The highest resolution supported by the Optoma EX855 is 1920 x 1200 (WUXGA). That's over seven times the resolution of the most common supported graphics resolutions of 640 x 480 (VGA). In addition, this multimedia projector support supported graphics resolutionss of 1024 x 768 (XGA), 1280 x 1024 (SXGA), 1280 x 720 (HD 720), 1280 x 768 (WXGA), 1400 x 1050 (SXGA+) and 1600 x 1200 (UXGA) and 800 x 600 (SVGA).
A 1920 x 1200 (WUXGA) supported graphics resolutions is in fact the best supported resolution across all multimedia projectors of a comparable spec and age to the EX855.
A 640 x 480 (VGA) supported graphics resolutions is the worst supported resolution amongst comparable types of projector.