"UCR" and "GCR" Separation Processes (1)

The key to color reproduction is color reproduction. To faithfully reproduce the original color, correct color separation in photoshop is very important. "UCR" and "GCR" are one of the powerful tools for controlling color separation provided by the Photoshop software. It directly affects the result of converting the file mode from RGB to CMYK, and also controls the amount of ink on the printing press and the degree of black generation. After the “UCR” and “GCR” in photoshop, color separation and adjustment are completed, so that the stable reproduction of colors is guaranteed.

"UCR" and "GCR" are two color separation modes in the separtion setup of photoshop. GCR Gray Component Replacement means that the achromatic structure is intended to replace the gray component, and UCrunner Color Removal means that the background color is removed. Both methods can use black ink instead of color ink, that is, reduce the ink volume of the yellow, blue and green three-color editions, and accordingly increase the black dot area. The theoretical basis for using “black ink instead of color ink” is the gray balance, and the combined ink can produce gray, ie, achieve the gray balance. For example, 80% cyan, 71% yellow and 71% magenta are equivalent to 80% black, so you don't have to print 222% of the total ink (80%+71%+71%) and only 80% black ink .

According to the principle of gray balance, the color ink composition added to black can be removed, leaving the rest. For example, the colors are 90% cyan, 71% yellow, and 76% magenta. Only 10% cyan, 5% magenta, and 80% black are printed. The gray part of the color (80% cyan, 71% yellow, 71% magenta) was replaced by a black plate, and the rest was printed with a separation plate.

Replacing color with black reduces ink usage and costs. You can also open the image density contrast, rich dark tone level, to prevent prints dirty and adhesion, is conducive to printing. Because the specific printing conditions only allow a certain amount of ink to cover the paper. If the ink is excessive, it may not dry properly, stick back, or splash. The total amount of ink coverage is related to the printing speed, the type of printing press, and the quality of the substrate. Usually the maximum amount of ink is between 260% (newspaper) and 350% (high-quality sheetfed). Therefore, we can only use the “UCR” and “GCR” color separation process correctly to print rich and vivid colors with limited total printing ink coverage.

The following are specific applications of the "UCR" and "GCR" color separation process.

First, UCR separation process

UCR refers to removing the color of the gray area, that is, only the neutral gray area of ​​yellow, blue, green instead of black. Among them, the Black Int Limit is set to about 85%, and instead of gray, black is used instead of a small amount. Therefore, the three-color ink amount is still relatively large, which is suitable for color separation of a document with a more vivid image. Traditional electricity separation plate making process uses UCR separation. However, this method can not adjust the amount of black ink to replace the color ink, as well as black highlights and dark tone.

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