Video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) sy ...

black level is defined as the level of brightness at the darkest (black) part of a visual image or the level of

brightness Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. The perception is not linear to luminance, ...

at which no light is emitted from a screen, resulting in a pure black screen. Video displays generally need to be calibrated so that the displayed black is true to the black information in the

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) sy ...

signal. If the black level is not correctly adjusted, visual information in a video signal could be displayed as black, or black information could be displayed as above black information (gray). The voltage of the black level varies across different television standards.

PAL Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

sets the black level the same as the blanking level, while

NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...

sets the black level approximately 54 mV above the

blanking level In video technology, blanking level is the level of the composite video signal during the front and back porches of the video signal. The composite video signal is actually the video information superimposed on blanking. The total level of the co ...

. User misadjustment of black level on monitors is common. It results in darker colors having their hue changed, it affects contrast, and in many cases causes some of the image detail to be lost. Black level is set by displaying a testcard image and adjusting display controls. With CRT displays: * "brightness" adjusts black level * "contrast" adjusts white level * CRTs tend to have some interdependence of controls, so a control sometimes needs adjustment more than once. In

digital video Digital video is an electronic representation of moving visual images (video) in the form of encoded digital data Digital data, in information theory and information systems, is information represented as a string of discrete symbols eac ...

black level usually means the range of

RGB The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three addi ...

values in video signal, which can be either ..255(or "normal"; typical of a computer output) or 6..235(or "low"; standard for video).

See also