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Thread: chroma keying two colors

  1. #1

    Default chroma keying two colors

    Hi, I set up a green screen and with markers on it that are a slightly lighter green than the majority of the green screen. I'm doing this so that another program (Labview) can track/measure the motion of the camera via the motion of the lighter green markers.

    My question is what is the best way to chroma key out both of these shades of green? I tried putting two chroma keyers in the filter chain, but after going through the first chroma key filter, say for the majority green shade, the other green shade, the markers in this case, loose a lot of color, making it potentially closer to object colors in the foreground and hence the second chroma keyer struggles.

    There must be a better way to do this.

  2. #2


    Using two key effects is normally no different to relaxing the tolerance using one key effect. If you try to take out both shades of green with a single key and one of those shades is too close to colours in your subject then a second key effect is going to have the same effect.

    Hypothetically, if your screen is perfect and has the exact same colour pixel for pixel and your markers are the same, but for their lighter shade. A single key effect for each with zero tolerance would allow you to have a shade of green in-between in your foreground. But this isn't really a real world scenario. If you use a single effect and set the screen colour to halfway between the darkest area of the screen and the lightest area of the markers you will get the best results you can get.

    But it all depends on what you are using to key out the background. "Keylight" has some excellent tools that let you replace colours in the foreground layer that have been taken out along with the background layer. What you want is a keying tool (such as keylight) that lets you examine and make adjustments to the matte.

    Sorry I can't help you regarding what is available for Vegas in this regard.


  3. #3
    Join Date
    Mar 2011
    London, England


    Maybe no help if the "job's done" but could you not make these secodary markers closer in colour, or make small cones that have a slight shadow - What happens for example if you stick 3M "Magic" tape over the Chroma - it should be the same colour, but different....dunno.

    Is'nt what you are doing a common-enough Application?

    -I'll get my coat...

  4. #4

    Default Thanks for the suggestions

    I managed to get the lighter green markers to turn to the green screen green using the secondary color corrector in sony vegas, to then do a single chroma key. Thanks for the suggestions.

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