Basic knowledge of printing (1)

Four-color printing:

As long as the R+G+B tri-colors collide in proportion, more than 10 million colors can be generated. Why black? Why, it can produce black when R.G.B ratio is equal, but three inks can generate a color? From the economic point of view, it is not feasible. Actually, the use of black is very much in the design process. This is actually why we use four-color printing. There is another point: RGB generates black and direct deployment with ink. Compared with the black color, the former has a sense of emptiness, while the latter feels more immersive.

1. With the four-color principle, it is easy for people to accept much more. It is equivalent to the four films at the time of output. It is also equivalent to four channels of cyan, magenta, yellow, black (C, M, Y, K) in PHOTOSHOP. Channels. The modification of the channel when we process the image is actually a change to the film.

2. Mesh outlets Mesh and flat screen. Mesh: Per square inch, the number of outlets, 175 mesh for common prints, 60 to 100 mesh for newspapers, depending on paper quality. Special printing There are special meshes, depending on the texture. Dots: sub-circular. Ellipse. Diamond. Square. Diamond. FM mesh, etc.. Web: The angle between the straight line and the horizontal line formed by the most closely connected dots. There are 30 Degrees, 45 degrees, 75 degrees, 90 (0) degrees. Flat screen: The dots of the entire film are regularly distributed evenly and have the same size. It is like a plane and has no sense of layering. The above diagram shows the flat net: the dot size is not the same, and the mesh has a layered sense.)

What to do before exporting a film

First, the format of the file

The output center is now mostly using the Founder Grid RIP (pspnt) output system, and the HQ510, Israel's Sailing Angel, Heidelberg [specialty, product, encyclopedia] and other phototype output systems. All support postscrit printer description file. This is the file with the .ps extension.
Other common file formats that can be directly RIP output are: s2, s72, ps2 (Founder Edition), EPS, TIF, PDF, etc. At present, the commonly used design software: photoshop, pagemaker, coredraw, illustrator, etc., can all generate a PS file or a PDF file through a postscrip virtual printer, and some Founder software such as Founder, Verizon, and Feiteng s2. The ps2, ps2, and ps files can also be output directly at the Founder Century RIP, but other output systems do not. There are other word processing softwares such as word, wps2000, and so on, which can also generate PS files through postscript virtual printers. In fact, the prepress output must be processed such as imposition, registration line, cutting line, etc. However, word, wps2000 and other software can be said to be powerless in this regard, especially the color draft, once done, go to the later Processing will bring great difficulties. Therefore, try to use pagemaker and a series of professional design and layout software.

Second, the picture format, accuracy

Modern offset printing uses offset printing (four-color overprinting), that is, the color picture is divided into four colors: blue (C), product (M), yellow (Y), black (B) four-color dot film, and then drying Into the PS version, after four offset printing presses, it is colored printed products.

The printing picture is different from the usual computer display picture. The picture must be in CMYK mode, but not in RGB mode or other modes. When the output is converted into pictures, that is the precision: dpi, the printing image with a minimum theoretical accuracy to reach 300dpi / pixel / inch, and usually everybody often see the beautiful pictures on the computer, on the monitor feel very beautiful, in fact Most are 72dpi RGB mode pictures, most of which cannot be used for printing. The pictures used cannot be based on the display. Do not look at the picture because it is very fine with acdsee or other software. After zooming in, it is considered as a print. It must be opened with photoshop. Use a picture size to confirm its real value. Accuracy. For example: If the resolution of an image is 600*600 dpi/pixel/inch, then its current size can be enlarged to more than double. If the resolution is 300*300dpi, then it can only be reduced or larger and cannot be enlarged. If the picture resolution is 72*72 dpi/pixel/inch, it must be reduced in size (dpi accuracy will be relatively large) until the resolution becomes 300*300 dpi. (When using this function, set "Redefine pixel" in image size option in photoshop to none.)
Common picture formats are: TIF, JPG, PCD, PSD, PCX, EPS, GIF, BMP, etc. When making a draft, TIF color, black and white bitmap, EPS vector or JPG=

Third, the color of the picture

With regard to some technical terms such as overprinting, overprinting, hollowing out, and spot colors on printing, we can refer to some of the relevant printing basic knowledge. Here only some common sense that must be noted.

1, empty
There is a blue line on the yellow bottom plate, then the blue word on the yellow plate of the film must be empty. On the contrary, the blue version is also the same. Otherwise, the blue thing is directly printed on the yellow, and the color will change, and the original blue word will turn green.

2, overprint
There is a line of black on a red base plate, and then on the red plate of the film, the position of the black characters should not be hollowed out. Since black can suppress any color, if the black content is hollowed out, especially for some smaller characters, a slight error in printing will lead to white edges, and the contrast between black and white is relatively large and it is easy to see.

3, four color black
This is a more common problem. Before outputting, it is necessary to check the black text in the publication document, especially the small characters. It is not only on the blackboard, but it should not appear on other three-color editions. If this is the case, the quality of the printed product will be discounted. When the RGB graphics are converted to CMYK graphics, the black text will definitely change to four-color black. Unless otherwise specified, it must be processed before the film can be exported.

4, the picture is RGB mode
When the RGB mode picture is output, the RIP system will automatically convert it to CMYK mode output. However, its color quality will be greatly reduced, and the printed products will be light in color and will not be bright. The effect is very poor. The picture is best converted to CMYK mode in photoshop. If it is a scanned manuscript, then it must go through the process of color correction and the picture can be used.