Recently I receive my Black M8 back for NJ and while it was there I ask them to check the focusing.
When I got it back I mounted my 50 Summilux on it and found that it DID NOT focus correctly, it backfocused. I then set out to find out why becasue on my Chrome M8 the 50 Lux is fine.
Doing the infinity focus with the 50 Lux and 75 Cron showed that the images were not lining up, IE they did NOT get TO each other. This means that you had to turn the lens to a father distance setting to get the Range/Viewfinder images to coincide which will give you backfocus. So I adjusted it, got it to where I think the images are lined up, and then did some minor tests checking more for sharpness of focus point then worrying about how much in front of or in back of the focus point the DoF covered.
Then last night it was incredibly clear here in Atlanta with a nearly full moon. So I set out to mount every lens I have on the black body and check infinity focus, in repect to how the the images lined up in the View/Rangefinder. The results were startling.
With every lens I own, except the 50 Lux and 75 Cron, the Range/Viewfinder images went PAST each other to some degree, more with some then with others and my 50 Cron was about as close as the 50 Lux and 75 Cron but still past slightly.
I then set out to do some focus test with all lenses on both bodies.
I didn't try to be to precise with the focusing. I'd mount the lens, adjust the focusing ring and when my test target image came into what I thought was good focus I took the shot. Only a few time did I go past focus and then back and then back again.
The result from the focus tests showed that all my lenses had GOOD FOCUS @ the POINT i was focusing on.
So it seems that Leica lenses are not all calibrated to set the range/viewfinder to true overlapping images when they are set to infinty.
So John I would do some test with your various lenses at different focusing distances to see if the images they produce are acceptable, and of course do some near controlled focus tests to see if they are really focusing correctly, before I'd adjust the infinity focusing cam.
My test opened my eyes as to what can happen with a multiple lens Leica M kit.
It is the small roller right at the throat of the body; a 2mm allen adjusts the eccentric the roller is mounted to. Tiny adjustments are usually all that are required, like moving the end of the wrench 1mm at a time or like one minute on a 60 minute clock face. Try CCW first if you're not quite hitting infinity. However, be advised that adjustment may alter the total focus arm length pushing close focus off, though not likely to be a significant change unless your infinity is way off to begin with. (The arm pvot adjustment is back inside the camera at the other end of the arm and more difficult to make.)
