Low-temperature reciprocity failure of photographic emulsions and the temperature dependence of sensitivity.

Abstract

The observations of Biltz that, under certain conditions, reciprocity failure occurs at low temperatures (e.g., −196°C) have been confirmed. The failure is only of the high-intensity type and is restricted to emulsion-developer combinations of relatively low sensitivity, in particular, to surface image development of nonchemically-sensitized emulsions. At −196°C, the effect is exhibited most readily by silver bromoiodide emulsions.The effect represents an intensity-dependent recombination of electrons and positive holes released m a grain at low temperatures, thus modifying the number of electrons available for latent-image formation on warming up. The mechanism proposed for superlinear fluorescence adequately accounts for all observations and the connection between low-temperature reciprocity failure and fluorescence of the silver halides is established.The description of the dependence of sensitivity on temperature is revised. It is now apparent that, with certain emulsion-developer combinations, the speed loss from the normal temperature optimum to a low temperature may contain a factor additional to the absorption and ordinary high-intensity-failure speed losses.