CIExy scope not showing HLG

[cicero]

Whenever we feed HLG 1000nits images to the internal Flame scope set to CIExy, it gives an Incompatible Colour Space error on the scope.
Is this a bug? It’s very annoying.

@AdamArcher I think you’ve done plenty of HLG work?

[AdamArcher]

I have done a bit of HLG work. However, the main body of work has always been at P3D65PQ and then I have applied a Colour Space Transform at mastering our stage to get to Rec2020HLG, and that has mostly been in Resolve to produce the IMF.

What colour space are you working in and what colour space is the media you are working from?

[AdamArcher]

Also, can you please take a screenshot of your scopes to see the issue that you are seeing?

[cicero]

Thanks Adam. Will try to do a screenshot tomorrow if I can get in front of it.

Working P3PQD65 but with a View Transform (via a Viewing Rule) to make it HLG on Broadcast Monitor. Hitting Bypass on the viewer (so now seeing it P3PQ) makes the scope kick into life.

Same happens if I bring in HLG media and Tag Only as HLG without any Viewing Rule.

All the other scope options (waveform, vectorscope etc) work fine, it’s just the CIExy not behaving (it would be very useful to check that the HLG Rec2020 is P3-constrained).

[AdamArcher]

Your colour gamut should not be affected by the gamma. If you are changing from P3D65PQ to P3D65HLG then your gamut should be the same.

[cicero]

Sorry for delay, busy few days.

Sure, gamut and gamma are different things, but I’m going P3-PQ to Rec2020-HLG (pretty sure P3-HLG doesn’t exist, HLG always has to be Rec2020 primaries). Anyway as I said, it happens if you just keep everything HLG (Tag Only, no View Transform etc), so it feels like it’s probably a bug… or I’m missing something pretty basic in the scopes setup!

In all three examples below, Scopes Settings say Do Not Sync (to Viewport or Broadcast).

1. Prefs > Colour Management > Scopes Colour Space = HLG
   Scopes Settings > Vectorscope > Video CbCr
   Media is HLG
   Scopes show ok:
   

   

2. Prefs > Colour Management > Scopes Colour Space = HLG
   Scopes Settings > Vectorscope > CIExy
   Media is HLG
   Scopes show incompatible:
   

   

3. Prefs > Colour Management > Scopes Colour Space = P3 PQ
   Scopes Settings > Vectorscope > CIExy
   Media is P3-PQ
   Scopes show ok:
   

   

[AdamArcher]

P3-D65HLG definitely exists. I believe it is the native display colour space on the iPad Pro for instance. It isn’t how you would deliver to DPP but in a P3-D65PQ to Rec2100 HLG workflow, your colour gamut would still be P3D65 contained within the larger BT2020 gamut.

If I get time on Monday I will have a look. This will be new to me too though as I always mastered out of flame at P3D65PQ, or as BT2100PQ and created my BT2100HLG deliverables out of Resolve. Essentially, I would use Flame to create a DSM that I would then create all the versions out of Resolve as I needed to create IMF deliverables that Flame can’t do.

One other thing. The BBC/DPP has a P3D65PQ to BT2020HLG transform (may have been in the form of ia LUT) that they insisted on using the last time I delivered to them. I believe it needs to be licensed but if you are delivering to them then you may need to use that. From memory, when I compared it to a straight colour transform, the result was identical anyway.

[cicero]

Thanks Adam. I’d never heard of P3D65-HLG so there you go.

As mentioned in another recent conversation, we are working at P3D65PQ but want to view at Rec2020 (=2100) HLG, before we then burn that same View Transform into the eventual deliverable export.

Managing Multiple Grades

Sorry, didn’t explain properly. Not looking to compare side-by-side or anything like that. Totally agree with all your points about the pitfalls and futility of that! Our primary del is the HLG, so that’s what we (only) want to be looking at with the client while we do the work. But we want to be actually working in PQ until export, because the PQ > HLG conversion is more solid than HLG > PQ (so don’t want to bake it to HLG at grade export or Flame import), and obviously for the secondary PQ d…

So the pipeline is working but I want to see that HLG on the CIExy scope, to check that it is Rec2020 primaries but constrained within the P3 gamut.

I think our exact colour pipeline is actually a red herring here, it just seems Flame won’t display whatever-gamut, with HLG gamma, on a CIExy scope.

Thanks for mentioning the BBC LUT. We collaborate with BBC R&D a fair bit, so yes that’s the one we’re using for the View Transform. We also found the same as you, that it matches a standard transform anyway

[AdamArcher]

Have you contacted support? I reread your posts and now understand that you think there is an issue with the scopes, not the transform itself. They should be able to recreate it if that’s the case.

Have you looked at an external scopes solution such as Omniscope or 4K scopes? My preference is to have something available externally, especially when you can take snapshots and compare outputs of applications/systems more easily.

[cicero]

Contacted support. This is a fault (“incorrect behaviour”) with the scopes in HDR and has been logged as a Change Request so will hopefully be fixed soon.

Thanks for the input Adam.