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Chromakey issue: noise in dark areas after applying Keylight 2.0

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Nicholas Natteau
Chromakey issue: noise in dark areas after applying Keylight 2.0
on Sep 15, 2011 at 3:25:38 pm

After shooting my green screen interview using Reflecmedia Litering and my AF100, I brought the footage into Final Cut Pro and used Keylight 2.0 to chromakey.

But whereas the original footage is clean, the chromakeyed footage has lots of noise in the dark areas, especially to the right of the talent all over the chair leather. Please see my footage here:

http://vimeo.com/29095983

Not sure what I'm doing wrong in Keylight.

Thanks in advance for any advice help with Keylight in FCP.


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Mark Suszko
Re: Chromakey issue: noise in dark areas after applying Keylight 2.0
on Sep 15, 2011 at 3:48:20 pm

Sounds like you need to make more adjustments to the chromakey settings. Try expanding the sampled green color a bit. I find it helps to work separately on the luminance component and then the chroma component. Also, use garbage mattes and masks to cut away as much of the nonessential background as possible, and concentrate on making the key immediately around the talent as clean as it can get.


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Dave LaRonde
Re: Chromakey issue: noise in dark areas after applying Keylight 2.0
on Sep 15, 2011 at 3:48:50 pm

Reflecmedia does indeed make a bright green background, no?

I use Keylight a lot in After Effects, and I've found that if the green screen is TOO bright a green, the result is what you're seeing.

The solution in FCP would be to put two identical clips on the timeline, one precisely above the other. Pull the key on the top clip, and don't worry about the noise. Just use it as an alpha matte for the lower clip. Poof! No noise in the darks!

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


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Nicholas Natteau
Re: Chromakey issue: noise in dark areas after applying Keylight 2.0
on Sep 15, 2011 at 4:18:19 pm

Hi Mark and Dave, thank you both very much for replying and helping me out.

Dave, I don't see any change at all after applying the alpha matte to the top clip in FCP. The noise is still there. My Keylight settings for this clip are:

Screen Gain:1
Clip White: 0.5
Screen Blur: 2.8
Clip Black: 0.43 / Clip White: 0.61
Screen Dilate: 1
Screen Softness: 0.2


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Dave LaRonde
Re: Chromakey issue: noise in dark areas after applying Keylight 2.0
on Sep 15, 2011 at 4:36:01 pm

Sorry, I can't help you with the step-by step. I merely know it can be done. The lower layer uses the upper layer's transparency to create its own transparency, but it sounds like you've still got the upper layer visible.

Perrsonally, I don't chroma key in FCP. I prefer to create completed shots with foreground and background plus light wrap, color correction and and fake shadows in After Effects. I suppose if somebody held a gun to my head, I could look up the procedure for using an alpha matte in the FCP manual, learn it for you and write back. But nobody's holding a gun to my head right now....

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


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Nicholas Natteau
Re: Chromakey issue: noise in dark areas after applying Keylight 2.0
on Sep 15, 2011 at 5:12:35 pm

Hi Dave,

No problem at all. I just figured it out. I had the lower clip on alpha matte instead of the upper one, my bad.
Now no noise, poof! all gone! exactly as you explained. Thanks so much for the tip! I like the humor about the gun! :)


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Egor Maraev
Re: Chromakey issue: noise in dark areas after applying Keylight 2.0
on Sep 27, 2011 at 8:49:44 pm

Good day, Dave!

I have the similar problem using Keylight in After Effects, and i've prepared some screenshots of what i did, so please, tell me what's wrong here.

I try to use your method: duplicate layers, then use the top one as an alpha for the layer beneath. It reduces black points as if i increase Clip Black parameter. But it doesn't reduce the noise (i showed in screens three sequential shots and there is a lot of noise).

Here is the zip file with screens from my monitior: http://www.sendspace.com/file/tt0rzh

If you could help me, i'll be very grateful for you!
Thanks!

P.S. I don't want to remove all the shadows of table and sofas. And i don't want to make the floor be very clean. It should be with gray spots on it, but without this noise on theese spots.


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Nick Natteau
Re: Chromakey issue: noise in dark areas after applying Keylight 2.0
on Feb 18, 2012 at 6:31:11 pm

Hi Dave,

I was wondering if you could possibly take a look at my chromakeying work in Keylight that I posted here on Vimeo, it's a short screencast of the noise issue I keep encountering in Keylight, no matter what I do:

Screencast


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