26 September 1997 Photographic-fog-level determination: an objective criterion
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The knowledge of the true fog level of the exposed and developed photography emulsion is necessary both for correct plotting of the characteristic curve and for accurate determination of the exposing light intensity distribution. It is suggested to calculate the function S equals lg(10D-Df - 1), where S is the modified Seidel function, D are the measured densities and Df is the fog density. The value of Df at which S versus logarithm of exposure shows a linear form, is the true fog density. This linear dependence is an additional criterion that allows one to judge the correctness of the fog level evaluation and to distinguish the fog from a uniform background.
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Yury S. Muzalievsky, Yury S. Muzalievsky, } "Photographic-fog-level determination: an objective criterion", Proc. SPIE 3140, Photometric Engineering of Sources and Systems, (26 September 1997); doi: 10.1117/12.279227; https://doi.org/10.1117/12.279227

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