pentax da* 50-135 2.8
I have both the Sigma HSM & the Pentax, they are two very different creatures, The 70-200 is very fast focussing, but no where near as sharp as the Pentax which is fairly pedestrian by comparison....
I you can Keep the Pentax, you wont find a sharper zoom.......an get a Sigma HSM as well....
& yes I do suffer from LBA, but it is nice to have both in the bag....
Andy
A few bits & Bobs
I've had both the Pentax 50-135 and a Sigma 70-200mm F2.8 EX DG OS HSM. The Pentax is a lovely sharp lens but can be pretty slow to auto focus. The Sigma was fast and much more suited to auto sports, especially when turning off the Pentax SR and setting the in lens stabilisation to panning mode. I found my copy of the Sigma pretty sharp and not much behind the 50-135.
reso
Member
worcestershire
k5iis k200d
8mm fisheye sigma 15mm sigma 10-20 3,5 hsm
tamron 17-50 2.8 pentax 18-55 al ii sigma 18-125 hsm tokina 20-35 af tokina 28-70 atx pro ii pentax F 35-105 pentax A 50 1;1;7 pentax 55-300 sigma 70-200 apo ex 2.8
kenko pz af 1.5 tele tamron pz af 2.0 tele and a flash