I've had some 120 film sitting around for a while as a result of a messed-up order from an online shop. I've been itching to actually do something with it, and I've finally decided that now that my final semester of grad school has begun and my daughter has been moving around on her own, it's a PERFECT time to hide and build my own medium format camera. I don't mean this to be a general-purpose machine, but largely for macro and/or environmental portraits (I'm willing to concentrate on one or the other, both don't have to work). The salient point out of that is that I'm unconcerned about focus beyond about, say, 6 to 8 meters max no matter what direction I go. Now. I'm interested in using materials I have sitting around as much as possible so lenses intended for 35mm (135) SLRs are attractive. Now, obviously, if I just push, say, a 50mm focal length 135 lens away from the film plane it will eventually cover a 6x6 frame with reduced light intensity--and corollary effect on f-ratio. Depending on the lens some won't even have to be pushed that far... image circles vary pretty widely. Depending on the particular lens, focus range will be impacted and I'll have to make decisions to emphasize closer or farther focusing. All of that I can live with for my intended uses. The unknowns, however, are many. I'm a software guy, not an optics guy. I've taken physics and chemistry and a few semesters of calc... I'm not dumb, but I'm mostly ignorant of optics beyond the intro (Newton) stuff you get in general science courses. And whatever I've picked up from being a photo enthusiast. So what other effects might I expect in this scenario? In case anyone has knowledge of specific lenses, the most likely candidates for this would be 55/1.8 Takumar and Vivitar 135/2.8 (as I have dupes of each laying around that were tossed in with parts bodies). If this is a really unsuitable use I'll probably scavenge a lens from an old folder. But I'd like to see what I can do with this first.