ClearType is a subpixel-rendering method designed to improve the perceived quality of text. The method renders text at subpixel resolution and then applies a one-dimensional symmetric mean-preserving filter to reduce color artifacts. This paper describes a computational method and experimental tests to assess user preferences for different filter parameters. The computational method uses a physical display simulation and a perceptual metric that includes a model of human spatial and chromatic sensitivity. The method predicts experimentally measured preferences for filters for a range of characters, fonts, and displays.