Hi all, I'm preparing for a 10-20 image series that requires a moderate amount of setup and postwork, some of which I haven't done before, and just wanted to know if any of you see any problems with my planning. Simply put, I need to photograph people and place them into synthetic environments with cg elements. I plan to photograph the subjects against a neutral gray backdrop, either outside in the sunlight, or with 5,000-5,500 K lamps (unless the rendered background is going to be in shade). Lighting of virtual sets will be handled using HDRI probes. All distances and camera settings will be recorded.
Really the only thing I'm not sure about is if the lighting will be strong enough to cover the whole set (about 20x10 feet) without fading. Does anyone else have any experience with this?

I'm not sure the choice of a neutral grey background is a good one. 
Neutral grey is the same luminosity as human skin and could give you selection problems.

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html

I'm doing all my masking manually, without the magic wand tools or anything like that. Since there's going to be a lot of different light intensities between shots, and even within shots, I felt a neutral color would help balance it out a bit, so I don't have to deal so much with glowing edges as with a white background. Does that make sense?

Yes it does.
All sounds good to me :)

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html