If four-color printing is carried out on a four-color printing machine, the most common and recommended order is magenta, cyan, then yellow and finally black; Or CMYK order. This order can reduce unnecessary chromatic aberration caused by multi-color overprint. Color difference is the amount of unnecessary pollutants obtained by the superimposed second color ink owned by monochrome ink.
For example, when 100% yellow block and magenta block are superimposed, I hope to get a red tone, but I don't. The actual result is orange tone, because magenta ink usually contains about 50% mixed yellow ink. When yellow ink is printed on magenta ink, the yellow ink will be mixed with the following colors in the process of wet overprinter, and finally the overprinter tone will be generated, and the color will be slightly yellow than ideal.
Similarly, cyan ink also contains 25% magenta ink. This is why a 100% cyan and magenta color block does not produce the expected blue tone, but looks a little purple. Relatively speaking, yellow ink is cleaner and purer.
When four-color printing is carried out on a two-color printer, the color of the first printing process is very important. They are yellow and black. The contrast of yellow is so small that it is difficult to see it alone. Observing the yellow on white paper with a blue filter (such as Kodak Wratten # 47) can make the yellow tricolor light look like black. In fact, PMT (photomultiplier tube) roller scanner or CCD (charge coupler) platform scanner and development densimeter all use the same filter. Because the color of yellow is difficult to see, we should use reflection densitometer to control yellow.
Black will not affect the tone of a color, but will only make the color darker and dirtier. Adding black to CMY three-color printing will only increase the density to expand the dynamic range and establish contrast. Black is not only used to achieve gray balance in neutral gray. Gray balance is achieved by screening halftone dots, with magenta and yellow dots smaller and cyan dots larger.
A typical neutral gray balance consists of 65% cyan dots and 50% magenta and yellow dots. By the way, no matter whether black is added to any color, the final result is to deepen the color. Conversely, no matter what kind of white is added to any color, it will eventually make the color lighter. The hue remains the same. Because screening can make white paper appear and mix with colors to make the colors look lighter.
Back to the problem of printing color sequence, in order to prevent any possible sticking problems, in the first printing process, yellow is printed first, and then black is printed. If there is any sticking problem caused by ink film thickness due to printing plate coverage or incorrect ink viscosity, yellow will stick to black without being noticed. It is recommended not to change the color sequence, because it is yellow-black overprint, which leads to yellow dirty.
In the second printing process, the two colors printed are very important magenta and cyan. Magenta and cyan bear the task of producing secondary tones, such as blue sky and water. In the second printing process, when cyan and yellow are mixed, they also partially undertake the task of generating grass and leaves. When magenta is mixed with yellow, it also partly undertakes the task of generating skin color and bread, meat and other foods.
When printing four colors on a monochrome printer, it is recommended to simply print black first.