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Standardization and digitalization of color newspaper printing operation process

standardization and digitalization control production process refers to "standardization of operation procedures and steps, digitalization of whole process quality control and related factor control." Through digitization and standardization, we can stabilize the variable factors in the process of phototypesetting, plate making, proofing and printing, effectively control the information conversion and transmission in the process of color newspaper production, and carry out color processing as perfectly as possible to achieve true color reproduction

because the actual conditions such as the materials and equipment used will constantly change, which can be solved by the bridge compensation method, there are many differences in the specific operation. Therefore, this paper only plays an overall role in the formulation of the digitization and standardization of the color newspaper printing process, which is only for reference

1 standardization and digitization of phototypesetting process

the standardized operation of phototypesetting involves the whole process from text input to film development and inspection. Under the condition that the hardware and software systems work normally, reasonable Phototypesetting process data should be formulated according to the printing raw materials (paper, ink, plate, etc.) and printing suitability (ink volume, pressure, ink balance, etc.)

1) standardization of phototypesetting process

① black and white field tone range

this is an important indicator of image quality due to the general sampling frequency of 2000Hz in Figure 1. The longer the tone range, the greater the image contrast, the better the visual effect and the stronger the stereoscopic sense. However, the gradient range is restricted by the conditions of the subsequent process. If the white field point on the color separation sheet is too small, the picture and text points may not be exposed to the printing plate or printed on the paper; If the dot is too large, a paste may be formed during printing, and the dark tone level is obviously lost. Therefore, different printing conditions should have different gradient ranges. The white field should give up the bright tone in a small area (such as eye whites, shirt buttons, etc.). The printing characteristics of newspapers determine that their tone range is narrow, generally 3% - 90%. In case of large-area white field, the minimum point can be set as 4% (to prevent large-area extinction), and the black field is selected as 80% - 85%. Black field can be a small number of level, but to prevent a large area of absolute and paste version

② gray balance curve

in the process of determining the gradient range, it is necessary to determine the point percentage of each color separation plate that can ensure the reduction of neutral gray in the original. In view of the dynamic display of Swiss rotary offset four-color ink with the experimental process of Taiyuan gaoshilao data and curves, the percentage of dots in different tone ranges of each color separation plate of neutral gray is: at the highlight, the C version should be 2% - 3% higher than the M version and Y version; Intermediate mediation version C is 8% - 9% higher than version m and version y; At the dark tone, version C is 10 ~ 12% higher than version m and version y

③ fixed level curve and black version curve of different original types

because the original has transmission and reflection, and different originals have different density ranges, some abnormal originals may be too thin or too thick, so five fixed level curves can be set for transmission and reflection originals respectively: through originals with different density ranges and different thicknesses, Taking the intermediate adjustment as the standard value as a fixed layer, PGA has also been developed as an internal fixation system (biofix reg;) For the secondary curve, the other four curves are adjusted by ± 5% or ± 10% respectively. Usually, the black version is the black version of middle note

④ different original types correspond to different color saturation settings

in principle, for originals with flat and thin colors, the color saturation should be increased during processing. For the overall color deviation, different color correction methods (image/adjust) can be used

⑤ point enlargement rate (compensation amount) setting

point enlargement rate mainly depends on ink characteristics and printability. The point enlargement value can be compensated in turn in the point enlargement rate built-in compensation amount setting in computer software. For color newspaper printing, when various conditions are stable, the point enlargement rate (compensation) is usually set at about 25% - 30%

⑥ definition emphasis principle

in the process of image reproduction, the definition of the final copy is closely related to the definition, magnification, number of hanging lines and definition processing of the original. Due to the low overprint accuracy of newspaper printing, it is particularly easy to produce white edges during printing, which seriously affects the printing quality. Therefore, the reasonable sharpening should be determined according to the printing conditions

⑦ maximum ink volume setting

because the newspaper printing speed is fast, it belongs to the wet pressing method, and the maximum ink volume is usually set to 280% ~ 300%. If the total coverage of the dot area is too high, reverse transfer is easy to occur, especially when printing the third and fourth colors, and the dot is easy to expand. In addition, due to the low smoothness and strong ink absorption of the paper, if the total coverage of the dot area is too low, the ink is not enough to fill the paper pits and pores to form a smooth ink layer, thereby reducing the maximum color density and saturation. (to be continued)

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