Originally posted by Pepe Guitarra I have a bunch of those adapters with flange that Asian dealers sell for $8 each. Those can be installed on the lens and you can treat them as regular K mount. The only draw buck is the focus to infinite that gets compromised. If you do not mind not being able to focus to infinite, then there you go.
The safe wide-flange NIF (no infinity focus) adapters have less effect on far-focus on LONG lenses, like 200mm or more. Far-focus may be somewhere around 75m, which for many tele applications is just fine. My TeleTak 200/5.6 and Argus-Chinon 300/5.6 live with NIF adapters.
My favorite 'portrait' zoom is an M42 Sears-Tokina 55-135/3.5. On an NIF adapter, far-focus at 55mm is ~3m, and at 135mm is ~20m. Near-focus drops to 0.75m at 55mm and 1m at 135mm, and DOF thins a little. Those are damn useful focus ranges, so an NIF adapter lives on that lens.
Far-focus on a 35mm lens may drop down to 2m, which is more limiting. On a 21mm lens, it gets rather absurd. And on a 12mm fisheye? HA! It's down around macro range...
I think I read that the upcoming Pentax accessories price gouge, er I mean necessary increase, will include the Official Pentax M42-PK adapter. Y'all who want to turn your PK dSLRs into M42 cams had better stock up now. The rest of us with multiple M42's that we swap regularly can keep buying cheap clones.