HDR10 grade: Retaining color & detail in the sky area

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Piotr Wozniacki

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HDR10 grade: Retaining color & detail in the sky area

PostTue Oct 10, 2017 8:20 am

Hello guys; haven't been posting on this forum for a long time (meaning I haven't had too many problems with transition to v.14 :). But I do have a serious workflow problem (same in the 12.5 and 14) that I'd need your help with... So here I go:

As some of you may remember, ever since I started using Resolve over a year ago, I have been grading my FS7's XAVC-I, Shogun Inferno's DNxHR and recently also GH5's H.264 footage for PQ, using RCM and sometimes ACEScc. I'd say almost all my footage is log (S-Log2/3 from Sony and V-Log L from the little Panasonic), always 10-bit 4:2:2 - nothing less than that is enough for successful HDR10 grading! But I've started to observe some problems with my highlights, and particularly the sky area (clear blue, or overcast with white or gray clouds - in the outdoor uncontrolled lighting these are usually the brightest part of the picture). Namely, it's very difficult for me to retain color and detail information in the sky area; I must keep the level down to see the blue sky color and details in the clouds, because all this will quickly and suddenly turn into ugly, gray area with no color or detail at all... My Samsung SUHD monitor is rated over 1,000 nits of maximum brightness, and yet - with some footage, particularly S-Log3 - it can happen at levels quite a bit lower than this....

So far, my testing indicate one of the following might be the culprit (both software and/or hardware):

a. the way highlights in Log footage are decoded in Resolve (be it RCM, ACEScc, or even LUT-based workflows such as Loagrist - not much can be done about it, but do you encounter the same behavior?)

b. my Decklink 12G video card: colors in highlights are turning into light grey areas easily and suddenly, even when the levels not too high at all (BMD Support - if you're reading this - do you think my card might be malfunctioning?)

c. my Samsung SUHD TV, used as a grading monitor: it's said to have maximum brightness of more than 1,000 nits but when highlights occupy to large an area, it turns light grey without details but with lots of compression artifacts (yeah I know - calibrating should be repeated - but could the difficulty with retaining highlight detail & color indicate some hardware problem in my TV?)

Before you guys point at tone of the above as the most probable reason, let me show you the only way I can alleviate the problem with Resolve grading controls:
Highlights and Shadows.JPG
Highlights and Shadows.JPG (11.58 KiB) Viewed 322 times

As you can see, the "Highlight" control must be turned down considerably to protect sky color & details; it doesn't seem to decrease Gain too much (so the overall brightness is not overly reduced), while preventing the abovementioned turning of highlights into one detail- and color-less area. BTW, in this particular example I also elevated the Shadows - but that's because the scene has been back-lit considerably. As can be seen in the screen grab below, the clouds' color and detail has been retained - while the scopes still reach 1,000 nits with their peaks:
Parade.JPG
Parade.JPG (41.01 KiB) Viewed 322 times

And the resulting grade (in its basic stage, ready for fine-tuning) is OK in that the sky is not overblown into detail-less gray while the shadows are not too dark, with details but not noisy:
SDR screen grab from HDR project.jpg
SDR screen grab from HDR project.jpg (440.87 KiB) Viewed 322 times


I need to add that this kind of problem with retaining (otherwise completely legal in HDR10) highlights' detail & color has been increasing lately; this would indicate hardware rather than software problem... Also, in your grading experience much deeper than my own, is a need for such intensive tuning of Shadows and Highlights considered normal - or very rare at all? Your answer to this question would help me tremendously, as at beginning of my using Resolve on this particular hardware I never even touched those controls, whereas dialing the Highlights down has become more and more necessary lately... Looking forward to your suggestions and opinions,

Piotr
Last edited by Piotr Wozniacki on Tue Oct 10, 2017 10:15 am, edited 1 time in total.
Grading system: DaVinci Resolve Studio; Asus X-99 Pro/USB3.1; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; 480 GB SSD system drive; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive; Decklink 4K Extreme 12G driving Samsung SUHD calibrated monitor
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Piotr Wozniacki

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Re: HDR10 grade: Retaining color & detail in the sky area

PostTue Oct 10, 2017 8:34 am

It's important to add that it's not just such dark and backlit scenes that require turning Highlights control down; in order to retain blue color of the sky in the scene below, I had to crank the Highlights down all the way to -72; this cannot be normal IMHO. What do the experts think - is my Decklink or TV going?
SDR blue sky from HDR project.jpg
SDR blue sky from HDR project.jpg (536.05 KiB) Viewed 226 times
Grading system: DaVinci Resolve Studio; Asus X-99 Pro/USB3.1; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; 480 GB SSD system drive; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive; Decklink 4K Extreme 12G driving Samsung SUHD calibrated monitor
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Daniel Bănică

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Re: HDR10 grade: Retaining color & detail in the sky area

PostTue Oct 10, 2017 8:49 am

Piotr, i noticed the same thing on my raw bmpcc shoots when the Lut is applied.
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Piotr Wozniacki

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Re: HDR10 grade: Retaining color & detail in the sky area

PostTue Oct 10, 2017 8:57 am

Interesting - but with RCM which I used with both examples here, no LUT is used... Also, you mention RAW footage editing - and all "Page 2" controls are in fact the very same as those found in the Cinema RAW palette! So it seems natural they work for you - and even are required - for RAW grading. Whereas I'm grading Log - and while the Manual does say they can be used for any media, not just RAW - I find it disturbing I'm unable to achieve the same results without using them. What's more - I never used them before, and yet didn't have problems with retaining the color and detail of highlight areas!



Piotr
Grading system: DaVinci Resolve Studio; Asus X-99 Pro/USB3.1; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; 480 GB SSD system drive; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive; Decklink 4K Extreme 12G driving Samsung SUHD calibrated monitor
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Piotr Wozniacki

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Re: HDR10 grade: Retaining color & detail in the sky area

PostFri Oct 13, 2017 6:19 am

Anyone, please?

Why would lowering Highlights control value retain color better than lowering Gain?!!

Piotr
Grading system: DaVinci Resolve Studio; Asus X-99 Pro/USB3.1; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; 480 GB SSD system drive; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive; Decklink 4K Extreme 12G driving Samsung SUHD calibrated monitor
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Tero Ahlfors

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Re: HDR10 grade: Retaining color & detail in the sky area

PostFri Oct 13, 2017 7:58 am

Have you verified with a probe that your TV can actually do what is advertised? I'm really skeptical about a consumer set doing 1000 nits (or over) with any kind of accuracy. Also there might be some automagical image enhancements going on with the HDR mode that you can't turn off.
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Piotr Wozniacki

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Re: HDR10 grade: Retaining color & detail in the sky area

PostFri Oct 13, 2017 8:31 am

You're right about a consumer product - even though advertised as over 1,000 nits capable - is the weakest link in the workflow like mine. However, I can see the same on my Shogun Inferno (1,500 nits max brightness) when I connect it to my Decklink with 12G SDI... The brightness is still there, but color is fading - and the only way to retain it is cranking the Highlights control down considerably. Back wehn I started grading for HDR10 with this hardware I never even touched this control!

So- considering it wasn't like this at the beginning, and my impression is that it's slowly getting more and more pronounced ever since I noticed it some time ago - it's probably my Decklink card slowly going south :(

Piotr
Grading system: DaVinci Resolve Studio; Asus X-99 Pro/USB3.1; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; 480 GB SSD system drive; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive; Decklink 4K Extreme 12G driving Samsung SUHD calibrated monitor
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Cary Knoop

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Re: HDR10 grade: Retaining color & detail in the sky area

PostFri Oct 13, 2017 3:49 pm

Image
What confuses me is the highlights and shadows setting, which input transform did you use in order to raise those shadows so much? It is further confusing when I look at the scopes below, as the blacks are still not fully resolved even at shadows at +86.50.

Actually, on checking some footage I get Shadows -88, but is it just me or does shadows pull a lot more down than just the shadows under ST2084 which is different from using it under Rec.709? :o

One question about your scopes, isn't there too much in the highlights for HDR10?

Image

One thing I do not like about ACES is the 'bleaching' of color at the highlights, RCM and Logarist maintain far more color in the highlights and it stays within gamut.

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