Chroma
In video technology, chrominance or colourfulness describes a signal with information about the type of color . It is transmitted in parallel with the luminance (the brightness signal , for reasons of compatibility often corresponds to the pure black and white image). Both together provide the complete information about the colored image in the context of a brightness-chromaticity model .
In contrast to this, there are color models that specify a color location using three basic colors , such as the RGB color space .
Since the color space perceived by humans based on their physiology can be spanned over a surface, the transmission or storage of color information that is complete for the human observer must take place with at least two independent chrominance signals. This colored area is shown as an example for the YUV color model in the illustration opposite .
The definition of only two chrominance signals for the complete mapping of the color information is not fundamentally given, but rather is determined by the special structure of the human eye. For living beings with a different color perception, such as marsupials or honey bees , additional chrominance signals would have to be added. Higher-dimensional color spaces then result. On the other hand, a television set for dogs and most other higher mammals could do with a single chrominance signal.
The two color signals required for human viewers play a role in both analog and digital color television , video transmission , color photography and the color models used. In all these cases, Y denotes the brightness signal , the following two capital letters such as C b C r denote the chrominance signals. These are formed differently depending on the application, from which the various names result:
| Color model | Application: analog / digital | Application: norms and standards, devices |
|---|---|---|
| YCbCr | digital | Image / video transmission according to MPEG and JPEG , DVD , digital PAL and NTSC , DVB |
| YPbPr | analogous | Component video signal ( video recorder , game consoles , flat screens ) |
| YUV | analogous | Television standards PAL and NTSC (today); Composite video , S-video |
| YDbDr | analogous | TV standard SECAM |
| YIQ | analogous | NTSC (earlier) |
See also
- Color difference, see Delta E.