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Need help with problematic keing

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Maxime Marquis
Need help with problematic keing
on Feb 8, 2010 at 3:26:41 pm


I'm editing a music video that contains a lot of green screen footage to key out. The problematic shots are those of a "human doll" that have yellow hair. No matter what I try, I cannot key out the green without losing opacity in the hair.

I know, it's a pretty bad idea to shoot yellow in front of a green screen, but a reshoot is out of question.

Any tips on how I can get it to work? I use keylight.

I need help... Thanks

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Dave LaRonde
Re: Need help with problematic keying
on Feb 8, 2010 at 3:42:50 pm

Here's about the only thing I can think of: isolate the hair with an animated garbage matte, and key the hair part of the shot only. You can then match it up with the rest of the keyed shot later.

The process of keying grows MUCH tougher if the footage is DV or HDV, both of which have notoriously lousy color resolution.

And of course, the usual admonition against using any kind of interframe-compressed footage in AE applies.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA

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Kevin Camp
Re: Need help with problematic keing
on Feb 8, 2010 at 5:24:17 pm

keylight also has a feature called 'inside mask'. it allows you to define the area that it will not key.

an easy way to create an inside mask is to apply keylight and create a 'harsh' key (where you're not concerned about the edges, just the inside/core matte area).

once you have that, set the view to 'intermediate result' and apply a second instance of keylight. pick the screen color and set the inside mask setting for source alpha to 'add to inside mask'. that will take the matte form the first keylight effect and use it for a core matte for the second keylight. then you can focus on the edges.

you can use this in conjunction with aharon rabinowitz's super tight junk mattes technique, that creates a matte for everything outside the foreground element. then you're only keying just the edges of the character.

Kevin Camp
Senior Designer

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Philippe Lessard
Re: Need help with problematic keing
on Feb 8, 2010 at 7:28:29 pm

Maybe you better to do a color correction/removegrain before you key the shot, try to replace the yellow by something else an avoid to change your green, there a couples plugin(BCC) or software(color) to do just that.Then key the shot, use this keyed shot as a track matte over your original shot(the one with yellow hair) and you're done.Remember the only important color in your shot was the green,since keylight can key any color you just need to have a solid flat background to key, then use this keyed shot as a track matte.You can also divide your shot with different keylight setup(like said before) and/or(for more precise setup)track the problematic region and apply a keylight setup to this portion.I always use those technic on problematics shots and it work great.Also if you didnt have the key correct pro plugins suite, check it out!

Hope this help

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serj bato
Re: Need help with problematic keing
on Feb 8, 2010 at 8:26:05 pm

you can also use color key. using the color picker, pick a specific area on the green screen clicking on ly once. then
drag the tolerance & feather properties carfully. don't worry if it's not properly keyed out, you can duplicated the color key
and pick another area of the green screen. I've tried this before using as many as 6 color keys to do the trick. If this doesn't
work well, you have no choice but to animate a garbage matte for the hair as what Mr. Laronde advised.

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