[Klaus]

vs the EF 70-200mm f4 USM L IS II

[Klaus]

Oh, it's not compatible with TCs ...

[Brightcolours]

The RF TC's protrude too much. Same thing with the f2.8.

[Rover]

There were non-protruding EF TCs (third-party ones, though the exact brands elude me). Here's hoping something similar appears for RF down the road.

I'm not really convinced that Canon has excluded the TC compatibility on purpose - so that people would buy a 70-200 and also their 100-500 for when they need to go longer instead of just slapping a TC on their 70-200 - but I guess the circumstances may lend "a little" credibility to that idea.

FWIW, I own both the 70-200/2.8 and the 100-400/4.5-5.6 in EF mount; for some reason the TC route never worked out for me and these two lenses are (almost) never taken together on a single outing anyway. Of course the ver.1 100-400 cost me about $500 and a brand new RF lens north of $2500 would not have been such an easy purchase...