Definition of undercolor removal (UCR)

variation of gray component replacement that reduces the amount of colored ink printed in areas where all three of the colors used in four-color process printing will be layered (see trapping). This is accomplished by reducing the density of the individual color separations. Black ink is substituted for the colored ink in an amount equal to the amount of colored ink reduced, because using too much ink would interfere with the trapping of the inks. Black ink costs less; therefore, UCR reduces ink expense. The primary benefit, however, is a sharper image with darker shadow areas and lighter highlights.