Philip a. Hunt Chemical Corporation

Louis D Pratt

Donald J Sykes

A two-step black and white photographic process in which conventional black and white developing of latent images in a silver halide black and white emulsion first is carried out and then, instead of simply fixing the developed emulsions containing black and white images, the emulsions are fixed and bleached concurrently for a short period of time long enough to perform the fixing and to enable a controlled mild degree of bleaching to occur. Such bleaching is carried out only for a time long enough selectively to attack low-density areas of freshly developed black and white images at a greater rate than areas of heavier density so as to depress the toe of the D log E curve without markedly affecting the balance of the curve, thus enhancing the images by obtaining a general increase of contrast, a reduction or total elimination of fog and a reduction or elimination of film haze, this latter being applicable primarily to radiology. The bleaching/fixing solution contains a standard fixative such as a thiosulfate, a chelated ferric or cobaltic salt capable of bleaching the silver image by oxidation and, optionally, an accelerating agent which accelerates bleaching. The bleaching/fixing solution also contains standard addenda.

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North Bergen, NJ, United States of America

Louis D Pratt