Laqup wrote:

But: As far as I understand the option "A3", blocked shot is not related to camera or subject movement but rather to objects that PASS in the line of sight between camera and subject.

That's basically correct for most situations. There is a scenario when your subject is so small (e.g. distant, small bird) whereby the camera may decide that the background is "the subject" and the "small object" is the thing that it should consider is blocking. Z8/Z9 firmware updates tended to "fix" that. But it doesn't apply to the situation you illustrated.

My interpretation is, that in case of "5" (aka delayed), a passing object would not lead to an immediate switch of the subject, the camera will rather try to "predict" / "estimate" / "guess" where the previous target was, where a setting of "1" (quick) would immediately lead to a switch of the subject from original to the one passing in between.

Let me correct the wording here some. Nikon's wording isn't exactly clear, nor are some of their descriptions of what it does. Moreover, CSM #A3 doesn't apply in some situations. The set value is basically ignored in 3D-tracking, and in Auto-area AF the values of 1 and 2 are ignored.

An object that passes in front of the recognized focus subject in Subject Detection will trigger the blocked shot response on the delay value you set (outside of what I just mentioned). But it's not about predicting, it's about "instantly change subject and thus change focus." If #A3 is delaying a change of focus, focus is kept where it was last made.

Maybe I should apply at Nikon to get things finally right then.

Nikon is trying to be consistent with what they've done for over a decade. One simplification on the Zf is that it doesn't have the Steady/Erratic subject motion option, and this could be an issue if your camera handling is shaky.

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