While the Z AF aren't as good as the D5 but Sony A9 is up there. Is it? I find the user reports and reviews mixed; suggesting that in some areas it is worse, in some better. "As good" in my view means as good in any situation, and in no situation, worse, because a photographer may depend on the performance of a camera in a particular situation. Dpreview: Sony a9 Full Review: Mirrorless Redefined "On the other hand, the a9 images during bursts would fall in and out of crisp focus (as we will see with some frisbee and cycling bursts coming up in the review), whereas the D5's seemed to be more consistently spot-on in this regard. The D5 was also less prone to jump to a different subject after an obstacle blocked the initial subject (though it's not perfect, as you can see in sample bursts provided below)." "Perhaps the biggest difference between the two, though, was that the D5 still just feels more immediate. I found that I still prefer the D5's optical viewfinder, though shutter blackout does put it at an objective disadvantage compared to the a9. Also, AF acquisition speed on the D5 is just absolutely instantaneous, whereas the a9 still appears to have a bit of a hiccup before it begins tracking with Lock-On. It was fast enough for these subjects, but the D5 is still just that smidgen faster." Anyway, the D5 is a 2016 body, the A9 2017, in 2019 or 2020 we can expect both manufacturers' cameras to be at a different level.