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Noise after chroma key with Keylight(1.2)

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Rob GrauertNoise after chroma key with Keylight(1.2)
by on Jan 23, 2014 at 9:45:52 pm

Hi,

I'm having a small problem keying some footage.

The footage is 1080p24 ProRes HQ. I connected a Sony EX3 to an AJA Kona LHi and recorded directly into the computer. The footage is also well lit - Kino Flo lights on our product and an evenly lit blue wall (I used a light meter to ensure it was evenly lit). So this is some very clean footage I have to work with here.

I captured the footage into FCP7, applied a secondary color correction to the blue wall to boost the saturation for an easier key, and then exported as 10-bit Uncompressed for After Effects.

The footage actually keys well - really well - but for some reason Keylight(1.2) is creating noise after I pull the key. The "Screen Matte" and "Combined Matte" views confirm that the key is indeed very clean. There aren't any black blocks sneaking into the white areas.

Any ideas as to why Keylight(1.2) is introducing noise into my footage?

Rob Grauert, Jr.
http://www.robgrauert.com
http://www.facebook.com/robgrauertvideo


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Darby EdelenRe: Noise after chroma key with Keylight(1.2)
by on Jan 23, 2014 at 10:22:50 pm

[Rob Grauert] "Any ideas as to why Keylight(1.2) is introducing noise into my footage?"

It's probably Keylight's crummy despill. Switch to the Intermediate Result instead of the Final result and see if that looks better.

If you then need to despill the footage there are other methods. One is described here:

http://forums.creativecow.net/readpost/2/1027628

That post is for green screens. For a blue screen you would mix the Red & Green channels to produce a new Blue channel (instead of mixing the Red & Blue for a new Green channel).

Darby Edelen


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Tudor "Ted" JelescuRe: Noise after chroma key with Keylight(1.2)
by on Jan 24, 2014 at 12:31:41 pm

Like Darby I recommend using the Intermediate result and a separate Spill Suppressor. Ae's own worked for me quite well. However, in some tough situations you can use this:
http://aescripts.com/spill-slayer/

Tudor "Ted" Jelescu
Senior VFX Artist


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Rob GrauertRe: Noise after chroma key with Keylight(1.2)
by on Jan 24, 2014 at 2:07:50 pm

Wow, MUCH better when viewing Intermediate Result. Thank you!

Rob Grauert, Jr.
http://www.robgrauert.com
http://www.facebook.com/robgrauertvideo


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John CuevasRe: Noise after chroma key with Keylight(1.2)
by on Jan 24, 2014 at 4:43:42 pm

And just to add to the spill suppression techniques, Andrew Kramer at VCP uses the Hue/Saturation effect to remove the green cast from his keylight keys.

The Portal

He starts keying at 7:30, uses the hue/sat effect around 11:30.

Johnny Cuevas, Editor
Thinkck.com

"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.


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Darby EdelenRe: Noise after chroma key with Keylight(1.2)
by on Jan 24, 2014 at 6:31:44 pm

Spill slayer looks to be an implementation of the Channel Mixer method I mentioned. That's almost definitely how it's working under the hood. It's way more straight forward to use though :)

Darby Edelen


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Daniel BroadwayRe: Noise after chroma key with Keylight(1.2)
by on Jan 27, 2014 at 4:00:26 pm
Last Edited By Daniel Broadway on Jan 27, 2014 at 4:02:37 pm

I am one of the creators of Spill Slayer, and Darby is right. It is a variation on the Channel Mixer method to despill. The difference however is that, as he mentioned, it's way more straight forward. In a lot of cases, you can drag and drop, and you're done. It also works in 32 bit, but Channel Mixer only supports 16 bit.

Spill Slayer also allows more algorithms to be used besides the Channel Mixer one. Finally, it will also allow you to generate a spill map (grayscale map of spill areas), and replace spill areas with any other color, such as a color from your background plate for better integration. I hope this has been helpful.


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