Color Reproduction, Photographic

the reproduction of the color tones of a photographed subject on the subject’s image present on a positive color photographic material. One can judge the quality of photographic color reproduction by how accurately the color tones of the image correspond to the color tones of the subject, distinguishing three types of correspondence: physical, physiological, and psychological.

Photographic color reproduction is physically accurate when the spectral distribution of the radiation transmitted (by ordinary film) or reflected (by paper or pigmented film) by any part of the image fully coincides with the spectral distribution of radiation from the corresponding part of the photographed subject. Color reproduction is said to be physiologically accurate when the radiation reflected or transmitted by any part of the image is visually equal to the radiation from the corresponding part of the subject according to the objective, or colorimetric, characteristics of light, such as the three measurement coordinates. With psychologically accurate photographic color reproduction, the subjective perception of the color of any part of the subject and that of its corresponding part in the image are identical; in this case it is necessary to take into account the unavoidable distortions of the colors of three-dimensional subjects introduced by the two-dimensional nature of the image, especially along the contours of image details.

In amateur and professional photography and cinematography, the subjective impression conveyed is the primary and, in fact, the only criterion of accuracy in photographic color reproduction. Furthermore, it is not unambiguously correlated with objective evaluations (spectral and colorimetric evaluations, for example), since it very much depends on many variable factors that are assumed to be constant in an objective evaluation. Of these factors the most important ones are related to the properties of the image itself and to the conditions of exhibition (for example, the illumination and brightness of the image, the scale of enlargement or reduction, and the surrounding background and its chromaticity), as well as to the properties of the eye during viewing, particularly color adaptation. The conditions of comparison are also important, in particular, whether the image is viewed under the same conditions as the subject and whether both are viewed at the same time or separately. The basis for a qualitative evaluation, if necessary, of the psychological accuracy of photographic color reproduction may be said to be the threshold of color discrimination—the minimum change in color that corresponds, under given conditions of observation, to the first barely discernible change in visual perception.