Temperature Effects on Photographic Sensitivity

Abstract

The effect of temperature on the photographic sensitivity of three emulsions has been investigated over the restricted platen temperature range of approximately 16 °C to -55 °C. Exposures on Tri -X and Plus -X were made in neutral, red (6050Å), and blue (4490Å light. The exposures on 103a -0 were made only in neutral and blue light due to the insensitivity of 103a -0 to light redder than about 5500Å. In each exposure a 12 -step neutral density wedge was imaged on the film. The results are straightforward. Each emulsion displayed a sensitivity dependence with temperature in each color. The Tri -X and Plus -X showed points of optimum temperature (at maximum density) within the range employed. The optimum temperature however was not constant but varied with emulsion, color, and light level. The optimum temperature in general increased with increasing light level and was apparently higher at all light levels for the red exposures than for the blue. The 103a -0 displayed a nearly linear decrease in sensitivity with decreasing temperature. The point of optimum temperature for the 103a -0 is therefore higher than 16 °C at these light levels. A comparison of the blue exposures of 103a -0 and Tri -X reveals greater response for the Tri -X at the fainter light levels. However, the effect is reversed in the higher light levels. This response is interpreted as a difference in gamma of the two emulsions. The fact that the optimumly cooled Tri -X is more sensitive to blue light than the 103a -O at the lower light levels is not important to astronomical photography unless the same effect occured at much longer exposure times and fainter light levels.