• Adobe After Effects

  Keylight green screen filter question

  Posted by Matthew Zabel on December 10, 2009 at 3:10 pm

  What does despill bias and alpha bias do in the Keylight filter for green screen? As in depth as you can be would be greatly appreciated.

  Matthew Zabel replied 16 years, 5 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Kevin Camp

  December 10, 2009 at 3:49 pm

  is it finals week? 🙂

  you can download the manual for keylight at here:

  https://www.thefoundry.co.uk/pkg_overview.aspx?ui=A5FB8E97-D752-4E01-AC7D-17B39B7E1192

  but basically you can use the despill bias to set a color to better remove the spill color from… if that makes sense… generally, you’ll often want to set the despill bias to a flesh tone to better remove spill from flesh tones, but you could choose any color from the foreground object that you are keying.

  i’ve never used the alpha bias (well, never unlinked it from the despill bias) but it does the same for creating the key/alpha rather than the despill. you could try that if your key color was removing parts of the foreground object by selecting the color of the foreground object that was getting keyed out (you’d first have to disable the effect or set it to view source, then pick the color, then set the effect back and set the despill bias).

  Kevin Camp
  Senior Designer
  KCPQ, KMYQ & KRCW
• 

  Matthew Zabel

  December 10, 2009 at 5:29 pm

  Thanks, Kevin. Very helpful indeed.

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