UCR-GCR
R
A Division of Sun Chemical Corporation
UCR and GCR
WHAT ARE THEY?
Volume XV June, 1996
Copyright US Ink 1996
U
ndercolor removal (UCR) and Gray Component Replacement (GCR) are techniques used in the separation of color for reproduction on a four color printing press. The two processes are different so we will discuss them separately.
UCR
Theoretically, when all the process colors cyan, magenta, and yellow are printed on the same piece of paper, they should absorb all the colors reflected from the surface of the paper and thus create black. However because of the nature of the pigments used, the combination of equal amounts of the three colors is brownish in nature. As a result, the black ink is added to the three colors to compensate for this deficiency. Undercolor removal is the process of reducing yellow, magenta, and cyan dot values wherever black is printed. In other words, areas that are 100% of the four solid colors are reduced to 60% yellow, 60% magenta, 70% cyan, and 70% black. This allows for a total coverage reduction from a 400% ink film to a
260% ink film. This would be described as having 260% UCR. This is an extreme example and is not necessarily real. Most halftone prints would not have this level of coverage.
However, the theory would be the same for lower coverage areas with a similar reduction possible. Some advantages of UCR are as follows:
1.
Black brings out better detail and contrast in the photograph than it is possible with the process colors. Black will make the white appear whiter and will add density, resulting in improved contrast in the shadow areas. Higher contrast usually also increases the image sharpness.
2.
Substantial amounts of the process colors removed from the areas where black is to be printed allows better ink trapping during the run. 3.
Process colors are more expensive than black. Substituting three process colors with black makes undercolor removal more
A Division of Sun Chemical Corporation
UCR and GCR
WHAT ARE THEY?
Volume XV June, 1996
Copyright US Ink 1996
U
ndercolor removal (UCR) and Gray Component Replacement (GCR) are techniques used in the separation of color for reproduction on a four color printing press. The two processes are different so we will discuss them separately.
UCR
Theoretically, when all the process colors cyan, magenta, and yellow are printed on the same piece of paper, they should absorb all the colors reflected from the surface of the paper and thus create black. However because of the nature of the pigments used, the combination of equal amounts of the three colors is brownish in nature. As a result, the black ink is added to the three colors to compensate for this deficiency. Undercolor removal is the process of reducing yellow, magenta, and cyan dot values wherever black is printed. In other words, areas that are 100% of the four solid colors are reduced to 60% yellow, 60% magenta, 70% cyan, and 70% black. This allows for a total coverage reduction from a 400% ink film to a
260% ink film. This would be described as having 260% UCR. This is an extreme example and is not necessarily real. Most halftone prints would not have this level of coverage.
However, the theory would be the same for lower coverage areas with a similar reduction possible. Some advantages of UCR are as follows:
1.
Black brings out better detail and contrast in the photograph than it is possible with the process colors. Black will make the white appear whiter and will add density, resulting in improved contrast in the shadow areas. Higher contrast usually also increases the image sharpness.
2.
Substantial amounts of the process colors removed from the areas where black is to be printed allows better ink trapping during the run. 3.
Process colors are more expensive than black. Substituting three process colors with black makes undercolor removal more