GB553229A - Improvements in and relating to colour photography - Google Patents

Abstract

553,229. Colour photography. KODAK, Ltd., and BRANCH, L. E. T. July 25, 1941, Nos. 10433/42 and 10434/42, [both divided out of 553,196Drawings to Specification. [Class 98 (ii)] In the subtractive reproduction of a multicoloured original by a photographic or photomechanical process, colour correction is effected by making three colour-component records from the original, by contact or projection printing on one support or on separate supports, while it is in register with a mask having a single image which, in order to compensate for the undesired light absorption of blue light by the colour component records coloured minus green and minus red, is a record of the blue light absorption of the said two component records in the original or in the copy, and is coloured minus blue. The masking image is not formed in a sensitive layer in which a colour component picture record is made, although it may be formed, e.g. as described in Specification 547,519 in a layer integral with a layer or layers containing colour component picture records ; and it has an absorption gamma as measured by blue light which is not more than 50 per cent less or 50 per cent greater than the sum of the absorption gammas measured by the same light, of the said two component records. The correcting process may be extended by using in the reproduction a mask having two images, e.g. in superimposed layers on a single support, or in a mixed grain emulsion layer, one of which is as specified above, and the other of which, in order to compensate also for the undesired absorption of green light by one of the said component records coloured minus red, or of red light by one of the said component records coloured minus green, is either a red component record coloured minus green or a green component record coloured minus red, and has an absorption gamma as measured by light of the colour undesirably absorbed, and for which correction is being made, which is not more than 50 per cent less or 50 per cent greater than the absorption gamma, measured by the same light, of the component colour image which exhibits the undesired absorption. The correction process may, with appropriate raising of the gamma of the mask, be extended to correct for undesired absorptions of the dyestuffs used in both the copy and the original if this is a subtractively-coloured photograph. The masking images may be coloured by direct or indirect colour development, the developed silver being removed. The colour of the masking image may be adjusted to compensate for incorrectness of the gamma of one of the records, e.g. the effective absorption gamma of a record may be reduced by including in the mask a proportion of colouring matter of the same colour as the record, and in this case the mask may be made by colour development of a single emulsion using a mixture of colour couplers of the same kind as those used in producing the original or the copy. Specifications 427,518, 427,520, 458,665, 418,942, 493,952, 494,341, 512,608, 517,416. 537,864, and 551,614 also are referred to.