Talking about How to Improve the Printing Quality of Newspaper Pictures
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In all aspects of newspaper publishing and printing, the quality of the picture largely determines the printing quality of the newspaper. Therefore, in order to improve the quality of the newspaper, we must first improve the quality of the picture. This article will combine the actual situation of Guangzhou Daily and my experience in the Guangzhou Daily for a few years to talk about how to improve the quality of newspaper printing.
The image source of this newspaper is divided into foreign pictures and scanned pictures. Among them, foreign pictures include Reuters and Xinhua News Agency pictures, reporters' remote pictures and edited pictures downloaded from the Internet or copied to floppy disks by other means. In the foreign pictures, Reuters and Xinhua News Agency pictures are of good quality. Some of the pictures in the reporter's remote pictures are of poor quality, and some of the color casts are serious. They cannot be compensated by Photoshop adjustment, and the pictures downloaded on the Internet are too small. When zooming in the typesetting software, a grid appears to affect the effect of the report. Therefore, we should try to avoid using pictures on the Internet, and secondly, we should improve the quality of the reporter's remote pictures. In the pictures used in this newspaper, the proportion of foreign pictures is close to 80%. The improvement of the quality of this part of the picture plays an important role in improving the overall quality of the newspaper.
In addition to the pictures, the other 20% is the picture scanned by the scanner. Since the quality of the scanning depends largely on the quality of the original, the quality of the original is first guaranteed, and the second is determined by the technique of scanning.
At present, most of the image scanning work of this newspaper is in the Linotype-Hell multi-top desktop scanner and Mi-crotek. Scanmaker2000 is done on the scanner. Here are some tips for scanning when using the multi-master scanner as an example.
The scanning software used by the multi-master scanner is the Lino-color scanning software, which can select a certain scanning method according to the content of the image before scanning, which is more important for the scanning quality of the image, and it can more perfectly represent the content of the image. And if you reprocess it in software like Photoshop, you will lose information. The following is the Colorassis in the scanner driver in Lino-color.
Features of each option under tant:
Standard: Corrects color shift, contrast, and chromaticity over the dynamic range.
Landscape: Increases contrast and color density for natural scenery, holidays, entertainment, and advertising.
Portrait: Reduces contrast and color density and applies to originals whose skin is dominant.
Jewellery (jewelry): Increases the color density, reduces the treatment of color shift, and applies to the high-brightness of gold and silver.
Sunset: Increases color density and reduces the processing of color cast.
Technical: Contrast enhancement in the dark portion, applied to HiFi devices, TVs, cameras, etc.
When the picture quality is high, the "sharpen" option can be used to make the picture clearer based on the above items.
After the image is scanned into an electronic file, the image needs to be processed. Whether it is a foreign image or a scanned image, it needs to be color-separated, adjust the color shift, improve the resolution, etc., so that it meets the standards required by printing. . When processing images, first set the correct prepress parameters.
First, correctly set the prepress parameters
The purpose of pre-press parameter setting is to establish the characteristic parameter file of printing ink, paper, etc., so that the picture displayed on the computer screen is close to the effect of seeing the picture after printing, and the "what you see is what you get" when processing the picture; The second is to set the color separation parameters suitable for the printing press printing of this newspaper; the main software for processing pictures is Photoshop. In Photoshop, the pre-press parameters include separation settings (Separation Setup) and Printinginks Setup.
1. Separation setting, this parameter not only controls the amount of ink on the printing press, but also controls the degree of blackness produced. This parameter can be obtained by the printing test on the machine.
1.1 total ink volume control, due to the limitations of newsprint printing, this parameter can not be too large, otherwise there will be serious ink accumulation phenomenon. After printing test, this newspaper sets the parameter to 240%, that is, the sum of the four inks combined. No more than 240%.
1.2 GCR (ash component substitution) and UCR (background color removal), GCR is to remove the color of the gray area synthesized by the three inks of cyan, magenta and yellow, and replace the neutral gray with this part with black ink; UCR is to remove dark The gray portion of the three primary color inks is adjusted and replaced with black ink. Both of these methods are designed to reduce the total amount of ink during printing to reduce the phenomenon of ink accumulation. Since UCR is sometimes difficult to control on a press, GCR is generally used. After the printing test, the newspaper set the parameter to Medium, that is, the part whose tone is less than 20% is not replaced by black.
1.3 black ink volume control, this parameter controls the maximum amount of black ink after color separation. After printing test, we control the black ink volume to 85%.
2. Printing ink settings
2.1 Ink color, this parameter records the characteristics of the ink used for printing. The setting suitable for newspaper printing is SWOP (Newspaper), which is the web offset specification (newspaper).
2.2 dot enlargement, this parameter records the dot enlargement in printing. The setting of this value will affect the image display in Photoshop, making it look similar to the printed effect. In addition, the dot gain of the four inks used in printing may be inconsistent, and therefore, the dot gain values of the cyan, magenta, yellow, and black inks may be separately set. These values can be set by the following test methods: Great China Graphic Arts Network
Make a signal strip in Photoshop, including nine solid colors such as cyan, magenta, yellow, black, red, green, blue, white, neutral gray superimposed with three primary colors, and 50% cyan, magenta, yellow , black block. The signal strip was printed together with the newspaper, and the Y, x, y values of the nine solid colors and the dot gain of the 50% color patch were measured by a color reflection densitometer. In ink Select Custom in the colors option, and input the measured Y, x, and y values of the nine solid colors into the corresponding ink dialog box, so that the color characteristics of the ink used for printing are accurately recorded. The dot gain values of cyan, magenta, yellow, and black can be accurately set based on the dot gain values of the other four 50% color patches. On the basis of the test, the above parameters can also be adjusted in combination with the image printing effect of the newspaper.
Second, some tips for image processing
In addition to setting the correct prepress parameters, the technique for processing images is also essential and more flexible. Here are some image processing tips that will be shared with everyone.
1. After the image is scanned, try to correct the color in RGB mode, and then make fine adjustments in CMYK mode. Because the gamut range of the RGM mode is wider than the gamut of the CMYK mode, there is no loss of too much detail and detail when making large corrections in the RGB mode.
2. Because some sharp edges of the original are smoothed during the scanning process, in order to make the printed image have clear color and detail, after the color correction of the image, USM is used to sharpen, so that the image has A richer level.
3. If you want to enlarge the image, you should try to enlarge it in Photo-shop, and avoid zooming in on the image in the layout software. Enlarging an image in typesetting software only enlarges the pixels and degrades the image quality.
4. When correcting the image with gray balance, the reference should be based on cyan. The value of cyan is greater than the other two colors. The values of the other two colors are roughly equivalent, and the value of the obtained gray balance is equal to cyan.
5. Since the Curves tool is more powerful than the Levels tool in controlling color, you should use the Curves tool for color correction.
6. When processing the picture, the value displayed on the Info panel is used. Refer to the image displayed on the screen to determine whether C, M, Y, and K in each area are color cast. Whether the highlight and shadow areas are within the printing range, too bright. The highlights and too dark shadows are not suitable for printing on the press.
7. Some processing of the image can be performed in a single channel. For example, after the original of the printed matter is scanned, the quality of the Y or C channel is generally poor. In particular, the Y channel is often obvious, and can be processed separately; for the original is an unregistered print, it can be slightly Move its unregistered color channel and it works well. In addition, the individual modification of the K channel is more important for the quality of the picture. For the manuscript with poor quality, it is often necessary to open the K channel for observation and modification.
8. According to the content of common news pictures, some processing methods and approximate data:
People: If the face of the character is large in the picture, you can use “skintone” when scanning, and pay attention to ensure that the level of the middle tone is rich. The approximate standard of skin tone in facial treatment (only in line with this newspaper): Generally speaking, the values of C and K are zero; the bright parts Y and M are kept below 10%, and the dark parts are kept below 40%, generally yellow people The Y can be more, the face is yellow, the Caucasian M can be more, and the face is pink.
Landscape: The middle adjustment can be appropriately extended to open the layer, and the distance of the picture is increased. The curve curve is slightly S-shaped and the color saturation is relatively high.
Utensils: Try to ensure the level of detail, for a metal appliance can be sharpened to reflect its texture.
Night Scenery: Try to take care of the large areas of the middle and dark levels, rather than dead, especially pay attention to the phenomenon of ink accumulation due to excessive ink. At night, especially when the photo is reddish, the reddish tone must be reduced, otherwise the picture will be grayed out.