I bought this lens on the cheap online. Upon arrival I noticed that the aperture was not working. I have zero familiarity with PK mount lenses so I fiddled and fiddled and apparently made the situation worse, as the click aperture ring became click less. Disassembly was a logical next step - I said I bought this on the cheap, right? In the course of fixing whatever was wrong (I can't tell if something in the iris engagement assembly was hitched, or if the blades themselves were too gummy to open (they look super gummy)) but after more fiddling, with the lens mount disassembled, I was able to engage the iris to open and close either by manually flicking the little tab in there, or when I put the aperture ring back onto its tab by moving it open/close. Ok, then I saw the very tiny ball bearing that accounted for the click and figured that I had bent its housing a little too far down and thus my click less aperture. Fixed that. Finally, I saw the restraining post for the iris and noticed that while it was inserted in a spot to hold the lens at F22 there was room to move it back and close the lens down even further. So, and I said on the cheap already right?, I unscrewed the post and moved it back. Here's my question: did I do what i think i did and allow this lens to stop down even further? Is there any way to figure out what stop it might be at? The iris definitely closes down tighter, so I think I'm in the right ballpark. The picture shows the original travel that went from 5.6 to 22. I know just enough to be dangerously stupid; can any of you think of any repercussions to the lens for doing this? On reassembly, I noticed that a wide metal ring with a tab was left out. The lens works fine, and I figure that particular ring had something integral to do with the Pentax shutter action and zero to do with me using the lens on my Em5.