GATF color copy test chart function

The setting of printing parameters is a very important issue. Attention must be paid to the prepress production regardless of the printing conditions. It must be a failure; only respect the objective conditions of printing, such as the quality of the ink paper, the quality of the media. The resolution, the performance of the press, and other factors can make our reproduction ideal. Therefore, some printing must be done before copying the original. The effective method is to copy GATF on stable Heidelberg, Roland, and Beiren four-color printing presses with certain inks and papers. From this we shall draw: the dot gain rate, the CMYK overprint tristimulus value, and the appropriate Overprint ink total value.

The following is a brief introduction to the GATF color copy test chart, divided into six regions according to the map function: 1 simple color wheel chart for identifying colors and detecting color reproduction; 2 contact copy control standard paragraph, can be used to detect the sun The changes in the printing process during the printing process; the comparison of the line counts of the three outlets is used to select the matching reference of the screen lines and the suitability of the paper, and it can also reflect whether the reproduction of each color version is normal or not; 4 Neutral gray balance control chart of the three primary colors; 5 gray balance card, according to calculate the Y, M, C ratio; 6 proofing control bar. Through copying and copying of the GATF test chart, we can know the transmission of the dots from the film to the PS, the appropriate number of screens, neutral gray balance, and the performance of the machine. This ensures that printing factors are deterministic from printing to printing. Next, in the custom CMYK, you can set the ink color, color separation parameters, dot gain rate.

In the Photoshop 6.0 use the file drop-down menu to set the color to enter "Custom CMYK", select the custom in the ink color box, through the real block on the GATF copy map, three primary colors yellow (Y), product (M) , Blue (C), Three Color Red (Y+M=R), Green (Y+C=G), Blue (M+C=B), Synthetic Black (Y+M+C), Black (K) Eight color patches and paper white, respectively using a spectrophotometer to measure the tristimulus value XYZ of each color block and the paper used, and then use the formula x = X / (X + Y + Z) and y = Y / (X + Y +Z) Calculate the chromaticity coordinates x, y, respectively, where Y is the luminance coordinate, the value range is 0 to 100, and the x and y values ​​are 0 to 1. Then fill this in the box corresponding to "ink color".

After the data is filled in, the color of each color block will change, and the nine color blocks printed will be compared with the colors displayed on the screen. If the measurement is calculated correctly, the colors will be basically the same. If there is any difference, the calculation may be different. To re-measure meter.

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