As applied to analog television signals, two different words are used, luminance and luma, meaning two different things. Luma is a new word proposed by the NTSC in 1953 to prevent confusion between the Y' component of a color signal and the traditional meaning of luminance. While luminance is the weighted sum of the linear RGB components of a color video signal, proportional to intensity, luma is the weighted sum of the non linear R'G'B' components after gamma correction has been applied, and thus is not the same as either intensity or luminance. Analog television encodes picture information by varying the voltages and/or frequency of the signal. ... NTSC is the analog television system in use in Japan, United States and certain other places, mostly in the Americas (see map). ... 1953 (MCMLIII) is a common year starting on Thursday. ... A weight function is a mathematical device used when performing a sum, integral, or average in order to give some elements more of a weight than others. ... The word linear comes from the Latin word linearis, which means created by lines. ... The RGB color model utilizes the additive model in which red, green, and blue light are combined in various ways to create other colors. ... A gamma characteristic is a power-law relationship that approximates the relationship between the encoded luminance in a television system and the actual desired image brightness. ...

An incorrect luma setting can cause visible flicker in a television display.

For standard-definition television systems using older phosphor characteristics modeling for the RGB primaries, (non-linear) luma can be calculated from gamma-adjusted RGB using the CCIR 601 formula Y' = 0.299 R' + 0.587 G' + 0.114 B'. Modern HDTV systems use a different definition of RGB phosphor characteristics and the ITU-R BT.709 formula Y' = 0.2126 R' + 0.7152 G' + 0.0722 B'. In both formulas, scaling and offsets used on both sides of the equation are assumed to be the same (e.g., ranging from 16 for black to 235 for white when used for digital video such as CCIR 601). Otherwise, some adjustments to the formula are needed to account for different scaling and offsets. Standard-definition television or SDTV refers to television systems that have a lower resolution than HDTV systems. ... CCIR 601 is the old name of a standard published by the CCIR (now ITU-R) for encoding interlaced analogue video signals in digital form. ... It has been suggested that High Definition Video be merged into this article or section. ... The ITU Radiocommunication Sector (ITU-R) is a standards body subcommittee of the International Telecommunication Union (ITU) relating to radio communication. ... Digital video is a type of video recording system that works by using a digital, rather than analog, representation of the video signal. ... CCIR 601 is the old name of a standard published by the CCIR (now ITU-R) for encoding interlaced analogue video signals in digital form. ...

See also

• chrominance
• gamma correction