Two thoughts have hit me recently:
(1) I was doing something similar to this last set-up but using a slide projector for the backing. Using more slide projectors as spotlights, I was struck by how much light is reflected back onto the screen. Not from any white walls but from just ordinary objects nearby. So those black drapes came to the rescue. (But of course you might wish to intentionally desaturate the image.)
(2) Looking at the photos of my 16mm copying set-up, I think it's about time I tidied up this room ! Maybe I could just spray all the clutter black ?
