I'm a bit confused here. I have been reading that the 645 and the RB67 are both 120 film. BUT I also read that the negative on the 67 is a lot bigger. Sorry if this is a dumb question. But what's the difference if they are both 120? thanks for the clarification. Beyond that, the question in my thread. I'm considering going from digital to medium format. I'd like the best images for the web (build musical instruments). I'm currently using a Nikon D40 and my initial thought was buy a full frame sensor camera. But with a little prompting from my wallet, from Ken Rockwell's site and just flipping through some film scans on the web, I've decided that maybe Medium Format is what I'm looking for. So... for 1600 on the long side sized images with striking quality what do I want? I realize that 645, 67, 4X5 and a bunch of other options are out there. But I don't know where to start. I'd love some experienced advice! thanks, Nick EDIT: after a bit more searching (I guess I wasn't looking in the right places) I think I found the answer. 67 is 6x7cm and 645 is 6x4.5cm. But I still don't get how the film is the same. I guess the frame size and how much is advanced with each film exposure and advance?