Dot gain

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Dot gain is a phenomenon in printing and graphic arts whereby printed dots are perceived and actually printed bigger than intended. This causes a darkening of the screened images or textures, especially in the mid tones and shadows.

This happens because of the viscosity of ink and its ability to spread through the paper as it is soaked in. Dot gain varies with paper type. Uncoated paper stock like newsprint paper shows the most dot gain.

A related subject, the Yule-Nielsen effect, is sometimes called "optical dot gain." When using a conventional reflection densitometer to measure dot area, and applying the Murray-Davies model, the computed size of the dot will be smaller than it actually is. This isn't dot gain at all, but an error in the computation method.

The area of the dot may be computed more accurately using the Yule-Nielsen model. This requires the optical densities of the substrate, the solid-covered area, and the halftone tint, as well as the value of the Yule-Nielsen parameter, n. Pearson [TAGA Proceedings, 1981] has suggested a value of 1.7 be used in absence of more specific information.