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How to select areas to key?

Posted: Wed, 25th Mar 2009, 2:55am

Post 1 of 2


Force: 0 | Joined: 25th Feb 2007 | Posts: 1


I have video with a subject sitting on a green screen table, in front of a blue screen. I use a garbage matt to remove all but a small halo around the subject. It keys out all of the blue background no problem, but the green table is having issues, like some spill. I want to be able to isolate the table like with a mask and use the keys on just that area.But I cant figure out how to apply a key to just a certain area.
Posted: Wed, 25th Mar 2009, 3:00am

Post 2 of 2


Force: 17995 | Joined: 20th Jan 2002 | Posts: 6124

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Here's what I would do:

If you apply a greenscreen key, it will automatically only affect the green area, i.e. the table. Apply a second key for the bluescreen, to remove that. Use garbage mattes to remove any extraneous bits that are beyond the keys. Or am I not understanding? Its always very difficult to give keying advice without seeing what we are talking about. If I am not understanding you here, perhaps you can upload a brief clip of the footage and give us a link, or even a single frame, before any keys are applied, so we can see what you are working with. will host images for free if you don't have webspace.

Keying automatically only works with a certain portion of the footage, based on the color data contained therein. that's what keying is. all keys are reversible, so they can either be used to remove or retain the color they are set up to affect. Garbage mattes likewise can be used to either retain or remove portions of the screen, but based on a shape that you draw in.