 
short section of a wave sweeps across the screen. 

In case of speech or music we are in general dealing with waves 
that are not steady but which vary continually with time. The 
traces produced by succeeding mirrors in the mirror assembly can 
therefore not be superposed, and if not more than a single trace 
is to be perceived upon the screen at a time, not more than one must 
be projected during the time interval of Vie of a second; on the other 
hand, if the number of traces projected per second is much less than 
16 a disagreeable flicker will be noticed. 

The question most frequently asked by persons observing an 
oscilloscope wave for the first time is, "What does one actually see 
upon the screen? Is it a wave such as one might see by observing 
the groove of a phonograph record passing beneath a microscope, 
or is it something else?" Probably the easiest way to simulate a 
rotating-mirror oscilloscope is to divide such a phonograph groove 
into lengths corresponding to Vie of a second, and to photograph 
by means of a motion picture camera each successive length on 
each successive frame of the film. If the film were then passed 
through a motion picture projector we should see wave changes 
similar to those seen on the oscilloscope not a wave bodily and 
continuously travelling across the screen, similarly to the wave of 
a phonograph record travelling beneath a microscope; but the wave 
in sections, each corresponding to a time-interval of about Vie of a 
second. In other words, what we see on the screen at a given instant 
is what happened during the preceding Vie of a second, and the 
wave we see at that instant is stationary and not moving across the 
screen. 

The question is now, how many mirrors are required upon the 
rotating-mirror assembly. With one mirror it is obvious that the 
screen will be dark most of the time. If we increase the number of 
mirrors, forming a polygon of 5, 10, or 20 sides, the flicker caused by 
the change from a dark screen to a projected wave and vice versa 
will disappear gradually. The correct number of mirrors is the 
number that allows the pencil of light reflected from one mirror to 



Dec., 1934] 



ROTATING MIRROR OSCILLOSCOPE 



331 



appear upon the screen at precisely the moment when the one that 
was previously projected leaves the screen. 

The requisite height of the mirrors is determined from the geometry 
of Fig. 1, as also their width, if the tolerable loss of illumi- 
nation at the ends of the screen due to the cutting into the pencil of 
light by the edges of the rotating mirrors is specified. 

The Optical System. In choosing the optical system it is most 
important to project the maximum amount of light upon the screen 
for a given intensity of the light source and size of image. The 
simplest and most efficient arrangement is provided by a concave 
vibrating mirror for focusing the light source upon the screen. 

In order to determine the focal length of the mirror the size of 



Hri 
r. 

MIRROR W| => 2 

D\___ 

LIGHT 
X XB SOURCE 



SOLID ANGLE 1^- 




S=36" 




(a) 



(c) 



FIG. 2. (a) The limiting condition for sweep angle 2a; (b) the 
solid angle subtended at the screen; (c) the limiting condition for 
the mirror tilting angle 0. 



the image to be projected upon the screen must first be decided. 
This depends upon the highest frequency to be resolved. Assume 
that we wish to inspect a 3000-cycle wave upon a screen 36 inches 
wide, across which the beam of light will sweep in Vi 6 of a second. 
The wavelength on the screen will be approximately 0.2 inch, and 
the 3000-cycle wave will be fairly well resolved if the width of the 
image is about 0.1 inch. 

Experience shows that for inspecting waves of speech and music the 
most satisfactory wave is one the average slope of which is com- 
paratively great, say about 70 degrees. Such being the case, we 
may choose an image of considerable height, say four times the width. 
By so doing more light is obtained upon the screen than would be 
obtained with a square or round spot. 



332 R. F. MALLINA [j. s. M. P. E. 

The 32-cp. automobile headlight is a convenient source having 
such proportions. The height of the filament is J / 8 inch and its 
width is Vs2 inch. Since the width of the light spot upon the screen 
is to be about Yio inch, or say, l / 8 inch, the optical magnification 
should be 4. 

At the beginning it was assured that the width of the screen was 
to be 36 inches, the width of the image l / 8 inch, and the filament 
1 /32 inch. One more factor must be considered: the sweep angle 2a 
(Fig. 2). If the screen is to be visible to a large group of persons 
it should be substantially flat or, at the most, slightly concave. 
To keep the image in focus on a flat screen the sweep angle 2 a must 
not be very much greater than about 36 degrees. The following 
values are therefore known: S, W 2 , Wi, and a. From the relation 



(1) 



where E is the illumination or the flux per unit area of the spot, B 
is the brightness of the light source, and ^ the solid angle subtended 
by the mirror at the screen. The formula shows that the only 
means of increasing the illumination is to use a brighter light source 
and a larger mirror. It can be shown also that no other optical 
system can increase the efficiency beyond that obtained by a single 
lens or a concave mirror. 

Assuming now that a single concave mirror is used in the optical 
system, and the distance D it Fig. 2, between the light source and 
the concave mirror, and the magnification M, may be obtained 
from: 

D 2 , . 

D 1 ==M 

and the focal length / from: 

+*>/ 

From Fig. 2 (a) it is apparent that the sweep angle 2 a is a limiting 
condition. Fig. 2(c) shows that an additional limiting condition 
is imposed by the angle B through which the mirror oscillates, and 
by the maximum double amplitude x of the projected wave, which 
was assumed to be 10 inches. If the angle 6 is too great, mechanical 
stresses occur in the drive and distortion results. Equation (4) 



Dec., 1934] 



ROTATING MIRROR OSCILLOSCOPE 



333 



shows that the illumination is again a function of the brightness and 
the mirror area, this time being expressed as a function of the angle 
8 and the amplitude x; viz., 

'tan 2 d' 



16 Bm* 



/tan20\ 2 



(4) 



Assuming the sweep angle 2a to be the limiting condition, it 
was found that 6 is sufficiently small to cause no excessive stresses; 
in other words, the limiting condition is a rather than 6. 

In order to facilitate the choice of the variables in the equations, 
they were plotted for a number of focal lengths, as shown in Fig. 3. 
Four boundaries limit D 2 and H 2 . The first is the resolving power 



ILLUMINATION 
\ 



XMAX 
Hz 

= AMPLITUDE OF WAV.. 




160 140 120 100 80 60 40 2O / X 20^-40'" '60 80 100 120 140 160 
DISTANCE OF LAMP TO VIBRATING MIRROR^^DrSTANCE F IMAGE TO VIBRATING 
IN INCHES [D| = f(l + j^)] MIRROR IN INCHES [D 2 =f(n-M)] 

FIG. 3. Curves showing the relations between/, D\ P 2 , M and H z> 
and boundaries for H 2 and D%. 

of the eye (R), which limits the ratio of the size of the image to the 
distance Z> 2 . For a given image there will be a distance D 2 beyond 
which the eye can not resolve the high frequencies. 

The second boundary is the ratio of the maximum amplitude X 
of the projected wave to the height of the image H 2 . If the size of 
the image relative to the amplitude is too large, the high frequencies 
will not be resolved. 

The third boundary is the minimum distance D 2 between the 
vibrating mirror and the screen. In general, the minimum limit 
for D z is the distance at which the size of the oscilloscope begins to 
be large as compared with the size of the screen, thereby obstructing 
the view. 



334 



R. F. MALLINA 



[J. S. M. P. E. 



A boundary that is more difficult to establish is the maximum 
distance D 2 , which depends largely upon the illumination in the room. 
In a dark room D z can be made quite large, but in a light room the 
screen must be quite close to the oscilloscope to perceive a distinct 
wave. The curve E shows how rapidly the illumination decreases 
as D 2 is increased. 

It is well known that the image formed by a spherical mirror is 
astigmatic except for perpendicular incidence. For both the arrange- 



RUBBER BLOCKS TO 

JAKE UP THRUST 

OF SHAFT 




DRIVING TIE 
CONE 





MIRROR- 



i 2 =0 



0.005" MUSIC WIRE WITH , 
L^ ^ ENDS BENT OVER 
^a \ AND CEMENTED IN 



(d) 



(e) 




FIG. 4. (a) Front view of vibrator; (b) cross-section; (c) tie con- 
necting mirror and diaphragm cone; (d) analogous circuit for de- 
termining axis of spontaneous rotation; (e) end view of mirror. 

ments shown in Fig. 1, (a) and (b), the angle of incidence is quite large. 
A cylindrical lens may conveniently be placed in the path of the 
light in such a position and of such focal length as to correct the 
astigmatism and afford an appreciable improvement in definition. 

The Vibrator. The driving mechanism for the vibrating mirror 
of a portable oscilloscope should be rugged, free from resonances, 
free from variations due to atmospheric conditions, and capable of 
imparting sufficient angular motion to the mirror. A modified 



Dec., 1934] ROTATING MlRROR OSCILLOSCOPE 335 

form of the moving-coil microphone described by Wente and Thuras 1 
best fulfills the conditions, the application of which is shown in Fig. 4. 
The mirror is attached along its axis of spontaneous rotation to a 
thin shaft supported in jewel bearings, and is driven at the center 
of percussion (Fig. 4 (c) and (e)). Mounting the mirror in this 
manner reduces the possibility of resonance vibrations. To reduce 
the possibility of such vibrations still further, the mirror is made 
semicircular at the driven end. 

In order that the efficiency of the drive may be a maximum, it is 
necessary to determine what dimensions the driving coil should have 
relatively to the size of the mirror. A convenient expression for the 
efficiency 17 (at a given frequency) is 77 2 = x z /i 2 R, where x is the 
amplitude of the mirror displacement, i the maximum current that 
the coil will withstand, and R the resistance of the coil. At high 
frequencies the device is mass-controlled, and we have the relation 

Bli = <**x(M d + M m ) (5) 

where B is the flux density, / the length of the coil, co/2?r the fre- 
quency, M d the mass of the diaphragm and coil, and M m the effective 
mass of the mirror at the point at which it is driven. Assuming, 
then, that in changing one dimension all other dimensions are changed 
proportionally, the efficiency is 



where C and h are constants, ktf* = M dl and r is the radius of the 
coil. This equation shows that r} is a maximum when k\r* = M m ; 
in other words, when the effective mass of the diaphragm and coil 
is equal to the effective mass of the mirror. Assuming now that 
a certain displacement of the mirror is required for a given displace- 
ment on the screen, the size of the driving coil and diaphragm can be 
calculated. 

It was mentioned before that the illumination on the screen is 
proportional to only two factors; the brightness of the light source 
and the solid angle subtended on the screen (E = B+). In order 
to increase E it is conceivable that the vibrating mirror might be 
moved very close to the screen, thereby increasing \j/. This natu- 
rally would increase the sweep angle 2a (Fig. 2). Instead of 
employing a rotating mirror, the oscillograph could have been so 
designed that the horizontal movement of the spot of light upon 



336 R. F. MALLINA [j. s. M. P. E. 

the screen is produced by a bodily movement of the vibrator across 
the screen. 

To determine whether the illumination E increases as the distance 
D 2 is decreased, the following argument may be employed: The 
kinetic energy K of the mirror is Id 2 /2, where I is the moment of iner- 
tia and 6 the angular velocity of the mirror, and where the illumination 
E is again B^. For a square mirror / = kiA b / 2 , where k\ is a constant 
and A the area of the mirror. It is assumed here that the ratio of 
the thickness of the mirror to its area remains constant. The angular 
velocity 8 of the mirror is k 2 /D 2 where K 2 is a constant and D 2 the 
distance from mirror to screen. Solving these equations for the 
illumination E in terms of the distance D 2 we obtain E = k 3 /D 2 * /5 , 
assuming that the kinetic energy K and the brightness B are to 
remain constant. In other words, the nearer the vibrator is moved 
to the screen the greater is the illumination. However, there are 
four factors that limit the shortening of the distance D 2 : 

(1) If DZ is not large, compared with the maximum amplitude traced upon 
the screen, the spot will not remain in focus. 

(2) As mentioned before, the angle 9, through which the vibrating mirror 
is tilted, can not be made very large without straining the tie connecting the 
diaphragm and the mirror. 

(3) The maximum amplitude of the vibrator is limited by the depth of the 
air chamber behind the diaphragm. 

(4) If a driver of a certain power capacity is assumed, the distance D 2 will 
attain a value such that 6 becomes so large that the coil will be burned out. 

Using a moving-coil drive as described in this paper, the limiting 
factor is the amplitude of the diaphragm. It would be possible, of 
course, to drive the mirror through a larger leverage; but as long 
as the axis of spontaneous rotation is to remain within the area of 
the mirror, a substantial increase of leverage can not be achieved. 
The best that can be done is to use the conjugate values of the 
point of percussion and the axis of spontaneous rotation. According 
to the design followed out in this paper, factor 2 above is not very 
close to a limiting condition, as the angle 9 is quite small. Factor 
4 is rather far removed from the limiting condition so long as the 
effective mass of the mirror is equal to the effective mass of the 
diaphragm assembly. But even if it were possible to bring the vi- 
brator close to the screen, the mechanics of moving it across the 
screen would greatly complicate the machine, and this method 
was therefore not considered in the final design of the oscilloscope. 



Dec., 1934] 



ROTATING MIRROR OSCILLOSCOPE 



337 



The driving structures may be designed either for constant velocity 
or for constant amplitude per unit of force over a wide frequency 
range. With a high-quality microphone and amplifier, if the drive 
is constant velocity, the projected wave will represent the displace- 
ment of the air particles of the sound wave; whereas if it is constant 
amplitude, the wave will represent the pressure. Although the 
latter case may possess greater physical significance for demon- 
stration purposes, the former type of wave is generally to be preferred 
as it is more easily followed. The measured response of a vibrator 
designed for constant velocity is shown in Fig. 5. 

The Screen. The visibility of the wave largely depends upon the 
reflection characteristics of the screen. The same conditions apply 
here as for a motion picture screen. When a maximum lateral 
angle of view has been decided upon, a screen should be chosen that 




400 800 1200 1600 2000 2400 2800 3200 

FREQUENCY IN CYCLES PER SECOND 

FIG. 5. Measured characteristic of vibrator. 

will reflect the greatest amount of light throughout that angle. 
With such a screen an appreciably brighter image will be obtained 
throughout the viewing angle than would be the case if a completely 
diffusing screen were used. 

If the oscilloscope is to be operated in a lighted room, a considerable 
improvement in visibility will be achieved if the screen is surrounded 
by a hood to shield it from direct rays. An oscilloscope designed 
according to the general principles outlined here may be used for 
exhibiting distinctly visible waves of speech and music to a group 
of 20 or 30 persons. When the room illumination is decreased, the 
visibility improves rapidly, so that the waves may be observed by 
much larger groups. 

REFERENCE 

1 WENTE, E. C., AND THURAS, A. L. : "Moving Coil Telephone Receivers and 
Microphones," /. Acoust. Soc. of Arner., Ill (July, 1931), No. 1, p. 44. 



SOME TECHNICAL ASPECTS OF THEATER OPERATION* 

H. M. WILCOX AND L. W. CONROW** 

Summary. The various technical phases of theater operation, grouped under 
the headings (1) projection, (2) sound, (3) light, power, and heat, (4) building main- 
tenance, are discussed. Particular attention is paid to means of effecting savings in 
the cost of operation, such as by properly choosing the type and voltage of lamps; 
burning the proper size carbons in the proper manner; keeping lamps, reflectors, 
optical systems, and screens free from dust and dirt; selecting the proper kind of 
fuel for the heating system, and properly firing it; paying close attention to the 
maintenance of the theater building, particularly the roof, a rain hazard; and the 
various fire hazards. 

There has been considerable literature on the various phases of the 
technical part of theater operation, much of it very excellent. Most 
of such matter, however, has been devoted to specific details of 
projection, sound reproduction, air conditioning, etc.; and while 
instructive and helpful to some particular theater employees it is not 
particularly helpful to the theater managers. In this paper we shall 
endeavor to give an inclusive but brief outline of the technical prob- 
lems of theater operation with which every capable theater manager 
should be familiar. 

There is an old adage, "If you want a thing done right, do it your- 
self"; but in this highly specialized age this should probably read, 
"If you want a thing done right, hire someone who knows how." 
This may be all very well for the larger theater chains comprising, 
say, ten or more theaters, but these constitute less than thirty per 
cent of all the motion picture theaters in the United States, and the 
managers of the other seventy per cent are in the difficult position of 
being responsible for the proper operation of highly technical equip- 
ment without being in the financial position to employ technical 
assistants. 

The first requisite of a good theater manager is showmanship, 
which implies ability to select programs that will please his clientele, 

* Presented at the Fall, 1934, Meeting at New York, N. Y. 
** Electrical Research Products, Inc., New York, N. Y. 
338 



TECHNICAL THEATER OPERATION 339 

advertise these programs, and get people into his theater. Compared 
with this requirement, the mechanical and technical features of 
operation are relatively small, but not relatively unimportant 
by any means. The smart retailer packs his goods in neat packages 
and displays them attractively. In the show business the picture's 
the goods, the theater's the show window. 

Suppose we start with the purchase of a ticket for admission to a 
"movie" show. Ostensibly we have purchased the right to enter 
the theater and occupy a seat to see the show. As a matter of fact, 
we have purchased considerably more than that. Suppose, for ex- 
ample, that after we are comfortably seated in this theater we notice 
that the picture is not clear and there is an objectionable flicker; 
we have to strain to understand the dialog; after a while the sound 
stops; then the screen becomes dark for a minute or so ; the picture 
resumes with possibly part of it left out; before long we commence to 
get drowsy on account of bad air. Under such conditions, even if the 
picture were good, we wouldn't like it. 

Obviously we have bought something besides the mere right to 
enter the theater and see the show. We have bought the right to see 
the show comfortably, undisturbed, and presented in such a manner 
that we are practically unaware of the mechanics or mechanisms by 
which the show is presented. Annoying distractions detract greatly 
from the value of the picture. 

Let us take a trip behind the scenes and meet some of the problems 
that confront the theater manager in operating his theater so that 
his patrons will receive he maximum satisfaction and enjoyment 
from the entertainment without distracting annoyances. We shall 
assume that the pictures and the program have been bought and 
paid for, and delivered to the theater; furthermore, that the prints 
are satisfactory both as to picture and sound. The theater, as a 
machine, must be ready for their presentation on time and to the 
satisfaction of the audience. 

The various technical phases of theater operation may be grouped 
under the following general headings : 

(1) Projection. 

(2) Sound. 

(3) Light, Power, and Heat. 

(4) Building Maintenance. 

Each of these will now be discussed in turn. 



340 H. M. WILCOX AND L. W. CONROW [j. s. M. P. E. 

PROJECTION 

The ultimate in projection is to make the patron become mentally a 
part of the story of the picture, with total absence of either conscious 
or unconscious eye-strain. The creating of the illusion of reality 
requires making the two-dimensional scene on the screen assume the 
illusion of three dimensions, and with proper screen illumination 
this effect can be secured to a remarkable degree. 

The screen should appear to be evenly illuminated from every seat, 
and the amount of reflected light should fall between certain definite 
limits. When the reflected light is too great the eye becomes "over- 
loaded"; the pupil contracts, and there is a resulting loss of the fine 
gradations of contrast. When too little reflection occurs, the eye 
responds oppositely and the picture becomes "flat," losing contrast 
and whatever stereoscopic effect may be created by careful lighting. 
Either under- or over-illumination may cause physical discomfort 
and possible damage to the eye and its associated nerve system. 
Not infrequently you hear people state that "movies" always make 
them sleepy. In many cases this is the result of improper projec- 
tion. 

We have recently made a study of screen illumination in a large 
number of theaters. This study consisted of the measurement of the 
amount of light which is projected to the screen by each projector and 
the measurement of the amount of light reflected from both the right- 
hand and the left-hand side of the screen, using the light source of 
each machine. Tests were also made of the maximum point of focus, 
for travel-ghost, and for spherical and chromatic aberration, and for 
the proper curvature of lens by use of the standard lens measure. 

Not in one single case was it found that the screen illumination 
from the two projection machines was the same, and variations be- 
tween machines were found to be as high as 50 to 100 per cent. These 
results were caused mainly through incorrect calibration of ammeters, 
generator commutators scored or having high mica, ballast resistor 
connections imperfect, improperly adjusted shutters, faulty optical 
alignment, pitted reflectors or condensers, or dirty projection 
lenses. 

Another matter of considerable importance is picture size. Sight- 
lines and viewing angles must be given careful consideration in 
determining the size and the placing of the screen. Quite a usual 
fault in small theaters is the use of screens that are too large. This 
tends to dilute the intensity of the light on the screen with a result- 



Dec., 1934] TECHNICAL THEATER OPERATION 341 

ing impairment of definition, or else an unnecessarily high current 
consumption in older to increase the light intensity. Also, the larger 
the picture the more apparent are defects of projection, such as jump, 
weave, graininess, and other film imperfections. 

The condition of the screen is, of course, an important factor in 
maintaining a satisfactory degree of illumination of the picture. In 
this regard the screen manufacturers have a great opportunity for 
developing a screen material with an adequate reflecting surface at a 
price which will enable exhibitors to replace screens at more frequent 
intervals than is the case at present. Some sacrifice of initial reflect- 
ing power would be permissible if screens could be obtained at a low 
enough cost to peimit more frequent changing, thereby raising the 
general average of screen illumination. 

The complete projection system is a combination of mechanical 
and electrical equipment. The various working parts of such a 
system are designed to operate most efficiently when adjusted and 
maintained within the limits prescribed by the manufacturer. The 
wear and tear on a projection machine is abnormally high under 
constant use due particularly to the intermittent mechanism 
and the large amount of current used, with resulting high tempera- 
tures. 

The condition of the intermittent mechanism should be watched 
closely as worn intermittents not only reduce the life of the projector 
head but also the life of release prints. The cost of release prints 
runs into millions of dollars a year, and even a 10 per cent increase 
in their life would mean a substantial saving which eventually would 
accrue to exhibitois, because they, after all, are the ones who foot the 
bill for the entire cost of pictures. The proper maintenance of the 
power generating equipment is an important factor in maintaining 
projection at a high standard of excellence. 

The theater personnel assigned to the operation of the projection 
equipment should be trained men ; definite routines should be estab- 
lished for the maintenance of the equipment, and certain standards 
established against which actual performance can be checked from 
time to time. The Projection Practice Committee of the S. M. P. E. 
have made substantial progress in the establishing of standards. 
The task now appears to be to get exhibitors to adopt these 
standards and to establish simple methods b/ which theater man- 
agers can check the performance of their projection equipment 
against the standards. 



342 H. M. WILCOX AND L. W. CONROW [j. S. M. P. E. 

SOUND 

The picture is enlarged from the film to the screen a few hundred 
times. Sound, on the other hand, is amplified several million times 
from the initial impulses at the photoelectric cell to the time it is 
projected from the loud speakers. As a consequence, any imperfec- 
tions entering into the reproducing apparatus have a much greater 
effect in deteriorating the quality of sound reaching the audience 
than is the case with picture projection. 

In order to have a full appreciation of the importance of adequate 
maintenance of sound equipment, which is the most highly technical 
device of any theater apparatus, it is desirable to have some knowl- 
edge of the nature of sound. 

When you hear a note struck on a piano you know that it is a 
piano. The same note on a violin would sound differently. What is 
it that makes it possible for you to recognize whether the tone origi- 
nates from a piano or a violin? 

Sound has its origin in vibrating bodies. The atmosphere exerts a 
definite, uniform pressure on all bodies with which it is in contact. 
When vibrations have been communicated to the atmosphere they 
cause rapid fluctuations in this pressure, and these changes of pres- 
sure striking the ear-drum result in the sensation which we know as 
sound. 

The rapidity with which these vibrations strike the ear causes the 
sensation which is known as tone or pitch. The intensity with 
which these vibrations strike the ear causes the sensation which is 
known as volume or loudness. You may perhaps remember how, 
as a boy, walking along the street you might drag a stick lightly along 
a picket fence; if you would start to run, the sound would immedi- 
ately go up in pitch ; if you pressed the stick harder against the fence 
it would become louder. 

If you have ever noticed the piano keyboard you will remember that 
it is divided into a number of uniform sections comprising eight 
white keys and five black keys. Each of these sections is identical to 
the other except that the pitch or tone of each adjacent section is 
what is known as one octave higher or one octave lower than the 
next one. The perfect human ear can hear sounds over a range of 
approximately ten octaves. Technically this is known as the sound 
spectrum, and the audible spectrum encompasses a range of from 16 
vibrations per second to 16,000. One of the highest pitched sounds 



Dec., 1934] TECHNICAL THEATER OPERATION 343 

which the ear can hear is the tinkling of keys, while the rumbling of 
the lowest organ note is about the lowest pitched sound which the 
ear can detect. 

Variations of loudness range from the faint rustling of leaves up to 
artillery fire; that is, to the point where the sensation changes from 
one of hearing to one of feeling. In terms of energy this is a variation 
of many million times. 

When one note is struck on the piano, say, middle C, which is a 
pitch resulting from the vibrations of the piano string of about 250 
times per second, a strange thing happens. You hear not only the 
tone represented by 250 vibrations per second but you hear also some 
of 500, some of 1000, some of 2000, some of 4000, some of 8000, and 
perhaps some of 16,000. These are known as overtones or harmonics. 
The reason that you could determine that a certain tone came from a 
piano or a violin is the fact that there were different combinations and 
intensities of these harmonics or overtones which struck your ear 
drum. It is this fact which gives character to sound. If any of these 
overtones are missing or over-accentuated the sound will not be 
natural. 

Any mechanical or electrical device must be capable of recording 
and reproducing a sufficient range of vibrations to make the repro- 
duced sounds appear to be natural. Bearing in mind that the ear 
can hear a range of about ten octaves the apparatus which records the 
sound and which reproduces it must have the capacity of handling 
this range for the sound to be completely natural. The old mechani- 
cal phonograph of ten years ago could handle about four octaves. 
The electrical phonograph of 1925 could reproduce about five octaves. 
You perhaps remember in the early days of talking pictures how 
frequently the characters seemed to lisp. This was caused by the 
inability of the machine to reproduce the sibilants which are sounds 
of relatively high frequency or vibrations per second. 

Since the introduction of sound pictures commercially about 
eight years ago there has been a continuous improvement in both 
the tone range and the volume range of sound recording and reproduc- 
tion, so that today the standard of sound reproduction in theaters 
represents about 80 per cent of all that the ear can hear. 

Fortunately, in sound reproducing apparatus there are few moving 
parts, so that there is relatively little mechanical wear and tear. 
In maintaining a high quality of sound, cleanliness is next to godli- 
ness. Probably the most vital part of the apparatus is the optical 



344 H. M. WILCOX AND L. W. CONROW [J. s. M. P. E. 

system and exciting lamp which generates the initial power en- 
tering into the sound reproducing system. A very small amount 
of dirt on the exciting lamp or the optical system, or a very small 
maladjustment of its alignment or focus can have a very serious 
effect on the quality of the sound reproduced. 

It is very necessary that the film travel at a smooth uniform speed 
through the exciting lamp beam, otherwise objectionable flutter will 
appear in the reproduced sound. Consequently, the film-driving 
mechanism of the projector and sound head must be kept in first- 
class condition. 

In the amplifying system the photoelectric cell and the vacuum 
tubes are the equivalent of moving parts, but the motion is electrical 
and not mechanical. However, this electrical motion taking place 
within the photoelectric cells and vacuum tubes does cause wear and 
tear, and these should be watched closely for condition. As a rule, 
deterioration of vacuum tubes takes place very gradually up to a 
certain point and then becomes exceedingly rapid. In general, 
properly manufactured vacuum tubes of high quality will last a 
theater running 60 hours a week for over a year. 

Troubles from defective loud speaker units are usually not immedi- 
ately apparent, particularly where there are two or more units in use. 
It is advisable occasionally to run one reel on each machine and listen 
to the reproduction from each speaker unit with the others cut out. 

The exhibitor owes it to his audience to deliver faithfully all that 
the producer of pictures is delivering to him on the sound record. 
To a considerable measure the reproducing apparatus in theaters 
is an extension of the recording apparatus in studios. The producers 
are continuously striving for improvement in sound recording, and 
it is highly important that the reproducing apparatus be kept in 
step with recording technic in the studios, to the end that the efforts 
of the producers in improving their product will be translated into 
increased box-office receipts. 

LIGHT, POWER, AND HEAT 

A periodic survey of the light, power, and heating plants will 
provide a substantial saving in the cost of operation. We recently 
completed a survey in 14 theaters belonging to a chain which main- 
tains relatively high operating standards. The following summarizes 
the reports on the actual conditions found in these theaters, and refers 
to facts that are of distinct interest to theater managers generally : 



Dec., 1934] TECHNICAL THEATER OPERATION 345 

"The average indicated net saving per theater in current, carbon, 
and lamp replacement costs, expressed in terms of a percentage of 
the respective annual light and power bills, is 13.4 per cent. This 
represents a total first year saving, after deduction of the cost to af- 
fect the savings, of $12,884. 

"The average indicated net saving per theater in fuel consumption 
and fuel costs is 23 per cent. This represents a total first year saving, 
after deduction of cost of necessary indicating instruments, of $5873. 

"These estimates are conservative. Recommendations are re- 
stricted to those considerations involving little or no initial expense. 
No attempt has been made to alter existing policies in regard to 
amount of light and heat used. Considerations effecting reductions 
in power consumption by motor overhaul, adjustment, and lubrica- 
tion also effect equipment savings by reducing fire hazard, avoiding 
equipment breakdown, and minimizing equipment replacement costs." 

Reduction in current consumption for lighting is based upon the 
following considerations : 

The light output per watt of standard incandescent lamps increases 
with increase in wattage size of lamps. One 100-w. lamp produces 
42.6 per cent greater light than is produced by four 25- w. lamps, while 
one 75-w. lamp produces only 1.3 per cent less light than do four 25-w. 
lamps. It is possible, where consistent with appearance and effect, 
to produce the same amount of light at a lower current consumption 
by substituting a smaller number of higher wattage lamps. Reduction 
in the number of lamps in use reduces the cost of lamp replacement. 

The actual wattage consumed by a lamp, its life, and its light 
output depend upon the voltage of the circuit on which it is operated. 
A 120-v. lamp used on a 110-v. circuit consumes only 88 per cent 
of its indicated wattage, lasts 320 per cent as long, and gives only 73 
per cent as much light as it would on a 120-v. circuit. A 110-v. 
lamp used on a 120-v. circuit consumes 115 per cent of its indicated 
wattage, lasts only 30 per cent as long, and gives 135 per cent as much 
light as it would on a 110-v. circuit. The determination of lamp 
voltage thus depends upon the cost of lamps as compared with cost 
of current; for it is possible to save on lamp replacement cost by 
selecting lamps of a voltage greater than the voltage on which they 
are to be used, or to save on current cost by selecting lamps of a volt- 
age lower than that of the supply voltage. In most theaters, the 
cost of current outweighs the cost of lamps, and lower voltage lamps 
are more economical. 



346 H. M. WILCOX AND L. W. CONROW [j. s. M. P. E. 

Not only must the supply voltage be considered, but also the 
voltage of individual circuits. The voltage of heavily loaded lines 
will be lower than the supply voltage, as will all dimmed circuits. 
It may be necessary for a theater to use lamps of three or four differ- 
ent voltages. Standard lamps are supplied for 105, 110, 115, 120, 
125, and 130 volts. 

Effective light may be as little as 1 per cent of the light actually 
produced. A lamp distributes light almost equally in all directions. 
Unless satisfactory reflecting surfaces are used to redirect light in the 
desired direction, much of the light produced is wasted. Reflecting 
surfaces include ceilings, walls, and floors, as well as reflectors. The 
efficiency of light reflection of these surfaces depends upon the in- 
herent character and brightness of the surfaces and upon their condi- 
tion and cleanliness. The most striking example of waste of light is 
found in theater dome coves. The surfaces at the sides and bases of 
vertically mounted lamps in coves are often rough concrete, covered 
with heavy accumulations of dust. The lamps are covered with 
dust, and the light that finds its way through the tip of the tinted lamp 
is redirected to the auditorium by means of the curved surface of 
the dome, the paint of which is dull with age. Beginning with a 
loss of 30 or 40 per cent due to tinting, another 75 per cent of what 
remains is absorbed by the dust-covered reflecting surfaces. Of 
the little remaining light, part is obstructed by dust on the lamp, 
and as much as 80 per cent of the remainder may be absorbed by the 
dull reflecting surfaces of the dome. 

Reflectors are available with efficiencies as high as 95 per cent, 
while the efficiency of flat white painted surfaces may be as high as 85 
per cent. In the above example, clean lamps in clean, efficient reflect- 
ors suited to the lamps in use, directed into a white dome, would 
deliver to the auditorium more than 60 per cent of the light produced. 

Reflectors should be used wherever possible to avoid waste. Re- 
flecting surfaces, marquee, soffit, space behind attraction letters, 
coves, ceilings, walls, and even floors should be kept as clean and 
bright as possible. Light-transmitting media such as globes, fix- 
tures, panels, attraction letters, and the glass of the lamps should be 
kept clean and free of dust. 

Tinted lamps cost more, produce less light, and burn fewer hours 
than standard lamps. Light effects may be produced by using 
color caps, by tinting the glass of fixtures, panels, etc., by using vari- 
ously colored overlays, and by using colored drapes. 



Dec., 1934] TECHNICAL THEATER OPERATION 347 

Some theaters in this circuit use tinted 25-w. lamps behind tinted 
glass in exit fixtures. The use of a tinted lamp in this way causes a 
loss of light equal to the difference between a 25-w. lamp and a 15-w. 
lamp. This is a loss of 40 per cent in current and 20 per cent in 
lamp replacement cost. 

The majority of lamps in use in these theaters are bare, low-wat- 
tage, tinted, 120-v. lamps, operating on circuits between 110 and 115 
volts. If these lamps could be replaced with fewer, properly re- 
flected, higher- wattage clear or white frosted, 110-v. or 115-v. 
lamps, current consumption for all lighting would be reduced 40 per 
cent. 

Other considerations effecting reductions in current consumption 
include reduction of line loss in overloaded circuits and dimmed 
circuits; replacement of high- wattage lamps in exit lights and 
indicators; reduction of the number of units on one switch; loca- 
tion of switches conveniently to encourage turning off lights; and re- 
placement of inefficient fixtures, such as the channel type of attrac- 
tion sign letter, which is costly in current consumption and lamp re- 
placement cost. 

Projection accounts for a large part of power consumption. Con- 
siderations affecting current consumption are, type, size, condition, 
and cleanliness of screen; type, adjustment, condition, and cleanli- 
ness of reflectors and lenses ; size, kind, adjustment, and operation of 
carbons; condition and operation of feed motors, jaws, contacts, 
feed rollers, etc. Type of screen is determined by the shape of audi- 
torium and angle of projection. Size of screen affects light density 
per unit area. Condition and cleanliness affect reflectivity of screen 
and consequently affect the necessary light production at the arc. 
Reflectivity of a new screen is from 77 to 85 per cent. The normal loss 
in reflectivity in one year is 50 per cent. This represents a current 
consumption loss at the arc of from $15 to $65 a month, where the 
average cost per kilowatt hour of current is S 1 /^ cents. Types of 
reflectors and lenses are governed by the length of throw and the 
size of picture on the screen. Adjustments of reflectors and lenses 
affect adjustments of carbons. Condition and cleanliness of re- 
flectors and lenses affect efficiency of light transmission. Size and 
kind of carbons affect current and carbon consumption. Oversize 
carbons increase current consumption and reduce carbon consump- 
tion, but increase carbon consumption cost. Undersize carbons in- 
crease current consumption and increase carbon consumption and 



348 H. M. WILCOX AND L. W. CONROW [J. s. M. p. E. 

carbon costs. Adjustment of carbons affects current consumption 
greatly. An out-of -position adjustment of 1 / 8 inch may increase the 
current and carbon consumption 10 per cent. A common fault is 
reducing the arc-gap between positive and negative carbons. This 
increases the light, but causes excessive current and carbon consump- 
tion and burning of carbons and reduces the voltage at the arc. 
This, in turn, causes faulty operation of the carbon feed motor. Ir- 
regular feed produces irregular light on the screen and necessitates 
periodic, inefficient hand adjustment. 

Electrical contacts, jaws, rollers, motors, etc., must be kept clean 
and in good operating condition to avoid losses in current and carbon 
consumption. Projecting single reels instead of double reels in- 
creases the current and carbon costs at least 5 per cent. 

Light and power billing rate schedules should be given constant 
consideration. Billing depends not only upon the amount of current 
consumed, but also on the manner in which it is used. Alternate 
rate schedules are usually available, and should always be con- 
sidered in any change in policy affecting current consumption. 
A theater on an annual demand rate may find it to its advantage to 
elect to have applied to its billing a flat rate when its operating 
policy establishes a high demand for only a short period dur- 
ing the year. On the other hand, the theater may so adjust its 
policy as to maintain a fairly constant demand and so control its 
billing. 

Heating efficiency depends largely upon the selection of fuel for 
which the boiler was designed and the complete combustion of the 
fuel in the presence of the heating surfaces. Complete combustion 
depends upon the proper mixture of fuel and air. It is possible, by 
means of an Orsat apparatus and a thermometer so to adjust air mix- 
ture and draft as to produce nearly complete combustion. Fuel 
should always be purchased on specifications. 

Except where burners were found defective, it was possible to 
attain combustion efficiency of 75 per cent for oil-burning and coal- 
stoker installations. Hand-fired furnaces depend so much upon the 
ability and interest of the fireman, that although high efficiencies 
were attained during tests, the anticipated savings were based upon 
much lower efficiencies. A small bonus to the fireman based on fuel 
consumption with maintenance of proper temperature in the audi- 
torium may be an effective economy. 

Other considerations for which savings are indicated but not 



Dec., 1934] TECHNICAL THEATER OPERATION 349 

readily calculable are insulation of piping, shielding of radiators, 
improving condensate return systems, etc. 

BUILDING MAINTENANCE 

Building maintenance needs less frequent attention than any 
other parts of theaters, and consequently the tendency to neglect is 
greater. Being a place of public assembly, safety and comfort of 
patrons is the first consideration. Such things as exit doors, fire- 
escapes, stairs, carpets, fire extinguishers, and electrical apparatus 
and wiring should be inspected at regular and fairly frequent inter- 
vals. An excellent plan is to have a check list of all such items and 
a regular time set each week or each month for a building inspection. 
An hour or so is all that would be necessary except in the very 
largest houses, and there is considerable advantage in the manager 
making these inspections personally. He could check the house- 
keeping, such as cleanliness, condition of plumbing, decorations, etc. 

Twice a year, in spring and fall, there should be a thorough in- 
spection of roof, gutters, and drains. Roof deterioration is insidious, 
and water damage inside the building is apt to be very costly. In a 
recent case an organ was almost ruined from a leaky roof which 
suddenly developed during an exceptionally heavy rain and wind 
storm. Roof repair or reconditioning should be made on definite 
specifications, and in general the highest bidder will probably prove 
the most economical in the long run. Every fall there should be a 
thorough inspection of the heating system, including cleaning of 
flues with special reference to fire hazards. 

As we consider each of the many problems which a theater man- 
ager must deal with, it is quite evident that to handle the more 
involved technical problems of maintenance efficiently he must look 
for assistance and advice of an engineer or group of engineers. He 
can, of course, secure information from many individual sources, 
but he can not be certain that the information he receives applies 
to his individual problem. Only a careful investigation and study 
of conditions in the theater will produce the best and most economical 
solution. The question is, how much will maintenance of this 
character cost. It will cost something, of course, but in the long run 
the savings from efficient handling of maintenance will result in a 
reduction of direct operating expenses, longer life of equipment, and 
satisfied patrons, and will make the net expenditure a very small 
percentage of the cost of operation. 



PROBLEMS IN MOTION PICTURE ENGINEERING* 
A. N. GOLDSMITH** 

Summary. After defining motion picture engineering as the production of an 
acceptable semblance of reality, there are discussed the functions of the engineer and 
the artist, as well as certain aspects of parts engineering, including the improvement 
of the film, the camera, lenses, studio lighting, sound recording, laboratory processes, 
theater monitoring and maintenance, sound reproduction, theater architecture, and 
other allied matters. An open mind and a determined attempt favoring continuous 
evolution of the art are urged. 

The problems of any branch of engineering depend upon the aims 
of that branch. While it would be most difficult, if not impossible, 
briefly to define the aims of mechanical or electrical engineering, 
for example, it is fortunate that a reasonably acceptable definition 
can be contrived for motion picture engineering. It is the presenta- 
tion of a real or imagined happening to the audience in such approach 
to perfection that a satisfactory illusion of actual presence at the 
corresponding event is created. Briefly, it is the production of an 
acceptable semblance of reality. 

It might be objected that exact replicas of reality will not give a 
desired dramatic or comic effect, and that is quite true. On another 
occasion, I defined the motion picture industry as "vendors of 
illusion and sellers of glamour." This definition need not be changed. 
However, the task of the engineer is to create the illusion of reality. 
It is for the playwright, the director, the actor, and any other artists 
who are involved to provide the glamour by intensifying or subduing 
or otherwise modifying the reality to be recorded and reproduced so 
that the most satisfactory audience response shall be achieved. It 
is well for the industry to keep this point in mind. If we desire 
in the theater suppressed or heightened impressions, those who 
provide the raw material for the engineer to work upon must arrange 
for this and specify the desired effects clearly. The engineer can help 
greatly, but it is not his function to control tempo, the aesthetics of 
lighting, the tone of the actors, and the multitude of other necessary 

* Presented at the Fall, 1934, Meeting at New York, N. Y. 
** Consulting Engineer, New York, N. Y.; President, Society of Motion 
Picture Engineers. 
350 



PROBLEMS IN MOTION PICTURES 351 

artistic factors. Occasionally there will be found an engineer who is 
also an artist, but in general it is well, as a practical proposition, for 
the two groups of workers to "stick to their own last" and to become 
more nearly perfect in their respective tasks through specialization. 

In considering the further problems of motion picture engineering, 
there must not be assumed any implied criticism of the fine work 
which has been done in the past. The results already available are a 
convincing testimonial for what has been done by the technicians. 
Yet the motion picture industry can not stop at that point. No 
industry that hopes to retain public patronage on so vast a scale can 
afford to be smug and self-satisfied. We have not yet reached our 
goal and perhaps we never shall. 

Motion picture engineering falls into two broad divisions system 
engineering and parts engineering. Historically the latter generally 
comes first. Individual parts of the complicated series of devices 
necessary for the final presentations to the public are invented; 
are built in crude form; are tested and found wanting in some 
respects; and are improved in a series of steps toward an acceptable 
performance. But parts engineering is not enough. By coordinating 
each device with the others, and by fully appreciating the way in 
which each part fits into the entire structure, greater effectiveness of 
operation, superior results, and marked economies generally result. 
We may safely assume that every device now used by motion picture 
engineers can be improved, that new devices for functions not yet 
filled can be contrived, and that the relation of each part of the sys- 
tem to the whole system of audio-visual recording and reproduc- 
tion requires study and consequent technical development. 

In the brief presentation which is the subject matter of this paper, 
only parts engineering can be conveniently considered. Even so, 
the subject is so vast that only a brief and partial summary can be 
given. It is obvious that present and possible future problems can 
be listed but that their solutions can not be given to do so would be 
to overleap human mental and time limitations. 

Considering first the raw material and very foundation of this 
branch of engineering, namely, the photographic film, we can fairly 
ask whether the present film materials are the best that can be ex- 
pected. Are they as durable, as economical, as well adapted to high- 
speed projection and intense heating, and as free from dimensional 
changes with time as may be desired? Has graininess been reduced to 



352 A. N. GOLDSMITH [j. s. M. P. E. 

a completely satisfactory minimum (even for such special applications 
as process shots), and has speed been raised to the point where the 
cameraman is practically untrammeled in his work even under such 
unfavorable conditions as frequently challenge the newsreel worker? 
Can we be said to have film that is suitable for color photography 
that is, for the reproduction on the screen of the full colors of the 
photographed scenes? Has film susceptibility to other forms of 
energy than light been reduced to a minimum? Can we add to the 
already great accomplishments along these lines? 

The engineer, contemplating the awkward structure of a blimped 
or sound-proofed camera (the camera itself being an object of con- 
siderable size and weight), wonders whether something more con- 
venient can be contrived. Silence in operation, compactness, 
continual accessibility of all adjustments and simplification of such 
adjustments, and generally increased mobility present attractive 
possibilities. Some workers are prepared to accept the theory that 
the optics of photographic lenses are not capable of basic improve- 
ment, but if some way to diminish the large number of lenses that 
are required in the studio for close-ups, medium, and long shots could 
be contrived, it would be a step forward. Zooming by more con- 
venient and automatic means is desirable. And the present methods 
of achieving angle shots, following shots, and the like leave room 
for improvement, as any one must admit who has watched the opera- 
tion of the mammoth cranes and dollies now in use. 

It may also be fairly assumed that the last word has not been spoken 
in studio lighting. Could not studio lighting be so arranged that 
each set does not require inevitably the shifting of practically every 
lighting unit? Could not a semi-standardized lighting plan be 
adopted under which the lighting could be controlled by manipulating 
a modern control board rather than by dragging tons of equipment 
around the studio? The control of the direction of incident light, 
its amount, its diffision, and its color (where that factor is of im- 
portance) all present to the engineer matter for further consideration. 
Closely associated with such problems are those of make-up, set 
construction and finish, and costuming. It is possible that new ma- 
terials will be found for set construction which will present a more 
desirable combination of optical, mechanical, and acoustical char- 
acteristics than those now available. 

The recording of sound is well done, considered as a young art. 



Dec., 1934] PROBLEMS IN MOTION PICTURES 353 

But the evolution of more compact and lighter recording equip- 
ment, the use of more economical recording methods, the develop- 
ment of more convenient and simpler methods of editing and re- 
recording or "dubbing," and methods of recording that enhance 
auditory perspective are desirable. 

When the processing of film by the laboratory is considered, it 
seems clear that a group of methods will be evolved whereby the pre- 
cision and uniformity of the product can be further increased. 
Automatic processes are entirely in order in dealing with the vast 
quantities of film that are handled by a laboratory, and one may 
look forward to the time when everything, from exposure time and 
developer concentration and temperature to the condition and 
packing of the finished film, will be handled and controlled auto- 
matically. The devices for the purpose may even be provided with 
"checking controls," indicating when the control device in question 
is out of order and then providing a corresponding alarm. 

By a simple extension of the thought, one can imagine film ex- 
changes wherein the inspection of film and the repair of at least some 
defects can be automatic or semi-automatic. Considering the way 
in which film is sometimes mistreated by the user, one might face- 
tiously add that there is need for a device that automatically charges 
the delinquent user for the damage he has done and also collects 
the full amount promptly and relentlessly. 

Closely related to some of the problems mentioned are those of 
the theater. Present methods of monitoring both picture and sound 
leave something to be desired. Substantially complete silence in the 
projectionists' room is needed if convenient monitoring through 
large open ports is to be possible. In the meantime, a type of port 
that lets out light without absorption, but not sound, may be de- 
veloped. Screen illumination remains inadequate in some cases, and 
no standardized method of checking the condition of screens as often 
as may be desirable has been worked out. A simple and automatic 
method of so doing would be a help to the exhibitor whose entire 
salable output passes through the proscenium arch. The color of the 
projector illuminant and its stability and economy are under active 
study and merit such attention. The reduction of film wear by ap- 
propriate construction of projectors and by automatic or semi- 
automatic supervisory methods presents a real problem. And, 
needless to say, film breakage during projection is, in the engineering 



354 A. N. GOLDSMITH [j. s. M. p. E. 

sense, entirely inexcusable. The projection of color pictures will 
bring in a number of new problems of projector construction, of 
screen surfacing, theater lighting, and other arrangements. If ever 
three-dimensional pictures are to be available, it is likely that a 
number of radical changes in theater construction and equipment 
will be involved. 

The reproduction of sound in theaters has also steadily improved. 
Problems of increasing further the dynamic range of reproduction, 
of establishing and maintaining reproduction of improved fidelity, 
of achieving stereosonic reproduction (i. e. y sound reproduction with 
auditory perspective), and of reproducing speech and sound with 
equal satisfaction assuredly exist and invite further effort. Closely 
associated with all the preceding is the general question of motion 
picture theater construction. Some architects skilled in the related 
problems have vigorously maintained that the present forms of 
theater design are not technically sound, and have proposed other 
more or less plausible substitute constructions. Speaking for a mo- 
ment as a theatergoer, something is certainly to be desired to permit 
the blinking and half -blind patron, entering a darkened theater from 
a sunlighted street, first to accomplish the difficult feat of locating an 
unoccupied seat and then to reach it with minimum damage to the 
footwear, other impedimenta, and good nature of the seated occupants 
of that row. And, as has been clearly pointed out recently by a pro- 
found thinker, there is need for solving the old problem of the theater- 
goer who enters at the middle of a picture and has the weird experience 
of "enjoying" a slice of life that begins with the death of a character 
and ends with his birth. Perhaps even that puzzle has a partly 
technical answer. 

As may have been gathered, all the preceding discussion is really 
more a plea for an open mind, willing effort, and resourcefulness on 
the part of the engineer than a complete technical summary of prob- 
lems in the motion picture field. If you are satisfied that much 
has been accomplished and that much remains to be done, the purpose 
of this discussion will have been achieved. In that event, motion 
picture engineering will continue to be the loyal friend and tireless 
servant of the industry and the public, and will always, as now, 
deserve to be fostered and encouraged by the industry and the public 
alike. 



Dec., 1934] PROBLEMS IN MOTION PICTURES 355 

DISCUSSION 

MR. RICHARDSON: You mentioned only camera lenses and various problems 
in connection with them. There is another lens that deserves attention. I am 
more and more impressed with the fact that the condenser is by no means what 
it should be, and that due to that fact we are wasting a great deal of light. 

MR. SCHLANGER: The difficulty of being able to find one's seat in the motion 
picture auditorium has been largely overcome. In the past, direct and spot 
illumination was used, and during the performance it was necessary to switch 
off the lights because of the distraction they caused in competing with the screen 
illumination. The proper intensity and color of evenly distributed indirect light 
will afford ample illumination for getting about the theater, and will not in any 
way interfere with screen definition or the ability to view the screen comfortably. 
Low chair, stair, and wall lights below the line of vision are effective also for 
auditorium illumination. 

The problem of adjusting the eyes to the sudden change of intensity from that 
of the street to that of the auditorium is soluble in two ways : first, by a higher 
permissible intensity of light in the auditorium proper; and second, by having 
at least two intermediate stages of light intensity between the street and the 
auditorium, using the lobbies, foyers, or other spaces in the same way as com- 
pression chambers are used in under-water construction. 

MR. BLIVEN: I am quite interested in the reduction of sound through the 
projection port, and particularly of the audience's reaction to the noise of the 
projectors and the sound of the monitoring speaker. Serious work should be 
done on that problem, taking into consideration the dimensions of the ports and 
projection room noises. 

MR. RICHARDSON: If the wall of the projection room is thick enough, say, 
8 inches, and if the two sides of the port are faced with sound-absorbent material 
cut to the size of the light-beam, the sound should be considerably reduced. 
Such a scheme has been tried in a number of theaters, and has proved quite 
satisfactory. 

MR. BLIVEN: I have tried that, at the same time lining the interior with 
sound-absorbing felt, but it was not entirely satisfactory. 



MOTION PICTURE APPARATUS 

A SMALL DEVELOPING MACHINE* 

H. R. KOSSMAN** 

It is the purpose of this paper to describe a small developing machine es- 
pecially suitable for research work and for such cases wherein it is desirable to 
duplicate the conditions that exist in the largest film printing and de- 
veloping establishments. In designing the machine, the first thought was com- 
pactness; not only for the purpose of saving space, but primarily to make it 
possible for the operator of the machine to watch at all times all the phases of 
development from the time of feeding the film into the machine to the final re- 
winding after the film leaves the drying cabinet. 

The machine consists of the following units : 

(1) The developing, hypo, and washing tanks. 

(2) The cabinet, containing the motor drive, motor ventilator, high-pressure 
blower, electrical heating unit for the drying air, air filters, and a com- 
plete switchboard for all the thermostat relays and starters for the circula- 
tion pump motor. 

(3) Drying cabinet. 

In addition, there is a small unit containing the constant level tank, the circula- 
tion pump, and the coil and reheating unit controlling the temperature of the 
bath. 

The dimensions of the smallest machine are 7 feet long, 6 feet high, and 3 feet 
wide. Its capacity, necessarily small, is 650 feet of film per hour, for a develop- 
ing time of four minutes. A slightly larger machine has an output of 1300 feet per 
hour. The machine can be used for developing either positive or negative film. 

The change from positive to negative bath can be effected in two different ways: 
The circulation pump can drain the positive developer from the developing tanks 
and return the bath to the storage tank. Then the negative storage tank would be 
connected to the circulation circuit. Another way to change the positive to 
a negative bath is to change the developing tubes. The tubes are instantly inter- 
changeable, and such procedure may be preferable in many cases especially when 
it is intended to try various developing solutions as for picture and sound. 

The temperature of the developing solution is thermostatically controlled. 
The film passes from one developing tank to the other with the least possible 
exposure to the air. The developing time can be regulated from 4 to 16 minutes, 
by changing from one to the other of the two speeds provided in the machine and 
by lengthening or shortening the film loops in the developing tanks. The de- 
veloping time can be changed in each individual developing tank so that if it is 

* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Andre Debrie, Inc., New York, N. Y. 
356 



MOTION PICTURE APPARATUS 



357 




358 MOTION PICTURE APPARATUS 

discovered in the first or second developing tank that the developing time is either 
insufficient or excessive, it is possible to compensate for the condition in the last 
developing tank. 

In the smallest model there are five developing tubes, followed by one washing 
tube, and finally by five hypo tubes and three washing tubes. At this point the 
film leaves the tubing, its direction of travel is changed, and it is immersed on 
the opposite side of the machine in three additional washing tubes. After leaving 
the last washing tube and before entering the drying cabinet, the film passes a high- 
pressure blower, which is so constructed that the water is blown off entirely with- 
out causing the undesirable spots produced by the so-called "squeegees." The 
film then enters the drying cabinet, forming four loops. The temperature of the 
drying cabinet is also thermostatically controlled. After leaving the drying 
cabinet, the film is rewound exactly at the same point where it was fed into the 
machine. 

Tht machine is equipped with a system for filtering the air before heating it for 
the dryiiig. For locations where it is necessary to control the humidity of the air, 
as is especP'^v the case in the tropics, a refrigerating system and closed air cir- 
cuit are proved. The air is cooled ; the excess moisture is eliminated ; it is then 
heated and passed through the drying cabinet, the same air being returned to 
the refrigerating unit. Such a procedure makes it possible to condition the 
air perfectly with a comparatively small refrigerating unit. 

The temperature control of the bath, the circulation pump, and the constant- 
level tank are built in one unit. By a pipe connection, preferably of rubber 
or lead, the developing solution passes into the constant-level tank by gravity, 
the tank being so arranged that it automatically refills the developing tanks if the 
developing solution is reduced by evaporation or by being carried over into the 
washing and hypo tanks by the film. The tank supplies only fresh developer. 
Below the constant-level tank is the temperature control tank, which also contains 
the circulation pump. The temperature of the bath is controlled by a copper coil, 
which uses either city water or, if conditions make it necessary, artificially cooled 
water. This unit is equipped also with a heating unit and a very sensitive thermo- 
static control so that the temperature can be maintained constant within V 2 
degree. 

The machine has been designed so as to require a minimum of labor in installing 
it. Normally, the plumbing for the water system, and the pipe connections 
for the storage tanks and circulation unit must be provided by the purchaser. 
However, in the latest design, all connections to and from the storage tank and 
circulation unit are made by rubber pipes delivered with the machine, a procedure 
that greatly reduces the cost of installation. Only one feed line for the electrical 
current to the switch-board is necessary. 

The material used in this machine is Monel, Allegheny, and hard rubber. The 
tanks are made of ebonite, and are easy to clean and, as mentioned above, to 
interchange. 



THE NEW KLIEGLIGHT * 
H. KLIEGL** 



Twenty-five years ago the Klieglight was used extensively and successfully in 
indoor photography, following which came the high amperage arc spotlights. 
Then, for a long time the only developments that occurred were improvements 
in the general design of the equipment then in use, principally mechanical im- 
provements. With sound came incandescent lighting and high- wattage lamps ; 
and the principle of sun arc was widely adopted and is now universally used. 

Chief among the disadvantages of the latter are its size, and the requirement 
of using "niggers" and "gobos" for subduing false light and for shaping the beam, 
and of "cellos" to render the field of light more uniform a costly means of 
control. In 1932 a great deal of experimenting was done with differently shaped 
and designed reflectors, leading ultimately to the new Klieglight. 

The rhodium reflectors that were used proved extremely su ^ssful. The 
accuracy of these electrolytically deposited reflecting surfaces w far greater 
than that of spun or cast surfaces, and far greater durability was ._ .hieved. The 
reflection factor was about 74 per cent, 
and the surface could withstand the 
heat of a 2000-watt spotlight bulb, in 
any kind of hood designed for that size 
of lamp. Fig. 1 shows the original now 
popular down-light employing a 250- 
watt bulb, the main reflector of which is 
elliptical in design. 

In the elliptical reflector the light 
emanating from the lamp filament is 
collected and then projected to the con- 
jugate focus. In the new unit, however, 
the rays are intercepted by a flat rhodium 
mirror reflector placed at the exact center 
of what would be the completed ellip- 
soid, as shown in Fig. 2. 

The action is as follows (Fig. 2) : light 
ray A passes from the lamp to the reflec- 
tor, then to the flat mirror, then back 
through the lamp, and out through the 
exit hole in the reflector a two-reflec- 
tion ray. There are, in addition, any number of four-reflection rays, as, for 
example, ray B, which missed the exit opening and had to travel through an- 
other series of reflections before emerging from the unit. 

Upon leaving the reflector the rays are picked up by a set of lenses which 




FIG. 1. The original unit, em- 
ploying a 250-watt lamp and ellipti- 
cal reflector. 



* Presented at the Spring, 1934, Meeting at Atlantic City, N. J. 
** Kliegl Bros. Stagelighting Co., New York, N. Y. 

359 



360 



MOTION PICTURE APPARATUS 



[J. S. M. p. E. 



converge the rays into a crossing beam, permitting the light to pass through 
an opening in the ceiling only 4 inches in diameter. The unit has an efficiency 

of 24 per cent, approximately three 
times that of the standard spotlight. 

Fig. 3 shows the next step in the de- 
sign of the Klieglight, which is practi- 
cally a reversal of the down-light. The 
output of the exit hole is placed at the 
center of the reflector, which is located 
exactly as described before, and the 
lenses are placed beyond the conjugate 
focus. The exit hole is large enough 
to permit maximum pick-up by the lens 
of the beams suffering only one reflec- 
tion. The remainder of the light, miss- 
ing the lens, is redirected by the mirror 
back into the reflector, which, in turn, 
sends it eventually out the exit hole 
into the lens. The efficiency of the 

unit is approximately 30 per cent as compared with 24 per cent for the previous 
lamp. 

However, difficulty was encountered in attempting to employ lamps of higher 
wattage, containing larger filaments and entailing a corresponding loss of light 
because of the size of the filament, which difficulty, however, was solved by using 
lamps with filaments of the biplane type. However, the lamps had to be burned 




FIG. 2. Reflection of light rays in 
the unit shown in Fig. 1. 



Q 





FIG. 3. A development of the Klieglight, prac- 
tically a reversal of the down-light. 



base downward, and an additional hole had to be made in the top of the reflector 
in order to be able to insert the lamp in the socket. While studying the output 
of the lamp it was found that if the filaments were faced toward the sides of the 
reflector, the pick-up of the latter would amount to nearly 90 per cent of the 
light emitted by the filament, all of which is directed by the reflector in one 
reflection to the lens. It is actually a fact that in the same reflector 40 per 



Dec., 1934] 



MOTION PICTURE APPARATUS 



361 



cent more light enters the lens when the filament faces the sides of the reflector 
than when it faces the lens. 

A 1500-watt bipost-base up-burning lamp, with a biplane filament in the T-24 
size bulb, was then developed, and the hood of the lamp was again redesigned, 
as shown in Fig. 4. The bulb is designed to operate at any angle within 45 
degrees of the vertical, and by off-setting it in the fashion shown a full 90- 
degree down-tilt is permitted. The filament is placed far down in the tip of the 
lamp, resulting in two advantages: 

(1) There is very little glass inside the reflector system. 

(2) All the blackening of the bulb occurs near the top of the neck, outside 
the reflector, enabling the system to retain its initial efficiency over a 
much longer period of time. 




FIG. 4. The final arrangement of the spot- 
light, employing a 2000-watt bi-post up-burning 
lamp operated 45 degrees from the vertical. 



The lamps are made in both the 1000- and 1500-watt sizes in a T-24 bulb, and 
a 2000-watt size in a T-30 bulb. The centering of the filaments of all three 
lamps is the same. Both the square and iris adjustable shutters are used, as 
well as the single-lens pick-up and control system. The flat mirror reflector 
has been omitted, because the increase of light effected by it was found to be very 
slight in proportion to the direct pick-up. The shutters are at the focal point of 
the lens, and the spread is determined by the distance of the lens from the con- 
jugate focus of the reflector. By using lenses of various focal lengths the di- 
vergence of the beam can be changed. 

In order to illustrate effectively the performance of the new lamp, comparative 
measurements of the intensity of the spots and floods of the three spotlights 
indicated in Table I were made. 

Note that the intensity of the spot cast by the standard Klieglight is about the 
same as that of the flood, which is to be expected as the lens position is unchanged, 
the size of the beam being regulated by the shutter. It is an interesting feature 
of this type of lamp, that the field intensity remains constant while the beam is 
varied. The unit lends itself readily to lenses having any degree of spread, either 
circular or in only one direction. 



362 



Spotlight 



MOTION PICTURE APPARATUS 

TABLE I 

Comparative Tests of Spot and Flood Intensity 
(51 -Ft. Throw) 



Standard 



Klieglight (Fig. 4) Model F 



Lens 


8"X16" 


6" X 8" (Single Lens) 


Combination of Two 








Lenses 


Reflector 


5 : /4 Rhodium 


Rhodium Elliptical 






Spherical 


(No Front Mirror) 




Control 




Shutter 


Shutter and 








Adjustable Lenses 


Lamp 


2000-w. 


2000-w. 200-hr. 


2000-w. 200-hr. 




Monoplane 


Biplane 115-v. 


Biplane 115-v. 




115-v. 






Spot Intensity 


24 


32 


70 


(6 ft.) 








Floodlntensity 


11 


32 


32 


(20 ft.) 









Referring again to Fig. 4, a unit of such type is very suitable for proscenium 
lighting, balcony-front units, ceiling floods for illuminating stages and orchestra 
pits, for general spotlighting on the stage, and for indoor and outdoor flood- 
lighting anywhere where a sharply cut-off beam of high intensity without spill 
is required. Lenses can be had for beam-spreads varying from 49 to 5 degrees. 

The Model F Klieglight resulted from the further development of the present 
standard, the variation of the intensity and spread of the beam being effected 
by adjustment of the lenses without dimmers. Two lenses are used in com- 
bination, the shutters remaining fixed, by which means the total luminous output 
of the lamp is utilized at all times. Although the intensity of the illuminated 
area decreases as the area increases, the minimum intensity, which occurs in 
the flood position, is about the same as the intensity of the standard Klieglight. 
The maximum, which occurs in the spot position, is more than three times as 
great. The shutters can, of course, be adjusted during the alteration from flood 
to spot or vice versa, so that any intensity within the range of the lamp may be 
achieved. The transition from spot to flood is effected much more gradually 
than is possible with a dimmer. The most important features of the new spotlight 
are the method of controlling the beam, the absence of spill light, and the atten- 
dant reduction in the lighting expense and operating cost. 



THE FALL CONVENTION 

NEW YORK, N. Y., OCT. 29 NOV. 1, 1934 

HOTEL PENNSYLVANIA 

Approximately two hundred members and guests of the Society attended the 
various sessions of the Fall Convention at New York. The Convention opened 
on Monday morning with a general session, including reports of Committees, 
election of officers of the Society for 1935, and action on a proposed amendment 
of By-Law 1, Sec. 3(d), as described in Society Announcements. 

At noon of the opening day, an informal luncheon was held for the members 
and guests. A short introductory address was given by President Goldsmith, 
followed by addresses by Mrs. Frances Taylor Patterson, Director of photoplay 
Appreciation of Columbia University; Mr. Martin Quigley, Publisher of the 
Motion Picture Herald; Col. R. W. Winton, Managing Director of the Amateur 
Cinema League, Inc.; and Mr. Homer G. Tasker, the president-elect for 1935. 

The program of papers and presentations, as actually followed at the sessions, 
was published in the November issue of the JOURNAL. At the Semi-Annual Ban- 
quet, held on Wednesday evening, the members were addressed by Dr. F. B. 
Jewett, President of Bell Telephone Laboratories, Inc., who traced the important 
and parallel connection between the art of telephonic communication and that of 
producing and projecting sound motion pictures. Dr. Jewett was appropriately 
introduced by President Goldsmith. 

In recognition of Dr. Goldsmith's unbroken attendance at the meetings of the 
Projection Practice Committee during the past three years, and his unselfish and 
invaluable contributions to the work of that Committee the members of the 
Committee presented to Dr. Goldsmith, at the banquet, a solid silver combina- 
tion fountain-pen and pencil. The presentation was made on behalf of the Com- 
mittee by Mr. J. J. Finn, and was followed by a few words of appreciation by 
Mr. J. I. Crabtree, on behalf of the Board of Governors, for Dr. Goldsmith's un- 
tiring and very successful administration of the Society's affairs during the past 
two years. 

Credit for the success of the Convention, which might be measured in terms 
of an increased general interest of the motion picture industry in the affairs of the 
Society was largely due to the efforts of Mr. W. C. Kunzmann, Convention Vice- 
President, Mr.- J. I. Crabtree, Editorial Vice-President, Mr. J. O. Baker, Chair- 
man of the Papers Committee, and Mr. H. Griffin, in charge of projection and 
other technical facilities. Others to whom credit is due were Mr. H. Heidegger, 
Mr. Griffin's assistant; the officers and members of Local No. 310, 1. A. T. S. E., 
for furnishing the projectionists for the film programs and technical sessions; 
Mrs. O. M. Glunt, for attanging an attractive and interesting program of enter- 
tainment for the ladies visiting the Convention; Mr. and Mrs. H. Griffin, for 
arranging a tea and fashion show for the ladies at Wanamaker's department store; 

363 



364 HIGHLIGHTS OF THE CONVENTION [j. s. M. P. E. 

Mr. J. Frank, Jr., Chairman of the Apparatus Exhibit Committee; Mr. W. Whit- 
more, Chairman of the Publicity Committee; and Mr. M. W. Palmer for his 
assistance in arranging the banquet facilities. 

The sound and projection equipment used in the meetings and at the banquet 
was supplied and installed by the International Projector Corp. ; Bausch & Lomb 
Optical Co; National Carbon Co.; Bell & Howell Co.; Raven Screen Co.; Elec- 
tro-Acoustic Products Co.; National Theater Supply Co.; RCA Victor Com- 
pany, Inc. ; and Motion Picture Lighting & Equipment Co. 

Courtesy passes were provided to the members and guests by the Radio City 
Music Hall, Warner's Strand Theater, and the Paramount Theater. The floor 
show at the Banquet was provided through the kind offices of Mr. J. H. Spray 
and Mr. H. Rubin. Passes to several broadcasts were provided for the Ladies 
Committees by the National Broadcasting Co. 

Monday and Tuesday evenings were devoted to film programs as follows: 
Timereel, Fox Film Corp.; Old Kentucky Hounds, Paramount Pictures, Inc.; 
Grandfather's Clock, Metro-Goldwyn-Mayer ; Gay Divorcee, RKO Pictures, Inc.; 
Transatlantic Merry-Go- Round, United Artists; St. Louis Kid, Warner Bros. 
Pictures, Inc.; So You Won't Talk and Baby Blues, Vitagraph Corp.; A Dream 
Walking, Paramount. 



HIGHLIGHTS OF THE TECHNICAL SESSIONS 

Among the interesting presentations on Monday was a paper by H. Rosen- 
berger, describing the recent developments in the technic of cinephotomicrography 
or micro motion pictures. This was followed by a symposium of three papers on 
x-ray cinematography; one by R. F. Mitchell, in which the history of cinematog- 
raphy with x-rays was traced; another by R. F. James, dealing with the principles 
of Roentgen cinematography, and another by J. R. Townsend and L. E. Abbott, 
describing the applications of x-ray cinematography in industrial development 
work. 

On Monday evening, preceding the motion picture show, an illustrated lecture 
by Dr. C. E. K. Mees entitled "Certain Photographic Aspects of Sound Record- 
ing" was presented by L. A. Jones. The presentation constituted a valuable 
resume of the large amount of research work carried out by various experimenters 
to date. 

The paper by A. L. Williams on the piezoelectric loud speaker, followed by a 
demonstration of the performance of such a speaker, stimulated much discussion 
and interest. The reproduction of the orchestra, singers, and speakers at the 
banquet on Wednesday evening was through a piezoelectric microphone oper- 
ating according to the same principles. 

C. E. Lane repeated his demonstration of the mechanical analogue of electric 
wave filters, which he had originally presented at the Atlantic City Convention 
last spring, in a more detailed and elaborate form. 

On the afternoon of Tuesday, Dr. Goldsmith discussed at quite some length 
the possibilities of engineering developments in the motion picture industry, in 
which many fertile fields for research and investigation were pointed out. This 



Dec., 1934] HIGHLIGHTS OF THE CONVENTION 365 

paper prompted considerable discussion and suggestions for further study and im- 
provements in motion picture technic. 

Perhaps the outstanding session of the Convention was that devoted to the 
theater and projection, on Tuesday afternoon, which was opened by Dr. Gold- 
smith's presentation. The report of the Projection Practice Committee was 
followed by a vigorous and interesting discussion on the merits of reflector guards 
for projection machines, and the paper by D. B. Joy and E. R. Geib described a 
non-rotating high-intensity arc, which operates more efficiently and provides a 
quality of light comparable with that obtained from the conventional high- 
intensity arc. 

The report by Messrs. Schlanger, Wolf, and Jones, outlining in a very interest- 
ing manner the architectural and acoustical features of motion picture theaters, 
was based on information assembled with the view of subsequently presenting it 
before architectural societies. 

The way in which the lighting of the Centre Theatre, Rockefeller City, New 
York, is controlled by means of electronic tube devices formed the subject of an 
interesting presentation by J. R. Manheimer and T. H. Joseph. 

On Wednesday morning Dr. S. E. Sheppard, in his paper on photographic sen- 
sitivity, outlined the various theories proposed to date explaining the reason for 
the sensitivity of the photographic emulsion to incident light; and some of the 
mysteries of rear projection for process photography were explained by G. G. 
Popovici and H. Griffin, their presentation representing a valuable contribution 
to studio practice. 

In the afternoon of Wednesday inspection trips were conducted to various 
studios, laboratories, and manufactories in the New York district, which were 
well attended and apparently greatly appreciated by the members, judging from 
the large turnout for each trip. 

"What is Light?" constituted an extremely interesting presentation by S. G. 
Hibben, which was accompanied by illuminating demonstrations. The author 
predicted an increasing application of light sources such as the sodium, mercury, 
and zinc vapor lamps. Also on Thursday, J. D. Edwards, of the Aluminum 
Company of America, displayed samples of polished aluminum electrolytically 
treated so as to attain an extremely high reflecting power. 

A new method for controlling humidity, by passing the air to be conditioned 
through a saturated solution of lithium chloride, was described by F. R. Bi- 
chowsky. 

An innovation of the Convention was a symposium on "Construction Mate- 
rials for Motion Picture Processing Apparatus," in which Dr. LaQue of the In- 
ternational Nickel Company described the new alloy, Inconel, and Mr. Foote, 
of the Synthane Corporation, Oaks, Pa., described the various molded bakelite 
products. Dr. Mitchell, of the Carnegie Steel Company, mentioned a stainless 
steel containing molybdenum in addition to chromium and nickel, which should 
display greater resistance to corrosion than the usual 18-8 stainless steel alloys. 

"A Developing Rack for Continuously Moving the Film during Processing 
by the Rack-and-Tank System" was described by C. E. Ives. With this mecha- 
nism it is possible to produce an equally uniform degree of development as is at- 
tainable with the larger processing machines. 



SOCIETY ANNOUNCEMENTS 
BOARD OF GOVERNORS 

At a meeting held at the Hotel Pennsylvania on October 28, the day preceding 
the opening of the Fall Convention, plans were laid for holding the Spring, 1935, 
Convention at Hollywood, Calif., May 20-24, inclusive. The status report 
presented by Mr. O. M. Glunt, Financial Vice-President, indicated that the fiscal 
operations of the Society during the current year were progressing very satis- 
factorily; in view of which the Board voted to increase the number of pages 
published in the JOURNAL, beginning with the January issue. Various designs for 
the Progress medal were submitted by Mr. J. I. Crabtree, and work has been 
begun on a design of the Journal Award Certificate which this year is to be 
conferred, posthumously, upon Dr. Peter A. Snell. 

A Code of Administrative Practices, prepared by a committee of board members 
and presented by Mr. O. M. Glunt, was adopted by the Board. This code 
formulates the current administrative procedure of the Society, as directed by en- 
actments of the Board extracted from the mintues of the meetings, that are now 
in effect. The Code is to be brought up to date periodically, so that each new 
Board, as it is elected, will be aware immediately of what enactments still remain 
in force. 

Among the actions taken by the Board was the abrogation of the charge for 
exhibiting apparatus at conventions of the Society. No charge will therefore 
be levied at the Hollywood Convention, and it is hoped that a large number of 
exhibitors will take advantage of this enactment and assist in making the Holly- 
wood exhibit a notable one. 

In order to clarify a point that has been discussed in the past, the Board ruled 
that all Committees of the Society shall be appointed annually, their terms corre- 
sponding approximately with that of the President of the Society. In other 
words, the term of office of all members of the various Committees of the Society 
will coincide with the calendar year, since, according to the recently revised 
Constitution and By-Laws, the President's term also coincides with the calendar 
year. 

A committee of Board members was appointed to confer with Mr. J. W. 
McNair, of the American Standards Association, regarding the selection of the 
organizations to be represented upon the recently authorized Sectional Com- 
mittee on Standardization. This Committee will prepare and render its specific 
recommendations to the Board at the next meeting which is to be held on Friday, 
December 14. 

ATLANTIC COAST SECTION 

At a meeting held at the studio of RCA Photophone, Inc., New York, N. Y. f on 
November 14, a paper entitled "An Improved System for Noiseless Recording" 
was presented by Mr. G. L. Dimmick of the RCA Victor Company, Inc. The 
paper, which was followed by an interesting demonstration of noiseless recording, 
366 



SOCIETY ANNOUNCEMENTS 367 

enlarged upon the information contained in previous papers upon the subject, 
and the demonstration indicated that means have been found of increasing the 
volume range of reproduction considerably without introducing distortion or 
ground noises. 

AMENDMENT OF BY-LAW I, SEC. 3 (D) 

In accordance with By-Law XI, outlining the method of amending the By-Laws 
of the Society, the following proposed amendment was introduced at the Fall, 
1934, Meeting at New York, N. Y., over the signatures of ten members of 
Active or higher grade: 

"Applicants for Associate membership shall give as reference at least one mem- 
ber of higher grade in good standing. Applicants shall be elected to membership 
by the approval of at least three-fourths of the Board of Governors, or, at the 
discretion of the Board, this authority may be delegated to a Committee on Admissions 
appointed by the Board." 

The amendment consists in adding to the end of the second sentence the 
clause printed in italics. 

JOURNAL AWARD 

An award of fifty dollars, to be accompanied by an appropriate certificate, was 
provided for by the Board of Governors some time ago, to be granted to the author 
or authors of the most outstanding paper originally published in the JOURNAL of 
the Society during the preceding calendar year (1933). The Journal Award 
Committee, appointed to study the contributions to the JOURNAL and make their 
recommendations for the Award to the Board, reported as follows: 

AWARD 

P. A. Snell, "An Introduction to the Experimental Study of Visual Fatigue;" 

May, p. 367. 

HONORABLE MENTION 

H. E. Ives, "An Experimental Apparatus for the Projection of Motion Pictures 
in Relief;" Aug., p. 106. 

J. Crabtree, "Sound Film Printing;" Oct., p. 294. 

W. Garity, "Production of Animated Cartoons;" April, p. 309. 

W. N. Goodwin, "A Photronic Photographic Exposure Meter;" Feb., p. 95. 

O. Sandvik, V. C. Hall, and J. G. Streiffert, "Wave Form Analysis of Variable 
Width Sound Records;" Oct., p. 323. 

In view of the untimely death of Dr. Snell some months ago, the Award will be 
granted posthumously to his widow. Announcement of the Award was made at 
the Semi- Annual Banquet of the Society on October 31. 

PROJECTION SCREENS COMMITTEE 

At a meeting held on October 9 plans were suggested for forming a Com- 
mittee representative of the various phases of screen illumination, in order to 
initiate a comprehensive study of that subject. Such a Committee would 
include representatives of the Projection Practice, Screens, and Theory Com- 
mittees, Committee on Laboratory Practice, and Sound Committee, so that the 
problem could be studied from the standpoints of screen design, projection, film 
density, and sound reproduction. 



AUTHOR INDEX, VOLUME XXIII 



JULY TO DECEMBER, 1934 



Author 
ARNOLD, P. 



BATSEL, C. N. 

(and SACHTLEBEN, L. T.) 
BATSEL, C. N. 

(and SACHTLEBEN, L. T., 
and DIMMICK, G. L.) 
BATSEL, C. N. 
BATSEL, C. N. 

(and DIMMICK, G. L., 
and SACHTLEBEN, L. T.) 
BELAR, H. 

(and DIMMICK, G. L.) 
CARSON, W. H. 
CONROW, L. W. 

(and WILCOX, H. M.) 
CRABTREE, J. 



DIMMICK, G. L. 

(and BELAR, H.) 
DIMMICK, G. L. 

(and BATSEL, C. N., 
and SACHTLEBEN, L. T.) 
DIMMICK, G. L. 

(and BATSEL, C. N., 
and SACHTLEBEN, L. T.) 
EDGERTON, H. E. 



A Motion Picture Negative of Wider 

Usefulness 
Sixteen-Millimeter Sound Pictures in 

Color 
A 16-Mm. Sound Recording Camera 



A Non-Slip Sound Printer 
Optical Reduction Sound Printing 



Issue Page 
Sept. 160 

Aug. 82 
Aug. 87 



Aug. 100 
Aug. 108 



An Improved System for Noiseless Re- 
cording 

The English Dufaycolor Film Process 

Some Technical Aspects of Theater 
Operation 

A Sweep Oscillator Method of Record- 
ing Wide Frequency-Band Response 
Spectra on Short Lengths of Motion 
Picture Film 

An Improved System for Noiseless Re- 
cording 

A 16-Mm. Sound Recording Camera 



Optical Reduction Sound Printing 



Stroboscopic-Light High-Speed Motion 



(and GERMESHAUSEN, K. J.) Pictures 



Foster, L. V. 

(and HERRIOTT, W.) 
GEIB, E. R. 

(and JOY, D. B.) 

GEIB, E. R. 

(and JOY, D. B.) 

GERMESHAUSEN, K. J. 

(and EDGERTON, H. E.) 
368 



Recent Optical Improvements in Sound- 
Film Recording Equipment 

Operating Characteristics of the High- 
Intensity A-C. Arc for Motion Pic- 
ture Projection 

The Relation of the High-Intensity 
A-C. Arc to the Light on the Pro- 
jection Screen 

Stroboscopic-Light High-Speed Motion 
Pictures 



July 48 
July 14 

Dec. 338 



Nov. 299 

July 48 
Aug. 87 



Aug. 108 

Nov. 284 
Sept. 167 

July 27 

July 35 
Nov. 284 



INDEX 



369 



Author 

GOEHNER, W. R. 

GOLDSMITH, A. N. 

HERRIOTT, W. 

(and FOSTER, L. V.) 
IVES, F. E. 
JONES, L. A. 

(and WEBB, J. H.) 
JOY, D. B. 

(and GEIB, E. R.) 

JOY, D. B. 

(and GEIB, E. R.) 

KLIEGL, H. 
KOSSMAN, H. R. 
LACK, F. R. 
MALLINA, R. F. 
MASSA, F. 

(and OLSON, H. F.) 

MILI, G. 
OLSON, H. F. 
(and MASSA, F.) 

PORTER, L. C. 
RAYTON, W. B. 

SACHTLEBEN, L. T. 

(and BATSEL, C. N.) 
SACHTLEBEN, L. T. 

(and BATSEL, C. N., 
and DIMMICK, G. L.) 
SACHTLEBEN, L. T. 

(and DIMMICK, G. L., 
and BATSEL, C. N.) 
WEBB, J. H. 

(and JONES, L. A.) 
WILLIAMS, A. L. 
WILCOX, H. M. 

(and CONROW, L. W.) 
WOLCOTT, E. A. 



VICTOR, A. F. 



Issue Page 

The Microdensitometer as a Labora- 
tory Measuring Tool Dec. 318 
Problems in Motion Picture Engineer- 
ing Dec. 350 
Recent Optical Improvements in Sound- 
Film Recording Equipment Sept. 167 
Pioneering Inventions by an Amateur Sept. 175 
Reciprocity Law Failure in Photo- 
graphic Exposures Sept. 142 
Operating Characteristics of the High- 
Intensity A-C. Arc for Motion Pic- 
ture Projection July 27 
The Relation of the High-Intensity 
A-C. Arc to the Light on the Pro- 
jection Screen July 35 
The New Klieglight Dec. 359 
A Small Developing Machine Dec. 356 
Piezoelectric Frequency Control Oct. 187 
A Rotating Mirror Oscilloscope Dec. 328 
On the Realistic Reproduction of Sound 
with Particular Reference to Sound 
Motion Pictures Aug. 63 
The Biplane Filament in Spotlighting Sept. 131 
On the Realistic Reproduction of Sound 
with Particular Reference to Sound 
Motion Pictures Aug. 63 
C.Francis Jenkins: An Appreciation Sept. 126 
The Effect of Aperture Lenses on 

Illumination Dec. 309 

Sixteen-Millimeter Sound Pictures in 

Color Aug. 82 

A 16-Mm. Sound Recording Camera Aug. 87 



Optical Reduction Sound Printing Aug. 108 



Reciprocity Law Failure in Photo- 
graphic Exposures Sept. 142 

Piezoelectric Microphones Oct. 196 

Technical Aspects of Theater Opera- 
tion Dec. 338 

Recent Improvements in Equipment 
and Technic in the Production of 
Motion Pictures Oct. 210 

Continuous Optical Reduction Print- 
ing Aug. 96 



CLASSIFIED INDEX, VOLUME XXIII 

JULY TO DECEMBER, 1934 

American Standards Association 

S. M. P. E. Sponsorship of Sectional Committee on Standardization, No. 1 

(July), p. 59; No. 3 (Sept.), p. 182; No. 4 (Oct.), p. 243. 
Arcs 

Operating Characteristics of the High-Intensity A.-C. Arc for Motion Picture 

Projection, D. B. Joy and E. R. Geib, No. 1 (July), p. 27. 
The Relation of the High-Intensity A-C. Arc to the Light on the Projection 

Screen, D. B. Joy and E. R. Geib, No. 1 (July), p. 35. 
Apparatus 

Recent Improvements in Equipment and Technic in the Production of Motion 

Pictures, E. A. Wolcott, No. 4 (Oct.), p. 210. 

A Sweep Oscillator Method of Recording Wide Frequency-Band Response 
Spectra on Short Lengths of Motion Picture Film, J. Crabtree, No. 5 (Nov.), 
p. 299. 
The Microdensitometer as a Laboratory Measuring Tool, W. R. Goehner, 

No. 6 (Dec.), p. 318. 

A Rotating Mirror Oscilloscope, R. F. Mallina, No. 6 (Dec.), p. 328. 
A Small Developing Machine, H. R. Kossman, No. 6 (Dec.), p. 356. 
The New Klieglight, H. Kliegl, No. 6 (Dec.), p. 359. 
Cameras 
A 16-Mm. Sound Recording Camera, C. N. Batsel, L. T. Sachtleben, and G. L. 

Dimmick, No. 2 (Aug.), p. 87. 
Color Cinematography 

The English Dufaycolor Film Process, W. H. Carson, No. 1 (July), p. 14. 
Sixteen-Millimeter Sound Pictures in Color, C. N. Batsel and L. T. Sachtleben, 

No. 2 (Aug.), p. 82. 
Committee Reports 

Report of the Committee on Standards and Nomenclature, No. 1 (July), p. 3. 
Report of the Sound Committee, No. 1 (July), p. 6. 
Report of the Non-Theatrical Equipment Committee, No. 1 (July), p. 9. 
Committees 

Committees of the Society of Motion Picture Engineers, No. 1 (July), p. 55. 
Development 

A Small Developing Machine, H. R. Kossman, No. 6 (Dec.), p. 356. 
Dufaycolor 

The English Dufaycolor Film Process, W. H. Carson, No. 1 (July), p. 14. 
Exposure in Photography 

Reciprocity Law Failure in Photographic Exposures, L. A. Jones and J. H. 
Webb, No. 3 (Sept.), p. 142. 

370 



INDEX 371 

Film, Photographic Characteristics 

Reciprocity Law Failure in Photographic Exposures, L. A. Jones and J. H. 

Webb, No. 3 (Sept.), P- 142. 

A Motion Picture Negative of Wider Usefulness, P. Arnold, No. 3 (Sept.), 
p. 160. 

Frequency Control 

Piezoelectric Frequency Control, F. R. Lack, No. 4 (Oct.), p. 187. 
General 

Pioneering Inventions by an Amateur, F. E. Ives, No. 3 (Sept.), p. 175. 

Problems in Motion Picture Engineering, A. N. Goldsmith, No. 6 (Dec.), 
p. 350. 

High-Speed Cinematography 

Stroboscopic-Light High-Speed Motion Pictures, H. E. Edgerton and K. J. 
Germeshausen, No. 5 (Nov.), p. 284. 

Historical 

Pioneering Inventions by an Amateur, F. E. Ives, No. 3 (Sept.), p. 175. 
Illumination 

Operating Characteristics of the High-Intensity A-C. Arc for Motion Picture 
Projection, D. B. Joy and E. R. Geib, No. 1 (July), p. 27. 

The Relation of the High-Intensity A-C. Arc to the Light on the Projection 
Screen, D. B. Joy and E. R. Geib, No. 1 (July), p. 35. 

The Biplane Filament in Spotlighting, G. Mili, No. 3 (Sept.), p. 131. 

The Effect of Aperture Lenses on Illumination, W. B. Rayton, No. 6 (Dec.), 
p. 309. 

The New Klieglight, H. Kliegl, No. 6 (Dec.), p. 359. 

Incandescent Lamps 

The Biplane Filament in Spotlighting, G. Mili, No. 3 (Sept.), p. 131. 
Index 

Author Index, Vol. XXIII, July to December, 1934, No. 6 (Dec.), p. 368. 

Classified Index, Vol. XXIII, July to December, 1934, No. 6 (Dec.), p. 370. 

Jenkins, C. Francis 

C. Francis Jenkins: An Appreciation, L. C. Porter, No. 3 (Sept.), p. 126. 
Lenses 

The Effect of Aperture Lenses on Illumination, W. B. Rayton, No. 6 (Dec.), 
p. 309. 

Membership of the Society 

List of Members, No. 4 (Oct.), p. 215. 
Microdensitometer 

The Microdensitometer as a Laboratory Measuring Tool, W. R. Goehner, 
No. 6 (Dec.), p. 318. 



372 INDEX [j. s. M. P. E. 

Microphones 

Piezoelectric Microphones, A. L. Williams, No. 4 (Oct.), P- 196. 

Noiseless Recording 

An Improved System for Noiseless Recording, G. L. Dimmick and H. Belar, 
No. 1 (July), p. 48. 

Non-Theatrical Equipment 

Report of the Non-Theatrical Equipment Committee, No. 1 (July), p. 9. 
A 16-Mm. Sound Recording Camera, C. N. Batsel, L. T. Sachtleben, and G. L. 
Dimmick, No. 2 (Aug.), p. 87. 

Obituary 

C. Francis Jenkins, No. 1 (July), p. 59; see also No. 3 (Sept.), p. 126. 
J. Elliott Jenkins, No. 1 (July), p. 59. 
W. V. D. Kelley, No. 5 (Nov.), p. 305. 
George K. Jenson, No. 5 (Nov.), p. 305. 

Officers of the Society 

No. 2 (Aug.), p. 118; see also reverse of contents page, each issue of the JOUR- 
NAL. 

Optical Reduction 

Continuous Optical Reduction Printing, A. F. Victor, No. 2 (Aug.), p. 96. 
Optical Reduction Sound Printing, G. L. Dimmick, C. N. Batsel, and L. T. 
Sachtleben, No. 2 (Aug.), p. 108. 

Optics 

Recent Optical Improvements in Sound-Film Recording Equipment, W. Her- 
riott and L. V. Foster, No. 3 (Sept.), p. 167. 

Oscilloscope 

A Rotating Mirror Oscilloscope, R. F. Mallina, No. 6 (Dec.), p. 328. 

Photography 

Reciprocity Law Failure in Photographic Exposures, L. A. Jones and J. H. 
Webb, No. 3 (Sept.), p. 142. 

Piezoelectric Equipment 

Piezoelectric Frequency Control, F. R. Lack, No. 4 (Oct.), p. 187. 
Piezoelectric Microphones, A. L. Williams, No. 4 (Oct.), p. 196. 

Printing 

Continuous Optical Reduction Printing, A. F. Victor, No. 2 (Aug.), p. 96. 
A Non-Slip Sound Printer, C. N. Batsel, No. 2 (Aug.), p. 100. 
Optical Reduction Sound Printing, G. L. Dimmick, C. N. Batsel, and L. T. 
Sachtleben, No. 2 (Aug.), p. 108. 

Production 

Recent Improvements in Equipment and Technic in the Production of Motion 
Pictures, E. A. Wolcott, No. 4 (Oct.), p. 210. 



Dec., 1934] INDEX 373 

Projection, General Information 

Operating Characteristics of the High-Intensity A-C. Arc for Motion Picture 

Projection, D. B. Joy and E. R. Geib, No. 1 (July), p. 27. 
The Relation of the High-Intensity A-C. Arc to the Light on the Projection 

Screen, D. B. Joy and E. R. Geib, No. 1 (July), p. 35. 
The Effect of Aperture Lenses on Illumination, W. B. Rayton, No. 6 (Dec.), 

p. 309. 

Reciprocity Law 

Reciprocity Law Failure in Photographic Exposures, L. A. Jones and J. H. 
Webb, No. 3 (Sept.), p. 142. 

Screen Illumination 

The Relation of the High-Intensity A-C. Arc to the Light on the Projection 
Screen, D. B. Joy and E. R. Geib, No. 1 (July), p. 35. 

Sixteen-Millimeter Equipment 

Report of the Non-Theatrical Equipment Committee, No. 1 (July), p. 9. 
Sixteen-Millimeter Sound Pictures in Color, C. N. Batsel and L. T. Sachtleben, 

No. 2 (Aug.), p. 82. 
A 16-Mm. Sound Recording Camera, C. N. Batsel, L. T. Sachtleben, and G. L 

Dimmick, No. 2 (Aug.), p. 87. 

Sound 

Report of the Sound Committee, No. 1 (July), p. 6. 

Sound Printing 

See Printing 

Sound Recording 

Report of the Sound Committee, No. 1 (July), p. 6. 

An Improved System for Noiseless Recording, G. L. Dimmick and H. Belar, 

No. 1 (July), p. 48. 
A 16-Mm. Sound Recording Camera, C. N. Batsel, L. T. Sachtleben, and G. L. 

Dimmick, No. 2 (Aug.), p. 87. 
Recent Optical Improvements in Sound-Film Recording Equipment, W. Her- 

riott and L. V. Foster, No. 3 (Sept.), p. 167. 
A Sweep Oscillator Method of Recording Wide Frequency-Band Response 

Spectra on Short Lengths of Motion Picture Film, J. Crabtree, No. 5 (Nov.), 

p. 299. 

Sound Reproduction 

Report of the Sound Committee, No. 1 (July), p. 6. 

On the Realistic Reproduction of Sound with Particular Reference to Sound 
Motion Pictures, H. F. Olson and F. Massa, No. 2 (Aug.), p. 63. 

Spotlighting 

The Biplane Filament in Spotlighting, G. Mili, No. 3 (Sept.), p. 131. 



374 INDEX 

Standards 

Report of the Committee on Standards and Nomenclature, No. 1 (July), p. 3. 
Standards Adopted by the Society of Motion Picture Engineers, No. 5 (Nov.), 

p. 247. 
See also American Standards Association. 

Standard Test Reels 

Report of the Sound Committee, No. 1 (July), p. 6. 

Stroboscopic Cinematography 

Stroboscopic-Light High-Speed Motion Pictures, H. E. Edgerton and K. J. 
Germeshausen, No. 5 (Nov.), p. 284. 

Studio Equipment 

Recent Improvements in Equipment and Technic in the Production of Motion 
Pictures, E. A. Wolcott, No. 4 (Oct.), p. 210. 

Technical Cinematography 

Stroboscopic-Light High-Speed Motion Pictures, H. E. Edgerton and K. J. 
Germeshausen, No. 5 (Nov.), p. 284. 

Test Reels 

Report of the Sound Committee, No. 1 (July), p. 6 

Theater Operation 

Technical Aspects of Theater Operation, H. M. Wilcox and L. W. Conrow, 
No. 6 (Dec.), p. 338. 




BOD