The image processing software Photoshop (file/color setting/CMYK setting/CMYK mode/built-in) is a very important function for setting printing parameters. It can be set in terms of ink color, dot gain, color separation parameters, etc. . These parameters are set up for the equipment characteristics of a four-color offset system. It can also be used to create output files for other output methods (such as color inkjet), and to simulate offset printing processes for color separation. The details of the setting parameters and their respective parameters are described in detail below, which is very important for personnel of foreign printing technology. 1.Ink Options: This item contains the following two items: (1) Ink Color. This option provides the selection criteria for ink color. Options include Custom and some commonly used offset ink standards. Commonly used offset ink standards include, for example, SWOP (Specifications for Web Offset Publications) commonly used in the United States, Toyo inks commonly used in Japan, and Eurostandard commonly used in Europe. According to print papers such as coated paper, uncoated paper and newsprint, there are different standards. Users should know if their presses use these inks or which ones they prefer, and if they are close, they can use them. If the ink used deviates too far from the ink standard set in the options, you must develop your own ink standards. The Custom option is used to create your own ink standard. This option includes 9 calibration blocks, yellow, pink, blue, red, green, blue, synthetic black, black, black, and black [Y, M, C , MY (R), CY (G), CM (B), K (CMY), W, K], the first six colors have the greatest impact, they represent the six corners of the CMYK color space, respectively. The basic method for customizing the special ink color: print the used ink on its own printing system to the calibrated nine solid color blocks, measure the tristimulus value XYZ of each color block using a colorimeter, and then use the formula X=X / (X + Y + Z) and Y = (X + Y + Z) calculate the chromaticity coordinates x and y, respectively, where Y is the luminance coordinate, the value is small 0-100, X, y take 0-1. Then the measured Yxy is filled in the color coordinates of each color block and named and stored, thus completing the production of a specific ink color. In addition, you can use the setting button at the bottom of the dialog box to select the L"a"b" chroma space as the chroma value of each test patch. Yxy and L"a"b" are two expressions of the absolute chroma space. , two spaces can be converted between each other. Normally, when printing on coated paper, approximately SWOP (Coated) or Eurostandard (Coated) is used. For printing on offset paper, SWOP (Uncoated) or Eurostandard (Coated) may be used. Printing newspapers may be approximated using SWOP (Newsprint) or Eurostandard ( Newsprint). Domestic ink standards are not completely consistent with foreign inks, and their ink colors are not added to the ink table in advance, and similar inks cannot be found in the table. In this case, custom ink colors can be used. Another situation is to use a spot color ink to replace the primary color ink to produce special effects. For example, some packaging prints use spot color red instead of magenta ink, which looks better and more vivid than magenta. At present, a variety of non-offset color output technology is used more and more widely, such as the color inkjet output method, which uses inkjet ink also divided into four colors CMYK. Since many inkjet output software does not have the ability to automatically separate colors based on the characteristics of paper and ink, offset color separation settings can be used for simulation. The determination of the ink color standard is similar to the offset ink color determination method described above, except that the test color mark must be generated under certain conditions such as a machine, an ink, a paper, and an ink-jet speed currently used. (2) Dot Gain (network expansion). There are two ways to set up dot gain in Photoshop 5.0: a. Standard (standard mode): The network expansion has the greatest influence on the midtones, and the expansion rate of the 50% outlets is the largest. The dot gain value set in the standard mode is the enlarged value of the 59% dot. For example, setting a 20% dot gain ratio means that the midtone dot will be printed at 70% (50%+20%). In addition, the effect of dot gain on color printers is equally large, and different paper, inkjet speeds, and printer models will all lead to very different dot gains. b. Curves: In this mode, the dot expansion can be set in all the same [composite channel] and CMYK four-color channels. It can set the corresponding dot gain values ​​for up to 13 levels. Accuracy is higher than standard mode. In the "all the same situation, when the expansion rate of each channel of CMYK is forced to the same value, it is actually the expansion of the standard mode, the expansion of the network points from a point of 50% to a range of the entire gray ladder. This type of setting needs to be used. Go to the gray scale and use the density meter to measure the number of gray points at each level of the gray gradient above the gray scale, and fill in the table respectively.If the 20% gray scale of the original gray scale is printed, the measured network point is 30%. Enter 30 in the dialog box 20%. If you use four color channels to set their dot gain values ​​(don't choose the "all the same" method), it not only gives dot gain parameters for each color ink, but also compensates for the gray balance of the ink. The acquisition must test all CMYK four-color rulers one by one, and measure and fill in the same form as the gray scale.