Display Color Management with MP4 files

[maximeb24899079]

Hello.
I'm working with BT709 MP4 files (offline editing of movie trailers). I have an external EIZO screen for monitoring purposes and an LG Ultrafine for UI.
Premiere Pro 25.2.1 : what the "Display Color Management" setting does regarding that type of files?
I have two movies as an example: one seems better with it (a lot less saturation but a more contrasty image) and the other one is dull and way too dark when the setting is on.
So, what is the general rule with this improved color management on "standard" BT709 files?
TIA!

Cheers.
Max

Macbook Pro M1 Max / Sonoma 14.7.1

[R Neil Haugen]

Bt.709 ... or more commonly called Rec.709 ... specifically states the monitor should apply a display transform of essentially gamma 2.4 to the image, that the total brightness of "white" should be at 100 IRE (now often conflated with NITS), and of course the color space is sRGB/D65.

(The actual brightnes transform is a "power law" curve, technically ... but gamma 2.4 is close enough to be used instead and is shorter to type.)

So if your Eizo is correctly set up, and you are not on a Mac, then ... things should be relatively straightforward.

The monitor should be set & calibrated for Rec.709.

Then in Premiere by the Rec.709 specs you should set the viewing gamma dependent on the lighting environment you are working in!

This latter is actually technically correct but not what is normally said.

If working color in a normally lit, office environment, you should set the Premiere viewing gamma option to gamma 2.2/web.

This doesn't have spit to do with 'web', it's just the proper display tranform for working in a bright room.;

If doing color work in a very dark though not quite black room, then and only then should you use the Premiere viewing gamma option of gamma 2.4/broadcast.

And the whole "web" and "broadcast" terms are incorrectly applied here, completely ignore them. Set the viewing gamma accrording to your working room brightness.

As to your media differing ... that is highly likely due to improper color management by whoever created the file. Sadly, and pretty much expected.

Set your system correctly and then do color work on the files to get them looking 'right'.

[maximeb24899079]

Thank you!
Thing is, when Display Color Management is on, changing the gamma has no effect over the transmit device. It just changes the gamma of the UI monitors.
Which is a good thing, because the EIZO takes over as it is indeed set to BT709 (Gamma 2.2 in my case, I work in a lit environment).
But even if the gamma doesn't affect the external monitor, the image changes drastically, and I think for the worst, actually. So my question really is: do I need to check that box when working with BT709 sources? I understand that the file itself might not be properly color encoded, but beyond that?
Oh and I do work on Mac.

[R Neil Haugen · Accepted solution]

DCM is needed for most folks. But depending on the level of the calibration of the monitor, you may not want or need it.

In my case, the Transmit Out is definitely affected by changing that ... and that monitor used for TO is calibrated and profiled outside of Premiere.  So I don't want the program to make changes based on the initial OS data on it. I want that proven image.

I've got a Decklink, and will be going to that at some point rather than TO.

But if people haven't really worked their calibration routine to a fare-thee-well by checking with a profile pass, they should probably use the DCM on.

You may well be in a situation, with that Eizo, that you're better off without Premiere mucking about.