Brightness is a measure of the light output emitted by a screen. If the light output is high, the viewer perceives the image as bright; if it is low, he perceives it as dark. Brightness is evaluated using the unit of measurement candela/m2. A brightness that is perceived as pleasant has about 200 candela/m2.
Brightness, along with hue and color contrast, is decisive for the recognition of image details. Depending on the color range, the human eye can distinguish between 16 and 26 different brightness values, whereby the perception of brightness is logarithmic. Darker brightness values therefore require only a fraction of the actual intensity. Thus, a 50% gray value can be produced with only about 20% of the intensity that would be needed for the white value, i.e. the 100% value.