Tone Reproduction in Colour Scales

Abstract

A comparison is made between microphotometric recordings, rms density deviations and visual graininess with the aid of a model emulsion (photographic reduction of a chance distribution of circular discs). Conditions are listed, under which rms density deviations are used for measuring the visual graininess. σF ≈ 0.01 is still considered grainy. The term “limit of enlarging factor” is defined with the aid of this result. The relation between granularity and Wiener spectrum is recalled. Measured Wiener spectra of varying degrees of order and of real emulsions are represented and discussed. It is indicated when the measurement of the Wiener spectrum appears worthwhile and when it may be omitted. The influence of grain size distribution on the Wiener spectrum is outlined, and the proposal is made to characterize a statistic manifoldness of particles by their Wiener spectrum. A brief description is offered of the measuring technique used.