I've been using contax I for a while now. I had a problem rewinding film the first time I used it. I had to unload in the darkroom. I had not had a problem since. Two prongs push the film away from the spool while rewinding. A funny system for rewinding. I have a f2.8 tessar perfect shape and f1.5 sonar also perfect shape both nickel plated and uncoated The tessar preformed much better with a lens hood. Camera works well.