The Truth About AI Auto Masks in Final Cut Pro

There are a lot of videos hyping up the new Auto Mask feature in Final Cut Pro. Mine included. But nobody is telling you the full story: this tool is not perfect. So let's go over when you should use it, when you should not, and a pro tip fix for one of its biggest problems.

Two ways to add an Auto Mask

First route: go to the magic wand icon (also called the enhancements menu, for you nerds out there) and choose Add Auto Mask, or press Control Command K. This is the route I'd take if you want to cut someone or something out of your shot.

The other way is directly on your effects and color correction tools. Go to the icon that looks like someone was punched in the head, hit Auto Mask, and choose what you'd like masked out.

Where Auto Masks shine

One: it's instant. No analyzing and no tracking needed, unlike the Magnetic Mask. FCP automatically knows the perimeter of things in your video, and with one click it masks them out. As far as I know, no other editing software has anything like this right now.

Two: real fine-tuning. The Shrink/Expand slider moves the edge of your mask in or out. Grabbing too much background? Shrink it. Cutting into your subject? Expand it. Erode is different: it keeps the edge exactly where it is and feathers around it, inward or outward. And Blur softens the whole thing. Compared to the Magnetic Mask, where all we had was a feather slider, this is a real upgrade.

Three: they're copyable. Press Command C on the clip with the mask, then paste onto another clip with Command Shift V and select the effect carrying the mask. Even easier: drag straight from the inspector onto other clips, or onto the viewer if the playhead is over the clip you want to copy to.

Four, and this one is sneaky good: if you extend your clip, the mask automatically adjusts and applies. The old Magnetic Mask workflow would make you analyze again. This one does not care. It's instant.

The stuff the hype videos skip

I'm guilty of this too. I was very excited when this feature came out, and I still am, but I'd be doing you a disservice if I didn't mention these.

One: you're limited to the menu. Sometimes you want to select something in your shot besides what shows up in the Auto Mask selection menu. If it's not on the list, you're out of luck.

Two: you cannot adjust the mask itself. When FCP doesn't understand that your subject continues into the background, you get unavoidable flickering, and there's nothing you can do about it. Unlike the Magnetic Mask, you can't click points to add to or subtract from the mask. The weird thing is that on some shots it holds perfectly, and on others it changes its mind about your subject frame by frame.

Three: multiple people, one mask. If there are several people in your shot, you can't just select and adjust one person. Or can you?

The fix: isolate one person with Intersect

I figured out a way. Say I pull up the hue/saturation curves, add an Auto Mask, select Skin, and I only want to adjust one person. Problem is, it selects everyone, and there's no way to choose who you want.

First, make a wild adjustment so you can see what you're working with. I'll swing the global hue vs hue slider until everyone starts looking like they got a big whiff of the Final Cut Pro, and add a little blur to make it more gradual.

Now go back to that masking icon and add a Magnetic Mask on top of it. Select the person you want adjusted (remember, you can hold Option to deselect areas from the mask) and hit Analyze. Yes, this means we're back to using the Magnetic Mask for cases like this, which takes some processing time, but it is what it is. Hit Done.

You might be thinking: well, that didn't work, you idiot. Fair. But here's the secret: go to the blend mode on the mask and click Intersect. Now the adjustment only hits where both masks agree, which means just your chosen person. And if you'd rather adjust everyone except them, select Subtract instead.

Here's the truth about all this masking stuff: selecting your subject is step one. Knowing what to actually do with that selection, with the color, the exposure, the skin tones, that's what separates an okay edit from one that looks expensive.