I have been using the Pentax DA 17-70mm f/4 SDM for a few years.
Most of my shooting is done in TAV mode, and I find the 17-70 covering nearly all requirements. The only other lens I have is a (something like 50-200) dirt cheap Pentax one which gets used once a year. (A lot has changed since carrying an OM2SP, later OM4Ti, 5 lenses and 25 rolls of Kodachrome 25
and I am not sorry).
It works great, of course, but sometimes cannot focus properly. Also I *feel* that the K3 should be a lot sharper than I am getting. Mostly I shoot at F8 which according to reviews is optimal for most of these lenses.
I may be missing something but the only other *Pentax* option is a very similar WR lens. Not worth changing for that one!
What is the very best quality lens in the 17-70 sort of range, regardless of price, which will fully work with the K3?