We know that the three primary colors of R, G, and B transition to the white field, and the three primary colors of Y, M, and C, the transition to the black field. In addition, four-color printing is subject to two conditions: one is that only inks of four colors Y, M, C, and K can be used; the other is that the ink layer on each sheet is evenly distributed. Neutral gray refers to a series of colors such as Y, M, and C. They absorb R, G, and B light in equal amounts, and only change in brightness but not in hue and saturation. When the three primary colors Y, M and C of the color material are overprinted on the ground or dots in an appropriate ratio, the neutral gray scale can be completely reproduced. Then, it is said that the three primary colors of Y, M and C have reached the neutral gray balance. The monochromatic density of the three primary colors to obtain gray balance is called the equivalent neutral gray density. 1. Emphasize the significance of neutral gray balance 1. Copy the gray of the original correctly. 2. In plate making and printing, the neutral gray balance is used as a scale to measure whether the proportion of the three primary colors of ink is appropriate for color separation plate making and printing. 2. Background color removal and neutral gray balance 1. The concept of background color removal. The so-called background color removal (UCR) refers to the removal of a part of the neutral gray background color from the three primary colors of Y, M, and C, that is, the nearly black background formed by the superposition of the three primary colors of Y, M, and C Color, and replaced with black ink. For example: suppose a certain color is overprinted by three colors of Y, M and C, the area of ​​Y dot is 80%, the area of ​​M dot is 80%, and the area of ​​C dot is 100% (on-site). If neutral gray balance is used, 80% Y and 80% of M energy and 90% of C can overlap to form black ink equivalent to 90% of the dot area, then: C = 80% Y + 80% M + 100% C = 80% Y + 80% M + 90% C + 10% C = 90% K + 10 % C 2. The necessity of background color removal, ①Improved printing suitability: generally used in dark tone, if the three primary colors Y, M, C are used for printing in the dark tone area, the dot area is often very high. When high-speed multi-color printing, process problems are easy to occur. If the background color is removed, the amount of inking is greatly reduced and the printability is improved. ②It is beneficial to control the neutral gray balance when printing. ③ It is conducive to the drying of the ink and reduces the amount of overprinting of the three primary color inks of Y, M and C. ④Because of reducing the amount of Y, M, C color inks, increasing the amount of black ink, thereby reducing costs, the price of black ink is relatively cheap. ⑤After using high-speed multi-color printing machine, the biggest problem affecting the speed and quality of high-speed printing machine is the problem of ink drying. That is to say, the speed of ink drying will directly affect the speed of high-speed multi-color printing machine and the improvement of product quality. There are many ways to solve the problem, such as changing the composition and structure of the ink, improving the drying method of the printing press, and improving the process, increasing the concentration and gloss of the black ink, and reducing the Y, M, and C primary colors of ink The amount of ink in the part, thus effectively thinning the ink layer to speed up the drying speed, which is the fundamental reason for using UCR in color reproduction. 3. Points to note when removing background color ①Underground color removal generally works in the neutral gray and dark neutral gray areas. ② Correctly control the removal amount. ③ Master the control of the removal point, that is, the scope of the removal control. Third, the relationship between the dark line of the black version and the amount of background color removal The depth of the black version is closely related to the amount of background color removal. The amount of background color removal is large, and the black version should be dark; otherwise, the amount of background color removal is small, and the black version should be shallow. At the same time, the length of the black tone should be based on the length of the dark tone density range of the original. Dark tone density range is long, black version should be long, dark tone density range is short, black version should be short. Neutral gray balance is an important condition for the original copy to be reproduced in color. It is also a technology that is difficult to master in plate making and printing, because the three-color inks of Y, M, and C have certain difficulties in reproducing neutral gray balance. [next] 4. The main factors affecting the neutral gray balance: ①Ink color characteristics. ②The proportion of the three primary colors. ③The color sequence of printing. ④ Paper performance. ⑤ Process operation, etc. 1. First, we must figure out the law of color changes. ①The three primary colors ink can be mixed into black according to a certain proportion. ② After mixing the three primary colors, the ink will be almost black, and with different proportion of diluent, then different colors of neutral gray will be obtained. ③ The three primary colors can be mixed in different proportions to obtain intermediate or multiple colors of different hue, and the hue is biased to the hue with a large proportion. ④ Two primary colors of ink are mixed in equal amounts to obtain standard intermediate colors. 2. Neutral gray balance requirements for ink, ①High transparency: When the ink is coated into a uniform film, the degree of the background color of the material that bears the ink film is developed. The more clearly the background color is displayed, the higher the transparency of the ink. ② Fine pigment particles: fine pigment particles are required for printing high-end and exquisite products. ③ Strong coloring power: The coloring power of the ink is a quantity indicating the color intensity or concentration of the ink. For inks of the same hue, the coloring power depends on the dispersion of the pigment on the binder. The higher the dispersion, the stronger the coloring power; It also depends on the content of the pigment, the higher the content, the stronger the coloring power. ④Light resistance: Under the effect of light, the color of the pigment will change and fade to different degrees, which is light resistance. ⑤High color efficiency: Color efficiency is a comprehensive indicator of ink color difference and gray scale. ⑥Good chemical stability: The color of the ink will change under the action of some chemical substances. Therefore, the ink needs to have good chemical stability, water resistance, acid and alkali resistance, ethanol resistance and other properties. 3. The relationship between the performance of the paper and the neutral gray balance, the product quality of the printing company is greatly affected by the raw material paper, the ideal paper whiteness is 100% reflectivity, and the total reflection of light from 380 to 700 nm. In the process of plate making and printing, it is necessary to consider "different from paper", and adopt appropriate process content to adapt to the paper used, especially in terms of dot thickness, color registration, and contrast of the layout. The papers for high-end and exquisite offset printing products include domestic coated paper, offset paper, painted newspaper and imported coated paper, egg-textured paper, cloth-textured paper, etc. Due to the difference in paper tightness, whiteness, paper absorbency, smoothness, stretchability, etc. , And the curve that reproduces the reproduction tone is also different. The tone level of printing with coated paper is very rich, while the tone level of printing with offset paper is relatively dull. The same is for 157g / m2 coated paper. Due to different origins, there is a certain gap between domestic paper and imported paper. The high-quality paper with low absorption, high whiteness and high smoothness of the paper has an ideal reproduction curve, the amount of ink is thin, and the color is still bright. 4. The relationship between printing color sequence and neutral gray. Monochromatic offset presses use the sequential color sequence of Y, M, C, and K. First, it is considered that the ink with the lowest transparency is printed in the first color, and then the ink with high transparency is printed. The color sequence is arranged according to the transparency of the ink. At the same time, the viscosity of the ink is also considered. Because the viscosity of the Y ink is small, the backside of the printed matter can be avoided; the light color is placed on the front and the ink roller is easy to clean; it is also convenient for four-color overprint accuracy. Multi-color offset presses use the inverted color sequence K, C, M, Y. Because the multi-color presses are wet stacked wet, the printing ink is overprinted again without the oxidation conjunctiva drying. The viscosity of the four-color ink is K> C> M> Y, which meets the requirements of the four-color machine. The color sequence of the multi-color machine is gradually reduced from high to low according to the viscosity of the ink. The high viscosity is placed in front. Imprint, overprint fastness is better. In addition, the color sequence arrangement of the multi-color machine takes into consideration that the lowest transparency is printed first, and the black ink has the lowest transparency, that is, the darkest. As the outline of the screen, the color is denser, so it should be printed in front, so that the transparency is high. The C color is printed on the back, which can make the whole picture bright and eye-catching. Different color sequence arrangements have a greater impact on the neutral gray balance. Different color sequences will directly affect the quality of the printed products and the hue of the colors. In the actual production, a comprehensive analysis should be carried out. Considering the variable factors a little more, the color sequence should be arranged according to the effects of different types of originals and customer requirements in order to achieve the perfect reproduction of the printed matter. In general, the color cast of several inks should also be considered after overprinting: M, C, and Y are easy to turn green after overprinting, C, M, and Y are reddish after printing, and C, Y, and M are easy to reddish, M, Y, C is brownish green after overprinting, Y, C, M is light purple after overprinting, Y, M, C is bluish green after overprinting. Simple design :Kid Furniture Sets Homebase comes with 1 chair, made from faux wood, and the modern two-color design of the table in modern shades of gray and white ensures it looks just as cool in a playroom or living room.
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The significance and influencing factors of neutral gray balance in color printing
The reproduction of printed matter is color restoration, tone restoration, texture restoration and sharpness restoration. The so-called tone is the color classification according to lightness, the color is three-variable, and the neutral gray is a three-dimensional color space; the neutral gray is composed of three colors of Y, M, and C. ) Hv / c means that neutral gray has no hue and saturation, but only the brightness of one-dimensional variables.