illustr. light spectrum
RGB color theory studies how light affects us human vision and comes to the additive R-G-B model. It has determined the max visual field and made thereout the well-known CIE1931 diagram.
Yes, in the year of 1931.
From this model there are 2 color spaces that normalize TV device:
Rec709 till fullHD, in 1990;
Rec2020 for UHD (4k and above), in 2012.
illustr. CIE1931_TVspaces
Sure, since TV born it didn't lack on color spaces.
But they died.
The shortest died one is NTSC, perhaps you never heard it.
Reason: no capture or display equipment can cover that much color gamut in 1953.
illustr. NTSC-1953
When we talk about color, we can describe it diagrammatic, coordinated, or in cubic till the single color coding detail appears.
Clear is, a color space/gamut needs certain "density" to support; if the construct too loose it collapses.
illustr.abc color density
That's why Rec709 still having its longevity after more than 30 years.
It is small but robust with 256-grayscale, meaning that the R-G-B primaries care and bear with 2^8 density unit respectively, or 8-bit color depth as profis jargon.
The fixed primaries guarantee that no TV should diplay its color hue differently, and the frugal 8-bit depth offers more than 16 million colors.
They are saved in YUV, not RGB which captures and beams for our eye.
illustr. YUV space
YUV is video signal construction in its analog age but adopted to the digital world because of its flexible subsampling.
The 8-bit 4:2:0 subsampling becomes a standardization required for TV bandwidth (broadcasting, receiving), therefore, treated as video "color space" - actually it's "how the signal clustered".
Amateur cameras simply use this standard for shooting and watching, kind of hobby with fun.
Film industry prepares its source material through high-tech machines.
And high-speed/bandwidth medium for subsampling/storing the signal in 4:2:2, 10-bit 4:2:2/4:4:4, Log or RAW.
No doubt, such footage for post editing has rich and precise chroma, fine and delicate luma, wide highlight with details, or complete shooting informations.
illustr. Log-curve vs Rec709-curve
In VP20b214, the 8-bit pixel format (full range) is the common mode for Rec709TV end production.
It works natively with footage compatible to Rec709/sRGB primaries.
Not compatible footage needs camera-LUT.
It can't avoid generating post artefacts, worse by amateur source and less by profi material.
But that's all.
If you do video for your daily caviar and want to go higher level, the 32-bit floating format (1.0 linear gamma) is the ultimate mode for Rec709TV end production.
It works natively with footage compatible to Rec709/sRGB primaries.
Not compatible footage needs camera-LUT and linear gamma lifting/adjusting.
It makes amateur footage not better but reduces post artefacts.
It takes all advantages of the profi material during editing. That's why commercial product is much better than ours, mostly.
It requires a powerful computer.
Its render is very slow, because the 32-bit floating to Rec709 encoding goes CPU-only-computing.
In VP20b214, the ACES/HDR10 modus (minimum luma-peak 1000Nits) is the advanced mode for HDR10 production.
It works natively with footage compatible to Rec2020 primaries, at moment it's only HDR10 and HLG.
Not compatible footage must take an IDT (Input-Device-Transforming) - which including tone curve and primaries conversion - into ACES AP0/AP1 space for editing/grading.
It requires max-power workstation and proper display equipment.
illustr. HDR10preview in Rec2020 (my screen can't show properly) and ST2084 activated (my screen does it well)
The output can be any format, because its render is actually an ODT - Output-Device-Transform.
illustr. ODT for choose
Without proper display equipment, the ACES modus is very limited.
Exempli gratia
ACES/sRGB mode can be taken for special purpose, like intermediate transforming without editing/grading; because the preview limitation prevents your judge vision for WCG footage.
Others are nonsense.
illustr. ACES/sRGB preview
Apropos, the difference between 32-bit floating project and ACES project:
Thanks for reading. I'm training my Denglish.
