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The Objective Measurement of the Graininess of Photographic Emulsions

Goetz, A. and Gould, W. O. and Dember, A. (1940) The Objective Measurement of the Graininess of Photographic Emulsions. Journal of the Society of Motion Picture Engineers, 34 (3). pp. 279-310. ISSN 1545-0279. doi:10.5594/J10097.

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A definition of a graininess coefficient G is given by the distribution function (2/G' √π)∫_0^x e ^-(x/G')^2 dx of relative transparency fluctuations (ΔT/T_m =x) in emulsions. In practical units G=1000G' . — An instrument is described which measures the graininess of an emulsion sample directly in G. It consists of the graininess photometer which produces a microphoto-metric record in terms of x and an integrator which analyzes this record photoelectrically in terms of the probability function and indicates G. There are no standards involved in the instruments except for the geometrically defined area which scans the sample and which is simply related to G. — The G values obtained for different emulsions are described for constant density as well as the variation of G with the density. The transformation of G into G8, the graininess effective in sound reproduction, is given as G_8=G·10^-D; furthermore, the corrections necessary for G to obtain visual graininess impressions, are discussed. The latter varies with the illumination on account of deviations from Fechner's law for certain ranges of brightness. Their visual effects are predictable from G. — The effect of scattering of the incident light within the emulsion upon the measured graininess is discussed. — The observed graininess density functions are compared with those of other authors and agreement and deviations are found where they are to be expected. — The relation between graininess and grain size is discussed with the conclusion that a priori no relation exists between the two qualities. — The grain distribution is found to follow, in many cases, very closely the probability function.

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Deposited By: Kristin Buxton
Deposited On:27 Oct 2015 22:29
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