TWI by Dustin Abbott said:
Talys said:
Thanks for another great review.
I've only used this camera in the store, but what I noticed right away was the EVF. It's such a step down from the A9/A7R3, that I don't think I would choose this model, between it and the "R". Then again, I'll freely admit that the VF is a critical part of my decision making, and, along with AF speed, remains one of the key reasons I haven't been convinced to switch to mirrorless.
AF performance is, in my opinion, no longer a reason to not go mirrorless. I got better tracking results with the a73 than I have with any DSLR.
So, first of all, most of the time that I need fast autofocus is birding, and that's the lens through which I'm making these comments (sorry, pun intended

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There's autofocus tracking, and autofocus speed, which aren't the same thing, though. I agree that the tracking capability is great, but you have to get autofocus in the first place.
I haven't tried an A73, but I did have an A9 for a couple of days (and an A7R3 for over a month). Using the 100-400 GMaster, the speed to go from near to infinity is horrible. If you defocus, then try to focus on a hovering hummingbird, for example, you'll never catch it in the second or two that you have. Now, if you throw on a 1.4x extender -- which his the only solution to go higher than 400mm -- the autofocus speed is just dismal.
Take a 1DXII, throw on a 100-400LII and a 1.4x extender (which, in my opinion, when using extenders, is the best AF speed camera currently on the market), and the autofocus speed just blows it away. Throw on the Sigma 150-600 (which will require an MC-11 adapter on the Sony), again, a huge difference.
I actually had the 100-400 GM + 1.4x extender beside a Nikon D850 with the 200-500 at the same time while at a birding spot. The performance difference was just night and day -- it's hard to overstate. The AF speed at 400 and 400+extender on full frame is pretty important, IMO, and it's still not there, yet, in my opinion. There is the additional problem of the VF being blacked out while you raise it to you, making pointing the camera at as small subject quickly at telephoto lengths sometimes challenging (by the time you see anything and the AF starts to engage, the subject has moved). As a result, you need to start at a lower focal length, track it, and then crank the zoom -- which is rather noobish and misses some great shots
The problem with autofocus tracking with birding is that it's almost useless. You want the bird to fill up as much of the frame as possible, for reproduction clarity. But then, most birds are moving so fast that the tracking has no chance, and anyways, you only have it for a brief time.