An indispensable part of my quiver of glass ... and at a very good price.
Incredibly sharp with my Pentax 300mm tele-zoom lens.
Super convenient for extending my Pentax 100mm macro to allow a bit of air between subject and lens when doing live ultra-close macro work. I would never get rid of it.

Anyone know if such an adapter exists or is available? This lens produces brilliant photos (with plenty of interesting tonal variations) on my old Leica 3G and would be interesting to try on my K3 as a portrait lens.