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Advice with REALLY bad green spill on color graded footage

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Don StroudAdvice with REALLY bad green spill on color graded footage
by on Aug 23, 2015 at 6:44:14 pm

Disclaimer: I'm relatively new to AE, but after several months I know enough to be dangerous... to myself.

So I'm working on some footage that was handed to me recently. It's several shots of people working on monitors that have a green screen graphic displayed on them, not a green screen fabric or paper overlay. So the actors sitting 18 inches from these monitors have the mother of all green spill on their faces. So much so that, when I apply Keylight, giant chunks of their faces disappear in the keying. I guess, technically, there's no spill at that point... because it all goes away!

I'm aware of mattes and things like that, but... I'm looking at matting the curves of a profile, animated, over the course of several seconds per shot. There has to be a different way.

So my question is: how do you key the monitor without removing the details of the faces, so that I can then apply the spill removal?

Thanks in advance for your help/tips/tricks/advice!


My setup: AE CS5.5, Macbook Pro with OS X Yosemite

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Spencer TweedRe: Advice with REALLY bad green spill on color graded footage
by on Aug 23, 2015 at 7:52:40 pm

Hey Don,

It's a little bit unclear to me weather you need help with the key or the spill... I'll give you advice for both and maybe I can help you out!

In the world of keying/spill suppression you always want to separate out these steps, particularly in Keylight which has a VERY sensitive and aggressive spill suppression algorithm. You also want to often pull your matte in multiple keys (though this isn't always necessary). It's a bit hard to explain this in text without showing you but I'll do the best I can!

Basically you apply keylight to your footage and get a good looking key (looking at Screen Matte in the View dropdown). Then if you need to do any roto on top with either a black layer or white layer, or even a second key if needed (which it sounds like you will). Then without switching your View dropdown pre-compose the whole lot - keys and rotos.

Now pull your original un-keyed footage back into your comp and start your despill. I recommend two approaches - first apply Keylight, select your Screen Color and change your Screen Matte -> Clip White to 1 (thus only despilling and not keying at all). Second if that doesn't look good (it rarely does) try this free plug-in: The last is a magical plug-in that will work 90% of the time!

Now put your pre-comp (which is now your matte) on top of your newly despilled foreground and set your despilled clip to "Luma Matte" your pre-comp.

Boom! A little light-wrap, some further color correction, and you should be good to go!

- Spencer

PS with really spill'd footage you might also need to do a degrain. I would do this on your clip, pre-comp it, and do all of the above with your pre-comp instead of the raw source. I also sometimes just pre-render out the degrained plate to speed things up.

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Don StroudRe: Advice with REALLY bad green spill on color graded footage
by on Aug 23, 2015 at 8:06:56 pm

Spencer, thanks for the quick reply. I'm both glad and saddened that someone else is working on a Sunday afternoon...

I'm curious about the white/black roto step you mentioned. I completely understand rotoscoping, even though I've never really had to do it, but I don't get its use in this particular instance. Are you saying that I'd have to go in and rotoscope out the actress sitting in front of the monitor, animating the roto over the span of the shot, cutting her perfectly out?

And then (forgive my ignorance), but how would that work with the footage in creating a better key?


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Spencer TweedRe: Advice with REALLY bad green spill on color graded footage
by on Aug 23, 2015 at 11:37:43 pm

Haha, such is our life I guess!

The rotoscoping would be to fix up any problems. You mentioned a lot of spill in the foreground, which to me usually means that your key isn't going to be perfect. For example her eyes might reflect some of the green, or if she is wearing glasses those will be a problem, etc. In these cases you can just create a white solid on top of your key (but pre-comp'd in the end) which covers up these holes.

Conversely if there is a bad reflection on your screen, or, lets say, tracking markers on your green you would need to create a black solid to "garbage matte" those out. A keyer will of course never key out a black X or piece of tape, so you need to roto those out with a black solid so they don't come through the key.

How's the spill looking?

- Spencer

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