I've done fair bit of green screen work for corporate interviews as a simple way of placing them on an infinite white backdrop.
There are a few things I've learned:
- use a green screen on anything except people with lots of blonde hair. Green gets a much better key than blue because of the way cameras sensors work (they are twice as sensitive to green than blue)
- use a blue screen on people with lots of blonde hair, but add more light to compensate. And if they have flyaway blonde hair, politely introduce them to a hair brush
I once shot a middle aged female CEO with long grey hair that was as wild as anything... she was a lovely eccentric, but damn the I had to work hard in post.
- ask your subject to take 2 steps forward from the screen to avoid casting shadows on it.
- TURN YOUR CAMERAS SHARPNESS CONTROL TO OFF/MINIMUM. This is the best tip I can give. Sharpness adds a black 'edge' to your subject which looks ugly and cheap. You'll get a much better key if this edge isn't there. You can always add sharpness in post if you must.
- If you have the option, record with as much colour information as you can. 4:2:2 material is going give you a better key than 4:2:0. Don't worry if you don't understand this though...its still possible to get a good key with regular 4:2:0 content.
- If you plan on taking any stills from the composite footage, e.g. For a thumbnail image, increase your shutter speed and frame rate....otherwise you'll see bad ghosting and smearing.