Canon R3

[Fast Glass]

So I have a question for a friend across the pond who is getting an R3 and a 300mm f/2.8 IS. He was talking with someone that said that he wouldn't be able to take advantage of even 20fps because the AF on the lens is old and not able to keep up because he has an R5, but not a 300mm f/2.8 IS. So you can see the irony here but anyway. He went back and forth with him and explain the thing with having a full battery and all the caveats to get full FPS on the R5. Well he is not convinced.

So his question is two fold, will the R3 get full performance with the 300 and is it as good as the 1Dx III. He pretty much knows that it will be as far as driving the lens fast enough, his theory is it uses the fantastic LP-E19 battery and will have no problem driving it and that is a limiting factor, among other things of course. But he is less sure on how it compares to the 1Dx III, he is coming from a 1Dx II and is a sports photog. His work is very nice, so he has a handle of photography.

I told him it be awesome to just join the forum but I guess he said the admins have disabled it? Maybe on vacation? Dunno.

Anyway, that was his request. He can at least read the responses.