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Final Cut Pro X: An Even Better Keyer... Again!
Iain Anderson on Tue, July 24th 0 comments
Iain Anderson revisits an earlier article on the excellent keyed in Final Cut Pro X and finds ways to improve the results even further.

A little while ago, I wrote an article that showed you the secrets of the new Keyer in Final Cut Pro 10.0.3. The technique shown there worked really well if you wanted perfect edges, but it had one flaw: the interior of the remaining subject could have been left a little darker than is ideal. Here, we'll look at how to use masking to get everything just right.

1. Some background

Here's a quote from the original article, talking about the Spill Suppression parameters:

To lighten edge fringing that's too dark, you could drag the black point up. Here, though, we need to darken edge fringing that's too light, and we'll drag the white point down, quite a long way, to about 0.3. Note that the subject becomes slightly darker when you adjust this option, but this can be fixed with the Color Board (or some other sneaky tricks '" perhaps detailed in a future tutorial).

Essentially, the controls that make the edge of the key perfect don't only affect the edge of the key. And yes, while you could use the Color Board's Mask feature to brighten the interior of the subject, you'll be fighting noise. There's a better way.

2. Setting it up

Let's start with the finished key that you achieved after working through the previous tutorial. The edges are great, but the inside might be a little dark '" it is with the sample image I've used. If you haven't worked through that old tutorial, now's a perfect time!

As before, we'll be using a clip from the generous people at Hollywood Camera Work:

Download the Hair Detail video linked there, and follow the instructions in the original article. Eventually, you'll have the Keyer effect applied to a clip on top of a Vivid background generator. The key setting to fix the appearance of the dark hair against a bright background is Spill Suppression, where you drag the White point down to about 0.3. The edge will be good, but the subject's face is dark.

Subject's face is dark

Not exactly ideal for color correction.

3. Cloning the keyed clip

What we're going to do is to clone the keyed clip, reduce the Spill Suppression to get the color back to normal, bring the edges in quite significantly, then soften them. In this way, we'll get the original color back without losing the very nice key we've already achieved.

To clone that keyed clip, click to select it, then press the Up arrow a few times until you're at the start of the clip, press Command-C, then finish with Command-V. The newly pasted clip will automatically be placed on top, in sync.

After a quick copy and paste, your timeline should look like this : 

The timeline after copy and paste

The timeline after copy and paste.

4. Change the top clip's Keyer parameters

Select that top clip, and open the Inspector, then the Video section there. Look through the Keyer parameters to find the Spill Suppression, and drag the white point back up to 1.0. Icky edges return along with the correct face color.

To see what's going to happen in the next step, let's hide our original clip. Select the lower keyed clip, then press V to hide it. Select the top clip once again to continue.

Open the Matte Tools section, then drag the Shrink/Expand parameter to the left. You'll see the edges come in, but probably not far enough. Click on the number to the right of the slider, then drag to the left to change it to less than -10. Also drag Soften up, to around 5.

Keyer with holes

Yes, you'll see holes.

5. Fix the problems

Clearly, this has some issues: many holes that the background shows through. Luckily, there's a Fill Holes parameter just above. Drag it up, just a little, to 0.2-0.3, to restore the face but leave the edges missing.

Keyer filled holes

And now it's all good except the edges.

The missing edges, of course, will come from the clip below that we hid earlier. Select that clip, then press V to show it. It should look great: the clean edges of the original clip below, and the rough, soft-edge key on top to preserve the interior detail.

Finished product

The finished product!

This technique can be applied to many similar scenarios '" there's no need to give up if you can't get a perfect key with just one layer. Good luck!

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