Again, you assume. I was merely suggesting you actually try and see.
Easy enough to say when it's not your money going towards the trial.
If the AF doesn't hold up with an adapter (and, so far, it doesn't hold up for tracking action with any lens, from any maker, on any adapter), I'm stuck with a $3000 lemon.
One of your main complaints is that the 70-200 Sony was mush at f/2.8, so how is a slow f/4 100-400 going to solve your desire to be razor-sharp at f/2.8 ![Shocked :o](https://forum.luminous-landscape.com/Smileys/default/shocked.gif)
If it's sharp wide-open, it still ticks off several requirements that would otherwise require an extra lens in the kit.
If it were only sharp in the middle, it would covers the odd wildlife or distant action shot on trips not otherwise dedicated to wildlife.
If it's also sharp enough in the corners for lsndscape work, it can pull double duty as the telephoto landscape lens. That way, I could do without the 70-200 until a good one comes out, rather thab choosing between one that is soft and one which won't AF as well as a native lens.
Not so. Canon's L II and Nikon's VR II 70-200 lenses were basically even, until Nikon upped the ante with the 70-200E FL ED, improving it in every respect, whilst minimizing its size and weight.
Central sharpness, yes. Not so much in the corners, and not so much when it came to CA. The VR II was close, but the Canon was still ahead.
There are a lot of if-clauses, "likelys," and "may"-prognostications in your thinking.
Back to reality: no one is going to buy Nikkor, and they've been completely dominant (batting 100%) in creating class-leading super-teles with their E FL ED glass. Thus, why not see for sure how the best current 70-200 f/2.8 works for you?
It's just a suggestion. Won't hurt to give it a shot.
It's a $3000 gamble with bad odds. No other lens on any adapter comes close to matching the AF performance of even the worst native lens. Why should this be any different?
Nikon's telephotos are currently the best because they're also the newest. Notice how the general trend is that, where the Nikon lens is newer than the Canon equivalent, the Nikon is better, while, when the Canon lens is newer than Nikon's closest equivalent (e.g. 11-24, 16-35 f/2.8, 200-400) the Canon is better? Nikon and Canon lenses keep leapfrogging each other, and whichever one is better at the time depends largely on which one is newer, rather than who makes it.