Quickly fix faulty green-screen footage
Learn how to get quick keying results from compressed or badly shot green-screen footage with the Key Cleaner effect and remove color spill using the Advanced Spill Suppressor controls.
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[male narrator] One of the most common post-production techniques is shooting a performer in front of blue or green screen, with the ultimate goal to key out the person and composite against a different background later.
Adobe After Effects has long had excellent keying tools, but for years it's been accepted that there's only so much you can do with a bad piece of footage.
This situation has improved now with 2 new effects, key cleaner and advanced spill suppression.
The first one we'll talk about is key cleaner, and it can work wonders on bad footage.
And it's worth noting— you don't really want to use it on anything except bad footage.
It's designed specifically to deal with blocky compression noise in a key; the kind that looks ugly and causes your key to chatter.
If your footage doesn't have those problems, you can safely ignore key cleaner and just use your favorite keying effect.
But if your footage does have those problems, key cleaner can be very helpful.
Let's apply it to this medium close-up of a blond woman shot on green screen, a notoriously difficult situation to get a really clean key.
This scene is pretty well lit, but the footage is compressed with H.264, and that will produce some artifacts that would ordinarily make this a challenging key.
If we apply Keylight and sample the green, and we switch our comp over to our alpha view to evaluate the key, you can see that our edges have some noise in them.
You've probably seen this before, and you know how hard it is to get out.
Keylight can sometimes choke past this, but Keylight is a fairly complex tool; not everyone is comfortable with the workflow and in the end, you are likely still losing detail.
There has never been a great, simple solution to fixing this before.
But if we apply key cleaner after Keylight, let's see what happens.
The first thing you should know is these new plug-ins are designed to work with the original RGB data from your clip.
But Keylight has built in spill suppression that will change the RGB by default.
So the first thing we'll do is change the display setting to intermediate result.
This applies the key to the footage without otherwise changing its color.
With its default setting, you'll see that things are already a little smoother.
Key cleaner uses the same approach as the refine matte feature that you may already be familiar with in Photoshop and After Effects.
And if we can look at the parameters, you'll see only 4 controls.
Edge radius defaults to 10.
Set this down if you're seeing the mask grow in an unwanted manner.
In the case of this shot, I'll set this down to about 6 since the top of the head doesn't need to expand.
Reduce chatter is the real miracle worker here.
It does a temporal smoothing effect that does wonders to remove the noise in our matte, which we can clearly see if we zoom in.
And adjusting the alpha contrast will help clean up any leftover compression noise that may show up in the clear areas.
Don't over due this slider since it can start to eat away details that you might want to preserve, but a value of about 15 percent will fix this clip just fine.
And the strength slider let's you back off of your final effect, if you want to re-introduce a little bit of grain— if you need to match your background for example.
Let's switch back to RGB, turn on our background, and see that we have a pretty decent result.
Now the other new filter in the keying suite, is the advanced spill suppressor, and to see how that works, let's turn off these layers, and turn on our close-up.
Now spill suppression is designed to work in concert with the other keying tools.
And since Keylight will probably be your first built in choice and the key cleaner will likely be a common companion for many of you, all 3 of these plug-ins have been wrapped into an animation preset.
If we just type in the word key into the effects and presets panel, you can see it right up here.
Keylight plus key cleaner plus advanced spill suppressor.
Let's add that to our footage, and notice that this adds all three effects to the footage although the spill suppressor is turned off, so we can first evaluate the rest of the matte.
Keylight is already set to use intermediate result, which is great, select our background color, turn on reduce chatter as before, and set the alpha contrast to about 10 percent.
This look pretty good, but if we turn on our background, we can clearly see that there's a strong green spill still present on our edges.
This is very typical of any blue or green screen setup, and it's not the worst thing, if the background happens to match the screen color, as in this example, but it can look terrible if there are contrasting colors.
Spill suppression helps get rid of that.
So if we just turn on our advanced spill suppressor, we can immediately see a better result.
And this is what most of you will want to use.
However, you can toggle standard to ultra to expose a whole new set of controls.
In fact switching to ultra completely changes how the plug-in calculates its results based on the Ultra Keyer in Premiere Pro.
You'll only need to poke around in here, if you have a specific case, such as refracted color contamination.
Otherwise standard should serve you well for most footage.
After Effects has always been a great solution for a keying and compositing workflow.
And with the addition of the new key cleaner and advanced spill suppressor, it now works better than ever before.
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