I see people are asking about this, or at least Tungsten light tests.
I hope someone with a faster accurate lens can try out some more tests, mine is only with the 18-55mm @ 5.6 and 55mm AWB & JPG. My 17-50 F2.8 is far too out of whack to be used for such a test haha.
I don't know anything about the K-5 issues, or how serious they were etc. I leave these results entirely up to your interpretation
It's dark out so no natural light comparison.
The focus chart is a pretty flimsy bit of printer paper, so some user error could have occured YMMV sue me etc