How to improve the printing quality of newspaper p

How to improve the printing quality of newspaper pictures

in all links of newspaper publishing and printing, the quality of pictures largely determines the printing quality of newspapers. Therefore, to improve the quality of newspapers, we must first start with improving the quality of pictures. Combined with the actual situation in Guangzhou and my experience of working in Guangzhou for several years, this paper talks about how to improve the picture printing quality of newspapers

the pictures of this newspaper are divided into foreign pictures and scanned pictures, among which foreign pictures include Reuters and Xinhua pictures, remote pictures and pictures downloaded from the Internet or copied to floppy disks through other means. Among the foreign pictures, the pictures of Reuters and Xinhua news agency are of good quality. Some of the remote pictures are of poor quality, and some of them have serious color deviation, which cannot be compensated by Photoshop adjustment. However, the pictures downloaded from the Internet are too small in size, which will show grids when enlarged in the typesetting software, thus affecting the newspaper effect. Therefore, we should try to avoid using pictures on the Internet. Secondly, we should improve the quality of remote pictures. Among the pictures used in this newspaper, foreign pictures account for nearly 80%. The improvement of the quality of this part of pictures plays a decisive role in the improvement of the overall quality of the newspaper

in addition to foreign pictures, the other 20% are pictures scanned by the scanner. Since the amount of quality rope pulling machine scanned largely depends on the quality of the original, it is necessary to ensure the quality of the original first, and then depends on the scanning skills

at present, most of the image scanning work of this newspaper is completed on the Duoba desktop scanner of Linotype hell and the MI crotek scanmaker2000 scanner. Here are some skills of scanning with Duoba scanner as an example

the scanning software used by Doba scanner is lino color scanning software. This software can select a certain scanning method according to the content of the picture before scanning, which is more important for the scanning quality of the picture. It can better represent the content of the picture. If it is processed in software such as Photoshop, information will be lost. The following are the characteristics of the options under colorassis tant in the scanner driver in lino color:

standard: correct color deviation, contrast and chromaticity in the dynamic range

landscape thanks China for its care and convenience in transit transportation. PE (landscape): increase contrast and color density, and apply it to natural scenery, holidays and entertainment. Scientists evaluated lignin music and advertisements from wheat straw, cork (such as pine) and hardwood (such as oak)

portrait: reduce contrast and color density, and apply it to originals with skin tone accounting for the main part

jewelry: increase the color density, reduce the treatment of color deviation, and apply it to the highlight of gold and silver

sunset: increase the color density and reduce the treatment of color deviation

technical (Technology): enhance the contrast in the dark part, which is applied to hifi devices, televisions, cameras, etc. when the picture quality is high, using the "sharpen" option on the basis of the above items can make the picture clearer

after the image is scanned into an electronic document, it needs to be processed next. Whether it is an external image or a scanned image, it needs to be processed by color separation, color deviation adjustment, sharpness improvement, etc. to make it meet the standards required by printing. When processing pictures, you should first set the correct prepress parameters

first, set the prepress parameters correctly

one of the purposes of prepress parameter setting is to establish the characteristic parameter files of printing ink, paper, etc., so that the effect of the pictures displayed on the computer screen is similar to that of the pictures published after printing, so as to achieve the "what you see is what you get" when processing pictures; Second, set the color separation parameters suitable for the printing machine of the newspaper; At present, the main software for processing pictures is Photoshop. In Photoshop, prepress parameters include separation setup and printing inks setup

1. color separation setting. This parameter not only controls the ink amount of the printer, but also controls the degree of black produced. This parameter can be obtained through the printing test

① total ink volume control. Due to the limitations of paper printing, this parameter cannot be too large, otherwise serious ink stacking will occur. After printing test, this newspaper sets this parameter to 240%, that is, the sum of the four inks does not exceed 240%

② GCR (gray component substitution) and UCR (background color removal). GCR is to remove the color of the gray area synthesized by cyan, magenta and yellow inks, and use black ink to replace this part of neutral gray; UCR is to remove the dark part of the gray part synthesized by the three primary color ink and replace it with black ink. These two methods are to reduce the total amount of ink during printing to reduce ink stacking. Because UCR is sometimes difficult to control on the printing press, GCR is generally used. After printing test, this newspaper sets this parameter to medium, that is, the part with a gradient lower than 20% will not be replaced by black

③ black ink volume control. This parameter controls the maximum black ink volume after color separation. After printing test, we control the black ink volume at 85%

2. printing ink setting

① ink color. This parameter records the characteristics of the ink used for printing. The setting applicable to newspaper printing is swop{newspaper}, that is, web offset printing specification (paper)

② point enlargement. This parameter records the point enlargement in printing. The setting of this value will affect the image display in Photoshop, making it look close to the printing effect. In addition, the dot enlargement of the four inks used in printing may be inconsistent. Therefore, the dot enlargement values of cyan, magenta, yellow and black inks can also be set respectively. These values can be set by the following test methods:

make a signal bar in Photoshop, including nine field colors such as green, magenta, yellow, black, red, green, blue, white and neutral gray after the superposition of the three primary colors, as well as 50% green, magenta, yellow and black blocks. Print the signal strip together with the newspaper, and measure the Y, x, Y values of nine field colors and the point enlargement value of 50% color blocks with a color reflection densitometer. Select custom in the ink colors option, and input the measured y, x, and Y values of the nine field colors into the dialog box of the corresponding ink, so as to accurately record the color characteristics of the ink used for printing. The dot enlargement values of cyan, magenta, yellow and black can be accurately set according to the dot enlargement values of the other four 50% color blocks. On the basis of the test, the above parameters can also be adjusted in combination with the picture printing effect of the newspaper

II. Some skills in image processing

in addition to setting correct prepress parameters, the skills in image processing are also essential and more flexible. Here are some image processing techniques to share with you

1. After the picture is scanned, the color should be corrected in RGB mode as much as possible, and then slightly adjusted in CMYK mode. Because the gamut range of RGM mode is wider than that of CMYK mode, large correction in RGB mode will not lose too many levels and details

2. because some sharp edges of the original will be smoothed during scanning, in order to make the printed image have clear tones and details, use USM to sharpen the image after color correction, which will make the image have richer layers

3. if you want to enlarge the image, you should try to enlarge it in the P test metal material crack growth rate and material threshold hot shop, and avoid enlarging the image randomly in the typesetting software. Enlarging the image in typesetting software will only enlarge the pixels and reduce the image quality

4. when correcting the image with gray balance, we should take green as the reference. The value of green should be greater than that of the other two colors. The values of the other two colors are roughly the same, and the value of gray balance obtained is equal to that of green

5. because curves tool has stronger ability to control color than levels tool, curves tool should be used more for color correction

6. when processing pictures, the value displayed on the info panel shall prevail. Refer to the image displayed on the screen to judge whether the C, m, y, K in each area are biased, and whether the highlight and dark tone areas are within the printing range. Too bright highlight and too dark tone are not suitable for printing on the printer

7. some image processing can be carried out in a single channel. For example, after the original print is scanned, the quality of Y or C channel is generally poor, especially the point of Y channel is often obvious, which can be processed separately; For the original is an unregistered print, you can slightly move its unregistered color channel, and the effect is good. In addition, the independent modification of the K-channel is more important to the quality of the picture. For originals with poor quality, it is often necessary to open the K-channel for observation and modification

8. according to the content of common pictures, some processing methods and approximate data:

people: if the face of the people in the picture accounts for a large proportion, you can use "skintone" during scanning, and pay attention to ensure that the level of the middle tone is rich during processing. The general standard of skin tone in face processing (only in line with this newspaper): Generally speaking, the values of C and K are zero; The bright part y and m are kept below 10%, and the dark part is kept below 40%. Generally, the yellow people have more y, and the face is yellow, while the white people have more m, and the face is pink

scenery: the middle tone can be appropriately lengthened to open the level and increase the sense of distance of the picture. The curve curve is slightly S-shaped, and the color saturation is relatively high

utensils: try to ensure the level of detail. For example, metal utensils can be sharpened to reflect their texture

night scenery: try to take care of a large area of medium and dark tones with layers inside, rather than dead black, especially pay attention not to pile up ink due to too much ink. At night, pictures, especially photos, tend to be red, and the dark tone must be reduced, otherwise the pictures will be grayed out