Photographic Sensitivity as a Function of Exposure Time and Temperature*

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Abstract
Reciprocity failure curves in the range between 1- and 256-seconds exposure time of three fine-grain experimental emulsions containing 2.4 mole percent iodide were determined in the temperature range between +50 and -195 C for radiation of 400-mµ wavelength with surface and internal development. The light absorption of the same emulsions in the temperature range between +25 and -137°C for radiation of 400-mp wavelength was measured.With internal development, practically no low intensity reciprocity failure occurs at and below -50°C, while with surface development no failure occurs between -50 and -150°C. In no case was high intensity failure observed in this temperature range.With surface development, an extremely large decrease in sensitivity is observed between -150 and -195°C, together with the appearance of a new type of high intensity reciprocity failure. In the same temperature region, a strongly temperature-dependent fluorescence is observed. It is believed that these two effects are connected, and it appears from sensitometric results that (a) the effect of the fluorescence is restricted to the grain surface, and (b) the fluorescence increases with the intensity of the exciting light at a rate higher than the first power of intensity.

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