This lens is sharp- enough to out-resolve the M Monochrom.
IF you ever get some shots out of focus, others in focus: I found one design flaw with the retaining ring that holds the front doublet in place. The retaining ring must be tightened using pin-type heads on a spanner. The retaining ring on mine had never been tightened down properly, the group would move ever-so-slightly when pointed down. Better now.