How to determine printing color separation parameters based on paper performance

1. The compensation sample of the dot increase is being set

When the ink is transferred to the surface of the paper under the pressure, due to the absorbency of the paper, the ink diffuses around when it penetrates, resulting in an increase in dots, making the entire image darker. Obviously, for different qualities of paper will produce different dot gain effects. The stronger the absorption of paper, the greater the value of the dot expansion. Specifically, newsprint is the largest and art paper is the smallest. The increase of the dots formed by the performance of the paper generally exhibits an exponential expansion law. In the process of prepress processing, it is necessary to compensate for the impact of the increase of the dots.

For dots of different sizes, the dot increase value is different. Generally, the increase value of high-tone and dark-tone dots is small, and the increase value of mid-tone dots is large. It is generally recommended to use the default settings. For example, when printing on coated paper, the default value is about 17%, offset paper is about 22%, and newsprint is about 30%.

Second, choose the color separation type GCR, UCR

Using GCR is easy to maintain the gray balance, reduce the total amount of ink overprint, make the ink dry faster, and increase the printing speed. The quality of the black version plays a decisive role in the entire printing. For general manuscripts, GCR is recommended. Special manuscripts, such as images with more high school tones and rich dark tones, can also use UCR. In short, be flexible.

3. Setting the total amount of ink

The printing characteristics of the paper and the high speed of rotary printing determine that the total ink volume cannot be too high. Foreign data shows that the total black volume of newsprint printing is generally controlled at 240% to 260%; the total ink volume of coated paper printing is generally controlled at 280% to 320%; the total ink volume of offset paper printing is generally controlled at 300% to 340%. The setting of this value is determined by each process, and it completely depends on the dot expansion rate during printing. If the dot expansion is serious, you need to reduce this value, otherwise, the dark tone part will be dead, and the mid-dark tone level will be seriously lost; if the dot expansion is basically normal, you can increase the value appropriately to ensure that the dark tone part is full of color and full performance The dark tone area level is conducive to the reproduction of the entire tone. In addition, it should also choose the ink that suits it according to the different paper.

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