Light scattering, or the so-called Yule-Nielsen effect, and ink penetration into the substrate paper play important roles in tone reproduction. We develop a framework in which the influences of both of these effects on the reflectance and tristimulus values of a halftone sample are investigated. The properties of the paper and the ink and their bilateral interaction can be parameterized by the reflectance R-p(0) of the substrate paper, the transmittance T-i of the ink layer, the parameter gamma describing the ink penetration, and (p) over bar describing the Yule-Nielsen effect. We derive explicit expressions that relate the reflectance of the ink dots (R-i), the paper (R-p) and the halftone image (R) as functions of these parameters, We also describe the optical dot gain as a function of these parameters. We further demonstrate that ink penetration leads to a decrease in optical dot gain and that scattering in the paper results in the printed image's being viewed as more saturated in color. (C) 2001 Optical Society of America. OCIS codes: 100.7810, 290.7050.