Autofocus Evaluation

With the sports-focused a9, Sony's shown that they know a thing or two about how to design a really successful autofocus system; they also claim they've taken what they've learned from that camera to improve performance on the a7R III. While the a7R III uses the same sensor and number of AF points as its predecessor, it's capable of shooting twice as fast, and Sony claims that tracking performance is twice as good as well.

Let's see how that bears out in our testing and real-world experience.

Long range depth tracking

When using a single, centrally located point placed over an approaching subject, it's no surprise that the a7R III does very well, whether shooting at 8fps with Live View or its maximum speed of 10 fps. As we'd expect from a camera of this caliber, the hit rate is basically 100%.

With Dan riding straight at the camera and the AF point placed over his vest, the a7R III ably kept him in accurate focus.

Long range subject tracking

Our subject tracking evaluation shows off a couple of interesting aspects of the a7R III's Lock-On AF implementation.

For the most part, the camera did extremely well with identifying our subject and sticking to him throughout the run, though performed slightly better overall at 10fps instead of 8fps with live view - more on this later. We would expect broadly good performance here, considering Dan is well isolated in depth from any background elements, making him easy to identify as the subject. Unfortunately, the majority of images are just slightly soft - certainly not enough to be unusable by any means, but 42.4MP of resolution can be pretty unforgiving at 100%.

In any case, it appears that since the tracking 'box' makes up most of Dan's upper half, there are necessarily parts of him that are both closer to and further from the camera than the front of his vest. In essence then, the camera (versus the photographer) makes a judgment call about what portion of the subject should be in critical focus.

Take a look at this sample rollover to see the difference between the soft images, and the tack-sharp ones, taken at 10fps:

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This is a good representative sample of the many runs we did - if you're not pixel-peeping, or if you're perhaps creating images for web publishing, this won't likely be a problem - but 42MP might be overkill for such a use.

We mentioned earlier that the camera generally performed better at 10fps than 8fps with Live View. When in 8fps, we noticed the a7R III occasionally stuttering as it temporarily lost Dan before reacquiring - you can see this behavior in the below rollover, where Dan makes a big jump between images three and four:

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Let's put this all into context, though. The a7R III is one of a very few number of cameras on the market able to offer supremely impressive autofocus performance combined with an incredibly high pixel count. In just two years, Sony has doubled the performance of its resolution-focused flagship, and that's nothing to sneeze at.

With that said, let's take a look at how the a7R III does in our low light autofocus exercise.

Close-up / Low light

In addition to evaluating the a7R III's AF capability at a distance, we also want to know how it handles close-range subjects - so we simulated a dimly-lit social setting and put both Eye AF and Lock-on AF to the test to see which performs better. Note: this demo was shot using the Sony Distagon T* FE 35mm F1.4 ZA lens. First up, Lock On AF:

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The results are decent, nearly 3/4 of the shots are sharper or close to sharp. However, as you can see in the video, the camera visibly loses the subject several times. Let's see how Eye AF does:

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We've long been impressed by how good Eye AF is on high-end Sony cameras and the results from this demonstration solidify in our mind that Eye AF is more reliable when photographing people at a close-range in low-light than the Lock-On AF modes - about 85% of the images are acceptably sharp. Also, at no point does the camera seem to completely lose the subjects, which is reassuring compared to Lock-on.

Real world results

Though we've seen that Lock On AF works fairly well given our well-isolated bicycle subject, we also had the opportunity to see how the a7R III copes with more complex scenes - and many more bicycles.

Well, at least the leaves are awfully sharp.

For this scene, DPReview's Richard Butler placed the AF area in the top left of the frame, and kept it over the riders as he initiated tracking. Most of the time though, the tracking box would simply float off to the background, ignoring the rider flying through the scene. This happened repeatedly in this spot.

However, this isn't the end of the story.

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These guys seem awfully happy for being competitors in a strenuous cyclocross race. Images selected from longer, high-speed burst.

In this situation, Richard initiated tracking on the rider further back, and the a7R III continued to track this rider even as the other rider crossed in front. This is the same sort of behavior we see from Nikon's class-leading 3D Tracking, and it's impressive to say the least.

So while it seems that Lock On is certainly capable of great results, it can't necessarily be depended on all of the time. For casual shooting, it's a nice feature to have - but if you absolutely need to capture a crucial moment, it's best to avoid Lock On and go old school by manually placing your AF point where you want it.