In reference to computer monitors, the measurement of the difference in light intensity between the brightest white and the darkest black. Contrast ratio is often used in marketing computer monitors, where a high contrast ratio, such as 400:1, represents a better color representation (the better the information will appear against a darker background) on the monitor than a lower contrast ratio, such as 150:1.
The term is used more frequently in reference to LCD monitors than CRT monitors.
A standard for measuring light output, used for comparing projectors. Unfortunately, there are enough variables, that the eye will often disagree radically with the ANSI rating. At best, ANSI lumens do fairly well comparing "apples" to "apples". If however one projector uses Halogen lamps and another metal-halide, the halogen projector will seem noticeably dimmer even if the two units rate the same