Some older pre-set lenses have the same optical design as the auto diaphragm lenses which were made at the same time or later. One of my favorite old lenses is the Vivitar 28/2.5 Fixed Mount. I have auto diaphragm versions in every mount I am aware of. I also have a pre-set model somewhere which has a Canon mount adapter on it. It is as good as all of the Fixed Mount examples I have. I am looking for pre-set lenses I have around to use on a Konica FS which was serviced last year. The old F mount Hexanons are not very plentiful and are sometimes expensive. The pre-set lenses can supplement the 50/2 F mount Hexanon I already have. I have an Exakta to F mount adapter so I can put a Viviter or Soligor T4 lens with an Exakta adapter on for one lens. I would like to find an M42 to Konica F adapter for a reasonable price because I have plenty of nice Takumars, SMCT and SMC M42 lenses.