Use Mac color profiles for viewers

So, I am not a professional colorist. I use Resolve for viewing dailies and exporting graded stills to whoever needs to see them. I use a 2021 MacBook Pro, with the display profile set to the Rec 709 preset that it has. I know from comparing to the grading monitor in a color suite that it's actually a pretty good match. The stills I export always look the same as the frames did in Resolve when I look at them in Mac preview on the same laptop.

Just recently, I was told that I should have the "Use Mac color profiles for viewers" box checked in my preferences. I did so, but now my exported stills don't look like they did on the Resolve timeline. In Mac preview, they are noticeable darker. Put another way, Resolve is now noticeably brighter. If I re-import the still into Resolve, it looks as it should compared to the timeline. There's obviously some color management issue here, but I don't know enough about it to fix it.

So, is the Resolve image "correct" and it is just being displayed wrong in Preview, or is it the other way around?

Thanks

Great question. Posting here so that I can track the answer. When you say 'preview' do you mean selecting the clip in Finder and hitting the space bar?

When you say 'preview' do you mean selecting the clip in Finder and hitting the space bar?

That, but also the actual Preview application.

There's a lot to explain about why you are seeing that.

The "use Mac display color profiles" preference option color manages the Resolve GUI viewer via macOS Color Sync based on the settings in the output color space of each project's settings [BTW - Resolve's current default output color space setting of REC709(scene) should almost never be used since that is a scene referred color space rather than a display referred color space, and IMHO it is a bafflingly bad choice by BMD to make that the default output].
When the "use Mac display color profiles" preference option is not checked, the Resolve GUI on macOS is not managed, so whatever the native spec of the display is will be what gets sent to macOS ColorSync (though this may be treated differently on Macs that support and are set to a reference mode as that gets treated as the native spec of the display). Stills exported from the Resolve gallery as DPX, TIFF, or PNG are not tagged with a specific color sync profile, but that untagged RGB typically gets managed for display as sRGB by default. And JPEG stills exported out of Resolve get explicitly tagged as sRGB, regardless of any other Resolve or macOS settings. So, if you've been exporting any of those formats as stills, that's why the image is matching when you have the preference option unchecked — you have an unmanaged Resolve GUI getting treated as 2.2 gamma REC709 (per the reference mode setting that you chose) and stills being treated as sRGB which is essentially the same gamma and exactly the same primaries, so on your display as set those will appear the same.
Working unmanaged as you are, however, has consequences when you go to export a video file from that project to play on another color managed device, or if you move unmanaged stills to a display set differently than your own. Even if the video and stills matched on your own display, the image will no longer match on a display of a different spec, or if you switched your mac to a different reference mode. If you instead set the Resolve preference on to "use Mac display color profiles", and you want your exported stills to match your Resolve GUI viewer image on other color managed apps + devices, you'll need to ensure that the output color space setting in Resolve *and* the ColorSync Profile applied to the exported stills is the same (also, when moving between devices in different lighting environments there are also perceptual differences to account for, which is a whole other deep rabbit hole). Or, when using the default sRGB profile on stills, you'll need to transform them from your output color space to sRGB before exporting the stills.

It's also worth noting that if, instead of grading in the Resolve GUI, you're working on standard BT.1886 calibrated reference monitor, the default sRGB tagged gallery still JPEG exports will be a relatively close perceptual match on any other macOS device in the usually brighter surround outside of the color suite reference environment.

These links have additional info about color management of stills and video that I recommend reading/viewing:
https://www.provideocoalition.com/understanding-color-management/

Thanks Jamie, for that very informative answer. Very helpful.

Today, I was grading at Company 3, and I had a chance to do a not very scientific test. I know from past experience that my MacBook retina screen is a pretty good match for the grading monitor in the color suite, when set to the BT-709 BT-1886 profile that it comes with. So I opened up Resolve and compared a frame on the grading monitor with an identical one in the Resolve viewer my laptop, first with the Use Mac Color Profiles checked, and then with it unchecked. It matched much better unchecked.

Obviously different setups yield different results, and every computer looks a little different, but for me, it seems like with my MacBook set to 709, and Resolve set to ignore Mac color profiles, the stills I export look the same between Resolve and Preview, and also look substantially the same when viewed in a professional color suite.

As I said, not a scientific test, but close enough for my purposes.

Sounds like you should be asking the folks at Company 3 to answer these questions

Kidding aside, that tracks with what I explained. With "use Mac display profiles" unchecked, and the Macbook Pro in reference mode set to BT.1886, then the Resolve GUI is being sent to the screen without the output color space setting having any impact. In theory, it should be the same as sending the signal out BMD i/o to external display. Though personally, I'm always wary that any OS or Resolve update can introduce bugs that change the GUI image, which has happened in past, most recently with a few of the v17 point releases until BMD fixed it. So if working that way, after any update, I'd recommend another double check against an external BT.1886 reference display. Just to be sure.

If you turn on "use Mac display profiles" then you've got to manage the output color space setting to control what is being sent to ColorSync. And Resolve's default output color space setting of REC709(scene) is always going to look wrong. I do not know why BMD picked that as the default. It was a bad choice IMHO.