Color Adjustments in Images and Groups in Color Newspapers (I)

At present, many counties and cities in China still only publish four editions and have a circulation of about 20,000 copies. Due to the needs of the market, they sometimes have to go to some big newspapers and print newspapers. The same printing machine, using the same software for processing, can print at a good time with a good time difference, and has a big difference between the print quality of hundreds of thousands of prints. The reason is that the important point is that the speed of the high-speed webbing belt can reach 9~13m/s, and the number of prints available for small color paper is only about 10,000 copies. In the case that the color has not been transferred to the best, it has reached the limit of printing scrap. Numbers, printers often make do, which is difficult to guarantee the quality of printing. How to solve this problem, on the one hand, the technical workers of the printing plant should improve their own quality, and the color correction should be accurate and fast. On the other hand, the typesetting personnel must also have certain cooperation in the pre-press processing of the small color newspaper, so that when printing It is relatively easy to adjust the color tone, and to speed up the coloring speed when printing in small color papers. Therefore, small color newspapers will have a relatively good print quality. Prepress processing includes the process of image processing, group edition, output, and plate making. The following two aspects of image processing and group edition adjustment will improve the printing quality of small color newspapers.

The picture plays a very important role in the color newspaper. Beautiful pictures often play the role of finishing touch and give people an artistic enjoyment. In order to get the best printing effect, the first thing is to adjust the picture. In the printing of small newspapers, the prepress processing of the pictures is particularly important. Only a good picture can make it easier and faster to adjust the colors during printing.

1. Original quality

It can be said that if the original quality of the picture is not high, although the prepress processing and printing process adjustment are fully in place, the quality of the picture cannot be greatly improved. For this reason, the selection of manuscripts is crucial. The requirements for color pictures printed by color newspapers are: colorful, rich, accurate, realistic, basically without large color deviations; distinct layers, good clarity, and good luck; moderate contrast, uniform distribution of levels; no scratches on photographs, Handprints, dust, creases, etc.

For the original is a photo, try to use non-meter photo paper (do not have a variety of lines); if it is the second time the printed manuscript is best to print more than 150 lines / inch (exquisite sample, etc.), and do not enlarge The original draft for the line drawing manuscript is better than the copy. In addition, the picture files downloaded on the Internet are generally relatively small, and the accuracy and definition are not enough, and they should be used as little or as little as possible.

It should be pointed out that in order to achieve the above requirements, in addition to the hard work of the image processing staff, it is necessary to get the cooperation of newspaper editors and reporters to jointly improve the quality of the original image.

2. Image processing

(1) Process color pictures in RGB mode. The RGB mode is the color mode adopted by all devices based on the principle of optics. It can express many colors, especially bright and bright colors. The editing process of a picture often goes through many subtle processes. For example, it may be necessary to combine the contents of several pictures. Since the original colors of the various components cannot be the same, they need to be adjusted. Regardless of the effect of the picture processing, the operator wants to create and retain as many subtle effects as possible, and to make the picture as real and rich as possible. Since the color range of the RGB mode is much larger than the CMYK mode, when the picture is processed in the RGB mode, a wider color space and more nuanced editing effects will be obtained during the entire editing process. If you use it well, most of you can keep it. Although in the end it still had to be converted to CMYK mode and there was definitely a loss of color, it was much better than letting pictures lose color from the beginning.

(2) Image sharpness adjustment. Sharpening is the most effective way to improve image sharpness in small color picture adjustments. Compared with the high-end printing, because of the limited printing conditions, the dot-printing rate is high, the coarse mesh, and the large sharpening value are conducive to improving the image sharpness. Generally, the screen effect can be slightly out of date. From the point of view of the hanging net technology, sharpening also eliminates the effect of the level loss that occurs due to the hanging net. From this point of view, sharpening is by no means a link that can be done, but is an essential part of prepress processing.

The degree of sharpening is related to the type of the original image and the zoom ratio. Usually, the sharpness of the character artwork is smaller, while it may be larger for the landscape document. In general, the greater the sharpness of the picture, the higher the magnification and the deeper the sharpening.

(3) Adjustment of picture level. The purpose of level adjustment must first meet the printing requirements. According to the characteristics of newspapers with high expansion rates of printing outlets, the compensation for the expansion of outlets in the printing process is to be concentrated in the middle region, ie, 20% to 60% of visually sensitive areas. In the adjustment process, that is to say, the gradation of the manuscript corresponds to the gradation that the printing can reproduce to the maximum, so that the image is clear and real, and secondly, the accuracy of the adjustment of important parts is ensured according to the content of the manuscript and the level distribution. Such as clothes, face, etc., must be clear, such as the level of the face should not be less than 15%; again, to adjust the value of extreme light or shade, can not be a large area of ​​net, generally controlled at 2% to 95% about.

(4) Image color adjustment. The adjustment of picture color is what people usually call school coloring. It is mainly to reproduce the color reflected by the original (not the original itself). In the course of operation, it is mainly to correct the color shift caused by the original or scanning, and to ensure the color of the main body is accurate. The color adjustment should ensure that the screen effect is compatible with the final printing effect. Keep in mind that newsprint has a grayscale of 3% to 5%. It is best to use the proofs or more accurate printing products to open the original digital file and contrast the color. . At the same time, it should be noted that the school color adjustment should be based on the information displayed on the information board, but not on the screen alone.

(5) Convert RGB mode to CMYK mode. The picture used to print the film must be in the CMYK mode, so the picture mode must be converted before the film is released. It should be noted that some picture color changes occur when the picture mode is converted. The picture in CMYK mode is always brighter than the picture in RGB mode. After the conversion, you should first observe the picture and confirm that there is no color cast before output. If you think that you are not satisfied, you should immediately cancel the conversion of the color mode, and never convert it back to RGB color mode again, resulting in irreversible color loss.