The minimum color gamut in standard digital cinema is DCI-P3. However, wider color gamuts than DCI-P3 are now possible. To better understand how wider color gamuts affect perception, several CIE chromaticity diagrams are shown below, beginning with Pointer’s Gamut.
Michael R. Pointer published in 1980 a maximum gamut for real surface colors, based on 4089 samples, establishing a widely respected target for color reproduction. Visually, Pointers Gamut represents the colors we see about us in the natural world. Colors outside Pointers Gamut include those that do not occur naturally, such as neon lights and computer-generated colors possible in animation. Pointers Gamut is illustrated below.
Figure P-1. Pointers Gamut
HDTV and Rec. 709
Rec. 709 is the ITU Recommendation for HDTV. Included in the Recommendation is the HDTV color space, also known as “Rec. 709.” The Rec. 709 color space is compared with Pointers Gamut, below. As can be seen, the Rec. 709 color space is significantly smaller than Pointers Gamut, which is why it was deemed unsuitable for digital cinema.
Figure P-2. Rec. 709 Color Space Compared With Pointers Gamut
DCI-P3 is explained above as the minimum color gamut in digital cinema for projectors and displays. Below, DCI-P3 is compared with Pointer’s Gamut. As you can see, DCI-P3 covers most of Pointers Gamut.
DCI-P3 compared with Pointers Gamut
UHDTV and Rec 2020
Rec. 2020 is the ITU Recommendation for UHDTV. Included in the Recommendation is the UHDTV container color space, commonly known as “Rec. 2020,” designed to include Pointers Gamut. However, emphasis must be placed on the word “container,” as practical displays cannot implement Rec. 2020. The actual implementation of Rec. 2020 in a display requires nanometer-wide primaries, which would create metameric problems and speckle. (Metameric problems include the lack of color agreement among multiple viewers.) Note that the ITU has not recommended a minimum UHDTV display gamut to guide manufacturers and artists.
The illustration below is of Rec.2020 compared with Pointers Gamut and DCI-P3. Note that if a wider color gamut than DCI-P3 were to emerge in cinemas, the primary benefit would be improvement in the cyan range. Deeper cyans will deliver more vivid color in ocean shots, for example.
Figure P-3. Rec. 2020 (light grey) compared with Pointers Gamut and DCI-P3