Over a few decades of film photography, I've managed to avoid Leica. I used a friend's M3 for a while and it was nice, but didn't set my photographic world alight. Now I think there may be space for a screw thread Leica with a collapsible lens to use as a pocket camera. The problem I have is finding a suitable lens that isn't scratched, fogged, or absurdly expensive. I'm only vaguely aware of the options, can someone fill in the details? Possibly including a fixed lens.