Survey of motion picture processing with emphasis on sound tracks for color film

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Survey of motion picture processing with emphasis on sound tracks for color film

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A Thesi3 Presented to the Faculty of the Department of Cinema The University of Southern California

In Partial Fulfillment of the Requirements for the Degree Master of Arts

by Victor Bloecker, Jr. January 1950

UMI Number: EP42685

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion.

Dissertation Publishing

UMI EP42685 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code

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Th is thesis, w ritten by

....... J±cAox3JLo.e.cJk:ej;.*Jr....... under the guidance of h.xs... F a c u lty C o m m ittee, and app ro ved by a ll its members, has been presented to and accepted by the C o u n cil on G ra d u ate S tudy and Research in p a r t ia l f u l f i l l ­ ment of the requirements f o r the degree of

....... Mas.t.ex.„.Q£...Acis..................

DateZlJ3m$r.X.12'?.Q.. Faculty Committee




( -'


A sincere appreciation is extended to each of the following gentlemen for giving their valuable time as well as information that has been incorporated in this paper: Edward W. Hart, Cinecolor Corporation V. P. Morin, Technicolor Motion Picture Corporation G. 6. Schomaker, Eastman Kodak Company Sidney Solow, Consolidated Film Industries R. E. Withrow, Ansco Processing Laboratory



....................1 . . . . . . . . . .


The importance of the s t u d y ....................1 Definitions of terms used .....................


Processing....................................... 2 Composite print ...................

. . . . .


Sound t r a c k .....................................2 G a m m a ........................................... 2 Single operation contact printer............... 2 "Track" printer ..............................


Timing........................................... 3 Method of procedure and review of the literature..........


Organization of thesis............................ 3 II.



...........* ............................5

Processing......................................... 5 Interpretation and evaluation of character­ istic curves.....................................7





Types of printers..........


Single and double operation continuous contact printer.


. . . . .


"Track” printer.............. Optical printer.

11 . . . . .


System of p r i n t i n g ....................... Method of timing. Manner of printing IV.







P R O C E S S I N G ............

24 ..........

Methods of procedure


The Ansco dye track..........................


The Eastman silver, sulphide, track...........


The Technicolor silver track ...............


The Cinecolor iron t r a c k ...................


Types of processing m a c h i n e s .................


Sensitome.trlc control, of sound track development.


Variable-area sound t r a c k . .............. . Variable-density sound t r a c k ...............


49 49 51

Fixation and h a r d e n i n g ...................


Wash w a t e r ....................................


Purified water supply. . Time of washing.







PAGE Temper a ture control......................... Drying conditions Air circulation.

. .......................... .


56 57

Temperature and humidity c o n t r o l ...........


Lubrication of f i l m . ..........................





V i s u a l l y .......................... ‘...........


Negative .





P r i n t s ................... . .................


A u d i b l y .. ........ ...........................


Cross-modulation test.......................


Inter-modulation test.......................


SUMMARY AND CQNCLUSIQNS.......................





Therefore, the purpose of this

thesis give a better_understanding of the problems of the motion picture laboratory in so far as they pertain to the processing of sound track on color cilm. THE PROBLEM Statement of the problem.

This paper has been writ­

ten because of the lack of concise, easily read and under­ standable information on the processing of sound track on color film..

It was felt that a survey should be made of

the various laboratories In Hollywood (1) to determine what methods of processing sound track on color film are avail­ able to the producer of motion pictures.

It is also hoped

that the collection and centralization of this information (2) will give the layman, an insight into the workings of a motion picture laboratory. The importance of the study.

The importance is

readily understood when one considers the added popularity

2 of any picture produced in color.

Box office figures indi­

cate that the paying public prefers pictures shot in color; therefore, it is of the utmost importance that the producer know, or at least be familiar with, the methods commonly in use for processing the sound track which must accompany his picture. DEFINITIONS OF TERMS USED Processing.

A method carried out in the laboratory

by which the sound track film is manipulated to produce the recorded sound. Composite print.

That piece of film which contains

both the picture and the sound track. Sound track.

That part of the composite print which

produces the accompanying dialogue, narration, or sound effects for the picture. Gamma.

The relationship between the density range of

the film and the brightness range of the original subject. Single Operation Contact Printer.

A printer in which

the sound track negative and ..the. picture negative are printed simultaneously, in contrast to the Double Operation Contact Printer which prints the sound track and the picture in separate operations.

3 ”Track” Printer,

A printer whose only use Is to

print sound track. Timing.

A method for determining the step at which

the light change system of the printer should be set to produce a balanced print. MTEHQsD OP PROCEDURE AND REVIEW OP THE LITERATURE There are approximately forty different companies throughout the United States processing sound track on color film; however, it was discovered that the resultant sound tracks could be broken, down into four distinct types. These are the iron, silver, silver sulphide, and dye tracks. Contacts were made and interviews arranged with the represen­ tatives of the laboratories processing the four distinct types of sound tracks,.

Patents assigned to these companies

were studied, and various technical manuals, journals, books and magazines investigated.

Of special value to the writer

were the monthly issues of the Journal of the Society of Motion Picture Engineers.

The reader should understand that

none of the Information presented in this, .paper Is of an original nature; it has been collected from the various sources previously described. ORGANIZATION OP THESIS This paper ha3 been organized In such a manner that

the reader can follow the recorded sound track completely through the processing steps to the resultant finished product, that is, the sound track on color film.

This pro­

cedure includes, as described in chapter two, the testing of the emulsions on the duplicating stock while chapter three is devoted to the printing of the negative track on the duplitized raw stock..

The processing of the film, and

finally the methods used to inspect the finished print are investigated in chapters four and five respectively. It will be noted that a great many of the laboratory practices and procedures described are identical to the methods used in the processing of black and white sound track.

A review of these principles will not be detri­

mental to the reader. It might be asked what prevents anyone from duplicat­ ing these processes when the chemical procedures are known. It must be remembered that there, are many things, important to such processes, which are not indicated by mere chemical equations.. For instance, very delicate controls are neces­ sary to have organic.chemical, reactions proceed in the de­ sired direction.

Also, the selection of dyes and their con­

centrations, to yield, proper color balances, require years of trial-and-error experimentation.

It is these among other

factors which cannot be revealed in such a survey of labora­ tory practice and procedure.

CHAPTER II STANDARDS FOR COMPARING EMULSIONS EXPOSURE Most laboratories use the Eastman type IIB sensitometer and various types of step tablet sensitometera as a standard of exposure for comparing emulsions and for running control tests.

Practically: speaking, tests are

made by printing a specially selected sound negative on a carefully maintained continuous printer and visually com­ paring the prints obtained.

When this method of emulsion

comparison is used it is especially necessary to give special attention to the master printer used for printing the negative selected as a standard of reference for sound quality.

The most important parts of. the printer that are

continuously checked include the lamp and the operating speed of the machine.

It is very important to make certain

that the amount of current that is supplied to the lamp be kept constant.

This will insure uniformity of illumination

at the printing aperture. PROCESSING When a new emulsion number of sound raw stock is re­ ceived it is accepted practice to impress upon 10 to 25 foot

lengths taken from one to five rolls selected at random of the new and the former coatings, two to five sensitometric strips on the sensltometer using the positive or negative setup, according to the film being used,

Obviously, the

positive setup is used for those photosensitive materials that have positive film characteristics, and the negative setup for those that have negative type characteristics. Six to one hundred foot lengths of both the new and the form­ er emulsions are printed on the selected printer from the selected negative accepted as a standard of reference.


prints on al.1. strips are made at the step setting that was correct for. the. former coating.

All.sensitometric strip ex­

posures and prints are then developed together by the ap­ propriate development process, either negative or positive, for the time.that produced the desired gamma, density, and photographic quality, that was adjudged satisfactory on the former coating.

Then the step densities on the sensitome-

tered strip are read on a suitable densitometer.

Prom the

plotted, averaged, sensitometric strips the difference in gamma and density speed can be ascertained for the predeter­ mined development time, and by visual judgment the timer can discern.the change of printer light, if any, necessary to produce the. same density in the new was obtained in. the former emulsion.

Often a retest is. made at the new

printer light assignment,.and the. new emulsion is developed

for the time necessary to produce in it a gamma equivalent to the gamma of the former emulsion which is the gamma that the laboratory has determined to be the most suitable to obtain the best quality. INTERPRETATION AND EVALUATION OF CHARACTERISTIC CURVES After the above tests have been performed on the new batch of color duplicating raw stock, an additional check is often made.

Prints are made from a negative sound track

on a thousand foot roll of the old emulsion.

From this

final test a visual inspection of the print determines what printer point rating and development time are assigned to the new emulsion so that prints made with the new emulsion wili match approximately..the quality obtained from the old emulsion.

Often laboratories will depend upon their sensi­

tometric. tests, and assign printer light.settings for posi­ tive emulsions, by drawing, perpendiculars from the point of unit density on the straight line portion of the plotted characteristic curves to the abscissa, or log E, axis, to determine, the., log E difference between the new and old emulsions.. A difference in Log E of 0.05 at equal gammas is equal to a change of about one Bell, and Howell printer light. Generally speaking, positive emulsions from coating to coating are usually within the tolerance of laboratory

manipulation for density and gamma, and, therefore, only slight changes in...printer light settings are necessary. When the new emulsion has a slightly higher or lower gamma than the old emulsion, it is assigned a development time that will produce the gamma desired by the particular labora­ tory.

Most laboratories process variable area and variable

density positives to a control gamma of 2.50.

It is desir­

able, naturally, to maintain the control within plus or minus 0.05 but usually the laboratories have a control gamma variation of plus or minus 0.1.

The printer point variation

is generally held within plus or minus 0.5 printer point; however, some laboratories are willing to accept a print that has a day to day variation of plus or minus one Bell and Howell printer point, or the equivalent of plus or minus 0.05 in log E exposure value at a density of unity.

CHAPTER III PRINTING TYPES OP PRINTERS Regardless of the amount, of Its footage production, each laboratory has several types of printers available for routine or special printing work.

When sound was intro­

duced into the motion picture industry it was decided by most laboratories that a few mechanical changes in their standard printing equipment would expedite and make less expensive the printing of sound track.

This accounts to

some extent for the different types of printers in use today. Single and double,operation continuous contact printer. A very common printer found in most laboratories is the Bell and Howell printer.

The first model was a double operation

type printer, in which, the sound track and the picture were printed in separate operations.

However, it was not long

before laboratories found it more efficient and economical to use singLe-operation printers, that is, printers in which the sound track negative and the picture negative are printed simultaneously.

The modified Bell and Howell

printers and the Duplex step printers are of this type. In laboratories employing Bell and Howell continuous

10 printers that have been modified to print the sound track and the picture negative together, a finished sound print is the result of passing the picture negative, the sound negative, and the positive raw stock continuously through the printer.

Printer mechanisms and light change apparatus

are so constructed that the printers are able to print both forward and backward, thus avoiding the necessity of re­ winding the negative after each printing. Some of. the Bell and Howell printers make use of the standard Bell and Howell picture shutter light change mech­ anism, ufoile others utilize especially designed resistance boards for light, changes.

Ho matter which system is uti­

lized,, the laboratory endeavors to maintain the log exposure increments, step for step upon all machines, equivalent in terms of step density, value when all printer tests are ex­ posed upon, the.same piece of film and developed together. When using these printers it is quite necessary to continually obtain the same quality of work.

In order to

attain this end all printer sound heads are usually matched daily by making a print from unmodulated sound track upon the positive, emulsion being used, at a selected step on each printer, and developing the several prints together in a suitable developing system for the time, previously deter­ mined, that produces the correct gamma and print density in a given.printer.

The step at which the prints are made

11 u p o n each printer is usually two or three points above the mid-step.

If these points, match visually as to density,

the printers are then assumed to be matched, step for step, one against the other.

If a printer is out of match there

are two ways of making the necessary adjustments required to match up the printers.

Either the fixed aperture open­

ing is increased or decreased until the printer matches the other printers at that step; or the distance of the lamp from the printers aperture may. be increased or de­ creased until the match is attained.

It is not uncommon

to find laboratories making densitometrie comparisons of the exposed prints in addition to the visual comparisons. Some laboratories visually, or both visually and densitometrlcally, compare such strips exposed at every step of each printer every two weeks or every month. "Track" Printer.

In those laboratories which use

the printer only for printing sound track Model J, Bell and Howell. Continuous film .printer is generally used.


Is referred to as a "track" printer because Its only use is to print sound track.

Laboratories using "track" print­

ers are those whose process Involves the wash-off-relief method of transferring dyes.

This method does not require

the use of a mechanical.printer such as Bell and Howell manufacturers to print pictures.

Inasmuch as the Bell and

12 Howell continuous, film printer is standard equipment in most laboratories a description of this piece of equipment follows; The 16mm Semi-Automatic Continuous Film Printer, Model J, is designed to print a l l s o u n d or silent 16mm motion picture film. Five methods of printing are possible: (1)

To print on one positive film the picture

area and sound track from two separate negatives.


method necessitates two separate operations, in which the positive film, is run through the printer twice. (2)

To print

the picture area and soundtrack


two operations, even though both the picture areaand sound track are on the same negative film. (3)

Or, as it rarely ever occurs, to print both

the picture area and sound track simultaneously if the two records are on.the same negative film. (4)

To print

the picture area only.


To print

the sound track only.

The printer1s film moving, mechanism is designed to unwind the positive and negative films.from the feed hubs, and move them past the printing, aperture without longi­ tudinal or horizontal slippage, on to their respective takeup hubs.

All. this action is a continuous uniform motion

which will cause no undue strain on the perforations.

15 A 150-watt lamp furnishes the illumination for ex­ posures .


light intensity is mechanically controlled

in order to insure instantaneous light, changes that can he duplicated exactly on all prints. A combination interlocking switch and starting lever is hand .operated.

The lever switch performs three distinct

operations w h e n the lever is moved one-quarter turn to the "operating” position:

(1) the component parts for each

operation are assembled to the lever shaft in such a manner and position that the printing light is turned on;


electric current. Is.transmitted to the circuit interrupter; (3.) the belt tension pulley engages the drive belt at the proper time. When the s tarting le ver is shifted from the "operat­ ing” position to. the "off" position, the belt tension pulley shifts and releases the tension on the. drive belt, a stop engages the. brake arm,_ causing the mechanism to stop instant­ ly, and the current to the printing lamp and magnet is cut off.

The lever is interlocked with the printing gate so

the gate can not be opened until .the lever is switched to the off position. The film moving mechanism includes a feed sprocket, a printing sprocket, and a take-up sprocket.

All the

sprockets are positively geared together and so driven as to move the film at a uniform linear speed of 60 feet per

minute. The film is accurately registered just before it reaches the printing aperture, and remains so until print­ ing is accomplished.

The film, loops between the printing

and the take-up sprocket thus absorbing any uneven motion of the film.

An adjustable clutch take-up insures smooth

winding of the film, onto the take-up flanges, making trans mission, of uneven film motion to.the printing aperture impossible. The positive and negative films are held in close contact at the printing sprocket by means of a film gate. The gate is pivoted in the center to permit.the passage of splices, and is mounted on a hinge, lever to permit ease in opening for the purpose of threading films on the printing sprocket. The film.gate has a gate shoe shaped to fit the printing sprocket, and is highly polished to eliminate the possibility of scratching, abrading, or otherwise injuring the films... The. film, gate is interlocked with the combina­ tion switch lever, which prevents an accidental opening while the mechanism is in operation, and the printing light turned on.

To open the film..gate it .is necessary to stop

the printing mechanism,., which automatically turns out the printing ..light, A film footage counter is connected to the feed

15 sproeket shaft, automatically registering every foot of film that passes through the mechanism.

It is of great value in

checking the progress of the printing operation, as the footage registered is made to check with the footage indi­ cated for each scene on the printing index card. An automatic curved light shutter encloses the lamp side of the printing sprocket.

The shutter has 22 exposure

openings which vary from.adjacent openings by approximately 10$.

This range of exposures is sufficient to permit print­

ing of all.normal negatives.

Control of exposure is ob­

tained. by varying.the volume of light, allowed to r each the film rather than the varying of brilliancy of the light by means of a resistance in the light circuit.

In other words,

light control is by means of. a variable shutter instead of an electrical control on the light intensity. All normal, adjustments of. the light volume are taken care of by the shutter, set by means of the manually operated index, pointer.. o



the. index, dial,, which is marked with the

22 shutter opening positions..

The. actual change in the

size.of. shutter opening is actuated by an electrical circuit interrupter which rides against the edge of the negative. Thus the setting of. the shutter is. always one step ahead of the actual, operation, instantaneous change in the light volume is made as soon as the scene changes. The printing aperture jaw is operated by the aperture

16 jaw setting knob which permits the locating of three indi­ vidual aperture openings in printing position*

The purpose

of each opening is as follows: (1)

When the knob is set so the pointer is at

"Sound Only," the width of the printing aperture permits the printing of only the sound track. (2)

When the.knob is set so that the pointer is

set at "Picture Only," the width of the printing aperture permits the printing of only the picture area.

This open­

ing is used for printing the picture area from either sound or silent negatives. (5)

When the. knob is set so the pointer is at

"Sound Picture," the width of the opening permits the print­ ing of the sound track and picture area simultaneously.


is obvious that the simultaneous printing of picture and sound track can be done only from master 16mm. sound negatives in which the density of the sound and picture area have been matched to permit their being run through the printer at one light setting. Optical Printer.... As far back as 1933 accounts were published which told of the defects introduced when sound track is contact printed*

It was shown that individual

prints exhibit large fluctuations in high frequency output, *

indicating variations, in the contact between the negative and the positive raw stock as they pass in front of the

17 printing aperture.

It was also shown that there is an over-

all_loss of level, of the higher frequencies which varies In a regular manner with the pitch of the perforations of the negative and the positive film stock,, and which is due to the slippage that must occur between the two films as they are carried along by the. teeth of the sprocket. The printing of 16mm sound tracks offer more oppor­ tunity for the disadvantages of contact be noticed than does the printing of 35mm.tracks.

With 16mm

tracks the sprocket holes, are farther apart, and therefore the amount of slippage which, must, take place when each sprocket tooth engages or disengages is greater.

The high

frequency pattern recorded on the negative Is two and a half times finer, which makes the blurring effect of a given amount, of printer slippage correspondingly more serious. Also the distance between sprocket holes is greater than the height which, it is practical to make the printing aper­ ture.

This, means, that some parts of the sound track are

and other parts are not in front of the printing aperture at times when slippage occurs, both.24 cycle flutter and 24 cycle amplitude modulation of the high frequencies of the record are introduced. Since these printing defects are due to non-uniform relative motion of the negative and the positive raw stock, J. A. Maurer came to the conclusion that the. best solution

18 for possible improvement was a one-to-one ratio optical sound printer.

In an optical printer the negative and the

positive raw stock can be moved separately at constant speeda,. and if the image is transferred by a good enough optical, system, the resulting prints can be free of the three defects common to contact printing, of sound track, flutter, amplitude variation of high frequencies, and over­ all. loss of high frequencies. For sometime the construction of the correct optical system was' held up because it was found that the designed lens combination, did. not. give, definition on color film sufficiently good for the printing of sound track.


another optical system (an explanation of which is beyond the scope of this paper) was constructed and a new printer using this new straight-line optical system was put out dur­ ing the past year by J. A. Maurer, Incorporated. It has been found that the improved quality obtained by optical printing in comparison.with contact printing of 16mm sound track on color duplicating, stock is such as to be noticeable in a listening test with average reproducing equipment. There is. a. marked g a i n i n naturalness . For ex­ ample, musical instruments are clearly differentia­ ted, in an optical print, whereas they may sound almost alike .in the reproduction, from a contact print of the same negative. The sound is decidedly

19 ’brighter,1 and at the same time ’cleaner,* and the intelligibility of .speech is considerably improved.1 SYSTEM OF PRINTING Method of Timing. negative sound track.

There are various ways of timing

The visual method was quite popular

in east coast laboratories because it seemed to be the most practicable and economical, since the beginning of the development and printing of motion picture film.

With this

method the ’’timer” estimates, according to his experience, the step at which the light change system of the printer should be set to produce a balanced print.

As the "timer”


times or determines the proper printing steps, for the nega­ tive, he usually, notches it,, cutting, a notch into Its edge at a predetermined distanceahead of the beginning of each light change, for a given reel of sound track film. Some laboratories,, notably most of those on the west coast, use a timing, machine which makes a print of a section of nine to eleven frames of. each negative.

A foremost ex­

ample of such a machine, is the.. "Cinex” timer.

Each of the

frames receives an exposure that Is matched, to alternate steps of the printer, so that when the print is developed each of the nine or eleven frames represents the print

J. A. Maurer, ’’Optical Sound Track Printing,” Journal of the Society of. Motion Picture Engineers, Vol. 50, May, 1948.

20 density that would be obtained by printing with alternate lights, from step one to the highest step.

The ” timer” then

visually judges from this print the proper step at which to print the negative so that scenes of balanced density will result throughout given sequences.

Whichever system is used,

it is the custom for the ”timer" to note upon a specially designed timing card the light-s tep or light-change for each given roll of negative. The sound-track is frequently timed in this manner, but the practice of timing it by densitometric measurement is growing in favor because the problems of picture compo.sition and detail, do not complicate the assignment of printer exposures for sound-track as they do in pictorial work.


visual and densitometric methods are being used, and as the majority of sound-track are re-recorded and therefore bal­ anced for exposure, one light is generally set for printing a complete reel of negative.

Variable-density biased nega­

tive can be timed correctly only by measuring the unbiased, unmodulated portions of the track. Manner, of Printing.

After the negative picture and

negative sound-track have been timed they are given to the operator of the printer with their respective printing cards. From these cards, when resistance boards are used, the lightchanges are set up on the board for making the print from the negative, or in the case of standard Bell and Howell

21 continuous printers, the light-changes are made manually as the notched negative trips the circuit interrupter roller. In this case, as the notch trips the roller and changes the light to the manually pre-set point, the operator again manually sets the lever control for the succeeding lightchange; whereas, in the case of resistance-board operation, the electrical trip-bar is actuated by the notch-follower roller and automatically sets itself for printing the suc­ ceeding scene, according to the sequence established by the set-up of the board. After the first print is struck off and processed the timer projects it repeatedly and makes printer point corrections for raising or lowering the volume level of the reproduced sound in the various scenes in order to produce the best quality and the most desirable effect.

When the

print Is adjudged as good as can be expected, general re­ lease printing from the timed negative is begun.


laboratories print all. release prints from a given reel of negative upon the same, printer in order to minimize errors. Several rules of a general nature for the printing of sound on Kodachrome can be set down: 1. The printing aperture should be smaller than the positive image from which printing is accomplished. 2. If a variable area negative is used, the print­ ing aperture should be larger than the width of the negative record.

22 3. The projector aperture should be wider than the 16mm recorder aperture; yet smaller than the aperture used Tor printing the black and white positive.2 A few comments should be made at this point concerning variable-density linear recordings.

With regard to the

quality of sound, a good general rule of thumb is to dupli­ cate from a positive which in itself has minimum distortion. In the case of variable-density 35mm originals, it is true that a 35mm negative of gamma 0.45 which will contact print in the usual way to a gamma of 2.4. will have an excessive gamma product when optically reduced from that 35mm positive to Kodachrome; the increase in printer factor of the optical sound printer over the contact printer is possibly a cause. The case for 35mm variable-area negative tracks has the usual complications with regard to dimensions and enve­ lope effect.

If the 35mm negative is optically reduced to

a 16mm positive and this 16mm print used for the Kodachrome duplicate, only the 16mm track printer needs to be masked to print to Kodachrome from any conventional original negative either 16mm or 35mm. With regard to other types of original for sound such as toe recorded 16mm tracks or toe recorded 35mm variable density tracks, it can be said that they are few 2

W. H. ©ffenhauser, ’’Some Laboratory Problems in Processing 16mm Black and White Color Films,” 0 £. cit., Vol. 36, February 1941, p. 172.

in number, and for the most part the quality is quite poor due to the fact that the Kodachrome duplicating step, is ignored.

Variable-area master positives in either 35mm or

16mm have not put in an appearance; attempts have been made to save the cost of a track positive, but the sound proves so poor as a result and the procedure so costly in the long run, that such attempts have died out quite rapidly.


The normal processing of Ansco

color film involves the removal, of silver from the picture area leaving in its place three different dye layers.


cyan, magenta, and yellow dyes give a combined maximum den­ sity of 2.8 to 3^" which is visually opaque; however, this density does allow far-red and infrared light to be trans­ mitted. It can be readily understood that if this particular method of processing was used to process sound track the required modulations would not be opaque to infrared light and, therefore, the resulting volume would not compare favorably with that from a silver track. Because the type of sound reproducing equipment is so important to the problem at hand, that is to say, the elimination of the transmission of infrared light waves, it would be worthwhile to mention a type phototube which would allow a dye sound track to be used.

It Is possible for a

1 J. L. Forrest, "Metallic-Salt Track on Ansco 16mm Color Film," Journal of the Society of Motion Picture Engineers, Vol. 53, July 1949, p. 40.

25 sound projection unit to make use of a blue-sensitive photo­ tube to read the light beam which has been modulated by a dye type of sound track.

Inasmuch as this blue-sensitive

phototube is relatively insensitive in the infrared region of the spectrum it makes very little difference whether the dye track transmits infrared light waves, and consequently, the volume of the sound recorded would not be minimized. Now that a method for reading a modulated light beam from a dye track has been discussed, it might be said that it is very unlikely that such a blue-sensitive phototube will be used In the very near future because the cost of converting sound projection equipment would be exorbitant. Most sound projection units make use of a cesium type photo­ tube.

Because thi3 type tube is most sensitive in the infra­

red region of the spectrum, a dye sound track which transmits infrared light cannot be used advantageously for modulating a light beam.

The cesium phototube would readily pick up

the transmitted infrared waves and when combined with the light permitted through the clear area of the sound track there would be the equivalent of an unmodulated track. Therefore, the problem confronted by the Ansco people was to find a way to process their sound track so that the sound-track modulations would be opaque to Infrared waves of light and at the same time would not Interfere with the formation of a dye image track.

26 The problem was solved by processing the sound-track area of the film differently from that method used to process the picture area.

However, this method increased

the number of steps in the processing method and also r e ­ quired highly precise application equipment.

Because of

the established width of the sound-track area, highly skilled technicians had to be available to operate the equipment necessary to keep the special application confined to the limits of the sound-track area. A procedure for increasing the opacity of 16mm Ansco color duplicating film to infrared light has been worked out in which the silver halides forming the modulations are converted to silver sulphide. It has been claimed by the Ansco people that their treated sound track compares favorably in volume with a silver track when reproduced on a cesium-type or red-sensi­ tive phototube.

However, there was an increase in noise

level when the treated track was played, but not enough to be judged objectionable. For reversible-type 16mm film, the variable- , area sound track is preferable and with a track treatment of this kind on reversible color film, the characteristics of the treated track lend it best to the variable area method. The treating of the film requires equipment which

2 Ibid., p. 44

27 for economical reasons Ansco operates in connection with its other color film processing machines.

It is very important

to remember that a uniform flow of film through the equipment is most essential for the best results, and that all machines run at the normal processing speed. The Ansco process is a reversal process and as such the sound track is exposed on Ansco color duplicating film from a positive type track.

Any recorded track having

characteristics favorable for printing on black and white reversible duplicating stock will be suitable for printing on Ansco color duplicating film.

After printing the follow­

ing processing procedure is used: In complete darkness 1. 2. 5. 4. 5.

First develop.......... Rinse................... Stop .............. ...... Hardener............ . Wash and second exposure

8-14 minutes 5-10 seconds 3 minutes 3 minutes 2 minutes

After the film, has been washed it is led into the equipment which treats the sound track.

The first step here

is to dry the surface of the film to prevent the treating solution on the sound track from running into the picture track area.

This drying, process requires about 50 seconds

and is accomplished through the use of air squeegees and then passing the film, .through a small, dry-box.

After the

film has cleared the drying chamber it is led over the

28 applicator roller where the edge treating solution is applied to the sound-track area.

According to J. L. Forrest, of the

Ansco Laboratory, Binghamton, Few York, the treating solu­ tion is essentially an aqueous solution of sodium sulphide with cellosize WS-100 added to increase the viscosity. Edge Treatment Solution Formula Cellosize WS-100......................... 100 cc. Sodium Sulphide (Anhydrous)....... 20 gr. Water to make ............................ 1 liter After the reaction of this edge-treating solution, which is very rapid, requiring only 15 seconds to convert the silver halidee in the track to silver sulphide, the ex­ cess solution is washed off the sound-track area and the film is returned to the wash tank from which it was taken. The entire edge treatment requires only 75 seconds after which the film is allowed to continue in the usual manner through the color processing machine.

The following steps

complete the Ansco color reversible 16mm sound film process: In white light Finish wash......................... 1 minute Color develop....................... 10-15 minutes Rinse................................ 5-10 seconds Stop................................. 5 minutes Hardener............................. 3 minutes Wash................................. 3 minutes Bleach. 6 minutes W a s h ................................. 3 minutes Fix 6 minutes Wash................................. 9 minutes Dry

29 The application of this solution to the sound-track area requires care, but it cannot be considered a difficult task.

The procedure is straightforward and is not untidy

or odorous.

The amount of the solution, which contains

sodium sulphide, required to treat 100 feet of 16mm film is very small, being only about 10 cc. or approximately l/3 ounce.

Therefore, the handling of the solution or the carry­

ing out of .the process does, not present any outstanding problem to the laboratory.

At present this process is re­

stricted to 16mm film but there is no reason why it should not be extended to the processing of 36mm color film.


edge treating equipment comes in a small, compact, portable unit which can be moved away from the other processing machines, in order to facilitate cleaning and maintenance. The unit itself does not propel the film. accomplished entirely by the processing machine.

This is Actually,

the processing machine pulls the film through the sound­ track-treating unit.

In order that no undue strain be

placed on the film, the sound-track-treating unit is ten­ dency-driven, that is, the shafts in the rollers of the drying cabinet are turning in loose rollers.

After leaving

the drying, cabinet, the film is fed over a roller cluster to guide it accurately over the edge-treating roller.


the sound-track area comes in contact with a bead of the edge-treating solution carried in the slightly concave

30 periphery of the applicator wheel.

The bead wheel travels

at a slightly faster rate of speed than the film and in the same direction as the film.

This maintains a uniform bead

in contact with.the track area. The amount of solution applied is controlled by the depth of dip of the applicator wheel in the solution, and lateral movement of the wheel is controlled by the micro­ meter adjustments on the applicator assembly.

With these

controls, no difficulty has been confronted in confining the sound-track area within the established standards. The Eastman Silver Sulphide Track.

According to

EeRoy M. Dearing, as published in U.S. Patent 2,258,976, the production of a dye sound track in reversal processes is usually carried out in one of two ways.

The sound track

may be treated in the same manner as the picture area in which case it will contain the same dyes as those present in the picture.

The other way is to develop the sound

track image by printing in such a manner after reversal as to use only one dye for the sound image.

It is extremely

important to select that dye which has the greatest infrared absorption power in order to insure the best sound reproduc­ tion quality.

The disadvantage in using a dye track is

that the dyes available for making color images are poor infrared absorbers and consequently the maximum density to

31 infra-red is too low for satisfactory sound quality.


states that, "In general, dye sound tracks give weak volume •\

as well as poor quality sound on reproduction."*' A method for overcoming these objections is to make the sound track of metal or a metallic salt.

It is not

difficult to use silver sulphide to form the desired sound images and as a result of this method it is possible to obtain a sound track which has satisfactory contrast and whose maximum density transmits a minimum of infra-red light. The Kodachrome reversal process is one which has been used successfully to produce a silver sulphide sound track. A description of this method is as follows: Picture

Sound Track

1. Kodachrome raw stock


Black and white sound negative raw stock

2. Expose and develop


Expose and develop

3. Reversal process gives a master positive


Negative sound track


Printed and developed


Positive sound track


Printed on kodachrome duplicating stock


4. Printed on kodachrome duplicating stock


First Development Complete bleach.

The film Is passed through a bi­

chromate solution which dissolves by oxidation the silver image leaving only residual silver bromide not exposed and

32 developed. Re-expose.



The entire film Is exposed to three differ­

ent colored lights, namely,red, green, and blue.

Each sec­

tion of the emulsion is sensitive to a particular color light.

The remaining silver.bromide is exposed giving a

positive latent image. v Re-develop to get positive image on both picture area and sound track. Conversion bleach.


The film is Introduced into a

potassium ferrocyanide, solution which converts all of the silver into silver ferrocyanide.

The reason being that all

of the silver must be removed from the entire area of the film so that the various dyes, namely yellow, magenta, and cyan may be Introduced into the film.


■' '

At this point the film is tipped over on edge so that the sound track alone passes through a sodium sulphide bath converting the silver ferrocyanide in the sound track into silver sulphide which is. not soluble in hypo.

If the silver

ferrocyanide had not been converted the hypo would have dis­ solved it and there would not have been any sound track. The final step Is to pass the entire film through a hypo bath and then a wash so that the silver ferrocyanide in the picture area is dissolved leaving a dye image, and since the hypo has no effect upon the silver sulphide, that type of sound track is left.

33 Again, according to Dr. Dearing, "The sulphide sound track does not have a clean highlight and this factor has prevented its general use, due to the poor quality sound obtained."

However, this objectionable feature may be

overcome by making the sound track of silver sulphide and silver iodide.

As stated by Dr. Dearing, beneficial results

have been obtained in forming a photographic sound track by using a bath which both sulfides and iodizes the sound track. Any sulphur compound which reacts with a silver halide to produce silver sulfide, may be used in conjunction with an alkali metal iodide, such as potassium or sodium iodide. In this solution, which contains both iodide-forming and sulfide-forming compounds, the presence of the iodide prevents excessive highlight stain while the sulfide builds up the contrast and maximum density to a satisfactory level. The first step in the Dearing process is to print the sound and picture images either simultaneously or successive­ ly on a piece of photographic, film which consists of a support and three successive emulsion layers sensitive respectively to the red, green, and blue region of the spectrum.


negative metallic silver images in both the sound and picture track are formed by developing the film in an ordinary black and white developer. The bottom layer of the film, which is sensitive to red, is then exposed through the support to red light, the

54 sound-track area being masked off at this time to prevent exposure.

The film is then introduced into a blue-green

color forming developer to give a cyan positive image in the layer.

Similarly, the top layer is exposed to blue light

through the emulsion and developed in a yellow color forming developer to form a positive image in the top layer.


sound track continues to be masked during this exposure period. The sound-track area of the film is treated in an iodide or sulfide and iodide solution which will convert the positive portions of the sound-track area into a silver iodide or combined silver sulfide and silver iodide sound image. There are two ways of treating the sound-track area. The first method is to use a mechanical device known as an edge applicator which applies the solution directly to the sound-track area and makes certain that the solution is con­ fined precisely to that area.

The second way is to immerse

the edge of the film in the sulfide and iodide bath so that the picture area is not affected.

After the silver sulfide

and silver iodide sound image has been formed the middle layer picture area of the film is fogged either'chemically or by light and a magenta positive image is formed in this layer by means of a suitable color forming developer.


entire film is then introduced into a bleach and hypo bath

35 to remove all particles of metallic silver and to leave the silver sulfide and/or silver iodide sound image in the sound-track, area and the dye images in their respective layers. It is important to remember that the range of iodide and sulfide-forming compounds In the solution used to form the sound-track may be varied to give any desired contrast, as well as any highlight and maximum density.

The pH value

of the bath is controlled by adding an alkali such as sodium hydroxide to prevent the formation of hydrogen sulfide gas. A typical formula used for making the solution neces­ sary to treat sound-track area in the Dearing process Is as follows: Potassium iodide 200 grams Sodium hydroxide............. 50 grams Sodium sulfide 20 grams Water to m a k e ....... ....1000 cc. Summarizing the Dearing process it is a method of producing a sound track in a photographic film, which com­ prises printing the sound-track image, and treating the sound-track area of the film with a combined sulfiding and iodizing bath to form a combined silver sulfide and silver sound track in the film. The Technicolor Silver Track.

Due to the extreme

competition between the various processing laboratories it

36 is difficult to obtain the exact methods used by these labora­ tories in processing their film.

It has also been discovered

that each company may have a number of patents and that each patent may supply all or part of the processing method. Therefore, in discussing the Technicolor procedure, several methods are described which may possibly contain all or part of what has become known as the "Technicolor Process." According to United States Patent, No. 2,085,877, as­ signed to the Technicolor Motion Picture Corporation by L. T. Troland, the sound record may be produced by any wellknown method such as varying a light beam in accordance with the variable sound, as for example by a variable slot, ex­ posing a sensitized section of the film with this variable beam and then developing and fixing the sound record in the usual way.

The color picture record may be formed in vari­

ous ways, but the imbibition method is particularly suit­ able.

The sound record may occupy a narrow band of the film

at one side of the picture inside the sprocket holes but it is preferably located outside one row of sprocket holes so as not to reduce the area available for pictures. A preferred order of procedure consists in making the sound record of the variable light beam in a developed silver image upon one portion of the positive motion pic­ ture film, leaving the remaining portion blank for later printing the picture, developing the silver image, and then

hardening the blank portion and printing the latter portion with dyed matrices representing the different color aspects of the object field* In this way a motion picture film is obtained in which the pictures appear in their natural color or colors and the sound track appears in the form of a developed silver image. Describing this procedure in more detail it may be said that the entire surface of the film may be coated with a gelatin layer containing the usual light sensitive silver salt, or, if the pictures are to be printed by imbibition, only the space for the sound track may contain such a light sensitive silver salt while the space reserved for the pic­ ture is coated with unsensitized gelatin or other imbibition material. According to the preferred procedure the sound track is first exposed to light through a negative produced as described above simultaneously with the taking of the motion pictures.

This area is then developed in the usual way to

produce the sound record in black and white. If the pictures are to be printed by the imbibition method the gelatin covering the picture area is hardened, as by subjecting to a 5% solution of basic chrome alum, pref­ erably

after the sound record has been made.

The pictures

are then printed by the known imbibition procedure of effect­ ing intimate surface contact of the film assigned to the

58 picture area successively with the matrix films (which have been formed from the negatives exposed simultaneously with the sound record) wet with appropriate dye solutions. results in producing the printed picture.


Upon drying, the

natural color motion picture and black and white sound record are on the same film, ready for use in the usual types of sound reproducing and motion picture projecting apparatus. Of course, the advantage in having a black and white sound track is that records may be accurately repro­ duced with any good reproducing apparatus whereas good re­ production with films having the sound record as well as the picture records in color depends upon which of the two wellknown types of sound reproducing apparatus is employed, that is, whether the active metal of the photoelectric cell is potassium or caesium.

The potassium cell is most sensi­

tive to blue light whereas the caesium cell is sensitive to both red and green.

Consequently a sound track in color can­

not be adjusted to have the proper contrast for both cells and the film cannot be used interchangeably in apparatus of the types mentioned with satisfactory results in both. As can be determined from reading the previously de­ scribed processes for developing picture and sound track, it is desirable to treat chemically those two areas in a different manner.

This is very true in the case of color

59 pictures where the sound track may be silver or sulphide while the picture is developed in color.

The problem that

immediately arises Is one which pertains to the protecting of one track while the being treated.

Obviously, if

a protective coating was found which could be placed over the sound track without being affected in any way by the develop­ ing solution for the picture, the problem would readily be solved.

After the picture area had been processed the pro­

tective coating could be removed from the sound track and processed in. a manner previously disclosed.

However, it is

extremely difficult to obtain a protective coating which will hold up under the wet processing conditions and at the same time be easily removed after it has once been applied to the track. United States Patent, No. 2,330,796, was assigned to the Technicolor Motion Picture Corporation, by Gharles D. Bennes.

The object of this patented invention was to pro­

vide a method of treatment which thoroughly protected one zone while processing the other zone. According to the invention either the picture or sound track could be coated with a special lacquer which is insoluble in the various processing baths, after which the other track is processed In the usual manner.

The lacquer

is then removed with a lacquer solvent, which In turn is re­ moved with an intermediate solvent which is capable of being

40 mixed, with the lacquer solvent and also with the processing liquid, and then the zone from which the lacquer coating has been removed is processed.

The reason for the use of

the intermediate solvent is to permit the use of a hard, quick drying lacquer which is removable only with a solvent immiscible with the processing fluid. Monopak film of the Kodachrome type in which the colors are introduced into the respective strata during the development process is used in. this particular process.


various layers of the film, that is the red, green and blue sensitive layers, are exposed to the different color aspects of the beam.

After the picture has been printed the sound

track is printed.

At this point the sound-track area is

covered with a protective coating of opaque lacquer or var­ nish.

Other important properties of this lacquer are flexi­

bility, good adhesive quality, imperviousness to moisture, fast drying and easily redissolvable.

The gelatin through­

out the picture area may be hardened as soon as the protec­ tive coating has been applied to the sound track.

The pic­

ture is developed in the three color sensitive layers simul­ taneously and after the various layers have been flashed with blue, green and red lights the yellow, magenta and cyan colored positive components are produced in the picture zone. The various lights have been excluded from the sound track by virtue of the previously applied opaque protective coating.

41 After the three positive components have been color developed by the mentioned reversal process the film is first bleached to convert all of the reduced metallic silver into a compound which is soluble in the fixing solution that follows the bleaching.

The fixing solution also r e m o v e s _ s n y

unexposed silver halide remaining in the picture zone.


much as the 3ound-track area is still covered by the protec­ tive coating, the silver halide in the sound-track area is not removed in the fixing step. Before it is possible to process the sound track the protective coating must be removed.

This can be accomplished

by dissolution in any lacquer or varnish solvent that does not affect the picture area.

Inasmuch as the sound track

is to be treated with aqueous solutions after the coating is removed, and inasmuch as lacquer and varnish solvents are usually immiscible with water, after the coating has been dissolved the film is first washed with some solution such as isopropyl alcohol which is miscible both with the solvent and with water, after which the alcohol is removed in a bath of water.

After the sound-track area has been thoroughly

washed the sound track is developed with an ordinary black and white developer.

The unexposed and unreduced silver

halide is removed from the sound-track area with an ordinary fixing solution.

Thereafter the processing is completed by

washing and drying the film.

42 "Suitable compositions for the aforesaid coating and 3 coating remover comprise Coating Per Cent Nitrocellulose., ............. 10 Ester gum.............................. 5 Dibutylphthalate...................... 5 Butyl acetate............. 25 Butyl alcohol..................... 12 Amyl acetate...................... 8 ................. 8 Ethyl alcohol Toluene .......... 27 Carbon black.......................... 2 Coating Remover Butyl acetate........... Butyl alcohol....... Amyl acetate...... Ethyl alcohol..................... Toluene................. The Cinecolor Iron Track.

Per Cent 30 15 10 10 35

Cinecolor has developed

a method for processing picture and sound track simultaneous­ ly.

That Is, both of them are printed on one piece of film

and developed in the same solution.

This process varies

from the Kodachrome method previously described in that it is not a reversal process and it does not require special equipment to give the sound-track area preferential treatment, The laboratory does not process the black and white


C. D. Bennes, United States Patent No. 2,330,796 dated October 5, 1943.

45 sound track negative but leaves that part of the processing to the Individual requesting the recording..

After the nega­

tive track has been obtained it is printed on duplitized positive stock manufactured by either Eastman or DuPont. The duplitized stock is so constructed that there is emul­ sion containing a yellow dye on both sides of the base. Inasmuch as there is emulsion on both sides of the positive stock, the blue element of the picture is printed simultaneously with the red element on the other side of the stock.

After the red and blue elements have both been

contact printed, one on each side of the film, the sound track is printed on the same side of the duplitized posi­ tive stock as was the blue element of the picture. After both the red and blue picture elements and the sound track have been printed they are developed to give a silver image.

The blue side of the film containing the

sound track then receives preferential treatment by being floated on top of a blue toning solution.

Great care is

taken not to allow this solution to touch the side of the film on which the red element of the picture has been print­ ed.

As can be readily understood, if the blue tone did

reach the

other side of the stock the red element would be

completely destroyed and there would be no two color process. This solution, a conversion bleach, contains iron salts and ferricyanide.

The silver image previously formed

44 Is oxidized by the ferrieyanide solution to give silver ferrdcyanide.

Additional ferrocyanide formed in the reaction com­

bine with the ferric ions present in the bleach and precipi­ tates in situ a ferric ferrocyanide image.

This type track

is more commonly referred to as an iron track or a prussian blue track. The final step in the process is to pass the entire film through a hypo bath and then a wash so that the silver ferrocyanide is dissolved.

Since the hypo has no effect

upon the ferric ferrocyanide the prussian blue track and the blue element of the picture are unaffected. As was stated before, the negative sound track is not developed by this particular laboratory; therefore. It is necessary only to discuss the sensItometrie limits used to control the processing of the print.

In addition, the

engineers of the RCA Manufacturing Company have specified that in recording with sound recording film In RCA HighFidelity Equipment the negative sound track density shall be 2,75 when the film is developed in a positive type of developer to a control gamma of 3.40 to 3.70.

It has been

determined, by. the laboratory that the best quality variable area sound Is obtained from Its ferric ferrocyanide track when the print density, read visually, on a densitometer is .90 to 1.00 when developed to a control gamma, read on a densitometer with complementary filters, of 2.50.


45 print density for the best variable density sound was found to be .50 to .60 when developed to a control gamma of 2.50. TYPES OF PROCESSING MACHINES Continuous machines are now utilized for practically all types of film processing.

The operation of a continu­

ous developing machine is fundamentally simple, in that the undeveloped sound track film is fed directly from a feed reel into the machine, or from a feed reel to a feed ele­ vator having sufficient footage capacity at a predetermined speed to allow the feed operator enough time^ generally two to nine minutes, to splice a new roll of film onto the pre­ ceding roll so that a continuous band of film will flow con­ tinuously through the machine to the take-up reel at the end of the drying cabinet.

The splices may be either machine

made splices, produced by eyeleting or stapling, or care­ fully made cement splices.

Most of the continuous develop­

ing machines are of the roller-rack, deep-tank type, having in the wet section roller-rack parallel to the face of the film as the latter travels through the machine.

Each roller-

rack spindle is parallel to the face of the film, and the rack is from six to twelve feet in height and carries from eight to twelve loops of film, depending upon the design of the machine.

Usually there are one or two racks on each

tank, and the tanks may vary in capacity from 120 to 580

46 gallons of solution.

The racks may he so designed that

either all the racks in the wet end of the machine can be lifted vertically completely free of the tanks or the upper roller-rack may;be mounted in a fixed position, and the roller-rack in the lower part of the tank mounted upon a weighted elevator system so that it can be raised until it meets the upper roller-rack.

Invariably, in a machine in

which the film is propelled by power-driven sprockets, it is necessary that elevators be employed so that the tension of the individual film strands will be independent of the swell­ ing and the shrinking of the film.

In machines in which the

film is propelled through the machine by friction drive only, that is, by frictional contact of the film upon powerdriven rollers, there is no necessity for elevators.


film automatically slips forward or backward in accordance with its swell or shrinkage, because the power-driven rollers are always travelling at a slighter greater footage speed than the film and because the tension of the film is such that it will permit slippage. The upper racks of rollers in the wet end of the machine are generally submerged in the solution so that the film is exposed to the air only on the carry-over loop from tank to tank.

Because of specialized design, however, in

a number of machines the upper bank of rollers, whether on a rack system at right angles to the long axis of the machine

or parallel to the axis, may be from three to eighteen inches above the solution.

Usually in each machine there

are three or four tanks for development, followed by a small loop tank for rinse wash, three or four tanks for fixing, and five or six tanks for the washing.

It must be remembered

that this is the general set-up for developing machines, but that various color laboratories modify their equipment in such a manner to accommodate their particular processing method.

The number of tanks used in the wet end depends

upon the lengths of time necessary for the various processes, which in turn depend upon the number of racks in each tank and the footage speed of the machine. As the film feeds from the last wash tank of the wet end of the machine into the drying cabinets, it may feed directly or it may pass over a weighted feed elevator.


weighted elevator takes care of the slack, if any, between the drying cabinet and the wet end of the machine, and per­ mits operating either the wet end or dry end independently of the other.

This permits stopping either end of the m a ­

chine for a short time to take care of troubles that might be caused by mechanical defects or film breakage. Sometimes the wet end of the machine is In a separate room from the dry end, or both the wet and the dry ends may be in the same room.

The first arrangement permits drying

in a lighted room and developing in a dark room, whereas

48 the second requires special. Illumination or the wet and dry ends of the machine.

Invariably Wratten OA Safelights are

used for dark room illumination of the positive developing machines.

Wratten Series III (green) Safelights are used

to illuminate only the dry ends of the negative developing machine because the new fast negative films must be developed in darkness to avoid any slight possibility of "light fog.” The choice of arrangement is dependent upon the desires of the laboratory as to the ease of manipulating the film In the various types of machines. The drying sections of the machines usually have from five to twenty cabinets, the number depending upon the footage speed of the machine, the volume, the velocity, and conditioning of the air, and the type of roller-track mounting for carrying the film.

The racks in the drying

cabinet may be perpendicular or parallel to the axis of the machine.

Usually when perpendicular to the axis there are

two racks in each cabinet.

Like the racks in the wet end


the machine, this rack may carry from eight to twelve roll­ ers per rack, making eight to twelve loops of film, and they generally are from six to seven feet in helghth so that a man of normal stature can readily reach any section of the loop. In the majority of drying sections the flow of air Is counter to the direction of travel of the film, entering

49 at the bottom of the cabinet and passing out at the top into the top of the preceding cabinet and so on to the head end of the section.

Most laboratories now dry with conditioned

and filtered air. As the film comes from the drying cabinets it



up on a rewind reel mounted

on the

last drying cabinet

or on

a special rewind table next

to the

last drying cabinet.

As each machine splice passes from the last drying cabinet it is detected by an automatic trip, or noted by the inspec­ tor.

The film is then broken and another reel started on

the take-up. SENSITOMETRIC CONTROL OP SOUND TRACK DEVELOPMENT The two types of sound recording methods most widely used are the RCA photophone system, which makes use of the variable-area method of recording the sound track, and the Western Electric System, which makes use of the variabledensity method.

The laboratory control methods for the two

systems will. be treated separately, as they differ consider­ ably; and also because it is necessary to b e familiar with the sensitometric controls, used in the processing of the negative track in order to understand the printing of the negative on the color duplicating stock. Variable-Area Sound Track.

"Unless otherwise speci­

fied by the customer or the production department at the

50 studio, the laboratory develops and prints variable-area recorded sound track in accordance with the sensitoxnetric recommendations submitted to their licensees by the RCA Manufacturing Company or any other concern manufacturing sound recording equipment that records a variable-area track. The engineers of RCA specify at present that in re­ cording film in RCA high fidelity equipment the sound track density shall be 2.75 when the film is developed in a posi­ tive type of developer to a control gamma of 3.20 to 3.70. The sensitometric requirements for this specification stipulate that the laboratory determines the time of develop­ ment of the film being used for the recording to give a gamma within the prescribed limits.

It then becomes a

simple, problem to expose lamp current tests in the recorder and develop them for this determined developing time, and then select from these tests the proper lamp current to expose the sound track so that the specified density will be obtained for this development time.

Most laboratories

readily meet these specifications by developing variablearea track recorded in this manner in the regular positive bath.

The color laboratories which do process the negative


Report of Laboratory Practice Committee, Journal of the Society of Motion Picture Engineers, Vol. 26, April 1936, p. 387.

51 track minimize their control problems by maintaining, a separate machine for the development of this type of nega­ tive sound track. The recommendation for a black and white positive track is that the negative be so exposed in the printer that a density of 1.30 to 1.40 be obtained when the positive print is developed to a control gamma of 2.30 to 2.50.


is the function of the laboratory to maintain the control gammas of both the negative and the positive, and the ex­ posure density value of the positive; whereas it is the function of the recordist to maintain the negative exposure density of negative developed in the developer controlled for gamma and density. Variable-Density Sound Track.

The Western Electric

System of variable-density recording requires more detailed information for processing the variable-density sound records that utilize the straight line portion of the H & D curve.

The average laboratory develops the black and white

sound track negative in a suitable developer to obtain a gamma of .35 to .40.

Under these conditions the average

unbiased, unmodulated negative density ranges from .50 to .60, this density being controlled b y the recordist who ad­ justs his exposing lamp in accordance with the latitude of the film, which is determined by the points at which the toe and the shoulder break away from the straight line portion

52 of the characteristic log E curve.

This negative is then

so exposed in the printer that an unmodulated unbiased print density of .60 to .75 will be obtained when the black and white print is developed in the positive picture bath to a control gamma of 2.0 to 2.2.

The color laboratories,

contrasted with the laboratories making black and white sound track prints, have determined that for best quality variabledensity color sound tracks a print density of .50 to .60 should, be obtained when the color print is developed to a control gamma of 2.3 to 2.5. It is necessary that the low negative gamma be ob­ tained to secure an over-all reproduction gamma character­ istic approaching the ideal value of unity.

This over-all

gamma characteristic is the product of the positive and the negative control gamma the projection factor. The difference in gamma as determined by visual measure­ ment of the photo cell should be determined in order to assign a correction factor.

This factor has been determined

for standardized projection conditions and found to be 1.30. The correct reproduction conditions as recommended by the engineers of Electrical Research Products, are determined in the following manner: Over-all gamma* Neg Control GamraaX Pos Con GammaXFroj Factor Substituting, 1= NCgX PCg X 1.30 or NCgXPCgs0.76 According to the last equation, any combination of negative and positive control gammas that will produce a product

53 approximating 0,76 would be correct for straight line record­ ing. FIXATION AND' HARDENING The same type of fixing bath is commonly used for fixing and hardening color sound track as well as for black and white track.

Chrome alum fixing baths or bisulfite

fixing baths are sometimes used because the laboratory technicians^ believe that these formulas are more efficient and more economical. The fixation time varies with each type of continu­ ous processing machine in accordance with the design and footage speed.

As each color laboratory is privileged to

modify its processing machine in any way that it desires, it is impossible to determine when or how many times the color sound track is passed through the fixation and harden­ ing bath.

It must suffice to say, using the words of a

Cinecolor representative, ”In the processing of the color sound track it is fixed and hardened.” A few laboratories circulate the fixing bath so that the temperature can be controlled between 63 to 68 degrees fahrenheit.

In others the fixing bath is circulated and

replenished periodically with acid hardener.

The rate of

supply depends upon the results of titration tests to determine the degree of hardening throughout the life of the

54 bath.

WASH WATER There are no cut and dried rules which can be applied to the washing of color film containing picture and track. Each color laboratory has its own method of washing which include such variables as (1) the design of the processing machine,

(2) differences in the number of washes,

(5) the

amount of agitation in the wash, (4) the temperature of the wash,

(5) the particular place in the processing pro­

cedure where the wash is made, and (6) the disposal of the contaminated water. Purified Water Supply. are suitable for washing film.

Nearly all town water supplies The fresh water supply is

usually obtained directly from the city mains except for the Cinecolor Corporation, which has drilled its own wells. Brackish water, containing common salt, is to be avoided, but lime and magnesia, as carbonate and sulphate, are prob­ ably harmless, and the carbonates perhaps beneficial.


hard waters merely need more perfect surface removal by squeegeeing before drying.

Iron salts occurring in acid

waters may discolor the film, but they are not likely to affect its permanency.

Therefore, contrary to accepted

belief, the nature of the water supply is not of vital importance.

55 Before being used for any purpose in the laboratory the water is usually filtered through some type of 'commercial sand filter to remove suspended vegetable or animal matter that might be present.

So far as is known, no color labora­

tories have water so impure that it cannot be used satis­ factorily for washing film, but as a precaution the water is generally filtered and treated with chlorine. Time of Washing.

The washing arrangements in use

with continuous processing machines comprise sprays, tubes, or tanks with the main purpose of removing the hypo from the film.

All laboratories have practically the same wash

tank set-up.

That is, the film leaves the hypo bath and

is passed over a number of rollers into the washing tank. Here the film is exposed to water vigorously agitated by compressed air.

For the laboratories which object to com­

pressed air stirring because it involves costly compressors which wear unduly and which sometimes causes oil to find its way onto the film, there is an alternative, a spray of atomized water which fills the tank with mist and rinses the film equally well. In most continuous machines the film is washed for fifteen to sixty seconds between development and fixation. The time of washing following fixation varies for positive types of materials from seven to twelve minutes, and for negative types of materials from ten to sixteen minutes.

56 However efficient the washing operation, there must remain some hypo in the wash water.

The permanence of the

film is increased, therefore, if the surface layer of wash water is removed.

As drying proceeds, any water left segre­

gates into droplets which shrink down and leave all of their impurities in localized areas.

It is at these spots that

the density of the track tends to decrease.

This is a

reason for squeegeeing equally important as its effect on the appearance of the dry film. Temperature Control.

The effect of a high tempera­

ture wash on the film must be considered because it is believed by some that this tends to swell the emulsion and hinder washing.

The truth of the matter is that the emul­

sion swells in much the same degree as the high temperature wash causes the diffusion process to quicken.

The net

result i3 that in ordinary processing of color track the hypo washes out at about the same rate regardless of the temperature of the water. Only a few laboratories control the temperature of the wash water systems of their continuous developing machines.

Therefore, the temperature will vary from 50 to

75 degrees Fahrenheit, and occasionally rise to as high as 80 degrees Fahrenheit. DRYING CONDITIONS Each of the various color laboratories differ with

57 respect to their method of drying film.

This is due to

the difference in design of their developing machines, the varying operating speeds of the machines, and the varia­ tion in temperature and humidity maintained in the air. However, it is possible to present the drying conditions which can be considered average for the color laboratories in Hollywood. Air Circulation.

In all continuous machines the

film is squeegeed immediately before entering the drying cabinet or just previously to its entering the elevator system preceding the drying cabinet.

Squeegeeing by blow­

ing air at a uniform pressure at an angle of approximately thirty degrees to the film surface from a specially designed wedge slit is favored for removing excess water from the emulsion and support side.

In a few machines chamois-covered

rollers take the place of air squeegees and act in the manner of wringers.

These procedures prevent water marks which

would otherwise form on the film during drying, and materi­ ally reduce the quantity of water that would have to evapo­ rate from the film-during the drying process. Temperature and Humidity Control.

The range of con­

trol of the wet and dry bulb temperature varies considerably in the different laboratories, because the requisite condi­ tions for drying the film depend upon the footage speed of

58 the machine, which unfortunately the various color labora­ tories did not care to divulge, the volume and velocity of the air, the number of cabinets in the drying section, and the type of roller rack mounting in each cabinet. Dry bulb temperatures range from 75 degrees to about 120 degrees Fahrenheit, with humidity ranges from 25 to 60 per cent. Most laboratories, how­ ever, endeavor to maintain a dry bulb temperature range of 75 degrees to 85 degrees Fahrenheit, and a wet bulb temperature that will produce a relative humidity of 35 to 45 per cent.5 Important experimentations have been carried out which show that the density and gamma resulting from a development depend on the conditions surrounding the film while drying after development.

"High humidity and high

temperature give greater density than lower values.


higher densities result when drying takes place under such 6 conditions as to soften the gelatin during the process.” It is possible to understand the importance of this when it is remembered that densitometric tests are made on the color track to estimate the quality of the sound produced. LUBRICATION OF FILM It has become an established practice in most film laboratories to lubricate either the edges or the entire

5 Ibid., p. 398. 5

D. R. White, "Drying Conditions and Photographic Density,” Journal of the Society of Motion Picture Engineers, Vol. 19, October 1932, p. 340.

59 emulsion surface of 16mm and 55mm prints prior to projection. This practice was adopted because of the difficulties en­ countered when freshly processed prints were being pro­ jected for the first time. The gelatin in.the emulsion of freshly processed prints is very adherent to a hot metal surface and the adhesion of the film to the hot gate causes particles of gelatin to b e rubbed off the film. Some of these particles may adhere to form a crust on the metal parts of a gate, and this crust will greatly increase the frictional resistance of the film through the gate.^ The result of high friction or "sticking” as it is referred to by projectionists, is noisy and unsteady projection and often damage to the film. It is quite possible that freshly processed film w-ill project satisfactorily without being lubricated.


this depends upon the moisture content of the film and the condition of the projector.

Usually there is very little

trouble encountered if the film has been thoroughly dried, the relative humidity of the atmosphere is low, and the projector kept in excellent repair.

These factors tend to

reduce the "sticking" of the film as it passes through the projector.

If this "sticking" does occur the result may

be permanent destruction of the film or at least noisy and unsteady projection. 7 R. A. Talbot, "Lubrication of 16mm Films,"Journal of the Society of Motion Picture Engineers, September 1949. p. 286.

60 Although 16mm and 35mm films are both lubricated the methods by which this is accomplished varies for the differ­ ent films.

The motion picture industry most frequently

uses the edge-waxing method for lubricating 35mm prints. This process involves the application of a band of lowmelting paraffin to the centers of both rows of perforations on the emulsion side. Prior to sound the Eastman Kodah Company employed a dilute solution of pure mineral oil. in carbon tetrachloride. However, when sound made its appearance the coating of mineral oil impaired the quality of the sound thus causing the lubrication to be omitted from the sound track side of the film.

This resulted in the ”sticking” of the film as it

passed through the projector and a need arose for a new method for lubricating the sound track side of the print as well as the perforated side.

It was suggested that an over­

all lubrication be applied to the emulsion side.


thin coatings of certain waxes over the entire emulsion surface proved to be the solution to the problem.


coating formed a transparent layer over, the entire film surface thus providing excellent lubrication and to a certain degree, protection from scratches. Probably the most common solvent for waxes and oils is carbon tetrachloride.

It is the main constituent of

many film-treating and film-cleaning formulas; however, it

61 has one serious drawback, the toxicity of its vapors.


order for carbon tetrachloride-wax mixtures to be used, necessary care must be taken to prevent the odor from es­ caping into the work-room air where it can be readily inhaled by the laboratory workers.

Several laboratories have been

successful in placing the lubricating device, which contains the carbon tetrachloride treating solution, inside the dry­ ing cabinet between the point of dryness of the film and the take-up reel.

It is possible to block off this film treat­

ing section of the drying cabinet and to get rid of the toxic vapors througjh the use of auxiliary fans thus drawing the fumes out into the open air. The evaluation of various type film treatments can be carried out in a number of ways.

Actually, there is no

alternative to projection for making the evaluation; how­ ever, this is so costly and time-consuming that a new method for evaluating lubricants was developed by Mr. E. Seymour, of the Development Department, at the Camera Works of the Eastman Kodak Company.

This method involves the passing of

the various films to be tested through a film-friction recorder. The film to be tested Is drawn through a gate at the rate of eight frames per second. The gate is loaded with a weight of six ounces. The film, before going to the cons tant-speed take-up reel, is passed over a float roll which registers the pull in ounces per single strand of film. A footage-tension recording is made by a pen on a


62 slowly revolving drum. Before such a recording of tension is usable, It must be correlated with the behavior of the film on projectors. Projec­ tion tests show that films whose friction force lie between two and five ounces usually will project satisfactorily.® All of the following listed carbon tetrachloridewax lubricants have been tested and found to give film whose friction forces were four and a half ounces or less, and all gave films of satisfactory projection performance: CARBON TETRACHLDRIDE-WAX SOLUTIONS FOR 16mm FILM9 Max useful % Concentrated in CC14


Film Fric­ tion Ounces




Pentawax 217



Johnson’s W M 169C



Beeswax {.026% Ethyl Cellulose {.016%)



We have mentioned that the chief drawback in using carbon tetrachloride as a solvent for the wax is the toxic vapors which it tends to give off.

Recently, a new chemical

compound known as Freon 113 or trichlorotrifluoroethane has been developed which may end the search for a non-toxic, noninflammable, rapidly evaporating solvent. 8 Ibid., p. 290. 9 Ibid., p. 288.

Freon 113 will

63 dissolve various waxes in concentrations sufficient to pro­ vide good lubrication, as shown in the following table: FREON 113-WAX SOLUTIONS FOR 16mm FIIM


Max Useful % Concentrated in Freon 113


Film Friction Ounces




Cetyl alcohol



The chief drawback at present of the Freon 113 is that it is more expensive than the carbon tetrachloride. Carbon tetrachloride mixtures lubricate for less than $ .01 per 400 feet of 16mm film while the cost in the case of the Freon 113 mixtures at the present time is approximately $.06 per 400 feet of 16mm film.

It is believed that addition

al development of the Freon 113 process will reduce the cost of this lubricating method.

10 Ibid., p. 291

CHAPTER V METHODS OP FILM INSPECTION VISUALLY Essentially only two general inspections of films are made, and these apply either to the negatives when re­ ceived at the laboratory for printing or prior to printing after development, and to the finished prints prior to shipment to the theater or to the exchange.

The inspection

of negatives and prints will be treated separately, as each requires specialized methods for different purposes. Negative.

Inspections must be carefully made to

insure that oil has not been allowed to get on the negative itself.

Sound track film may become spotted with lubri­

cation oil in one or more of the following ways:

(1) as

the film passes through the recorder;

(2) during the pass­

age of the film through the printers;

(5) when the film is

run through the processing machine.

If the film becomes

spotted with oil previous to processing, the oil acts as a resistant and causes uneven development.

If the oil contacts

the film during drying, the drying of the gelatin is locally retarded and spots similar to water marks are, produced. Obviously, the only way to prevent the formation of

65 oil markings is to remove the oil immediately after it has been applied.

The effect of attempting to remove oil from

the film emulsion surface manually has been studied in great detail and the following results noted.

Negative film

that has been touched by oil should be squeegeed with a rubber squeegee and then polished with a cloth.

The squee­

geeing treatment tends to diminish the intensity of the markings and when followed by the polishing cloth the de­ veloped film was almost entirely free from markings. After processed sound track has been washed, it may be splashed accidently with oil previous to or during drying and characteristic markings may be formed.

These markings

generally show the characteristic dark boundary and lighter central portion formed by a quantity of oil too large to form a droplet and therefore become unevenly distributed over the film surface.

There is no method known of pre­

venting the formation of spots on film during drying after the oil has once been applied to the film. White spots on sound prints having a silver track, such as Technicolor, are often produced by dark brown spots of oil on the negative.

Freshly applied oil on the emulsion

side of the negative will also offset onto the positive in the printer.

If applied to the base side, the oil will off­

set onto the emulsion side when the negative is spooled, and in turn this will, offset onto the positive during

66 printing and act as a resist during development. The most satisfactory method of eliminating oil from the surface of sound track film and therefore of preventing the formation of oil spots is to pass the film through a bath of carbon tetrachloride, squeegee, and dry thoroughly prior to development.

Such a treatment can be successfully

accomplished in the various film cleaning machines presently being manufactured for that purpose. The access of oil to film can usually be prevented by care in the lubrication of machinery such as recorders, printers, and processing machines.

Sprockets, idlers, and

spindles should be oiled whenever possible by removing the sprocket or idler from the spindle and greasing the spindle with oily cloth rather than by applying oil with an oil can. Generally speaking, today the possibility of oil gaining access to the film is kept to a minimum by the designers of photographic equipment who give this problem the most care­ ful consideration. Unfortunately the present system of controlled develop­ ment of the high speed negative materials without safelight illumination prevents inspection of the exposed negative material prior to development, and provided that no trouble has been encountered when exposing the negative in the re­ corder there is no reason for the inspection by the labora­ tory technicians.

After the negative has been developed the

emulsion and support sides are carefully examined for dirt, scratches, abrasions, spots occurring during the develop­ ment or fixation,

and moisture marks. If any spots classi­

fied as removable

appear, the film iscleaned with purified

carbon tetrachloride or some similar solution before print­ ing.

Should there be scratches upon the emulsion side, an

attempt may be made to remove them by reprocessing the film, or the film may be sent to one of the firms employing re­ juvenation processes for removing or materially reducing the scratches.

Usually, however, when such defects occur,

the film having the deep scratches or abrasions, upon either the emulsion or the base side, is discarded and the sound is re-recorded.

Pine scratches in the base of the film may be

removed by polishing, which is done either by spooling the film upon a large

drum, emulsion side in, and polishing the

base manually with a fine muslin material dampened with a solution of ethyl alcohol and ammonia, or it may be polished by one of the various types of commercial polishing machines using a solution of this type. Before printing the negative, whether it be a negative developed in the laboratory or received at the laboratory, a careful inspection is made and it is cleaned and polished so that it will be as free as possible from all the above mentioned defects.

It is universal practice to clean the

negative after it has been timed for release printing, and

68 to clean it during release printing after every fifth to tenth printing.

The cleaning may be done by hand or in a

semi-automatic continuous cleaning machine.

The choice of

the method of cleaning usually depends upon the production problems of the laboratory; however, manual cleaning is passing away and the cleaning machine becoming more popular. Prints.

The inspection of release prints prior to

shipping them to the theaters or exchanges is not as exactingly done as is the inspection of negative materials prior to printing.

In some laboratories every print is projec­

tion-inspected before shipment, as to sound and picture quality and for the defects previously stated.

As a result

of the Improvements that have been made within the past few years in laboratory control, many laboratories have found it quite satisfactory to inspect by projection only the photographic quality and the presence of defects in the pic­ ture, and to inspect audibly every seventh to tenth print to evaluate the sound quality.

Sometimes only the fifth to

the tenth print is projection inspected for sound quality during release printing. audibly:

As stated before the evaluation of sound is determined by listening to every seventh to tenth print.

This is felt

to be sufficient because of the improvement in laboratory

69 controls over the. years.

However, an investigation of the

laboratories discloses that sound distortion checks are also run if requested by the contracting studio*


these .tests are performed by the producing companies supplying the sound track negative, but in the case where the studio raises a complaint against the laboratory for poor quality sound, the laboratory should be prepared to run the several tests for determining optimum processing and printing specifications. Cross-Modulation Test.

A cross-modulation method,

based on the use of two single frequencies, has been de­ veloped to determine the optimum processing and printing specifications for variable-area sound track*

This practi­

cal test when applied to 35mm film involves the use of a high frequency signal of 9000 cycles per second, or 4000 cycles per sec. when applied to 16mm film, which are modu­ lated seventy-five per cent by a low frequency sine wave of 400 cycles per second.

The low frequency signal is removed

by a high pass filter in the electrical circuit, and the remaining amplitude modulated high frequency signal is recorded on the film.

Photomicrography of such a record

indicates that the area of the developed photographic image representing the 9000 cycle wave is smaller or larger than the area exposed, depending upon the density and amplitude of the signal, with a corresponding change in the average

70 transmission of the sound track.

In other words, if the

sensitometric conditions are not correct a 400 cycle compo­ nent will appear as the result of the demodulation or recti­ fication action in the photographic process. Intermodulation Test.

The intermodulation method of

determining distortion In variable density sound records is applied to film processing for the determination of optimal negative and positive densities and over-all gamma.


ance of these parameters from those established in the past are traced to halation in the emulsion and to processing irregularities.

The use of special anti-halation emulsions

appear to reduce distortion effects. ”A suitable test for processing irregularities is the combination of 60 cycles and 2000 cycles for 35mm film, and 60 cycles and 1000 cycles for 16mm film.”'*' In both cases the high frequency signal has one-fourth the amplitude of the low frequency signal.

The 1000 or 2000cycle out-put

is usually set at 12db below that of the 60 cycle tone. Test recordings are then made of the combined 60 and 1000 or 2000 cycle waves at several values of lamp current which will give a range of negative densities which are estimated to lie below and above the desired operating density.


series of prints is then made, giving a range of print

J. G. Prayne and Hailey Wolfe, Recording, 1949, p. 414.

'Elements of Sound

71 densities above and below what might be considered the normal print density.

The resulting prints are next meas­

ured; in the intermodulation analyzer, and the percentage of intermodulation is noted for each printed condition. A 1000 cycle or 2000 cycle band-pass filter must first be selected.

If five different negative exposures are re­

corded and five prints made from them, a total of 25 prints will result. Two "families" of curves may now be plotted.


first, is the percentage of intermodulation plotted against negative density for a series of print densities.


second, is the percentage of intermodulation plotted against print density.

"The best results are found at a

visual print density of about 0.6, whereas the negative density may lie between 0.40 and 0.50 without much change in_the final result."


Reasonably good processing practice

can be represented at present by a minimum Intermodulation of about 4 per cent. As was mentioned before, all laboratories have the equipment necessary to check their processing and printing methods; however, they do not perform the actual tests unless the contracting studio has a complaint to register regarding the processing of the sound track.


Ibid., p. 414

CHAPTER VI SUMMARY AND CONCLUSIONS An effort has been made in this paper to allow the reader to follow the recorded sound track completely through the various laboratory procedures to the finished sound track on color film. emulsions,

This involves testing film

the printing of the negative track, the process­

ing of this film, and finally the lubricating and inspec­ tion of the finished print. To start at the beginning where the laboratory has received a new duplicating raw stock emulsion number, it is accepted practice to impress upon 10 to 25 foot lengths taken from one to five rolls (selected at random) of the new and the old coatings, two to five sensitometric strips on the sensitometer using the positive or negative set-up, according to the film being used.

The prints from all

sensitometric strips are made at the step setting that was correct for the old coating.

After processing all strips


and prints for the time that produced the desired photo­ graphic quality adjudged satisfactory on the old coating, the strips are read, plotted and averaged and the differenbe in gamma and density ascertained for the predetermined de­ veloping time.

Visually the timer can tell what change in

73 the printer light isi:necessary to produce the same density in the new emulsion as was obtained in the old emulsion. Printing sound track is accomplished in some labora­ tories through the use of a Bell and Howell "track” printer. However, the Bell and Howell Continuous Film Printer, Model J, is standard equipment in most laboratories.

Among the

five different methods of printing possible on this particu­ lar printer are:

(1) printing the picture area only,


printing the sound track only, and (3) printing both areas s imultane ously• It has been found that improved quality may be ob­ tained by printing on a one-to-one ratio optical sound printer rather than by contact printing 16mm sound track on color duplicating stock.

In an optical printer the nega­

tive and the positve raw stock can be moved separately at constant speeds thus the resulting prints can be free of the three defects common to contact printing of sound track: flutter, amplitude variation of high frequencies, and over­ all loss of high frequencies. There are various ways of timing negative sound track.

The visual method was quite popular in the east coast

laboratories because it seemed the most practical and econom­ ical.

Width .this'.method the "timer" estimates, according to

his experience, the step at which the light change system of the printer should be set to produce a balanced print.

The same balance has been accomplished in most west coast laboratories through the use of a "Cinex” tester.


practice of timing sound track negative by densitometric measurement is rapidly growing In favor because the problems of picture composition and detalL do not complicate the assignment of printer exposure for sound track as they do In pictorial work. There are approximately forty different companies throughout the United States processing sound track on color film; however, it was discovered that the resultant sound tracks could be broken down into four distinct types.


are the Cinecolor iron track, the Technicolor silver track, the Eastman silver sulphide track, and the Ansco dye track. It has been found that the gamma and density specifi­ cations have changed over the past twn years for processing variable-area sound track.

At present the engineers of RCA

specify that in recording with sound recording film In RCA equipment the sound track density shall be 2.75 when the film is developed In a positive type of developer to a control gamma of 3.20 to 3.70.

The recommendation for a

print is that the negative be so exposed in the printer that a density of .10 to .20 below the negative density be ob­ tained when the positive print is developed to a control gamma of 2.30 to 2.50.

However, It has been found that for

a high quality variable-area color sound track the black

75 and white negative must be exposed in the printer so that a density of 1.30 to 1.40 be obtained when the positive print is developed to a control gamma of 2.30 to 2.50. It has become an established practice in most film laboratories to lubricate the emulsion surface of 16mm and 35mm prints prior to projection.

This tends to prevent

the film from "sticking" to the hot metal gate in the pro­ jector and thus eliminate noisy and unsteady projection and damage to the film.

Probably the most common film treating

formula is a carbon tetrachloride wax mixture; however, it has one serious drawback, the toxicity of its vapors. Recently a new wax solvent, non-toxic in nature, was dis­ covered to take the place of carbon tetrachloride.

It Is

known as Preon 113, and although It is more expensive than carbon tetrachloride, the belief is that additional develop­ ment of the Freon 113 process will reduce the cost of this film lubricating method. It is impossible to say which type sound track on color film is superior.

Any difference noted by the indi­

vidual listeners between the various type sound tracks can be attributed to the human differences in hearing.

Inasmuch *

as the ultimate test is then whether or not one can hear what Is said on the screen, and each type adequately passes this test, It is safe to claim that each process will capably fulfill, the desires of the motion picture producer.



Frayne, John George and Hailey Wolfe, Elements of Sound Recording. Hew York: John Wiley & Sons, Inc., 1949. P. 414. Hees, Charles and Kenneth Edwards, The Theory of the Photographic Process. New York: The Macmillan Company, 1942. P. 976. Mack, J. E. and M. J. Martin, The Photographic Process. Hew York: McGraw-Hill Book Company, Inc., 1939. p . 386• B.


"Color In the Movies Again," Fortune, October 1934, p. 92. Jacobs, J. H., "The Processing of Colour Films, British Kinematography, September 1948, p. 109 Keane, N., "Cinecolor Moves Ahead," American Cinematog­ rapher, November 1948, p. 373. Maurer, J. A., "Sound on Film," Audio Engineering, December



Baker, J. 0., and D. H. Robinson, "Modulated High Frequency Recording as a Means of. Determining Conditions for Optimal Processing," Journal,of. the Society of Motion Picture Engineers, Vol. 30, January 1938, p. 3. Batsel, C. N., "A Non-Slip Sound Printer," Journal of the Society of Motion Picture Engineers, Vol. 23, No. 2, August 1934, p. 100.

77 Chambers, C. A., and I. D. Wratton, "The Eastman Type IIB Sensitometer as a Control Instrument in the Processing of Motion Picture Film," Journal,of the Society of Motion Picture Engineers, Vol. 21, September 1933, p. 218* Coffman, J. W., "Sound Film Processing," Journal of the Society of Motion Picture Engineers, Vol. 12, September 1928, p. 799. Crabtree, J. I., and H. S. Carlton, "Cleaning Liquids for Motion Picture Film," Journal of the Society of Motion Picture Engineers, Vol. 11, October 1927, p. 277. Crabtree, J. I., "Oil Spots on Motion Picture Film," Journal of the Society of.Motion Picture Engineers, V o l . l i , October 1927, p. 2ST _______ , "The Handling of Motion Picture Film at High Temperature," Journal of the Society of Motion Picture Engineers, Vol. 8, September 1924, p. 39. Crabtree, J., "Directional Effects in Continuous Film Processing," Journal of the Society of Motion Picture Engineers, Vol. 18, February 1932, p. 207. , "Sound Film. Printing," Journal of the Society of Motion Picture Engineers, Vol. 21, October 1933, p. 294. _______, "Uniformity in Development," Journal of the Society o7 Motion Picture Engineers, Vol. 25, December 1935, p. 512. Daily, C. R., and I. M. Chambers, "Densitometric Method of Checking the Quality of Variable Area Prints," Journal of the Society of Motion Picture Engineers, Vol. 33, October 1939, p. 398. Depue, O. B., "A Machine for Printing Picture and Sound Simultaneously and Automatically," Journal of the Society of Motion Picture Engineers, Vol. 18, May 1932, p. 643. Faulkner, T., "Cleaning' Motion Picture Positive Film, Journal of the Society of Motion Picture Engineers, Vol. 16, No-. 25, September 1926, p. 117.

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