three tests, even further inflating the calculated contrast ratio. With DLP projectors, one method to do this is to enable the clear sector of the color filter wheel for the "on" part and disable it for the "off" part This practice is rather dubious, as it will be impossible to reproduce such contrast ratios with any useful image content. Another measure is the ANSI contrast, in which the measurement is done with a checker board patterned test image where the black and white luminosity values are measured simultaneously. This is a more realistic measure of system capability, but includes the potential of including the effects of the room into the measurement, if the test is not performed in a room that is close to ideal. It is useful to note that the full on/full off method effectively measures the dynamic contrast ratio of a display, while the ANSI contrast measures the static contrast ratio. Dynamic contrast (DC) An LCD technology is dynamic contrast (DC), also called advanced contrast ratio (ACR) and various other designations. When there is a need to display a dark image, a display that supports dynamic contrast underpowers the backlight lamp (or decreases the aperture of the projector's lens using an iris), but proportionately amplifies the transmission through the LCD panel; this gives the benefit of realizing the potential static contrast ratio of the LCD panel in dark scenes when the image is watched in a dark room. The drawback is that if a dark scene contains small areas of superbright light, the resulting image will be over exposed. The trick for the display is to determine how much of the highlights may be unnoticeably blown out in a given image under the given ambient lighting conditions. Brightness, as it is most often used in marketing literature, refers to the emitted luminous intensity on screen, measured in candela per square metre (cd/m2). The higher the number, the brighter the screen. It is also common to market only the dynamic contrast ratio capability of a display (when it is better than its static contrast ratio only on paper), which should not be directly compared to the static contrast ratio. A plasma display with a 4,000,000:1 static contrast ratio will show superior contrast to an LCD (with LED or CCFL backlight) with 30,000,000:1 dynamic and 20,000:1 static contrast ratio when the input signal contains a full range of brightnesses