Estimating Physical Dot Gain of Offset Using a Scanner

The methodology for estimating physical dot gain from scanned images is proposed, taking into consideration of light scattering inside the paper substrate and the light reflection at airpaper and air-ink interfaces. The physical dot gain obtained reveals significant differences in the light tones compared to the middle and the dark tones. This indicates different mechanism governing the physical dot gain of the light tones (well isolated dots) compared with that of the middle and the dark tones comprising overlapping dots.