Originally posted by Rondec The biggest thing with regard to a f1.4 lens is if your camera doesn't have auto focus adjustment capability for individual lenses, you have to be willing to send it away to be calibrated with the lens. I think you had a pretty good experience with that, Ed, didn't you?
I've owned a variety of lenses with my K-x, but I guess I've been lucky so far because the only one that's needed calibrated has been my Sigma 30mm 1.4. It was consistently front-focusing when I first got it. I sent it to Sigma in NY with my K-x to be calibrated to my body. Sigma serviced it and returned it the same day they received it, so the whole process, including transit time, only took about a week. They tested the lens on my K-x, and adjust the AF software in the lens accordingly. It now focuses perfectly, so I was very impressed with the entire process.
I also included my 50-150mm f/2.8 in the package to Sigma since it needed the firmware updated for live view on the K-x. They upgraded the firmware and tested the focus calibration, but confirmed my experience that it was already spot-on on my K-x.
But focus adjustment is an important advantage of the K-5, especially for users of fast glass. Whatever camera I buy next, one of the criteria will be focus adjustment for individual lenses. But even so, sending my camera/lens off to Sigma was not a painful experience.