Why offset printing needs to copy pictures through wind spots

1) Continuously adjusting the film During the process of copying, the transmission of the density is difficult to control, and the image copy quality is difficult to guarantee.

2) Since the principle of photosensitive printing of offset printing plates is very different from the principle of silver illumination, the printing plates that are printed out have only two states of ink and non-inking. The printed results are only two levels of colored and non-colored, and they cannot be like silver. The salt sensitization material can change the gradation by changing the density of silver particles.

3) Even if a continuously-tuned printing plate can be developed, the offset printing machine cannot control the image density through accurate ink layer thickness, thereby completing the image-level reproduction.

Therefore, the continuous tone image of the manuscript must be invaded into its own independent dot. The density value of each dot is the same, but according to

4) The difference in color and depth of tone, the dot area is not the same. Dark shadows, large dots, printing only need to provide the same thickness of the ink layer, the amount of ink is not, copy the product color is dark; bright tone, small dot, although the ink thickness and dark tone of each dot is the same However, due to the small dot area and the low amount of ink, the color of the copied product is light, and thus the color changes in shades of light.