In printing, different shades of the same color are expressed by using inks of different thickness and density.

As shown in picture 1, the above is the normal effect we see, from 0% gray to 100% black. If you enlarge the print enough,  what you actually see is something like this: some dots of different thickness and density are covered on the paper. 

But the dots are small enough,such as the commonly used 157 lines(Line Per Inch) and 200 lines (Line Per Inch), you can see the above effect.

Through the dots,we only use one black ink,and can also print the effects of different shades, of black, white, that the naked eye can see.100% is pure black, 0% is colorless, and the middle is gray. 

Through different densities and densities ofhalftone dot, it can be shown the effect of 100%, 80%, 50%, and 20%

Double color overlay halftone dot

We combine CMYK four colors in pairs, one color is 100%, and the other color is from 0% to 100%.

For example: M+C=blue; through different dots of C (M=100%, C=0-100%), more different blues can be obtained; 

Four-color halftone dots and software settings

Through the different dots of CMYK four-color ink, from 0%-100%, theoretically any color can be obtained.

When we set the color on the software panel, the percentages of the four colors of CMYK correspond to the dots of each color.

Summarize

1. When printing, it is used to cover the different thickness and density of ink to express the different shades of the same color;

2. Through the dots, we only use a black ink, and can also print the effects of different shades of black, white, and gray that the naked eye can see. 100% is pure black, 0% is colorless, the middle is gray, and the other C blue, The three colors of M magenta and Y yellow are the same;

3. Through CMYK four-color ink with different dots (from 0%-100%), theoretically any color can be obtained;

4. When we set the color on the software panel, the percentages of the four colors of CMYK correspond to the dots of the respective inks.