Out with the R6 and RF 800mm in the morning and with the 90D and 100-400mm IS II in the afternoon, I had almost exactly the same relative reach in either instance. In bright sunlight, where the 90D shot around two stops faster ISO most of the time, the R6 made far better images.
The 90D couldn’t AF accurately on any shot with the 1.4X III attached, something I thought I’d noticed on previous outings and was able to confirm today. It’s currently keeping the S5 company in the outbound lane, after previously getting a reprieve. No more.
The RF 800mm, even with the challenge of harsh light, appears to be somewhat better than the EF zoom + teleconverter. Then again, my memory says that this copy of the 1.4X III is not nearly as good as past copies I’ve owned. No surprise as RF takes over from EF.
Sigma responded to my query about the 150-600mm, mum on whether it’ll come in RF mount. And the cost of converting L to Sony E is so expensive that it’s more practical to sell one and buy the other.
Critters, keen interpreters of human intent, continue to be unusually friendly much of the time in this area. The White-Throated Kingfisher in the second shot below flies out to greet me regularly now, flying off after I snap a few shots and continue on my way.
One of my Masked Lapwing friends actually walked closer to me again while I was shooting. Well, if he is a zoo escapee, maybe a food offering from his human observer is expected? 😉