Originally posted by kodai84 Worked for me, tvcrder (after 3 attempts at repairz failed) I have no doubts that most K-30s are great cameras, but this model does seem to be "prone" to this and if it develops this problem, it's probably not worth paying to fix as it seems difficult to keep fixed.
Just found this thread and thought I'd add my observations with a similar, if not identical problem (cross-posted):
I had a similar issue (intermittent underexposure) with a recent (used old SMC) DA21 mm lens on my K30 (firmware V1.06), but none of my other lenses (DA 50, DA 35, DA 18-138). This effect was largest when shooting at f/3.2. This particular lens had no problems on a K3 and K-S2 tested in a camera store.
After asking and phoning around, I've concluded it is an aperture control problem related to the body but manifested with only that lens:
My K30 (don't know if other K30 do this) closes down the aperture of any mounted lens to its max aperture, then opens the aperture to specified aperture for each shot (very easy to see on my DA 50 f1.8 lens). In contrast, when pressing the optical preview (Fx), the lens stop down to specified aperture without going to f/22.
The K3 and KS-2 tested did not do the "close-all the way, then open" cycle with each shot.
So it appears that in my case, the aperture blades of the DA 21mm tested did not open fast enough after closing all the way, resulting in underexposure due to the shot being taken at wrong aperture.
(Ricoh/Pentax told me I'd have to send it in for repair, but I don't think it's worth it as my other lenses do fine and this body has 28,000+ shutter actuations)