An aspect of Dot Gain associated with physical increase in the area coverage of a halftone dot when printed, compared to the area of the dot on the imagesetter film. (See also optical dot gain.)
In offset lithography, the printed image may take a tone or color darker than expected owing to increased pressure between the blanket cylinder and impression cylinder of an offset press, or in other processes by ink feathering or spreading as it penetrates the surface of the substrate. The paper may have a high porosity, or the ink a low viscosity. Some types of offset printing plates, in particular bimetal plates and positive-working plates, exhibit less dot gain than others.