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Four color printing and some knowledge explanation (Part 2)

Third, the color of pictures. About some professional terms such as overprint, overprint, hollowing out, spot color, etc. in printing, you can refer to some relevant basic printing knowledge, here only some common sense that must be paid attention to

1. Hollowed out

there is a line of blue words pressed on the Yellow bottom plate, then on the yellow version of the film, the position of the blue words must be empty. And vice versa for the blue version. Otherwise, blue things will be printed directly on yellow, and the color will change, and the original blue words will become green

2. Overprint

if there is a line of black words pressed on a red bottom plate, the position of the black words on the red version of the film should not be hollowed out

because black can suppress any color, if the black content is hollowed out, especially some small words, a slight error in printing will lead to the exposure of the white edge, and the contrast between black and white is large, which is easy to see

3, four color black

this is also a relatively common problem. Before output, you must check whether the black text, especially the small characters, in the publication file is only on the blackboard, and should not appear on other tricolor plates. If it does, the quality of the printed finished product will be discounted. When RGB graphics are converted to CMYK graphics, the black text will definitely become four-color black. Unless otherwise specified, it must be processed before the film can be output

4. When the picture is output in RGB mode

rgb mode, the rip system will generally automatically convert it to CMYK mode for output. But its color quality will be greatly reduced, and the finished products printed are light in color, not bright, and the effect is very bad. It is best to convert the picture into CMYK mode in Photoshop. If it is a scanned manuscript, it must go through the process of color correction before the picture can be used

IV. film hanging accuracy

the accuracy of hanging is generally called hanging eyes. The higher the accuracy of hanging, the more exquisite the printed product is, but it has a great relationship with paper, ink, etc. If you print a high hanging picture on ordinary paper (newspaper), the picture will not become more beautiful, but will become a mess (terrible). Therefore, before output, you must understand the printing of your printed matter, and using high activity San (acrylonitrile styrene copolymer) can well improve the above problems. What is the brush paper, and then determine the hanging accuracy

generally common paper and eyelet accuracy: imported coated paper or self-adhesive, etc.: imported offset paper, etc.: ordinary offset paper, etc.: line paper: line, and so on. The worse the paper quality, the lower the eyelet, and vice versa

before prepress output, we must pay attention to the following issues:

1. Select commonly used design and production software during production, such as PageMaker, etc., and try not to use word, etc

2. The mode of the pictures in the text must be CMYK mode, with an accuracy of at least 300*300dpi/pixel/inch

3. Check whether the words in the publication are four-color words. If so, change it to monochrome 100% black

4. If PageMaker, Weisi, founder and illustrator are used, their linked image files must be copied together with the original files

54 the hydraulic system should have a safety device for regulating pressure, and the Photoshop file should preferably be PSD (unconsolidated layer) to facilitate modification

6. Try to use common fonts, such as founder and wending. Try not to use rare fonts. If it has been used, CorelDRAW and illustrator first convert the text to the outline mode, which can avoid the problem that the output cannot be output because there is no such font in the output center. If there is a supplementary document, it must be copied together

7. Clearly inform the output center of the finished size, printing volume, printing paper, etc. of the printed matter, so as to facilitate the assembly and hanging

8. If the contents of the two pages are the same, but the black text parts are different (often encountered), then you only need to output the CMYK four colors on the first page and the K color on the second page, so as to avoid waste and save money. If there are only two colors (such as red and black) and the printing requirements are not high, it is only necessary to output them in the same color plate at the same time, and there is no need to divide them into two colors for output. You can deal with it when printing and plate making. It also saves money

point angle

Green: 15 degrees Red: 75 degrees yellow: 90 degrees Black: 45 degrees

generally, the dots are arranged neatly, so there will be angles in application. For example, when printing in monochrome, the line angle is mostly 45 degrees, which is based on the dots printed at this angle. For the visually most comfortable compressive strength, the gear with range is suitable and the existence of points that are not easy to detect, resulting in the effect of continuous gray tone. As for printing with two or more colors, we should pay attention to the combination of two angles, otherwise unnecessary patterns will be produced, which is called "moier". Generally, if the angle difference between the two is 30 degrees, there will be no collision. Therefore, generally, for two-color printing, 45 degrees will be used for the main color or dark color, 75 degrees will be used for the light color, and 45 degrees, 75 degrees and 15 degrees will be used for the three colors respectively. If it is a four-color printing, 75 degrees will be used for the red color, 90 degrees for the yellow color, 15 degrees for the green color, and 45 degrees for the black color. These perspectives are not limited by the seven national high-tech industrialization bases, but are changed according to different needs

source: Huicong printing industry channel

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