Pre-printing dot pre-processing

After the color original is scanned and input into the computer, it is also necessary to perform the gradation compression processing on the image in order to realize the ideal dot restoration. Under normal circumstances, in the high-contrast manuscripts, the gradation density contrast is mostly greater than the gradation density range of the printed matter, and linear equal-area-average compression cannot be performed when gradation adjustment compression is performed. The high school tune the level to compress some less, the secret tune level should compress some more, in order to make the high level section level density difference to pull apart, the intermediate tune theme level is deeper, and the dark tune section level density is flat. For the color separation curve, at the 50% screen point, the general product network needs to be compressed by 15%. Offset printing can be done at high light. For a flexible version that continuously adjusts the image, 2% to 3% of protection points should be given under normal circumstances.

In all kinds of printing methods, dot gains will be more or less encountered. In particular, dot gains often occur in flexo and offset printing. In the case of flexo, there are not only dot enlargement problems, but also printing plates. The combination of bending deformations causes flexographic offset problems. According to this kind of situation, generally make the test printing plate, carry on the printing experiment, obtain the information that enlarges and distorts according to the experimental result, carry on the compensation treatment through pre-press processing.

In the prepress stage, “reducing” the size of the dot in order to compensate for dot gain in printing, there are mainly two pre-processing methods: one is to adjust the level curve of dot gain, and finish before the film is out. The other is The calibration of the laser photodischarging is completed when the screen is screened. It is suggested that the second method is adopted. According to the characteristics of the printing method, the film printed by the laser image aligner is printed on the film. The dot gain is significantly reduced, and the halftone dots in the middle tone are 5% to 10% smaller than the ordinary printing plate. , And can make 0.5% to 3% of the dots are clearly reproduced on the film and plate.