The process of printing (mainly refers to Offset Printing) is to decompose the tonality of successively tuned originals into four monotone meshes of yellow, magenta, cyan, and black, and to superimpose each mesh into a monochromatic version. To achieve color reproduction. Because of the ever-changing colors of prints, it is impossible to examine and control different levels of each color, so people have explored the use of methods to test neutral gray balance to control the reproducibility of printed colors. Usually, under the certain printability, with yellow, magenta, and blue three-color version of the screen ladder, from shallow to deep according to a certain ratio of overprint combination of overprint, trapezoidal color after the ladder loses its hue and saturation, but only different Brightness of the gray, this process is called the printed gray balance. Since gray has neither hue nor saturation in the three attributes of color and is a neutral color (also referred to as "achromatic"), it is sometimes said that the gray balance is a neutral gray balance.
The function of gray balance is to indirectly control all the hue on the entire screen by controlling the gray part of the screen. It is a measure of whether color separation plate and color sleeve are correct or not. It is the principle that all processes in the entire process of data reproduction and standardization comply and implement.
First, the principle of gray balance
Theoretically speaking, if the two colors are complementary to each other, then the two colors are mixed in the proper proportions, and the color will change to a neutral color. This means that when two colors are complementary to each other, they are mixed. There is also a balance issue. Otherwise, it will not appear neutral grey. However, it is not the balance of the three primary colors, but the balance of the two complementary colors. In fact, the two complementary colors are converted into neutral gray after being mixed in appropriate amounts, which is the basis of all gray balance. The gray balance of the three primary colors is also a method of using color synthesis and finally they are attributed to the balance of complementary colors. We will mix any two primary colors, yellow, magenta, and blue, to produce a color that is always complementary to the third primary color:
Yellow + Magenta = Red, and Blue is a pair of complementary colors;
Magenta + blue = blue-violet, and yellow are a pair of complementary colors;
Green + yellow = green, and magenta is a pair of complementary colors;
Therefore, the principle of printing gray balance of three primary colors is a specific expression of the complementary color law.
Second, the necessary conditions for achieving the gray balance
It is conditional to achieve a grey balance. Each of the yellow, magenta, and cyan inks participating in the balance has a definite color and saturation, which are necessary conditions for determining whether the synthesized colors are balanced.
1, the effect of color balance. After a mixture of several different colors, it is possible to obtain a neutral gray balance. Take the three colors red, orange, and yellow, no matter how you mix, you can't reach neutral grey. This is because in these three colors, orange is not an independent color, it can be obtained by mixing red and yellow, and red and yellow are not complementary colors and it is impossible to produce neutral gray. Obviously, the hue of each color involved in the mixing, either they are complementary colors, or they can be mixed to produce a complementary color. Only in this way, the mixture of hue can produce a gray balance. The hue of printing three primary colors meets this condition. However, any of the three primary colors of yellow, magenta, and cyan that are offset in printing will affect the original balance. Hue shift is color shift, which is an important factor in determining the balance of the three primary colors.
2. The influence of saturation on the balance, the amount of each color participating in the gray balance should be appropriate. This requires the participation of balanced colors, neither more nor less. Even if the two complementary colors must also be equal amounts of mixing to be balanced, if the two color amounts are not equal, the hue of the mixing result will inevitably shift to the hue where the colors are more. The color saturation in printing is expressed in terms of the density or dot area ratio.
Source: Jiangsu Publishing School Liu Ningjun