The Influence of Ionizing Radiation on the Granularity of Colour Negative Emulsions

Abstract

Coatings of large grain emulsions that were given low exposures lo cobalt(60) gamma rays, in order to simulate the effect of background radiation, exhibited an increase in minimum density and granularity. This granularitywas greaterthan that obtained if thefilmswere exposed to light to give the same density. It was found, by use of photomicroscopy, that the main contribution to this high granularity was the formation of multiple developable cadres per grain, which gave more dye per grain during the partial development common to the normal colour negative processes. The effect of this latent image dispersity on the granularity was removal if the grains were fully developed cither in a black-and-white process or a special colour process. There was also an increase in granularity due to a high grain yield where several grains were rendered developable by the same gamma (y)-ray photon. The effects of silver coating weight and emulsion grain size on the granularity induced by ionizing radiation were also studied. II was concluded that latent image dispersity on grains was dominant at large grain sizes, where it persisted at all laydowns, and that high grain yield was dominant at small grain sizes and always disappeared at low coaling weights.