Color deviation and correction of printing color i

Color deviation and correction of printing colors in the screen

color correction has always been the most troublesome problem in computer graphics and printing, because many colors on the screen can't be printed at all, or there are serious color deviations. If they can't be corrected at the design stage, it's too late to wait until the finished product is printed. However, I can tell you that you don't need to spend too much time on this, because most people simply don't have the ability to effectively correct the color of their own devices

color correction

color correction is linked. From scanner, screen, output to printing, each layer of conversion steps are colored. China's paper industry once ushered in a short "spring" problem. The scanner scans a color card for correction, and makes correction by comparing the theoretical color with the color obtained by actual scanning. For the screen, you need to use a small camera pasted on the screen to correct it by reading the color value of a specific color block on the screen. Most people don't have the software and hardware mentioned above, so it's impossible to correct them at all. Most people can correct the brightness and contrast at most. This software is attached to Photoshop 5, and the installer can set it

rgb to CMYK color deviation problem

it should be emphasized here again that printing is printed with magenta, cyan, yellow and black inks (please refer to the introduction of colors in the home page), so the colors are specified by CMYK. As long as CMYK is determined, it means that the printing ink ratio is determined, and the color usually won't have much problem (from the point of view of ordinary people). However, the color in the computer is expressed in RGB mode, so to print RGB color, it needs to go through a step of color conversion. There will be two problems:

the first is the ink, and then re calibrate the sensor to work normally. There is no way to print all RGB colors. Usually, the high brightness color, fluorescent color and metallic luster cannot be printed. At this time, the program has to use the closest CMYK to replace it. If you find a triangle exclamation point in the selected color box when using Photoshop (refer to the right figure), or an exclamation point is added after the CMYK value, it means that the color cannot be printed

the second question is, what is the conversion standard for 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 shown on the screen. Usually, the biggest problem occurs in cyan. Without correction, the cyan seen on the screen (r:0 g:255 b:255) is a very bright color (the color block on the left of the right figure), but the cyan actually used for printing (c:100% m:0% y:0% k:0%) has a completely different feeling (the color block on the right of the right figure), and there are serious color deviation problems with a large number of cyan colors, such as blue and green

solution

1 Use CMYK to specify color

some software, such as CorelDRAW and Photoshop, will specially consider the correctness of the conversion between RGB and CMYK. As long as you directly use CMYK to specify color in the software, you can get a result quite close to the actual printing, so use CMYK mode to operate as much as possible. Photoshop can convert the image file into CMYK mode (menu: image mode CMYK color), which can completely avoid the use of colors that cannot be printed. The disadvantage is that most filters cannot operate in CMYK mode. There is really no way but to temporarily switch to RGB mode, and then switch back to CMYK mode after using the filter

2. Another way to query colors in conjunction with the "print color rendering table" is to use the print color rendering table to query the actual printed colors. The color rendering table (refer to the right figure) is a reference template of color values, which lists various combinations of CMYK for query. Therefore, when you want to choose a specific color, first find the desired color from the color table. Then, after clamping the extensometer, input the indelible CMYK value of the team's strength marked on the table into the software. For ordinary people, this is the most reliable color correction method. In actual use, it is certainly impossible to check the table one by one for all the colors appearing in the layout, as long as you confirm the key points (such as text, borders) or large-area coloring

color display table is a very important tool, but the price is not cheap. According to the manufacturer, paper size and color quantity, the price ranges from 300 to 1000, and most bookstores can't buy it. You should go to art clubs or bookstores specializing in selling art books. Otherwise, booksellers of art and drawing will participate in the computer exhibition every year, and they will also be sold at the booth

another thing is very similar to the color table, which is called the standard color ticket. This thing names the inks used in the printing system and prints samples one by one. The color inside must be modulated with special ink to be printed. It cannot be used in CMYK printing. Don't buy the wrong

printing art