Luminance (relative)

The luminance is a photometric size of the video, which is used as a measure of the brightness of pixels. Physically it is identical to the luminance of the unit cd / m². The term " luminance " but connotes the specific context of video art and is reckoned that usually in units of the maximum luminance. In addition, it is at the luminance to a transmitted signal, which ignores the directional dependence of the luminance, and only then is proportional to the luminance when the screen is optimally calibrated.

The English term luminance is available for both luminance and for luminance, which can lead to translation errors.

Both analogue and in digital image data, the terms luminance and luma are used. The word " Luma " was introduced in 1953 by the NTSC. Luma roughly corresponds to the brightness ( brightness ), is in the video section but often mistakenly referred to as luminance.

The luminance signal E'Y calculated from the equalized nonlinear color value signals E'R, E'G, E'B as follows:

Luma ( Y component in YUV and in YCbCr) is a weighted sum of the non-linear RGB components (ie signals R'G'B ' ) after a gamma correction has been applied. Weighting in digital PAL and NTSC systems (YCbCr according to CCIR 601) in HDTV systems (e.g., ITU-R BT.709 ) and other JPEG - or MPEG -based digital image and video systems (for as a DVD -Video):

Flickering of image sequences can be caused by incorrect luminance and Lumaeinstellung or translation.

In a digital 8- bit encoding, there are 28 = 256 different gray levels, ie black, white and in between 254 shades of gray.