The paper is printed primary substrates, paper quality will directly affect the quality of the print. The different paper surface gloss, surface strength, whiteness, the absorbent and smoothness, scalability, etc. there is a large difference, even in the case of the same printing conditions, with an ink printing on a different paper will produce different color effects. Level and the color of the surface properties of the paper directly the performance of the image tone, decided to the platemaking tone color kind of positive data. Therefore, in the actual operation, it should be fully grasp the printing characteristics of the paper, is determined according to the performance of the paper of printing parameters to improve the quality of the printed materials.
Depending on the paper performance to determine the number of screen lines
The common screening lines 80,100,120,133,150,175,200,300 lpi and other performance of the paper is an important factor in the actual selection. The paper smoothness and roughness of the surface properties of the decision they are not the same as the requirements of the screening lines. A high degree of surface smoothness of coated paper or senior calender Paperboard, is able to reproduce the finer dot, so the higher the number of screen lines, and can be set to 175 to 300 lpi; offset paper surface coated paper and coarse screening lines between 120 ~ 150lpi; newsprint surface more rough too small outlets form a broken edge, or fall entirely on the concave, so you should use a larger screen printing, its screening lines at 80 ~ 33lpi.
To determine Black / White paper performance
At the highlight of the printing image, generally in the 3% to 5% of the highlight region is not printed out, and that prints the high-light portion is formed by the color of the paper. The whiteness of the paper will affect the screen the main bright at the color brightness and saturation, thereby affecting the color contrast of the screen. Similarly, the texture of the paper is also useful, newsprint for the porous material, the ink can easily be fibrous absorber, so that the printing surface to produce a high degree of light scattering, so that the printing density is reduced, black at not black, smooth, coated adsorbed on the surface of paper, ink and light scattering very little, so that the dark tone darker.
Newsprint, printing gloss, directly affect the printing ink color drift; surface whiteness and print contrast; smoothness, ink spreading strong, so good newsprint screening lines of more than a 133lpi. Given these characteristics, the black / white field scaling value white field can be a small area network (C = 0%, M = 0%, Y = 0%, K = 0%), black field calibration is C = 62 %, M = Y = 56%, K = 75%, the total amount of the ink trapping should be small as 250.
Coated paper surface with good smoothness, whiteness and light reflective ability, printed on coated paper ink diffusion type of dots, dot gain rate can be controlled at around 15%; printed on coated paper prints color saturation, bright colors, to reflect better the level and contrast. The high Guangneng printed 2% dot the shadow dot overprint total about 340, and the screen lines can reach the 200lpi more, the density contrast can reach 1.8. Therefore, for coated paper, and some manufacturers white field outlets as C = 95%, M = Y = 3%, proofing drying out the minimum number of outlets and printing paper can print out the minimum number of outlets have a relationship, the calibration of the black field is substantially C = 95%, M = Y = 85%, K = 75%.
The image White Point, paper color as a reference point to adjust the white field, the paper anti-regulation to CMYK colors outlets is less than 3% or less can
According to the paper properties determine the color separation parameters
A dot gain compensation like being set
When the ink is transferred to the paper surface under pressure, due to the absorbent paper, the ink to spread around the permeate generated dot gain, so that the entire image becomes darker. Obviously, for different quality of the paper will produce different dot gain effect. The paper is absorbent, the stronger the greater the value of dot gain, specifically, newsprint, coated paper minimum. The dots formed by the paper properties increases generally exponential expansion law in the prepress process, it must be the impact on dot gain compensation.
Dot gain values ??are different for different size outlets. General high-profile, dark tone dot gain value is small, the Midtones the dot gain value larger. Generally recommend better default settings, such as coated paper printing default value of 17%, offset paper, compared with about 22% of newsprint for about 30%.
Second, choose a color separation type GCR, UCR
Using GCR easy to keep the gray balance, reducing the ink overprint total, so the ink dry faster, improve the printing speed. The black version of the Quality plays a pivotal role in the entire printing GCR general originals recommended. Special originals, such as high school tone color more rich dark tone of the image, and can also use the UCR. In short, to be flexible.
Total ink set
The printing characteristics of the paper, as well as the high speed of the rotary printing, determines the total amount of the ink is not too high. The foreign data display: newsprint black is generally controlled at 240% to 260%; coated paper printing total amount of ink is generally controlled in the range of 280% to 320%; offset paper printing total amount of ink control 300% to 340%. This value is set by each process, completely dependent on the dot gain when printing. Dot gain serious, you need to reduce the value, otherwise the darkened part will paste dead in the darkened serious level of losses; dot gain is basically normal, may be appropriate to increase the value, the darkened part of the full color, full performance darkened the regional level, and is conducive to the overall tone reproduction. In addition, it should be selected depending on paper their compatible ink.