ClearType sub-pixel text rendering: Preference, legibility and reading performance

ClearType is an onscreen text rendering technology in which the red, green, and blue sub-pixels are separately addressed to increase text legibility. However, it results in colored borders on characters that can be bothersome. This paper describes five experiments measuring subject preference, text legibility, reading performance, and discomfort symptoms for five implementation levels of ClearType rendered text. The results show that, while ClearType rendering does not improve text legibility, reading speed or comfort compared to perceptually-tuned grayscale rendering, subjects prefer text with moderate ClearType rendering to text with grayscale or higher-level ClearType contrast. Reasons for subject preference and for lack of performance improvement are discussed.