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Grainy Blacks/Shadows in Green Screen Footage

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Jim Murphy
Grainy Blacks/Shadows in Green Screen Footage
on Apr 14, 2013 at 10:19:23 pm

Hi All,

So I've imported a bunch of green screen footage shot in 1920x1081 (codec is ApplePro Res 422). The shadows/blacks in this footage appear grainy in FCPX, but do not look grainy in the master files.

Also, when I drop in Keyer, in some spots I get bleedthrough of the inserted background. I'm able to fix most of it but I am wondering if the way the footage was shot could be the root of both of these issues.

Any suggestions as to why these issues are happening and how to possibly fix them would be appreciated.

Thanks in advance!

Jim


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Jeff Kirkland
Re: Grainy Blacks/Shadows in Green Screen Footage
on Apr 14, 2013 at 11:55:11 pm

Possibly whatever you're using to view the footage outside of FCPX is crushing the blacks and hiding the noise? What does it look like on a broadcast monitor? That's really the only way to judge it.

As to the key, sounds like you left some holes in the matte. Can't really say much there without actually seeing a sample of the footage but it will come down to either a problem with the footage or on your side of the equation, just not getting the best out of the keyer filter.

You didn't mention what camera was used to shoot the footage.

I may be slow but for what it's worth it took me about six months and many tutorials to master the FCPX keyer (master might be an exaggeration) and get to the point where I'm confident I can pull a good key on just about anything I'm given.

Anyway, happy to advise if I can but we'd probably need to see a sample of the footage and have some idea of the process you went through to finesse the key once you applied the filter.

Jeff Kirkland | Video Producer | Southern Creative Media | Melbourne Australia
http://www.southerncreative.com.au | G+: http://gplus.to/jeffkirkland | Twitter: @jeffkirkland


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Jim Murphy
Re: Grainy Blacks/Shadows in Green Screen Footage
on Apr 15, 2013 at 2:44:41 am

Pulling the key doesn't seem to be the issue. When I look at the footage (shot with a Sony PMW200) in Quicktime straight up, it looks OK... but yes a tad dark which may be hiding the noise. When I open it in FCPX it is immediately apparent that there is something going on with the image in those black/shadowy areas. Have not gotten this footage to a broadcast monitor just yet.

Tried to play with the image in Color Corrector to no avail.


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Jeff Kirkland
Re: Grainy Blacks/Shadows in Green Screen Footage
on Apr 15, 2013 at 4:46:47 am

Ok. I guess I got confused because your post mentioned that there were bits showing through your key and that it was still only mostly right.

There is a gamma difference between FCPX and the Quicktime Viewer. In theory, FCPX is colour managed so that should be the most correct rendition of your footage. Without seeing the footage, I'd assume it's camera noise?

Cheers,
Jeff K

Jeff Kirkland | Video Producer | Southern Creative Media | Melbourne Australia
http://www.southerncreative.com.au | G+: http://gplus.to/jeffkirkland | Twitter: @jeffkirkland


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Mark Smith
Re: Grainy Blacks/Shadows in Green Screen Footage
on Apr 15, 2013 at 12:03:47 pm

Camera set up for green screen critical. I'm guess that if it was a sony camera with a standard scene file, the camera might have a bit too much detail enhancement dialed in, which is frequently the case with sony and some other cameras. Unfortunately detail enhancement is the enemy of chroma key in that it frequently adds noise to dark areas, essentially its enhancing the noise and that causes havoc with keying.
Its far better to use a bit less contrasty camera profile and dial the detail wayyy back. On my C 300 typically I have the detail reduced to -10 or so because even at the out of the box detail setting of zero there is far too much enhancement for a pulling an easy key.


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Jim Murphy
Re: Grainy Blacks/Shadows in Green Screen Footage
on Apr 15, 2013 at 12:13:54 pm

That was my assessment... Camera issue. So having said that, is there an effective way in FCP to reduce the issue?


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Mark Smith
Re: Grainy Blacks/Shadows in Green Screen Footage
on Apr 15, 2013 at 1:21:26 pm

That's out of my pay grade. I don't thinks so however. baked in camera issues tend to remain baked in. I'm not really an editor though I do try to stay abreast to a degree of what is happening in post. An editor friend once told me the difference between shooting and editing which boiled down to this: In the edit if you don't have some right you can command z a bunch of times and get back to where you were, however with shooting you pretty much have to get it right as there is no command z...


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Jeff Kirkland
Re: Grainy Blacks/Shadows in Green Screen Footage
on Apr 15, 2013 at 9:20:07 pm

This is where a noise reduction plugin is a life saver. Neat Video is probably the best. I haven't tried the Magic Bullet one since they released the new version.

Jeff Kirkland | Video Producer | Southern Creative Media | Melbourne Australia
http://www.southerncreative.com.au | G+: http://gplus.to/jeffkirkland | Twitter: @jeffkirkland


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Jim Murphy
Re: Grainy Blacks/Shadows in Green Screen Footage
on Apr 15, 2013 at 10:29:41 pm

I'll give one of those a shot and see how it goes. Thanks for the tip!


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