Originally posted by reh321 What K-01 lens would not be usable on my KP? It's namely proudly proclaims that the K-01 is a K-mount camera.
The 2012 roadmap included a K-mount lens that could not be used with a mirror, because part of the lens went deep into the mirrorbox. See the top lens shown in this article, labeled "Pentax K-01 lens":
Pentax lens roadmap for 2012 - Photo Rumors
On the roadmap images, it was listed as "DA Wide Zoom". In this article, PentaxForums staff indicated that they believed it would be approximately 10-30mm:
Pentax Publishes Updated Lens Roadmap - Pentax Announcements | PentaxForums.com
But I don't think the lens looks like a zoom, so there could be a disconnect somewhere. I see one knurled ring next the mount that appears to be for grasping the lens when mounting and dismounting it, and another one that appears to be for focusing. But it could be that the mockup was incomplete. It's certainly much smaller than Sigma's 10-20/4.5-5.6.
The lens was obviously meant for the K-01 along with any future mirrorless K-mount bodies. But with the addition of mechanical mirror lockup, I don't see any reason why it wouldn't work with a standard K-mount DSLR, in Live View mode. I think it would require mechanical mirror lockup because otherwise I think the mirror flaps back down if you turn the camera off (or just take it out of Live View mode).
Back in the film SLR days, I believe Nikon had a 220-degree fisheye that went too deep into the mirrorbox to allow the mirror to flap. You had to mount the lens, compose on a tripod, then dismount the lens, lock up the mirror, remount the lens, and finally take your shot.