Observations on ACES 2 candidates version 024, 025, 026, 026b
DaVinci Resolve 18.1.1
Using B: Stock DaVinci YRGB project with manual ACES node
Computer 1 - HDR
AMD Threadripper 1950X, Radeon Pro WX8200 GPU, Windows10 64-bit with display LG OLED55C8PCA via BMD DeckLink 4K Extreme 12G
Computer 2 - SDR
Intel Xenon E5-2650, FirePro W8100 GPU, Windows10 64-bit with ASUS ProArt Monitor calibrated to Rec.709 via Decklink Mini Monitor 4K
HDR Comparisons using:
rev 024 Rec2100
rev 026 Rec2100 (P3D65 1000nit limit)
rev 025 Rec2100
rev 026b Rec2100 (P3D65 1000nit limit)
rev 024 Rec2100 (Rec709 sim)
rev 026 Rec2100 (Rec709 sim)
SDR Comparisons using:
rev 024 Rec709
rev 026 Rec709
rev 025 Rec709
rev 026b Rec709
Rec709 (ACES1.3)
ISSUE 1:
For HDR I did not like the images with the suggested Resolve settings so I modified as follows:
Enabled Dolby Vision
ver 4.0
1000-nit, P3, D65, ST.2084, Full
Target Display Output at 600-nit, P3, D65, ST.2084, Full(HOME)
Analyzed all the images
Enabled Tone Mapping Preview
This gave a much better looking image.
The Rec709_sim versions looked to dark and were difficult to lighten.
ISSUE 2:
It felt as if 24 and 26 were nicer than 25 and 26b due to some hues being brighter in 25 and 26b.
I suspect that not only does the variation in the amount of brightness vary by hue, but also by saturation with higher saturation being brightened more.
To investigate this further I added nodes before and after the ODT node in which I used the RGB mixer to select monochrome.
These nodes were controlled by a three node binary switch. (Color Generator set Black, Invert, Invert with outputs of the Inverts to the mask inputs of the before and after B&W nodes.)
All the comparisons listed above were checked with the before B&W node which showed identical results, as was expected.
Then comparisons were made with B&W before and after for each listed and then between each other with the after B&W nodes on.
The variations are readily apparent using frame 0074.
All the after node B&W images varied with none even close to that of the ACES1.3 Rec709.
But, to some degree, this was to be expected as the apparent luminosity is going to vary from the actual luminosity. But I did use the RGB mixer for that reason.
But which is closest to reality, or actually apparent reality?
ISSUE 3:
The saturation of Yellow seemed a bit less than the other colors, especially when looking at the various charts in the sample images.
This was most apparent in SDR and very little to not in HDR.
ISSUE 4:
There is a difference of HDR and SDR as to changes in saturation values for various revisions.
In SDR the saturation, in general, reduces from 024 to 026 and from 025 to 026b.
In HDR the saturation, in general, reduces from 026 to 024 and from 026b to 025, the reverse of the SDR.
(as seen in the vector scopes)
ISSUE 5:
This issue is difficult because of comparing between two monitors and systems.
This issue involves darker skin.
I took into account variations seen in frame 0067 (Isabela) between HDR and SDR which were a close match.
The lighter skins in other frames looked to be a good relative match.
The darker skins looked to be a good brown color in HDR, but in SDR seemed to have a reddish hue.
(example frames 0005, 0073, 0074)
As a check on this I compared rev_024_Rec2100 with rev_024_Rec2100_(Rec709sim) on the HDR system as well as rev_026_Rec2100_ (P3D65 1000nit limit) with rev_026_Rec2100_(Rec709sim) and found similar results in that the Rec709sim had the more reddish hue in dark skin. Also in HDR, rev_0024 and rev_0026 differed in that the rev_026 HDR shows some reddishness but far less than SDR. In SDR all revisions showed the same amount of reddishness. (Note also that the Rec709sim versions had lower exposure which could have influenced color.)
ISSUE 6:
While the SDR images look to be an improvement over ACES1.3, I feel something not right with the HDR.
If I had to pick one thing I would say contrast of the lighting looks harsh, which is just the opposite of what HDR should provide.
Something is just not working as the SDR images look better. (image 0029 is one example of many)
And again I also checked this with the Rec709sim revisions all on HDR computer 1.
QUESTION:
Since there seems to be issues with perceptual luminance values for various hues and saturation, could a color model like OKlab help? or has this already been considered?
I have used this model successfully to get nice control of hue and saturation and perceived lightness.
Also note how OKlab handles the presentation of gradients.
COMMENTS:
I find the other work being done using the gradients interesting.
I don’t see SDR and HDR as working together yet with these revisions and intend to try more HDR grading.