Detailed Prepress Operation - Separation Work Paper 3

Third, the manuscript printing manuscript operation

The use of prints as originals in electronic color separations is extremely high. When prints are used as manuscripts for color separation, only the following three issues are mainly addressed: (1) moire and sharpness, (2) gradation reproduction methods, and (3) backside photocopying to ensure image separation quality.

1. Moire and sharpness: Since the printed matter is the dot to reproduce the image, when the print job is performed as a manuscript, the dot shape of the original, the scanning line, the number of the screen lines, and the screen angle will cause the problem. Moire occurs in the color-processed image, resulting in deterioration of image quality. The method to eliminate the moiré in the actual color separation includes (1) making the network point halo, that is, adjusting the focal length of the sampling head lens until the print halo. (2) Change the number of scan lines, dot shapes, and net angles, that is, when scanning, use different scan lines, dot shapes, and Y, M, and CBK four-color screen angle distributions when the original is copied. (3) Change the subtle level of control parameters emphasized in the electronic color separation machine. The first is to change the relationship between the SHARP and SMOOTH binary values ​​in the subtle level, that is, to decrease the SHARP to improve the SMOOTH; second is to change the subtle levels to emphasize the multiple parameters in the composition. (4) Increase the scanning aperture. Specific operations should be combined with the above methods according to the status of the originals and the purpose of copying. At the same time, we should let customers know that the separation and copying of printed manuscripts will inevitably reduce the clarity of finished products, that is, reasonable choices should be made when both the degree of moire and the degree of clarity decrease are taken into account.

2. Hierarchical reproduction method: the original manuscript contrast is relatively small. When the white/black calibration is performed, the white field should be raised two steps forward. The black field should be advanced one step. The correction can be the same as the color photo. Methods, the intermediate tone levels need to be properly improved.

3. Back photocopies: Back photocopies are caused by too thin or double-sided printing on the printed manuscript. Therefore, in the actual color separation, when the original towel is attached to the roller, the original should be lined with black paper. If the original is a single-side printed matter printed on thin paper and the image contrast is to be increased, the white is covered with white. Paper is appropriate.

When the printed product is scanned for color separation, it should also be noted that the white balance point needs to be selected on the white portion of the original, and the white balance is selected after the automatic balance calibration is completed.