Just a short info for users of EF version of the current 600mm f/4 (Mk III in EF mount): if you want to update the firmware of that lens (currently 1.1.3), better use a current R system camera + adapter. Updating worked flawlessly with my R7.
Problem with a 5D4, and this may happen with other older (or all?) EF mount DSLRs: I tried to update the lens firmware with my 5D4 several times. Every time when I clicked on the lens firmware shown in the menu, its display immediately went black, top screen showed "err" and it needed a reset by removing the battery (fortunately the firmware updating of the lens did not start yet). I did follow exactly Canon's update manual, to prepare it I re-formatted a card in the camera before I copied the new lens firmware on it on my MacBook, and my 5D4 has the latest firmware (1.4.0) installed.
Problem with a 5D4, and this may happen with other older (or all?) EF mount DSLRs: I tried to update the lens firmware with my 5D4 several times. Every time when I clicked on the lens firmware shown in the menu, its display immediately went black, top screen showed "err" and it needed a reset by removing the battery (fortunately the firmware updating of the lens did not start yet). I did follow exactly Canon's update manual, to prepare it I re-formatted a card in the camera before I copied the new lens firmware on it on my MacBook, and my 5D4 has the latest firmware (1.4.0) installed.
