Four-color printing should pay attention to what issues?

Four-color printing is the most basic printing method in brochure printing and its requirements are very high. For professional printers or companies, understanding the color of printing is a very important basic skill. What are the rules for the matching of colors in printing?

Pure color can be printed with one primary color or two primary colors. The size of the chroma depends on the number of primary inks. The greater the number, the higher the chroma, such as the pale solid series and the concentrated solid color series and the 28-30 page two-color series. colour.
The hue obtained by printing with two primary colors depends on the relative proportions of the two primary colors, and the hue of the printed color is biased toward a large proportion of the colors, as indicated by the color circles on pages 10 and 13:
Adding a third primary color to the solid color of the two primary colors causes the chroma of the process color to become lower and the brightness to decrease accordingly, while the color tone of the process color is basically unchanged because the three primary colors are mixed to form an achromatic color. The effect is similar to the effect of printing with a smaller proportion of color and a certain amount of black ink, such as a light-colored series and a dark-dark series and a three-color printing color.
Increasing the number of black inks on the basis of color will not change the hue of the mixed colors, while reducing the lightness of the colors while also lowering the chroma, such as the two-color series on pages 31-33 and the three-color series on pages 44-70. And the four-color series of colors;--The printing of three color primary colors in close proportions yields a low-saturation color that approximates color, close to the color printed in black plus a certain amount of color. In color printing, this feature is often used to reduce the amount of color inks, known as Undercoat Removal (UCR) and Gray Component Replacement (GCR).
On the one hand, in the four-color printing technology, the color of the picture is the most important issue to be paid attention to. Therefore, we must pay attention to the color problem in the four-color printing.
1. There is a row of blue words on the hollow yellow floor, then on the yellow version of the film, the location of the blue word must be empty. On the contrary, the blue version is also the same. Otherwise, the blue thing is directly printed on the yellow, and the color will change, and the original blue word will turn green.
2. There is a line of black characters on a red base plate, so in the red version of the film, the position of the black characters should not be hollowed out. Since black can suppress any color, if the black content is hollowed out, especially for some smaller characters, a slight error in printing will lead to white edges, and the contrast between black and white is relatively large and it is easy to see.
3, four-color black This is a more common problem. Before outputting, it is necessary to check the black text in the publication document, especially the small characters. It is not only on the blackboard, but it should not appear on other three-color editions. If this is the case, the quality of the printed product will be discounted. When the RGB graphics are converted to CMYK graphics, the black text will definitely change to four-color black. Unless otherwise specified, it must be processed before the film can be exported.
4, the picture is RGB mode
When the RGB mode picture is output, the RIP system will automatically convert it to CMYK mode output. However, its color quality will be greatly reduced, and the printed products will be light in color and will not be bright. The effect is very poor. The picture is best converted to CMYK mode in photoshop. If it is a scanned manuscript, then it must go through the process of color correction and the picture can be used.