Picture quality and readability of thirteen LCDs for mobile telephones were subjectively assessed by thirty subjects under indoor and outdoor lighting conditions. The luminance, contrast, color gamut, and character and pixel sizes of the LCDs were measured under both lighting conditions. From these results, we investigated the requirements for mobile LCDs in terms of picture quality and readability. Results indicate that the optimum luminance level under a screen illuminance of 200 lx is 50 cd/m2, and that the level is 160cd/m2 under a screen illuminance of 10, 000 lx. The optimum character size is 3.14 mm heigh, and the optimum stroke width is 0.26 mm.
