Dynamic contrast ratio - wiki
A notable recent development in the LCD technology is the so called "dynamic contrast" (DC). When there is a need to display a dark image, the display would underpower the backlight lamp (or decrease the aperture of the projector's lens using an iris), but will proportionately amplify 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 does contain small areas of superbright light, image quality may 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), which should not be directly compared to the static contrast ratio. A plasma display with a static 5000:1 contrast ratio will show superior contrast to an LCD display with 5000:1 dynamic and 1000:1 static contrast ratio when the input signal contains full range of brightnesses from 0 to 100% simultaneously. However they will be on par when input signal ranges only from 0 to 20% brightness.
