Neutral gray balance in color reproduction (bottom)
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Fourth, the relationship between the depth of the black version and the amount of background removal
The depth of the black plate and the amount of background color removal are closely related, the amount of background color removal is large, and the black plate should be deep; conversely, the amount of background color removal is small, and the black plate should be shallow. At the same time, the length of the black tone should be determined according to the length of the dark density of the original. The dark tone density range is long, the black version should be long, the dark tone density range is short, and the black version should be short. Neutral gray balance is an important condition for color reproduction and restoration of originals. It is also a technique that is difficult to master in plate making and printing, because Y, M, and C three-color inks have a certain difficulty in reproducing neutral gray balance.
Fifth, he main factors affecting the neutral gray balance control of neutral gray balance:
1 color characteristics of the ink.
2 The ratio of the three primary colors.
3 printed color sequence.
4 paper performance.
5 process operations, etc.
1. The color characteristics and variation of the ink, the control of the neutral gray balance, and the factors affecting the neutral gray balance, we must first understand the law of color change. 1 Three primary color inks can be mixed in black in a certain ratio. 2 After the three primary color inks are mixed, they are approximated black, and with different proportions of the thinner, then neutral ash of different colors is obtained. 3 The three primary colors are mixed in different proportions to obtain inter-color or complex color of different hue, and the hue is biased to a large hue. 4 The two primary colors of ink are mixed in equal amounts to obtain a standard color.
2. Neutral gray balance requirements for ink, 1 high transparency: When the ink is applied into a uniform film, the degree of coloration of the underlying color of the substance that withstands the ink film, the clearer the background color is displayed, the higher the transparency of the ink. 2 fine pigment particles: printing high-grade refined products to fine pigment particles. 3 strong tinting strength: the tinting strength of the ink is an amount indicating the color strength or concentration of the ink. For the ink of the same hue, the tinting strength depends on the dispersion of the pigment on the binder, and the higher the degree of dispersion, the stronger the tinting strength; It also depends on the content of the pigment, and the higher the content, the stronger the coloring power. 4 Lightfastness: Under the action of light, the color of the pigment will change color and fade to varying degrees, which is lightfast. 5 color efficiency is high: color efficiency is a comprehensive indicator of ink color difference and gray level. 6 Chemical stability: The color of the ink will change under the action of some chemicals. Therefore, the ink is required to have good chemical stability, water resistance, acid and alkali resistance, and ethanol resistance.
3. The relationship between the performance of the paper and the neutral gray balance, the quality of the printing enterprise is greatly affected by the raw paper, the ideal paper whiteness is 100% reflectivity, and the total reflection is 380-700 nm. In the process of plate making and printing, it is necessary to consider "different from paper" and use the appropriate process content to adapt to the paper used, especially in terms of the thickness of the dots, the color of the dots, and the contrast of the layout.
High-grade and exquisite offset printing papers include domestic coated paper, offset paper, newspaper and imported coated paper, egg-pattern paper, cloth paper, etc., due to paper tightness, whiteness, paper absorption, smoothness, and flexibility. The curve that produces the reproduction tone reproduction is also different. The level of printing on the coated paper is very rich, and the level of printing with offset paper is relatively dull. The same is the 157g / m 2 coated paper due to different origins, domestic paper or imported paper also has a certain gap.
The high-quality paper with low absorption, high whiteness and high smoothness of paper has an ideal reproduction curve, the amount of ink is thin, and the color is still vivid.
4. The relationship between printing color sequence and neutral gray, the monochrome offset printing machine adopts the order of Y, M, C, and K. First, the ink with the lowest transparency is printed in the first color, and then the ink with high transparency is printed. The order of the color sequences is arranged according to the transparency of the ink. At the same time, the viscosity of the ink is also considered. Since the viscosity of the Y ink is small, the back surface of the printed matter can be prevented from being sticky; the light color is placed on the front side, and it is easy to clean the ink roller; it is also convenient for four-color overprinting accuracy. The multi-color offset printing machine adopts the inverted color sequence K, C, M, Y. Since the multi-color machine is wet and wet, the printing ink is overprinted without the oxidized conjunctiva drying, and another color ink is overprinted. The viscosity of the four-color ink is K>C>M>Y, which satisfies the requirements of the four-color machine. The color sequence of the multi-color machine is gradually lowered from high to low, and the viscosity is high. Printing, stacking fastness is better.
In addition, the multi-color machine color sequence arrangement takes into account, the transparency is the lowest, the black ink has the lowest transparency, that is, the darkest, as the outline of the picture is thicker, so it should be placed on the front to make the transparency high. C two colors are placed on the back to make the whole picture vivid.
Different color order arrangements have a greater impact on the neutral gray balance. Different color sequences will directly affect the quality of printed products and the color tone. In the actual production, comprehensive analysis is needed to introduce some of the printing processes. The variable factor is considered a little more. In the color sequence arrangement, the color sequence should be arranged according to the effect of different types of originals and the requirements of the customer, in order to achieve the perfect reproduction of the printed matter.
Usually, the color cast of several inks after overprinting should also be considered: M, C, and Y are easily greenish after overprinting, C, M, and Y are reddish after overprinting, and C, Y, and M are easily reddish after overprinting, M. Y, C is brownish green after overprinting, Y, C, M is superimposed after printing, and Y, M, C are blue-green after overprinting.