An empirical model has been developed to describe tone reproduction in halftone imaging. The model is based on experimental measurements of the image microstructure of halftone gray scales produced by offset lithography, thermal transfer, ink jet, and silver halide photography. Both traditional and stochastic halftone patterns are described by the model. Like the Yule-Nielsen model, which contains an arbitrary constant called the "Yule n factor", the model developed in the current study is derived from the Murray-Davies equation. However, the current model contains two empirical parameters, w and v. The w factor relates to the optical spread function of the paper relative to the spatial frequency of the halftone dots. The v factor relates to the distribution of colorant within the dot. The Yule-Nielsen model describes only the relationship between the mean reflectance, R, of the halftone image and the dot area fraction, Fi. The current model describes R versus Fi and also some experimental data on the image microstructure. With the Yule-Nielsen model, estimates of the n factor are traditionally made by fitting the model to R versus Fi data. With the current model, estimates of w and v are chosen to fit the image microstructure data. The resulting values of w and v provide an excellent fit with the mean reflectance, R, versus Fi data.
Department, Program, or Center
Chester F. Carlson Center for Imaging Science (COS)
Recent Progress in Digital Halftoning II (1999) 390-396
RIT – Main Campus