"Photo Booth" Chroma key

Question

Level 1

10 points

"Photo Booth" Chroma key

anyone know of a plugin in FCP that will do a "chroma key" like the way photo booth does its' chroma key effect?

pretty much instead of keying out blue or green, photo booth asks you to step out of frame then saves the image, when you step back into frame it keys out the background the same way you could key out the color green.

I haven't seen it, but I'm wondering if there is a way to do this in FCP.

Mac OS X (10.5.3)

Posted on Jun 3, 2008 7:04 PM

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Answer 1

Jun 3, 2008 7:09 PM in response to zijital

Difference Matte...just make sure the camera is locked solidly in place, with guard dogs and a barbed wire/chain link fence around it.

; ]

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Answer 2

Jun 3, 2008 11:21 PM in response to zijital

As mentioned - that is NOT a chroma key in photobooth - it's a difference matte (you've got one in FCP)...

If you look at my reel the third row, second column - with the cat - there's a shot where the ball just misses the cat. That was originally supposed to be shot to be a split screen, but the DP didn't understand that and changed the focus and lighting slightly between the "cat pass" and the "ball pass". I had to use a difference matte to marry the two and thus was able to capture the shadow on the wall from the ball, etc...

Patrick

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Answer 3

zijital Author

Level 1

10 points

Jun 4, 2008 3:22 AM in response to Patrick Sheffield

thanks for the help so far.

I've tried the difference matte w/o much luck so far. the video I'm using is a person that walks in front of a book case.

the final image is translucent & a mix between the person & bookcase. it is keying out the rest of the image well enough, but why is it mixing the person w/ the bookcase?

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Answer 4

Jun 4, 2008 7:09 AM in response to zijital

You'll have to adjust the sliders in the filter...

Remember it is a "difference" matte - that is, it looks for what is different from the still in the image well. If something is the same color and light level as what you put in front of it, a hole will show thru...

Patrick

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Answer 5

zijital Author

Level 1

10 points

Jun 4, 2008 1:27 PM in response to Patrick Sheffield

ok so most of my experience is w/ chroma key, so that is how I think of this. I understand that FCP takes the difference layer & thinks of it similar to a green screen. you adjust tolerance & threshold to fine tune the matte / key. I also know that there is a little bit of noise in the video (I'm shooting these tests on -6db gain to get the cleanest image) which will make the same pixel "NTSC" (never the same color 😉 frame to frame.

but this is the best I can get it w/ my tests

http://i30.tinypic.com/2dt3k3b.png
http://i31.tinypic.com/2hg6b2q.png
http://i28.tinypic.com/15eju4o.png

this is w/ the threshold at -90 & the tolerance at 0. is this filter really this poor, because I've hit the wall in the parameters and it feels like I should have more room to move around. is this the best FCP can do? if so is there a third party app that can actually do this better?

or are there any more tricks, like progessive vs interlace, DV vs HD, etc.

these are some of my first attempts that were creating more of a blended key.

http://i30.tinypic.com/k53fo2.png
http://i26.tinypic.com/9saplg.png
http://i31.tinypic.com/fvdxth.png

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Answer 6

Jun 4, 2008 9:54 PM in response to zijital

Well, you've got a red handled hammer over a wood background. Brown is just low intensity red, so you're running into a "lack of difference"... Same deal with the flesh tones...

You could clean up the matte, but you REALLY should shoot against a different background...

Patrick

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Answer 7

zijital Author

Level 1

10 points

Jun 4, 2008 10:42 PM in response to zijital

I've got my answer, although I'm not impressed w/ the power of the filter as I'd like it to be. oh well I guess I'll just have to wait a few more years for better algorithms to be written.

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Answer 8

Andy Neil

Level 4

3,795 points

Jun 4, 2008 11:40 PM in response to zijital

zijital wrote:
I've got my answer, although I'm not impressed w/ the power of the filter as I'd like it to be. oh well I guess I'll just have to wait a few more years for better algorithms to be written.

Or you could plan your shoot better and not be relying on the post-production process to come to the rescue...

Andy

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