I have the potential to succumb to LBA (Lens Buying Addiction, as coined by the on-line Pentax community). Since getting such fantastic results with the f1.4 50mm I have had all these years, I hankered for something fast and sharp in a longer focal length. I have just received a Tamron 135mm f2.8, it is the second I won on eBay. The first was mixed up by the seller and sounds like the receiver took advantage of the error. I got a Canon SLR instead (sent it on to the intended buyer). The Tamron I won this time is the old BBAR version so is from the late 1970s I think. 5-10 years older than the other, but it looks clean enough where it counts and seems to be working fine. It meters in Av mode with my PKA Adaptall 2 adapter, although I think this is the older Adaptall. It does not seem to stop down to f22 properly, but this is down to the mechanical stop down lever and could be fixed. So far, the few photos I have taken with it look sharp enough (see crop attached), so it could be a keeper.