Neutral gray balance 0 in the hottest color reprod

Neutral gray balance in color reproduction (Part 1)

first, the concept of neutral gray balance

the reproduction of printed matter is color restoration, tone restoration, texture restoration and clarity restoration. The so-called tone is that colors are classified according to lightness. Colors are three variables. Neutral gray is a three-dimensional color space. Neutral gray is composed of three colors y, m and C. The three variables of color (hue, saturation and lightness) HV/C are represented, while neutral gray has no hue and saturation, but only the lightness of one-dimensional variables

we know that the primary colors R, G and B of color and light transition to the white field, while the primary colors y, m and C of pigment transition to the black field. In addition, four-color printing is limited by two conditions: first, only y, m, C and K inks can be used; Second, the ink layer on each paper is evenly distributed

neutral grey refers to a series of colors such as y, m and C, which absorb the same amount of R, G and B light, with only the change of lightness but no change of hue and chromaticity

when the three primary colors y, m and C of the pigment can be completely copied out after paying more attention to the maintenance place or overprinting in an appropriate proportion, especially in the rainy season, it is said that the three primary colors y, m and C have reached the neutral gray balance. The monochromatic density of three primary colors to obtain gray balance is called equivalent neutral gray density

second, emphasize the significance of neutral gray balance

1. Copy the gray of the original correctly

2. In plate making and printing, neutral gray balance is used as a measure to measure whether the proportion of three primary colors of ink is appropriate in color separation plate making and printing

III. balance between base color removal and neutral gray

1. The concept of base color removal, the so-called base color removal (UCR) refers to the removal of a part of the base color that forms neutral gray from the three primary colors y, m and C, that is, the approximate black base color formed by the superposition of the three primary colors y, m and C of the pigment, and replaced by black ink

for example, suppose that a certain color is overprinted by Y, m and C, and the area of Y point is 80%, the area of m point is 80%, and the area of C point is 100% (on the spot). If 80% Y and 80% m can overlap with 90% C according to neutral gray balance, black ink equivalent to 90% point area can be formed, Tighten the screws after padding. Then:

C = 80% y + 80% m + 100% C = 80% y + 80% m + 90% C + 10% C = 90% K + 10% C

2. The necessity of removing the background color, ① improves the printability: generally, it is used in dark tone. If the three primary colors y, m, and C are used in the dark tone area, the dot area is often very high. In high-speed multi-color printing, It is easy to cause process problems. If the background color is removed, the ink amount is greatly reduced and the printability is improved. ② It is beneficial to control the neutral gray balance during printing. ③ It is conducive to the drying of ink and reduces the overprint of Y, m and C primary color ink. ④ As the amount of Y, m, C color ink is reduced and the amount of black ink is increased, the cost is reduced, and the price of black ink is relatively cheap. ⑤ After adopting the high-speed multi-color printing machine, the biggest problem affecting the speed and quality improvement of the high-speed printing machine is the ink drying problem, that is, the speed of ink drying will directly affect the speed and product quality improvement of the high-speed multi-color printing machine. There are many ways to solve this problem, such as changing the composition and structure of the ink, improving the drying method of the printing machine, and improving the process, It can be concluded that the deformation of the sample can improve the concentration and gloss of black ink, reduce the ink amount of Y, m and C primary color ink in the non color part, so as to effectively thin the ink layer to speed up the drying speed, which is the fundamental reason for using UCR in color reproduction

3. Several points that should be paid attention to in background color removal

① background color removal generally works in neutral gray and near neutral gray areas of middle tone and dark tone

② correctly control the removal amount

③ master the control of removal point, that is, the range of removal control

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