US3162533A - Method and means for controlling photographic masks and color selections - Google Patents

Description

Dec. 22, 1964 METHOD Filed 001;. 3, 1960 P. P. DE PELSMAKER ETAL AND MEANS FOR CONTROLLING PHOTOGRAPHIC MASKS AND COLOR SELECTIONS 5 Sheets-Sheet 1 WHITE AREA FOR COMPARISON WITH CYAN, MAGENTA AND YELLOW COLORS w TO DETERMINE CORRECT EXPOSURE OF ALLSEPARATION NEGATIVES DARK GREY AREA FOR DETERMINATION OF PROPER EXPOSURE OF COLOR MASK LIGHT GREY AREA FOR DETERMINATION OF PROPER DEVELOPMENT OF COLOR MASK CYAN COLOR TO DETERMINE coRREcT EXPOSURE 0F RED FILTER SEPARATION NEGATIVE YELLOW COLOR TO DETERMINE CORRECT SEPARATION NEGATIVE EXPOSURE OF BLUE FILTER MASKING STRIP FOR OPAQUE AND TRANSPARENT ORIGINALS FIG. I

Dec. 22, 1964 P. P. DE PELSMAKER ETAL 31 2 METHOD AND MEANS FOR CONTROLLING PHOTOGRAPHIC 6 MASKS AND COLOR SELECTIONS 3 Sheets-Sheet 2 Filed Oct. 3, 1960 mEPm 0Zm 2 025: com mwmoomm D 1964 P P. DE PELSMAKER ETAL METHOD AND MEANS FOR CONTROLLING PHOTOGRAPHIC MASKS AND COLOR E Filed Oct. 3. 1960 LECTIONS DENSITY PORTION RECTILINEAR PART TOE SHOULDER PORTION 3 Sheets-Sheet 3 EXPOSURE DARK GREY LIGHT GREY AREA AREA FIG. 3

MAGENTA COLOR COUPLER (I) SENSITIVE T0 BLUE AND RED LIGHT CYAN YELLOW COLOR COUPLER I3) SENSITIVE TO GREEN LIGHT TRANSPARENT SUPPORT MATERIAL YELLOW FILTER LAYER I I I I MASKING FILM United States Patent Ofifice My 3,152,533 Patented Dec. 22, 1954 33 METHQD AND R'IEANS F OR CONTRDLLIN B ro. TOGRAPHTC MASKS AND CGLOR SELECTIQNS Paul rare; De Pelsinaker, Eae em-Antwerp, and Joseph Louis De Keri, hiortsel-An twerp, Belgium, assignors to Gevaert Photo-Producten N.V., Marisol-Antwerp, Belium, a Belgian Company Filed Set. 3, 196%, Ser. N 59,790 Claims. {CL 96-6) The present invention relates to a method and means for controlling photographic masks for and color separations of color transparencies, color negatives and originals viewed by reflection.

One means heretofore employed for the control of photographic masks and color separations has been to reproduce a determined part of a grey wedge in a density range equal to the density range of the original to be reproduced. This method, however, does not, in all in stances,- assure the best control since the measurement of the density range in color originals is rather difiicult and unreliable and because the grey requirement for the different kinds of dyestuifs differs. Another method which has been followed has been the use of a control strip or a control card consisting of a grey Wedge and three color wedges. This control method, however, is likewise not completely reliable.

The present invention may be better understood by referring to the drawings in which:

FIGURE I is a schematic View of a control member or strip useful in this invention;

FIGURE II is a flow diagram of the major steps of this invention;

FIGURE III is a graph of a typical sensitometric curve useful in describin the grey control areas of the control member of this invention; and

FIGURE IV is a schematic View of a masking film with which the control member of this invention may be used.

In the instant invention, we have discovered a control method which is simple, and may be employed universally in the sense that it is applicable to all kinds of originals irrespective of the dyestuffs used. According to the presour invention, a control member, which may be in the form of a strip, is employed. The control includes two grey areas, one white area and three colored areas. Preferably, the three colored areas are cyan, magenta and yellow. For use with transparent originals, the control or strip is of transparent material and for use with nontransparent originals to be viewed by reflection, a nontransparent control or strip is employed. The control member or strip is photographed together with the original.

The two grey areas of the control are used for checking the quality of photographic masks and for controlling the exposure and density range of the masks. These two areas are rendered on the mask with a predetermined density. The white and colored areas permit control of the balance of the color separation negatives. These latter areas are used to check the quality of the separation negatives and show the proper exposure and development of the color separation negatives.

The two grey areas are of different density. The density of the darker area of the control member or strip is selected so that, when a determined exposure time is observed, the original is exposed as much as possible on the rectilinear part of the sensitometric curve of the masking material. As shown in FIGURE III, a typical sensitometric curve is a graph of exposure time against density produced in a light sensitive emulsion and is characteristic of the film emulsion employed. The curve as shown consists of a toe portion in which the shadows of an original are reproduced, a central straight line portion or rectilinear part, and a shoulder portion in which the high lights of an original are reproduced. The density of the image produced increases in the direction of the arrow. The slope of the straight line portion or rectilinear part of the curve is called the gamma of the light sensitive material represented by the curve. In preparing a curve such as FIGURE HI, it is necessary that the conditions of development remain constant. That is, the time of development; the temperature of the developing solution, etc., remain constant as exposure times are varied. The density of the dark grey area of the control member or strip is selected so that its photographic rendering will fall at point A in the rectilinear part of FIGURE III. Similarly the density of the light grey area of the control member or strip is selected so that its photographic rendering will fall at point B in the rectilinear part of FIG- URE III. While two such densities of grey may occur in the original being reproduced, the necessity of locating those two points in the rendering of the original is eliminated by use of the two grey areas of the control member or strip. The density of the reproduction of the darker area allows checking the masking film for correct exposure. The density of the lighter grey area of the control or strip is so selected that a certain difference between the densities of the reproductions of the two grey areas will appear on the mask. The reproduction of this light grey area permits checking and control in the development of the masking film. The checking of the quality of the exposed and processed mask is checked by measuring the density of the rendering of the light and dark grey areas of the control member or strip which were exposed together with the original. The quality of the development is checked by comparing the rendering of the light grey area with the predetermined values that are known to produce optimum masking quality. The quality of the exposure is checked by comparing the rendering of the dark grey area with predetermined values that are known to produce optimum masking quality.

The colors of the three colored areas which, preferably, are cyan, magenta and yellow, should be at least as pure and saturated as the dyestutf or printing ink which is to be used to reproduce the original in mass quantities and show the same density on an ideal separation negative. That is, the colors and densities of the three colored areas are selected so that they compensate for the side absorptions of the printing dyes. The rendition of each of the three colors when exposed through its complementary separation filter should be approximately equal. That is, the rendition of the cyan area on the red filter separation negative should have approximately the same density as the rendition of the magenta area on the green filter negative and the same density as the rendition of the yellow area on the blue filter separation negative. \Vhen controlling the quality of color separation negatives, one of the three colors of the control or strip is selected for starting purposes. The color selected is so exposed and developed that its contrast range that is, the difference between the maximum and minimum densities, measured in the image, fully meets the practical requirements. The density of the reproduction of the white area of the control member or strip and the density of its color area, complementary to the color separation filter, are then measured without the necessity of measurement in the images themselves. A similar measurement is made of the white area and of a color area of the control member or strip in the two other color separation negatives. If the measurements of the white area and the respective complementary color areas are approximately the same on each of the separation negatives, then the proper grey balance of the three separation negatives has been obtained. As a practical matter this may be determined by comparing the density of the rendition of the complementary colors in each of the separation negatives as discussed above.

If the minimum density and the contrast range of the first color separation negative fully meet practical requirei'n'ents, it is Certain that all separation negatives are of good quality and will be balanced if the reproduction of the white and the color areas of the control member or strip has the same density on all color separation negatives.

In the following illustration describing a practical example of the use of a control member or strip in accordance with the instant invention for making masked color separation negatives of a color transparency using a correction mask, the correction mask is produced on masking film of the type disclosed and described in US. patent application Serial No. 2,362, filed January 14,1960 and by Reprorama 10, International Bulletin for Graphic Information, published in 1959 by the Gevaert Co. This correction mask is arranged substantially as shown in FIGURE IV of the drawings in which three different color layers are coated on a support material. The top layer contains a magenta color coupler and is sensitized to blue and red light; the intermediate layer contains a cyan color coupler and is sensitized to blue and green light, and the lower layer contains a color coupler for yellow and is sensitized to green light. A yellow filter layer for the blue light, is interposed between the yellow and cyan layers in order to prevent blue light from sensitizing the naturally blue sensitive yellow layer. In practice a color correction mask of this type provides for an optimum color correction of the side absorptions of the commercial dyestufi" used in color reproduction as explained in application Serial No. 2,362.

The material to be reproduced in color is placed in a printing apparatus with the color control member or strip of the instant invention mounted adjacent the material and is reproduced along with the color control member or strip on the masking film of the aforementioned patent application. The exposure and development of the mask is controlled with reference to the rendition of the grey control areas. Thus, the exposure time is so regulated that the density of the darker grey area of the control member or strip is reproduced on the masked film with a density ranging between 0.2 and 0.4, which density is determined by the contrast range of the transparency. If, after developing and bleach-fixing the masking film, density of the image of the darker grey area of the control member or strip is found to be reproduced by a density range between 0.2 and 0.4, the exposure was correct. If the density of this area reproduced on the film mask is lower, the film mask was underexposed and an increase in exposure time is required. If, on the other hand, the density in this area on the film mask is too high, the film mask was overexposed and the exposure should be reduced. When the density of the image of the darker grey area of the control member or strip which is reproduced on the masking film is not within the aforestated density range, the exposure time is adjusted and another reproduction made on the mask film. This procedure is' repeated until the reproduction of the darker grey area on the mask film on the developed and bleachfixed mask film is within the proper density range. Once a reproduction within the proper range has been made further processing can proceed.

The density of the reproduction of the light grey area of the control member or strip on the mask film allows the development of the film to be checked. The difference between the densities of the reproduction of the two grey areas on the mask film should amount to 0.5 to

0.8. If the reproduction of the light grey area of the control strip on the mask film has too low a density, this'lack of density shows that the mask possesses too little contrast which may be due to exhausted developer, too low a temperature in the developing bath, or a similar de ficiency in the developing process. If the reproduction of 4 the lighter grey area has too high a density, the mask film has too much contrast. This may have been caused by overdevelopment, too high a temperature of the developing bath, or a similar deficiency.

After the mask film has been properly exposed and developed as determined from the two grey areas, as described above, the separation negatives are then made from the combination color transparency and film mask. By checking and changing the densities with which the three color areas and the white area of the control member or strip are reproduced on the different separation negatives, it can be assured that these negatives are correctly exposed and developed. Starting with, for example, a red filter negative, the negative is exposed in such a way that it possesses a minimum density of 0.3 and a maximum density of 1.6 in the image, giving a density range of 1.3 according to practical requirements. For the other separation negatives, it is sufficient to make comparative measurements on the color control strip as represented in each negative as described above. The measurements applicable to the different color selections are as follows:

On the red filter negative; the density reproduction of the white and the cyan area of the control strip;

On the green filter negative; the density reproduction of the white and magenta area of the control strip;

On the blue filter negative; the density reproduction of the white and the yellow area of the control strip.

As stated above, if the first separation negative, for example, the red separation negative, is satisfactory from the practical standpoint, then the other negatives will also be satisfactory if, on these negatives, the reproduction of the white and appropriate color area from the control strip have the same density as those reproduced on the red filter negative. That is, on the green filter negative, the white and magenta areas from the control strip should have the same density as the white and cyan areas reproduced on the red filter negative and, on the blue filternegative, the white and yellow area reproductions should have the same density as the white and cyan areas on the red filter negative. It is, of course, not necessary to have complete equality of densities to produce satisfactory reproductions and the instant invention is not limited to such optimum results.

The reproduction densities of the cyanQmagenta and yellow areas from the control strip on the red, green and blue filter negatives, respectively, serve as standards for exposure. The densities of the reproductions of the white area from the control strip on the respective negatives serve as standards for the developments.

In the foregoing example a transparent control strip was employed since the color selections were made from a color transparency. It is to be understood, when the original is viewed by reflection a non-transparent control strip or member is employed.

While the instant invention has been described utilizing the multiple masking film of aforementioned U.S. patent application Serial No. 2,362, it has equal utility with separate masks. In such cases however, the densities of the areas on the control strip and the recommended densities on the mask material are desirably determined by considering the sensitometric curve of the emulsion that is used.

Since the light and dark grey control areas and the white and color control areas perform different func tions, that is, the former areas are employed to control the exposure and development of the mask and the latter areas are employed to control the exposure and development of the color separation negatives, it is not necessary for one control strip or member to incorporate both sets of control areas. A control member or strip incorporating either set of control areas is useful for its own particular control function, irrespective of whether sw ns or not a control embodying the other control areas is employed.

The method of this invention may be summarized as follows: 7

1) A light sensitive material is exposed to the object being reproduced and to the control member or strip.

(2) The exposed light sensitive material of step 1 is processed to produce a mask.

(3) The quality of the mask densities is checked by comparing the rendering of the light and dark grey areas of the control member or strip. The density of the rendering of the dark grey area should be in the range of 0.2 to 0.4. The difference in density between the light grey and dark grey areas should be in the range of 0.5 to 0.8.

(4) A; second light sensitive emulsion is exposed to the object being reproduced.

(a) The mask from steps 1, 2 and 3 is interposed be tween the object and the light sensitive emulsion, as the exposure is carried out.

(b) A red filter is also interposed between the object and the light sensitive emulsion as the exposure is carried out.

(5) The light sensitive emulsion of step 4- is processed to produce a first separation negative for the production of a cyan color plate.

(6) The quality of the separation negative of steps 4 and 5 is checked by comparing the densities of rendition of the cyan area and white area of the control member and accepting the negative if the difference in densities of the two' areas is about 1 .3.

(7) A third light sensitive emulsion is exposed to the object being reproduced.

(a) The mask from steps 1, 2 and 3 is interposed between the object and the light sensitive emulsion as the exposure is carried out.

(b) A green filter is also interposed between the object and the light sensitive emulsion as the exposure is carried the magenta area of the control member on the second separation negative and accepting the second separation negative if the densities are substantially equal.

(10) A fourth light sensitive emulsion is exposed to the object being reproduced.

(a) The mask from steps 1, 2 and 3 is interposed between the object and the light sensitive emulsion as the exposure is carried out.

(1)) A blue filter is also interposed between the object and the light sensitive emulsion as the exposure is carried out.

(11) The exposed emulsion of step 10 is processed to produce a third separation negative for the production of a yellow color plate.

(12) Checking the correctness of density of the separation negative produced by steps 10 and 11 by comparing the densities of the renderings of the cyan area of the first separation negative and yellow area of the control member on the third separation negative and accepting the third separation negative if these densities are substantially equal.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed p 1 A method for controlling photographic color reproductions on a photosensitiied masking film with a control member consisting of afirst grey area of fixed photographic density and a second gi'ey area of a photographic density less than the density of said first" grey area, the steps comprising exposing the masking film to the image of the'object to be phoio rsphicsuy reproduced and to the image of the control member to form simultaneously on said masking filrn'a photographic image of the object to be photdgraphically reproducedand a photographic image of said control rrlerr'ilier, the time of expo sure of said film to said images being set to form an image on said film of the first grey area of said control member which, when saidfilm is developed, will give a developed image of said first grey area Within a predetermined density range, placing said exposed a developing solution to develop on said the photographic images of said object and said control element, fixing said developed film, said film being suitable for further use in photographic reproduction processes, if the image of the second grey area ofsaid control member has a density differential within a predetermined density range when compared with the density of the image of the first grey area.

2. In a method as recited in claim- 1, said density of the developed image of said first grey area being not substantially greater than 0.4 and riotsubs'tantially less than 0.2.

3. In a method as recited clairn 2, s'aid density differential between said second grey area andsaid first grey area being not substantially greater than 0.8" and not substantially less than 0.5.-

4'. A method for controlling the quality of lithographic color reproductions made by exposing separation negatives through first, second and third primary color filters and masking films to anoriginal colored image and to a control member consisting of a White area, a first grey area, a second grey area having a photographicdensity less than thede'n'sity of said'first grey area, and first, second and third color areas composed of colors complementary to those of the primary colors of the-color filters, Which comprises:

(I) exposing a photosensitized masking film to the original image of the object to be phot'og'raphically reproduced and to the control member to form simultanfeously on said-mask a photographic image of the object to be photographically reproduced and a photographic image of said control member;

(II) the time of exposure of said masking film to said images being set to form an image on said mask of the first grey area of said control member which, when said mask is developed, will give a developed image of said first grey area within a predetermined density range;

(III) developing said masking fihn to develop thereon the photographic images of said original and said control member;

(IV) measuring the density of the image of said first and second grey areas of said control member on said masking film, said masking film being acceptable for further use if the image of the second grey area of said control member has been developed to a density having a density differential within a predetermined range when compared with the density of the image of the first grey area;

(V) placing said masking film having thereon a photographic image of said control member between said original and a first separation panchromatic sensitized film and in register with said original,

(I) interposing a first primary color filter between said object and said first separation film, (2) exposing said separation film to said original through said mask and said first primary color filter to reproduce on said separation film an primary color filter with the rendering of the white area of said control member-on said first separation negative, 7

() said separation negative being suitable for;

further use if the difierence in density of these areas on the control member falls within a predetermined density range;

(VI) interposing a second primary colo-r filter between a second separation panchromatic sensitized film and the combination of said original and said masking film,

(1) exposing said second separation film to said original through said masking film and said second filter,

(2) developing said second separation film to produce a second separation negative,

(3) comparing the density of (a) the rendering of the color area (second color area) of said control member complementary in color to said second filter on said second separation negative with the density of the rendering of the first color area of said control member on said first separation negative and (b) the density of the white area of said control member on said first and second separation negatives, r

(4) said second separation negative being suitable for further use if the densities of said first and second color areas are about equal and also if the densities of said white areas are about equal;

(VII) interposing a third primary color filter between a third separation panchromatic sensitized film and the combination of said original and said masking film, p

(1) exposing said third separation film to said original through said masking film ands-aid third filter, g

(2) developing said third separation film to pro duce a third separation negative,

(3) comparing the density of (a) .the' rendering of the color area (third color area) of said control member complementary in color to said third filter on said third separation negative with the density of the rendering of the first color area of said control member on said first separation negative and (b) the density of the white area of said control member on said first and third separation negatives,

(4) said third separation negative being suitable (VIII) so that a balanced set of three separation nega-- tives are produced which are then suitable for use in production of lithographic plates from which high quality, multiple lithographic reproductionsof original colored images are obtained. I I 5. The method of claim 4 wherein the first separation film is exposed in such a way that it possesses a minimum density of 0.3 and a maximum density of 1.6 in the separation negative.

6. The method of claim 4 wherein the difference in density of the first color area and white area on said first separation negative is about 1.3.

7. In a method as recited in claim 4, said density of the developed image of said first grey area being not substantially greater than 0.4 and not substantially less than 0.2.

8. In a method as recited in claim 7, said density differential between said second grey area and said first gr'ey area'being not substantially greater than 0.8 and not substantially less than 0.5.

9. In a method as recited in claim 8, in which said masking film is exposed by reflection.

10. In a method as recited in claim 9, in which said masking film is exposed to a transparency.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Masking for Reflection Copy, Eastman Kodak Co.,

1957, Kodak Publication No. Q-5, pages 6-11.

Reprorama No. 10, International Bulletin for Graphic Information, Gevaert Photo-Producten N.W., Antwerp, Belgium (1959). p

Claims (1)

1. A METHOD FOR CONTROLLING PHOTOGRAPHIC COLOR REPRODUCTIONS ON A PHOTOSENSITIZED MASKING FILM WITH A CONTROL MEMBER CONSISTING OF A FIRST GREY AREA OF FIXED PHOTOGRAPHIC DENSITY AND A SECOND GREY AREA OF A PHOTOGRAPHIC DENSITY LESS THAN THE DENSITY OF SAID FIRST GREY AREA, THE STEPS COMPRISING EXPOSING THE MASKING FILM TO THE IMAGE OF THE OBJECT TO BE PHOTOGRAPHICALLY REPRODUCED AND TO THE IMAGE OF THE CONTROL MEMBER TO FORM SIMULTANEOUSLY ON SAID MASKING FILM A PHOTOGRAPHIC IMAGE OF THE OBJECT TO BE PHOTOGRAPHICALLY REPRODUCED AND A PHOTOGRAPHIC IMAGE OF SAID CONTROL MEMBER, THE TIME OF EXPOSURE OF SAID FILM TO SAID IMAGES BEING SET TO FORM AN IMAGE ON SAID FILM OF THE FIRST GREY AREA OF SAID CONTROL MEMBER WHICH, WHEN SAID FILM IS DEVELOPED, WILL GIVE A DEVELOPED IMAGE OF SAID FIRST GREY AREA WITHIN A PREDETERMINED DENSITY RANGE, PLACING SAID EXPOSED FILM IN A DEVELOPING SOLUTION TO DEVELOP ON SAID FILM THE PHOTOGRAPHIC IMAGES OF SAID OBJECT AND SAID CONTROL ELEMENT, FIXING SAID DEVELOPED FILM, SAID FILM BEING SUITABLE FOR FURTHER USE IN PHOTOGRAPHIC REPRODUCTION PROCESSES, IF THE IMAGE OF THE SECOND GREY AREA OF SAID CONTROL MEMBER HAS A DENSITY DIFFERENTIAL WITHIN A PREDETERMINED DENSITY RANGE WHEN COMPARED WITH THE DENSITY OF THE IMAGE OF THE FIRST GREY AREA.

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