EF Lenses on R Mount (f/1.2 portrait primes)

CESA wrote:

Questions now:

A. Having to adjust the lens this bad, meaning to such a high value is a bad sign?

I'm inclined to think so.  My first copy of this lens needed me to shift the calibration to the rear (*due to terrible backfocusing issues) ... all the way to the limits of the MFA settings.  I showed the Canon dealer that sold it to me and he agreed there was a problem... because If I later attempted to sell the lens to someone using say an EOS 60D, they wouldn't be able to use the lens because they can't calibrate that specific model of camera since it has no MFA setting.   The lens I swapped it for required just one or possibly two notches or so from 0 (zero).  I still needed a minor calibration but the different from the first lens was like night-and-day.

B. Would be prudent to return the lens?

I'd be inclined to do so - especially if the only way to gain focus properly is by pushing the MFA settings to the furthest settings.

C. Do you think I should test at another distance? Like 4m or 5m?

I's be inclined to make your calibration again if you were not satisfied with the results.  Because if you are not confident in the lens, you won't likely use it again very often.  This should be the best lens in your collection so getting the calibration right using flat targets (like batteries) ought to make it possible to set the camera to match the lens.  Be wary of using curved AF targets (like tube shaped AA batteries)... try to use flat targets that are not highly reflective.  Ensure the surfaces have something with contrast for the AF to lock onto and keep them aligned so that they are not tilting away from the lens. You should put the lens cap (or your hand) in front of the lens between shots to shift the focus to "infinity" (or close enough) .  Then take your hand away and allow the camera to focus on the target and take you test shot.  This ensures that the focus is forced to travel quite a bit before locking onto the target.  If you were to just shift focus between various targets that are close to each other, you may not be able to tell if the calibration is working or not.
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Focus will be more critical at closer distances where the DOF is shallower so don't go too far.  I tend to shoot a lot at minimal focus distance (MFD) a lot with this lens so I had to ensure that my lens was calibrated properly with the MFA feature.  At greater distances the AF should be producing good results because the plane of focus ought to be greater.  Up close it will be very narrow.
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However, I had calibrated for this lens a number of times, only to have to re-calibrate the camera again when I took pictures and the AF wasn't nailing the shot perfectly.  This issue really does only relate to f/1.2 lenses. Put any of these same lenses onto an EOS R camera and you're nailing the AF every time.  It's great that you can use this lens on mirrorless cameras although the 85mm focal length, especially at f/1.2, is not as impressive on an APS-C camera as it is on Full Frame models.