Printing ink setup tips in photoshop

In the DTP system, there are many occasions need to convert the RGB color mode image file format to CMYK color mode, so that the color image file can be used for printing and copying, in the usual case, the Photoshop software for color mode conversion work . Since the two color modes are very different in terms of the expression of color fineness, there is a great difference in the quality of the image, and in the color mode conversion process, this difference is based on Photoshop software in printing inksets (printing inksetup). ) Changes in the settings.
In general, the difference in image quality has changed significantly in two areas:
1. Since the color gamut of the CMYK color mode is significantly smaller than that of the RGB color gamut, after converting to the CMYK mode, “super gamut color” may be generated in some color gamuts. The presence of this "ultra-chromatic color" makes the printing color gray.
2. When the two settings of the printing ink and the printing method are not properly set, the level of the image is lost. Especially at the level of the dark tone, the loss is even more serious. Because the dark area is often the area where "hyperchromatic color" is often generated.
Therefore, it is necessary to give sufficient attention and discussion to the setting of printing ink. This part of the work is essentially part of the commissioning of the electronic color separation and high-end scanners. In particular, some scanners for color plane scanners are installed under Photoshop software. Printing ink origami includes the following three elements: Colour ink, Dot Gain, and Grey Balance. ). In essence, the color ink referred to herein is not only referred to as a printing ink, but also a pigment used in an ink jet printer can be selected by selecting an item. Due to the difference in the hue and printing conditions of printing inks and printing pigments, color quality, dot gain, and neutral gray balance cause differences in image quality. Therefore, it is necessary to adjust the data of the above factors to ensure the image quality. of. And these data are only valid in the CMYK color mode.
One, neutral gray balance (Grey Balance)
In the theory of pigment subtractive coloring, equal amounts of cyan (C), magenta (M), yellow (Y), and trichrome are mixed in equal amounts to give black (K). However, because the pigments cyan, magenta, and yellow cannot all obtain ideal colors from processing and manufacturing, they often have different degrees of opposite colors in the cyan, magenta, and yellow colorants. For example, a small amount of magenta is contained in the blue pigment, and a small amount of red is contained in the magenta pigment. In the yellow pigment, it contains a small amount of red. And in actual printing, due to the different ink brands used, the yellow, red, and cyan inks have different hue. For example, there are magenta, magenta, or pink in magenta inks, and yellow or clear yellow in yellow inks. Therefore, after mixing the same amount of cyan, magenta and yellow inks, you cannot get a dark reddish black. To get a more pure black, you need to have a combination of different proportions of cyan, magenta, and yellow inks.
Such a combination of different proportions is not only the case in the black area, but also the different combinations of cyan, magenta, and yellow in the gray area. This is because the fineness of the dots is not exactly the same in the three regions of high light (0-25%), intermediate tone (25%-75%) and dark tone (75%-100%).
In each area, the grays composed of cyan, magenta, and yellow dots with different proportions of the three primary colors of ink are called neutral balance data in prepress and printing. Due to the sensitivity of the gray area to the color performance, under normal circumstances, when the neutral gray balance data deviates from the normal state, the gray will be biased to a certain color. Therefore, during the entire image reproduction process, neutral gray balance data is used as an important quality standard for monitoring the production process from prepress to printing. For example, in the image scanning operation, the gray area of ​​the original document deviates from the normal data of blue, which will cause the entire screen to become reddish due to lack of blue. In the printing operation, when the ink amount of a certain color is too large, the printing screen will be shifted to the hue with a large amount of ink in the gray area, and the balance of the blue, red and yellow inks in the gray area will be disturbed. Can cause the color cast of the entire picture.
Under normal circumstances, the correct neutral gray balance data for cyan (C), magenta (M), yellow (Y), and black (K) is obtained through the conventional proofing of specially designed color blocks. . The color block group consists of 2%-100% different tonal regions, and consists of different data of C, M, Y, and K. The color patches belonging to the neutral gray were confirmed by observation of proofs. From this, the proportions of the halftone dots in neutral gray balance are determined, and the reflection densities of the various tones and the curve of the data points of C, M, Y, and K dots can be plotted. In general, neutral gray Balanced data at 50% of the intermediate tone zone, C is about 7%-8% higher than Y, M, and at 90% of dark tone, C is about 5%-6% higher than Y and M, and In the high profile area, C is about 1% higher than Y and M. From the perspective of the neutral gray balance curve, the Y and M curves basically coincide, and from the neutral gray balance curve, the Y and M curves basically coincide, while the C curve is higher than Y and M to become an arched curve. Even if the ink hue differs, the difference between the Y and M curves will not be too far apart.
However, in the “printing ink setting” item, the percentage of neutral gray balance points in each area of ​​C, M, Y, and K cannot be input like some scanners, and only CMYK color curves can be input in the gray balance column. The Y value. Therefore, if you want to accurately get neutral gray balance data, you need to find the Y value of each color curve based on the neutral gray balance curve you draw, and then enter the color data. A correct neutral gray balance will favor the correct formation of colors when converting RGB images to CMYK color mode. Therefore, careful and careful data balancing of neutral gray balance will ensure the improvement of image quality.
Second, Dot Gain expansion (Dot Gain)
The expansion of outlets is an inevitable result of the printing process. The conventional printing currently used requires the ink to be absorbed by the printing plate, and the ink is pressed on the paper by pressure, such as letterpress printing, flexographic printing, and gravure printing. Or after the ink is absorbed by the printing plate, it is first transferred to the blanket, and then transferred to the paper by embossing, so as to complete the printing, such as the most commonly used offset printing. Therefore, all printing must have three conditions: 1. The ink needs to have a certain viscosity, so that it can absorb the printing plate, and there is a sufficient amount of ink. 2. There must be enough pressure to transfer the ink to the paper. 3, the paper must have the right ability to absorb ink. Only when the pressure, the amount of ink, and the conditions of the paper are matched with each other can a satisfactory printing be obtained. The problem arises because of the imprint expansion caused by the pressure. How to control it within a certain range in printing and how to provide prior compensation in prepress operations is an important point.
In any type of image printing, dots are a basic unit for accepting ink volume and are also the basic unit for printing. The transfer of outlets during the printing process will inevitably cause changes in the status of the outlets. This change of state will seriously affect the image quality.