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The Objective Quantitative Determination of the Graininess of Photographic Emulsions

Goetz, A. and Gould, W. O. (1937) The Objective Quantitative Determination of the Graininess of Photographic Emulsions. Journal of the Society of Motion Picture Engineers, 29 (5). pp. 510-538. ISSN 1545-0279.

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A graininess meter as an instrument for objective and quantitative determination of density fluctuations of photographic emulsions is described. The instrument, specially designed for the purpose, produces a microphotometric record of a uniformly exposed area in terms of relative transparency fluctuations (ΔT/T_m) (T_m — mean transparency). The resolving power of the optical system is greater than the individual grain size, so that granularity as well as graininess is recorded. Unlike the usual microphotometric records, the records are produced in such a way that they can directly undergo a process of partial integration in a photoelectric integrator designed for the purpose. Thus the distribution of the areas occupied by transparency fluctuations as a function of the magnitude of the deviation is determined. In addition, the sum of the fluctuations can also be measured. The distribution function is found to be predominantly a Gaussian probability function (C/G)e^-(x/G)2, upon which an exponential distribution function (C/G)^e-(x/G) is superimposed. The graininess constant G is defined as the inverse rate of decline of the occurrence of relative transparency fluctuations with the deviation from average transparency. A construction of the integrator, though provisory, is given which allows direct readings of the numerical values of G without involving calculations. — The graininess meter has been applied to the measurements of the graininess-density function and, furthermore, to the effect upon the emulsion by the variation of the mode of development. In addition, quantitative determinations of the increase of the graininess in contact prints with respect to the graininess qualities of the negative materials from which the print is made are described.

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Issue or Number:5
Record Number:CaltechAUTHORS:20151027-151854913
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ID Code:61589
Deposited By: Kristin Buxton
Deposited On:27 Oct 2015 22:27
Last Modified:03 Oct 2019 09:09

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