Focus Persistence....Nikon AF (D6 and Z9)

[fcotterill]

Focus Persistence holds the position of the point of Autofocus, so one can switch the AF mode without losing the subject. Its advantage is not only to avoid manually repositioning the cursor, but more importantly it avoids losing focus and missing the Moment. Basically leveraging Focus Persistence is part and parcel of 'toggling' between AF modes almost instantly..... The feature works by enabling inheritance - in a split-second - of the AF point position despite switching between AFmodes.

It allows switching 'inwards' or 'outwards' between AF modes.... from the widest expanse of the AF cursor space to a focal subject OR locking on to subject with a tightly delimited mode (eg Dynamic or Custom Area) and then switching to 3D Tracking or Auto to track the moving subject. So Focus Persistence allows switching AF modes on the subject without losing focus on the subject.

This feature helps use improve what Thom Hogan describes as 'focus decision making on demand' with customized Fn buttons.

Nikon's Mark Cruz explains how it works one useful aspect in this video, although IMHO he doesn't go far enough in covering the full scope of what it enables - particularly in how the instant-inheritance of Focus Persistence maintains precision in switching AFmodes in either direction from tight to full screen and vice versa

Nikon first released this feature over 2 years ago: and somewhat under the radar due to the timing and the nature of the new camera. Focus Persistence was just one of the less conspicuous new features in the Flagship D6., and migrated into the Z9. Of course, it didn't help that the D6 began to ship when the pandemic was spreading, in April-May 2020.

It's possible many a D6 owner forgets this feature exists, after setting a13 to Auto on the D6. Focus Persistence just works and very well, IME. In any case, most of the youtube 'reviewers' and forum threads seem to have been more obsessed as to whether the D6 was really a D5s. So few barely, if at all, tested the camera and highlighted this feature among its other significant improvements.

The D6 AF system is an utterly different entity to the D5 AF. I have found it's taken me a few months of experience to full appreciate the differences, and what the feature empowers (and the Nikon Manual is more than vague). Focus Persistence was one of the minor features - together with 7 new Custom settings - introduced to optimize and leverage the advanced AF engine in the D6 - along with eye and face recognition, much improved 3D Tracking, and of course the D6 launched Nikon's Custom Area modes (Z9 precursor!) and much more under the hood [the appended table gives some insight in D6 Sports AF Tips/Guide ].

Nikon seems to have cloned the core of the algorithm underlying this feature into the Z9 (Custom : a7). It also works by fixing the location of the AF cursor even if focus modes are switched. Hence, as with the D6, the primary aim is to help sports photographers grab firm focus on a challenging subject (typically moving fast/appearing suddenly); then once locked on, the Z9's AF tracks the subject thereafter using AutoAF or 3D Tracking. Thom Hogan reported some preliminary findings using Focus Persistence, in a December 2021 Blogpost: photographing African wildlife. And we discussed the feature in a Z9 thread here, back in January.

IME as with the D6, I find a big advantage with the Z9 is that setting a7=Auto does indeed underpin almost instant switching between focus modes: eg. from 3D Tracking (or AutoAF) to a smaller focus area if the camera-driven AF is struggling (eg with the proverbial bird in the bush) OR going the opposite way by transferring the focus from a tight AF point to 3D. So this feature is a boon for birds and mammals in scrub, or moving through trees etc. Thus, with my preferred AF modes mapped to Fn buttons (as AFMode+AFOn).... and the Z9 in BBAF, IME Focus Persistence has worked seamlessly in all the FW versions - switching to and fro between AF Modes.

 

[fcotterill]

There are a few more features in the current flagships to leverage control of the AF cursor more efficiently, being much quicker than manual scrolling, as well as allowing dual press&scrolling of an active AF mode.

These additions to the Z9 and D6 augment the Store Points by Orientation setting (a5) to that memorizes AF cursor (and AF mode) turning the camera between Landscape and Vertical formats. Preset Focus Point is another useful feature that's also been available in Nikon DSLRs for several years. With practice, trained muscle memory using these features can save precious seconds winning out on ephemeral moments framing the subject.

In Firmware 2.00, Nikon also added a new control to the Z9: Custom function f13. Perhaps its delayed addition suggests optimizing the underlying code wasn't as trivial as it might seem, because Nikon only launched this same option - in the D6 - in May 2021 (FW 1.20), months after the camera's launch.

This feature extends the usability of the sub-selector button in both the Z9 and D6. It allows you to still shift the AF cursor position, while activating the custom control assigned to the sub-selector center button. This dual function is enabled when ‘Prefer sub-selector center’ is turned OFF. A useful way to appreciate the advantages is to assign an AF Mode to sub-selector center, and test out press-with-scrolling the cursor of the active AF mode active. The default is ON, as Steve recommends in his Z9 book, however I find it works well OFF on my Z9 and D6. It's often useful IME to have track&focus under one's thumb with a Custom Area mode.