Halftone Color: Diffusion of Light and Dot Shape

The diffusion of light within paper has a significant affect on the color of a halftone printed image. This effect, known as optical dot gain, or the Yule-Nielsen effect, depends on the shape and size of the halftone dots, on the locations of dots with respect to each other, as well as upon the degree of light diffusion within the paper. The current work reports on a theoretical investigation of the influence that the shape of the halftone dot has on optical dot gain. A comparison is made between the colors produced by two types of halftone screens – a circular dot halftone screen and a line halftone screen. These are also compared to the colors produced when there is no diffusion of light within the paper. The comparisons are made for a monochromatic (one ink) halftone print, and for a bichromatic (two inks) halftone print. It is shown that there is a slight difference in halftone color between the circular dots and the lines, but that this difference is much less than the case of no diffusion.