Contrast is (from the French contraste - the opposite <from the Latin contra - against)
the difference between the maximum and minimum optical densities in the photographic image.

Contrast

~~ of photographic materials: gradient (tonal) characteristic of photographic material, determined by the ability of its photosensitive layer to transmit the brightness distribution of the shooting object by the corresponding distribution of the optical density of the photographic image field.

Expressed by the gradient of the characteristic curve - medium or maximum (contrast ratio); the steeper the characteristic curve, the higher the contrast of the photographic materials. It is determined not only by the properties of the photosensitive layer of the photographic material, but also depends on the conditions for its development (composition of the developing solution, its temperature, duration of development, etc.).

A decrease in contrast in relation to the norm (for example, due to underdevelopment) leads to a deterioration in tone reproduction, a decrease in differences in lightness and chromaticity of the displayed colors, an increase (for example, due to overdevelopment) - to the disappearance of tonal and color differences in the highlights and color differences for areas with medium brightness.

 

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