Real-world autofocus performance

by Carey Rose - Edited from content originally published here on May 18, 2016.

Motocross practice

For someone as obsessed with motorcycles as I am, it’s almost embarrassing to admit that this was my first time watching motocross in person, much less photographing it. And even though we were shooting a Sunday practice session, it proved a good test for Nikon’s flagship sports shooting machine. As riders brapped and blipped their engines, rocketing around the track at over 40 mph, I snapped and clacked the D5 away at 12 fps nearly the whole time. You just don’t realize how nice all those frames per second are until you really – truly – need them.

Panning shots - they look great, but because of the deep depth-of-field caused by small apertures and potential subject blur from slower shutter speeds, they're not the best for testing autofocus accuracy. Photographed in Auto Area AF. Photo by Carey Rose. Nikon 24-70 F2.8E VR @ 38mm | F11 | 1/250 sec | ISO 100

But before we get to the burst rate and the photos, it's best to make sure you've read about all the autofocus modes on the previous page for context. The continuous autofocus modes I chose to try out were 3D Tracking, single-point, Group Area AF and Auto Area AF. 

It goes without saying that all of these modes, despite how computationally intensive they may be for the D5, work perfectly well at its full burst rate (not mirror lock-up mode). Actually, it's not as obvious as I'm making it sound: a D750 or D810, while excellent at subject tracking when not shooting (that is, for single shots), can falter during bursts, much like a Sony a7R II. And as someone who is used to 5 fps bodies, the higher frame rate was quite an eye-opener.

12 fps

After some quick and informal testing, I soon started to take 12fps for granted. Slowing down the D5 in ‘Continuous Low’ mode to 6fps to simulate a less sports-oriented body was torturous. Predictably, instead of getting a solid six-to-eight shots of a rider flying past me with wide-ish framing, I’d get maybe three. I was often left wanting an additional shot in-between the few that I managed to get, and because of this, I ended up trying to get just a single shot at the right moment and hoping that my timing worked out. It often didn’t. Back to 12fps mode for me.

A high frame rate gives you more compositional options in situations such as this, where two riders are constantly changing their positions relative to each other. Photo by Carey Rose. Nikon 70-200 F2.8G VR II @ 200mm | F5.6 | 1/1250 sec | ISO 400

Following and focusing with single-point AF

But of course, 12fps is useless if you can’t see what you’re shooting. The good news is that the viewfinder blackout is so ludicrously short on the D5 that I was able to pan and follow a fast-moving rider at a very close distance with ease. Nikon’s 3D Tracking worked well (more on that later), but because I could see so clearly in 'real time' even at 12fps, using single-point continuous autofocus and just keeping a point over my subject was a completely viable option when panning and netted a high degree of ‘keepers.’ What’s more, the autofocus spread is so generous on the D5 that I rarely felt compositionally constrained by picking a single point to keep over my subject.

Of course, for the sake of some variety, sometimes it's best not to follow the action and just let it pass you by. Photo by Carey Rose. Nikon 300m F4 PF | F5.6 | 1/500 sec | ISO 100

Group AF

Group AF on the D5 works similarly to single-point, but with the idea that a tight group of points will afford you a little more sloppiness in point placement than the higher precision one point alone requires. The idea is great in principle and it usually worked well, but there were a handful of times where I let a part of the group stray off the rider, and the camera quickly readjusted to focus on the background. Part of this is probably due to the fact that I had the AF system set up for ‘erratic’ subjects, and 'Blocked shot AF response' to default (3), since 3D tracking and single-point worked so well in this mode, but in any case I tended to avoid Group AF for the rest of this shoot. It's a great focus mode though for when you expect a subject to suddenly appear in one part of the frame: make sure AF is enabled for your shutter button, wait for it, then when the subject is under the general area of your selected group, jam the shutter button to both initiate AF and take the shot.

Birds Motorcycles in flight. Photo by Carey Rose. Nikon AF-S 300mm F4 PF | F4 | 1/1600 sec | ISO 100

3D Tracking

One of the most exciting autofocus developments for DSLRs in recent years, Nikon’s 3D Tracking, worked as well as I have come to expect with only a single exception. When at wider focal lengths and attempting to initiate tracking on a rider at a distance, the D5 would usually just not be able to find my subject. The user manual reflects this though, saying that the camera collects color information from focus points surrounding the one you've chosen, storing that information and using it to initiate tracking.

So with a distant rider, the D5 was seeing mostly the dirt color, despite the bright colored clothing of my intended subject. Put another way: the metering sensor was not high enough in resolution to discern a small rider from its immediate background. In any case, if I let the subject get a little closer, or if I used longer lenses that produce inherently shallower depth-of-field, 3D Tracking proved itself to be pretty magical, constantly re-focusing and re-positioning the autofocus point in the viewfinder even when I was shooting at 12fps.

Nikon's 3D Tracking did a great job of tracking this rider with a single AF point pegged to his riding suit. Photo by Carey Rose. Nikon AF-S 300mm F4 PF | F4 | 1/1000 sec | ISO 100

Auto Area AF

The last mode I experimented with was Auto Area AF, which is usually a mode that I tell people to avoid using. The D5 might just change my mind on that one. The camera was able to find a moving subject and hit it with anywhere from one to nine AF points almost every single time.

1 2 3 4 5

In the above series of (unedited) images, Auto Area directed the camera to focus on the background first. But then in the middle of that 12fps burst, focus snapped to the rider flying through the air in front of me within two frames. I generally prefer a higher degree of control than Auto offers, but I can see this mode being genuinely helpful if you have milliseconds to get a shot and you don’t have time to place an autofocus point manually.

All those buttons

As we've covered on our 'Controls & Setup' page, one of the best parts of the new D5 (and the D500) is the level of button customization regarding autofocus modes. I am a back-button AF shooter, as I do sometimes like to pre-focus and wait for a subject to enter the frame without having to switch into manual focus.

But even with the shutter button decoupled from any autofocus functionality whatsoever, I can assign AF-ON to be 3D Tracking, then assign the Fn1 button on the front of the camera (under my ring finger) to switch to single-point continuous autofocus, and then also assign a full press of the AF joystick to switch into Auto Area mode. Counting manual focus since the shutter button is decoupled, I’ve got four different focus modes at my fingertips without even shifting my grip. This is incredibly handy as I often found myself changing AF modes depending on my lens, my position and the riders' movement. This versatility in instantly switching AF area modes is a feature you won't find on any other camera on the market, save for Nikon's own D500.

Having watched this rider come around this corner a number of times, I wanted focus on just how much dirt he kicked up as he plowed through. Having de-coupled autofocus and my shutter button, I pre-focused just behind where his rear tire is, shot a burst as he entered and exited the viewfinder with the tight framing I wanted and I didn't have to worry about the focus shifting or missing (an admittedly minor concern with the D5). Photo by Carey Rose. Nikon 300mm F4 PF | F4 | 1/2000 sec | ISO 200

The wrap

In all, the Nikon D5 is a fantastic machine that proved to be more than a match for shooting motocross with a variety of lenses. Admittedly, this test is more of a stress on the depth tracking abilities of the camera, and less so its RGB metering sensor-based subject tracking, but I still came away impressed, particularly with the Auto Area AF.*

Nikon D5, you've earned yourself a beer. Photo by Carey Rose. Nikon 24-70 F2.8E VR @ 24mm | F8 | 1/200 sec | ISO 100

But since the Nikon D5 did so well at motocross, we decided to try something else. We had the opportunity to shoot it at an evening club soccer match in Seattle's Greenlake neighborhood. Let's see how it fared.

* We say this particular scenario was less of a stress on the RGB metering sensor-based subject tracking because riders isolated against a much further background tend to not be a stressful subject tracking test. That's because the camera can discern your subject well based on distance - the rider is surrounded by objects at very different distances, so it's easier for the camera to automatically track it around the frame just by looking for a subject at or near the distance of the initial subject. Trickier is to track the eye of a bride at 24mm F1.4, where her eye appears at similar distances as her ear, or her nearby groom. And yet, even here, Nikon 3D tracking performs well, unlike Canon iTR.