Correction of screen and printed colors
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Color correction has always been the biggest headache for computer graphics and printing, because many colors on the screen are not printed at all, or there is a serious color shift. If it can't be corrected at the design stage, it will not be too late after the finished product is printed. It is. But I can tell you that you don't have to spend a lot of time on this head, because the average person has no ability to perform effective color correction for his device.
Color correction
Color correction is interlocking. From scanner, screen, output to printing, each layer conversion step has a color shift problem. The scanner scans a calibration color card and corrects it by comparing the theoretical color with the color obtained by the actual scan. On the screen, a small camera attached to the screen is used to correct by reading the color value of a specific color block on the screen. Most of the above mentioned soft and hard bodies are not available, so it is impossible to make corrections at all. At most, most people can correct the brightness and contrast. This software is attached to Photoshop 5, and can be set by someone who has installed it.
RGB to CMYK color shift problem
Here again, it is necessary to emphasize that printing is printed with magenta, cyan, yellow and black inks (please refer to the introduction of color in the homepage), so the colors are all specified by CMYK. As long as CMYK is determined, it means printing. The ink ratio is determined, and the color usually does not have much problem (as far as the average person is concerned). However, the color in the computer is expressed in RGB mode. Therefore, to print the RGB color, it is necessary to go through a color conversion step. Two problems will occur here:
The first is that there is no way for the ink to print out all the RGB colors. Usually high-brightness colors, fluorescent colors, and metallic luster are not printed. At this time, the program has to be replaced with the closest CMYK. If you use Photoshop, you will find that the selected color square has a triangle exclamation mark (refer to the right), or an exclamation point after the CMYK value indicates that the color cannot be printed.
The second question is, what conversion standard is based on RGB to CMYK? Even if an RGB color can be converted to CMYK, it does not mean that the actual ink color will be the same as the color displayed on the screen. Usually the biggest problem is that it occurs on cyan. In the uncorrected case, the cyan (R:0 G:255 B:255) seen on the screen is a very bright color (the left color block on the right), but the actual printing cyan (C:100% M) :0% Y:0% K:0%) is a completely different feeling (right color block on the right), with a lot of cyan colors, such as blue and green, have serious color cast problems.
solution
1. Use CMYK to specify color
Some software, such as CorelDRAW and Photoshop, will specifically consider the correctness of conversion between RGB and CMYK. As long as you use CMYK to specify the color directly in the software, you can get results that are close to the actual printing, so use CMYK whenever possible. Mode to operate. Photoshop can convert the image file into CMYK mode for editing (MENU: Image > Mode > CMYK color), so you can completely avoid the use of unprintable colors. The disadvantage is that most filters can't work in CMYK mode. The method has to be temporarily converted to RGB mode, use the filter and then switch back to CMYK mode.
2. Query color with "Printing color table"
Another way is to use the printed color table to query the actual printed color. The color table (refer to the right) is a reference template for color values, and a list of various combinations of CMYK is available for query. So when you want to choose a specific color, first find the desired color from the color table, and then input the CMYK value marked on the table into the software. For the average person, this is the most effective color correction method. In actual use, it is of course impossible to check all the colors appearing in the layout, as long as the focus (such as text, frame line), or large-area coloring is confirmed.
The color table is a very important tool, but the price is not cheap. According to the manufacturer, the size of the paper and the number of colors, the price ranges from 300 to 1000, and most of the bookstores can't buy it. You have to go to the art club or specialize. Go to the bookstore selling art books. Otherwise, the annual computer exhibition will have exhibitors of art drawings, and there will be sales at the booth.
There is another thing like the color chart, called the standard color ticket, which is to name the ink used in the printing system and print the samples one by one. The color inside must be printed with a special ink, can not be used in CMYK printing, do not buy the wrong.