Technical LUTs working incorrectly for Sony's slog 4:2:2 footage - Premiere 2022 on M1 Mac

[majcyy]

After being super confused why my workflow got destroyed over night I finally realised that the difference in my case is made by 4:2:2 clips. Applying technical LUT to 4:2:2 footage delivers incorrect results, image is blown out and oversaturated. Same LUT in same version of Premiere with same files looks correct on my windows machine. 4:2:0 clips work the same accross both laptops. I tried with multiple slog to rec709 LUTs and with many different clips. Any ideas what can be resposible for this?

[chrisw44157881]

there's new color management settings. check your colorspaces in file interpret and sequence.

[R Neil Haugen · Accepted solution]

Yes, check the sequence color management settings ... previous versions assumed all would be transformed to Rec.709, this version does not. That's a major behavior default change.

Plus for clips there are settings under "Modify/Interpret footage" for color managment including applying LOG correction LUTs and color space over-rides.

Also, check the preferences ... it sounds like one of your rigs is a Mac? That should definitely have the "display color management" option turned on in the prefs. Most people on PCs should also unless they've really tightyly calibrated and profiled their monitors.

Neil

[majcyy]

Hey Neil, I just wanted to say big Thank You! I was struggling with it for days and the Interpret footage was the option that everyone suggests but everything was set to Rec 709 and what did the trick was the ''Display Color Management'' tick box, I'm saved, once again thanks!

[R Neil Haugen]

Always glad to just get someone working. That's the whole point of this user-to-user forum, right?

Neil

[majcyy]

I hate to get back to that issue but opening my project again on this beautiful Monday morning I realised the issue is not resolved. I'm super confused as I remember looking at correct colours of my footage in project's timeline the other day when Neil first explained what needs to be done.

So just to maybe provide extra clues I attach the screens of how ticking the ''Colour Management'' box helped, how it was before and how it rendered on a windows machine (so yes the problem persist on my M1 Pro Mac), there might be one more layer of secondaries there but the point is nothing is clipping.

To me it just looks like the LUT is being read wrong now, the colours look more or less ok now but it's clipping that footage's highlights, which definitely shouldnt be the case.

Sequence and clip's settings are set to Rec 709 colour space. Any ideas what's wrong now?

[R Neil Haugen]

I would love to test a clip on my machine. If you upload a short clip to wetransfer/dropbox/whatever and give the link either here or via personal message, I'll check it on my rig.

Neil

[majcyy]

Thanks for trying to explore this issue further, here's some sample footage and the LUTs, 300mb total so shouldn't be too bad. Just one more thing I realised, maybe it's not related to chroma subsampling but to the codec being used. When I shoot H.264 it ends up being 4:2:2, and HEVC is 4:2:0, and I missed that intially when look at properties of clips that get messed up.

https://we.tl/t-jTyp1XeZOQ  

[R Neil Haugen]

I just tried both LUTs with both clips. And had no troubles, but I think the reason you did is simply not fully realizing the true nature of LUTs.

They can do seemingly amazing things, but the colorists I know all call them the dumbest math out there. You have to be careful in testing them before using them as most LUTs actually can in the right (or perhaps, wrong) circumstances do amazing artifacting. So for some clips of a job they might work fine, but something with darker shadows or highlights or something is mangled.

And all LUTs are built for clips with specific color and tonal range values. Any clip "outside" those values gets clipped. So all the colorists I know teach applying LUTs after a node (Resolve) or 'layer' in an Adobe app, where you can trim the tonal ranges and saturation to fit within the LUT so it won't clip the whites, crush the blacks, or over-ramp color.

And ... in applying both these LUTs, for each clip, I found that applying them in the Creative tab and using the Basic tab controls to 'trim' the clips into the LUTs ... worked beautifully. No clipped data at all. In fact, as I brought the "exposure" slider down after dropping a LUT onto the guy clip, I could watch the clipped line of forehead area simply become the full data of a properly exposed image.

So ... it might be how you're applying the LUTs. Here's an image showing the Scopes and the Basic tab settings, with the SLog3->Rec.709 LUT applied in the Creative tab.

Neil

[majcyy]

Thank you Neil for taking the time to test the LUTs! I'm with you that LUTs are just LUTs and can be a good starting point at best. The issue here is that the Leeming LUT is my trusted technical LUT to bring the slog to rec 709, and it's been working as such fairly well, it still does on HEVC 4:2:0 clips, it just behaves oddly on my mac machine on these clips that I sent you.

I guess I'm always rushing with these replies and not being very scientific with examples and explanations. This time I took the time to properly compare two clips on windows laptop and M1 Mac and I realised that the problem starts even before applying the LUT. I attach two waveforms of raw clips before adding the LUT. It's same timeline, same settings for sequence and the project, same file, same latest Premiere Pro 2022. And you can see that the waveform starts at different point on one computer than the other. Clearly there is a software issue there and it prevents me from working with my old project files on new Mac without reworking color correction from scratch.

[R Neil Haugen]

Ahh, PC and Macs ... there's a fun issue there, in that the wonderful folks at Apple chose intentionally to "reinterpret" video standards differently than all others. Mac OS has it's ColorSync color management system, that does two rather nasty things to video media.

First, they only apply the first of two required transforms. The apply the camera (scene) referred transform, but not the also required display transform.

Second, they chose to apply an odd gamma of 1.96, when the Rec.709 standard clearly and directly calls for gamma 2.4, with 2.2 acceptable for "bright room" working environments.

In order to get around that as best as possible, the Pr engineers added the "display color management" option in the Preferences. All Mac users, and most PCs should have this checked. Unless you're running a pretty solid CM setup with stringent calibration/profiling to Rec.709, that should be selected.

So ... checking to make sure that the Mac has the "display color management" option selected, does that help at all?

Neil