In
four-color printing
The CMYK color model (also known as process color, or four color) is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. The abbreviation ''CMYK'' refer ...
(or more), under color addition (UCA) is a technique for darkening areas of the printed image by adding colored inks. It is meant to achieve the same results as
under color removal
In printing, under color removal (UCR) is a process of eliminating overlapping yellow, magenta, and cyan that would have added to a dark neutral (black) and replacing them with black
Black is a color which results from the absence or comple ...
, but from a different starting position.
Under color removal replaces colored inks in selected areas with black ink to achieve a darker appearance, whereas with under color addition, small portions of the three colors are added to these areas instead of, or in addition to, using black ink.
UCA is used to reduce the speckle effects of dithering, especially with very light colors. Without UCA, a very light grey would consist of infrequent black specks that might be individually noticeable. With UCA, the specks are lighter and 3x more numerous.
Printer drivers sometimes make the use of UCA somewhat configurable, disabling it when set to a mode intended to save ink.
Graphic designers (or anyone else creating artwork for print output) are cautioned to be wary of using UCA. Used wrongly, the effects can be disastrous, rendering poorly printed images and yielding the problems associated with
rich black
Rich may refer to:
Common uses
* Rich, an entity possessing wealth
* Rich, an intense flavor, color, sound, texture, or feeling
** Rich (wine), a descriptor in wine tasting
Places United States
* Rich, Mississippi, an unincorporated comm ...
. On the other hand, UCA can breathe life into a flat image, adding depth and richness to the shadows.
UCA is generally best used in conjunction with
under color removal
In printing, under color removal (UCR) is a process of eliminating overlapping yellow, magenta, and cyan that would have added to a dark neutral (black) and replacing them with black
Black is a color which results from the absence or comple ...
- in order to remove some, but not all CMY ink from black areas.
{{DEFAULTSORT:Under Color Addition
Printing