Four-color printing:
As long as the three colors R + G + B collide in proportion, more than ten million colors can be generated. Why black? When the ratio of R, G, and B is equal, black can be produced, but it takes three inks to produce a color, which is not feasible from an economic point of view. In fact, the use of black is very much in the design process, which is why it is necessary to use four-color printing. Another point: after the black generated by RGB is compared with the black prepared directly by the ink, the former has a sense of voidness, while the latter feels more solid.
1. With the four-color principle, it is much easier for everyone to accept. It is equivalent to four films at the time of output, and is also equivalent to the four channels of cyan, magenta, yellow, black (C, M, Y, K) in the channels in PHOTOSHOP. The modification of the channel when we process the image is actually the change of the film.
2. Flat and hanging nets at mesh corners.
Mesh: per square inch, the number of dots placed, commonly used 175 mesh printed matter, newspaper from 60 mesh to 100 mesh, depending on the quality of the paper. Special printing has special meshes, depending on the texture.
Outlet: round. oval. diamond. Square. Diamond shape. FM outlets, etc. The picture above is composed of circular dots.
Net Angle: The angle between the straight line formed by the most closely connected dots and the horizontal line. The picture above is 45 degrees
Flat screen: The dots of the whole film are regularly and evenly distributed, and the size is the same, like a plane, no layering.
Hanging the net: The size of the outlet is different, and the mesh has a sense of hierarchy.
Precautions before outputting film
First, the file format
Most of the output centers now use Founder Grid Century RIP (pspnt) output system, and HQ510, Israel's Sai Angel, Heidelberg and other phototype output systems. All support postscrit printer description files. That is the suffix name. ps file.
Other common file formats that can be directly RIP output are: s2, s72, ps2 (Founder Book Edition), EPS, TIF, PDF, etc.
At present, the most commonly used design software: Photoshop, pagemaker, coreldraw, illustrator, etc., can generate a PS file or PDF file through the postscrip virtual printer, and s2 generated by some founder software such as Founder Book Edition, Vespa, Feiteng, etc. , Ps2, ps files can also be directly output in Founder Century RIP, but other output systems are not supported.
There are some other word processing software such as word, wps2000 and so on, which can also generate ps files through postscript virtual printers. In fact, pre-press output must be processed such as imposition, registration guidelines, cutting lines, etc., and word, wps2000 and other software can be said to be powerless in this regard, especially the color draft, once completed, go to the later stage Processing will bring great difficulties. Therefore, try to choose a series of professional design and layout software such as pagemaker.
Second, the format and accuracy of the picture
Modern offset printing uses offset printing (four-color overprint), that is, the color picture is divided into four colors: cyan (C), product (M), yellow (Y), black (B) four-color dot film, and then dry Formed into PS version, printed four times through the offset printing machine, and then came out as a colored printed product.
If you print a high-mesh picture on general newsprint (newspaper), the picture will not only become more exquisite, but will become a mess (it is unbearable), so you must understand the printing of your prints before output What is the paper, and then determine the accuracy of the net.
Commonly used paper and hanging mesh accuracy: imported coated paper or stickers, etc .: 175-200 lines, imported offset paper, etc .: 150-175 lines, ordinary offset paper, etc .: 133-150 lines, newsprint: 100-120 lines, to By analogy, the worse the quality of the paper, the lower the mesh size, and vice versa. [next]
The issues that must be noted before output before printing are:
1. Use more commonly used design and production software during production, such as pagemaker, etc., as much as possible, such as word.
2. The mode of the picture in the text must be CMYK mode, and the precision is at least 300 * 300dpi / pixel / inch.
3. Check whether the text in the publication is a four-color character, and if it is, change it to monochrome 100% black.
4. If you use pagemaker, Weisi, Founder Book Edition, Illustrator, you must copy the linked image file and the original file together.
5. Photoshop files are preferably psd (unmerged layers) files for easy modification.
6. Use common fonts as possible, such as Founder and Wending. Try not to use rare fonts. If used, CorelDRAW and Illustrator first convert the text to an outline method to avoid the problem that the font cannot be output because there is no such font in the output center. If there is a supplementary word file, the supplementary word file must be copied together.
7. Clearly inform the output center of the finished product size, printing volume, printing paper, etc., to facilitate imposition and net hanging.
8. If the content of the two pages is the same, but the black text is different (often encountered), then only the four colors of CMYK on the first page and the K colors of the second page can be output, 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, you only need to output them in one color version at the same time, and there is no need to divide them into two color outputs. Just do it when printing plate making. Also save money.
Dot angle
Green: 15 degrees red: 75 degrees yellow: 90 degrees black: 45 degrees
Generally, the dot arrangement of the net is neat, so there will be angles in the application. For example, when printing in monochrome, the screen angle is mostly 45 degrees. This is based on the dots printed at this angle, which is the most visually comfortable. And it is not easy to detect the existence of dots, which results in continuous gray tone effect. As for the printing of two colors or more, we must pay attention to the angle combination of the two nets, otherwise, unnecessary patterns will be produced, which is called "moier" (Moier). Normally, if the angle of the two nets is different by 30 degrees, there will be no net hit. Therefore, in general two-color printing, the main color or dark color is 45 degrees, the light color is 75 degrees, and the three colors are 45 degrees, 75 degrees and 15 Three angles such as degrees, if it is the four colors of color printing, 75 degrees for red, 90 degrees for yellow, 15 degrees for cyan and 45 degrees for black. And these angles are not limited, they are changed according to different needs.
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