Autofocus

Sony's eye-detection algorithms are as good as ever. Out-of-camera JPEG.
ISO 400 | 1/320 sec | F2.8 | Sony FE 135mm F1.8 GM

Key takeaways:

  • Market-leading autofocus tracking implementation and performance
  • Tracking is reliable for all kinds of subjects from portraits to fast-action sports
  • Animal Priority works well for cats, dogs and also some farm animals

System overview

Sony's a9 II uses the company's latest autofocus implementation, which we've found to be incredibly effective and easy to use in almost any situation from family photography to pro sports. We've covered it in detail elsewhere, but here's a quick refresher.

The a9 II has 693 autofocus points offering 93% coverage of the sensor. You can, of course, track subjects yourself by keeping an array of AF areas over your target, but most high-end cameras are capable of this; it's letting the camera recognize and track a subject around the frame, thereby freeing you up to concentrate on capturing the right moment, that is the greater challenge.

As far as setup goes, we recommend keeping the camera in AF-C and using the 'Tracking: Flexible Spot M' focus area with face / eye priority enabled. This will allow you to place an AF area over the subject of your choosing, and the a9 II will track it tenaciously with a green box; if the subject happens to be a human, the camera will automatically transition to face and eye detection as it's able, and if it loses the subject's face or eye, it won't automatically jump off to something else. It's a powerful yet simple way of working.

In many cases, you'll find you just don't have to mess with your autofocus settings again, though if you're doing animal photography, you'll want to enable 'animal priority' to get the camera to most reliably lock focus on animal eyes. We've also been using real-time tracking for fast-action sports for a while now, and it's truly excellent.

Autofocus system performance

To test continuous AF performance, we first try to shoot a subject approaching at a steady speed using the central AF point. This lets us see how good the camera is at assessing subject distance and whether it can drive its lens to that point quickly.

Straight-on
Weave
All images captured using the Sony 70-200mm F2.8 GM at 200mm.

We then have the subject weave across the camera's AF region in a way the camera can't predict. This has the advantage that the approach rate varies as the subject changes direction. For this test we enable one of its tracking modes, so it needs to identify and follow a subject around the scene, as well as trying to keep it in focus.

At 20 fps using the silent shutter, the camera basically turns in a 100% hit-rate. With the mechanical shutter at 10 fps, we see a very slight reduction in critical hit rate, but there wasn't a single image that we'd call unusable.

The a9 II's tracking is excellent for just about any subject. Processed and cropped in Adobe Camera Raw.
ISO 12800 | 1/1000 sec | F2.8 | Sony FE 400mm F2.8 GM

In more challenging sporting situations, tracking is similarly reliable. And once you get the camera set up, you will find that you rarely need to change settings, though you can adjust the camera's 'AF Tracking Sensitivity' if needed. On a scale of 1 (Locked On) to 5 (Responsive), this lets you tell the camera how willing it should be to abandon a subject it's tracking if another subject gets in the way – say, if a defender comes between you and an attacking player in football. While we found the default setting of 3 (Standard) to work well much of the time, setting the camera to 1 (Locked On) will make it less likely that the tracking box jumps off to the defender from the attacking player.

For candid portraiture and documentary work, we tended to keep 'people priority' enabled so you don't have to worry much about the camera getting tripped up by foreground elements. This is great if you're a fan of having a bunch of out-of-focus stuff between you and your subject for context.

The AF system didn't get tripped up at all by the grass and the fence in the foreground of this image. Out-of-camera JPEG.
ISO 100 | 1/160 sec | F2.8 | Sony 70-200mm F2.8 GM @ 70mm

Against DSLR competition, the a9 II's electronic viewfinder rewards you with far greater autofocus coverage than a Nikon D5 or Canon EOS-1D X Mark III, though we found the Nikon D5's autofocus tracking to be almost as sticky as Sony's. In live view, we found that the EOS-1D X Mark III just about closes the gap with the a9 II with truly excellent tracking and face / eye detection, but again, that's only in live view. So if you're after the best overall autofocus performance money can buy whether shooting through the viewfinder or on the rear screen, the a9 II is the camera for you – especially with its lag-free, blackout-free burst shooting if you can use the electronic shutter.