Under Color Addition
A method of darkening areas of a printed image by adding colored inks, used when making color separations from RGB to CMYK data.
The process works as follows: cyan, magenta and yellow portions are added in shadows and black is accordingly removed.
Under color addition is generally done to make the blacks look darker which increases the tonal range.
Not all achromatic portions, however, are replaced with black, rather a portion of black is generated according to the principle of chromatic composition from the primary colors cyan, magenta and yellow.
The aim is to enhance neutral image depths (gray tones) where the density of black is insufficient.