Originally posted by manufocus do I guess correctly that the aperture won't be controlled with the camera anymore? This would mean that the viewfinder would accurately show DOF, however I think that this could become an issue for focussing since the area of "sharpness" will be longer making it more difficult to land the desired object in the "middle" of the sharpness zone.
Correct, this is the same as m42 with A/M switch in M position.... you do the aperture, not the camera. And because of this, metering is done when the shutter is released. Also, as you pointed out, the focussing will be harder as you stopped down the aperture since the viewfinder is darker. With the m42 lens, you can simply flip the A/M switch to keep it wide-open while you are focusing and push to M position when you are ready to trip the shutter. With the k-mount lens (no aperture), you can turn the aperture wide-open when you are focusing and then 'count' to the desired stop before tripping the shutter. In general, if you seldom go above f4.5, it won't matter.