The Equation of the Characteristic Curve of Photographic Emulsions

A general equation has been derived for the characteristic curve for the spectrographic level of illumination. This equation is relatively simple, fits the experimental curve very well, and although applied to only three types of emulsions so far, is believed to be applicable to most emulsions. This equation is log 10 D 8 /D= (I 10 /I) n (t 10 /t) q where D and D 8 are density and saturation density, respectively; I and t are intensity and time, respectively; I 10 , t 10 , n and q are constants. D 8 , I 10 , n and q are all parameters of emulsion, wavelength and development.