There was also a 28. I have the 135/2.5. No one seeme to like it. When it's stopped down a little it looks fine. I would like to find a 135/2.5 SMC Pentax. There probably weren't very many made before the change to the M lenses. Luckily I have a 135/3.5 M lens and that seems sharp at all apertures. I can also use an older 135/2.5 Super Takumar with an adapter. Nikon had the E lenses, Konica had the Hexars, Yashica had the Yashikors, Minolta had the Celtics and Asahi had the Takumar Bayonets. They were trying to compete with Vivitar, Soligor, Sigma etc. Some of these less expensive lenses were identical optically to their more expensive counterparts and some were not. Not long ago many people wouldn't consider the less expensive models but the Pentax DSLRs and the MILC cameras gave sparked interest in the more exensive lenses and both kinds have gone up in price.