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Pick your brains: Portable Green Screen vs Rotoscoping
Hi,
I am planning to film a project in a very flat location but will be adding additional CG elements in the background. I am wondering what typically works better when dealing with the foreground subject, portable greenscreen or Roto, and why? I just want to pick everyone’s brains on this because I really don’t have a whole lot of experience on this.
The way I see it, it’s almost 6’s. With the greenscreen, you’ve gotta replace the BG which requires motion tracking and copy-pasting other elements from your scene into the BG and making it look flush with the rest of the BG. Roto is more tedious for sure, but probably will end up being the same amount of work (since I likely wouldn’t have to roto the entire body of the subject, just a shoulder, head, torso, maybe a foot here and there, whatever).
What are your thoughts? Please, any thoughts on the matter/past experiences you have had either way are greatly appreciated. Thanks!!
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3 Replies
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Answer “c”: motion-controlled camera rig. Best of all worlds.
But if you can’t afford it, then shooting with green screens does most of the roto for you, and lets you mix in physical props and actors that maintain their proper perspective relationships relative to the camera lens.
Roto all by itself is the most tedious way to go, but you’re only punishing the one or two guys in post doing that work, versus the crew and actors on location. I always calculate these kinds of choices based partly on where the time/money is best spent: on the set, or in post. When you can’t afford a lot of on-location set and crew/actor time, you offload more of the work onto the post side, by using green screens and roto. If your post time is short, but access to the live environment is cheap, then you try more “practical” FX.
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Well, I have to say, I’ve done tons of greenscreen work, and tons of rotoscoping. Every single time, without fail, in the middle of rotoscoping I say to myself, “Man, I sure wish I had greenscreened this.”
It really just depends on the scope of the work. If It is just, say, a small part of a body part that moves quickly in front of an object… then rotoscoping is the best way to go.
If it is ANY more than that, I would greenscreen.
Remember, you don’t have to greenscreen everything. If someone, say, waved his hand and that hand needs to pass over a to-be-composited-later object, then you really only need a small insert green screen the size and position of the object that is to be covered. You’d want to, of course, shoot a same-exact-position clean background plate to fill in the composite.
Bottom line, you can do it either way. Personally, if it were only a little bit, I’d probably roto. More than that, I would greenscreen or do a combination of both techniques.
T2
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Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com
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Seth, this is a case where a test is in order. Find out how long it takes to roto five seconds of representative footage, then figure out how many seconds you’ll need to do for real. If the foreground will have a lot of action or non-linear motion, then your test should too, because that’s where the hard work happens with rotoscoping. And shoot your test as if it were in front of a chroma key screen, i.e. use a higher shutter speed to avoid motion blur.
I’d vote for green screen, if you have the time, equipment, and knowledge. Even with a perfect backdrop, I still sometimes have to roto a tiny bit here and there. I can’t imagine doing entire scenes in rotoscope.
Bob C
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