The Factors Determining Photographic Response

Abstract

The dependence of sensitometric response on the physical properties of the emulsion layer, e.g., mean grain size, grain size spread, is first examined, followed by a description and interpretation of variations in response and image quality with type of developer. Detailed variations in the relationship between density and exposure with nature of the exposing radiation (e.g., light, X-rays, electrons) are then reviewed and related to the associated differences in the numbers of electrons released by absorption of a single quantum or passage of a particle through a grain. Finally the phenomenon of reciprocity failure, the related topic of temperature dependence of sensitivity, and the wavelength variation of sensitivity for exposure to light, are reviewed and interpreted. From a practical point of view it is demonstrated that the calibration of the material must be carried out under the same conditions as those involved in recording the image. At the same time it is clear that fundamentally the same basic factors are involved under all conditions, so that responses to different sources of energy are broadly related.