Thanks for the comments, and thank you DCshooter for the kind offer. I do live in DC, but am not there right now. All the glass and blades are clean, and the focusing ring works smoothly. Note that the blurriness occurs with both auto and manual focus, and that I do get the focus confirmation blinky.
I am attaching a very artful shot taken out of an open window this afternoon. Lens was attached to a K100D (on which it behaved normally a couple of years ago), but the same problem occurs with a K20D. My Pentax gear is not quite up date to date, as you can see. Thanks in advance for any thoughts.
---------- Post added 02-16-2017 at 05:15 PM ----------
I just noticed that the EXIF for this shot says f/1.4. But, the lens aperture ring was set at f/8. Might this give some hint?