Newspaper printing requirements for editorial design and prepress technology
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Improve the printing quality of the color newspaper, and better play its role of propaganda, education, entertainment, etc. The main problem to be solved is to improve the image clarity, tone level range, color saturation and ink uniformity. Based on the newspaper editorial design and prepress platemaking theory, this paper combines the practice of color newspaper publishing and printing to talk about the prepress process control of color newspaper production.
1 editorial design
The color printing has certain limitations in terms of overprinting accuracy, color vividness, level tone and uniformity of ink color. Editors and designers should make corresponding designs on the basis of understanding these technical characteristics, try to avoid their technical limitations and maximize Land to play its advantages.
1) Editing should use images with strong contrast, high definition and rich layers when selecting pictures to create a good condition for color separation plate making.
2) Special attention should be paid when editing electronic photocopies. The resolution of pictures on the Internet tends to be lower, and the color resolution of the picture-receiving network requires pictures from 200 dpi to 300 dpi. Therefore, pictures downloaded from the Internet must have higher precision; other electronic manuscripts should also pay attention to accuracy requirements.
3) Due to the characteristics of newsprint, it is easy to lose the dot in the highlight area, and the dot in the dark area is easy to expand and level, and the vividness of color is also low. In the design color, the color of the high-purity color or the high- and medium-tuning area should be selected as the main color, and it should be expected that the set color has the problem of the bottom gray and color shift of the newsprint during printing.
4) Due to the limited overprinting accuracy of the rotary machine, when designing colored text or doing reverse white characters, the use of Song and small characters should be avoided, and the color of the small characters should not exceed two colors.
5) The uniformity of the ink layer printed on the newsprint by the rotary machine is limited by the conditions. The large-area flat net should be minimized in design, especially the multi-color overprinted flat net is extremely difficult to print evenly.
6) The reel receiving paper is positioned by the pressure of the pressing wheel, and it is easy to press the dirt in the middle seam. In the newspaper arrangement, the thick text and images should be avoided in the newspaper.
2 prepress production
Newsprint printing and printing equipment used in color printing have determined that color printing is different from general color printing. To stabilize and improve the printing quality of color newspapers, prepress production process control is very important.
1) Image processing
1 scan settings
In order to adapt to the process characteristics of the color printing, the setting of the scanning should focus on improving the clarity and layering effect of the picture. The following aspects should be noted.
Set the resolution of the scan reasonably. Generally, the input resolution is between 200dpi and 300dpi, which should not be too high.
In order to reduce the loss of the level, the tone range should be set to the maximum range during scanning, and the black and white field and tone curve are preset according to the type of the picture.
In order to improve the definition, the picture should be sharpened, that is, the sharpening value should be appropriately adjusted according to the picture.
De-net processing of printed originals.
Black and white field settings. The black and white fields are the starting point and the ending point of the image tone. Correctly setting the black and white fields is the key to grasping the tone. Since the whiteness and ink density of newsprint are much lower than that of general color prints, the tone of the print is compressed to a smaller extent. In order to improve the printing effect of the image, it is necessary to appropriately set the black and white fields according to the characteristics of the main body of the image, and intentionally compress the tone which does not affect the image area of the main body, so as to play a large contrast.
For general color prints, in order to achieve color reproduction, the level of the high-definition area is preserved, and the white field is usually set in a small-scale highlight. In newsprint printing, the small dots in the highlights are easy to lose, the paper itself has more than 5% of the grayscale, and the over-emphasis on the level of the highlights will affect the overall tone range, making the picture gray. Therefore, the white field area should be appropriately expanded. Sometimes it is necessary to lay off some bright layers in order to highlight the main body. At the same time, it should be noted that the white field area should not be too large to prevent large-scale nets.
Whether the picture level is rich or not is reflected in the dark tone. For general color prints, the darkest smaller area is mostly selected as the black field in image processing. However, according to the high expansion rate of the dot in the newsprint printing, the outlets are prone to the characteristics of the level. In order to take care of the overall effect of the image, it is necessary to discard some of the hidden layers when necessary.
2 level correction
The correction of the gradation curve is to compensate for the gradation that is compressed due to the setting of the black and white field, to expand the gradation of the dark part, to avoid the gradation of the dark part, to play the role of widening the contrast and adjusting the ratio of high, medium and low to ensure the subject level. Correctly restore and increase the stereoscopic effect of the image. The correction of the image level should be analyzed and processed according to its tone type, requiring the operator not only to have experience, but also to have the ability to understand and art the image.