Abstract
To compare dot gain of various hardcopies, we have proposed a new dot gain definition as “Dot area expansion caused by dot thickness reduction compared with the one at the solid area”. According to this definition, the amount of dot gain can be estimated both from cross sectional dot structures and by colorimetric measurement. The latter is preferred as for evaluation efficiency. The present report describes in detail the principle of colorimetric dot gain analysis based on the new definition and further proposes practically effective procedures. The amount of dot gain is evaluated by the degree of deviation from the straight line representing the Murray-Davies relationship on a color coordinate plane. Such a deviation takes place with the change of the ratio of main absorption to sub-absorption of the colorant caused by the dot thickness reduction. Accordingly, in the case of a step wedge comprising a typical magenta pigment which has the main absorption at the y region accompanied with a relatively large sub-absorption at the z region, a colorimetric analysis on the y-z plane is most desirable. Slight differences in dot gain depending on screen structure have become detectable due to the appropriate selection of plane.
