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shadow on green screen (keying, masking, roto-ing in AE)

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Robbie Tassaroshadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 6:03:38 am

First timer here:

I'm editing a project that contains a 90 second long 2 shot on a green screen. When one subject is on the screen, everything is great. When the 2 of them are on the screen, that is where my nightmare begins.
I looked around on this forum for a similar problem and found almost the exact same issue and here is what someone suggested:

You can also create an "inverse–junk matte" very tightly around the inside of your body, and then key out the light and dark green separately. Something like that is probably too dark for a keyer like Keylight, so you'd need to use a luma–keyer like Extract.

I'm pretty sure that is what I have to do, but like I said before, got a first timer here!
I tried going in frame-by-frame and animating a mask for the 1-2 second durations where the 2 subjects serparate enough to see the shadow between them, but couldn't really figure out how to get rid of the mask when they came together and it was unnecessary for the mask anymore. I turned down the opacity but then lost the subjects as well.

I've attached some screen shots so you cans get a better idea of what I've got going on. Any help explaning how to fix this is greatly appreciated.





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craig whitRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 1:49:06 pm

Unfortunately, roto is probay going to be the answer here. If you can get a key to work, it will probably be a combination of every trick you have(luma, keylight, multiple garbage mattes, etc) If precision isn't important, you should be ok but are still looking at many hours of work. If this has to be super tight, you may want to get a few guys to help out. Good luck !


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Robbie TassaroRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 3:55:05 pm

that is what I figured, thanks.


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John CuevasRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 2:15:35 pm

If you are going to mask, why not roto out the shadow. Create a mask around the shadow and change the mask mode to subtract. Then when the actors converge, just move the mask off screen.

Johnny Cuevas, Editor


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Michael SzalapskiRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 2:46:16 pm

This looks like a good lesson learned for the future: get your talent as far from the chroma screen as possible.

You may not need to do full on rotoscoping. It may be possible to key out the shadow area first, then do your main key. Most professionals do more than one pass on the keying. In the keying collection of tutorials here on the COW there are a couple of ones you should check out, Procedural Matte Creation and Creating Super Tight Junk Mattes might also be helpful.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Tudor "Ted" JelescuRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 3:23:06 pm

Way too close to the green screen- rotoscoping all the way would save you some headache. Key out whatever you can as best as you can and leave the shadow area for a second pass.

Tudor "Ted" Jelescu
Senior Compositor/VFX Artist


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Robbie TassaroRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 3:58:38 pm

when you say a 2nd pass, do you mean key out the green that I can and mask out the shadow and render it out... or should I be doing multiple renders with different effects on raw or keyed footage?


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Michael SzalapskiRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 4:30:04 pm

Multi-pass keying just means applying different instances of various keying effects to the footage.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Tudor "Ted" JelescuRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 7:50:18 pm

Aye! What the Great One (or not so..)said. Although in the not so long ago past, that really meant key, render, then roto then render, then comp then render...now a days you have the processing power to have it all done in one comp.

Tudor "Ted" Jelescu
Senior Compositor/VFX Artist


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Todd KoprivaRe: shadow on green screen (keying, masking, roto-ing in AE)
by on Dec 27, 2010 at 8:09:22 pm

As long as we're talking about lessons to learn for next time:
Those wrinkles are going to be a pain to deal with, since each wrinkle introduces its own set of shadows and multiple shades of green. If you're using a cloth screen, be sure to get rid of the wrinkles. Also, lighting from multiple angles to evenly light your green screen _really_ helps.

There are a lot of keying tips here, by the way:
"Keying introduction and resources"

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Todd Kopriva, Adobe Systems Incorporated
Technical Support for professional video software
After Effects Help & Support
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