Power Spectrum of Granularity as Determined by Diffraction

Abstract

The optical diffractometer has been used for measuring the power spectrum of the granularity of uniformly exposed layers. It is first shown that the power spectrum obtained In a Fraunhofer diffraction pattern is, in general, not the same as the Wiener spectrum of granularity. But in the case of an ideal film, which is defined as a film in which all of the grains are circular with the same radius and have positions at random on the film, the two spectra would be equivalent if a point source were used. The form of the spectra remains nearly the same if the point source is replaced by a line-source. The spectrum has been registered of an artificial ideal emulsion imaged on a Lippmann plate. Commercial layers have also been investigated and noise spectra of several types of emulsions are shown. The increase of noise level with density has been shown and the differing actions of developers have been studied on a fast negative emulsion.