A Note on the Induction Period of Photographic Development

Abstract

Historical and conceptual aspects of the induction period of photographic development are reviewed. The term, first introduced into photography by Sheppard and Mees, is now used in reference both to individual grains and to whole emulsions, leading to some confusion. According to the mode of presenting data, an induction period can appear or disappear. Given the electrode model of development, the bold S-shape of the density-time curve for hydroquinone can follow simply from the dependence of rate on the effective surface area of clumps of silver filaments. It is, rather, the absence of this type of induction period that calls for special comment to establish how the body of solid silver halide can play a rate-determining role.