I own a couple M42 (Pentax Screw Mount) cameras. I've recently begun to shoot Efke 25 in contrasty light and the combination of a low EI (I shoot it at EI 12 in contrasty light) and the use of contrast filters often brings my shutter speeds within that 1/4 sec - 1/30 sec range within which mirror shake can be significant. I've tried a couple things to try to limit susceptibility of the camera to these vibrations, but these are of questionable effectiveness and add weight to my camera bag. I've also tried adding a 4x or 8x ND filter to lower the shutter speed below 1/4 sec, but then I begin to exceed the reciprocity limit of the film and the exposures become sufficiently long that elements of certain subjects don't stay still...
Does anybody know of an M42 mount camera that incorporates mirror lock-up? I do know that a few Pentax Spotmatic samples were modified by Honeywell, USA to incorporate this feature but they are rare and very, very expensive.
A Pentax K-mount camera that can be adapted to fit M42 lenses with no loss of function (e.g. loss of the ability to focus the lens at infinity) would be acceptable - though I would need to know the brand/model of the adapter, too.
This camera or camera/adapter combo would basically be a "one trick pony" (i.e. only used to shoot Efke 25 on a tripod) - so I'm looking for "cheap", rather than "feature-rich"