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IMAGE PROCESSING
24 February, 1999
(5) UCR (Under Color Removal)
Principle
B
k
B
k
B
k
A259D525.WMF
Obtaining the right colors using YMC toner addition does not always work perfectly.
For example, if the same quantity of toner for each color (YMC) is put on the paper,
ideally the image should become black, but in reality it becomes a dark color, such
as dark blue.
To compensate for this, an equal portion of the common ID value for each color is
subtracted. This reduces the amount of color toner on the paper, and a
proportional amount of black toner is added. This process is known as UCR.
The UCR ratio is the percentage of the common ID value for YMC that is
subtracted and converted to black. In the above example, where the UCR ratio is
100%; the entire common ID value is subtracted from Y, M, and C, and converted
to K.
In actual use, the UCR ratio depends on the color mode and the image density. For
example, when the UCR ratio is 95%, 95% of the entire common ID value is
subtracted from Y, M, and C, and converted to K.
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