CAMERA



Colour Space Rec.2020

The Rec.2020 color space is used for standardization in UHD television.

Broadcast systems and transmission providers deliver video that corresponds to a pre-defined colour space. This means it complies to a set of rules about what colour parameters it meets, and how it will be displayed on monitors and the audience's television sets. The colour model can differ between what was recorded during production, to what the audience finally see at home.

Colour Space

A colour space is a system referring to the mathematical description of colour against a set colour system. There are a number of colour systems: RGB, CMYK, YUV, HSL, and the colour space describes which colours can be used. The extreme values or vertices of these coordinate systems are determined by the so-called primary colours. In an RGB colour model, the primary colours are red, green and blue. This is the colour palette that you can work with for your picture.

Gamut

A colour gamut describes the amount or range of any displayable colour within the gamut colours. So in real terms this means that the colour gamut of the REC.2020 colour space, contains colours that do not exist in the gamut of the Rec709 HDTV colour space (because it is smaller than REC.2020). How big a colour space, and, consequently, how many colours are contained in the gamut, depends on the physical capabilities of the monitor or the camera.  The term wide colour gamut is used to refer to a higher number of colours than Rec.709.

Rec.2020

UHD TV was introduced by the ITU in 2012 with the publication of the ITU-R BT.2020 standard to interpret the specifications for UHD 1 (4K) and UHD 2 (8K). The Rec.2020 colour space is also included in this standardisation. As with Rec.709 , this is an RGB colour space. It has a larger colour gamut than any other colour space in the area of defined RGB colour spaces. Currently, you can only reproduce the primary colours of Rec.2020 to 100% with laser light sources. In 2015 NHK introduced a laser-LCD display prototype with a measured performance of 98%. The gamut of Rec.2020 is equivalent to slightly more than half of the visible spectrum, so is a huge leap in reproducing real-world colours on your screen at home. Of course, you’ll need a new TV to appreciate it.

ITU-R BT.2020 defined the following colour space:

  • A resolution for UHD 1 of ("4K") 3840x2160 and UHD 2 of ("8K") 7680x4320 pixels, with an aspect ratio of 16:9 and square pixels
  • Specified frame rates: 120p, 119.88p, 100p, 60p, 59.94p, 50p, 30p, 29.97p, 25p, 24p, 23.976p.
  • Only progressive scan allowed. Field or PsF methods are not allowed.
  • 10-bit or 12-bit RGB and component signal formats with 4:4:4, 4:2:2 and 4:2:0 colour sub-sampling
    in 10-bit black level at 64 and white level at 940
    in 12-bit black level at 256 and white level at 3760
  • White point (illuminant) D65 corresponds to a colour temperature of 6500K



Rec.709 vs. Rec.2020