UCR

UCR or Under Color Removal is used whenever large percentages of three process inks are together to form a color, resulting in a substantial neutral or grey component. That is to say, past a certain point, adding more of one of the C, M, or Y process colors simply darkens the result. So, instead of simply adding more color, the UCR formula uses black ink to replace a partial amount of the other process colors in the shadow areas and in neutral colors. For example, in a screen tint build of 50% cyan, 40% magenta, and 45% yellow, magenta acts as the greying process. So, the 40% magenta value indicates the largest potential amount of black that can be added in place of a percentage of some of the other colors.

GCR

GCR or Gray Component Replacement is a specialized form of under color removal which involves a more general replacement of chromatic inks – not just the close to neutral ones as with UCR. In a GCR separation, black is substituted for a partial amount of the process colors in all areas where the three chromatic colors are present – even in lighter tones. That added range of color where CMY can be replaced with black is the key to how GCR reduces CMY ink usage.

The difference in the range of the black channel makes it fairly easy to determine whether UCR or GCR was used to create a particular CMYK separation. With a UCR separation the black printer appears as a “skeleton” image usually missing tones around the 0%-30% range while the CMY looks very colorful. In contrast, the black printer in a GCR separation looks more like a full range greyscale image while the CMY looks washed out.

Color Gamut Correction / High DMAX / Total Ink Coverage

We set up the color reproductions so that the colors are implemented efficiently within the printable density ranges so your brand’s identity is printed accurately. Both UCR and GCR separation techniques use a defined parameter to limit the maximum amount of ink that will be used in the darkest part of the image. This maximum total dot percentage is referred to as either TIC (Total Ink Coverage) or TAC (Total Area Coverage) and is determined according to the type of presswork and substrate that the images will be used for.

The combined value of all CMYK inks for a particular area or object cannot exceed a specified amount, or ink may not transfer effectively and printed sheets may not dry properly. This specified amount, referred to as Total Area Coverage (TAC), typically is limited to 300 for offset lithography using coated paper. Technically speaking, the TIL/TAC/TIC value should not exceed 300, depending on print process.

Spot Colors

UCR or Under