Originally posted by Edgar_in_Indy Those were kind of my thoughts too, but it seems like the OP is convinced it's the lens. Whether the problem is with the lens or not, the full disclosure is commendable.
Maybe it really is just a case of this lens did not play well with my K5iis but plays slightly better with my K3. Maybe it will play well with someone else's K3. If that's the case, then someone is getting a steal on a great lens.
Originally I was so fed up with my K5iis AF when paired with this lens that I was on the verge of switching systems. I started reading reviews about the improvement of the K3 AF so I gave Pentax one last opportunity. I still am not thrilled with the AF performance, but it is tolerable, mainly because I don't have enough cash reserve at the moment where switching systems could become an option.
Once I acquired a K3, I spent an entire Saturday aiming at test targets in my back yard and across the house, because I needed some closure on the whole "is it the lens or does the Pentax AF really suck that badly?" That's where I figured out the goofy adjustments needed that I relayed in my referenced post. Then it was revealed that some of the earlier version so this lens do suffer from inherent BF issues and it made sense. It still doesn't completely absolve Pentax of sub-par AF, but it's enough for now to keep me.
It's probably a case of a little bit of lens and a little bit of my camera makes for a bad pairing, but I'm not about to go out and purchase several bodies to test that theory. And I know it's not a technique issue because I used to shoot a Bigma and get very good results from it, but it weighed 2x what the 100-300 weighs and literally would take 2-3 miles off doable hikes because of the weight.
Given my shooting partner is a wildlife shooter, I spend a lot of time chasing critters, and need a lens for the task.
I really hope whoever purchases this lens has no issues, but I couldn't
not relay the reservations I have about it since I don't have the ability to send the lens in for servicing to find out for certain. I really have no desire to ship a lens of this type and then have it returned, it's just not healthy for the lens no matter how well you pack it.
What surprises me is that I've had not even a single nibble, maybe I'll end up after all this with a Sigma paperweight.