Dynamic Contrast
This is a technique for expanding the contrast of LCD-screens.
LCD-screens comprise a backlight unit which is permanently emitting light and an LCD-panel in front of it which modulates transmission of light with respect to intensity and chromaticity. In order to increase the contrast of such LCD-screens the backlight can be (globally) dimmed when the image to be displayed is dark (i.e. not comprising high intensity image data) while the image data is numerically corrected and adapted to the reduced backlight intensity. In such a way the dark regions in dark images can be improved and the contrast between subsequent frames can be substantially increased. Also the contrast within one frame can be expanded intentionally depending on the histogram of the image (some sporadic highlights in an image may be cut or suppressed). There is quite some digital signal processing required for implementation of the dynamic contrast control technique in a way that is pleasing to the human visual system (e.g. no flicker effects must be induced).
The contrast within individual frames (simultaneous contrast) can be increased when the backlight can be locally dimmed. This can be achieved with backlight units that are realized with arrays of LEDs. High-dynamic-range (HDR) LCDs are using that technique in order to realize (static) contrast values in the range of CR > 100.000.
Read more about this topic: Display Contrast
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