GB462232A - Improvements in colour photography - Google Patents

Abstract

462,232. Colour photography. ALLISON, D. K. Aug. 27, 1935, No. 23955. [Class 98 (ii)] Two positive images are produced from two colour-component negatives on superposed emulsion layers and coloured with colours complementary to the colours recorded in the respective negatives, and an image in a third colour is printed photomechanically or by imbibition on one of the positive images from a matrix produced from one or both colourcomponent negatives. The colour-component negatives are produced on a bi-pack comprising a front orthochromatic film dyed with Congo Red and a rear panchromatic film. The two negatives are printed on to opposite sides of a double-coated film, and the positive produced from the orthochromatic negative is toned red with an uranium-toning bath and the other positive toned blue with an iron-toning bath. Alternatively, either or both of the positives may be dye-toned, using red or blue basic dyes after mordanting with an iodine bleaching bath or a copper ferrocyanide toning bath. A positive print from the orthochromatic negative is printed to give a negative, which is etched with a solution including hydrogen peroxide to give a gelatine relief. A yellow image is printed using an acid yellow dye from this relief on to either of the two other images, preferably the red image. In a modification, a developed positive print from both negatives on double-coated film is printed in registry on to an undeveloped positive print from the panchromatic negative on a single coated film, which is then processed to form a gelatine relief employed as previously described. -The gelatine relief may also be produced by the bichromate process, the pinatype process, and the relief - development process. The two colour-component negatives may also be printed on to a film having two emulsions on the same side of the support, or a thick single emulsion. The developed and fixed film may be coloured by bleaching and dye-toning the outer image and then chemically toning the inner image, or by differentially iron- and uranium-toning the outer and inner images respectively.