Chroma key/Green Screen problem

Discussion in 'Professional Video Production' started by yarock, Apr 7, 2005.

  1. yarock

    yarock Guest

    We recently did our first project with green screen. We lit the screen
    correctly, kept the talent 8 feet in front of the screen and lit her
    correctly. We did the editing in Premier 6.5 using some scanned photos
    for background.

    The video looked great and the pictures were good as well. In a couple
    of spots there is still a small amount of green bleeding (the edge of
    her hand, forearm etc.) When we tried to adjust in Premiere the video
    became too transparent.

    We've read and looked at the "Ultra Key" program, which claims to solve
    this problem. Also, we've heard that keying is easier in Premiere Pro.

    Does anyone have experience and know what our best solution would be?

    Thanks in advance,

    Bruce Yarock
     
    yarock, Apr 7, 2005
    #1
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  2. yarock

    Dave Guest

    Important: Did you shoot your green screen footage in DV?
     
    Dave, Apr 7, 2005
    #2
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  3. yarock

    yarock Guest

    Yes, it was shot with a Canon XL2.
     
    yarock, Apr 8, 2005
    #3
  4. yarock

    Dave Guest

    Where could I start. Although I use Premiere Pro 1.5 as my NLE, I've never used it
    to key green/blue footage. I do this in basically only two programs: After Effects
    and Shake. It is my opinion that the stock keyers in Premiere and AE are ok, but far
    from being perfect ... or even very good. Sure you can key the footage, but it will
    probably take what seems to be an eternity of constant tweaking of the matte to get
    it just right. The spill suppressors or ok, but not great

    It is again my opinion that you would be much better off keying you footage in AE (v6
    or v6.5) using KEYLIGHT. Keylight is arguably the best keyer out there. Keylight
    comes stock with AE 6 or higher, and Shake. You can also download it as a plugin for
    AE if you don't already have it. Another fairly good keyer plugin for AE is "ZMatte"
    from Digital Film Tools ... *almost* as good a Keylight.

    Since you're shooting on DV, another problem you'll encounter is that of the infamous
    jagged edges of DV when keying. You might first want to check out:

    http://www.philipwilliams.com/greenscreen.aspx

    This *could" also have a slight effect on how well you are able to suppress the green
    spill. What you generally have to do (indeed, this is what Ultra Key is doing), is
    to blur the color channels, ever so slightly, only of the green screen footage, and
    NOT blur the luminance channel. The reason for this is because the luminance to
    chroma sampling of DV is 4:1:1. In other words, there is only one color sample per
    color channel to every FOUR luminance samples.

    My bottom line suggestion: Use a different keyer OTHER that the stock keyers in
    Premiere 6.5.

    If you're curious about Ultra Key (now, Serious Magic simply refers to it as
    "Ultra"), and how well it works, let me know. you can send me a brief 3 or 4 second
    clip, I'll key it against a background of your choice in Ultra, and send you the
    result. Up to you from there.
     
    Dave, Apr 8, 2005
    #4
  5. yarock wrote...
    One trick is to back-light the talent with a complimentary
    color to neutralize any green that is hitting the foreground
    objects.
     
    Richard Crowley, Apr 8, 2005
    #5
  6. yarock

    Seattle Eric Guest

    Also, you say "8 feet away" -- that's not all that much. Fifteen would
    better, and hit the talent w/complimentary backlight, usually amber.
     
    Seattle Eric, Apr 8, 2005
    #6
  7. "bastard amber" is the spill-killing backlight for BLUE screen. For
    GREEN screen, you would choose a magenta.
     
    nobody special, Apr 9, 2005
    #7
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