So I decided to test focus accuracy with all my lenses. I tried doing this outside but there were just too many variable and mosquitoes. So I did it indoors mounted on a tripod about 5 1/2 feet away from target lit with an off camera flash. All images, both M9 and 5D mk2 exposed manually at f4 1/60 ISO 160. Focus point is the light stand in the middle. I realize resizing these images doesn't convey much, but it's a hassle to crop and resize them all. Also, excuse the mess.
15mm Heliar at f4.5 because that its largest aperture. Focus was eyeballed since it's not rangefinder coupled.
25mm Biogon. Very slight backfocus. But acceptable. Very sharp lens though.
28mm Ultron. Moderate backfocus. Seemingly enough to be noticeable in use. Also as some have noted the left side seems to be a bit weird. But in general I think it's a bit of a soft lens.
35mm Summicron v4. Focus is perfect. And a sharp lens.
40mm Nokton. Moderate backfocus that would be an issue on occasion in use. A bit of a soft lens also.
50mm Summilux v3. Very slight backfocus. Like an inch or two. Probably negligible in use. Not tack sharp but sharp enough.
75mm Summilux. Perfect focus. Very sharp.
90mm Summicron. Focus is good. A bit soft.
Canon 5D mk2 w/ 28mm f1.8 USM. Kind of an ugly lens. Focus is spot on. Not the sharpest lens but usable.
Canon 5D mk2 w/ 50mm f1.4 USM. Sharp lens, spot on focussing. Makes a pretty picture.
Canon 5D mk2 w/ 100mm f2 USM. Super sharp and spot on focus.