Ive got an interesting story as to why im possibly very interested in the high mp canon eos r camera.
over the past two years i felt a bit let down by canon for not supporting the "low budged" wildlife community as much as wished for. I had really hoped for the 7d iii and when the rumors about no 7d iii and only a 90d showed up i was very disappointed.
Then i saw sony announcing and releasing the 200-600 and the a7r iv, which seemed to me like everything i had whished for in a portable wildlife setup, so i bought the camera.
But for the last two months i only had problems with the sony setup. my plan was to use my sigma 150-600 sport with canon mount on a sigma mc11 adapter until i could save enough money to buy the sony 200-600. With the adapted lens i had a big backfocus at 600mm and couldnt really use it. So i speed up my saving and quickly bough the 200-600 but i had the same backfocus on that too, so i sent it back.
I then tested my sony a7r iv with a completly different 200-600 at my dealer and again the backfocus. My dealer then exchanged it against a new a7r iv... but still the same backfocus.
I even sent in bouth of my sony a7r iv for repair but they said they cant do anything about it (only sent in the body, not the lens).
Now im visiting my dad and checked out the camera store near his city and tried out their a7r iv and 200-600 they had... again a backfocus.
I dont know why noone so far has talked about this problem. Maybe they dont pixelpeep enough.
Well ... at this point it seems to me like sony is really a huge let down for me.
So i look forward to that canon, but im afraid it probably wont focus well enough for wildlife, what do you guys think?
That is a very strange coincidence that you went through at least 3 bodies and saw back focus on all of them. Because the A7r4 is using phase detect focus, it is very rare that there is an AFMA issue. However, if there is an issue, there is an AFMA option in the menu. You can see a guide for that here:
I know it's annoying for the forums to indicate that you might be doing things wrong when you bring up a problem, but the math suggests that you might be doing something wrong. For instance, if you have a corner focus point set, you might find the lens always focusing on the background. It's just very odd to have a consistent, multiple-body focusing issue without other people indicating a similar problem. One thing I have seen with my A7r4 is that it doesn't follow focus as quickly as my A9 cameras, so if something is coming toward me, I will see a backfocus (like I'd see a front focus with objects moving away). But even then, it is still following as fast as my Canon 5D4s did. If you shoot the A9/A7 combo, you might find yourself criticizing the A7 performance on AF speed.
I wonder if you'd discover a problem if you let one of the shop people take the camera and lens and do their own settings and then report to you what they find. Feel free to message me if you want to troubleshoot.
As to you question about the new 5 series being a potential solution for you, I don't see why that wouldn't be a good option. I'd look at how many lenses you have right now and either try the A9 Mark I - used for about $2500 now - if you had more Sony glass, or get the new 5 series mirrorless if you have more Canon glass. I'd put a condition on the Canon choice that you'd have to first see what the AF tracking frame rate is for the camera and make sure it is a multiple of that of the current R offering (3 fps) if you're going to be doing action/wildlife. Another option if mirrorless isn't a do-or-die factor might be to get a used 1dx mark 1 (used for $1800) which I found to be a good percentage as good as the Mark II. In my opinion, the A9 Mark I and the 1Dx Mark I are the two most underrated cameras on the market for the price. Don't bother with the A9 mark II if you stay with Sony, as I own both versions, and the II has only nominal benefits at a much higher price.