The ink that is used, the fountain solution, the blanket, the pressure (over/underpacking), and the speed at which the press runs all influence this type of dot gain. Each time the dots get squashed a little bit, increasing the physical diameter of the printed dot. On an offset printing press, ink is transferred from the printing plate to the blanket and from the blanket to the paper. Media such as plates or film also can be non-linear: some are but polymer plates, for instance, can have a dot gain of 5 percent of so.
Depending on the process (positive/negative), this may cause either a slight dot gain or a dot loss. In order to make sure that the media are exposed sufficiently, the laser beam is a bit wider than needed so that the lines that are exposed slightly overlap each other. The optical system in computer to plate systems or imagesetters is not always perfectly linear. Dot gain caused by imaging devices & media There are different types of dot gain in the prepress and printing process. It is also a more suitable name for processes in which some devices may not actually deliver a dot in the final output. TVI is a more generic description of the difference in tone value between a requested value and the final output. Total dot gain is the difference between the dot size on the source file and the corresponding dot size on the printed result.ĭot gain is sometimes referred to as TVI (tone value increase).
There are slight differences in dot gain between cyan, magenta, yellow, and black. If no target percentage is specified, it is assumed that dot gain is specified for a 50% tint.ĭot gain is not identical for all the colors used in color printing.The percentage, however, is not a real percentage but an absolute value – 20% dot gain at 50% does not mean the end result are halftone dots that are 60% but that the resulting halftone dots measure 70%! Please note that the convention for specifying dot gain is slightly weird: it is expressed as a percentage at a certain tint.For instance: if a page has a 50% flat tint as a background but after measuring the printed result, this flat tint is now 65%, the dot gain equals 15%. Dot gain controls in Photoshop Dot gain basicsĭot gain is expressed as a numerical value which equals the difference between the wanted value and the resulting value.
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