Eliminating color casts and moire

The principle and practice of multi-color machine color arrangement We all know that, in the color platemaking process, the network line angle should be determined according to the primary and secondary colors of the original. Since the 45 degree angle has a special sensitivity to human sight, the main color plate of the original document is made into a 45[deg.] angle, and the other color angles are set to 15[deg.], 75[deg.], and 90[deg.] in sequence. In the process of printing and restoring, the dots and dots are crossed at different angles to form various patterns. Among them, the cross-shaped pattern has the best color rendering effect, and the hat-shaped pattern takes the second place. When a four-color plate is grouped, only strong black, blue, and red energy form a pattern, and yellow is a weak color, which does not act as a texture, and only plays the role of color change. Therefore, when determining the four-color screen angle in the platemaking process, the black, blue, and red three-color screen lines should be at an angle difference of 30°. The result is not only beneficial to the color rendering effect, but also prevents the color screen lines from differing by 15 °, causing the appearance of a moire failure.

Even in the platemaking process, we chose the above-mentioned various network line angles, but when the four-color melter is arranged for printing, if the color sequence is not properly arranged, the angles of the plate lines of the adjacent two color groups may still differ by 15°. There is a possibility that color casts and moire may occur, and it is also not possible to achieve a better print reproduction original.

For example, the landscape painting manuscript is often biased toward blue. According to the principle of making the main color plate of the manuscript 45°, here we set the blue line angle to be 45°, followed by 75° for the red plate, and 15 for the black plate. °, the yellow version is 90°. In the four-color offset printing press, the color sequence is arranged in order of black, blue, red, and yellow, and the adjacent red and yellow versions are 15 degrees apart, especially the low-key areas where the dots are above 75 degrees. As long as the paper is slightly misaligned during the transfer and imprinting process, it is prone to mis-alignment, causing color casts and mottled spots and other ills.

According to the theory of the original color of the original color (determined) to determine the angle of the screen, as well as the problems that often arise in daily production operations, in order to better solve the problem of color cast and moire on a multi-color offset press, the solution is:

First, we should check the source of the process design. After the manuscripts of the enterprise and the production workshop are accepted, the primary problem is to determine the color version of the 焉45° cable according to the main color of the manuscript; then determine the angle of the other cable and the printing of the four-color offset press. Color sequence. For example, for the main blue-and-green landscape paintings, the blue version is set to 45°, the black version is set to 15°, the red version is set to 75°, and the yellow version is set to 90°. Set to black first, followed by red, blue, and yellow. We believe that during the printing process, the angles between adjacent two-color network cables differ by at least 30°. In accordance with the sequence of the above-mentioned color screens, the black-red color is different by 60°, the red-blue color is different by 30°, and the blue-yellow color difference is 45°. Printing sorting can effectively prevent the occurrence of color cast and moire.

Similarly, red masters the main color of the original, after the red version of the wind is set to 45 °, the process designer should arrange the red version in the third color group printing; and the provisions of the black version of the cable 15 °, in the first color group printing; Followed by the blue version of the network cable 75 °, printed in the second color group; yellow version of the network cable is 90 °, arranged in the fourth color group printing is more appropriate.

It can be seen that the above-mentioned complementary relationship between the angles of the screens and their color sequential arrangements should be introduced to the attention of the process technicians of the enterprises, and through the organic combination of theory and practice, better grasp this rule. Prevent the occurrence of unnecessary color casts and moire.

Reprinted from: Longjiang Printing Network