The Rec. 2020 specification is the color space that supports UHD resolution. It is a standard classification ITU-R recommendation BT.2020. Most modern computer and video HD displays conform to sRGB or Rec. 709. What Rec. 2020 represents is the full range of specifications under UHDTV and is not used for cinema. Rec. 2020 is ultimately designed for television so this will be for broadcast quality content and not for the movie theater. It defines mainly two resolution types 3840 × 2160 ("4K") and 7680 × 4320 ("8K") with a 16:9 aspect ratio using square pixels. It only uses progressive scan frame rates non-interlaced scanning.
The color diagram shows the wide color gamut Rec. 2020 can provide. The white point is defined in line with D65 and corresponds to about 6500 Kelvin, or average daylight. The bigger triangle is Rec. 2020 (UHDTV), while the smaller one is Rec. 709 (HDTV). When compared to other color spaces, Rec. 2020 outperforms them with a score of 75.8%. This shows it has a higher precision than Rec. 709.
Rec. 2020's color recommendations are (x/y coordinates for Red, Green, Blue):
(R) 0.708, 0.292
(G) 0.170, 0.797
(B) 0.131, 0.046
These colors are so much wider than the gamut we have now. The current technologies cannot really produce them. Most televisions today are capable of a wider color gamut than Rec. 709, but not as wide as what Rec. 2020 provides. As of 2018, there are experimental sets that attempt to reproduce the colors. This wide gamut means an excellent HDR functionality with high luminosity as well. Contrast is also critical for HDR to allow dark and bright details in the picture. Older television sets that don't support this will show details that disappear as grey or white picture areas.
When it comes to the color aspect it is the bit depth, or how many shades of each color there are, where Rec. 2020 shows its superiority. The current TV system is 8 bits per color: 256 shades, minus some margin on either end. This means that Rec. 709 is capable of a maximum of 16.78 million colors. Rec. 2020 supports 10 bit (1024 gradations) 1,073,741,824 colors or 12 bit (4096 gradations) 68,719,476,736 colors. It is amazing in theory, but in reality the human eye cannot even perceive that many colors. Rec. 2020 is an “on-the-field” color space that is meant for cameras, displays, delivery and distribution.
For high end broadcasts like 8K-UHD (Japan) the Signal Bit Rate would be 91 Mbps, MPEG-4 AAC with Center Frequency of 671 MHz. In the US UHDTV broadcast will arrive with ATSC 3.0 deployment aka NextGen TV.
