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help with a noisey key

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jonas espinoza
help with a noisey key
on Mar 17, 2010 at 8:57:55 pm

hi there

if anyone with more keylight experience than me could lend a hand, i am at my wits end with the noise in the blacks.

this was shot with HDV, not by me, but everything else is keying reasonably, but somehow this guys sweatshirt is really noisey and flickery.

here is the link for the footage/project
and thanks in advance!



1. Download Link: Click here to download file
http://rapidshare.com/files/364713378/noisey_key.zip.html
MD5: C10330DFDE1437D890E078A15004EC41






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Michael Szalapski
Re: help with a noisey key
on Mar 17, 2010 at 9:21:43 pm

Security reasons where I work prohibit me from downloading your file from rapidshare, but I can link you to some useful stuff on getting better keylight keys.
Great info here and here. You might also consider using this method on all your keys.


- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Dave LaRonde
Re: help with a noisey key
on Mar 17, 2010 at 9:51:24 pm

I see that the footage is 1440x1080, so I'll bet it's HDV, and still in its acquisition codec to boot. In addition to the wise advice Michael points you to, you should also read this:

Dave's Stock Answer #1:

If the footage you imported into AE is any kind of the following -- footage in an HDV acquisition codec, MPEG1, MPEG2, AVCHD, mp4, m2t, H.261 or H.264 -- you need to convert it to a different codec.

These kinds of footage use temporal, or interframe compression. They have keyframes at regular intervals, containing complete frame information. However, the frames in between do NOT have complete information. Interframe codecs toss out duplicated information.

In order to maintain peak rendering efficiency, AE needs complete information for each and every frame. But because these kinds of footage contain only partial information, AE freaks out, resulting in a wide variety of problems.


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


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jonas espinoza
Re: help with a noisey key
on Mar 17, 2010 at 11:41:55 pm

thanks dave, but the thing is i still get the horrible noise in the blacks on the movie i output for this troubleshoot, which was quicktime PNG transcoded from the HDV sources (i know, not ideal. i got brought in to amimate some stuff around it. the keying, the client assumed, would be the easy part)





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Dave LaRonde
Re: help with a noisey key
on Mar 18, 2010 at 3:19:44 pm

Glad you converted footage to ProRes. I presume from the thoroughness you've described, you also used garbage mattes, animating them where necessary, to make keylight's task easier.

I've had similar problems with noise in dark colors using Keylight. Here's what I did:

http://forums.creativecow.net/thread/2/931091#931104


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


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jonas espinoza
Re: help with a noisey key
on Mar 18, 2010 at 1:39:55 am

thanks for the links, its good stuff, but most of it i know already

it keys ok on all the other interviews shot with the same camera on the same green screen.

somehow, the dark gray sweatshirt this guy is wearing is super noisey after applying the key.

would anyone have a second to have a look? thanks



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Joey Foreman
Re: help with a noisey key
on Mar 18, 2010 at 2:38:56 am

You'll get the best results by combining a core matte and an edge matte, and using that as a luma track matte for the original footage. With the core matte filled completely, you'll be left with the original shirt underneath, so there can't possibly be more noise than on the unmatted footage.
There are step-by-step instructions for how to do this here:

http://forums.creativecow.net/readpost/2/974490

If the original footage has the noise, you can use the same track matte in combo with an adjustment later to which Remove Grain has been applied. If the talent moves a lot you may have to rotoscope some masks on the the non-grainy areas to prevent the loss of too much detail.

If the noise is predominant at the edges, you can add some pre-blur in keylight on the edge matte.


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