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Noise in Keylight Footage
I’m pretty new to greenscreen compositing, but I’m noticing something disturbing in my Keylight footage. The key is fine, nice soft edges, etc., but when I look at the final rendered composite, the keyed subject seems to have a lot of noise in it — moving noise.
I’ve tried different settings, but can’t seem to get rid of this noise. Does this seem like a typical problem and, if so, what am I doing wrong?
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10 Replies
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try noise reduction…dv footage will look pretty crappy after doing keys specialy
if there is poor lighting. -
Actually, I’ve read their tutorials, I’ve also watched Andrew Kramer’s great tutorial on keying and I’ve had excellent results as far as the key itself goes. Adjusting of black and white clips has made no difference as far as the noise in the footage goes.
Noise, I might add, that wasn’t there before keying. It’s very odd. I’m using well lit footage, too.
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Hi Rob,
Interesting problem, is it possible you could shoot a couple of plates of the footage, along with the project file, over to support at thefoundry.co.uk so we can have a look? If copyright is an issue then perhaps just some cropped region of the plate would enable us to get a handle on whats going on.
Kind Regards
JackThe Foundry, UK
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Is the noise in the footage, or the matte?
Clint
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It’s in the footage — and wasn’t there before keying. I’m sure it’s just me.
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Noise that may not be visible in the source can be amplified by processing. Apply noise reduction before keying. Personally, I disable spill removal in Keylight, because it can bring out compression and noise also. Instead of spill suppression I use light wrap.
But seriously, apply Remove Grain before keying. It’ll help. You may need to enable temporal filtering, but that slows down rendering a lot, so i’d try without first.
If you’re worried about losing detail by the noise reduction, you could use the resulting keyed footage as a track matte for the original footage. That way only the matte is denoised, but the actual foreground isn’t.
Bar3nd
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Barend makes an important point about noise and spill suppression there: often what happens is that part of your foreground area is close enough to the background that the suppression has to work quite hard to remove what it sees as spill. This involves correlating across the other two colour channels into the screen colour channel (thus the R and B channels are used to help ‘repair’ the G channel); if these channels are noisy then this noise may become amplified by this processing.
To help avoid this you can use the method Barend suggests, you can use a separate spill suppression pass (using the AE spill suppressor if you’re not concerned about bit depth, or alternatively one of the other plugins available), or you can isolate that area of footage and set it as an inside mask. This inside mask is then not processed by Keylight (so not introducing any noise); you can post process this in the colour corrector of your choice if it doesn’t quite sit right in the final plate. This inside mask can either be losely rotoed, or you can pull a hi-con matte by your favorite method leaving this as the alpha channel and then configuring Keylight appropriately.
Jack
The Foundry, UK
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Hi Jack,
Great to have the creators of Keylight get involved around here 🙂 Keylight is an essential part of my toolset. I’m currently pulling mattes from DVCProHD footage (ugh…) and Keylight holds up fine. Although I’m also relying heavily on Red Giant’s Key Correct Pro for de-artifacting and occasionally a bit of noise reduction.
Cheers,
Bar3nd
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Hey Barend,
Thanks for the welcome; long time cow loiterer, so cheers to everyone for such a handy resource for everything from views to chat and news! Glad to hear Keylight is performing well for you; had a play with Key Correct Pro a little while back and they did seem like some neat tools; in fact the reference to other spill suppressors in my previous post was mainly aimed at Key Correct’s rather flexible spill killer 🙂
Cheers
JackThe Foundry, UK
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I had the same problem, I fixed it by changing the soft light setting to hard light setting.
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