Went out with my new RF 100-500 and luckily there were some ducks.. So I was able to get an idea of its sharpness.. and.. WOW.
This thing is very very sharp.. almost super tele like... It smokes the EF 100-400 (which was already very very good) and there is no way a RF 600 or 800mm f/11 will come close to that IQ. So much fine detail, micro contrast.. I'm very! impressed.
Here is a duck portrait + a 100% crop.
Ente
IMAGE LINK: https://www.flickr.com/gp/generalstussner/6DHiF1
Duck




Looks like a couple of fire fighters or rescue team climbing the building that drew all of my attention away.











