« on: May 20, 2014, 03:42:36 PM »
Isn't the calibration Canon applying a micro auto focus adjustment? At f4, the depth of field is usually sufficient that your subject shouldbe in focus. At ff1.4, sure... but f4 is a while different animal. I'd be more concerned that the lens is off rather than the body and lens need to be paired.
There are shims and spacers located in the mount and various other places in the lens. These often need to be replaced if the alignment is beyond the +/- 20 AFMA range.