Autofocus impressions

That's some serious AF coverage. 93% to be exact.

[UPDATE: July 2019] Sony released firmware v5.0 that brought major improvements to the camera's autofocus system in April 2019. After testing, we found the performance enhancements make the a9's autofocus system industry-leading. Our original concerns were around 'lock-on AF', which has now been replaced by 'real-time tracking', and are therefore no longer relevant. Read more here.

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The Sony a9 comes with a whopping 693 phase detection autofocus points offering 93% coverage, a vast improvement over the a7R II. AF calculations have been sped up to 60 fps as well, with 25% faster initial acquisition, focusing in one-stop darker conditions (-3 EV with a F2.0 lens), and 30% faster Eye AF compared to the a7R II.

Our initial impressions of this revamped system are extremely positive. We've found Eye AF to be stickier, and it reacts faster than on the a7R II. The camera's 'Wide' area mode still works great for casual shooting and is incredibly fast at determining a subject to track. We tended to keep our cameras on the 'Lock-On: Flexible Spot M' so we could tell the camera our intended subject. Lock-on is noticeably quicker to initiate tracking than Sony's own a7R II, but still not as (visibly) instantaneous as a Nikon D5.

At the press event, we found that Lock-on even worked well enough for quick reactionary shots (i.e. mashing the button down) while an object was already in motion, and then accurately tracking that subject even if we changed framing before the autofocus points had lit up to indicate tracking had indeed begun. So while 'Wide' (completely auto) appeared to react the quickest, we still had a lot of success with specifying the subject in Lock-on AF modes, particularly with singular subjects.

Every now and then during these shooting events, Lock On appeared a mind of its own and jumps to another subject, but more often than not it returned to it, or stuck with it throughout. In the few instances it failed we quickly switched to Wide or a single point to try and rescue the shot, which is as easy as a button press thanks to the a9's extensive customization.

This pole vaulter was already well under way when we initiated autofocus on him, but the camera tracked well. I cropped to get the composition we wanted and still ended up with a 15MP image.
Sony FE 70-200mm F2.8 GM | ISO 2000 | 1/1000 sec | F2.8
Photo by Carey Rose

Speaking of which: new to the a9 is the ability to assign different autofocus area modes plus autofocus activation (among other options) to different custom buttons, just like you can on a Nikon D5 (and to a limited degree on a Canon 1D X II). This feature is called 'Recall Custom hold,' and allows you to react more quickly as your surroundings change; our technical editor Rishi Sanyal goes over the details of this new capability in the video below.

But now, back to autofocus tracking. The a9 offers some seriously impressive autofocus tracking performance, even with subjects being occasionally blocked by other objects or other subjects. But don't just take our word for it - check out three examples in the video below.

For the first time on a Sony, the a9 offers customizable autofocus tracking sensitivity on a scale of 1 to 5, where 1 is the least likely to refocus as a distraction comes between you and your subject, and 5, where it is most likely to refocus on a new subject entering the area where the camera is tracking.

Our initial testing shows 1 to take around three seconds to refocus, while 5 refocuses almost instantly. Leaving the setting at 3 results in a good balance, refocusing very quickly if the distraction is close in distance to the initial subject, and waits a little longer if there's a big difference in distance.

Interestingly, there's no setting to tell the camera how erratic or constant the acceleration (or deceleration) of your subject is - a parameter most DSLRs allow you to specify. Sony tells us this is because their system needn't rely as much on prediction, since it can simply react to the subject thanks to its 60 fps AF measurements. Our initial impressions line up with these claims: every now and then the camera might lose the subject, but it is capable of returning quickly, something we can't say about the Canon 1D X II when its predictive algorithm fails.

Autofocus and slow motion video

We also had a chance to shoot a number of 1080/120p slow motion clips during our time with the camera at Sony's announcement. You have the option of saving out either a 5x slow motion file (24 fps output) or 4x slow motion file (30 fps output). We opted for the latter to minimize judder.

Because there is no 'tap-to-track' autofocus implementation in Sony's 'S&Q' (Slow and Quick) video mode, you have to either use 'Wide' and let the camera decide what to focus on, or use a single point of your choosing and keep it over your subject. Our complaint extends to general video as well: the only sensible tap-to-track method is 'Center Lock-on AF', which is cumbersome to engage, and uses an old, unreliable tracking algorithm (so don't expect Dual Pixel-esque customizability when it comes to subject tracking in video).

While 'Wide' can work very well, there are times where it can behave unpredictably, forcing you to use a flexible spot mode to guarantee accurate focus. Check it out for yourself in our slow motion sample reel below. But let's keep some important perspective here: the camera is quite capable of refocusing on running athletes at 120 fps for effective focus in 4-5x slow motion video.

That's kind of amazing.