The use of color electrophotographic (EP) laser printing systems is growing because of their declining cost. Thus, the print quality of color EP laser printers has become increasingly important. Since text and lines are indispensable to print quality, many studies have proposed methods for measuring these print quality attributes. Toner scatter caused by toner overdevelopment in color EP laser printers can significantly impact print quality. A conventional approach to reduce toner overdevelopment is to restrict the color gamut of printers. However, this can result in undesired color shifts and the introduction of halftone texture. Coring, defined as a process where the colorant level is reduced in the interior of text or characters, is a remedy for these shortcomings. The desired amount of reduction for coring depends on line width and overall nominal colorant level. In previous work, these amounts were chosen on the basis of data on the perception of edge blur obtained from softcopy simulation of the blurring. We describe psychophysical studies to directly establish optimal coring values as a function of line width and nominal colorant level. For each line width and nominal colorant level, this is done by asking human subjects to choose the minimum amount of coring that is necessary to eliminate the perception of toner scatter. We conduct four separate psychophysical studies to address different aspects of this question.


Hyung Jun Park, Jan P. Allebach, and Zygmunt Pizlo, "Psychophysical Investigation of the Effect of Coring on Perceived Toner Scatter," Journal of Electronic Imaging, 19(01), 011008, (2010).

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