I'm spending quite a bit of time now using my 4x5 indoors. I've managed to stay away from flashes so far. More recently, I've been photographing more elaborate interiors and flash now seems like a real possibility maybe even a necessity. I'm thinking about using instant film to help me judge proper exposure when using falsh. My prefered indoor color film is Portra 400NC, but I may decide to use 160NC with flash. I only have small portable strobes (Metz 45 and 40, as well as 2 Nikon speedlights). Not a lot of power but that's all I have I would appreciate advice on materials/procedures/tips for doing this (i.e., using instant film to test exposure), as I've never done this before.