THE PANCHROMATIC SENSITIZATION OF SINGLE CRYSTALS AND EVAPORATED FILMS OF SILVER BROMIDE

An experimental study is reported of methods of achieving the highest degree of red sensitization of single crystals and evaporated films of silver bromide. Variations in dye treatment, surface orientation, and surface area all failed to produce a reasonable level of panchromatic sensitization on crystals. The surface area of crystals was too low to allow sufficient dye pick-up for efficient sensitization. With evaporated films, two approaches were tried: (1) screening of various classes of dyes to determine their relative efficiency for sensitizing these materials, and (2) improvement of the initial sensitivity of evaporated film samples by variation of the evaporation parameters. The latter approach proved to be the better. The dye sensitization of evaporated films having an initial sensitivity of ASA 0.1 when removed from the evaporator produced materials having over-all sensitivities of ASA 2 and red sensitivities (through a Wratten 25 filter) of 0.6. Preparation of a material sensitized to an ASA Exposure Index of 10 (5500 K light source) with a Wratten 25 filter factor of not more than 5, is shown to be within reach. (Author)