For four-color printing, field density is an important factor affect color copy.Field density in a certain extent determines the ink ink layer thickness, but also determines the print dot enlargement, and print order tone reproduction.In general, the level of the manuscript is relatively abundant, such as photos, and copy into print, and compression level will have a certain loss.If the field density is too small, the level of reappearance ability is low, so to improve the field density value, try to reduce the amount of compression level, thus improve the gradual reappearance ability;But if the field density value is too high, because the ink layer too thick, and the effect of printing pressure, causing network expansion is too large, also can make level from loss, especially the dark parts easy to damage layers.Therefore control the field density is vital for the whole order of replication.
However, different brand, different specifications of the printing ink, printing on different substrates, field density is different, you can achieve 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 method.
Printing contrast or K value refers to the field density and dark color density contrast (mainly refers to the density of 75% or 80%).The greater the printing contrast value, they can reproduce the layers are, the more the details of the dark color is rich;On the contrary, the smaller the printing contrast value, they can reproduce the level of the less.Its computation formula is:
Formula, Ds is field density value (including paper or less paper density), Dt is 75% or 80% density values (including paper or less paper density).
As can be seen from the formula, if a print of the Ds value as far as possible big, and Dt value as small as possible can maximize the printing contrast.
Of course, if the direct measurement of the Ds, Dt calculated again, is more tedious, so general spectral density instrument has the function of directly measuring the printing contrast. (Gold Printing Group) |
