Application of Undercoat Removal (2)

From the analysis of the above two cases, it can be seen that all the composite colors synthesized by the three primary colors necessarily include the background color, and the synthesized colors are the colors with lower lightness, while the single primary colors and the intermediate colors are not included. Background color.

After the background color is removed, the total coverage of the dot area in the unit area is greatly reduced as the coverage of the three-color dot sites is simultaneously reduced. From the point of view of improving the printability requirements of wet-press inks, it is advantageous to reduce the total coverage of the area, but it is not necessarily the lower the total coverage rate. The substrate used today - the surface of the paper cannot be very smooth, there are always pits and pores. When the surface of the paper is covered with ink, the ink must first be filled with these recesses and pores, and then a smooth ink film layer can be formed on it. If the total coverage is too low, it is not enough to form a smooth ink film layer. , it will reduce the maximum density of the color and the vividness of the color. Comprehensive advantages and disadvantages are generally not the removal of 100% of the background color, but the appropriate control of a removal, which is about 50%. If the paper is smooth, the removal can reach 60%; if the paper is smooth, the removal can be as low as 30%.

After the background color is removed, the amount of black ink corresponding to the background color is increased to assume the task of determining the color brightness of the original background color. The higher the percentage of background removal, the longer the tone of the corresponding black plate.

Third, the positive meaning of background removal

1. Good tone reduction If you do not use the background color removal, the total coverage of the mesh points per unit area cannot be reduced in the dark tone of the picture. By using three or four-color overprints to create the background, the dark areas are almost on the ground. Although the picture contrast increases, the level of dark tone does not come out and the outlines in the subtle areas are blurred. With background color removal, these problems are easily solved. As the tone of the dark version of the black version has been enhanced, the level of the dark tone region is mainly represented by the black version, making the level of the original dark tone region well represented.

2. Better printability In actual printing, when the total coverage of the dots exceeds 300%, the ink transfer condition deteriorates, and defects such as dot enlargement and reverse transfer are more likely to occur; when the total coverage is less than 200%, Because of the unevenness of the surface of the paper and the influence of the pores, light scattering occurs in the ink layer, which reduces the color density and vividness of the color. In general, it is better to control the total coverage of four-color printing outlets between 200% and 300%. Under-color removal can do this, so that printing has a better adaptability.

3. More suitable for the production needs of digital proofing

Today's digital proofing uses more economical and practical ink-jet printing methods. We know that ink-jet imaging requires more paper and ink, so the surface coating of proofing paper is particularly important. It should ensure that the paper can absorb a certain amount of ink, but it must maintain a certain amount of ink droplets. In fact, every proofing paper has a saturation limit that absorbs ink. When the ink limit is exceeded, the ink droplets will spread. Can not be well controlled, resulting in more ink, darker tone, image level and level, and seriously affect the image accuracy. In this regard, some digital proofing management software such as BlackMagic has applied the principle of undercolor removal to solve this problem.

Total coverage of BlackMagic's outlets is generally controlled within 260%, which varies according to the type of proof and ink, but is slightly lower than that of the printed ones. The use of the principle of undercutting the color has solved the problem of emulating the high number of amplitude modulation dots with the inkjet method. The problem.

In addition, the application of the under color removal increases the stability of the neutral gray, saves expensive ink and printing ink, and allows the dot gain to be well controlled. After successful application, it will find that its role is far more than these.

"Guangdong Printing"
Author: changs Beijing HiTech Group