Why gray scales are used in the image separation process?

The gray grading scale used in the image separation process is a continuous ash grading scale. The gray scale is a measuring tool for measuring the tone of a color separation sheet, and it has reflection and transmission points. Respectively used for reflection and transmission. Gradual ash ladder rule is generally composed of 21 blocks (also 10 or 30 steps) with the same area and equal density difference (0.15 in each stage). There is no stepless gray scale in the density of gray scale. The gray ruler is used to represent the original, and the density of the original is different. Therefore, when the same gray scale is used for different originals, it is necessary to find out the same density area as that of various kinds of originals and to control the original copy. The method is to measure the high, medium and low density values ​​of the manuscript first to find out the corresponding high, middle and low points on the scale to serve as the calibration duty, so as to control the reproduction of the tone and make the original contrast and the ash ladder. The three points of the ruler are basically the same. Only in this way can the tone be controlled correctly. Gray scale can be used as the basis for the balance of the three primary colors when color separation and screen are added. After the final print copy is completed, the copy of the original can be judged according to the grey reproduction of the gray scale, and the compression and pulling of the tone can be evaluated.