Quote Originally Posted by Bob Carnie View Post
I have 36 inch of workable bellows ... I am using an old century camera with no shutter, its light tight as I have gone through a few boxes of film as late as last sunday.
Well, the magic rule is: extension (distance from lens' rear node to film plane) = focal length * (1 + magnification). So the longest lens you can use is 9" and a bit shorter would probably be better. For most lenses, the rear node is near the diaphragm.

There's another magic rule, to the effect that if the lens is intended to be used at magnifications below 1:1 (that's all taking and enlarging lenses) it should be reversed when used at magnifications > 1:1. The big exceptions are symmetrical (with identical front and rear cells) lenses; this includes Apo-Saphirs (heliar type), some, perhaps not all, dagor types and most if not all dialyte type process lenses.

Good luck, have fun,

Dan