One of the sampling frequency ratios used to digitize the luminance and color difference components (Y, B-Y, R-Y) or, more usually, the RGB components of a video signal. It supports an equal number of samples for each of three components or as RGB 4:4:4. It is commonly used in standard computer platform-based equipment, and for the highest quality results in high-end post production as well as in the production of movies.
For movies, the images are kept in the RGB form all the way through the DI process to create the Digital Source Master (DSM) that can be used to produce a Digital Cinema Distribution Master (DCDM). For distribution the DCI recommends the use of X´Y´Z´ chromaticity which can be derived from RGB using a 3D LUT.

See also: 2K, 4K, DCI, Digital intermediate, Dual link, LUT, X´Y´Z´