GB516937A - Improvements in or relating to photographic reproduction in colour - Google Patents

Abstract

,516,937. Colour photography BUTEMENT, C., and DUFAY - CHROMEX, Ltd. July 14, 1938. No. 20952. [Class 98 (ii)] Multicolour photographs are produced by (a) exposing to the object a support bearing two silver halide layers to produce red and green colour separation records; (b) exposing simultaneously a single support bearing a single layer to produce the third colour record and developing this to produce a record in yellow; (c) developing the two layer material and exposing the residual silver halide in one layer by light to which that in the other layer is insensitive; (d) developing the exposed layer to the appropriate colour, i.e., magenta or bluegreen and exposing the residual silver halide in the remaining layer; (e) developing this to blue-green or magenta and removing the silver from both layers; (f) superimposing the resulting two colour record on the yellow record. Preferably the support of the two layer material is transparent and the second exposure is effected through this. In an example a celluloid support carries red and green sensitive layers and is printed under a multicolour screen transfering, a magenta filter being provided between the layers if the red sensitive layer is also sensitive to green. A yellow filter is used during the exposure. The material is then developed and the red-sensitive layer fogged by exposure to red light e.g. from a cadmiummercury vapour discharge lamp and the residual silver developed to blue-green with a-naphthol and diethyl-p-phenylene-diamine. The green layer is then fogged by green light e.g. from a mecury vapour discharge lamp or by white light and developed to magenta with p-nitrobenzyl cyanide and diethyl-p-phenylene-diamine. The silver from both layers is then removed with Farmer's reducer. The yellow record is prepared by exposing bromide paper to blue light under the transparency reversing the image andtoning it yellow or employing a yellow colour developer, e.g., actoacetanilide and diethyl-pphenylene-diamine, as the second developer in the reversal process. The records are then superimposed in register. If the two layer material is on an opaque support this is stripped .off after superimposition. Specification 486,424 is referred to.