I've recently finished shooting rehearsals and performances by Jazz & Ballet Companies of their Christmas. Posted a couple thousand photos. Rehearsals when I'm close, I use a DA12-24 and a Tamron 28-75 on my two K-5 bodies. Performances, stuck in back of the house, DA 50-125/2.8 & Sigma 100-300/4. Shot all AF with Single Point and Single Focus using AF button rear to follow. Have callous on thumb. I've never adjusted any lens on any body and if I had couldn''t keep track in the dark.
I threw away a lot of exposures but only a small amount due to missed focus. You can see the results here:
Downloads and Prints | Brooke Meyer
The older galleries were done with K-20s. With K-5s, I start shooting at ISO 3200. My most typical exposure ( I shoot manual) is f4 at 1/320, ISO 3200. If needed go to 6400 or 12,800, especially for the Jazz company. I've probably got 45K exposures on 1 body & 20K on the other. One was bought new last Jan at B&H and one was an Amazon open box return. Current firmware. Long range, the 50-135 is wonderful. The Sigma is tougher but when you nail it, its very good. Close up the Tamron 28-75 and DA 12-24 just work very well. I've been doing this for awhile with plays and other types of dance. If there is a design issue with Pentax AF in low light on stage aka Tungsten, I can't find it.