I didn't do anything to the focus adjustment. I did shave a bit off the M42 to EOS adapter so the flange is just below the rear element at infinity. I got infinity without problem and there is no mirror issue. As a matter of fact I can focus beyond infinity right now.
The infinity shot is at f1.2 also.
The 100% crop shows the power lines that I focused on.
Not bad, looks a lot like my Pentax 50/1.2. How're the out of focus highlights at large apertures? my pentax gives rings to gaps in leaves etc, but is ok with totally point light sources.
Slide the aperture ring back against the adapter to prevent light leakage. To fine tune infinite focus just remove the rubber focus grip then pull the tape loose. With the tape off mount the lens and set infinite focus then re-tape and put the grip band back on.
Thanks, I took the original adapter and cut off a thin ring of material to use as spacer between the aperture ring and the mounting flange. It is hard to see because it is black.