GB191413260A - Improvements in or relating to a Method of and Means for Producing Coloured Pictures, for instance Copies from Screen-plates. - Google Patents

Abstract

13,260. Christensen, J. H. May 29. [Addition to 25,419/13.] Colour photography.-Relates to processes for reproducing from autochrome and like screen photographs, or for producing colour photographs from separate component negatives by utilizing films of the kind described in the parent Specification. These films are made with silver bromide or like emulsions, which are characterized in that the permeability of the exposed parts is increased by development. The processes are adaptable for kinematograph colour films when reproducing a multicolour screen transparency. Three pieces of paper are coloured with dyes complementary to the colours of the screen plate to be reproduced, and are provided with films of the above-mentioned kind. These papers are brought, one at a time, into contact with a single plate or film containing a solution of the developer and illuminated through the screen plate by light which in each case is complementary to the colour of the coloured paper. The screen plate and the developer plate are maintained in the same relative position, and during each exposure, the developer acts upon the sensitive film and dye diffuses into the plate containing the developer in proportion to the intensity of the transmitted light. A colour picture is thus obtained in the film containing the developer, which can he mounted on paper or used as a diapositive. The process is the same whether for contact printing or enlargements. In adapting the process for producing copies from separate colour negatives, correct registering of the individual negatives is necessary; such registration is, however, effected before the following coloured paper is placed on the developed picture film. The developer plate can be formed by coating a glass plate or film with gelatine, and superimposing a film of less porous nature, such as hardened gelatine, viscose, or a porous nitrocellulose film, produced by pouring on a glass plate of 100 sq. cm. area about 10 ccs. of a 4 per cent collodion solution, to which is added 3 per cent of citric acid. The plate, together with the nitrocellulose film, is immersed in the developer and is placed between the developer and the coloured paper during the exposures. The dyes extracted from the colour films remain in the nitrocellulose film, which can be removed and mounted. The coloured papers are made bv coating a non-absorbent paper base with dyed colloid, or with an ordinary gelatine-silverbromide film dyed, and sensitizing this with a panchromatic film of the kind stated. In the case of the yellow paper which is acted on by blue light, an ordinary emulsion may be used.