360Photography

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Nikon has released a much-anticipated firmware update intended to improve autofocus performance from it Z-series mirrorless cameras. Specifically, Nikon promised improvements to autofocus in low contrast and low light shooting situations, but perhaps the most anticipated feature this firmware brings is continuous Eye AF.

As soon as the new firmware became available we updated our Z6 and Z7, and we’ve shot extensively with the updated cameras over the past few weeks. I routinely use a broad spectrum of Eye AF implementations, particularly Sony’s best-in-class one, and I can state up-front that I’ve come away very impressed. But not without a fair share of caveats and suggestions for improvement.

Does the update address the autofocus usability and performance issues we detailed in our Nikon Z7 review? And how does it stack up under the microscope against the best Eye AF systems? Read on to learn more.

Table of contents:

• Identifying eyes
• Focusing on unintended subjects
• Choosing your subject
• Eye AF accuracy
• Conclusion
• Footnote: compared to Canon EOS R / RP

Eye AF on the updated Z6 is so effective that it even found the coach’s eye underneath his cap. Nikon Z6 | Nikkor 70-200/2.8E FL ED VR

Identifying eyes

When it comes to finding eyes and tracking them, the updated Z cameras compare very favorably to the a7R III.

The Z6 and Z7 are able to routinely identify eyes behind glasses, and even when all you see is a person’s profile, as in the shot above, or this one. It then holds onto the eye nearly as tenaciously as the a7R III. As it turns out, it’s often even better than the Sony at initially identifying eyes in sideways-turned or downward-looking faces. That said, once the a7R III has identified the eye of your subject, it tends to be better at sticking with it, even if their face is turned to a profile. Faces and eyes have to be a bit larger in the frame before Eye AF kicks in on the Nikon, but in practical use this difference is negligible.

A situation where the Nikon Z6 found my daughter’s eye, but the Sony a7R III did not. Unfortunately, as you’ll see in this series of shots, accuracy of focus was comparatively poor, an issue that particularly manifests itself as light levels drop. Nikon Z6 | Nikkor 35/1.8 S

But simply identifying eyes and faces isn’t all that useful, in and of itself. Accuracy of detection (i.e., not seeing faces where there aren’t any) and accuracy of focus are the more important factors. Let’s investigate.

Focusing on unintended subjects

A downside of Nikon’s eagerness to find faces and eyes means sometimes it finds them where they don’t exist, like in this featureless shag carpet or these trees in the background. When this happens, even if a real face re-appears the camera is often reticent to refocus on it, especially if it’s at a vastly different distance-to-camera. Often the camera will hang on to the mis-identified ‘face’. In comparison I’ve never found Sony cameras to identify a non-human subject as a face or eye.

A downside of just how easily Nikon Z cameras find faces and eyes is that quite often it finds faces in objects that are not faces. In this case, the camera detected a face in the ladder in the background. It was then slow to re-focus on my daughter when she revealed her face again, and in some instances remained on the ladder. Nikon Z6 | Nikkor 35/1.8 S

This problem with false positives could be worked around if the Z cameras worked more like (recent) Sonys and Canons in which Eye AF works over the top of their subject tracking modes, meaning you can point your initial AF point at your subject to tell the camera what to target.

The omission of Nikon’s excellent 3D AF Tracking feature in the Z-series (and its replacement with an unintuitive, less effective subject tracking mode) was our biggest gripe about the Z-series when it launched. It would have been a perfect mode to layer Eye AF on top of.

Instead, Eye AF is only available in the Zs’ ‘Auto area’ AF mode, where the camera is left to decide what to focus on. While it makes sense that an auto area AF mode might assume that the nearest thing to the camera is your intended subject (see below) this is not always true.

Despite there being two clearly identifiable faces within this scene, in ‘Auto Area’ mode the camera chose the nearest subject. But can you blame it? Most ‘auto’ AF systems are designed to focus on near, central objects because It makes sense, most of the time. Nikon Z6 | Nikkor 70-200/2.8E FL ED VR

The soccer ball was not my intended subject in the image above, my daughter was. And that’s the problem with Eye AF only being added onto an ‘auto’ mode: you have accept that sometimes the camera will focus with a mind of its own. Most ‘Auto’ area modes tend to prioritize central, nearer objects like the ball above, and that’s not always the thing you want.

There is a way to force the camera to refocus on your subject once its focused on an unintended one (more on that below), but this doesn’t always work reliably. If your subject is at a vastly different distance from the one the camera is currently focused on, the Z6 / Z7 can be particularly reticent to refocus. The AF system either flat out refuses to refocus, or does so hesitantly. This again highlights the need for a robust subject tracking autofocus mode, to which Eye AF should be coupled.

The Z7 initially chose to focus on the background in its ‘Auto area’ AF mode. This is unfortunately common behavior for the Z-series cameras. The bigger problem is that after the camera has focused on the background, it’s reticent to refocus on a foreground subject if the subject is so far from the background that it’s extremely blurred. Nikon Z7 | Nikkor 50/1.8 S

Choosing your subject

As you can see, most of the problems come from the camera choosing the wrong subject. You are given some tools to rectify this, but these have their own drawbacks. Let first explain why this matters.

Event, wedding, and many other photographers trying to capture candid portraits have a very specific requirement that many manufacturers tended to overlook in the past: the desire to choose which face, among many, to focus on. On the latest Sony cameras you can simply place the AF point over your desired face and half-press the shutter button.

Nikon offers two ways to choose your subject: tap on a detected face or eye on the rear LCD or use the joystick or four-way controller to jump between eyes and faces.

I wasn’t able to select my daughter (in the background) as the target because the Z6’s AF system did not detect her face. If Eye AF were combined with a proper subject tracking mode, as it is for Sony’s ‘Real Time Tracking AF’ or Canon’s Face+Tracking on its EOS R/RP, then I could always rely on the camera at least tracking my daughter, whether or not it has detected her face or eyes. Nikon Z6 | Nikkor 70-200/2.8E FL ED VR

Normally, tapping on the LCD from ‘auto’ area mode is one way of engaging subject tracking. But if you tap on a detected face, the camera will automatically enter Eye AF mode instead of subject tracking mode. Note though, if you are a bit sloppy with your tap such that the camera ends up tracking a part of your subject’s shoulders or body, the camera may enter subject tracking mode and won’t engage Eye AF until you manually cancel tracking and try again.

Using the joystick to select your subject works quite well on the Z-series cameras

Either way, repeatedly having to take your eye away from the EVF just to tap on the LCD isn’t a great user experience, especially if you’ve just moved from a DSLR and are used to always having your eye to the viewfinder.

Thankfully, using the joystick to select your subject works quite well on the Z-series cameras, even allowing you to quickly toggle between the left and right eye of your subject. There’s a caveat, though: in order for you to switch to a different person, the camera has to have identified that person’s face. In candid shooting, if your subject is looking away, or for some reason isn’t identified as a face, you’ll find yourself repeatedly hitting the joystick or tapping the screen with no result.

Thankfully, a moment later, the Z6 did detect my daughter’s face, and I was able to hit ‘left’ on the joystick to switch from the blonde child to my daughter (in-focus). But this way of choosing your subject can be a gamble, dependent upon whether or not the camera has detected your intended subject as a face / eye to switch to. Nikon Z6 | Nikkor 70-200/2.8E FL ED VR

In practice, some of these concerns were allayed because the Z6 and Z7 are just so darn good at identifying eyes and faces that more often than not, I was able to select my daughter. And once I’d selected her, it stuck to her like glue. Even if she looked away, the Z6 continued to track her head, ready to jump back to her eye when she faced the camera again. Now, if your subject completely turns its back to you or looks away for long enough, the camera will eventually jump off to another eye in the scene.

So it’s not bad, by any means. However, the very best current system don’t have these problems. The systems introduced in the Sony a9 and a6400 will track a subject and automatically switch in and out of Eye AF as necessary, as it finds or loses them on the subject being tracked. And that’s the bar the Nikons have to live up to.

Eye AF accuracy

Now that we’ve talked about the ability of the cameras to detect eyes and select the right one, let’s get to an arguably more important question: how often are the resultant photos actually focused on the eyes?

In good light, for the most part, the Nikon Z6 and Z7 do a great job of focusing on the eye. It’s a good deal better than Canon, but it doesn’t quite compete with the repeated pinpoint accuracy of Sony’s system, particularly in challenging light as we’ll see below.

Nikon Z7 | 105mm F1.8	Sony a7R III | 135mm F1.8

While few would complain about the above result (this is a 50% crop), if you roll over to the a7R III example, you’ll see that the eye itself is in better focus, while the Nikon Z7 shot is slightly front-focused. Interestingly, on those occasions when Eye AF accuracy struggled on the Nikon, I almost always found the result to be fractionally front-focused.

Nikon’s Eye AF reticule tends to be rather large, especially compared to Sony’s, and I wonder if this is at least part of the reason. After all, contrasty features around the eye like eyelashes and eyebrows fall in front of the eye. In the image below, focus seems to lie on my daughter’s eyebrow, something that happened with quite some frequency:

I found Eye AF on the Z6 to front-focus more than I’d expect, sometimes significantly so. Here the camera appears to have focused on my daughter’s eyebrow. Nikon Z6 | Nikkor 35/1.8 S

The extent to which this inaccuracy might affect you will vary from lens to lens. With many lenses and subject distances, the slight difference in distance between an eyebrow and an eye won’t matter. But for shallow depth-of-field applications, and particularly with fast wide primes like the 35/1.8 where the difference in camera-subject distance between the eye and the eyebrow can be significant, I found the inaccuracy to be problematic. Furthermore, if you’re shooting a model with prominent eyelashes, you may end up experiencing more ‘eyelash AF’ than ‘eye AF’.

As light levels drop, accuracy suffers even further. The shot below is severely front-focused, despite light levels being at a modest 4 EV (approx). Interestingly, the camera fared better under similarly dark daylight conditions (as opposed to artificial light). The a7R III did not struggle with accuracy under these conditions.

Even at 4 EV, Eye AF autofocus accuracy can take a dive with artificial lighting. Interestingly, I had better results at similar daylight levels. Nikon Z6 | Nikkor 35/1.8 S

That’s not to say the Z6 is incapable of capturing accurately focused shots in these lighting conditions. Quite the contrary: I achieved a number of successful shots, like the ones below.

In darker conditions though, down to around -1EV, I was only getting a hit-rate of around one shots in three from the Z6, compared to the Sony a7R III, which typically missed only one or zero shots in a comparable sequence in repeated testing. The Z7 in particular would often hunt, and in Release Priority take completely out-of-focus shots. The Z6 fared better.

Furthermore, the Nikon 35 S and 50 S primes tend to sometimes hesitate to refocus, and this problem was only made more obvious in low light as the AF system tended to slow down. I’d often depress the shutter button and shoot a number of out-of-focus shots before the focus element finally even started to move to the correct position. This seems to be a problem not with Eye AF, but with the default behavior of the AF system, particularly with native lenses (often I achieved better results with adapted F-mount lenses).

In ~1 EV lighting, at best only two of these six shots are critically focused (click image to view 1:1). I had the same hit-rate with a different subject under 1 EV artificial lighting, where only one or two of six shots were critically focused. In all these instances, the eye was successfully detected by the camera. Nikon Z6 | Nikkor 35/1.8 S

Another (related) area where Eye AF, and focus in general, can struggle is under severely backlit conditions. Here, like many DSLRs, the Z6 can resort to hunting. While I was still able to get the perfectly focused shot on the left, the camera struggled, and many of the shots were misfocused like the one on the right.

In focus one moment… Nikon Z6 | Nikkor 70-200/2.8E FL ED VR	Out of focus the next. Nikon Z6 | Nikkor 70-200/2.8E FL ED VR

Conclusion

My goal in this article was to determine when and where the newly introduced Nikon Z6 / 7 Eye AF worked well, and when it didn’t. I tested the performance side-by-side with the Sony a7R III but also considered the best implementation from a usability point-of-view, which is the system in the Sony a9 and a6400.

Because this is a complicated thing to test (thanks for reading this far), I’ve broken our findings up according to four criteria, with winners indicated in bold.

• Detecting eyes: Nikon Z
• Avoiding false positives: Sony
• Eye AF ease-of-use: Sony
• Accuracy of Eye AF: Sony

Considering the updates in the Z6 and Z7 represent Nikon’s first stab at Eye AF, this is really impressive.

Our main outstanding concerns are twofold: The first is false positives, where the camera will misidentify something as a face and stick to it, and a general tendency of ‘Auto area’ AF to focus and stay focused on the background. Second, and perhaps more important: we’d like to see Eye AF integrated with a reliable and easy-to-use subject tracking mode, like 3D Tracking on the company’s own DSLRs. The only reason we might consider ‘ergonomics of Eye AF’ to be comparable is if we compare the updated Z cameras to the older Sony a7R III. The a9 and a6400, on the other hand, have the best Eye AF implementation to-date, both from a performance and usability standpoint (and as such should be a model for others to follow).

Nikon’s introduction of an effective Eye AF system is a huge step in the right direction

For now, let’s take a step back and give Nikon kudos for the fact that its improved face and eye detection allows me to get shots like the one below without having to think, whereas previously Auto Area mode may well have focused on my daughter’s arm in the foreground.

Face detect worked beautifully here to quickly nail this shot. Nikon Z7 | Nikkor 50/1.8 S

Nikon’s introduction of an effective Eye AF system is a huge step in the right direction for its mirrorless line of cameras, which even before this update, were already in my opinion the most enjoyable and photographer-friendly of today’s ILCs to shoot with.

If this firmware update is at all indicative of what’s to come from the Nikon Z-series, then we’re keen to see what’s next. The rebirth of 3D Tracking, pretty please?

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Footnote: For the sake of completeness, we also compared the updated Z6 / Z7 to Canon’s EOS R and RP. The Nikon Z cameras are considerably better at finding eyes than either of the Canons, where the eye has to be pretty big in the frame to even be identified. The updated Z-series cameras are also much more responsive when it comes to tracking the eye: like the Sony a7/R III they follow eyes around the frame quickly, whereas the EOS R / RP lag and frequently have to play ‘catch up’ with moving subjects.

Articles: Digital Photography Review (dpreview.com)