GB638048A - Improved process for producing multi-layer photographic color negatives containing masking images for color correction purposes - Google Patents

Abstract

638,048. Colour photography. GENERAL ANILINE & FILM CORPORATION. June 4, 1948, No. 15163. Convention date, Nov. 18, 1947. [Class 98 (ii)] A subtractively coloured negative incorporating colour-correction printing masks is made by exposing to a coloured object a multilayer film having silver halide emulsion layers sensitive to the blue, green and red regions of the spectrum and containing colour formers, colour developing, short stopping in an acid bath, washing, bleaching the developed silver to silver bromide, exposing to a controlled quantity of white light, developing in a black and white developer containing 0.02 to 0.4 gram per litre of a depth controlling re-agent of 1-mercapto-benzimidazol, 1-mercapto-benzimidazol-4-sulphonic acid, phenyl-mercaptotetrazol or 2-mercapto-benzthiazol ; fixing, washing and drying. Silver masks are thereby formed in the magenta and cyan layers (originally green and red sensitive, respectively) but not in the yellow coloured, blue-sensitive layer. The depth controlling reagents desensitize the upper strata of the emulsion layers but do not penetrate to the deeper sections, where the developer acts normally. The re-formed silver bromide, in situ with the coloured images is much less sensitive than the residual silver halide left after colour development and so the controlled exposure to white light does not form latent images therein. In examples this controlled exposure is 15 seconds at 5 feet from a 100 watt lamp, and the colour developing, the bleeching and the depth-developing solutions are specified. Specifications 458,400, 465,823, 489,161, 489,274, 491,958, 541,266 and 637,876 are referred to.