Green Screen Dancing Edge Pixels (After Effects CS6)

[Matt Dodds]

This is an image of my green screen set up. When I meant not a great green screen, I meant cheap and wrinkly, not small. It came with my lighting set up I bought.

I am currently not able to record outside, since it is still cold and will be snowing soon! Inside is my only option so far!

Thanks!

[Mark Whitney]

Are you using the Keylight keyer that comes with CS6? There’s a Screen Shrink/Grow control that taking it into the neg direction should help. A tiny bit (like -.7 to -1.5) of that plus a touch of Screen Softness should help.

In the future, try adding a bit of back light on the subject. Doesn’t have to be much; just noticeable to the eye. That will often clean up the subject edges from green spill.

Above all else, use an external mic & get it much closer to the subject, just out of frame. More people will notice that over any matte issues.

[Mark Whitney]

If you can, get it stretched on some sort of frame. Also, get as much distance as you can from screen & subject.

[Steve Bentley]

Adding to Mark’s comments: when shooting blondes try and go for Bluescreen – color keys are really just fancy difference mattes and there isn’t a lot of “difference between” yellow hair and green screens.

[Matt Dodds]

So, that is the reason why I am getting dancing pixels. That does make a lot of sense then. I will try to get a blue screen and get more distance from the screen, than I was before. I think that this footage isn’t usable then?!

[Matt Dodds]

I am using the Keylight 1.2 keyer. I have been using the Screen Shrink and putting it at -2 and the Softness at 2. Neither of these were of any help!

I did put 2 lights on the background to light it up, but I only have fluorescent light bulbs, but I plan to get some LED lights.

I do use a lavalier mic, with a zoom recorder. The lav was in her scarf! I did noise cancel the sound, so that shouldn’t be an issue!

[Steve Bentley]

That screen is probably a little too emerald to be used as a true green screen (real ones are a little more neon/glow-in-the-dark kind of green)
But there’s always a way. What you might be seeing is the compression on the footage. We had some HD footage in the early days of HD on blue screen whos edge was very very ratty. That was pure codec problems.
What codec was used to capture and have to got that original footage or are you working with a compressed version of the original?

We had a client send us some bluescreen footage – the screen was a made of demin – sort blue I guess – but guess what the talent was wearing? That’s the only screen we’ve never been able to pull a decent matte from in 38 years of work.

Next time try getting some green kino flos or similar to light the screen with. The lights you use to light the talent will wash out the screen soon enough so if you can light the screen with the same color as it already is the keys are stellar.
And don’t be afraid of green spill – its actually important because it lets you put some of the new background’s color in as though it’s whats being spilled on the actor.

Can you post a little of the running footage and we can give it a whirl? Doing a comp on a still won’t reveal the dancing edge problem.

[Steve Bentley]

I finally had a sec to pull a key off the still you sent. Is the screen being buffeted by a fan by any chance? I think the dancing edges are the creases in the screen showing up and perhaps fluttering. You may need to use the blur feature in Keylight to pre blur the screen to diminish those.
Or you can pull two keys one for the dark greens and one for light. Or pull two keys one for the body of the person (clamp the heck out of it) and then do a roto matte (very loose) around her head, make a thick fuzzy line out of that mask and then use that as a mask. (basically a halo of the edge of her hair). Combine that with a thin green key that lets some of the screen show through. Then you can have a much less dense matte and you can screen that element in over top of the main chunky matte of her. Because its blonde hair it screens well and lets you keep all those split ends even though the matte isn’t great/solid.

[Steve Bentley]

Like this (the image uploader failed so I had to inlcude it as a file)
12272_edgematte.jpg.zip

[Mark Whitney]

[Matt Dodds] “So, that is the reason why I am getting dancing pixels. That does make a lot of sense then. I will try to get a blue screen and get more distance from the screen, than I was before. I think that this footage isn’t usable then?!”

Replied to this earlier but it vanished into the ozone. Anyway, you might want to take a look at this short making of that shows what can be done on a shoestring budget yet paying attention to the basics:

https://vimeo.com/156679519

VideoCopilot has a bunch of good tutorials as well.

You might research doing multiple keying passes but if you’ve a wrinkled, moving green backing, you’re fighting an uphill battle.

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