Size of Silver Halide Grain and Wiener Spectrum

Abstract

Fourier analysis of grain pattern of photographic materials is known to be of great value towards estimating their optical characteristics. This paper presents a study on the relation between the grain size of silver halide of photographic emulsion and the Wiener spectrum of the developed grain pattern. Two series of photographic materials were used in this experiment, one has wide distribution of silver halide grain size and another series has a narrow distribution. The grain size of silver halide was determined by means of a centrifugal analyzer. The Wiener spectrum was determined by a high speed scanning microphotometer and a frequency analyzer. In a previous work, it was found that the mean grain size of developed silver grain was at least twice as great as the mean size of undeveloped grains. In the present work, bandwidth of the Wiener spectrum determined from silver grain pattern was found to be smaller than that expected from the mean size of silver halide grains. The mean size of grain mottles was estimated from the bandwidth of the Wiener spectrum. The mottle size obtained by this procedure was defined as expected mottle size and found that it was from four to twenty times as large as the expected grain size of developed silver halide for the specimens used in this experiment. Expected mottle size gives us a practical means of evaluating the mottle of silver halide grains and developed silver grains in the processed emulsion layer.