Chromogenic film stock
Subtractive 3 color: Chromogenic monopack
Rudolf Fischer and Hans Siegrist (Neue Photographische Gesellschaft)
Original Technical Papers and Primary Sources
Fischer, Rudolf (1913): Colour Photography—No. 15,055, 1912. In: The British Journal of Photography, 60, p. 595.
Fischer, Rudolf (1913): Toning Bromide Prints. In: The British Journal of Photography, 60, p. 712.
Fischer, Rudolf (1914): Coloured Tones by Development—No. 2,562, 1913. In: The British Journal of Photography, 61, pp. 329-330.
Fischer, R., and H. Siegrist (1914): Über die Bildung von Farbstoffen durch Oxydation mittels belichteten Halogensilbers. In: Photographische Korrespondenz, 51, pp. 18-22.
Evans, Ralph Merrill / Hanson, W.T., Jr. / Brewer, W. Lyle (1953): Principles of Color Photography. New York: Wiley, p. 297.
“COLOURED TONES BY DEVELOPMENT.—No. 2,562, 1913 (February 6, 1912).
The claim is for a process of making coloured photographic pictures, consisting in latent pictures obtained in halogen-silver films being developed with such developers as contain, besides the developing substance, a body which couples itself with the oxydation product of the developer to form a coloured body soluble with difficulty.
The development of photographic halogen-silver films leads, in general, to a black picture substantially composed of silver. Individual cases are, however, well known in which coloured pictures can be obtained directly when developing. Thus, developing with pyro yields a yellowish-brown picture, with indoxyl a blue, and with thioindoxyl a red picture. Also, the other customary photographic developers yield, under suitable conditions, e.g., absence of sodium sulphite and similar bodies, more or less coloured pictures. The colours thus obtained are, however, either not very decided or, as in the case of the developers from the indigo group, not readily obtainable.
It is now found that very highly coloured pictures can be very readily obtained not by using the oxidation products of the developers alone, but by adding to the developers substances which become coupled with those oxidation products of the developer which are formed whilst developing and form coloured bodies soluble with difficulty. According to the developers or coupling bodies which are employed, we obtain representatives of various classes of colouring materials or dyes, of which the following are given as examples :—
The bodies soluble with most difficulty are obtained with p-phenylenediamine as developer and phenols or compounds with acid methylene groups as coupling bodies.
The p-phenylenediamines comprise the side chain homologues and nucleus homologues, also the substitution products of p-phenylenediamine in one amido group or in the nucleus, the other being free.
Further, one amido group may be included in a ring system : p-aminophenylene-piperidine.
By phenols, likewise, the side chain and nucleus homologues and the substitution products are to be understood.
The acid methylene compounds may be both of an aliphatic and also of an aromatic nature.
Further, the methylene group may be substituted when the substituting group is split off during the reaction.
The colour developers can also be employed in such a form that they are incorporated in the film, or a separate layer is applied to the layer or film sensitive to light. Either the leuco compounds, the separate components, or only one of the two may be so incorporated or used. The colouring-material picture can be .isolated by removing silver by means of one of the well-known agents.
2 gms. hydrochloride of p-phenylenediamine, 30 gms. soda, 1,000 c.c.s. water. A greenish-blue picture is obtained.
(2) 2 gms. thymol dissolved in 20 c.c.s. acetone are added to the following solution :—
Hydrochloride of p-amidophenylenepiperidine, 40 gms. soda, 100 c.c.s. water. Blue picture.
(3) 2 gms. α-naphthol dissolved in 20 c.c.s. acetone are added to the following solution :—
2 gms. hydrochloride of dimethylparaphenylenediamine, 30 gms. soda, 1,000 c.c.s. water. Blue picture.
(4) 2 gms. thioindoxyl-carboxylic acid dissolved in 40 c.c.s. acetone are added to the following solution and shaken well :—
2 gms. hydrochloride of monoethylparaphenylenediamine, 40 gms. potash, 1,000 c.c.s. water. Red picture.
(5) 2 gms. O-nitrobenzylcyanide in 20 c.c.s. acetone are added, to a solution of 2 gms- hydrochloride of dimethylparaphenylenediamine, 30 gms. soda, 1,000 c.c.s. water. Brownish-red picture.
(6) 2 gms. α-chlor-ethyl-aceto-acetate in 20 c.c.s. acetone are added to 2 gms. diethylparaphenylenediamine, 40 gms. potash, 1,000 c.c.s. water. Yellow picture.
(7) 2 gms. p-nitrobenzylcyanide in 20 c.c.s. acetone are added to 1 gm. p-amidophenol, 40 gms. potash, 1,000 c.c.s. water. Brown picture.
(8) 2 gms. 4 oxy-2 amido-4-diethylamido-diphenylamine, 50 gms. potash, 1,000 c.c.s. water. Blue picture.
(9) 2 gms. 4-dimethylam.idophenyl-u-eyan-azomethine-phenyl. 100 gms. potash, 100 c.c.s. water. Orange-coloured picture.
Rudolf Fischer, 20, Beymer Strasse, Steglitz, Berlin.”
(Fischer, Rudolf (1914): Coloured Tones by Development—No. 2,562, 1913. In: The British Journal of Photography, 61, pp. 329–330.)
“COLOUR PHOTOGRAPHY.—No. 15,055, 1912 (June 27, 1912).
It is well known that by developing exposed films of silver halides monochrome pictures can be directly obtained, the exposed silver halide oxidising the substance in the developer to an insoluble or comparatively insoluble colouring matter which is precipitated on the reduced silver. An example of such colour development is found in the case where an alkaline pyrogallol developer is employed without any preservative such as sodium sulphite. Amongst other substances which act in a similar manner may be mentioned indoxyl, thioindoxyl, hydrochinone and alpha-naphthol, paramidophenol and xylenol (C6H3(CH3)2OH), paramidophenol and alpha-naphthol, dimethyl paraphenylenediamine and alpha-naphthol, dimethyl paraphenylenediamine and phenol, also toluylenediamine, diamidodiphenylamine (NH2.C6H4.NH.C6H1.NH2.) and other diphenylamine derivatives, and generally those bodies which while acting as developers also produce a more or less insoluble coloured oxidation product. This mode of development will be termed “colour development,” and the substances causing the same “colour formers.”
The invention utilises this stronger oxidation capacity of exposed silver halide as compared with that of unexposed silver halide for producing coloured photographs. This is done in various ways, and both additive as well as subtractive coloured pictures can be produced equally well.
1. For example, if a colour screen is to be made as an additive colour picture, we expose a silver halide layer sensitive to light under a screen, say a line screen, one-third of whose surface is permeable to light, whilst two-thirds thereof are covered. We then develop the layer in a solution producing a blue colouring matter – for example, indoxyl – and an alkali, such as described in “Photographischen Korrespondenz,” 1907, pages 55 and 115. We than expose it under a second screen, or the original screen, so that a further one-third of the surface is exposed, and then develop it in a solution, for example, thioindoxyl, producing a red colouring matter. We then expose the whole surface without the screen negative, the remaining or previously unexposed silver halide being acted upon, and this is coloured green when developed in a solution, for example, chlorindoxyl, producing a green colouring matter. During the second and third exposures the silver below the particles of colouring matter protects the unchanged silver halide below it from further exposure and development. Moreover, this protection can be afforded by the colouring matter already formed, by using during the subsequent exposures a light which is absorbed by the existing colouring matter. The three-colour picture or screen thus formed can be used as a three-colour screen after removing the silver under the particles of colouring matter with, for example, Farmer’s reducing agent, and after removing the unchanged silver halide by means of a fixing agent.
2. For subtractive pictures we employ, as usual, a set of three negatives, each of which corresponds to one of the primary colours. From these negatives three positives are produced, then developed as above described with the corresponding colour formers, and finally placed one above the other.
The positives can also be obtained directly from complementary-coloured negatives produced by means of multi-colour screens such as described above, by making selective positives from the negatives , either using filters and printing on a panchromatic layer, or without filters and printing on selectively sensitised halogensilver layers. These positives are developed, coloured, and superposed one on another as described above.
The last described method of reproduction on three selectively sensitised emulsions can be carried out in one operation in the following manner :—Three emulsions are made, one being sensitive only to blue light, another only to green light, and a third only to red light. In these emulsions are incorporated the substances necessary for the formation of each colour, i.e., the substances termed “colour formers,” the latter being so selected, for example, that that colour is formed at any time which is complementary to the corresponding selective colour-sensitisation of the silver halide. Now, when these three emulsions are poured out in three layers one on another, there is formed, for instance under the action of blue light, a yellow colour, and at the places acted on by red and green light the corresponding complementary colours. When the colours are correctly chosen those places which white light strikes become nearly black, whilst at those whereon no light strikes, for instance under the covered or dense parts of the negative, no colouration is formed at all, and consequently, after fixing, white results. By printing a screen negative on such a layer the correct colours and correct black and white values are obtained.
Instead of pouring the three above emulsions in three layers one on another, before pouring them we may treat them in a suitable manner, for instance by tanning, so that they can be mixed without the three compounds (silver halide and colourformers) uniting to form one homogeneous layer or film. This treatment has heretofore been proposed for a theoretically developed process of colour photography. (“Photographische Korrespondenz” of 1907, pages 55 and 115.)
The silver halide, which is unchanged during the printing operation, and the silver formed simultaneously with the colouring matter are removed by fixing and reducing agents.
When practising the process with three layers we may use a yellow colouring matter mixed with a binder as an intermediate layer for the purpose of reducing the sensitiveness to blue in the layers sensitive to green and red. It is, moreover, preferable not to pour the three emulsions directly one on another, but to interpose a colourless layer in order to prevent diffusion of the colourreducing substances.
An example of one method of carrying the invention into effect is as follows :—With a complementary-coloured screen-negative an exposure is made through a blue-filter on a transferable panchromatic layer of emulsion. The exposed picture is developed with pyro, fixed, and the silver removed, say, by Farmer’s reducer. The developer is made up as follows: Pyrogallol 1 gramme, soda carbonate 5 gms., water 100 c.c.s. Such a developer will give, as is well known in the case of a pyro developer used without a “preservative,” such as sodium sulphite, a yellow picture, which is now removed and transferred to a suitable backing or support. An exposure is then made through a green filter on a similar layer, and a purple-red picture developed in the following developer: 0·5 grammes of thioindoxyl carboxylic acid, 5 c.c.s. of acetone, 5 grammes of potash, and 100 c.c.s. of water. After fixing and removing the silver this red picture is transferred on to the yellow one. Finally, by using a red filter, an exposure is made on a panchromatic layer, and this is developed in the following developer: 0·5 grammes of indoxyl carboxylic acid, 5 c.c.s of acetone, 2 grammes of potash, 100 c.c.s. of water. After the removal of the silver and halogen-silver this blue picture is transferred on to the two former pictures.
Rudolf Fischer, 20, Beyme Strasse, Steglitz, Berlin.”
(Fischer, Rudolf (1913): Colour Photography—No. 15,055, 1912. In: The British Journal of Photography, 60, p. 595.)