Today's printing presses are generally screen printing, and four-night overprinting is the most common. You can see four CMYK channels in PS, if the image is in CMYK mode. It is conceivable to use these four channels to make four films, and then stack these four films together to see the light. This is probably the principle. According to the distribution of the four colors of red, yellow, blue and black in the picture, four films are made. The silk screen plate is generally made by the principle of sun exposure, and then the silk screen plate is used to print one color. After drying, the second color is printed until the four-color printing is completed. At this time, some colors are stacked together. Such as orange, printed once red, once yellow, it is orange. Although it is theoretically possible to use red, yellow and blue tones, it is not feasible in practice, because the mixing of colors will lead to a decrease in the degree of vividness, and the final result is a gray, so on the basis of the three primary colors of red, yellow and blue, add a color version. In PS, the four colors of red, yellow, blue and black are mixed together, but this setting will not work during printing, because the vividness will be reduced when mixed together. So generally only the black and blue channels are used to print the black part. In the same way, printing or printing cannot print very bright colors, so the color range of RGB mode is much larger than that of CMYK mode. When picking a color in PS, a triangular warning sign will often appear next to the color, which means that the color cannot be used.
in printing.
