The standardization and dataization of color printing operation

The standardized and data-controlled production process refers to the “standardization of operating procedures and procedures, the quality control of the whole process, and the control of data related factors.” Through data and standardization to stabilize the variable factors in photocopying, plate making, proofing and printing, effective Control the information conversion and transmission in the production process of color newspapers, perform color processing as perfectly as possible, and achieve true color reproduction.

As the actual conditions of materials, equipment, etc. used will continue to change, so there are many differences in the specific operations, so this paper only plays a role in the overall understanding of the digitization and standardization of the printing process. for reference only.

1 The standardization and dataization of photocopying process

The standardization of phototypes involves the entire process from text entry to film flushing and inspection. Under the condition that the hardware and software systems are working properly, reasonable phototypesetting process data should be formulated according to the printed raw materials (paper, ink, plate, etc.) and printability (ink volume, pressure, ink-water balance, etc.).

1) Standardization of phototypesetting process

1 Black and white field tone range

This is an important indicator of image quality. The longer the range of adjustment, the greater the image contrast and the better the visual effect. However, the range of tone adjustment is limited by the conditions of the post process. If the white field dot on the color separation film is too small, the graphic point may not be printed on the printing plate or printed on paper. If the dot size is too large, it may be formed during printing. Paste version, dark tone level obvious loss. Therefore, different printing conditions should have different gradation ranges. The Whitefield should give up on small areas (such as: white eyes, shirt buckles, etc.). The printing characteristics of newspapers determine that the scope of their tone is narrow, usually 3% to 90%. In case of a large-scale white field, the minimum network point may be set at 4% (to prevent large areas from being screened), and the black field is selected to be 80% to 85%. The black field can be a small number of parallels, but it is necessary to prevent large areas from being netted and erased.

2 gray balance curve

During the determination of the gradation range, at the same time, the percentage of the dots of each color separation plate that can guarantee the restoration of the original neutral ash is determined. For Taiyuan Gao's Rolli four-color offset inks, the percentage of dots in the different gradation ranges of the neutral gray's color separations is: In the high light, the C version should be higher than the M version and the Y version, 2%~3. %; the middle tone at the C version is higher than the M version and the Y version of 8% to 9%; the dark tone at the C version is higher than the M version and the Y version of 10 to 12%.

3 fixed level curves and black curves for different original types

Since the original has transmission and reflection points, and the density of the different originals is not the same, some abnormal originals may be too thin or too thick. Therefore, 5 fixed-level curves can be set for transmission and reflection originals respectively: Different density ranges and different thicknesses of the manuscript, the middle tone as a standard value for a fixed level curve, the remaining four curves corresponding to the middle tone adjustment ± 5% or ± 10%. Black Edition is usually in the tone of the black version.

4 Different Original Types Correspond to Different Color Saturation Settings

In principle, the color of a manuscript with a relatively flat and sloppy color should be emphasized during processing. For the case of an overall color cast, different color correction methods (image/adjust) can be used.

5 network expansion rate (compensation amount) setting

The dot gain rate mainly depends on the ink characteristics and printability, and the dot gain values ​​can be compensated in turn by setting the dot gain rate in the computer software. For color newspaper printing, the dot gain rate (compensation amount) is usually set to about 25% to 30% under stable conditions.

6Clarity emphasis principle

In the process of image copying, the clarity of the final copy is closely related to the definition of the original document, the magnification ratio, the number of hanging lines, and the sharpness processing. Due to the low accuracy of newspaper printing overprinting, printing is particularly prone to white edges, which seriously affects the printing quality. Therefore, reasonable sharpening should be determined based on the printing conditions.

7 maximum ink setting

Due to the faster printing speed of newspapers, it is a wet and wet method, and the maximum ink volume is usually set to 280% to 300%. If the total coverage area of ​​the dot area is too high, especially in the printing of the third color, the fourth color, the reverse transfer easily occurs, and the dot is easy to expand. In addition, due to the low smoothness of newsprint and the strong ink absorption, if the total coverage of the dot area is too low, the ink will not be sufficient to fill the paper pits and pores to form a smooth ink layer, thereby reducing the maximum color density value and saturation. degree. (to be continued)