In the printing and publishing process, the materials provided to the printing personnel must meet the standards described in the SWOP parameter description, and the printing personnel use this as a premise to perform specific color control to ensure faithful reproduction. The following reference is based on the guidelines of the five-level publishing offset printing paper and thermosetting four-color ink.
Printing machine production guidelines
In the past few years, the new type of printing machine has developed to be more stable and faster in production speed. Many printing processes have gradually changed to positive printing. At the same time, more and better measurement and control technologies have appeared, which have improved quality. In the production process of many printing machines, the dot expansion problem has decreased significantly. In the specific printing machine test conducted by SWOP, the dot expansion has been controlled at 18% or even lower. In other tests, the expansion of printing and publishing outlets remained at around 24% of the standard.
The job of the printing production staff is to match the printed proofs visually. Since SWOP specifies that the dot expansion value in proofing is about 20%, the requirements for the printing production process are higher and more perfect. Only in this way can it be matched with the proofs most closely. These guidelines play a very good role (make printed products more acceptable), because it can adhere to the COLORBALANCE (color balance) and PROCESSCONTROL (process control) guidelines during the printing process. As we all know, in the process of copying, the "weight of the paper" is often less important than color balance and color shift. It should also be emphasized again that no matter how high or low the network is, it is impossible to comment on its quality. Once it loses control or is unstable, it is harmful.
Color control strips for printing industry personnel
A color control strip suitable for measurement must be included on the printed material. The control bar should use 133 lines of screen lines, including solid color patches for each color; 25%, 50%, and 75% color patches; two-color and three-color overprinted solid overlay colors; and visually The obvious degree of network expansion. The relationship between the trimmed size of the publication and the cut size of the web should be within the range that allows the control strip to exist.
The control strips described above can be used to obtain GATF / SWOP product control strips through GATF.
Film copying and plate making
In the process of film copying, the resolution object control ruler and CT ruler should be combined to control the degree of film copying, copying, and plate exposure. Products that meet this requirement include UGRA plate control ladders and GATF plate control strips.
Positive plate making and negative plate making
Although most printed proofs are made using traditional negative plates, the printing of publications can use both negative and positive plates. Normally, the positive image plate-making tends to shrink by several percentage points, while the negative image plate-making tends to expand by several percentage points. In order to meet the needs of removing dirt, cutting or extending the printing life of the printing plate, it may exaggerate the expansion and contraction of the dots during the exposure. Due to the difference in plate-making procedures, it is normal for deviations of 5% or more to be printed with negative and positive plates. The total dot expansion value and total tone value increase range suggested here are wide enough to include the difference between plate making and other conventional processing processes.
The impact of computer-to-plate (CTP)
The design of the CTP plate-making machine is to ensure that the fixed dot percentage in the electronic file is accurately copied to the printing plate. The CTP system has a stronger ability to change the dot size specified in the electronic file. It is necessary to optimize the CTP when outputting, so that the final printing effect can best match the provided SWOP proofs.
Super Calendered (SC) paper
Some special offset publications are printed on super calendered paper (SC paper). As with other production materials, the purpose of printing is to match the submitted SWOP proofs as visually as possible. The acceptability of the matching is up to the customer, but there are some techniques that can improve the potential of matching the printed images of SC paper with SWOP proofs. If possible, the film and electronic files provided by SC paper printing should meet the following conditions:
The number of screen lines for the output image should be 120 lines per inch.
According to the performance characteristics of the printing press, the maximum TAC value should be selected between 240% and 260%.
The color separation curve is 4% to 6% lower than the standard SWOP negative color separation curve in the middle tone to compensate for the increase in the dot expansion value when printing on the surface of SC paper.
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