For four-color printing, field density is an important factors affecting color copy. Field density to a certain extent, determines the ink ink film thickness, at the same time also determines the print dot enlargement, and print order tone reproduction. In general, the level of the original is relatively abundant, such as photos, and copy into print, and compression level will have a certain loss. If the density is too small, the level of reproduce ability is low, so to improve the density of field value, try to reduce the amount of compression level, thus improve the gradual reappearance ability; But if the site density value is too high, because the ink layer too thick, and the influence of the printing pressure, causing network expansion is too large, also can make level from loss, especially the dark tone level easy to loss. Therefore control the field density is vital for the whole order of replication.
However, different brand, different specifications of the ink, printing on different substrates, can achieve the field density is different, have different dot enlargement. So, in the actual production, for different substrates, inks, field density and the right to determine the best network expansion value.
Discussed here field density and dot enlargement printing contrast is used to determine the best approach.
Printing contrast or K value refers to the field density with dark color density contrast (mainly refers to the density of 75% or 80%). The greater the printing contrast value, it can represent the level of it, the more the details of dark color is rich; On the contrary, the smaller the printing contrast value, it can represent the level of the less. Its computation formula is:
Formula, Ds for field density values (contain can be paper or less paper density), Dt is 75% or 80% density values (contain can be paper or minus paper density).
As can be seen from the formula, as much as possible if a print of the Ds value is big, and Dt value as small as possible so that it can maximize the printing contrast.
And, of course, if direct measurement of the Ds, Dt calculated again, is more tedious, so general spectral density apparatus has the function of directly measuring the printing contrast. (Gold Printing Group)