Originally posted by monochrome This (no Green Button metering in LiveView for Takumar lenses) is a well-documented condition, begining with the K-01. It has to do with the paint on the Takumar lens mount failing to short the contacts on the camera. There are kludge work arounds such as using bits of foil stick to the lens - apparently Pentax is in no hurry to correct this in a FW update.
Bayonet mount lenses do not exhibit this behavior, presumably because the mounts are not painted.
Getting back to the original topic (sort of, since I can only comment on the K-01), just repeating that my K-01 green button sets the shutter speed just fine with m42 lenses (or even no lens at all) in M mode. (ISO must be fixed.)