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s there any way to have color correction adjust automatically to footage luma?
I am working with some live footage which had automatic exposure on, so the levels go up and down a bit over the course of it. I want to color correct it to make it brighter. Most of the footage is dark, but occasionally it is bright enough. I know I could go through the footage, splice it, and just color correct the parts that need it, but I wonder if there is any way to just use one filter but have it automatically adjust as the luma of the footage changes. Is there any way to do that?
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3 Replies
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I don’t know of any way to do it automatically, but since version 10.4 Final Cut has been able to animate color corrections (including luma-only corrections) via keyframes. The keyframe button appears in the right side of the color correction title bar (the bar that includes the color correction type title, such as Color Wheels or Color Curves, and the mask icon).
The basic workflow is to set a keyframe one of the dark areas, do your correction there, and then move to an area where the luma was okay and make a small adjustment to set another keyframe there. Now the luma correction will animate over time. To fine-tune the transition you can add additional keyframes between these two. To adjust the placement of keyframes, type control-V to bring up the video animation bars, which reveal the keyframes you created and allow you to move them to exactly where you want them.
Obviously this isn’t automatic but what I like is that you don’t need to splice footage plus you can create smoother transitions. I’m using this same workflow to adjust luma on some footage where the sun was going in and out of heavy clouds.
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Forgot to mention that the other advantage of animating color corrections is that you can animate multiple corrections. For example, in the footage I’m working on where the sun was going in and out of heavy clouds, I’m making white-balance corrections too since there are pretty big differences in color temperature under clouds vs. full sun. In your case since it’s just an auto-exposure issue you might only need to adjust luma but if there are color balance issues as well you can correct them at the same time (e.g., if you use the color wheels to make luma corrections, you can move the pucks in the color wheels to also adjust color balance at the same keyframes).
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FYI, there is an OFX plugin in Davinci Resolve (the Studio version only) that actually does exactly what you’re looking for; it’s called Color Stabilizer. It’s possible that a similar plugin is available for FCPX but I’ve never seen one.
In Resolve, the Color Stabilizer OFX allows you to choose a frame in a clip that has the correct brightness and white balance. Color Stabilizer analyzes it, and then adjusts every other frame of the clip to match. It only works on a per-clip basis, so if you have multiple clips with this problem you’d have to run it on each clip. You might have to apply a deflicker afterward, based on reports I’ve seen.
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