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After a few videos, I think that now I manage pretty well chroma key on a green screen.

But in my last video, my subject handles items that are light blue / cyan, and I started to notice that those items shift color and become an unnatural blue, it looks like contrast has been pushed A LOT after applying the chroma key effect, I never noticed that before (probably because this color is quite greenish).

But this is not how I thought chroma key was working. I thought it was just removing the parts of the video that was matching the selected color (+some margin) and not touch the other parts/colors of the video.

And indeed, testing it with several other tools (Adobe After Effects, Lightworks, and the NewBlueFX chroma key plugin), it does exactly what I expect : remove the background and doesn't touch the colors that doesn't match. Only the default chroma key plugin seem to do that.

Is it a bug in the chroma key plugin (that seem to exist at least on version 12 and 13) ? (but it would be surprising as I guess a lot of people would be affected)

Is it a bug with my installation ? (keeping in mind that uninstalling Vegas 12 and installing Vegas 13 didn't fix it)

Is it some parameter or something I forgot somewhere that would affect the chroma key plugin ?

Update : Here is small parts of the video, with different effects applied :

  • The raw image
  • The best I can do with the NewBlueFX Chroma Key plugin
  • The best I can do with the default Vegas Chroma Key plugin (pretty ugly...)

Chroma Key demo

Vegas Settings :
Vegas settings

NewBlue Settings :
NewBlue settings

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This might be an issue with the Vegas chroma key program removing green from all objects and making it transparent rather than finding only solid green and modifying that.

Someone may know how to fix this in Vegas, but if all else fails you can run your keyed footage through a program like Davinci Resolve Lite (free) and correct the colors.

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I would guess that it is trying to correct for green highlights in the chromakeyed video and overdoing it. It's relatively common for green screen footage to have greenish reflections due to light bouncing off the green wall back on to subjects. The chroma-key effect may be attempting to automatically correct this and catching objects that have no such reflections in the crossfire. I would expect it to be a setting that can be turned on and off, but I'm not familiar enough with Vegas to take a guess as to what it might be called there.

Possibly something like "bleed prevention" or "reflection correction", but those are just guesses.

  • I don't think it's that. It already occured to me on one of my first attempts at chroma key, and it only made the green parts transparent, it didn't change the color of the "not keyed" parts. – Julien N Jan 8 '15 at 16:22
  • Can you post a screen shot of the green screen settings you are using that also shows the color change you are experiencing? That would help a lot with figuring it out. I tried to find documentation on Sony's site, but it was less than helpful. – AJ Henderson Jan 8 '15 at 16:24
  • I added a screenshot (the image is bigger, I expected the site to open a popup... please use open image as new tab). As you see, the blue color become awful (in my mind it was more purple, but it's still ugly). There is a bit of green reflection but other tools handle it pretty well (it disappears with the keying and the blue is slightly darker but it looks okay, nothing like what Vegas' plugin does). – Julien N Jan 8 '15 at 19:16
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Ok, I know it won't help you much now after 4,5 years, but i found roundabout for those still looking. Set up color corrector (secondary) with hue rotation 180, then chroma keyer, then color corrector (secondary) with hue rotation 180 again. It's not perfect as you'll have to play around with the slider, but at least you won't have to switch/download other programs.

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