Originally posted by StefanMikes Does it. An APS-C lens? In the FF or Crop mode?
FF mode.
If you've been following the forum, this has been known for a long time.
Pretty much all the DA primes from 35mm up to 300mm work well with FF. Part of the reason is that many actually have heritage in Pentax's older film designs.
Zooms and wider primes are less successful, although you can pick your focal lengths. The DA12-24 I find is great from about 17mm on, for example. Others find that if you remove an internal baffle, the DA*60-250 is very handy, too.
Of course, you can shoot a great DA zoom or wide prime in crop mode too ... I've done that with the DA*50-135 for its fantastic rendering.