Autofocus performance

Sony FE 70-200mm F2.8 GM | ISO 800 | 1/1000 sec | F2.8
Cropped out-of-camera JPEG.

Key takeaways:

  • The a7 III shows very impressive autofocus performance at high burst speeds
  • Lock-on autofocus tracking (where the camera tracks a subject for you) has been improved over the a7 II, a7R II and a7R III
  • Leaving the autofocus sensitivity and tracking settings to default values is more than good enough for most shooting
  • Eye AF still impressive, though Sony a9 still performs better
  • Continuous autofocus can falter when shooting at smaller apertures, unless you turn off exposure preview in the menus

So the a7 III has 693 autofocus points and an array of different autofocus modes that you can utilize while the camera is motoring away at a maximum of 10 frames per second. But what good are any of these specifications if your shots end up out of focus?

But we have to admit that we were really impressed with our keeper rate on the a7 III, whether shooting at 8fps with live view or 10fps without. Sure, you lose out on absolute burst speeds when compared to dedicated sports cameras like the Sony a9, Nikon D5 and Canon EOS-1D X Mark II, but in terms of focus accuracy and reliability, the a7 III can hang with the best of them.

We took a look at how the a7 III did in our standard bike test, close-range exercise and also took it to a college soccer (football) match.

Note: On desktop computers, please use your mouse to navigate the various slideshows on this page. The left and right arrow keys will control every slideshow on this page, not only the one you've scrolled to. We're aware of the problem and are developing a fix.

Bike test

Our bicycle test is designed to help us assess the camera's ability to track a subject around the frame, as well as changing its distance. This is more akin to a small child running around a lawn. From the camera's perspective, the movement is unpredictable and the rate at which the subject approaches varies, adding to the challenge.

When we initiated tracking on Dan at a distance, the cloud of AF points more or less covered his entire upper torso; we've zoomed in on his face, as it stayed in more than acceptable focus throughout the runs.

Download the full resolution images here

As we've come to expect from Sony's latest cameras (and increasingly, interchangeable lens cameras in general), the a7 III performs with a very-nearly 100% hit rate with Dan riding straight at the camera - and it's worth noting that near the end of the selection above, the central AF area slipped from Dan's face to his shoulder, as you can see if you download the full-size burst.

This is with all autofocus settings at default values, with a 'balanced emphasis' between focus and shutter release, AF tracking sensitivity to '3' and face priority turned off.

Now, on to the weave.

Download the full resolution images here

Here we see a very good hit rate on the a7 III, shown here at 10fps (though we got similar performance at 8fps with Live View) using Lock On AF: Flexible Spot M.

We should note that at this point in the weave, Dan is extending far off into the edge of the frame, and these sorts of directional changes are the most challenging portion of this exercise - plus, at these distances, the focus elements within the lens must move more than if Dan were further away. There are a couple of images where Dan's face goes slightly soft, but the rest of his body is still in acceptable focus.

In any case, for well-isolated subjects, the Sony a7 III's autofocus performance is really impressive.

Close-up test

Our close-range, low-light exercise is designed to see how the camera tracks a subject while the photographer is the principal source of motion. It's the sort of activity you might engage in photographing your friends out at dinner, or a bar.

As with the bicycle test, the Sony a7 III performed really well here, nailing most shots at F1.4.

First, let's look at how Lock On AF did with Face Priority turned on.

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There's a few takeaways from this; first, that Face Priority struggles with glasses. The a7 III never once draws the telltale 'box' around Jeff, as it does around Carey. Second, it's that despite the accurate focus, Face Priority can often turn into 'Body Priority,' with the box growing and shrinking at will.

Next, we turned Face Priority off.

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Here, the camera treats both Carey and Jeff equally, and is equally adept at tracking their faces in this dimly lit scene.

Soccer

So, the a7 III did great in our more controlled testing, but the real world is where the rubber meets the road. We coordinated with the University of Washington to photograph a soccer game against Seattle University in our own backyard to get a sense of how the camera's Lock On subject tracking performs with more potential distractions and less isolated subjects.

Sony FE 70-200mm F2.8 GM | ISO 6400 | 1/1250 sec | F2.8
Processed and cropped in Adobe Camera Raw

One of our criticisms with Sony's a9 was that, upon initiating tracking, the AF points would jump off to another subject most of the way across the frame. Impressively, we encountered this behavior more rarely on the a7 III; when we did, it was usually in social situations where Eye AF was the better option anyway.

Here are some burst samples from the game.

Zooming, sudden deceleration

In this burst, autofocus was initiated on the Washington player, and note how, despite a good amount of speed, my zooming in the middle of the burst, and her sudden stop near the sideline, the a7 III was able to react well at its default autofocus tracking settings (AF Tracking Sensitivity set to '3'), using Lock On AF.

Dealing with distractions

For this burst, tracking was again initiated on the Washington player near the center of the frame. Note how the camera continues to keep her in focus, despite momentary distractions; this is again with default autofocus settings and using Lock On AF.

But of course, no autofocus tracking system is perfect.

Not dealing with distractions

For this final burst, we initiated tracking on the Seattle player, and as you can see, the camera was distracted by two other subjects, and never returned to the original. This is always a danger with subject tracking systems, though this was the only instance during the entire match that this occurred. If I were using a single AF area and keeping it over her myself, the camera would have returned to focusing on her once the distracting players were out of the way.

We also noticed that burst images from the a7 III were more consistently tack sharp compared to its more expensive sports-oriented sibling. With the a9, images in the middle of 20fps bursts could sometimes float in and out of critical focus, but at 10fps on the a7 III, images throughout the burst were almost universally accurately focused.

Eye AF

Eye AF continues to be one of our favorite features of Sony cameras, making it drop-dead easy to get perfectly focused portraits. We've noted, though that using Eye AF during burst shooting can be unreliable on previous cameras, which can be a pain if you're trying to, say, catch the perfect moment with your toddler.

This sequence, taken at the a7 III's maximum burst rate of 10fps, is really the ultimate autofocus torture test for a camera. There's a lot of unpredictable scene and subject and photographer movement to deal with. In other words, the hit-rate we experienced here is very impressive, likely only bested by Sony's own a9, which yields a surprisingly high Eye AF hit-rate even at 20 fps. The a7 III did slightly worse during this exercise at 8fps, possibly because of the burden of maintaining a live feed in this mode (10 fps only shows you a succession of last-shot images as you shoot).

Stopped-down Focusing

When utilizing continuous autofocus on the a7 III, one thing to bear in mind is that when using smaller apertures, the camera does not open up the lens for focusing. Because this means that the autofocus system is getting less light, and decreased phase separation between 'left' and 'right' (or 'up' and 'down') looking pixels, it can result in an image that is inaccurately focused. The example below is back-focused, but the focus inaccuracy can just as easily result in front-focus. This is unfortunately exacerbated in backlit situations, where the AF system is already stressed by a drop in subject contrast.

This image was photographed in AF-C, but for depth-of-field, the photographer wanted to use F5.6. The individual's shoulder is clearly sharper than his nose, and as such, is back-focused. A similar shot resulted in front-focus. Stop-down focusing should theoretically increase focus accuracy, but in low light or low contrast situations, it can ironically decrease accuracy.
Sony FE 24-105mm F4 G | ISO 2000 | 1/125 sec | F5.6
Photo by Dale Baskin

In our controlled testing with both the Sony a7 III and a7R III, we found that there is no native Sony FE lens that focuses wide-open in AF-C. For reference, wide-open focusing is standard practice on DSLRs (as well as Canon and Olympus mirrorless), and allows the AF system to consistently get the most light available, and the best phase separation possible, regardless of the user's settings. Look-up tables in the lens can correct for any focus shift that results from stopping the lens down.

Unfortunately, there's no workaround for this other than to revert to the slower AF-S,1 which focuses wide open.2 A commonly held misbelief is that setting 'Live View Settings Effect' to 'off' remedies the issue, but it doesn't for AF-C: all it does is force the initial focus acquisition to be done wide open, but then stops the lens down immediately thereafter, potentially throwing off focus - or causing hunting from reversion to CDAF - if continuous focus struggles at the smaller aperture. Furthermore, this disables one of the eminent advantages of mirrorless: being able to preview your exposure or depth of field.


1For some lenses, like the 85/1.4 GM, 50/1.4 GM, and 70-200 F2.8 GM, even AF-S does not force wide-open focus.

2Technically, if you're shooting at an aperture smaller than F2, AF-S will force most lenses to open up to F2, but not wider. If you're shooting faster than F2, then AF-S will focus at your shooting aperture.