I'm preparing to construct an exposure unit to make ziatype and platinum/palladium prints. As I've got this drawn out right now, the distance between the bottom of the BLB bulbs and the surface of the negative/paper sandwich when exposing would be 2 1/2 to 3 inches. Is this too close? What are the consequences, if any, of having the lights too close for exposure? Finally, if this is too close, what is the recommended distance range?