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XL2 Settings for Blue Screen


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#1 Theo Lipfert

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Posted 25 May 2005 - 10:02 PM

I am shooting some blue-screen interviews with an XL2 and the Reflectmedia light-ring blue screen. In my tests, the light ring produces a nice, even blue (bouncing off their special material) but when keying I get some horrendous aliasing on my test subjects' ears and shoulders. I know that DV 4:1:1 is problematic -- but does anyone have any suggestions for getting usable results? Turn down sharpness? Use Ultimatte Advant-edge?

All suggestions welcome.

Theo
Bozeman, MT
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#2 drew_town

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Posted 25 May 2005 - 11:00 PM

What program are you using to key? After Effects has a nice keyer and there's some addtional plugin keyers you can buy if you need them. The keyer in FCP isn't all that great. Hair is one of the hardest things to key.

Something that might make a little difference would be to convert your dv footage to uncompressed.
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#3 Theo Lipfert

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Posted 26 May 2005 - 07:26 AM

Re: AE or Final Cut --

I can use either AE or Final Cut. I have experimented with Key Light in AE, but still get really crunchy, blocky aliasing around people's heads. I guess my question is really whether there are settings on the XL2 that will help minimize problems with keying.

Thanks for the suggestion about working with uncompressed footage -- I will test that as well.

--Theo
Bozeman, MT
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#4 Jay Gladwell

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Posted 27 May 2005 - 06:55 AM

Proper lighting of both the green screen and the subject will play the single biggest role in getting good keying.

Light both seperately. Light the screen evenly. Make sure the subject does not have any bounced light from the green screen falling on it--the more distance between the subject and the screen the better. Having good rim lighting on the subject can help resolve this in tight situations.

Jay
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#5 David Cox

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Posted 27 May 2005 - 07:59 AM

Hello,

The aliasing you are seeing is most probably a combination of the DV compression (the resolution of the colour part of the signal is effectively lower than the resolution of the lumience part, so your blue screen isaliasy) and the settings in your keyer.

In your keyer, make sure that the tolerance of the key (the number of shades of blue it keys) is as wide as possible. Having this too tight will crunch the edges. Also blur your matte a little to soften off the aliased edges.

David Cox
Baraka Post Production
www.baraka.co.uk
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#6 Landon D. Parks

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Posted 30 May 2005 - 05:07 PM

I once lighted an interview scene for the local community access television for an interview they did. I did not key it in post, but I did light the chroma-screen (Blue in our case), and after some test's, I found the following worked fairly good:

Posted Image


It may not be the proper way to light it, but this was several years ago and I was working on the lighting for this as a volunteer job I had at the CATS studios. This was the first and last Chroma Job I shot for the studio.

PS) I seen the finnished version of the scene, and to tell you the truth it looked good. so they either done magic in post to fix my mistakes or I actually lit it well enough that it came out good and clean. Although having been shot on 16mm probly helped out the keying a bit more than shooting with DV compression. I lit it so that there was NO shadows on the subject, and where the shadow of the subject would not project onto the Bluescreen. Countered by the lights behind the subject lighting the bluescreen.

I don't know if this will help you or not, but it's worth a shot.

PS) I may be able to get ahold of a digital copy of what I shot and how it turned out. I'll talk to the head of production in a few days to see if they still have it, and if I can use a segment of it.

Edited by Landon D. Parks, 30 May 2005 - 05:11 PM.

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#7 Andy Joyce

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Posted 15 July 2005 - 07:06 PM

I am shooting some blue-screen interviews with an XL2 and the Reflectmedia light-ring blue screen. In my tests, the light ring produces a nice, even blue (bouncing off their special material) but when keying I get some horrendous aliasing on my test subjects' ears and shoulders. I know that DV 4:1:1 is problematic -- but does anyone have any suggestions for getting usable results? Turn down sharpness? Use Ultimatte Advant-edge?

All suggestions welcome.

Theo
Bozeman, MT

<{POST_SNAPBACK}>


I tried that screen in a store demo, and if you zoom in on the edge of the subject, it is not a perfect key. The illumination is perfect, but the edges around the subject were questionable, even if you turn up the rig lite all of the way.
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#8 David Grantham

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Posted 14 August 2006 - 12:06 AM

I am shooting some blue-screen interviews with an XL2 and the Reflectmedia light-ring blue screen. In my tests, the light ring produces a nice, even blue (bouncing off their special material) but when keying I get some horrendous aliasing on my test subjects' ears and shoulders. I know that DV 4:1:1 is problematic -- but does anyone have any suggestions for getting usable results? Turn down sharpness? Use Ultimatte Advant-edge?

All suggestions welcome.

Theo
Bozeman, MT



I'm told that if you use a "Chroma blur" effect it'll blur the colour data ( R and B ) without blurring the image (because the luminance channel is unblurred) thus reducing aliasing when keying. Aparrently this is specifically what that effect is for. Mirage has one. Don't know about AE.

(Makes for a lovely hand coloured effect also.)>

Edited by dgrantham, 14 August 2006 - 12:07 AM.

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#9 AshG

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Posted 18 August 2006 - 02:04 AM

Try turning down the sharpness a bit and turning up the corring a little. Also, you might try setting the vertical detail to low. Video does not like BLUE, it is overly sharp and can be noisy because of that.



ash =o)
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