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difference matte problem

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Muhammad Hassan
difference matte problem
on Jun 15, 2010 at 9:26:01 am

I am trying to use "difference matte" as an alternative for the "green screen".In my video my camera is not moving at all. I am trying to remove everything from the video except my body but whenever I try to do this I get my body getting transparent instead of the background.
The steps I took are as follows:
1 An image of background with no body as the upper layer.
2 The video clip as the second layer.
3 Applying effects > keying > difference matte to Background
4 having the clip with the body as "Difference Layer"
5 And finally get my body transparent (which I do not want).

Please tell me where I am making the mistake. Thanks

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Michael Szalapski
Re: difference matte problem
on Jun 15, 2010 at 1:32:20 pm

Body as upper layer
Effect applied to Body layer
Difference layer background layer without body.

Sorta the opposite of what you've got. Which makes sense, since you're getting the opposite of what you want.

Although, to be honest, Difference Matte rarely pulls a good key due to variations in color (especially in compressed formats like HDV or DV. You may need to employ some rotoscoping.

- 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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Dave LaRonde
Re: difference matte problem
on Jun 15, 2010 at 3:14:07 pm

In addition to what Michael says, you should never consider AE's Difference Matte as an adequate substitute for doing a proper green or blue screen. Unless the footage is absolutely perfect, and it almost never is absolutely perfect, the results will be less than satisfactory.

Difference Matte: a great idea in principle, but extremely difficult to use effectively.

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

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