Introduction of Correction Terms for Optical Dot Gain into Pollak's Equation based on Spectral Reflectance

Abstract

One of the main causes of the difference between color photography and printing based on color image reproduction by superimposing C, M, Y and BK halftone dots on paper is the optical dot gain arising from light diffusion through paper substrate. Neugebauer's equation is famous for describing the color print based on halftone dots, but it is very complicated. By assuming additivity of solid optical densities Neugebauer's equation can be resolved into factors and can be transformed into Pollak's equation. By introducing our correction terms for optical dot gain into Pollak's equation through our own method, color reproduction superimposing four color halftone dots is described satisfactorily in the form of spectral reflectance. Our correction terms are quadratic equations of dot area and they have coefficient k_λ's.