Laqup wrote:

the golden middle has been used ("3"). To be honest, at least according to the decsription and basic algorithm design principles it should not matter, as there is nothing moving in between subject & camera and actual subject detection has never been lost.

I'm going to have to go to the replay booth on this one ;~). One thing I believe I noticed in your examples—hard to tell for sure because of the way you presented them—is that the camera is indeed moving. I've written this before—and to some degree it's one of the things that is a bit different between brands—but handling discipline informs AF on the Nikons, for sure.

The position of the focus sensor boxes is the first sign that is telling me that. Locked down on a tripod on a static subject, the box won't move. Handle the camera loosely, and particularly with a subject that might move some, and the box will drift off. Worse still, the box is not where focus was achieved. The reason for that has to do with the timing of recording the box position. If I put the camera on something like a paint shaker, the box is never on the actual focus position, because the focus continues during the movement while the camera is trying to record the focus position. In other words, Nikon has chosen to put "focus box position" with the lowest priority in the chain of things it's doing while focusing.

But again, I'd need to see the actual replay of your photography session to make a more informed comment.

Finally, as someone else noted, the Zf lags the Z8/Z9 in autofocus performance some. I'm pretty sure that has to do with the way the viewfinder stream is done on the two different systems, and the speed at which the system is getting data. There's no lag in focus data stream on a Z8/Z9, while there can be on the Zf.

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Thom Hogan
author, Complete Guides to Nikon bodies
bythom.com dslrbodies.com sansmirror.com zsystemuser.com