Measurements of the effect of temperature variation on the reciprocity failure curves were made for several types of emulsions and for radiation of several different wavelengths. The effect of temperature variation upon emulsion sensitivity is shown to be very strongly dependent upon the intensity level at which the exposures are made. At very low intensities it is found that the speeds of certain emulsions can be increased several fold by lowering the temperature. An analysis of the data suggests a possible manner of division of the reciprocity curves into two component parts which, presumably, correspond to two different modes of utilization of the exposure in the formation of the latent image. A theoretical formulation based on the foregoing analysis yields the Kron-Halm catenary equation for representing the reciprocity failure curves.
J. H. WEBB, "The Effect of Temperature upon Reciprocity Law Failure in Photographic Exposure," J. Opt. Soc. Am. 25, 4-20 (1935)