As mentioned earlier in this thread, researching this topic of focus persistence, I find contradictions in the official documentation, which is vague on the details.
According to
Nikon Tech Advice, Focus Persistence is not supposed to work outwards from tighter spatial AF area to 3D.
and Thom H is vague on precise details in his Z9 blog and his ebook
Day 7 of the Z9 in Africa blog
www.zsystemuser.com
I've yet to read a clear explanation online specifying what controls work - or do not work - to get Focus Persistence. Steve has done the best job that I've read IMHO, with a neat illustrated example in his Mirrorless AF (pp 274-5) and Z8/Z9 books. His examples are comparatively straightforward, and incidentally he is using single point mode on the heron
There's more going with the settings in how Handover(s) work between AF modes. It's not as clearcut as made out - there's more going on under the hood than Focus Persistence. One reason seems to be Subject Recognition is an important variable with/besides actual Focus Persistence, and many Z9 (and likely Z8) users keep SR on most subjects.
These gaps is important to get beyond as to how Hand Over works. So further testing is needed.
Here's what I've got regarding Focus Point Persistence. Please pardon any of my over-simplications and long windedness, as I wanted this to be useful to any skill level.
Setup:
1) Your default AF-area mode must be one that allows the camera to move the active focus point, so any Wide-area or 3D or Auto-area. Note that the Wide-area must be actively tracking via Subject Detection. If Wide-area doesn't have a subject (light gray box) the "persisted" point will be the center of the Wide-area, effectively serving no purpose.
2) The AF-area mode that you are "persisting" to must be assigned via Custom Setting Menu "Custom controls (shooting)" (f2 on Z9 fw 4.0) to [AF-area mode] or [AF-area mode + AF-ON]. All AF-area modes are able to be on the receiving end of the Focus-point persistence, even though the manual states "...to a mode in which the focus point is selected manually."
3) Custom Setting Menu "Focus point persistence" (a7 on Z9 fw4.0) must be set to "AUTO"
Engaging:
1) The camera must be actively auto-focussing and tracking using the default AF-area mode from Setup step 1 above. So:
1a) shutter button half pressed if Custom Setting Menu a6 [AF Activation] is set to "ON"
-or-
1b) you've assigned a custom control with role "AF-ON" and you are holding that custom control/button down.
*Note again that the "persisted" point when using a Wide-area will be the grey box if a subject is found, or the center of the Wide-area if no subject is found.
2) While maintaining active auto-focussing, press and hold the custom control/button from Setup step 2 above. Note that once you've pressed this button you are free to release the half shutter / AF-ON button from Engaging Step 1 above.
Disengaging:
1) Release the custom control/button from Setup Step 2 above. Deliberately or accidentally
General notes:
1) The focus point position will return to it's last set position once Focus Point Persistence is disengaged unless you also manually move the focus point via Sub-selector or Multi-selector while Focus Point Persistence is engaged. Handy trick if you want to move the focus point position, just give it a quick bump before disengaging Focus Point Persistence.
2) I think there is some confusion between "Handing off" and Focus Point Persistence, but the latter is a one way street following the steps above. You aren't able to "persist" a focus point going the other way. There can be an illusion it's happening, perhaps if you're using a Wide-area on Fn button and are tracking the subject
at the center of the Wide-area so that when you release the Fn button to go to the default AF-area mode the focus point does't move (since it is at the center of the Wide-area box, which coincidentally is where you had the subject) and therefore the target under the new focus point is good enough for the camera to appear like it never hiccuped. But it's not guaranteed and can cause hunting. Do this quick experiment (probably easier with shutter-button focus): Set single point to your default AF-area mode. Set a 19x1 Custom Wide-area plus AF-ON to some button, say Fn1. Find a subject that will trigger Subject Detection. Prints of my kids make for easy, stationary targets. Or pull up a picture on your computer. Press Fn1 to activate the Wide-area and see how the gray Subject Detection box moves as you pan the camera over the subject. Now, pan such that the Wide-area box is still activating Subject Detection but the center of the box is not over the subject. With the shutter button half pressed, release Fn1. Note that the focus point is now at the center of where the Wide-area box was, and the camera is focussing off the subject now.
3) There is no "a" in persistence, no matter how many times I type it that way.
Andy
)
