Then you should be looking at A series lenses:
Pentax Lens Review Database - Pentax A Series Prime Lens Reviews and Specifications
And equivalent (Pentax A fit, A contact, aperture ring A position) third party ones if your not after Pentax only.
SMC Pentax-A 28mm f/2.8 might be good choice, but not the best one.
Since M series provide only partial exposure metering automation and it is with error as well.
So what about the requirements? Speed. At f3.5+ i think kit lens is already plenty good in this focal length. Or are you after a compact size?
Last edited by ytterbium; 08-01-2010 at 08:52 AM.