Dot gain refers to a characteristic of halftone printing whereby reflectance of the printed material is less than would be expected from the percentage area coverage of the dots set on film by the imagesetter, or the percentage area coverage expected from a digital code value in the digital representation of the image.
The major component of dot gain is Optical Dot Gain, by which light scatters in the printing substrate. Dot gain may also be contributed by dot spreading, press gain, slurring, or doubling.)
Dot gain is also called “tone value increase” (TVI). The term TVI is confusing because in domains other than printing – for example, in color science – value is zero at black, and increases towards white; what a printer calls “tone value increase” would be called, by a color scientist, “tone value decrease”!
Dot gain is dependent upon many factors associated with the ink, the press, and the substrate being printed.