Creating a LUT to counteract Gamma shift in Final Cut Pro GUI viewer for more accurate color grading

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Frenshprince Author

Level 1

4 points

Creating a LUT to counteract Gamma shift in Final Cut Pro GUI viewer for more accurate color grading

Hey FCP Users,

As you probably know, some applications on macOS rely on ColorSync to display colors.

That’s the case with Final Cut.

Every video, except HDR, is displayed with an altered gamma in the GUI viewer.

This issue doesn’t occur when using an external video monitor, but that’s not always an option.

The video itself remains unchanged—only the preview is affected—making any color grading inaccurate and different from what you might expect.

Specifically, the GUI viewer makes the content appear brighter.

So if you think your content is too bright and adjust it accordingly, the exported video will look too dark when viewed on anything other than macOS.

Apple hasn’t provided a real solution, despite well-documented complaints from users for over a decade.

So I came up with an idea, tested it, and while it’s not perfect, it works quite well.

ColorSync changes the gamma in the preview from the expected Rec. 709 (2.2 or 2.4) to 1.961.

My idea was to create a LUT that counteracts this shift. By applying it to an adjustment layer during grading and disabling it before export, you can preview the colors more accurately.

I created one in DaVinci to simulate a 1.961 to 2.4 gamma, imported it into Final Cut, and the result is about 90% similar to how it should look without the gamma shift in the GUI viewer.

It’s not a perfect fix because I’m not an expert in LUT creation and don’t have the right tools to refine it further, but it’s a promising approach worth exploring.

[Re-Titled by Moderator]

MacBook Pro 14″, macOS 15.3

Posted on Mar 14, 2025 8:32 AM

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Answer 1

Frenshprince Author

Level 1

4 points

Mar 14, 2025 1:39 PM in response to Clint Gryke

Actually, I understand the issue more than you think.

The Rec. 709-A setting in DaVinci Resolve is just a trick to ensure, as you said, that the video looks the same in QuickTime and Final Cut Pro. But that’s not the real issue here—it’s only a fix for those who will watch their videos on macOS.

The real challenge is ensuring that the Final Cut GUI viewer matches the exported video file when viewed outside macOS. Because of the ColorSync gamma shift, what you see in QuickTime or the FCP GUI viewer isn’t an accurate representation of your video file—it appears brighter. As soon as you play it outside macOS, you notice the problem: it’s too dark. Why? Because you’re grading a video that is inaccurately displayed by your OS.

To answer your second message directly:

• If you stay in Rec. 709 in Resolve, the exported clip will look too bright in QuickTime or FCP but will appear correct outside macOS.

• If you switch to Rec. 709-A in Resolve, the image in the viewer will be brighter than the original, but the exported clip will look exactly the same in QuickTime, FCP, or any ColorSync-managed app on macOS. This is fine if you’re staying within the Apple ecosystem, but not if your content will be viewed elsewhere.

I suggest checking out the CineD article or the YouTube video on this topic.

The consensus among colorists is that you cannot achieve identical results on macOS and other platforms—one will always look worse than the other unless Apple decides to change its gamma display.

I’m not trying to reinvent the wheel here. For serious grading, you need an external monitor, and if you’re using one, you won’t have any issues with FCP since you won’t rely on what you see in the viewer.

I was just offering a method to grade in FCP while ensuring that what you see in the viewer matches what you’ll see when playing the video outside macOS.

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Answer 2

Mar 14, 2025 11:27 AM in response to Frenshprince

I get the feeling that you don't really understand this issue from what you have written. Volumes have been written on various forums and people have argued until they are blue in the face and grey in the hair about what causes it and how to work around it. I can't say I understand it entirely myself nor do I want to as there is a simple solution. There is no point in you attempting to reinvent the wheel here, moreover as you say you don't have a perfect practical solution.

Yes there is a simple practical solution that does work perfectly and Blackmagic have provided it. That is to simply use Rec709A as the Output Color Space in a Resolve Color Management workflow. If you do that what you see in a Resolve viewer (if you have the correct settings in Resolve Prefs) will be exactly the same as what you see when exported in Quicktime, what you see when imported into an FCP SDR project and what you see with the same file exported as Rec709 from FCP. It works. I'd suggest you try it.

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Answer 3

Mar 14, 2025 12:51 PM in response to Clint Gryke

Here’s an image that I hope will clarify what I’m saying. This image is derived from a screenshot of four frames from the same clip laid out side by side on my Mac desktop. Top left is the original clip in a Resolve viewer. The Resolve Project is a Resolve Color Management SDR project with an Output Color Space of Rec 709A. Bottom left is the same clip exported as Rec 709A ProRes HQ viewed in Quicktime Player. Top right is the exported clip imported into an FCP SDR (Rec7 09) project. Bottom right is the same clip exported from FCP as Rec 709 ProRes HQ viewed in Quicktime Player..

Firstly, the screenshot of the four frames was imported into Photoshop. I then used the Photoshop Color Sampler tool to measure the color numbers on a couple of patches in the different images. The values can be read in the Photoshop Info box. One set is RGB and the other is HSB. The values are identical in all four images with very minor variations which are well within any margins of error and way smaller than the effect of the gamma shift issue. Even without the numbers, the four images are essentially identical.

This is a clear demo that exporting from Resolve as Rec 709A resolves the issue. There is no gamma shift whatsoever.

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Answer 4

Mar 14, 2025 2:35 PM in response to Frenshprince

OK. This is extremely confused so I’ll step out now. Life's too short. Good luck with your endeavours

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Creating a LUT to counteract Gamma shift in Final Cut Pro GUI viewer for more accurate color grading

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