How to eliminate color cast and moiré in color printing?
During the color plate making process, the angle of the cable should be determined according to the primary and secondary colors of the original. Since the 45° angle has a special sensitivity to the human line of sight, the original color plate of the original is made at a 45° angle, and the other color angles are set to 15°, 75°, and 90°. In the printing and reduction process, the dots and the dots intersect at different angles to form various patterns, wherein the cross-shaped pattern coloring effect is the best, and the hat-shaped pattern is second. When the four-color plate making pattern is formed, only the strong black, blue, and red can form a pattern, and the yellow color is a weak color, which does not function as a group, and only plays a role of color change. Therefore, when determining the angle of the four-color network cable in the plate making, the angle difference between the three strong colors of black, blue and red should be made at intervals of 30°, and the result is beneficial to the coloring effect and the difference of the color lines of the respective colors. °, causing the occurrence of a moiré fault.
Even in the plate making process, we chose the angles of the various colors mentioned above. However, if the color sequence is not properly arranged when the four-color melter is arranged for printing, the angles of the plate lines of the adjacent two color groups may still differ by 15°. There is a possibility of occurrence of color shifts and moiré defects, and it is also impossible to achieve a better printed original.
For example, the landscape original is often biased towards blue. According to the principle that the original color plate of the original is 45°, here we set the blue network angle to 45°, the red version is 75°, and the black version is 15 °, yellow version is 90 °. In the four-color offset printing machine, the printing color sequence is arranged in the order of black, red, yellow and yellow, then the adjacent red and yellow versions are different by 15°, especially in the low-key area where the dot is above 75°. As long as the paper is slightly misaligned during the transfer and imprinting process, it is prone to wrong nets, causing defects such as color shift and moiré.
According to the theory of the original color (tone) to determine the angle of the cable, and the problems that often occur in daily production operations, in order to better solve the problem of color shift and moiré on the multi-color offset press, the solution is:
First of all, it should be checked from the source of process design. After accepting the manuscript, the technical and technical personnel of the enterprise and the production workshop should first determine the 焉45° screen color version according to the main color of the original; then determine the screen angle of the other color plates and the printing of the four-color offset press respectively. Color order. For example, for the landscape color original with blue tones and greenish primary colors, the blue version of the network cable is set to 45°, the black version of the network cable is set to 15°, the red version of the network cable is set to 75°, and the yellow version of the network cable is set to 90°. It is first black, then red, blue, and yellow. We believe that in the printing process, the angles of the adjacent two color network cables differ by at least 30°. According to the order of the above-mentioned color network lines, the black→red phase difference is 60°, the red→blue phase difference is 30°, and the blue→yellow phase difference is 45°. Print sorting can effectively prevent the occurrence of color shift and moiré defects.
Similarly, if the red color is the main color of the original, after the red version of the wind line is set to 45 °, the process designer should arrange the red version in the third color group printing; and specify the black version of the network line 15 °, in the first color group; In turn, the blue version of the network cable is 75°, printed in the second color group; the yellow version of the network cable is 90°, and it is more suitable to arrange the fourth color group printing.
It can be seen that the complementary relationship between these network cable angles and their color sequence arrangements should be introduced to the attention of the process technicians of the enterprise, and through the organic combination of theory and practice, the law can be better mastered. Prevent unnecessary color cast and moiré defects.