GB755458A - Photographic colour correction - Google Patents

Abstract

755,458. Photographic colour correction. AGFA AKT.-GES. FUR PHOTOFABRIKATION. May 3,1954 [May 2, 1953], No. 12851/54. Drawings to Specification. Class 98 (2). Corrected multicolour images or separation records, described as of special importance in the reproduction of original images as of fabrics, carpets, wallpapers, handbags or shoes for advertising purposes, are made by printing the original coloured image through a mask or corrective prepared therefrom which represents an optical combination of a colour separation record with another colour separation record of opposite but otherwise similar gradation, both records being formed of dyes of the same colour and which colour has the same absorption as the unwanted absorption of the partial dye images to be corrected. The most important mask, described as a " yellow corrective " and by which better reproduction of the yellow and blue colours is obtained, is made by contact printing an original multicolour negative with blue light on to a silver halide emulsion layer, processing the latter to black and white, placing it in printing relation to the original multicolour negative, exposing therethrough with green light and processing the result which constitutes the mask or corrective to a yellow dye image. Directions for obtaining the desired gradation of the intermediate black and white image, as by use of a grey step wedge, are provided in the Specification. The mask of next importance, a " magenta corrective " for increasing the saturation of the colours green and magenta is made similarly using green light for the first printing, red light for the second, and processing of the mask to magenta. The corrected images or records may be made using both of these " correctives," one on each side of the original multicolour negative. The " yellow corrective " may be adapted to mask unwanted blue absorption of both the magenta and blue-green dyes of the original negative by use of green-red light for exposure thereof, or to mask unwanted blue and green absorption of the blue-green image dye by processing it to a yellow-orange colour. The above printing and processing steps may be united into a single step by effecting the first exposure on to a two-layer material, one layer of which is sensitive to the part of the spectrum in which the unwanted absorption of the image dye lies and can be processed directly to positive, and the other sensitive to the part of the spectrum containing the desired absorption and which can be processed to a negative; thus such a " yellow corrective " for the magenta dye is made by exposure of the original multicolour negative with blue and green light into a blue-sensitive positively-developing layer with underlying yellow filter and negatively developing orthochromatic layer, which layers are colour developed to yellow to provide a mask for printing the original negative with white light to give a corrected multicolour positive.