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alternative keying method in AE7?
I was just wondering: can the following method be used for keying (instead of a greenscreen)?
(1) Put camcorder on rock-solid tripod facing any background (probably a simple one in colours different from your actor’s colours); do not move camcorder during whole exercise.
(2) Record a still of the background.
(3) Record the actor’s performance before the background.
(4) Have the computer compare the still (without the actor) with the movie (with the actor).
(5) Have the computer key out all pixels which are the same as in the still (i.e. the background), thus leaving only the ones which are different (that is the pixels making up the actor).My question would be: is this practical and can it be done with AE7? Is there a tutorial or something on this?
Thanks!
Steffen
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4 Replies
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Difference Matte, or Difference Key.
Beware, though. If any pixels match, you have to mask them manually. These pixels are usually brown, gray, or other neutralized colours, which are quite prevalent in the real world, unlike 255 Red, Green or Blue.
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Also, getting a clean key with a Difference Matte is pretty much impossible without significant tweaking. Video noise and other factors cause ‘differences’ in the pixels. Not to mention the frightening capability of even a ‘locked down’ camera to twist mere fractions of a degree without alerting you =O
Darby Edelen
DVD Menu Artist
Left Coast Digital
Aptos, CA -
Yep. I think Difference Keying is mostly theoretical. 🙂
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All the Serious Magic (now part of Adobe) products use Vector Keys, which combines Difference and Chroma keys to get a good result.
If your project is at the low end of the scale, Visual Communicator does a pretty good job.
Graham
https://www.quinceweb.com – web design
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https://www.shiveringcactus.bravehost.com – Free FX for amateur films
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