Patent GB-487685-A (GB)
IPC: G03C7/14
Abstract: 487,685. Colour photography. LASSUS ST. GENIES, A. H. J. DE. Dec. 22, 1936, Nos. 35198 and 35199. Convention dates, Jan. 4 and Dec. 1. Drawings to Specification. [Class 98 (ii)] A coloured photograph is obtained from a photograph comprising a plurality of developed colour component images on a lenticular film by partial illuminations through the lenticulations each of which partial illuminations is followed by chemical treatment of the photograph, the partial illuminations permitting the selective action of the chemical agents employed whereby the appropriate colouring of the colour component images is produced. In one example, in the gelatine of a lenticular film developed as a positive and fixed is incorporated a leuco-base of a red dyestuff, for example a leucorhodamine, and the film is illuminated through its lenticulations so that only the red monochrome receives light. A light projector having three light sources successively uncovered by a shutter may be employed. The leuco-base is oxidized and the corresponding parts of the gelatine in each elementary chamber are coloured red. The excess of leuco-base is removed and the operation is twice repeated using successively the leuco bases of blue and green dyestuffs, for example hexamethyl-para-leucaniline and leuco-malachite green. Tanning agents such as formalin, tannin, and potassium bichromate may be incorporated in the gelatine. In another example, the silver image in an unfixed lenticular film developed as a positive is transformed into a stable black compound by treatment with a bath containing copper sulphate, tri-potassium citrate, citric acid and ammonium sulphocyanide, or by effecting the development with indoxyl and thio-indoxyl, and if desired pyrogallic acid. The remaining silver halide is successively selectively exposed, developed and treated to form a dyestuff absorbing complex, the dyestuffs being inalterable by the succeeding operations. The remaining traces of silver halide are dissolved out, and the whole of the metallic silver is removed by Farmer's reducer. In another example, an exposed lenticular film or paper is developed as a positive in a developer such as indoxyl, washed, selectively exposed, developed in a colour developer, washed, again selectively exposed, developed in a colour developer, and so on. The whole of the silver and remaining silver halide is removed by Farmer's reducer. The film or paper is washed and dried, and the lenticulations may be effaced by varnishing. In a fourth example, the silver image in a developed positive image, the developing bath for which contained a silver halide solvent, is dissolved out but the film is not fixed. A coloured compound, for example an azo-dyestuff, is incorporated in the gelatine, the film is treated in a resensitizing bath, and a first selective exposure is effected. During the subsequent development the coloured compound is destroyed at the points of the silver image. The reduced silver is dissolved, and the operation of incorporating the coloured compounds selectively exposing and developing is twice repeated. The coloured compounds may be purple, marine blue, and yellow. The lenticulations may be effaced by varnishing. In a fifth example, starting from an unfixed lenticular film bearing a positive image, successive partial illuminations are effected directing the light so that in each elementary chamber the axis of the elementary beam falls on the line of separation between two of the three microscopic images, and the parts of the emulsion affected by the successive illuminations are coloured yellow, purple and marineblue respectively. The lenticular support may be freed from any trace of the previous bath by blowing or it may be placed in a bath of refractive index similar to that of air. After colouring the lenticulations may be flattened.