Originally posted by nmcleod1993 So is there really any fix besides just having it in focus at one focal distance?
You could average the adjustment and shoot at f/8 all the time, that way the focus shift will be just enough to keep your subject within the plane of focus. This will be problematic if you shoot distant subjects or close up subjects.
I seem to have been very fortunate with my copy of the Sigma 100-300mm f/4 APO EX DG, even on the K10D - which under normal circumstances, has no option for AF adjustment, it worked fine.
Yes, the lens is very sharp - there is a slight drop in contrast @ 300mm f/4, however stopping down to f/5.6 delivers consistently high performance across the entire focal length range - with one caveat being:
The Sigma lens does experience diminished performance at the minimum focus distance at focal lengths over 100mm, so it is best to use a macro lens for close ups.
Pentax K5IIs - Sigma 100-300mm f/4 APO EX DG - 1/250th ISO 2500 f/5.6 Pentax K10D - Sigma 100-300mm f/4 APO EX DG - ISO 200 1/180th f/4 off camera AF540FGZ + 1/2 CTO Gel used.