In the newspaper In the printing production, the layout of the advertising theme is usually produced by the advertising company. The layout of the news theme is produced by the prepress department of the newspaper. After the printing company obtains the digital files of different layouts, it is printed on the large version and printed on the printing plate. Since the color decomposition of the prepress process and the color synthesis of the printing process are respectively produced by different companies, there is a lack of communication between them, which makes the entire production process of the color newspaper often lack effective color management, resulting in quality disputes such as color cast and smudging. Therefore, how to effectively manage the color of the newspaper printing process is the focus of every newspaper printing factory.
Problems with newspaper printing
1. Problems in prepress plate making
In the pre-press process, due to the lack of in-depth understanding of color management by some prepress producers, when converting picture mode from RGB to CMYK, Photoshop software's default printing paper printing characteristic file is often used (such as Japan, which is often used). Color 2001 Coated.icc, etc.) is the target property file for color separation . Take Japan Color 2001 Coated.icc as an example, the color space represented by it is very different from the color space printed by newspapers. In the case of a picture that is separated in this case, the color cannot be accurately restored during the printing process. The more obvious drawback is that the total amount of ink specified by Japan Color 2001 Coated.icc is as high as 350%, that is, after the black part of the picture is separated, the sum of the dot area ratios of the CMYK four-color ink is close to 350%. This is not only a waste of ink for newspaper printing, but also a printing failure such as smearing when the paper is delivered due to the inability of the ink to dry in time.
In addition to using the printing property document of the coated paper as the target property file for color separation, some prepress producers also use the printing property document of newsprint (such as ISOnewspaper26v4.icc) as the target property file for color separation. Taking ISOnewspaper26v4.icc as an example, the specified black ink starting point value is 0%, the maximum value is 95%, and the color separation option selects the maximum gray component substitution (GCR). In this case, the color separation picture, after printing, the black ink replacement amount is too much, which tends to cause the density and gloss of the intermediate adjustment and brightness adjustment parts to be lowered, the level loss is serious, and the color saturation is poor. Meanwhile, since the amount of black ink Alternatively, the body color becomes black, and when printing of national newspapers prepress color separation files, often with square dots, and the CMYK four-color dot printing corresponding to the angle set to 15 ° 45°, 90°, and 75°, in which the black plate is not arranged in the 45° direction as the main color plate, resulting in a colored portion overprinted by four-color ink, especially in the middle and the bright and bright parts. The grain, which causes the picture to be rough and the layer to be lost.
Therefore, we believe that the default print profile of Photoshop software and the print profile of newsprint are not suitable for use in domestic newspapers for color separation. It is necessary for domestic newspaper printing factories to generate printing characteristic files according to their own process characteristics after printing and calibration, for use in pre-press separation, proofing and setting color block colors.
2. Problems in the printing process
In the actual production process of newspaper printing, because most newspaper printers either have no density meter, or because there are no test strips in the newspaper, or because the printer does not develop the habit of controlling the amount of ink by detecting density, the printing process The control of the amount of ink is mainly based on the long-term experience accumulated by the printing workers. In addition, because photo editors and prepress producers are accustomed to using the color seen by the monitor as a measure of the printing effect, it is always felt that the color after printing is not bright enough. Therefore, in order to meet the requirements of photo editors and prepress producers, some newspaper printers intend to increase the amount of ink in the printing process of newspapers, so that the actual density values ​​of the four basic colors of CMYK clearly exceed the international standard ISO 12647-3 for newspaper printing. And the standard density values ​​of the four basic colors of CMYK recommended by the national standard GB/T 17934.3.
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