Ghosting is when image elements overlap onto subsequent
image areas in the direction of print (fig. 2.1-17b).
The inking rollers are generally smaller than the plate
cylinder in a roller inking unit. After inking the plate, an
ink profile remains on the inking roller due to the ink
splitting and can appear in the print image as a “ghost
image” after one roller revolution. Several ink form
rollers of various diameters (on sheet-fed offset printing
presses normally four form rollers) and a correspondingly
dimensioned inking unit regarding the
number of rollers and the points of contact as well as
the effect of the lateral distribution, usually ensure that
the ink film is smoothed out sufficiently on the printing
plate. However, with an unfavorable color combination
on the printing plate with regard to the geometry
of the inking unit, visible ghosting effects can occur.