KirkD said:
Here's part of that Canon-to-Sony exodus I'm talking about. I needed 4k video and was waiting for the 6D II announcement. When I saw there was no 4K, I went out and bought a mirrorless Sony a6500. Not only does it shoot beautiful 4K videos, but I have been very impressed with it in several other aspects, especially for telephoto photography. The photo below is what I'm talking about. When they announced the Sony A7III, it has everything and more, that the 6D II should have had. It blows the 6D II in the weeds. I'm keeping my best Canon glass, but I'm pre-ordering the A7III (Full frame 4K, in camera image stabilization, fantastic HDR sensor, etc.)
I pity you. I have an A7RIII at the moment, and an adapted 100-400LII (as well as the native GMaster 100-400 lens).
On the telephoto end, the 100-400LII is about as awesome as autofocusing a Nikon D850 at 400mm f/5.6 in live view mode. It's god-awful slow in comparison to a 6DII or a native lens, half the time it hunts forever, and many of the advanced AF modes are just plain disabled.
You'll be happy to know that Eye AF works, but who uses that on a telephoto lens
And good luck trying to shoot stuff moving either towards or away from you, because that 10 fps? You'll be lucky if you get 2 shots out of 10 that aren't blurry.
Frankly, I think it's unusable if your subject is moving faster than a turtle on pot. If you're really sold on the A7iii, just sell the 100-400LII and buy a GMaster -- which, by the way, is still far inferior in the initial subject acquisition in comparison to a 100-400LII on a 6D or 5D body. It's focus by wire, and by the time it takes to go from near to infinity, the subject is in a land far, far away.