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A while back we had a similar problem with a greenscreen shoot. On the field monitor what looked like an even lighting setup on the background turned out to be 3 shades of green when we got to post (the DP had folded up the greenscreen for transport, lots of wrinkles.) At the time we were using Vegas Pro 8’s first version and it could not separate all three ‘greens’ with the built in keyer (did I mention the talent wore a shiny green hard hat and a pastel green coat?) Having worked on other compositing shoots I made sure to light the talent and background with separate lights which saved the day. Fortunately, while the post team was stumped, I ended up using After Effects (5.5) and keyed out each individual shade of green. With some tense moments of trial and error tweaking (AFX has great tools for that) we went from having to reshoot the whole thing to getting acceptable imagery.
Lesson learned: Despite the prior tests to make sure the talent’s colors could be keyed out successfully, a) spill from the shiny hats almost killed us (a slight dusting of talc or cornstarch powder would have knocked out the ‘shinys’, b) though we had the talent moved away from the background to cut down on shadows, moving them farther out would have helped immensely (if you’ve got room use it) and c) wrinkled greenscreens are evil and should be avoided at all costs. Now that we use our own portable collapsable greenscreens I keep a small travel iron with the kit to knock out any trouble spots. Most important, thank the production gods we had a dedicated compositing software program on hand to get the job done. You should never have to rely on a post solution, but it’s good to have one just in case!
Just for the record as an aside, I dropped an original clip into other NLE’s to see how they handled the problem and Avid Xpress Pro, Premire Pro and FCP got smoked. I even tried Ultra CS3 and it couldn’t get rid of the ‘rogue’ colors despite having the tools that says it could. I would have tried Boris FX but I’ve never been able to make heads or tales of that program. So I always make sure we have a copy of AFX around for when ‘weird stuff’ happens.