The printing layout is generally designed and produced by a computer, but the final carrier of the work is paper. From the design pattern on the computer screen to the final printed product, it needs to go through multiple processes such as color separation, plate making, and printing. Due to the limitations of printed materials and processes, many designs that work well on the screen cannot be reproduced correctly after printing. Facts have shown that only by perfectly combining the art of layout design with modern printing technology can the best printing reproduction be achieved. This paper discusses several issues that must be paid attention to in the design of layout colors from the perspective of printing technology.
1 Reasonable selection of spot colors and primary colors
1) There are many colors that cannot be represented by overprinting with primary colors, which can be reproduced with spot colors. When spot colors are used, the color printed on the paper is completely determined by the color of the spot color ink. The spot color set on the screen only serves as a reference, and is not completely consistent with the final color printed on the paper. However, spot colors have their limitations. Many of the highly saturated colors seen on the screen cannot be adjusted.
2) Since each spot color is a version, the color depends only on the ink. Compared with the use of multiple primary colors to obtain a new color, it can maintain the consistency of the color. The color patch printed by using the primary colors will change the color of the color patch due to the change of the solid density or dot area of ​​any primary color forming the color patch, which greatly increases the chance of color cast and ink unevenness.
3) When printing large areas of light color blocks, if the four-color printing process is used, due to the low coverage of the ink on the paper, the ink color is flat and lacks a thick feeling. Moreover, due to the problem of the angle of amplitude modulation and screening, it is inevitable that people feel the existence of moiré; and the spot color printing method is used to print light colors, and the diluent is added to the original ink and then printed on the ground, the ink layer is thicker, compare It is easy to get a uniform and thick effect. Therefore, most of the light colors will be better reproduced with spot colors.
2 Selection of printing chromatography
The choice of layout color for four-color printing should be determined based on the printed color spectrum, not the color on the computer screen. The color gamut range of four-color printing is smaller than that of the screen. Many highly saturated colors on the screen cannot be reproduced by four-color printing. Strictly speaking, only when the ink, paper and printing process conditions are the same, the color of the chromatogram will match the printing color selected according to the chromatogram. Some printing factories print their special chromatography according to the actual production conditions of the factory. The layout of the factory should use our chromatography. If the factory does not have a self-made chromatography, the actual printing conditions of the factory should be fully considered when selecting the chromatography, and the chromatography should be as close as possible to the paper, ink and printing conditions, rather than the one-sided selection of exquisitely printed chromatography.
At present, most of the chromatograms used by various printing factories are printed on imported coated paper. If the designed works are finally printed on coated paper, and the printing process is similar, the color reduction is generally better. However, if printed on offset paper or newsprint, due to the poor smoothness and good ink absorption of these non-coated papers, the ink layer required for printing is thicker, and the dot expansion is relatively large. Set the color dots with reference to the color spectrum of coated paper When the area is large, you need to reduce the screen number. For example, if the screen size is 30%, it may be set to 26% on offset paper and 24% on newsprint, depending on the printing. Depending on the process conditions of the printing house.
3 Text color setting
In graphic design, text not only plays a role of explanation, but its shape and color itself have a strong visual expression ability, which plays an important role in the success of the overall design. The text design needs to consider the following questions.
1) The greater the contrast between the text and the background color, the clearer and more conspicuous, the more conducive to reading. Do not print inverse text in light-colored areas, and do not print inconsistent colored text in colored background areas.
2) The text is best located in the blank space of the layout, or in the area with a relatively uniform background color. In the area where the hue is obviously uneven, whether it is printing reverse text or colored text, because the contrast between the text and the background color is chaotic , Easy to cause reading difficulties.
3) In spot color printing, the ink layer is generally printed thicker, and the ink will expand under pressure; when multi-color overprinting, there will always be overprint errors. Therefore, the text and lines that need to be highlighted, whether it is spot color printing or primary color overprinting, must not be too thin, generally not less than 8 pounds, and be careful not to use too thin fonts such as Song and thin circles, try to use bold, Lishu Fonts with obvious lines.
4) The color setting of the text should use spot colors or a single primary color as much as possible. Text that is overprinted from several colors may look good on the screen, but because it is overprinted during printing, it is easy to overprint. Accurately affects reading; when light-colored dots are used, the edges of text or lines will appear jagged, affecting aesthetics.
4 Color settings for color blocks and large-area background colors
1) Try to avoid the use of too many small dots, such as flat mesh dots below 15%, which is easy to cause localization due to insufficient air suction or fine particles adhering to the film and glass of the plate-making machine during printing Light exposure; when printing, it is easy to cause the plate to be dropped due to excessive moisture, dirty rubber blanket or plate wear, etc. Both of these reasons may cause uneven ink color. As for the outlets below 5%, it should be avoided for ordinary lithography process.
2) To avoid the use of too many dots, such as more than 95% of dots, it is easy to paste in printing due to insufficient water supply or dirty rubber blankets.
3) Try not to choose colors that need to be overprinted from three or four primary colors. The more overprinted colors, the more difficult it is to overprint, and due to various variables in the printing process, the reproduced colors may be the same as the specified colors. The difference is very far; in addition, the color produced by the three-color or four-color solid or high-density dots overprint is easy to be dried because the thickness of the ink layer is too thick at the time of printing, causing the back to be dirty.
4) When printing large-area background colors, use blue-violet and nearby sensitive colors on the color ring as little as possible; try to avoid large-area flat screen printing, because large-area flat screen printing is prone to ink bars and front depth due to machine reasons. After light, etc., if possible, it is best to use a solid color to print a large area of ​​background color.
5) When there is both a color mesh tone image and a large area of ​​black background on the layout, it is recommended to use black solid parts and about 30% ~ 40% of green to overprint the black part, so that the black background is printed better than Only print solid black to be thick and even. This is because usually in four-color printing, the solid density of black cannot exceed 1.9. When printing a large-area background color with such a density, a thick visual effect is lacking. Adding a green plate can make up for the lack of black printing. However, it is not necessarily printed with cyan, and the adjustment value of cyan is not necessarily about 40%, and adjustments should be made according to actual needs. If there is a warm color pattern on the black background and the edges are feathered, then the screening of the background color should be adjusted according to the main warm color, such as overprinting with 100% black, 20% magenta, and 30% yellow, such a pattern transition The part will look more natural than overprinted by black and cyan. If there is reverse text or lines on the black part of the overprint, it is necessary to fill in the trap, that is, make the reverse part of the blue version larger, otherwise the reverse part may be exposed to cyan because the printing is not 100% registered.
6) When using spot colors, try not to use color blocks that need to be prepared from too many basic colors of ink. The mixing of too many inks makes the difficulty of ink preparation greatly increased, that is, the ink adjustment time is also increased. It is difficult to mix colors that are close to the same; when printing large-area background colors in spot colors, you should also pay attention to using blue and purple on the color circle and nearby sensitive colors as little as possible.
In short, although the color spectrum and color guide both provide richer colors for designers to choose from, due to the limitations of printed materials and processes, there are many colors that are relatively difficult to achieve when printing, and it cannot be taken for granted that the design effect on the screen will be Faithfully reproduced on paper. Try to avoid the limitations of printing materials and processes on the reproduction of graphic colors, and selectively use some easy-to-print colors, which is convenient for production and more importantly, the product quality is more guaranteed, so that it is possible to achieve from design quality to printing Boutique.
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