I'm posting this in a couple of relevant forums, since this is a question that could be answered from both a production and post production point of view. :)
I've done a fair bit of green screen shooting in the past, but in a few weeks I'm going to be trying something new, at least new to me.
I'm going to be shooting an actor wearing a green suit. Not to get into too many unecessary details but the actor will be interacting with objects and other actors. Sort of an invisible man kind of effect. Example: lifting a mug from the table in front of an actor.
So my plan is to shoot a clean background plate of the set (or in some cases shoot the other actors with the background set) then shoot our "green man" on the set doing his actions. Then key out the green suit in post.
What I'm wondering is whether it'd be easier/cleaner to shoot the "green man" against a green screen. I was thinking that if the objects and actors he's interacting with are actually on set the effect will look more realistic when composited. Rather than trying to make them appear to be in the scene, they ARE in the scene.
But then again, lighting will be very important and it might be hard to light a scene on set that will also give me clean keys on the "green man".
I wouldn't count on the green keying super well due to the shading it will have on it. However, it could help immensely for some shots. Shoot a few tests.
When planning your shot, think "Could I rotoscope this shot if needed?" and try to keep that answer to a "yes".
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I worked on a project with puppeteers in green using puppets against a green screen. I was actually hired to help clean it up because even though it was lit about as well as could be, shadows created under the puppeteers arms etc, made a ton of artifacts. This was a long time ago, and keyers have gotten better since then, but I'd still expect a lot of roto cleanup.
Another thing to keep in mind, not only were there keying artifacts, there were many places where a puppeteer's green stick or arm crossed in front of a puppet and erased some of the puppet. The erased portions of the puppet needed to be very carefully clone painted back in. Given what you are doing, I would recommend shooting the green man against a green screen. If the man is potentially moving in front of other actors, or moving objects in front of actors as you describe, you will want him as isolated. That should help keep any clone painting to a minimum. You could maybe compromise and set up a portable green screen on set behind the place that he will be interacting with things.