[davidmanze]

[quote pid='50532' dateline='1585899827']

PS. Over the years I've heard many togs say that using AF fine tune causes more issues than it solves and as a consequence never tune their lenses ...... were these people getting the best from their lenses ?? .........80% of mine needed tuning!

AF fine tuning as in AF micro adjustment? That is not the same as lens calibration.
AFMA is really only a band-aid to be able to overcome an AF issue in the field. 

AF on DSLRs can be "miss" due to different wave lengths not focusing on the same plane. It depends on what the AF sensor is sensitive to. "Recently (last few years)", I have seen many complaints regarding Nikon cameras and different AF results in daylight and in artificial light. I bet that is due to a certain band of "invisible" light (IR/UV) that the AF sensor sees in focus before it would see visible light in focus.
You can't AFMA that away.

A

  What would you call "calibration" ...... are you saying that Canon or Nikon would offer a calibration service?