Re: [DCP-o-matic] P3 Color Space

On Tue, 21 Apr 2015 14:22:31 +0200 Carsten Kurz via DCPomatic <dcpomatic(a)carlh.net> wrote: [snip] Here are Dennis' thoughts on P3: Hi Carl, P3 color space is an RGB space covered by most DCP projectors. (The "post production" Barco DP2KP actually covers a color gamut quite a bit larger than P3. As ever, the technology is in flux.) Carsten Kurz is right that editors and colorists should take advantage of the expected display of their work: P3. Curiously, the term "P3" does not appear in the SMPTE or DCI standards. I attach the 2011 SMPTE RP 431-2. Perhaps the term "P3" is Adobe's or Black Magic's, and I prefer we stick as close as we can to the SMPTE version of DCP projection. I will use the term "P3" but only with SMPTE legitimated interpretation. DCP-o-matic can already handle source footage in P3 space. When you give DCP-o-matic an RGB video you can specify the RGB-to-XYZ matrix. SMPTE RP 431-2 gives the R,G,B primary chromaticities: Red 0.680, 0.320 Green 0.265, 0.690 Blue 0.150, 0.060 Although a little indirectly, SMPTE RP 431-2 gives the same white point as in the original DCI specification: White 0.314, 0.351 DCP-o-matic is now able to generate a RGB-to-XYZ matrix from those four chromaticities. 0.4451698 0.2771344 0.1722827 R X 0.2094917 0.7215953 0.0689131 × G = Y 0 0.0470606 0.9073554 B Z Happily, this the same matrix given in SMPTE RP 431-2, page 12. SMPTE RP 431-2 also tells you to understand the R'G'B' in a P3 encoded video to require gamma 2.6 to become RGB. The DCP created by DCP-o-matic will be encoded X'Y'Z' as every DCP must be. But if the source material was R'G'B' of the P3 kind described above, then the X'Y'Z' will be limited so as to only project XYZ that are producible by the P3 primaries (in positive amounts). Thus what's on the screen will match what the P3 editor or colorist saw. Dennis