Performance

Performance is what the Sony a9 is really all about. Compared to an a7R II, Sony's claiming the a9 sensor readout is 6 times faster than an a7R II with its backside illuminated architecture, and 20 times faster than the a7 II which uses a more conventional front-side illuminated sensor.

When shooting 4K video, Sony says the a9 uses 40% less power consumption than the a7R II, even though it is oversampling from a 6K readout of the sensor. Startup times are 30% faster, and the camera feels generally snappier to use than previous Sony full-frame models.

One aspect of the a9 that may leave users scratching their heads concerns the use of SD cards, with only one UHS-II compatible slot. Sure, XQD cards are physically larger, but they're incredibly fast - you'll never have to wait for a Nikon D5 or D500 to finish writing when you're done shooting. Thankfully, you can enter playback while images are being written and see how many are left to go, but you can't enter the menus to change any settings there.

In terms of burst shooting, one of the headline features of the a9 is that it shoots at 20fps with full autofocus and autoexposure - unless you're shooting uncompressed Raw, which results in the camera dropping to 12fps. So you'll have to put up with Sony's localized compression that can lead to artifacts if you want 20 fps (we'd like to see a lossless compressed Raw mode that still allows the camera to hit 20 fps). Now let's say, somehow, you hit the huge buffer on the a9. Here's how long you'll need to wait before you can go into the menus and change things; take particular note of the effect processing the JPEGs can have.

Quality Number of images captured Buffer clear time
Uncompressed Raw (12fps) 132 0:32
Uncompressed Raw + JPEG (12fps) 124 0:39
Compressed Raw 245 0:38
Compressed Raw + JPEG

236

0:55
JPEG - Xtra Fine

368

2:05
JPEG - Fine

365

1:05

If you are a photographer that utilizes speedlights for burst shooting at events, for example, be aware that the Sony a9 is not capable of syncing up with an external flash for its electronic shutter; this limits you to 5fps with the mechanical shutter. Sony's flash ecosystem also precludes the possibility of using a red/IR assist beam on an external flash to aid with autofocus, a shortcoming not present on Canon and Nikon systems (the a9 can activate annoying LED assist lamps on some flashes though). We'd like to see Sony engineer a solution for fast AF in low light using perhaps a blue (since the masked phase-detect pixels are blue), non-distracting grid pattern projected by a flash or radio trigger - this is often important for event shoots.

Lastly, you happen to turn the camera off while it's writing to the card, the camera will power down, though the card write light will stay illuminated until it's done - and if you power it back on, the camera will boot up and function as normal. Some other fast-shooting cameras, such as the Leica SL, don't let you do this, requiring you to wait until the camera has finished writing and then reboot if you hit the power switch before a burst is done recording.

Video

Given what the rest of Sony's mirrorless lineup is capable of, it should come as no surprise that the Sony a9 is capable of 4K recording internally; in an interview we had with Sony, they claimed that it offers the 'highest 4K movie image quality of any FF ILC.'

At the heart of this claim is the brand-new stacked CMOS sensor that allows the a9 to capture UHD 4K video using the full width of its sensor, still with reduced rolling shutter. This means its 24p footage is made up from 6000 x 3376 pixels: oversampling the scene by 1.56x in each direction, for more detailed footage with less risk of moire. 30p footage is oversampled 1.26x in each direction, and comes with a 1.2x crop, but shows less rolling shutter. The camera also has the headphone and mic sockets, and option to fit an adapter for twin XLR mic input.

Sony's claims regarding image quality appears not to be overstated, at least in terms of 4K detail capture, with the a9 showing better results than the a7S II and a7R II; it also puts up a good showing against the (also oversampled) a6500. Switch to 1080p, though, and the a9 lags far behind the a7S II and a7R II, and again looks somewhat comparable to the a6500. At the very least, switching the camera into S&Q mode and recording slow motion video doesn't seem to further negatively impact quality to a meaningful degree.

Rather strangely, though, Sony has omitted picture profiles from the a9, including S-Log2 and 3, and ITU 709, all of which serve to maximize the dynamic range available for video recording. This is a feature that first showed up on the a7S, a7 II and RX100 IV, and it's strange to see such a high-end product missing a feature that has become so common on lower-end models.

In terms of autofocus during video, the only method of subject tracking is the older Center Lock-on AF implementation, which does allow 'tap-to-track' functionality, but isn't as sticky nor reliable as Lock-On AF in stills-shooting mode. It's also cumbersome to use in practice, as we show in this Sony a6500 video. Fortunately, the camera's 'Wide' AF area mode works extremely well given a fairly well-defined subject.

Lastly, we missed several clips because of the pronounced lag once you switch into video mode - give the camera about 2-3 seconds to fully switch, or else your press of the record button isn't likely to have any actual effect.

In any case, how does the footage actually look, even without the benefit of S-Log? Pretty darn good.

Video sample

For this sample, the Sony a9 was set to F16, 1/50 sec with Auto ISO. All shots are handheld and image stabilization is turned on.

We also ran the Sony a9 in the camera's 'S&Q' (slow and quick) mode, which allows you to shoot 1080/120p footage with autofocus. The footage looks beautiful, and though we have both samples of when autofocus worked and failed, it does work well much of the time.