The "adapter" lenses are usually made to fit a Bay 1. They were made by Rollei, Yashica and Sun (among others). I have the wide one but rarely use it. It seems to work fine, but I never tried making a huge enlargement to really check it out. Up to an 8x10 print they seem to do OK, but I wouldn't push it much further. You will want to stop down a bit, as the maker recommended anyway.