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.
Dot: sub-circle. Ellipse. Diamond. Square. Diamond-shaped. Frequency mesh. The above figure is composed of circular dot.
Net angle: the angle between the straight line and the horizontal line formed by the most closely connected dots. The above figure shows the 45 degree flat screen: the dots of the entire film are regularly distributed evenly and have the same size, like a plane, without layering. The above figure is the flat net hanging net: the dot size is not the same, the mesh is layered)
What to do before exporting a film
First, the format of the file
Most of the output centers now use the Square Grid Century RIP (pspnt) output system, and the HQ510, Israel's Sailing Angel, Heidelberg 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 the 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.
Fourth, film hanging precision
Hanging net accuracy is generally referred to as hanging nets. The higher the precision of the netting, the finer the printed products, but it has a greater relationship with paper and ink. If you print on a regular newsprint (newspaper) a picture with a high mesh size, the picture will not only become more exquisite, but will become a mess (miserable). Therefore, you must understand the printing of your printed matter before exporting. What is the use of paper, and then determine the accuracy of the net. General common paper and hanging mesh accuracy: imported coated paper or stickers, etc.: 175-200 lines imported offset paper, etc.: 150-175 lines of ordinary offset paper, etc.: 133-150 lines of newsprint: 100-120 lines to By analogy, the poorer the quality of the paper, the lower the hanging net, and vice versa.
in conclusion
Before printing, you must pay attention to the following issues:
1, when the production of more commonly used design and production software, such as pagemaker, etc., like the word as much as possible.
2. The mode of the picture in the text must be CMYK mode, with a minimum accuracy of 300*300 dpi/pixel/inch.
3. Check if the text in the publication is a four-color word. If it is, change it to monochrome 100% black.
4. If pagemaker, WS, Founder, and Illustrator are used, the linked image file must be copied along with the original file.
5, photoshop file is best psd (unmerged layer) file, in order to facilitate the modification.
6, the font as much as possible using common fonts, such as Founder, Wen Ding. Try not to use rare fonts. If used, coreldraw and Illustrator first convert the text to outline, which avoids the problem that the output center cannot output without such a font. If you have a make-up file, you must copy the make-up file.
7, clearly told the output center print product size, print volume, printing paper, etc., to facilitate the imposition and hanging net.
8, if the two pages are the same, but the black text is different (frequently encountered), then only the first page of the CMYK four-color, and the second page of the K-color can be, so as not to waste, but also save money. If there are only two colors (such as red and black) and the printing requirement is not high, it is only necessary to output it in one color version at the same time, and it is not necessary to divide the output into two colors. Deal with the printing plate. It also saves money.
Network point of view
Blue: 15 degrees red: 75 degrees yellow: 90 degrees black: 45 degrees The arrangement of the general network is neat, so there will be an angle in the application, such as monochrome printing, the angle of the cable is mostly 45 degrees , This is based on this point of view of the printed network, for the visually most comfortable and difficult to detect the presence of outlets, resulting in continuous gray tone effect. As for printing with two or more colors, it is necessary to pay attention to the combination of the angles of the two networks. Otherwise, an unnecessary pattern will be created, which is called "Moier". Usually the difference between the angles of the two nets is 30 degrees, no net collision will occur, so the general two-color printing, the main color or dark color with 45 degrees, light color with 75 degrees, three colors are respectively 45 degrees, 75 degrees, 15 Degrees and other three angles, if it is the four-color printing, they are red with 75 degrees, yellow 90 degrees, green 15 degrees and black 45 degrees. There is no certain limit to these angles. They are changed according to different needs.
What is Postscript?
Postscript is a programming language designed specifically for printing graphics and text. It is independent of the media being printed, whether you print on paper, film, or on the screen. It is a page description language, similar to the HTML language.
Postscript was proposed by Adobe in 1985 and was first applied to Apple's LaserWriter printer. The main goal of Postscript is to provide a device-independent language that can easily describe images. Being device independent means that an image does not need to be described by the characteristics of any specific device (for example, the resolution of the printer), so this description can be used for printing on other Po stscript printers without any modification.
Postscript as a language, has its own set of grammar and format rules, if you are interested in this, please visit A ​​dobe company's website http://, Adobe company has a very comprehensive information.
Postscript files are stored as text, similar to HTML files. You can see this by simply opening a Postscript file with WordPad, as shown in Figure 1. The Postscript file itself describes the features and parameters of the image to be displayed or printed in the Postscript language. When the Postscript file is displayed or printed, it is interpreted and executed by the Postscript interpreter, and the specific printing or display is performed to obtain the desired image. . Figure 2 shows the Postscript file in Figure 1 in a Postscript file reader. You can see that the Postscript file is interpreted and displayed, resulting in a colored page.
Postscript files have many advantages over other formats. The above mentioned device independence is a very important point. Postscript files also have the advantage of being independent of the operating system platform. Because many Unix graphics environments themselves have support for Postscript as part of the core, so whether you are using a Windows* operating system or a Unix* operating system, you can read and print P ostscript files. This makes communication easier. . Because Postscript files are stored in text, the files are small and suitable for transmission over the Internet. There is also a unique advantage in printing and displaying on Postscript devices (printers, monitors) for the best results.
There are several ways to generate Postscript files:
(1) You can refer to Postscript's language format and edit it directly with your text as needed