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Keying - Despill Bias

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Marc LucasKeying - Despill Bias
by on Dec 30, 2013 at 10:33:02 pm

When I use the Despill Bias colour picker and click on the skin tone it makes the footage/talent noisy. Why is that?


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Dave LaRondeRe: Keying - Despill Bias
by on Dec 31, 2013 at 5:50:11 pm

Typically it's because the chroma key background is too hot.

On well-shot video, I like to use 2 layers with Keylight applied: one to pull a key with nice edges, which I use as an Alpha Matte. On the layer below, I use Keylight just to remove the spill. You'll know you've gotten the spill when the chroma key background on the lower layer goes gray but doesn't disappear. You have to play with it.

If you were anticipating that a good chroma key would be a fairly straightforward procedure, I'm sorry to be the bearer of bad news: it rarely is.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Marc LucasRe: Keying - Despill Bias
by on Jan 2, 2014 at 10:41:40 am

Thanks for the comments Dave.

I will have a look at your suggestions. One thing I did notice was that if I pulled the key initially without using the Keylight Despill the key is actually quite good and the talent looks ok but as I have mentioned it goers wrong when using the built in Despill, however, if I use a separate Despill plugin I don't seem top get the aforementioned grain after applying?

In relation to the green BG being to hot what kind of levels do the green BG need to be for future reference, thanks


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Dave LaRondeRe: Keying - Despill Bias
by on Jan 2, 2014 at 3:13:36 pm

Since I tumbled onto the 2-layer Keylight despill trick, I haven't played around with much of anything else, so I'm no help there.

Keylight in particular seems to like a little darker chroma key background. If you look at nicely-lit chroma key shot, the brightest part of the shot, i.e. white, would be at 100% on a waveform monitor: there's a viewer for that in Color Finesse.

The chroma key background would be at 65-75%. It should work fine. And of course, the better the codec used for acquisition, the better the key.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Marc LucasRe: Keying - Despill Bias
by on Jan 2, 2014 at 5:23:31 pm

Just to follow on I thought I'd upload a screen grab of the Colour Finesse screen of the talent in front of the green screen. The green looks quite even but only at around 40-50% so is that where you suggest the green screen should be brighter up to 70ish?

https://dl.dropboxusercontent.com/u/2003727/Screen%20Shot.png


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Dave LaRondeRe: Keying - Despill Bias
by on Jan 2, 2014 at 5:53:58 pm

That shot looks just fine! That's a nice background. It might be a little on the dark side, but I don't know why you'd have any problems with it. Sure, you might lose a few stray hairs, but I don't see any bad spill on the subject. It would really show up on white clothing, too.

I can't figure out why you're having problems unless you're trying to use Keylight intuitively, i.e. no looking at a few tutorials on using it. They'll help.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Marc LucasRe: Keying - Despill Bias
by on Jan 3, 2014 at 11:04:41 am

I'm not having problems really I hope thats not how things came across. The only hiccup I had was when I applied the Despill function in Keylight but looking back I really didn't need to use it on the footage. Appreciate your comments and help though.


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Marc LucasRe: Keying - Despill Bias
by on Jan 6, 2014 at 1:04:27 pm

Hi Dave

Really not sure whats going on here I've been playing with the key again. The original footage is fine no noise whatsoever. When I go to pull the key and apply minimal key light settings I get noise on her head.

settings

https://dl.dropboxusercontent.com/u/2003727/Screen%20Shot%202014-01-06%20at...


Vid

https://dl.dropboxusercontent.com/u/2003727/test3.mov.zip


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Marc LucasRe: Keying - Despill Bias
by on Jan 6, 2014 at 1:33:54 pm

to update heres a screen grab of the Status showing green

https://dl.dropboxusercontent.com/u/2003727/Screen%20Shot%202014-01-06%20at...


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Dave LaRondeRe: Keying - Despill Bias
by on Jan 6, 2014 at 5:15:12 pm

Don't use the keyed footage as your final product. Use it as an Alpha Matte for the duplicated & unkeyed footage. See what happens.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Marc LucasRe: Keying - Despill Bias
by on Jan 6, 2014 at 5:17:47 pm

I've since had a go with that and worked way better:-) Just sorting out the edges now, might have to do the head and body in two separate sections due to the hair not sitting right.


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