Patent GB-494341-A (GB)
Title: Process for the production of partial colour selection pictures out of subtractive multi-colour images
IPC: G03F3/04
Filed: 1937-03-24
Abstract: 494,341. Colour photography. GASPAR, B. March 24, 1937, Nos. 8649 and 8650. Convention dates, March 24, 1936 and Sept. 26, 1936. Drawings to Specification. [Class 98 (ii)] In producing a subtractive multicolour print from a subtractive multicolour original by means of colour separation records produced from the original, at least one of the records is produced by printing from the -original by coloured light which is substantially absorbed only by the image to be printed, printing a second image onto sensitive material with a printing light which is absorbed by the second image and also by the first image and either printing the first image onto the second image to correct it or using the first image as a correcting mask in printing from the second image in preparing a multicolour print. The third image in the case of three layer material may be similarly produced and used. For example, an original having three layers containing images coloured purple-red, blue-green and yellow is used. The bluegreen image is printed with red light on a redsensitive or panchromatic material and the resulting image is developed. The purplered image is then printed by green light on a green-sensitive layer and the negative of the blue-green record printed thereon and the resulting image developed. Lastly, the yellow image is printed with white light on a bluesensitive, i.e. not specially sensitized layer, and the negatives of the blue-green and purplered images printed thereon and the layer developed. The separate images are used for printing on three layer material. For example, three layer material comprising a blue-sensitive layer coloured purple-red with diamine fast pink G, a red-sensitive layer dyed yellow with chrysophenine, and an infra-redsensitive layer dyed blue-green with diamine pure blue FF is printed upon in succession from the separate images using red, blue, and infra-red light, the images developed and treated with a dye-destroying bath of thiocarbamide and citric acid. The separate images may be negative or positive silver images or images in dye produced, for example, by the dye destruction process. The process may be employed where the colours of the original are incorrect, for example where the red colour record image is coloured yellow, the blue record purple-red and the green record blue-green, a correct result being produced by printing the separate records onto the appropriate coloured layers using appropriate lights. Other examples of procedure are given in the Specification. The separate colour records may be produced on two or three layer material, the additional layers being used to record the compensating images. For this purpose, two blue-sensitive layers, one dyed yellow, on the same or opposite sides of a support may be used. Alternatively the sensitivity of the layers may be different. In order to obtain a compensating image of low contrast one or more of the supplementary layers may be poor in silver. Emulsions consisting of mixed particles of differing sensitivity may also be used. One of the superimposed emulsions may be a solarized emulsion which yields a positive directly on development.