Originally posted by Tommot1965 yes I doubt any of these comparable priced lenses would be as good as the canon 200mmF2..but thats a $6500 lens..so Id be gob smacked if it were..not sure why you put that one in the mix
I think the point I was trying to make was that speed of focusing isn't the be all and end all. I mentioned a lens that I happen to have had a little experience with, which would be my benchmark for a good fast long lens.
So when I say that the DA*50-135mm is fast enough for me, I wanted to stress that it's not because I have not been able to experience faster lenses.
But in my experience, focusing speed does not matter as much as anticipation and timing on the part of the photographer.
Also, in continuous mode, it's the ability to track across shots that matter more than the speed of rotating the lens barrel from one end to another. In this respect, the DA* lens seems to be quite sure-footed and stable, the Sigma I tried seemed more erratic. Maybe the OS version performs better - I was assured that the OS and non OS versions had similar performance but hey anything is possible, maybe I was trying out a dud Sigma unit.
It does make sense to me that Pentax may have tested and fine tuned the K-5 focusing algorithms to match their premium lenses more than 3rd party lenses.