I compared how AF works on the E and A format on the presentation of the A7 * cameras, well, in general there is no comparison in speed. Yes it works, but it induces very slowly with adapters without a mirror. If you take an adapter with a mirror, it’s still slower. Errors AF in aiming at the object appear. And the meaning of the mirrorless is completely lost, the AF system in the adapter is very weak, the AF points are less than in any SLT camera, it even worse than on the A57, I'm not talking about the A77-2 and even more so the A99 * series. Yes, I looked closely at A99 on eBay, but AF speed is still more important for me, and the quality with 24mp images is almost the same. This is especially felt on old lenses with an AF drive from the camera, they focus much faster (well, the ones that I have
). So far, everything is fine in A format.
I think that you can confirm this by having two cameras on the hand.
Tamron 70-300mm F / 4-5.6 USD SP. I have been using it for a long time, it works perfectly with all cameras and APS-C and FF. Both AF speed and sharpness are beautiful. Especially in the range of 70-200 (120-135) is very sharp. On cameras APS-C gives 450mm (300X1.5 = 450) with its low weight. But with A99-2 it is not very sharp, it is not good enough for a 42mp matrix. Well, of course it works, but not like with the A77-2. Therefore, I purchased a high-speed Minolta 80-200.
In general, there is not a single criticism of Tamron(Sony sell same lens 70-300 - with own name on it.
). Over the years of work, sometimes in "hellish" filming conditions, Tamron has never failed.
PS. If you can find some used Sony flash like HVL-F43M or F43AM(old standart) - they the best! I have also Metz 44 AF-2, but Sony F43 way, way better!