US2371746A - Photographic color correction process - Google Patents

Description

March 20, 1945. R EVANS :1- AL 2,371,746

PHOTOGRAPHICICOLOR CORRECTION PROCESS Filed Dec. 12, 1942 FIG. 1!.

RED SENSITIVE EMULSION 00;.0R TRA NSFHRENCY Fl LIGHT EXPOSURE ETCH/NG, DYE/N6 GRAY ADHESIVE LA YER C 0L 0R- TRANSPA RE NC Y RALPH M. EVANS WESLEY T. IiANSON, JR.

Q FM M parency, but "also the deficiencies in Patented Mar. 20, 1945 PHOTOGRAPHIC I COLOR CORRECTION PROCESS Ralph M. Evans and Wesley '1. Hanson, J12, Roch ester, N. Y., assignors to Eastman Kodak Company, RochestentN. Y., a corporation of New J ersey Application December 12, 1942, Serial No. 468,776 o1. 95-2-) Claims.

This invention relates .to subtractive color phoraphy and more particularly to a color-cor rection process for. subtractive color photography.

In the preparation of subtractive color photographs it is a well-known practice to make allowonce for the fact'that the light absorptions of the dyes or coloring materials of the process are application, Serial No. 413,442, filed October 3,

. 1941, and elsewhere.

extended to the whole visible spectrum rather than to one part thereof and in most three-color processes the dyes are not equally bad in this respect. This is generally accomplished by using the subtractive dyes in aproportion such that the gray scale will be balanced, that is, in a proportion such that the whites and blacks will be uncolored. More specifically, the generalpractice may be to useless yellow than magenta or I cyan to compensate for the blue light'absorption of the cyan and magenta dyes, and to use less magenta than cyan to compensate for the green light absorption of the cyan dye. As a consequence of balancing the color materials in this manner, there is generally obtained a picture In duplicating subtractive color transparem cies, another effect has been observed which prevents obtaining pictures in natural colors. For. example, it has been found that when a'given transparency to be duplicated contains a magenta image, in the corresponding region of the duplicate there is obtained animage which is colored orange. This is apparently due to incorrect gammaoij the magenta image. Such errors may be a characteristic of a given process or of a. given single, photograph made in' that process. Also in certain cases correct reproduction may not be .desired. For example, in special cases it may be desirableto reproduce a color which is red in the original photograph as orange or magenta.

Also, in printing color-corrected photographs by means of color-correction masks it is frequently desirable to remove the mask from the v color transparency in order to compare the transhavinga degradation of colors, that is, the green,

blue and cyan colors are too dark, and on the other hand, the red,yellow, and magenta colors are too bright. i

Also, in printing from multicolored original transparencies which consist in whole or in part of dyes, the fact that the light absorption of the dyes. is extended to the whole spectrum rather than to one part of the spectrum makes it impossible to obtain printed records of the individual dyes simply by restricting the color of the printing light. Since in most three-color photographic processes the three dyes are not equally bad in this respect, the final result of printing such film is to introduce unequal parts of all three records in each image which is made, regardless of the color of. light usedfin printing or the sensitivity of the photographic materials used. The general result is to obtain a print in parency withthe print or duplicate. To this end it is desirable than the mask either be detachable from and replaceable in registry with the color which the colors are degraded as above described or may even show more degradation due not only to deficiencies in the dyes in the original transthe dyes used in the duplicating process.

The usual method 01 compensating for the deficiencies of the dyes in such processes consists in using a negative color-correction mask in conjunction with the transparency when making the printing exposure. The mask may, for exam-' ple, be prepared and used as described in the prior Evans U;. S. Patent No."2,203,653, granted June 4, 1940; Hanson U; ,8. Patent No. 2,294,981,- granted September 8, 1942; Evans U. s. patent transparency or the masking image itself be readily removable and replaceable on the color transparency.

One object of the present invention is to provide a method for the color-correction 01' subtractive'color transparencies which utilizes masks or masking images readily detachable or removable from, and replaceable on,- color transparencies.

' Another obiectis to describe a method of color I correction which corrects forerrorsin saturation of, colors.

Another object of .theinvention is to describe a method of color correction which corrects for errors in the saturation of colors and also corroots for gamma errors of colors. I

Another object is to describe a method of re producing an image 'of an original color trains"- parency' as an image of a color or contrast desired.

Another object of the invention is to describe I a method of making a-color-correction mask in which local changes may be made to compensate for errors in contrast andsaturation of colors.-

Another object is to describe a method 01 mak ing a color correction mask which is, readily removable from and replaceable on a color transparency.

c Other objects will vappeanfrom the following description.

layer 12.

These objects are accomplished by making a colloid relief mask from asubtractive color transparency, dyeing the relief mask and if desired retouching it with a colored dye and using the mask in the reproduction of the subtractive color transparency.

My invention is illustrated as shown in the accompanying drawing wherein, a

Fig. 1 shows by means of enlarged cross-sectional views of photographic films employed, the

various steps in making a colloid relief color-correction mask in the manner of the invention.

Fig. 2 shows in enlarged cross-sectional view a photographic color transparency provided with a colloid relief color-correction mask.

The general method we use for forming a colorcorrection mask comprises the steps of exposing an unhardened light-sensitive silver halide emulsion layer containing a colloid, for example, gelatin, adapted for forming relief images, through a photographic subtractive color transparency, for example, produced by the process of Mannes and Godowsky, U. 8. Patent 2,252,718, granted August 19, 1941, with a wave length of light required to give correction for the principal light absorption errors of the dyes, the wave length being selected if desired in the manner described in the Hanson U. S. Patent 2,294,981, above-cited, that isyusing substantially monochromatic light. The wave length will, in general, be longer than blue unless a mask is required which'will place density back ofcolors other than the reds, yellows, or magentas'; Afterexposure of the sensitive layer it is processed in a well-known manner to a colloid "relief image which is a negative in respect to the transparency of which it is a rec ord, that is, if the original transparency is a color negative or positive, the relief image is apositive or negative, respectively.

The relief image is then dyed, for example, with a gray dye and the dyed relief image is then 'transferred mechanically to, and placed in registry with, the original color transparency and then the color print is made by printing'from the combination. In an alternative manner, the sensitive emulsion layer may be laminated onto the color transparency and exposed thereon, then the parency, then the red sensitive film is removed from the transparency, etched in a well-known manner, and the silver-free relief thus obtained is dyed up with a gray dye such as Comacid Black. The gray dyed relief film appears as shown in the second stage of Fig. 1 wherein the support Ill carries the gray dyed red light relief record is. of the red and magenta images of the color transparency. The relief mask may then be placed in registry with the color transparency of which it is a negative record and a color-corrected print is made by exposingthrough the combination. The mask used in this manner places gray density back of the red colors of the transparency with the result that all colors of the transparency willhave substantially the same amount of impurity and will have substantially the same printlng' value. The reproduction process may be one in which the copying film carries differentially sensitive emulsion layers, with or without coupler compounds in the layers, and processing is by means of color-forming development whereby a coupler compound reacts with the oxidation prodnot of the developing compound to produce subtractively colored dye images in the layers.

As previously mentioned, if it is known that the duplicating process will, for example, give-an orange-colored magenta image, the gray relief image may be retouched with magenta dye either replacing or adding to the gray dye in the area of the relief corresponding to the, area exposed through the magenta image of the original transparency. .The third stage of Fig. 1 shows the appearanceof the mask after retouching wherein support l0 carries the relief image dyed gray in area II, the area exposed through the red image ofthe transparency, and dyed magenta in area ifl tne area corresponding to exposure through the magenta image of the transparency. This dyed relief masking image is formed in the layer without removal from the transparency.

Our invention will now be described in more detail with reference to the accompanying drawing.

forming the colloid relief image may be constructed as shown in ,the first stage of Fig. 1 of the drawing, that is, comprised of a transparent support l0, for example, of cellulose ester, carrying a red-sensitive gelatin silver halide emulsion For the purpose of the present example, since it is desired to produce a relief image of' low, gamma by-red exposure, the emulsion is dyed cyan with'a dye readily removable inthe processing solutions. Ingeneral, the emulsion is colored with a dye complementary to, or at least absorptive of, the exposing light used.

This sensitive masking film is placed on the co1or-- transparency as shownin the first stage of 'Fig. 1, the transparency having a transparent support I i of suitable material such as a cellulose ester carrying gelatin layers-l3, l4, and 15, containing cyan.' magent'a, and yellow dyes in the respective layers so distributed for purposes of illustration that blue, green, red, magenta and black images, are presentin the transparency. A red light exposure is made through the trans- The light-sensitive emulsion layer. used for color transparency. i any time to compare the original transparency with the printand later with a minimum of effort dyed relief is then placed in registry with the original transparency and-a color-corrected print may be made from the combination. Fig. 2 shows the relief mask laminated to the original trans.- parency prior'to printing, by means of the adhesive layer IS. The composition and means of applying this layer are to be described subsequently.

The advantages of the masks of our invention will now be apparent. Since the ask is composed of a gelatin relief image it 1 possible at any time to remove the 'dye image leaving a colorless relief image on the transparency which in no way interferes with the appearance of the It is, therefore, possible at the dye may be replaced in the relief in the same or a different distribution than originally present, as may be required from the appearance of the print. Also, since the dye masking image is readily removable the invention permits return of a colored transparency to a customer without. any visible alteration and should it later be desired that other color-corrected prints be made from the same transparency the attachedrelief mask is dyed up as required for color correction. An enormous saving ,in time and materials, as well .as improved quality, are thereby attained.

- In an alternative manner, and this constitutes a preferred embodiment of our invention, a photographic stripping film constructed as described in Nadeau et al., U. S Patent 2,266,435, granted December 16,-1941, or other stripping film havin a substantially water impermeable permanent support for' the emulsion layer may be used as the source of the sensitive emulsion layer in which the relief masking image is formed. The sensitive film may be stripped from the stripping film directly onto the color transparency to be corrected to form an element constructed asv shown in the first stage of Fig. 1 and processed to a dyed relief record of the transparency and used for printing as previously described, or the sensitive emulsion layer may be stripped from the stripping film and laminated onto the color transparency with a solution of the following composition:

. Percent Gelatin 3-6 Water l 80 Glycerin 15 to which are added Turkey red oil in the proporand, glacial acetic acid to the extent of per cent of the weight of the'gelatin.- The emulsion is then exposed and processed in contact with the'color transparency to a 'dyed relief mask in the manner. previously described, the impermeable support of thestripping film preventing the processing solutions from attacking the dye images in the color transparency. Thecolor transparenc having the relief mask attached would then appear as shown in Fig. 2. Since the mask is formedin registry with the images of the transparency, there is no problem of regisa good black image. Also, three dyes may be used .tion of 15 per cent of the weight of the gelatin 6. If-desired, the colorless relief mask may be dyed with 'a mixture of dyes, e. g-. two dy s iv n a color not readily obtainable in a single dye, or

as in a specific case, Orange II mixed with An-- thraquinone Blue 3G in suitable proportions gives in admixture to obtain black. Similarly, a mixture of two or three dyes may be used in a retouching solution to add either black or a color locally to the mask.

It follows from the above description that the relief masks of the invention may be only grayif the usual correction for color saturation is desired, or the gray mask may be retouched to locally increase or decrease gray. The'maskmay be colored throughout or be gray and locally colored to add color to gray or to. replace it locally. In the specific case illustrated above, a magenta dye was used to correct for deficiencies in the magenta of the print. The process is likewise adaptable to the correction of other colors, for example, if there is a tendency for the green of theprint to become yellow during the reproduction process the mask may be exposed with green, light and retouched with a difiusible cyan dye.

Thus, the color added to the mask, effectively,

tering the transparency and mask before printing, whereas if the mask is processed separately from the transparency it must later be registered therewith before printing,

Our invention is subject to numerous variations of which the following are given as examples thereof:

-l. The colorless relief mask may be dyed only gray and used in conjunction with the transparency to effect colorcorrection in printing.

2. The colorless relief mask may be dyed to a color related to the printing light recording it as described in Evans U. S. patent application, Serial No. 413,442, filed October 3, 1941, and if desired may be retouched with gray or colored dye, or it may first be dyed gray and the gray dye totally replaced with colored ,dye.

3. The colorless relief mask may be dyed gray and retouched in the desired region inthe manner described with a dye either adding to gray in the retouched area or replacing grayin the retouched area. In the first case, the colored dye solution is made sufficiently acid to keep the gray dye'in the retouched region from coming out and the concentration of colored dye, in the solution is such that the colored dye is added to gray in the retouched region. In the second case the dye of the retouching solution merely replaces the gray dye in the retouched region.

4. By use of a solution of a gray dye of greater concentration than previously used for dyeing the mask gray, the overall density of themask may be increased or if the dye solution is used for retouching, gray may be increased in theparticular retouched region, thereb either producing a general or local alteration in contrast to white light.

5. If it is desired to or the color of the mask, the mask may be treated with a dilute ammonia solution to remove the gray or colored dye. Similarly, ammonia solution may be used for retouching the mask when it is desired to removeg'ray or colored dye in a particular region of the relief.

increase the overall gray said re'lief image,

image.

must be absorptive of the color contamination which would otherwise be produced intheflnal It is to be understood that herein and in the j appended claims where we .use the terms "retouching or "retouched" we mean to include making any changes whatsoever in an originally dyed colloid relief mask for example, converting a gray relief mask to a colored relief mask, .or lmally treating a gray or colored relief mask with gray or colored dye. treating dyed relief masks with suitable solutions ing image.

It is to be understood that the disclosure herein locally affecting the gray or colored relief maskis. by way of example and that weconsider as a part of our invention all modifications and equivalents falling within the scope of the appended- 2 A process of making a color-corrected photograph which comprises exposing a light-sensitive silver halide emulsion layer through a photographic color transparency with light recording an image of the color to be corrected, forming a relief image in the exposed emulsion layer, dyeing said relief imag with a water-soluble gray dye, retouching said gray-dyed relief image and print! ing a color-corrected picture from the combination of said transparency'in registry with said 4 retouched relief image.

3. A processof making a color-corrected photograph which comprises exposing-a light-sensitivesilver halideemulsion layer'through a. photographic color transparency with light recording an image of thecolor to be corrected, forming a relief image in the exposed emulsion layendyeing said, relief image with a water-soluble gray dye,

Also, the terms: include retouching said gray-dyed relief image with at least one colored dyereplacing gray dye in the retouched region and printing a color-corrected picture from thecombination of said transparncy in registry with said retouched relief image. I 4. A process of making a, color-corrected phot ograph which comprises exposing a light-sensitive silver halide emulsion layer through a photogrflphic color transparency with light recording an image of the color to be corrected, forming a relief image in the exposed emulsion layer, dyemg said relief image with a water-soluble gray dye, retouching said gray-dyed relief image with a gray dye increasing the amount of gray in the retouched region and printing a color-corrected picture from the combination of said transparency in registry with said retouched relief image.

5. A process of making a color-corrected photog'raph which comprises providing a photographic color transparency with a light-sensitive silver halide emulsion layer, exposing said emulsion layer through said transparency with light recording an image of the color to be corrected, forming a relief image in the exposed emulsion layer, dyeing said relief image with a watersoluble gray dye, retouching said gray-dyed relief image with at least'one colored dye replacing gray dye in the retouched region and printing a color-corrected picture from said transparency masked by said retouched reliei image.

RALPH M. Evans, WESLEY T. HANSON; JR.

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