UCA , under color addition

UCA, under color addition (In French ajout de sous-couleurs) process within achromatic composition to compensate for its deficits in brilliance and contrast; in this process, small quantities of the under colors CMY, which had previously been reduced to zero, are increased again in the “under colors” (neutral image depths and three-quarter tones), leading to an improvement in black. This also leads to a smooth transition to the chromatic color separation with UCR.