[Arthur Macmillan]

"The noise banding the 5D mkII gives is very widely known. The 5D mk II in my opinion is a nice tool, but in sensor output the 6D has passed it by some margin. "

 

I don't doubt what you are saying.  I had decided, back when the prices were not that far apart to get the 6D.  Now I would be tempted to look for a 5D Mark III on the used market. 

 

But getting a pristine 5D Mark ii for $215 is too good to pass up.  This camera doesn't even look used, and it is from someone I know who just wanted to make a FF camera available to me, not a seller who prepped it to sell.  She even let me borrow her 17-40mm F/4L and I high end Tamron VC zoom.  So, by my way of thinking, that plus a 1.4x Tamron SP autofocus compatable teleconverter for $10, I got a whole lot of toys to play with for a total of $225.  I refuse to mourn my bad luck in not getting a 6D!

 

As to the effect on AF of moving the focusing group relative to the focal plane, and your example of being able to focus using a tube - and please, I do see your point!  I just wonder in an innocent beginner way if there might not be some effect on AF as there would be some effect on depth of field.  A will throw in yes, for a very small amount, the effect on DOF is corresponding small.  That was just conjecture 1.  Conjecture two - Again, I'm just guessing...not saying... but MFD is something the might be fixed physically, even if I know infinity focus most often is not.  If an algorithm assumes closest focus to be minimum focus, and it is not, well who knows.

 

All that said, you are probably right.  I'm am just hoping for the day the MFA can be automated.  In fact, I've seen products that seem to claim this ability.  I think it is software plus a target.  But I am hoping someone like you figures that one out.  Complicated stuff to me!