The pre press screening of documents is usually done by automatically converting the computer to CMYK mode for publication. Even with the best imported plates, the results are sometimes unsatisfactory. CMYK four-color printing is a Planographic printing method that uses rose red, pure yellow, blue and black ink to achieve full color reproduction according to the principle of subtractive color mixing. In theory, four color printing can obtain thousands of colors, but due to the printing process; Outlet; Due to deformation errors and limitations in visual recognition thresholds, there are significant color phase shifts and misalignment phenomena in four color printing on watermark machines.

The cardboard box is also commonly used with yellow paper, which lacks the contrast of a white background and makes the pattern appear darker and less shiny. The more printed, the darker the color. Therefore, we can use spot colors to replace the three primary colors, reduce the number of colors, and use Complementary colors to overprint the black effect; And the highlight part can reduce color contrast, and even use blank spaces without printing any dots.

Although CMYK is loyal to the original manuscript, it is not the best result when it comes to screening. The plate making cost is high, the printing difficulty is high, and the finished product effect is dark and color biased. Even if the equipment is well-equipped and not color biased, it can be considered excessive processing (i.e. excessive precision processing is waste), because there are simpler production methods.

In cases where the effect is similar, using spot colors to match screen colors can greatly reduce plate making costs and bring more competitiveness to business orders. Reducing the number of colors in the pattern can reduce the difficulty of registration, save printing machine time, and improve work efficiency.

By using spot color screen matching, printing colors can be more easily controlled, and colors will not deviate or shift due to deformation errors and pressure changes during the screen rotation process. It can reduce the impact of positioning errors on pattern clarity.

As for which image to use and how to use it, it depends on the specific analysis of the problem. Some images can only be made using CMYK, but if it is found that they can be printed in three colors, then four colors are absolutely not needed. If they can be printed in two colors, then three colors are absolutely not needed. In today's world where even a penny is love, we should pay more attention to frugality.