Autofocus performance

Key takeaways:

  • Subject tracking reliability lags behind both Nikon's industry-leading 3D AF Tracking, found in its DSLRs, and also several of its mirrorless competitors.
  • Single point AF-C performance is good at the camera's top burst speed, but the buffer slows down during burst shooting after only several seconds.
  • AF-C performance proved reliable for shooting indoor sports
  • AF-S performance is snappy and accurate in good light. Since focus is performed by the image sensor, you'll typically get more critically sharp images than you might from a DSLR for static subjects.
  • Low light AF sensitivity is 2-3 stops worse than the competition - this can cause hunting in very dim lighting or when shooting back-lit subjects in AF-C mode.
  • Face Detect - available in the Auto-Area mode - is reliable at tracking static portrait subjects, but can be confused by movement. We prefer the reliability of Sony's Eye AF.
  • Auto Area AF mode occasionally gets stuck to the background - the opposite of what we'd expect.

Overall AF conclusion

The Nikon Z7 has vast AF coverage, is precise in its focus on static subjects and accurate in its focus on moving subjects (using a single point), but its AF tracking of moving subjects is not as reliable as the 3D-Tracking mode found in Nikon DSLRs.

For some time, we've considered Nikon DSLR autofocus the best in the business both in terms of tracking operability and reliability. But the Z7, while capable, falls short of meeting this high standard, despite its pro-level price. It also falls far short of the bar set by class-leading mirrorless autofocus features, like Sony's Lock-on AF.

AF-C performance

For our continuous AF test, we use a single point to test the camera's ability to determine the distance of an approaching subject, and drive the lens to the correct location.

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Both of our telephoto AF tests were shot using a Nikon 70-200mm f/2.8E FL ED VR adapted to the Nikon Z7.

The Z7 can easily maintain focus on a subject when using a single point with a nearly 100% hit rate. We did this test at the camera's top burst rate of 9 fps (High+, JPEG only) which locks the exposure on the first frame. It's worth noting we also ran this test at 5.5 fps (High, JPEG only) with similar results. In both cases, the buffer kicked in after about 4 seconds, slowing the burst speed down.

We tried this test with the camera set to both 'focus' priority and 'release' priority with similar results.

AF-C while shooting wrestling

Edited to taste in ACR.
ISO 8000 | 1/1000 sec | F4 | Shot with the Z 24-70mm F4 S lens at 24mm.

Sure the Z7 did well in our bike test, but do these results translate to the real world? We brought it to a semi-professional wrestling match to find out. And a 95% + hit rate confirms they do indeed. Of about 1000 images shot, less than 50 were out of focus.

It's worth noting that we shot the wrestling match with the comparatively slower, wider, native S 24-70mm F4. At F4, depth of field is relatively generous, especially at wider focal lengths. We were also working in a much darker environment, and rather than using a single point in the center, most of the match was shot using the camera's larger 'Dynamic Area' off center.

Edited to taste in ACR.
ISO 3600 | 1/1000 sec | F4 | Shot with the Z 24-70mm F4 S lens at 24mm.

AF-C with tracking - performance

Now on to our subject tracking performance test, where we expect the camera to recognize its subject and follow it as it moves around the scene (adding significantly complexity to its task).

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Test shot with the camera set to both 'focus' priority.

The above roll-over does a good job summing up our experience using the Z7 to track. The example starts midway through the run - all the shots prior those those shown here were critically sharp - but then for seemingly no reason, the Z7 loses focus on the cyclist, settling on the background instead. This behavior proved pervasive throughout many of our subject tracking bike runs. We also noted a similar tendency of the camera to jump to the background when using Face Detect in Auto Area mode, but more on that below.

In short, the only thing consistent about the Z7's subject tracking performance is just how inconsistent it is.

It is also worth mentioning that AF tracking performance seems dependent on how well the camera initially recognizes the subject. In the case of our bike test, we shoot multiple approaches, and in those where the cyclist started out small in the frame, the camera seemed to struggle to recognize him it as he approached. Fairly often we noticed the camera picking a slightly different object in the frame rather than the object we intended to track, which added to our frustrations regarding Z7 subject tracking.

Face Detect and low light AF-C - performance

Below is our standard low light Face Detect test, meant to simulate photographing friends or family in an indoor environment with dim lighting.

Sample photoSample photoSample photoSample photoSample photo

This test was shot using the Nikon Z 35mm f/1.8 S lens at F1.8 in Auto ISO.

The hit rate for this test is good, only about 2 of the 15 photos are totally out of focus, but there are some caveats. For this test, we had to set the camera to 'Release' priority instead of 'Focus' priority to avoid the slow acquisition speeds in the former. The result of doing so is that the autofocus keeps up, but doesn't always deliver critically sharp images.

Also our subjects in this example are relatively static and side-lit, making their faces contrasty targets, and there aren't many distracting elements around them. Add in an erratically moving subject or a more complex scene and - despite similar total illumination levels - the face detect hit rate takes a nosedive...

Face Detect can be useful when subjects are static, but it can utterly fail when your subject is moving around. In this example the camera decided to prioritize the balloon instead of the toddler in not just one, but tens of shots.

ISO 2800 | 1/250 sec | F1.8 | Shot with the Nikon Z 35mm F1.8 S
Photo by Rishi Sanyal

In multiple real-world scenarios, like the one above, we observed Face Detect mistaking distant inanimate objects for faces. When this occurs, the camera is then reticent to refocus on something closer - even an actual, real face - taking up a portion of the frame.

When it comes to moving subjects, what is especially frustrating is that even when the camera seemingly can stick to a face - as proven by a red box hovering over them - often it just can't drive AF fast or accurately enough to actually maintain focus. In the scenario above, of the shots we thought we had in focus, most (~80%) weren't critically sharp in 1:1 viewing.

AF-C in very low-light - performance

An AF-C hunt caused this image to be out of focus.
ISO 12800 | 1/500 sec | F2.8 | Shot with the Nikon Z 35mm F1.8 S

One constant frustration we observed while field testing the Z7 is the camera's tendency to hunt in AF-C when shooting in very low light or back-lit subjects. In controlled testing we found the camera started to hunt noticeably in light levels between 0 and -1EV when using the 35mm F1.8 S lens. But even in light levels slightly higher - like in the example above - AF hunting caused missed shots.

Changing the camera's AF-C priority from 'Focus' to 'Release' Priority helps to cut down on AF hunting in low light, but at the cost of critically sharp photos. And in severely back-lit scenarios, more often than not the Z7 simply cannot focus at all.