HDR - log vs HLG issue

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bronchitis

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HDR - log vs HLG issue

PostMon Dec 28, 2020 6:05 pm

Hi,

In the same timeline I have 2 different clips: one is VLOG and the other one HLG. Both are 10 bit clips from GH5s. When checking histogram under the new HDR wheels I can see the HLG one is quite stretched and represents about 12 stops, but the VLOG is only showing between 4 to 5 stops of dynamic range and is not stretched nearly as much. Color settings for the timeline are:
    Color Science: DR Color Managed,
    Color management preset: DR Wide Gamut,
    Output color space: REC 2020 ST2084 2000 nits
    HDR mastering is for 1200 nits
    HDR10+ enabled
I thought both VLOG and HLG clips would show more or less the same behavior in terms of visible dynamic range, but it's not the case. Can someone explain to me what I'm missing? I'd be grateful for any tips.

Thanks
Greg
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wfolta

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Re: HDR - log vs HLG issue

PostMon Dec 28, 2020 8:27 pm

Does Resolve know what input color space both clips are if you check in Media? I'm guessing it's possible that Resolve thinks the log clip is something else?
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RikshaDriver

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Re: HDR - log vs HLG issue

PostTue Dec 29, 2020 5:32 am

Wayne is spot on.

Unfortunately Resolve doesn't detect the Panasonic custom metadata which other software like Assimilate Scratch does. V-Log footage will always be interpreted as Rec.709 until you explicitly modify the clips.

HLG Footage is also interpreted incorrectly as it should be HLG Scene (as in Scene referred, not display referred).
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bronchitis

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Re: HDR - log vs HLG issue

PostTue Dec 29, 2020 7:13 am

Wayne,

For the LOG clip I manually selected Panasonic VLOG as a color space while the HLG clip is tagged with REC2020 by default.

Asim,

Are you by saying "explicitly modify the clips" suggesting I should for example apply a color space transform to force it into REC2020?

Thank you both for your replies.
Greg
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RikshaDriver

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Re: HDR - log vs HLG issue

PostTue Dec 29, 2020 9:25 am

What I meant is set the Input Color Space to either Panasonic V-Gamut/V-Log or Rec.2100 HLG (Scene) for the respective clips
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Claire Watson

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Re: HDR - log vs HLG issue

PostTue Dec 29, 2020 2:25 pm

Just checked, I have GH5 HLG footage and in Media page Input Color Space it says Rec.2020 (Scene). However if in Color Management I then uncheck 'Use separate color space and gamma' the color space shown in Media page changes to Rec.2100 HLG.
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RikshaDriver

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Re: HDR - log vs HLG issue

PostWed Dec 30, 2020 10:21 am

You shouldn't use Separate Color Space and Gamma unless you know what you're doing.
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