US2207631A - Method of producing color selection pictures from multicolor master images - Google Patents

Description

Sea rch Ro July 9, 1940.

400 lxnlllllxllllLl wAvfLf/va rus /N VENTO/1 PAUL GoLDFINGER /lm ORNEY |||U|uunm un, efcn Jul! 9, 1940 P. GOLDFINGER 2.207.631

METHOD 0F PRODUCING COLOR SELECTION PICTURES FROM MULTICOLOR MASTER IMAGES Filed Aug 13, 1937 4 Sheets-Sheet 2 IUI /N VE N TOR 0-/ By 02d PAUL GOLDFINGER July 9, 1940- P. GoLDFlNGl-:R 2,207,631

METHOD 0F PRODUCING COLOR SELECTION PICTURES FROM MULTICOLGR MASTER IMAGES Filed Aug. 13, 1937 4 Sheets-Sheet I5 7.00 l 6.00 n 00 n au /Nz/ENTo/e PAUL GOLDF IN GER Search Room July 9, 1940- P. GOLDFINGER METHOD 0F PRODUCING COLOR SELECTION PICTURES FROM MULTICOLOR MASTER IMAGES Filed Aug. 13. 1937 4 Sheets-Sheet 4 By PAUL GLDFINGER Patented July 9, 1940 UNITED STATES search Room PATENT OFFICE METHOD OF PRODUCING COLOR SELECTION PICTURES FROM MULTICOLOR MASTER MAGES Application August 13, 1937, Serial No. 158,983 In Great Britain August 20, 1936 13 Claims.

It has heretofore been proposed to use subtractive multicolor photographic pictures as master images and to print the differently colored part images on to separate lms or directly on to a multilayer copying material.

In the processes heretofore proposed the individual printing lights have been chosen so as to be absorbed as strongly as possible by the dyestuii intended to form the part image to be l0 copied, and so that they exhibit considerable differences of absorption for the different superimposed partial pictures. For this purpose, filters having a transmission only in a narrow spectral region, or alternatively monochromatic light have 15 been used.

With this choice of printing lights the resulting copies are, in most cases, unsatisfactory, due to the fact that in addition to the desired copy of the part image which is intended to be printed,

there are also printed unwanted copies of those part images which are not intended to be printed. These images are superimposed on the required image. Such unwanted and deleterious printing effects are often of such a magnitude as to render accurate color reproduction impossible.

The chief object of the present invention is to overcome this disadvantage and to provide means whereby the undesirable printing effects of the part images which are associated with the part image to be printed are reduced to such an extent that they will not interfere with accurate color reproduction, or even to such an extent that they disappear entirely for all practical purposes.

According to the principal feature of the present invention for the purpose of successively and/or simultaneously printing the differently colored part images from a multicolor image on to separate or superimposed printing layers, the

light used for printing the single part images has a wavelength or wavelength interval at which the ratio of the absorptions of the dyestuft' forming the part image to be copied and the dyestui or dyestuis forming the part image or images of which a copy is not required, is a maximum; or

as near a maximum as is consistent with practical considerations. The printing light is thus chosen independently of the absolute absorption maximum or maximum absorption difference of the dyestuffs in question.

It will be understood that these considerations apply equally well to images formed by a plurality of superimposed part images in diierent layers or strata of emulsion as to images formed in one single layer. For the sake of simplicity it may be assumed that each part image of the subtractive multicolor image is produced in a separate part layer.

For subtractive color reproduction it is essential that dyestuffs should be used each of which 5 absorbs light in a distinct wavelength interval whilst at the same time transmitting light of another wavelength. The dyestuffs which have heretofore been proposed, however, are far from having these properties desired from a theoretical 10 standpoint. The absorption curves overlap each other to a remarkable extent. It is one of the objects of the present invention to overcome the diiiiculties arising from such overlapping. It is true that in the case Where the dyestuff absorpl5 tions do not overlap printing with light of the wavelength for which each of the dyestuffs possesses maximum absorption would be feasible, but as a matter of fact the absorption of the dyestuffs which have heretofore been proposed in 20 such a concentration as is necessary for the production of a satisfactory colored image overlap each other to such an extent that it will be necessary to print with a printing light according to the present invention as hereinafter defined in 25 order to eliminate the undesired printing eiect resulting from the overlapping absorption of the dyes.

Where three-color images are to be printed the printing light for the individual layers is, in ac- 30 cordance with the present invention, preferably individually so chosen that its wavelength is that at which the lesser of the two ratios of the absorption of the dyestu in the layer of which the copy is required and the dyestuffs in the layers 35 of which a copy is unwanted has a maximum value.

It will, of course, be obvious that the dyestuffs of the different partial layers must exhibit considerable differences of absorption for the print- 40 ing light and, therefore, that the amount of printing light absorbed by the dyestuff in the layer of which the copy is desired should be as large as possible compared v ith the amount of the printing light absorbed by the other dyestuis. 45

It has been found, however, that, in practice, the ratio of the absorptions is of equal if not greater importance than the ratio of the transmitted light, i. e., the dilerence of the absorptions and accordingly, in carrying out the pres 50 ent invention, the wavelength of the printing light is so chosen that the ratio of the absorptions is sufficiently great.

It is a remarkable fact, that the wavelengths for which the difference of the absorptions has 55 a maximum value is often not the same as the wavelength at which the ratio of the absorptions is a maximum. For the sake of simplicity there will iirst be described the advantages which are obtained if the printing light is chosen with regard to the maximum of the ratio of the absorptions, Subsequently it will be shown in what manner the choice of this printing light and the requirement of suiiicient great difference of the absorptions can simultaneously be fulfilled.

It will be apparent that the printing light according to the present invention is chosen without regard to the maximum of the absorption itself. The present invention enables printing to be performed with light having a wavelength which is not the same as the wavelength at which the absorption of the dyestutf in the layer to be printed is a maximum, provided the ratio of the various absorptions for this light possesses a sufficiently large value.

In order that the nature of this invention may be more clearly understood reference may be made to the accompanying drawings, in which:

Figure 1 shows the absorption curves of two dyestuffs,

Figure 2 shows the difference of the absorptions shown in Figure 1 and Figure 3 shows the ratio of the absorptions of the same dyestuffs Figure 4 shows the absorption curves of three diierent dyestuffs the absorption being shown for two different concentrations of each dyestuff, i. e., b, B; m, M; and y, Y.

In Figure 5 there is shown (a) a master image employing the dyestuifs of Figure 4 in the form of a color chart and comprising a plurality of color scales, the most intensely colored field having the dyestui density represented by the curves B, M, Y of Figure 4 (b) represents the density distribution of the master image for the printing light used in printing the yellow part image (c) represents the density distribution of the master image for the printing light used in printing the magenta part image (d) represents the density distribution of the master image for the printing light used in printing the blue-green part image (e) represents the density of the silver image in one of the three-color selection prints and (f) represents the corresponding positive, (e) being assumed to be a negative.

Figure 6 is a series of graphs illustrating the relation between the ratio of the gamma-values to which the color selection prints are to be developed and the values of the unwanted prints thus produced Figure 7 shows the absorption curves of three dyestuis different from those shown in Figure 4 and the sum of their absorption Figure 8 represents the absorption curves of the same dyestuffs if used in different concentrations and the sum of these absorptions Figure 9 shows the ratios of the absorptions given in Figure 7 Figure 10 shows the ratio of the absorptions given in Figure 8 Figure 11 shows the absorption curves of three further dyestuis.

Referring now to the drawings, the two dyestuffs, the absorption curves of which are shown in Figure 1 are Patent Blue A (Schultz Farbstofftabellen, 7th ed. 1931, No. 826) and Filter Blue I (Huebl, Die Lichtfilter, 1921, Halle/Saale, 2nd ed., annex Ic) these being blue or bluishgreen dyestuii's which are very similar for the human eye, and the absorption curves of which overlap as shown.

In Figure 2 the curves show the difference between the absorptions of these two dyestuis and it will be seen that the maximum differences of the absorptions nearly coincide with the absorption maxima of the dyestuii's themselves.

On the other hand, as shown in Figure 3, it will be seen that the maxima of the ratio of the absorptions are not at all coincident with the absorption maxima. The greatest values of the absorption ratios are situated about 500ML and 655ML, whereas the absorption maxima (see Figure 1) are situated at about 570ml and 645W. and the maximum dierences (see Figure 2) are situated at about 565ml and 645ML.

In carrying out the present invention, therefore, the printing light is chosen in a region which is as near as possible to the maximum of the absorption ratios. In the example described above, one of the dyestuff images would be printed with light of a wavelength of 670ml and the other with a light of a wavelength of 508ML.

As sources of the printing light there are used monochromatic lamps preferably arcs or sparks, discharges in raried gases or lamps in which atomic line spectra are excited by heat, thermal electron emission or optically, as in the known resonance lamps. Lamps lled with easily vaporizable metals such, for instance, as metals of the rst and second` group of the periodic system of elements are especially useful. There may also be used lamps which emit continuous or band spectra but in this case, lters must be used which transmit only narrow spectral regions.

Frequently the usual sources of monochromatic light are of insufficient intensity, particularly for the printing of cinematograph films where the time of exposure is limited. In these cases therefore it is preferable to use discharge tubes with a relatively high current density. The illumination is, except in the case of resonance lines, performed end on," i. e., so that the radiation of the length of the whole discharge tube will be effective. Preferably these tubes are included in a vacuum jacket and the whole may, furthermore. be immersed in a cooling bath of circulating water.

Since these radiation sources naturally emit several atomic lines, filters are preferably used. The usual filter iilms are frequently satisfactory but sometimes, however, it is simpler to use liquid lters in which case the liquid forming the lter may be used as the cooling liquid, the ilter liquid circulating in a closed circle between a cooling vessel and the lamp.

The following examplesr illustrate the present invention.

Example 1.-A master image comprising two different blue part images dyed with Filter Blue and Patent Blue respectively is to be printed. In Figure 1 the optical densities of the dyestuis (Filter Blue in the maximum concentration of 0.8 g. per sq. m. and Patent Blue in a maximum concentration of 0.44 g. per sq. m.) are plotted against the wavelength. In the two partial pictures, of course, the dyestuif concentration varies locally from zero in the highlights to the maximum given above in the shadows.

The partial picture formed by Filter Blue is printed by the use of a cadmium lamp behind a. Wratten light filter No. 61 on to a blue sensitive printing material, the sensitivity of which extends up to about 520W. The intensity and duration, or more generally the quantity of light, is so chosen that at the points where the master image is uncolored, a silver deposit of a density 2 is obtained on the printing material when developed to 'y 2.2. At this gamma value the printing material shows the partial picture which corresponds to the image formed by Filter Blue with a maximum density of 2, whereas the partial picture formed by Patent Blue absorbs the light rays of the cadmium lamp to such a negligible extent that, at the points of maximum dyestuif concentration, a maximum silver deposit of a density of only 0.3 is caused. If printing were performed by printing light of the wavelength at which 'the dyestuif Filter Blue has its maximum absorption the presence of the other dyestuff would result in a maximum silver deposit of a density of 0.9 at the points of maximum dyestuff concentration.

The other partial picture is printed by the light from an electrical discharge in lithium vapour with the aid of a Wratten light filter No. 89 or 70 or, preferably, with the aid of the red glass F 4512 (supplied by Schott and Gen., Jena). The printing material is a panchromatic iilm and the light duration and intensity are regulated so as to obtain, after a development to gamma 0.65 a maximum density 2 of the silver image. The maximum density of silver due to the other partial picture in this case also is only 0.1.

The same master image may also be printed with other monochromatic light sources, for example, instead of the red lithium line, the red helium line may be used this being obtained from the known helium discharge tubes behind the above-mentioned red lters, if it be desired to use other wave lengths, e. g., the mercury line 491.6 or the hydrogen line 656 it is advantageous to change the dyestui concentrations in the master image. By the use of the red hydrogen line and the green cadmium line very good results, i. e., disturbing effects smaller than 0.2 may be obtained if the maximum dyestui concentration of Filter Blue be increased to 1.0 g. per sq. m. and that of the Patent Blue lowered to 0.2 g. per sq. m., and if both prints are developed to ^,1=1. The variation of the dyestui concentrations is effected for the purpose of adapting the absorption values and the absorption ratio to the altered printing lights and further for the purpose of avoiding extreme development conditions.

'I'his will be more fully described hereinafter. Heretofore multicolor master images have usually comprised images in the exact colors to be reproduced and could be used for direct viewing or for projection. Multicolor master images have, however, been proposed in which the individual partial color records are diierent from the natural colors, these being obtained by transposing the colors of the diierent partial images. In all cases, however, the intensity scale of the different part images remains the same, i. e., the image of a grey scale in the master image is formed by three colored partial pictures which combine together to form a grey scale which is of the same or opposite sign to the original grey scale.

A master image, however, which may be used in performing the printing process described above, may be obtained by departing from the equivalence of the colored partial pictures. In master images of this kind a grey scale would also appear in the form of three colored partial pictures which, however, do not together result in UGCU LH a grey scale, but in a scale in which, for instance, the yellow color is preponderant.

'I'he darkest black in this scale is, therefore, for example, a blackish yellow or brown. When master images of this kind are produced photographically, pictures which are not suitable for direct viewing are thus purposely produced but, on the other hand, one obtains the advantage that such master images yield prints which correspond much more exactly to the object than prints which are obtained from multicolor images which may be used for direct viewing.

The advantages of such master images and the method of using them may be more readily appreciated on reference to the following description and the accompanying drawings, it being clearly understood that this description and the drawings are given merely by way of example and are not to be taken as in any way hunting the scope of the present invention.

In the accompanying drawings, there is shown in Figure 4 the absorption curves of three diierent dyestus (greenish-blue, magenta and yellow). The curves b, m and 1/ represent the absorption of the respective dyestuis if the dyestuis were used in such concentration that a. grey scale object is reproduced as a grey scale (the known arrangement), whereas the curves B, M and Y represent the absorption of the same dyestuis in a master image formed by dyestuffs of unbalanced concentration according to the invention. In this rlgure the transparency of the dyestus, in the concentrations b, m and y and. B, M and Y are plotted against the wavelength inversely and logarithmically (on the base 10). It can be seen that the bluish-green dyestui is not completely transparent in the region of the absorption of the magenta dyestui. In fact, the absorptions overlap considerably. The bluishgreen dyestuif shows also a considerable overlap with the absorption of the yellow dyestuii, particularly in the region of the invisible light below 400g/.1. and down to the limit of absorption of glass. The yellow dyestuff also is not completely transparent in the region of absorption of the magenta dyestuif. The yellow dyestufi in the master image is employed in a considerably excess concentration so as to make the multicolor image appear in unnatural colors. A point in the master image at which yellow, greenish-blue and magenta dyestuis are superimposed does not appear grey, but of a brownish shade. In a similar manner all mixed colors in which the yellow dyestuff appears are very yellowish.

Of the dyestuiis which form the multicolor image illustrated in Figure 4, the bluish-green dyestuff is Patent Blue A (Schultz Farbstofftabellen, 7th ed. 1931, No. 826) and has a maximum concentration of 0.1 g. per sq. m.

The term maximum dyestui concentration is used in this specication to indicate the difierence of the dyestuff concentrations at the lightest and darkest points of the image, even where the lightest parts might be intensely colored and the expressions lightest point and darkest point are intended to imply, comparatively, the maximum light interval which can be registered by the material and not the fortuitous light interval of a certain object for which this interval may well be small. Furthermore, it may be borne in mind that, in general, dyestuii" concentration and optical density are proportional to each other. Therefore, the term concentration may be understood to be a measure of the optical density in these cases, whereas in cases in ilUUH which there is no proportionality it is the optical density which counts.

The magenta dyestuii present in the multicolor image illustrated in Figure 4 is Fast Red D (loc. cit. No. 212) and has a concentration of 0.40 g. per sq. rn. The yellow image, however, at the points at which the dyestuff is present in its maximum concentration contains 20 times as much dyestuff as the layer contains blue dyestui. The yellow dyestuff is conveniently Filter Yellow K (loc. cit. No. 737) and is present at the points of highest intensity in a concentration of 2.0 g. per sq. m. The absorption curves b, m, y corresponding to the concentrations which are necessary to form pictures with normal color values and a normal scale of grey will be obtained with about 0.25 g. per sq. m of blue, about 0.9 g. per sq. m. magenta and about 1.3 g. per sq. m. yellow dyestui. The effect of this deviation from the normal balance of concentrations of the dyestuffs may be seen in Figure 4.

Overlapping absorptions as shown in Figures 4, 7, 8 and 11 are frequent and in the printing process they cause considerable diiculties because the printing light, when absorbed by two dyestuffs is unable to yield a selective print represented by each of the dyestuifs alone. In addition to the partial image which it is intended to print and which may be termed the "regular image, others will also be printed owing to the overlapping absorptions and will yield irregular prints of considerable intensity. This undesired printing effect can be avoided by a deviation from the normal balance of dyestuif concentrations. Thus, the concentration of, say, the yellow dyestuf may be increased considerably above, and the concentration of the two other dyestuifs may be decreased far below, the value necessary for exact color representation and for the formation of a substantial grey, thus giving color-distorted images. In other' words, the summation of the absorptions produces a curve having an average positive slope toward the blue end of the spectrum and the appearance of the combined dyesturfs is brownish due to the predominate yellow. The overlapping of the absorptions is thereby practically eliminated, since the absorption of the yellow dyestui is increased and at the same time that of the bluish-green and magenta is considerably decreased. Such a master image yields prints of the single color-selection pictures in which the other color-selection pictures appear with a much less disturbing irregular image than in those prints which are obtained under the same conditions from master images with balanced color intensities.

If multicolor images composed of three differently colored dyestui images are employed, obviously three different printing lights are required. The printing light for the first desired print then, generally, results in undesired printing effects of the two other dyestuff part images, and in order to keep these undesired effects as low as possible not only t .e ratio but also the ratio fi A3' must be considered when choosing the printing light for the rst dyestu image. In this formula A is the absorption, i. e., the product of absorption coeicient and concentration, the lower exponents indicating the dyestus and the upper exponents indicating the wavelengths or intervals of wavelengths. Thus, for example, the ratio is the ratio of absorption of first dyestui in the rst printing light to the absorption of the second dyestuf in same printing light. In the same Way the wavelength of the second printing light is chosen having due regard to the ratio and and the third printing light is chosen according to the ratios A1" and Ag" Tg Whereas with two part images it would be possible to bring the printing light into exact coincidence with the maximum of the absorption ratio, in the case of a three color master image the printing light cannot be simultaneously in coincidence with the maximum of the diierent ratios. Therefore, according to the invention, when printing a three color image, there are chosen as printing lights for each part image such wavelengths as coincide, or nearly coincide, with that wavelength at which the smaller absorption ratio of the two ratios has its maximum value. rIhis is frequently the case with light of the wavelength, corresponding to the intersection point of the curves of absorption ratios plotted against the wavelength of Figures 9, 10.

The yellow dyestuT-image may be printed, for example, with mercury light of the wavelength 405ML or potassium light of the wavelength 404.6 to 404.7,u/.r- The amount of yellow dyestuff being purposely increased according to the present invention above the quantity necessary for correct rendering of colors, it is possible to print in a region in which the absorption of the yellow dyestui is not a maximum and in which at the same time due to the decrease of their concentration the absorptions of the blue-green and magenta dyestuifs are diminished to a negligible quantity.

The other two images are printed with lights between the wavelengths of about 510 and 540ml for the magenta image, e. g., with cadmium light of wavelength 508 or thallium light of the wavelength 535Ml, with light between the wavelengths of about 610 to 640ML for the bluish-green image, i. e., for example, the red lithium line at 610.4 or the cadmium line at 643.8p/r.

At the wavelengths given above, the two dyestuii pictures which it is not desired to print show such small absorptions in comparison with the dyestuii of the part image which it is desired to print that even at those points of the image where the dyestuffs are present in maximum concentration they will be nearly as transparent as the colorless parts of the image.

In Figure 5 oi' the accompanying drawings, in the first -horizontal line (a) there is illustrated diagrammatically a three-color photographic picture in which a yellow, a magenta and a. bluish-green and a grey scale are on a white background. In (b), (c) and (d) of this gure the density of this picture is shown for three different printing lights. These printing lights are of the wavelengths 405W (b) 508ML (c) and 610ML (d). On thenext horizontal line (e), as an example, there is represented the negative silver image which results from printing with light oi the mercury line 405ML and developing the print thus obtained to y=0.55 (the light intensity being chosen so that a maximum density Dmex=2 is obtained). In the last horizontal line there is represented the positive silver image which is obtained from the negative silver image (e), by printing and developing to 7:1.

It will be clear that the desired density of the final print chosen in this and in the following examples Dmax.p.=2 for the positive silver image, may be obtained also in another manner by developing, e. g., the negative partial picture to a. higher and the positive to a lower gamma value as is well known in the art. If the maximum density of the tricolor picture in the printing light be Dm, and if the gamma value of the partial picture obtained from this be yn, and the gamma value of the positive copy be vp, then the condition is Dmfypfyn=Dmax-p- If an extreme change of the density of the partial picture in the printing light is necessary to obtain the required density of the partial print, this can be eiiected to comply with the above equation by printing several times. Of course, this is limited by the fact, that it is only possible to use that part of the gamma curve which is substantially linear. By using the silver halide emulsions now available for the intermediate prints, it is not diiiicult to multiply the ratio of the densities by 10 or even 20 by printing twice. In each case in which by intermediate printing steps negative prints are obtained instead of positive, or vice versa, they may be printed or reversed to yield the corresponding positive or negative.

Pictures with high dyestuif concentrations show in the printing light used in printing them a high contrast, whereas, on the contrary, pictures with a low dyestuff concentration have transparencies in the corresponding printing light like pictures of low contrast. Therefore, the lower the absorption at the image points of maximum dyestuff concentration of the partial picture which is to be printed the higher is the gamma value to which the prints are developed.

The methods by which an image may be printed according to the present invention will now be described.

Example 2.-A master image is employed formed by three partial pictures in the colors illustrated by Figure 4 in concentrations corresponding to the curves B, M, Y.

The bluish-green colored partial picture is printed with the light of a discharge in lithium vapour on printing material which is sensitized by pinachrome or thiazol purple. The lithium lamp emits two lines of considerable intensity, one at 610.4pa and the other at 670.8;m. The printing material used is only sensitive to the former of these two lines and it is only this light which prints the bluish-green part picture. The black and white print is developed to 7:1.7 and .Search copied again and the second print again developed to the same gamma. This will be a positive, if the master image is a positive.

The yellow colored partial picture in the master image is printed on printing material not specially sensitized, with the light of the mercury vapour lamp screened by a Wratten light filter 18A. This filter transmits only the lines 365 to 366ML. The print is developed to 7:0.55 and may if desired be printed a second time to give a positive.

The partial picture which has a magenta color is printed on printing material which is sensitive up to 550W. A discharge in thallium vapour is used which furnishes the green line at 535ML. The print is developed to -/=2.2 and may be printed again to give a positive. Three prints are produced in this way, which all have a maximum density of 2 and in which the undesired irregular partial pictures have maximum densities which are not greater than the ordinary veil. By veil is meant the uniform darkening of the unexposed material if developed and fixed. The print of the blue-green partial picture contains also an image of the magenta partial picture but this additional image only has a maximum density of 0.1'7. The print of the yellow partial picture contains also an image of the blue partial picture, the maximum density of which is, however, only 0.04 and in addition an image of the magenta partial picture the maximum density of this irregular image being only 0.11. The print of the magenta partial picture contains an image of the blue partial picture with a maximum density of 0.12 and the yellow partial picture is imperceptible.

The method of production above indicated may, of course, be varied, e. g., the blue partial picture may be printed with the light of the red cadmium line 643.8Mr, a red glass F 4512 being used as filter with a thickness of 1.1 mm., the printing being performed on a lm sensitized with pinachrome violet or pantochrome. The print is developed in this case to A/=1.4 the blue partial picture then appearing alone.

The magenta partial picture may also be printed with the light of a cadmium lamp furnishing the spectral line 508ML, printing being performed on a film comprising an emulsion not specially sensitized and sensitive to wavelengths up to about S20/ra. As a filter a Wratten lter No. 61 is used. This print of the magenta partial picture is developed to y=2.3 and is produced with a density of 2.0 the print of the blue partial plcture appearing therein only with a density of 0.02 and that of the yellow partial picture only with a density of 0.11.

The yellow image may be printed in the light of the mercury lamp with the C. P. Goertz light filter No. 405, or with a filter which contains, in 100 c. c. 96% alcohol, 0.03 g. fuchsine (Schultz loc. cit. No. '780) and 4 g. quinine hydrochloride. The intensity of the printing light used is such that it gives a maximum density of 2 for the print when developed to 'y=O.55. The irregular print of the blue image then has a density of 0.07 and that of the magenta image a density of 0.08.

Example 3.-The master image of the preceding example may also be printed directly on to three-layer material. If the bluish-green colored partial picture corresponds to the blue colorselection picture, the yellow picture to the green color-selection and the magenta to the red colorselection, an image in natural colors can be obtained immediately in the following manner. A

printing material is used which contains as dyestuff Chicago blue, (Schultz loc. cit. No. 510), Chrysophenine (Schultz loc. cit. No. 726) and Diamine Fast Pink in concentrations which correspond to an exact balancing of the colors against each other. The magenta layer is poured on the support, an emulsion not specially sensitized being used as in the first example, the concentration of the dyestuff being 0.7 g. per sq. m. Over this layer is poured a layer of hardened gelatine which decreases the rate of diffusion of the developer and on this layer is coated an emulsion sensitized by pinacyanol blue and dyed with 0.7 g. of yellow dyestui per sq. m. On this is poured an emulsion which is sensitive to wavelengths up to 550ML and dyed with 0.5 g. per sq. m. of blue dyestuff.

The red color selection picture which is registered in the form of a magenta image in the master image is printed in the blue-green layer of the printing material with the light of the green thallium line. The yellow layer, sensitized with pinacyanol blue, lying behind this layer is not sensitive to light of this wavelength and may also, if desired, be screened by means of a lter dyestui which can be easily washed out. Printing is performed in the other two layers from the other side of the material, that is through the support, with mercury light of a wavelength equal to 405ML and the cadmium line at 643.8;m. The lm is developed to y=2.1 in the uppermost layer, a rapid developer formed by metol and potash being used. The gamma value of the following layer is then, as required, about 1.4 whereas in the undermost layer the developer diiuses only slowly through the hardened gelatine so that a gamma value of only 0.55 is reached. For the purpose of more easily controlling the diierent gamma values, it is advantageous to print in addition to the image, e. g., in the sound track (if this is free), a scale of light intensities in blue, green and red light, as is shown, for example, in Figure 5a. The film is then developed, xed and Washed, and the silver images are transformed into dyestui images in a known manner, for example, in a bath of 3.5% thiocarbamide and 2% citric acid. In this way, a positive tricolor picture in natural colors is obtained immediately from the unnaturally colored positive master image.

Example 4.--For photographing, a material is used comprising three layers, the uppermost layer being sensitive to red and uncolored, the second layer sensitized for green and containing 1 g. of chrysophenine per sq. m. The layer poured on the support is not specially sensitized, i. e., is blue sensitive.

The material is exposed through the support. Then after developing and xing, the uppermost layer is dyed with Fast Red D until the concentration of 0.6 g. per sq. m. is obtained, i. e., a density of 1.3 in light of the wavelength of the green cadmium line. The silver images of the two uppermost layers are transformed into dyestuff images by a bath of 2% thiourea and 1% hydrochloric acid. For the transformation of the silver images into dyestui images a bath of 4% potassium iodide and 1% hydrochloric acid can also be used with advantage. The silver in the layer which is immediately on the support is then transformed by potassium ferri-cyanide into silver ferro-cyanide which is treated by an acid solution of iron sulphate, and gives Prussian blue of a maximum density of 1.5 in light of the wavelength of the red potassium lines 691.1 and 693.9Mr or the red caesium lines 697.5 and 698.3/i/i.

It is of special advantage in this photographing material to print before developing the intensity scale corresponding to each partial color picture mentioned in Example 2. The Prussian blue picture having been produced, the 111m is iixed, I

dried and printed. As printing light for the blue partial picture which in contrast to the others is a negative, a discharge in potassium or caesium vapour and a printing material which is sensitized with pinacyanol blue are used. This partial picture is developed to 'y=1.3 to 1.4. The magenta colored red partial picture is printed in the light of the cadmium lamp at 50B/ra and developed to 7:15. The yellow colored green partial picture is printed with light of the mercury line 405ML and developed to 'y=0.65.

For the sake of simplicity, in the preceding examples silver partial pictures were produced in printing which all have the same density of 2. In most cases this arrangement will be satisfactory but it may in certain cases be necessary to depart from these conditions. The partial picture prints produced serve for the production of multicolor images and it is important that the colors of these usually tricolor pictures which serve for viewing or projection show an exact ratio of gradations, i. e., a grey scale must show the exact gradation. If silver images of different densities and gradations are required so as to produce colored partial pictures which supplement each other in this way, it is necessary according to the present invention to depart from equal densities of the single partial pictures as given above. This will be readily appreciated from the equations given below. For the production of master images, especially where the dyestuff in silver images is destroyed at the points of the silver image, it is frequently necessary to use emulsions which, when simultaneously developed, give dierent gamma values, because in layers in which there is present a dyestuif which is rapidly destroyed in the presence of silver images a low contrast is desired, whereas in layers in which a slowly bleaching dyestui is present, a high contrast is desired.

A further feature of the present invention consists in using the printing light to influence, instead of photographic layers which give the partial picture, photo-electric instruments such, for example, as photo-electric cells, bolometers, etc., and in transforming the light impulses thus produced into electric current impulses. This electric current can be recorded on instruments such as oscillographs and the like or can be used for teletransmission. In this case it is useful to scan the surface of the image by a light beam of the printing light, or in the vcase of uniform illumination of the surface of the image to scan it in the known manner by the photo-electric instrument. The current impulses thus obtained are then amplified in a known manner and retransformed into light after transmission. This light can be used for direct projection or for acting upon light sensitive materials. These serve for the production of multicolor photographic images or as printing matrices for multicolor prints.

In the preceding examples the most important features of the present invention have been described. It is, however, also possible without departing from the scope of the present invention to use other dyestuffs and/or other concentrations. 'Ihe manner in which the master images are obtained is of no importance. They may be obtained by dyestuff destruction or dyestuff formation at the image or non-image parts of photographic silver images, or by mordanting or imbibition processes, or by color development or other known methods.

Other light sources, emitting printing light of a wavelength which is different from that given above'can be used including ultra-violet or infrared light. It will be apparent from the foregoing examples that the choice of the concentrations for given wavelengths, i. e., for the given ratio of absorption coefficients is of fundamental importance and the manner in which such optimum concentrations can be readily calculated will now be described.

Assume that a colored master image contains a dyestui I in the form of an image and that its absorption coecient for different wavelengths A', A, N", etc., is

k1', k'l', etc.,

Intensmm.. o lntensmim logi k; being the absorption coeicient for the wavelength k, (or the average absorption coeilicient for the wavelength interval) expressed for logarithms on the base of 10 in sq. ms. per gram, the concentration being given in grams per sq. m. When the above-mentioned image is printed with light of the wavelength A', the print being developed to ^y=1, an image will be obtained, the maximum diierence in density of which is given by the right hand side of the above equation, provided of course that the image lies on the 1inear part of the gradation curve. For a gamma Value y other than 1, the maximum density difference D1' (density difference in print produced by printing dyestuff I by printing light N) is given by D1I=7Iki01 (la) kh, kn, etc.

be not zero. If the maximum density diierences of .these irregular images at the wavelength A' are dil, dill their values are given by In: 'Ylkiucm In a similar manner the maximum densities (or more exactly the maximum density differences) in the regular and irregular images of the dyestuis 11, 111, etc., at the different wavelengths are given by In these equations the maximum density differences of the regular partial prints DI', Dit, D'r, etc.

must correspond to the maximum ratio of light intensity (emitted or reflected) at the lightest and darkest points to be registered of the object. All the regular partial prints, however, are falsified by irregular partial pictures because in reality the absorption coecient of none of the dyestufs which are practically employed equals zero at any point within the spectral range in which photographic prints can be made. The desired single color selection prints are the more exact the fainter the undesired irregular images therein. The formulas show that for given dyestuil's and for given printing lights (i. e., given k-values), the concentration must be the smallest for those dyestuffs which have the most appreciable absorption coeflicient in the printing light in which it is intended to print a dierent dyestui. By this means, however, not only is the disturbing absorption decreased but also the absorption of this part image for its own printing light is reduced. Consequently in order to avoid at prints these images are developed to a relatively large gamma value.

On the other hand the ratio between the densities of the regular and irregular partial pictures in the print can also be improved by increasing the concentration of those dyestuffs which are printed by light which is absorbed to a considerable extent by the other dyestuis. Thus the regular partial picture obtains a high density diierence which can be brought down to the normal value by the choice of a low gamma in developing its print. Thereby the density difference in the undesired irregular partial pictures is decreased.

The optimum dyestuff concentrations necessary to obtain the best results can be determined quantitatively in the following way. Resolve the Equations la to 3c for the ratio of the gamma The optimum conditions can be determined from these equations analytically or in a more convenient manner geometrically. In Figure 6 the ratios are plotted against di', dir, d", dhr, etc.

the'maximum density of the regular partial pictures Di, Dit Di being chosen for the sake of simplicity as equal 2 and the k-values being those of the dyestuffs shown in Figure 4 for the printing lights '=4o5, "=508,i, and l"'=61 o.4,..

Equations 4a, 5a and 6a are represented by straight lines which pass through the origin, whereas the Equations 4b, 5b and 6b are represented by rectangular hyperbolas of which 5bcorresponding to the irregular print of the yellow dyestuff in the printing light used for printing the blue-green image-coincides with the co-ordinate axes because the absorption coefcient k2" of the yellow dyestuft at 610W. is practically equal to zero.

4a. and also 5a are straight lines inclined at a small angle to the abscissa which represents the density of the irregular images. This means that in order to keep these undesired images as small as possible it is necessary to choose very small ratios l l g77 and $7, so that 'y' and y" and also 'y' and 7" must be of very different magnitude.

Now the free choice of the gamma value is restricted by photographic considerations. As a matter of fact it would be impossible to choose two gamma values the ratio of which is for example 11100. If, for example, it is practically necessary to restrict oneself to the use of gamma values between about 0.7 and 2.3 only, gamma ratios between the limits .S-OB and can be selected. It is, however, possible to use gamma values of greater divergence and therefore gamma ratios which surpass these limits.

The straight line 4a and the hyperbola 4b, representing the inuence of the gamma ratio on the irregular images dit and d' respectively, in Figure 6, show that both these irregular images are equal to each other for corresponding to the intersection of 4a and 4b.

There may, therefore, be selected the gamma to which the print obtained by the blue light is developed y=0.6 or 0.8 and correspondingly the gamma to which the print obtained by green light is developed y"=2.1 or 2.8 respectively, the ratio being 0.29 in both cases.

Having chosen T one is still at liberty to choose either any desired ratio or any desired ratio ,yll

lll

,yl gm for example is selected the value of .Y will be determined by the relation 1 v WIF'TITQT-= These correlated values can be represented geometrically by the straight line OX, the ordinates of which are 3.45 times as great as the ordinates of 5a for the same abscissa. For each abscissa the ordinate of 5a gives a value of ratio and a ratio for which the irregular images determined by the two curves 5a and 6b will be equal to each other.

'I'hus by initially selecting any one of the gamma ratios, say

,yl 777', a relative optimum can be found.

'y is not changed, mere exists no other ratio Indeed, if

and no other ratio than those dened by the intersection of OX and hyperbola 6b which would not cause at least one of the largest irregular images to exercise a still more disturbing effect on the required image.

This relative optimum condition is character- -vvulu 11|,

Search Room di'i (curve 6b) and d'm (line 5a) and thus to improve the quality of the color selection prints. Here again an optimum can be found. This may be calculated arithmetically or also geometrically as follows: For this purpose the value of the ordinate of 5a is divided by the value of the ordinate o1' 4b for every value of the abscissa and the ratios thus obtained are plotted against the abscissa. There is thus obtained a parabola OY each ordinate of which gives the ratio of l l l/ (and therefore also of 7- ,y ,yl/l for which the irregular images d and dh, are equal to each other. The irregular images are simultaneously equal to I dit 1f ,YT/ is chosen at the intersection of curves OY and 6b. This means that the three irregular images defined by the curves 6b, 4b and 5a will be equal if all the prints are developed to gamma values the ratio of which is and to equal maximum densities. These conditions are s'atised, for example, by the following gamma values: 'y'=0.5 y"=2.1 'y= 1.66 or by gamma values in the same proportion.

From the gamma values thus selected the dyestuff concentrations necessary to build up the master image can be determined by the use of Equations la, 2a and 3a. Thus there is obtained, for example, c1=2.28 grams per sq. m. c2=0.434 gram per sq. m. c3=0.177 gram per sq. rn., or other concentrations in the same proportion. It is, of course, unnecessary to use dyestuii concentrations of the exact value obtained from these equations. Even if departing by about 10% from the concentrations thus calculated the irregular prints are not materially increased.

Example 5.-A master image in which the yellow dyed part image has a maximum concentration of 2.3 grams per sq. m. of Filter Yellow, the magenta dyed part image a maximum concentration of 0.43 gram per sq. m. of Fast Red D and the blue-green dyed part image a concentration of 0.18 gram per sq. m. of Patent Blue is printed in succession on to three different printing layers by light of the wavelengths 405, 508 and 610ml as described in the preceding examples. The first print is developed to Iy--0.5; the second print to y=2.1 and the third print to y=1.66. Three part images are thus obtained having a. maximum density of 2 and in all of which the largest irregular image has the same maximum density of 0.11. In two of the prints there is, further, one irregular image of minor importance.

In the following it will be shown that even in the case of dyestuifs with extremely flat absorption curves such, for example, as most of the azo dyestuffs, very satisfactory results can be obtained with the method according to the present invention which results could not be obtained heretofore.

In Figure '7 the absorption curves of three azo dyestuffs are given l. Diamingelb CP (Schultz Farbstotabellen, 7th ed. 1931, No. 726.)

2. Sirius Ruby B (Ullmann, Enzyklopaedie der technischen Chemie, 2nd ed. 1932, vol. 9, page 524).

3. Benzo Pure Blue Schultz Farbstotabellen. 7th ed. 1931, No. 513).

The curve S gives the sum of the absorptions of these three dyestuifs which practically show a grey color for the densities represented in Figure '7. If printing is performed in the maximum of the absorption so as to obtain regular prints of the maximum density 2 the following result is obtained:

Figure 9 gives the ratios of the absorptions of these dyestuffs in the concentrations given in Figure 7. If printing is performed in the maximum of the ratios the results are thereby considerably improved.

Density of the print for the wavelengths Print of the- 508.6 518 671 nu (Cd (M8) (Ll) Yellow image 0. 5 0. 3 0. 1 Magenta image... 2. 0 2. 0 0. 18 Blue-green image 0.67 0.8 2. 0

A further improvement is obtained by calculating the necessary variation of the concentration as described above in connection with Figure 6. In this case the corresponding absorption curves are represented in Figure 8 and the ratio of the l absorptions in Figure 10 and the results are the The sum of the absorptions as given in Figure 8 shows an increased transparency towards the Density of the print for the wavelengths Print of the- 405 508.61m. 643.8141.; (Hs (Cd) (Cd) Yellow image 2.0 0.26 Magenta image 0.26 2. 0 0.22 Blue-green image 0.07 0.22 2.0

The printing is performed in this case with the gamma values y=0.6; y=0.83; ly'=1.48.

The most important improvement is in the case of the print of the magenta image which in the maximum of the absorption, e. g., the thallium line 535ML at concentrations corresponding to neutral grey would be falsified by a print of the blue-green image of a maximum density 0.75.

A further advantage of the present invention is that it enables one to obtain not only very small irregular images but also irregular images which are all of practically the same magnitude. 'This is in the example corresponding to Figure 8 about 0.25. It is therefore possible to produce one correcting mask containing at the same time a print of all the three part pictures this print having a maximum density of 0.25 and a corresponding flat contrast which correcting mask is printed at the same time with each of the part prints obtained as described above, the correcting mask being a negative if the part prints are positives.

It will be understood that many modifications may be made in the above described examples without departing from the scope of the present invention. In each case printing is performed by light of a wavelength independent of the absorption maxima of the dyestuifs forming the part pictures of the multicolor image and for which the ratio of the absorptions is a maximum or as near as possible to such a maximum. In the case of more than one disturbing dyestuif image the maximum in question is preferably the maximum of the lowest ratio. Sometimes it may occur that the absolute amount of the absorption of the image to be printed for the printing light, for which the ratio of absorptions has its maximal value, is insufficient for reproduction with sufficient details in the black and white print. In such case the optimum printing light according to this invention will be within the range of wavelengths for which the range of sufhcient absorption and sufficient absorption ratio overlap each other. In the c ase, for example, of an image with three part images in blue-green, purple and yellow dyestuffs the absorption properties of the dyestufls are analysed, the absorption ratios calculated and preferably plotted against the wavelength and the printing light chosen accordingly. By proper choice of dyestuff concentrations the absorptions and therefore the absorption ratios may be altered in order to obtain absorption ratios of suitable value for the printing lights concerned. Whereas monochromatic printing light is chosen by preference, narrow spectral bands may be used if the maxima of absorption are sufciently fiat.

It is characteristic of the features of the present invention that subtractive master images from which it is intended to print separately the differently colored part images on to separate or combined printing layers, may further be rendered more suitable for printing purposes if one of the part images is a dyestuff image of higher contrast than the other dyestuff images.

In the master images according to the invention the dyestuif image which should have the highest contrast is that one formed by the dyestuff, in the preponderant absorption range of which the other dyestuis or one of them will have a substantial absorption.

Thus if it be intended to print a multicolor master image formed by three given dyestuffs, by the use of three given printing lights, the part image in the master image which should have the highest contrast is that one for which the dyestuff has, at the wavelength of its printing light (or the wavelength interval of its printing light), the smallest absorption in comparison to the absorption of the other dyestuffs.

When printing the master images according to the invention flat prints on the one hand and steep prints on the other would normally be obtained. Prints of any other desired contrast can be obtained by proper choice of the printing emulsions and conditions of development.

If, for example, all of the prints are to be developed to equal maximum density, each print must be developed to a different gamma value depending upon the respective dyestuif concentration in the master image. The choice of gamma values very different from each other is generally preferable.

For three given dyestuifs and three printing lights, dyestu concentrations can be calculated which in printing will result in a set of color selection prints in which the two largest irregular images are equal to each other, the following two in the order of their magnitude being equal again to each other. Such sets of prints are relative optima. Or a set of color selection prints can be obtained, the largest irregular image in each print of which is equal to the largest one obtained in the two other prints. Prints of this kind are the optimum prints which can be obtained in this case. Sets of prints between the relative and absolute optima can be obtained the conditions being given geometrically. 'I'he maximum density of the irregular images depends upon the absorption coefficients of the dyestuffs and can be readily predetermined. The choice of optimum printing lights for given dyestuffs is thereby made easier.

The relation between the densities of the irregular images and the ratio. of gamma values necessary to give prints of equal maximum density is shown geometrically, the ratio of gamma values being in inverse proportion to the maximum dyestuif concentrations. From the accompanying drawings it will be seen that the irregular image resulting from the absorption of a dyestuif which is not intended to be printed in the printing light of a second dyestuii and the irregular image caused by this second dyestui in the printing light of the first are in opposite relation; this relation is given by the abscissa of a straight line and that of a hyperbola for the same ordinate, representing the proportion of the maximum dyestui concentrations. If the absorption o1 one dyestuff in the printing light of the other is practically equal to zero the hyperbola will coincide with the co-ordinate axes or the straight line with the ordinate and in this case only the absorption of the latter dyestuff must be taken into consideration. In the example corresponding to Figure 4 the blue-green dyestuf is printed by light of a wavelength for which the yellow dyestuif is totally transparent. The hyperbola 4b may be caused to disappear by choosing the printing light for the magenta dyestui of a wavelength which is totally transmitted by the yellow dyestuff. This means, of course, that this printing light is shifted into a spectral region in which the absorption of the blue-green dyestui is not as low as before.

At rst sight it might seem that this is a disadvantage which nullifes the reduction of the disturbing effect of the yellow dyestuif when printing the magenta image. In fact, however, such choice of the wavelength is of considerable advantage. If printing is effected, for example, with light o 643.8; 535 and 405ML only three straight lines, which of course, are different from those shown in Figure 6 and which can be determined from the absorption coeicients of the dyestuffs at the selected wavelengths, need be considered for the determination of the dyestuff concentrations and conditions of development. If, for example, the irregular images defined by the steepest and the attest straight line are chosen such that they are equal to each other the third irregular image will in each case be smaller than the other two irregular images. In this case each diminution of both largest irregular images will result in a diminution of the third, whereas in the more general case shown in Figure 6 each diminution of the two largest irregular images causes a third irregular image to increase.

The case where it is desired to have the regular prints of equal maximum densities is only described for the sake of simplicity. It is not only possible to produce from these prints further prints in which the maximum density is no longer equal but the original prints themselves may be produced of unequal maximum density. It will be appreciated that the influence of the irregular images is not altered if the maximum density of the regular images is changed to the same degree.

What I claim is:

l. The method of reproducing from a multicolor subtractive master image in which a plurality of dilerent aspects of an object are recorded by differently colored images occupying the same picture area, a record of one of the said images recorded in the multicolor master image by a dye of such absorption characteristics that light rays of all the different wave lengths which said dye absorbs toa substantial extent are also absorbed by the master image as a result of the absorption of at least one of the other dierently colored records, which comprises, reproducing the record by light of a spectral composition for which the ratio of the difference between the optical density at the most intensely and at the least intensely colored points of the colored record to be reproduced to the diierence between the optical density at the most intensely and at the least intensely colored points of said diiferently colored record is substantially a maximum and which is within the range in which the rst of said differences has a value sufciently large for the reproduction of substantially all the details of the object represented by the master image.

search Room 2. 'I'he method of producing from a multicolor subtractive master image in which a plurality of different aspects of an object are recorded by differently colored images occupying the same picture area, a print of one of the said images recorded in the multicolor master image by a dye of such absorption characteristics that light rays of all the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one of the other differently colored records, which comprises, producing the print by monochromatic light for which the ratio of the difference between the optical density at the most intensely and at the least intensely colored points of the colored record to be printed to the difference between the optical density at the most intensely and at the least intensely colored points of said diiierently colored record is substantially a maximum and which is within the range in which the first of said differences has a value sufficiently large for the reproduction of substantially all the details of the object represented by the master image.

3. 'I'he method of reproducing from a multicolor subtractive master image in which a plurality of different aspects of an object are recorded by differently colored images occupying the same picture area, a record of one of the said images recorded in the multicolor master image by a dye of such absorption characteristics that light rays of all the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one of the other differently colored records, which comprises, reproducing the record by light of a spectral composition for which the smallest of the ratios of the difference between the optical density at the most intensely and at the least intensely colored points of the colored record to be reproduced to the difference between the optical density at the most intensely and at the least intensely colored points of each differently colored record is substantially a maximum and which is within the range in which the first of said differences has a value sufliciently large for the reproduction of substantially all the details of the object represented by the master image.

4. The method of producing from a multicolor subtractive master image in which a plurality of different aspects of an object are recorded by differently colored images occupying the same picture area, a print of one of the said images recorded in the multicolor master image by a dye of such absorption characteristics that light rays of all the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one of the other differently colored records, which comprises, producing the print b` monochromatic light for which the smallest of the ratios of the difference between the optical density at the most intensely and at the least intensely colored points of the colored record to be printed to the difference between the optical density at the most intensely and at the least intensely colored points of each differently colored record is substantially a maximum and which is within the range in which the iirst of said differences has a value suiciently large for the reproduction of substantially al1 the details of the object represented by the master image.

5. A photographic printing process in which a.

multicolor master image comprising three di'erent photographic records of an object is used, the records occupying superposed strata of the same picture area and being differently colored, the most intensely colored points of each individual record being more absorbent for light rays for which the density diii'erence between the most intensely and the least intensely colored points of said record is sumciently large for a reproduction of the details than are the most intensely colored points of every other record for the same light, at least one dye used in coloring said records having such absorption characteristics that light of all of the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one differently colored record, which includes the step of printing the record formed by the dye having such absorption characteristics with colored light of a spectral composition for which the smallest of the two ratios of the difference between the optional density of the said dye with respect to said colored light at the most intensely and at the least intensely colored points to the difference between the optical density of every other dye with respect to the same light at the most intensely and at the least intensely colored points of the other dye images is substantially a maximum and which is within the range in which the rst of said density diierences has a value sufficiently large for the reproduction of substantially all the details of the object represented by the record to be printed.

6. A photographic printing process in which a multicolor master image comprising three different photographic records of an object is used, the records occupying superposed strata of the same picture area and being diierently colored, the most intensely colored points of each individual record being more absorbent for light rays for which the density difference between the most intensely and the least intensely colored points of said record is sufiiciently large for a reproduction of the details than are the most intensely colored points of every other record for the same light, at least one dye used in coloring said records having such absorption characteristics that light of all of the dierent Wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one diierently colored record, which includes the step of printing the record formed by the dye having such absorption characteristics with substantially monochromatic light for which the smallest of the two ratios of the difference between the optical density of the said dye with respect to said monochromatic light at the most intensely and the least intensely colored points to the difference between the optical density of every other dye with respect to the same light at the most intensely and at the least intensely colored points of each of the other dye images is substantially a maximum and which is within the range in which the first of said density diierences has a value sufliciently large for the reproduction of substantially all the details of the object represented by the record to be printed.

7. A photographic printing process in which a multicolor master image comprising three different photographic records of an object is used, the records occupying superposed strata of the same picture area and being differently co1- ored, at least one dye used in coloring said records having such absorption characteristics that light rays of all of the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one differently colored record, the most intensely colored points of each individual record being more absorbent for a spectral range of light rays corresponding thereto and for which the density difference between the most intensely and the least intensely colored points of said record is sufficiently large for a reproduction of the details of said record than are the most intensely colored points of every other record for the same spectral range of light rays, the dyes forming the diierent photographic records in the multicolor master image being present in such maximum dye concentration that of the six ratios of the difference, between the optical density of each dye with respect to its corresponding spectral range of light rays at the most intensely and at the least intensely colored points, to the difference, between the optical density of every other dye with respect to the same spectral range of light rays at the most intensely and at the least intensely colored points, at least the two smallest ratios are substantially equal to each other for the different light rays, respectively, for which said two smallest ratios have substantially their maximum value, which includes the step of printing the record formed by a dye having such absorption characteristics that light of all of the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one differently colored record with colored light of a spectral composition for which the smallest of the two ratios of the diierence between the optical density of the said one dye with respect to said colored light at the most intensely and at the least intensely colored points to the dierence between the optical density of every other dye with respect to the same light at the most intensely and at the least intensely colored points of each of the other dye images is substantially a maximum and which is Within the range in which the rst of said density diierences has a value suiciently large for the reproduction of substantially all the details oi.' the object represented by the master image.

8. A photographic printing process in which a multicolor master image comprising three different photographic records of an object is used, the records occupying superposed strata of the same picture area and being differently colored, at least one dye used in coloring said records having such absorption characteristics that light rays of all of the different Wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one differently colored record, the most intensely colored points of each individual record being more absorbent for a spectral range of light rays corresponding thereto and for which the density difference between the most intensely and the least intensely colored points of said record is sufciently large for a reproduction of the details of said record than are the most intensely colored points of every other record for the same spectral range of light rays, the dyes forming the different photographic records in the multicolor master image being present in such maximum dye concentration that of the six ratios of the diierence, betwen the optical density of each dye with respect to its corresponding spectral range of light rays at the most intensely and at the least intensely colored points, to the diierence, between the optical density of every other dye with respect to the same spectral range of light rays at the most intensely and at the least intensely colored points, at least the two smallest ratios are substantially equal to each other for the different light rays respectively for which said two smallest ratios have substantially their maximum value, which includes the step of printing the record formed by a dye having such absorption characteristics that light of all of the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one differently colored record with substantially monochromatic light for which the smallest of the two ratios of the difference between the optical density of said one dye with respect to said colored light at the most intensely and at the least intensely colored points to the difference between the optical density of every other dye with respect to the same light at the most intensely and at the least intensely colored points of each of the other dye images is substantially a maximum and which is within the range in which the first of said density differences has a value sufiiciently large for the reproduction of substantially all of the details of the object represented by the master image.

9. A multicolor master image for color photographic purposes comprising three dilerent photographic records of an object, the records occupying superposed strata of the same picture area and being diiierently colored with dyestuffs, at least one dye used in coloring said records having such absorption characteristics that light of all of the diiierent Wave lengths that the said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one dierently colored record, the most intensely colored points of each individual record being more absorbent for a spectral range of light rays corresponding thereto and for which the optical density of said record at its most intensely colored points is suiciently large for reproduction of the details of said record than are the most intensely colored points of every other record, the dyes forming the different photographic records in the multicolor master image being present in such maximum dy'e concentration that the average slope of a curve representing the sum of the absorptions of said dyes throughout the total of said corresponding ranges is positive toward the blue end of the spectrum, the maximum dye concentration also being such that of the six ratios of the optical density of each dye for its said corresponding spectral range of light rays to the optical density of every other dye with respect to the same spectral range of light rays, the two smallest ratios are substantially equal to each other for the different light rays respectively for which said two smallest ratios have substantially their maximum value, the optical densities being determined by subtracting the optical density measured at the least intensely colored points of the dye image from the optical density measured at the most intensely colored points of the same dye image.

10. A multicolor master image for color photographic purposes comprising three different photographic records of an object, the records occupying superposed strata of the same picture Search Hoorn area and being differently colored with dyestuffs, at least one dye used in coloring said records having such absorption characteristics that light of all of the different wave lengths that the said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one differently colored record, the most intensely colored points of each individual record being more absorbent for a spectral range of light rays corresponding thereto and for which the optical density of said record at its most intensely colored points is sufliciently large for reproduction of the details of said record than are the most intensely colored points of every other record, the dyes forming the different photographic records in the multicolor master image being present in such maximum dye concentration that the average slope of a curve representing the sum of the absorptions of said dyes throughout the total of said corresponding ranges is positive toward the blue end of the spectrum, the maximum dye concentration also being such that of the six ratios of the optical density of each dye for its said corresponding spectral range of light rays to the optical density of every other dye with respect to the same spectral range of light rays, at least two of the three smallest ratios are substantially equal to each other for the diiierent light rays respectively for which said two ratios have substantially their maximum value, the optical densities being determined by subtracting the optical density measured at the least intensely colored points of the dye image from the optical density measured at the most intensely colored points of the same dye image.

l1. A multicolor master image for color photographic purposes comprising three different photographic records of an object, the records occupying superposed strata of the same picture area and being differently colored with dyestuffs, at least one dye used in coloring said records having such absorption characteristics that light of all of the di'erent wave lengths that the said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one differently colored record, the most intensely colored points of each individual record being more absorbent for a spectral range of light rays corresponding thereto and for which the optical density of said record at its most intensely colored points is sufliclently large for reproduction of the details of said record than are the most intensely colored points of every other record, the dyes forming the different photographic records in the multicolor master image being present in such maximum dye concentration that the average slope of a curve representing the sum of the absorptions of said dyes throughout the total of said corresponding ranges is positive toward the blue end of the spectrum, the maximum dye concentration also being suc]` that of the six ratios of the optical density of each dye for its said corresponding spectral iange of light rays to the optical density of every other dye with respect to the same spectral range of light rays, the two smallest ratios are substantially equal to each other for the different light rays, respectively, for which said ratios have substantially their maximum value and the next two smallest ratios again are substantially equal to each other for the different light rays respectively for which these ratios and at least one of said smallest ratios have substantially their maximum value,

the optical densities being determined by subtracting the optical density measured at the least intensely colored points of the dye image from the opticalpdensity measured at the most intenseg ly colored points of the same dye image.

12. A multicolor master image for color photographic purposes comprising three different photographic records of an object, the records occupying superposed strata of the same pic- 1. ture area and being differently colored, each of the three dye images showing at its most intensely colored points absorption for colored light rays which are absorbed to a less extent by the most intensely colored points of each differently u colored record, one dye used in coloring said records having such absorption characteristics that light of all of the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the l absorption of at least one differently colored record, the said dye being present in such maximum dye concentration that the average slope of a curve representing the sum of the absorptions of said dyes is positive toward the blue end of I the spectrum and the ratio of the absorption of said dye to the absorption of said diierently colored record is sullciently large to permit printing the record formed by said one dye without material interference from said diierently colored record the absorptions being determined by subtracting the optical density measured at the least intensely colored points of the dye image from the optical density measured at the most intensely colored points o1' the same dye image,

13. A multicolor master image for color photographic purposes comprising three different photographic records of an object, the records occupying superposed strata. of the same picture area and being differently colored, each of the three dye images showing at its most intensely colored points absorption for colored light rays which are absorbed to a less extent by the most intensely colored points of each diil'erently colored record, the yellow dye used in coloring one of said records having such. absorption characteristics that light of all of the different wave lengths which said dye absorbs to a substantial extent are also absorbed by the master image as a result of the absorption of at least one diiIerently colored record, the yellow dye being present in such maximum dye concentration that the average slope of a curve representing the sum of the absorptions of said dyes is positive toward the blue end of the spectrum and the ratio of the absorption of said yellow dye to the absorption of said diierently colored record is sufficiently large to permit printing the record formed by said yellow dye without material interference from said differently colored record.

PAUL GOLDFINGER.

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