Improved Photographic Emulsion for the Photosolubilisation Process

1,197,536. Photo-solubilization process. AGFA-GEVAERT A.G. Oct. 2, 1968 [Oct. 4, 1967], No. 46701/68. Heading G2C. A photo-solubilization process for the production of photographic images comprises (a) exposing imagewise to actinic light a supported photographic silver halide emulsion layer containing silver halide grains which have been made relatively less soluble in sodium thiosulphate by treatment with an organic compound that is capable of forming a silver salt of lower solubility in water than silver chloride and (b) treating the exposed layer with an aqueous solution of a silver halide solvent to dissolve out the silver halide in the more exposed areas at a rate substantially greater than in the less exposed areas until a positive silver halide emulsion is produced, in which process sensitivity specks are present only inside the silver halide grains of the silver halide emulsion. The silver halide grains consist preferably of a core of a silver halide which is chemically ripened and another layer of unripened silver halide. Chemical ripening with gold and/or sulphur sensitizers is preferred. In the example the complex Na 3 Au (S 2 O 3 ) 2 is used.