Originally posted by robgo2 At this point, I am unsure about trying another K-5 in about a month or waiting for its successor. Who knows when that might be released and what bugs it might have? Although I am feeling frustrated, I do recognize that my current kit can produce stellar results.
I hear you, this is frustrating.
If I were you, I'd try a focus chart (instead of the LensAlign) and perhaps different lighting conditions (unless you are using bright daylight already) just to see whether it makes a difference.
Seems hard to believe that you only got dud 55's, given that you tried different vendors, but maybe there was a large batch of them which are lacking somehow?
Originally posted by robgo2 That is the reverse of what I experienced, but it does reveal a defect in the AF/lens interface.
The Sigma 100-300/4 has a great reputation among Pentaxians. I reckon Peter got a copy with an optical defect or a lens chip problem.