US2393756A - Photographic color correction process - Google Patents

Description

1946. LE ROY M. DEARING v 3 3 PHOTOGRAPHIC COLOR CORRECTION PROCESS Filed larch 6, 1942 BFUSURE F 5 R BLUE SENS/WVE EMULSION.

g E R- l3 GREEN SEN6I77VEEMUL5IOM fi RED SENSITIVEEMULSION.

l0 REDSEN-SITIVEEMULSION WITH COUPLER.

, COMB/NED 8LACK-AND-HHITEAND if cow/2 DEVELOPMENTI m$lw REVERJAL EXPOSURE, COL OR OEVELOPMEN T AND REMOVAL OF. SIL VER AND SIL VER SALTS.

' amsz/RE FIG-Z BLUE SENSITIVE EMULSION NIT H f} ggay cg ge 26 WW RED AND INFRI-I-RED SENSITIVE 25 if! EMULSION.

. REEN SENSITIVE EMULSION wrm MAGENTA COUPLER. RED SENSITIVE EMULSION NITH CVAN COUPLER.

COLOR DEVELOPMENT.

INFRA -RED FLASH, cow/e DEVELOPMENT, g gI/AL 0F 67L VER AND SILVER V LEROYMDEIRING INVENTOR Patented Jan. 29, 1946 UNITED STATES PATENT OFFICE rno'roonnrmo COLOR CORRECTION PROC Le Roy M. Bearing, Rochester, N. Y., asslgnor to Eastman Kodak Company, Rocheate r, N. 'Y., a

corporation of New Jersey Application March 6, 1942, Serial No. 433,642 2 Claims. (c1. 95-2) This invention relates to processes of subtracprocesses the three dyes are not equally bad in this respect, the final result of printing such a film is to introduce unequal parts ofall three records in each image which is made, regardless of the color of light used in printing or the sensitivity of the photographic materials used. In a typical case, where less magenta o yellow dye is used and the gray scale is maintained by the blue-greens, the greens, blues and cyans of a print may be degraded with gray and are less luminous than they should be, while the magentas, yellows, and reds are lacking in 'satura, tion by virtue of dilution with white.

In the past, methods for compensating for the deficiencies of dyes in photographic subtractive color films have consisted of producing suitable metallic masks by exposure of a sensitive layer through dye images in an incorrectly color-balanced film and developing a masking image in the exposed layer. If properly exposed and developed the resultant silver image will compensate for the lack of color balance in the subtractiveiy colored film when the image is placed in register with the dye images. Processes of this type have been described in Mannes, Godowsky, and Wilder U. S. Patent 2,258,187, granted October 7, 1941, and Evans U. S. patent application, Serial No. 413,442, filed October 3, 1941, and Hanson U. S. Patent 2,336,243, granted December 7, 1943. These references describe the formation of a masking image in a masking emulsion layer after the formation 01 color images in the film, by exposure through the dye images, the quality of the masking image being determined by the characteristics of the dye images in the incorrectly colorbalanced film. The quality of the masking image is, therefore, only indirectly dependent on the original scene or object photographed.

The present invention ha for one of its objects, providing a method of color correction wherein the quality and degree or the masking image is determined directly by the original obiect exposure. Othe objects will appear herematter.

In the accompanying drawing, means for accomplishing the objects of my invention are il-- lustrated. Fig. 1 of the drawing is a flow diagram illustrating the method of applyingmy invention to a reversal process of subtractive color photography. Fig. 2 illustrates by means of a new diagram a method of applying my invention to a negative-positive process of subtractive color p oto r p y:

My invention is especially adapted to correction for deficiencies in dyes of the type'previously mentioned, wherein the greensare degraded with gray and the reds are desaturated. To correct for these errors use is made of masking layers incorporated in an original film or in a duplicate film. Images in the masking layers balance the transmission of the subtractive dyes by either giving extra exposures to those areas covered by cyan and magenta or by placing density over areas covered by other colors.

My invention, as applied to reversal processes,

will now be described by particular reference to the accompanying drawing.

In reversal processes of subtractive color photography, the general procedure is to record images in superposed differentially sensitized emulsion layers-and after development r a negative stance in Mannes and Godowsky U. S. Patent No.

2,252,718, granted August 19, 1941, Jelley and Vittum U. S. Patent 2,322,027, granted June 15, 1943, and Mannes and Godowsky U. S. Patents 2,304,939 and 2,304,940, granted December 15, 1942.

The first stage of Fig. l of the accompanying drawing shows a, film of construction similar to.

that of the prior art cited but containing an extra, masking layer, which film may be used in the present invention. A support ill of a cellulose ester or other similar material; has coated upon it the red sensitive emulsion layer ll containing; a coupler compound. This layer is designedgto Over the masking; layer H are levers l2, l3, and H which are-red receive a masking. image.

green, and blue sensitive emulsion layer spectively. The yellow filter layer li.;separates: the blue sensitive emulsion layer fromathe .red. and green sensitive emulsions. flhe, {coupler pler compounds capable of I exposure of layer ordinary black-and-white developer.

' compound contained in the masking layer I I may,

for instance, be cyanoacetanilide p-benzyl phenol or othenn'on-diflusing or protected coucoupling with the oxidation product of a developer to give a, neutral gray or colored dye image. The emulsion layer I I is given a different type of red sensitivity than that of layer I2, in the respect that the red sensitizer of layer II is capable of being destroyed in first development. A red sensitizersuitable for this purpose is pinacyanol. In addition, the emulsion has a higher blue speed than the red and green sensitive emulsion layers I2 and I3. After original exposure of the film to a colored object, it is treated with a developing solution of the following typical composition:

Sodium sulflte grams sodium hydroxide ..do 5 z-amino-fi-diethyl amino toluene hydrochloride grams' 2 p-Methyl amino phenol sulfate ....do 2 Water to -..cc 1000 As may be seen, this developer contains, in addition to the ordinary black-and-white developing agent, a developing compound the oxidation product of which will couple with the coupler compound in layer I I to give a dye image in the region of the red aspect silver image. The film now appears as shown in the second stage of Fig. 1 wherein the differentiall sensitive emulsion layers I2, I3, and I4 contain in the respective layers negative silver images IS, IT, and I8. The masking layer -II contains the silver'and dye image In case the coupler compound in layer II was cyanoacetanilide the masking image I9 would the coupler compound in the layer was p-benzyl phenol a neutral gray dye image would be formed. In certain cases it is desirable to use two developers in place of the above, in which case after original exposure, the film is developed in a color developer, as for inbe purple in color. If

stance, solution A shown later in the specifics.

tion, followed by an ordinary black-and-white developer. Subsequent processing steps include I2 to red light and development of a cyan image in the layer by use of a cyan coupler developer such as disclosed in U. S. Patent No. 2,252,718, followed by exposure of layer II to blue light and development to silver in an Thereafter, the green and blue sensitive emulsion layers I3 and I4 are re-exposed and color developed in magenta and yellow coupler developer solutions as described in the patent above cited. Thereafter, the silver and any residual silver halide is removed with a ferricyanide bleaching solution followed by a fixing solution. The film now appears as shown in the third stage of Fig. '1 wherein the positive dye images 2|, 22, and 23 are colored cyan, magenta and yellow respectively. The masking layer contains the dye image 20. In a similar manner it may be shown that the above-described process is effective in placing masking density over areas of the color film transmitting magenta. and yellow picture images.

-If the corrected transparency is to be used as an original film for duplicating, the negative masking image can be of any color as long as a complementary colored filter of equivalent densityis'used in the printing beam. It is preferred that the masking dye image be less stable in acid or alkaline solutions than the dyes making up the picture images in order that the mask ing dye my be removed without damage to the color dyes if a clear transparenc without a mask is desired at some later date. To this end, coupiers may be chosen for the masking layer which will give a dye that can be removed by weakly acid, strongly basic, moderately reducing or oxidizing baths.

' A variety of other methods may be employed for forming the masking image in the masking layer II without forming a dye image in the positive area of the masking layer. These are as follows:

1. The layer may be given an additional sensitivity to infra-red, green or deep ultra-violet. This sensitivity must stand up during negative development. The positive silver halide of the masking layer is then flashed to infra-red, green or ultra-violet light and developed to silver with an ordinary developer. Thereafter the positive dye images are formed in the remaining layers as usual by re-exposure and color-forming development.

2. The layer may contain incorporated, protected or non-difiusing coupler compounds which iii may be broken down slowly either during negative development or can be removed by treatment not affecting the color. emulsion layers. Such couplers are esters of soluble couplers which may be broken down with alkali subsequent to negative development or couplers having an aldehyde group such as hydroxy benzaldehydes, solubilized by strong bisulfite solutions in a manner similar to that described in my U. S. Patent 2,269,146, granted January 6, 1942, In addition, alkali soluble protected couplers such as disclosed in Mannes and Godowsky, U. S. Patent 2,304,940, are useful. After removal of the coupler from the masking layer the unexposed silver halide is exposed to light to which it is the most sensitive, such as infra-red or ultraviolet and the silver. image is developed in the layer. In subsequent treatment following reexposure of the other layers and coupler development, the silver images are removed with a silver solvent solution.

3. Easib' saponiflable esters of leuco dyes may be incorporated into the masking layer as couplers, as for instance,.the couplers disclosed in used. These compounds upon completion of their oxidation give dyes. The esters of these bases are little soluble but the residue may be removed by s'aponification-from the positive area of the masking layer after development of the negative dye image therein.

4. The mask layer may be composed of a finegrain silver chloride protected coupler emulsion. After negative development of the layer the positive silver halide may be removed with strong sulfite solution. In this case it is generally advisable to place the mask layer as close to the yellow filter layer as possible, or the filter dye may even be incorporated in the mask layer, and

the other emulsion layers should be slow speed moval of the residual silver halide in the mask layer is then necessary.

6. A fast red sensitive auto-positive emulsion with or without additional sensitivity in the infra-red, or ultra-violet may be used in the masking layer. The red positive in the mask layer develops in the negative developer along with the other negatives. The masking layer may then be flashed to infra-red light or ultra-violet and developed in a coupling developer producing a dye image of the chosen color, preferably gray. If the appearance of the transparency is no object I the negative silver halide in the mask layer may be flashed to red 'light along with the red sensitive color emulsion layer and both developed to cyan. The remaining dye images may be formed in the film by any chosen method, as for instance,

by means of color-forming development. In printing from a transparency of this type an amount of green light equivalent to the red mask over the highlightsmust be added to the printing light preferably by using an equivalent green filter. It is essential in this case that the contrast and maximum density of tlie cyan color positive be raised so that the resultant gamma of the red negative red mask and the cyan positive be equal to that of the magenta and yellow positive gamma taken'separately.

'In the above-described methods of producing masking images in the masking layer, the sensitometric characteristics of the masking image may obviously be controlled in several ways. For instance, if the red sensitive emulsion layer ii of Fig. 1' has high or low red sensitivity as compared to the sensitivity level of the other layers, the density of the resultant masking image will be easily controllable. the emulsion is of high or low contrast, gamma characteristics of the masking image are also controllable.

In a variation of my method wherein it is desired that the masking image be controlled by the green subject during initial exposure, to correct for incorrect absorption of the magenta dye, a green sensitivity may be conferred to the masking emulsion layer in addition-to the red sensitivity, or a separate masking layer of green sensitivity may be provided. Also, separate masking layers are not essential in that, if desired, the silver halide designed to receive the masking exposure may be incorporated in one of the picture emulsion layers. The masking emulsion layer may also be blue sensitive, but our preferred methods include only green and red sensitivity for the emulsion.

In another arrangement the masking layer is coated onto the back of the support opposite the red and green sensitive layer. The advantage of using a mask in such position, separated from the picture emulsion layers by the width of the support, is that it gives the so-called diifus'ed masking effect. This diffused mask results in higher contrast in the reversal highlight areas and hence gives a better apparent definition. Another advantage of having the mask layer on Depending on whether 1 the red or green aspect silver image in this mask emulsion layer, the image on the heels part of the film upport may be toned.

\ My invention may also be applied tothe so-' called negative-positive process of subtractive color photography in a manner now to be described with particular reference to Fig. 2 of the accompanying drawing. In the negative-positive color process the blue absorption of the usual cyan and magenta, dyes gives a difierent result on the positive than will be arrived at when making a duplicate of an original color transparency. When printing from positive to positive, the blue absorption of the cyan and magenta. dyes'results in excess yellow on blues, greens and cyans in the duplicate or print. In the negativepositive color process in which the blue, green and red aspect negatives of a multilayer film are developed to yellow, magenta, and cyan negatives respectively, the blue and green absorptions of the cyan and the blue absorption of the magenta dyes gives a different appearing positive. If such a color negative is printed onto the same type of material the blue absorption of the cyan negative gives rise to a lack of yellow in the finished positive and a correspondingly greater cyan density. In general, when a print is made by the color-negative-to-color-positive process it will lack yellow and have too much cyan. A masking method in this case to be successful must hold back the red printin onto the positive. Further, if one is to obtain better photographic scale as well as color masking, that is, decrease in contrast, the color negative must be masked in areas corresponding to the red and if necessary the green positives.

A film of the type described in Jelley and Vittum U. S. Patent 2,322,027, granted June 15,

below the yellow filter layer, may bev used in this process. A film constructed in this manner, is shown in the first stage of Fig. 2 of the accompanying drawing wherein a support IU of a cellulose ester or similar material carries red, green and blue sensitive emulsion layers 24, 25, and 21 containing cyan, magenta and yellow couplers in the respective layers. The red' sensitive emulsion layer 26 has an' additional sensitivity to infra-red or ultra-violet and isdesigned to receive a masking image. This layer contains a low contrast silver halide emulsion but does not have any coupling compound therein. It is generally desirable to coat this layer as a thinner emulsion layer than the other layers. The red the back of the support is that processing opera- 1 tions may be carried out upon it with greater ease than would be the case with a masking layer in position under the picture emulsion layers. An anti-halation layer may be coated onto the masking layer in position on the back of the support. An alternative method of processing this type of diffused mask layer, in addition to the methods already listed above, is that of toning. After the negative development, which of course, develops sensitivity of the layer is designed to correct for the blue and green light absorption of the cyan dye images and if it is sensitized to green it will tend to correct for the us a1 [blue absorption of the magenta dye.

After exposure of the film in a camera or printer, it is developed in a developing solution and coupler compounds masking layer.

remaining in the masking layer is exposed to infra-red light and developed in a low contrast developing solution containing color-developing which, in'case the masking layer is only red and infra-red sensitive and it is desired to correct only for incorrect absorption of the cyan dye, would develop a red, orange or neutral colored dye image in the masking layer. A developer 01 the type useful in developing a red or orange image is the following:

Solution A 2-amlno-5-diethylamino toluene HCl grams 2 Sodium sulfite do -10 Sodium carbonate do .40 Potassium bromide do.. 4 Potassium thiocyanate do.. 1 e-nitrobenzimidazole do 0.1 Water to -cc 950 Solution 8 Cyanoacetanilide grams 0.8 Sodium hydroxide do 5 Water to -cc 50 (Solution B is added to Solution A) A developer su'table for forming a neutral dye or protected silver image is the following:

2-amino-5-diethylamino toluene HCl grams 3 Sodium sulfite do 6 Sodium carbonate ..do 45 Potassium bromide do '1 Potassium thiocyanate do 1 p-Benzyl phenol do 4 Sodium hydroxide do 5 Water to 1iters 1 Finally, the negative silver images are removed from the layers by use of a ferricyanide'solution such as disclosed in U. S. Patent No. 2,252,718, followed by a hypo fixingsolution. The film appears as shown in the third stage of Fig. 3 wherein the color emulsion layers contain the dye images 32, 34, and 35, colored yellow, magenta, and cyan respectively. The masking layer contains the positive dye image 33.

The negative color transparency is then printed upon a sensitive film or paper of character similar to that shown in the first stage of Fig. 1 except that the copying material has no The masked color negative when color corrected print will lighting the cyans and alused for printing a then be effective in.

' lowing more printing into the yellow emulsion layer of the copy to increase the yellow, and the cyan printing will be held back.

It is to be noted. that a film constructed in the manner shown in the first stage of Fig. 2 of the drawing may be processed to give a color positive by the usual means of original exposure, negative development followed by reversal exposure and color-forming development. masking image comparable third stage of Fig. 1, i. e., a negative masking image, one means of doing this is to provide an autopositive red or green sensitive emulsion containing a suitable coupler for layer 26, the ositive area of which will .develop during negative development along with the picture emulsion negatives; thereafter the layer may be exposed to red or green light at,the same time as the red or green sensitive emulsions and developed to a dye image corresponding to the coupler wd along with the given picture emulsion layer. The

to that shown in the 'included in my invention all modifications and equivalentsfalling within the scope of the ap- In order to form a I masking emulsion layer'need not be placed be-.

tween the picture emulsions layers, but may be situated on the back of the film for reasons and advantages previously mentioned.

In a negative-positive process the masking layer in a film to be developed to a color negative, in a manner similar to that previously mentioned in respect to reversal color films, the layer may be coated on the back of the film support with the added processing advantage of enabling one to form a positive mask layer of silver iodide or other similar compound or metal which will not be removed during ordinary bleaching and fixing processes. In this method the film is first given color development whereby dye images are formed in the picture emulsion layers and a negative silver image in the masking layer. The positive masking image is then converted to silver iodide or similar compound by local application of for instance an iodide solution such as disclosed in my prior U. S. Patent 2,258,976 granted October 14, 1941. On the other hand the silver image may be toned to any othercompound or metal such as gold, uranium, Prussian blue etc. which will stand silver bleaching and fixing solutions.

In connection with my description of the method of forming mixed dye images in color films processed to color negatives, dye images of this type are a great advantage over silver from the processing standpoint, in that they can be easily localized as negative or positive images, whereas negative and positive silver are difficult to separate. Dye imagesv of this type may also be formed in films of the type shown in Fig. l, in which case more than .one coupler compound is incorporated in the masking emulsion layer.

In my invention as described herein and in the appended claims, where the sensitivity of the masking layer emulsion is either specified or only described as being adapted to receive a masking image, it is to be understood that the sensitivity is that which will allow. recording of an aspect of the original exposure, and in addition, permits treatment of the layer during processing so that a masking image is formed only in the region of the layer opposite in sign to the region of the colored picture images.

It is to be understood that the disclosure herein is by way of example and that I consider as pended claims.

What I claim is:

1. The method of forming a color correction image in a multilayer film carrying superposed silver halide emulsion layers each efiectively sensitive-to only one of the primary colors, red, green and blue, and free of coupler compounds, and a silver halide emulsion masking layer efiectively sensitive to at least one of said colors of longer wave length than blue and containing a coupler compound capable of coupling with the oxidation products of primary aromatic amino developing agents and of producing a dye image which corrects for incorrect absorption of light by dye images in said first-mentioned layers, which comprises exposing the film to a colored subject, and simultaneously with the original subject exposure, exposing the masking layer to the colored subject, and simultaneously developing silver images in all of the layers so exposed and also simultaneously developing in the same developing bath a dye image in the masking layer with a primary aromatic amino developing agent, tormposing the mm to a colored subject and simuling positive dye images by color development of the residual silver halide in the other layerstand removing the silver images and residual silver halide from the layers.

2. The method of forming a color correction image in a multi-layer film carrying superposed silver halide emulsion layers each effectively sensitive to only one of the primary colors, red, green and blue, and free of coupler compounds, and a silver halide emulsion masking-layer eifectively sensitive to at least one of said colors of longer wave length than blue and containing a coupler compound capable of coupling with the oxidation products of primaryaromatic amino developing agents and oi producing a dye image which corrects for incorrect absorption of light by dye images in said first-mentioned layers, 'the blue sensitive layer being outermost and a yellow filter layer between the blue sensitive emulsion layer and the other layers, which comprises exlayers, and then removing the silver images and residual silver halide from the layers.

taneously with the original subject exposure, exposing the masking and simultaneously all of the layers so exposed and also simultaneously developing in the same developing bath a dye image in the masking layer with a primary aromatic amino developing agent, forming positive dye images by color development: of the residual silver halide in the first-mentioned layers, the positive dye images in the first-mentioned layers being complementary in color to the sensitivity of the respective layers, and the dye image in the masking layer being of a color which corrects the incorrect absorption of light by at least one of the dye images in the first-mentioned LE ROY M. anama.

layer to the colored'subject,

developing silver images in

Images