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Grading HLG BT-2020 (Sony a7iii) - video export looking different than grade

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Eric Jaminet
Grading HLG BT-2020 (Sony a7iii) - video export looking different than grade
on Nov 24, 2018 at 11:53:38 am

Hello,

I edited and graded HLG2 BT-2020 clips on DaVinci Resolve using the following parameters:

Color Space
DaVinci YRGB Color Managed
Color Space: Rec.2020 / Gamma Rec.2100 HLG
(for Input/Timeline/Output)

When I export the video, I get completely different results with different colors.
Does anyone know how to fix that without changing my gradings?

I am not using an HDR monitor and don't need the video for that purpose. I've been testing different options for hours, including changing to Rec.709, it only gets worse.

Thank you in advance for your help!!!



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Marc Wielage
Re: Grading HLG BT-2020 (Sony a7iii) - video export looking different than grade
on Nov 25, 2018 at 4:10:19 am

If you don't have an HDR monitor, it's not possible to grade HDR. You'll drive right off the cliff.

If I were you, I would check the entire signal path in Rec709, make sure that what you see is what you get, and then work on what it will take to actually grade HDR. Just getting past the monitor (and calibration) is a huge hurdle.

MixingLight.com has a good 5-part series on what it takes to work with HDR (including Dolby Vision), and I would recommend them highly. Note that this is a pay site, but I believe you can try it out free for a week or two and explore their tutorials.


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Eric Jaminet
Re: Grading HLG BT-2020 (Sony a7iii) - video export looking different than grade
on Nov 25, 2018 at 2:13:35 pm

Thank you for your answer. I will definitely check this out when I have some time.

For now I just changed my parameters to:
- Input: Rec.2020 - Gamma 2100-HLG
- Output: Rec.709 Gamma 2.4

and I used a "Gamma 2.4 to HLG" 3D lut to "convert" the look of the footage in the timeline

I suppose it is not the right or best thing to do but it seems to work well with my footage for now, as I need results fast, and the colors seem a little better than if I put Rec.709 2.4 in both Input and Output. I could be totally wrong.



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Marc Wielage
Re: Grading HLG BT-2020 (Sony a7iii) - video export looking different than grade
on Nov 25, 2018 at 11:35:12 pm

[Eric Jaminet] "I suppose it is not the right or best thing to do but it seems to work well with my footage for now, as I need results fast, and the colors seem a little better than if I put Rec.709 2.4 in both Input and Output. I could be totally wrong."
Why do you think you need HLG at all? If your resources are limited, you could just color correct in normal Rec709 space and call it a day? There are affordable Rec709 monitors out there that can work, provided they're calibrated. Beyond that, whatever you do will wind up as guesswork.


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Bill Stephan
Re: Grading HLG BT-2020 (Sony a7iii) - video export looking different than grade
on Nov 26, 2018 at 10:22:28 pm

Eric,

Please note well that HLG is a "compromise" method of HDR intended for use on broadcast programming. HLG is intended to display a usable picture on both HDR and SDR monitors, but the end result will be noticeably different from separate color grades for HDR and SDR. This is most likely how HDR content will be distributed on broadcast and cable networks in the future, and there is very limited HLG distribution in England right now.

I would not use HLG unless I were required to deliver in this format.

Bill Stephan
Senior Editor/DVD Author
USA Studios
New York City


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Marc Wielage
Re: Grading HLG BT-2020 (Sony a7iii) - video export looking different than grade
on Nov 26, 2018 at 10:27:51 pm

I know very well what HLG is and have been following it for at least 5 years. What display are you using for it, and how was it calibrated?


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