Color-managed sequence gets brighter when changing frame size?

[Brennish Thomson]

I recently have been diving into the color managment settings to correctly display color/luminence on my OSX /studio display for web uploads, and while setting my program display to 1.96(QT) and using a QT comp LUT on the exports seems to work for my exports, I just went to change my sequence frame size from 4096x2160 to 3840x2160 and in the process it once again made everything brighter in my program monitor.  Before/after and screenshot of my color managment settings. What gives?

[Brennish Thomson]

Update: I find that even just opening and saving the sequence settings has the same effect.

[Brennish Thomson]

Another update: After changing a setting within the lumetri panel in my first screenshot, it had the same effect as changing from the sequence panel, but this time it has "permamently" changed the gamma/contrast in my program monitor. I find that applying the QT comp lut produces the correct results in the export, but in the program monitor it now has "incorrect" gamma/contrast. Just confused a bit whats going on. Perhaps what I was viewing originally was simply my program monitor not correctly reading the settings, which is why when simply changing a different unrelated setting caused it everything to change as it was now actually reading the other color managment settings. So if we assume thats whats going on, does that mean my premier-pro specific settings are fubar causing the issue within the program monitor; so I should shift those; or are my color managment settings now correct and I have to re-grade all my footage? (keeping in mind the QT-comp LUT seems to fix the export result atleast)

[Brennish Thomson]

Final update for the evening: Switching my program monitor gamma to 2.2 (web), along with the QT-comp LUT on-export via media encoder, seems to yeild the correct brightness on QT, Youtube, and within premier. Not sure if this is ideal overall but I am going to document my settings; panel screenshot included in this comment; more to ensure I can return to these settings later. 

[R Neil Haugen]

Ok, a little education.

First, toss the use of the ancient "gamma comp'' LUT, as there is a more sensible workaround now. That is, if you want to make an image that looks sorta like you want on only Macs without Reference modes that are set to HDTV. But is too dark and contrasty on all broadcast compliant systems, Macs with Reference modes set to HDTV, and nearly all Android devices, TVs, etc.

In the Color Management section of the Lumetri panel, the Settings tab, the tab named Settings ... set the Viewer Gamma to 1.96/Qt. Then just work the file as you want, and export without any LUT applied. The export will look very much like you in-Premiere view if viewed on QuickTime Player, or Chrome or Safari browsers. Like unto the old LUT thing.

Of course, it will be dark and contrasty/oversaturated in VLC and Potplayer, on Macs with Reference modes that are set to HDTV (so they use the correct display gamma for Rec.709), broadcast compliant systems, TVs, Android ... about everything else.

Because the issue is caused by Apple choosing to use a non-standard display gamma for Rec.709 video but only on their 'prosumer' Macs.

The full-on heavy duty Macs have screens with the Reference modes, with the option for HDTV, which uses the correct Rec.709/Bt.1886 display transform used by everybody but the Macs without Reference modes.

So your choice ... is your choice. Just understand exactly what you are choosing. As you cannot make a file that will look the same (well as much as is possible) on both Macs without Reference modes and everything else.

But setting Viewer Gamma to 1.96, then doing your color correction to your liking, is a vastly better replacement for the gamma comp LUT than using that LUT.