Originally posted by xmeda Yes Pentax bodies have problems focusing anything faster than F2.8... and F1.8 zoom is hell on earth for pentax SAFOX. Thats all. Contrast detect nails them.
Sig 17-50/2.8 might be "old" or whatever, but still optically superior to DA*16-50/2.8.
You're stating your opinion as fact. With respect, it is anything but. I take you at your word that
you have had problems with AF, however...
All of the Pentax (and Samsung rebranded) bodies I own - *ist DL, GX-1L, K10D, GX-10, K-5, K-3 and K-3II - focus well with my faster lenses. The focusing is very reliable - by which I mean there are very few misses, and no more than with my other slower lenses.
I seem to recall you once mentioning you had problems with AF on your FA50/1.4 (if I've mis-attributed this to you, my apologies). I've never had a problem with my copy of the FA50/1.4 on any of my Pentax / Samsung bodies.
There are, however, numerous people who've had problems with Sigma AF lenses on Pentax bodies, the 18-35 f/1.8 being especially unreliable. Indeed, Canon folks experienced these same problems (there's plenty of evidence on the web about this), but Sigma released a firmware update for their EF mount lenses that greatly improved the AF performance. Sadly, no such update was ever provided for K-mount...