Lightness and Contrast Requirements for Legibility of Reflective Liquid Crystal Displays.

The purpose of this study is to investigate the required lightness and contrast for legibility of reflective liquid crystal displays (LCDs). Thirty subjects rated 65 lightness and contrast combinations displayed on the hard copy that simulate a reflective LCD, under various ambient illuminance conditions The results indicate that a higher contrast ratio is required as the lightness L * of the background is decreased lower than 65 or 70 (i e reflectance is 35-40%). The required contrast ratio is about 5 when the lightness is higher than 65 or 70. The influence of ambient illuminance on subjective legibility of the simulated reflective LCDs is not so obvious when the lightness of the background is higher than 65 or 70 These results suggest that the lightness of the background should be higher than 65 or 70, and the contrast ratio between the characters and background should be at least 5.