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Old April 27th, 2005, 04:37 PM   #1
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Blue or Green Screen ?

Hi Everyone,

I am about to delve into an extensive star wars fan film with a colleague. I have an XL1s and Premiere pro / After Effects at my disposal. My questions are which screen is better, Blue or Green and is there an optimum setting for the camera ie fps, soft focus etc to ensure a good key.

I`ll say "Many Thanks for your help" now, because I know I`m gonna get some help here :-)

Andy
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Old April 27th, 2005, 05:31 PM   #2
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Quote:
Originally Posted by Andrew Paul
Hi Everyone,

I am about to delve into an extensive star wars fan film with a colleague. I have an XL1s and Premiere pro / After Effects at my disposal. My questions are which screen is better, Blue or Green and is there an optimum setting for the camera ie fps, soft focus etc to ensure a good key.

I`ll say "Many Thanks for your help" now, because I know I`m gonna get some help here :-)

Andy

Shooting on DV, as long as there's nothing too green in the shot, you're better off going with greenscreen. You'll generally pull better keys with green.
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Old April 27th, 2005, 10:50 PM   #3
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green is best for dv ..
shoot some TEST .. the wider the shot the harder the keying .. try backing off the sharpness a little on the XL to get rid of the electronic edge that is going to be chroma key enemy #1 ...
also when you're having problems keying - try pulling a luma key in AE and combine it with the chroma key matt ( ?? 60% chroma matte - 40% luma matte ) ..

you may have to use Primatte keyer ( 3rd party plug in ) - download the demo ...
i use combustion 4 ( with diamond keyer) & primatte plug in.. i also have Ultra .. using a hand size camera with 1/3" CCd's shooting in 4:1:1 color space you are going to have very difficult hours/days keying .. IMO save yourself headaches , time and shoot with camera/format that is 4:2:2 color space ...

again do some TEST in preproduction
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Old April 28th, 2005, 07:39 AM   #4
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Haven't had a chance to try this myself, but I recently read about a trick that sounds very interesting. If your green screen subject can be framed with the camera tilted 90 degrees ("on its side"), then after keying you can rotate the keyed image to keep the subject upright in the timeline, and shrink the clip to fit on the background. It would be a lot of CPU effort, but you should in theory have a much nicer looking key.

That's because the lower chroma resolution in the keyed layer will end up being vertical, which tends to catch the eye less than chroma bleed in the horizontal, AND because you've reduced the size of the 720px tall keyed frame to fit into the 480px high background.

If anyone has tried this, would be eager to hear about it. Just seems like it should give a much cleaner key but I probably won't get the time to try it until at least this weekend, and probably not then.
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Old April 28th, 2005, 02:04 PM   #5
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Here's a link that might help a bit-> Selecting Greenscreen or Bluescreen Essay

Most important is contrast between your subject and screen. Bright subjects will be easier to key with a blue background. Dark subjects work better against green.

Next is lighting. The screen should be as evenly lit as possible. Big diffuse lights. NOT halogen work lights. Keep shadows off the screen. Positioning a fill light on set to kill the shadows is a lot less headache than trying to clean them in post.

Shoot as clear as possible, don't softfocus. You can do this in post if you feel it will help. Even better, in post you could blur a single color channel if that's what's giving you trouble, leaving the others in focus to keep image clarity.

Tilting the camera on it's side seems like a lot of trouble for very little (if any) return. Also this would be a real mess if the final video is to be shown interlaced for TV.

Have fun.
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