Iain
Just experimenting on this myself now on a short doco of my dads bridge building days from the '40s to '70s.
I've tried my inside interview shots using natural light with subject in middle of living room, curtains open and green screen on a slight angle to dad and about 1 metre back. Too much of an angle and focus up the shoot. This gives a constant light source on green screen that had to be carefully ironed by the way to get out the wrinkles. Made sure there were no shadows from dad on screen. With subject not in the direct light but with green screen in direct light, the results to date appear to work out ok.
All this took several weekends to check out with weather hampering things a bit. Might have been the single malts that we both enjoy as well.
I plan to superimpose photos and old/new video of his bridges in the background and once again tests to date show this to work quite well. I'll be picking my daughters boyfriends brains about this in a couple of weeks when he comes up from Invercargill where he's at movie making school. He's been a great help so far.
When I finalize some of these shots, and if they do turn out as expected, I'll let you know.
Regards from the Naki