The contrast ratio is a measurement of a display’s contrast capability, and is defined as the ratio of the luminance of the brightest color (white) to that of the darkest color (black) that the system is capable of producing. A high contrast ratio is desired in any display. Unfortunately, due to the various methods of measurement employed, as well as variations in operation and unstated variables, the contrast ratio ratings provided by different manufacturers of display devices are not necessarily comparable to each other, and remarkably different measured values can sometimes produce similar results. Manufacturers traditionally favor measurement methods that isolate the device from the system environment, since that is a factor not under their control. Consequently their measurement methods simulate an ideal room where the only light seen in the room would come from the display device. With such an ideal room, the contrast ratio of the image would be the same as the device. Real rooms, however, reflect some of the light back to the displayed image, lowering the contrast ratio seen in the image, so display users must generally take the brightness characteristics of the surroundings into account when designing their systems. Complicating factors somewhat, the ratio of the luminosity of the brightest and the darkest color the monitor is capable of producing simultaneously at any instant of time is called static contrast ratio, while the ratio of the luminosity of the brightest and the darkest color the display is capable of producing over time is called dynamic contrast ratio.