Catalytic Phenomena Related to Photographic Development

Abstract

Publisher Summary This chapter discusses the catalytic phenomena related to photographic development. The light-sensitive layer of the present-day photographic material consists essentially of a large number of tiny crystals of silver halide embedded in a layer of gelatin. The tiny crystals, or grains, of the most sensitive photographic materials are composed of silver bromide, a small percentage of iodide, and a very small but very important amount of silver sulfide or possibly silver or both. The halide in the less sensitive materials may be simply bromide, chloride, or mixtures of the two. In the study of the mechanism of development, it is generally desirable to compare the rate of reduction of grains which have been given relatively large exposure to light (avoiding, however, over-exposure leading to solarization) with the rate of reduction of completely unexposed grains. The differentiation in rate is then large. The time at which the rate of increase of optical density in the image region becomes equal to the rate of increase of density in the unexposed region is a convenient criterion for the “maximum degree of development.”