Canon 6D, Leica 100/2.8 macro - super sharp lens.
Macbook pro 2018 + LG 5K monitor.
I routine use my 6D with other lenes in dumb mode - everything manual. And works fine. (The live view histogram is not accurate but that is another problem)
The camera takes RAW, the JPEG on the camera is good.
But canon DPP RAW does not render sharp on screen - looks out of focus. So I cannot edit it.
A Leica 90/2.8 works just fine. Just this specifc lens - which is actually extra sharp.
This scheme (manual mode) also work with wide lens of older manual lens. Incomplete exif, no aperture, everything else is fine.
The usual ones are dumb adapters - the leica 100/2.8 is also dumb but Leitax adapter (screwed in).
On camera JPEG is good.
Try taking photos of something with lots of detail that is about 4-6 feet from the lens. Set the aperture to f/16. Is it sharp?
Yes it is - in fact superbly sharp! The in camera jpeg is as I expect. The RAW rendered when DPP just starts up is good - but in few seconds becomes out of focus. Something it is trying to do messes it up.
I use other old mechanical lenses (hasslblad / zeiss etc) - all work great. Even other Leica R works great.
Just this specific one! Unfortunately, this is the "best" lens!
In all the cases, the camera does not know there is a lens there.
Works in all cases except this one! 100/2.8 macro is considered one of sharpest leica lenses. I can see that in the on camera jpeg!