I had observed some odd plane of sharpness in a number of field images at f/2, made with the Leica 50mm f/2 APO-Summicron-M ASPH and the Leica M Typ 240, both literally right out of the box: checking my shooting timeline in the field, the issue appeared immediately upon use so it cannot be some trauma to the lens.
Presented in Skewed Plane of Focus are several examples and one counter-example.
Sharp across the frame, but not at the same distance: skewed to the distance at upper left, to the foreground at lower right, in a very significant way. Of course, stopping down masks the issue, and by f/4 is becomes hard to see.
As an educated guess, it could involve focusing distance and/or a loose lens element, the latter of which was diagnosed by Leica for my brand-new 21/3.4 Super-Elmar-M a few years back. Nor can I rule out the camera as yet, which would be even more of a disappointing disaster, because it would affect all lenses. I must emphasize that the issue arose literally right out of the box on my very first shoot. But being in the field, I was shooting not analyzing so it’s not until I went through all my images that I could see the pattern emerge.
I called Leica and they were willing to help, but there is a basic gating factor: all M Typ 240 bodies have to go to Germany for repair, and probably the 50/2 APO also. As I am leaving on another mountains trip in a few days, I’m just going to run some tests to double-check and hopefully rule out the M240 camera body.
While I see no evidence that the camera is at fault (and f/3.4 and f/3.8 lenses are already masking the isuse). Still, if it is a camera issue, then all lenses should show the skew, so I’m going to shoot some lenses at f/2 and try to see if I can produce a skew.