| 摘要 |
684,248. Colour photography. FRAUNHOFER, H., VON, and BOMBACK, R. H. Feb. 2, 1951 [Feb. 9, 1950], No. 3344/50. Class 98 (ii). A negative comprising a support such as celluloid carrying three superimposed differentially sensitized silver halide emulsion layers of which the two lower layers contain colour formers and the uppermost, which may be blue sensitive and provided with the usual underlying yellow filter, is without colour former, is treated to develop the image in the uppermost layer, after which, without further treatment, the unreduced portions of silver halide of such layer are caused to transfer by diffusion onto another support and be there reduced to form a positive image in the manner described in Specification 614,155; and then the negative is further treated to produce coloured images in the two lower layers and to bleach out silver from all the layers and to bleach out the yellow filter when such is used. The positive image can be used to print off duplicate negatives in the usual way. The uppermost, blue sensitive layer of the negative may consist of a very " thin " or dilute coating of emulsion, possibly containing only 25 per cent of the normal amount of silver halide, since a " ghost " image only need be formed therein, resulting in a greater overall speed of the film, and such is developed in a normal silver halide developer but controlled as regards take-up quantity or controlled by addition of viscosity increasing substances. Specification 682,062 also is referred to.
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