Sony A9 Performance

Phenomenal burst speeds and buffer depths, though buffer clearing is incredibly slow for JPEGs.

The Sony A9's startup time (power on to first shot) was relatively fast for a mirrorless camera, but sluggish compared to most DSLRs. Switching from Play to Record mode and taking a shot was just a bit faster.

The Sony A9's full-autofocus shutter lag (with the subject at a fixed distance) was good although not exceptional, measuring in at 0.216 second in Single-area (Center) AF mode with the Sony Zeiss 35mm f/2.8 lens. This was with the mechanical shutter and electronic first curtain shutter (EFCS) enabled by default. With EFCS disabled, full AF shutter lag increased to 0.355 second. With the fully electronic shutter, full AF shutter lag was 0.231 second, a little slower than with EFCS.

When manually focused, the Sony A9's shutter lag dropped to 0.097 second with EFCS, or 0.249 second without. With the fully electronic shutter, manual focus shutter lag was 0.119 second.

The Sony A9's prefocused shutter lag was only 0.020 second with EFCS, which is very fast. Without EFCS, prefocused shutter lag increased dramatically 0.165 second, but with the fully electronic shutter, it was only 0.038 second.

To minimize the effect of different lens' focusing speed, we test AF-active shutter lag with the lens already set to the correct focal distance.

Single-shot cycle times were very fast, at less than 0.3 second for both Large/Extra Fine JPEGs and RAW + Large/Fine JPEG frames, regardless of shutter type. (Note that we no longer test single-shot mode with just RAW files, as the results are usually somewhere in between JPEG and RAW+JPEG modes. Also note that the A9 cannot capture highest quality "Extra Fine" JPEGs together with RAW, dropping to "Fine" quality JPEGs when shooting RAW+JPEG.)

Incidentally, we have confirmed single-shot uncompressed RAW files are indeed 14 bits, even with the electronic shutter, however the A9's lossy compression reduces the effective bit depth to 13 bits in single-shot mode in addition to being delta-encoded.

With the mechanical shutter, the Sony A9's top burst speed is a claimed 5 frames per second no matter the file type, and we were able to confirm that in the lab. With the electronic shutter, the top burst speed is 20 frames per second for JPEGs, compressed RAW or compressed RAW+JPEG files, which we also confirmed in our tests. When shooting uncompressed RAW files, the top burst speed dropped to about 12 frames per second, as advertised. We have also determined that all continuous mode RAW files are 12 bits, whether compressed or uncompressed.

Buffer depths were excellent, ranging from a minimum of 116 uncompressed RAW+JPEG files at 12 frames per second in the worst case to unlimited frames (limited only by the capacity of the card) when shooting compressed RAW at 5 fps with the mechanical shutter. At the top speed of 20 fps, the Sony A9 was able to shoot 364 JPEGs, 240 compressed RAW or 225 compressed RAW+JPEG files before slowing, which is within a couple frames of their specs.

Unfortunately, even with one of the fastest UHS-II cards on the market (a Lexar Pro 2000x UHS-II SDXC card) installed in the one slot that supports UHS-II, clearing the buffer can take a long time, particularly with JPEG files. The worst-case buffer clearing time in our tests was a glacial 254 seconds or over 4.2 minutes after shooting a max-length burst of best quality JPEGs at 5 fps, which fell slightly to 236 seconds after shooting 364 JPEGs at 20 fps. Buffer clearing was faster when shooting RAW files, but could still take well over half a minute for long bursts. (It appears the A9 is doing some JPEG processing while it writes them to the card as RAW files are written to the card roughly 4 to 5x faster than JPEGs by our estimation.) Only when shooting compressed RAW at 5 fps was the camera able to clear its buffer in near real-time, essentially keeping up with the capture rate. The Sony A9 does let you change some settings and view just-shot images while the buffer is clearing, however access to the menu system is unavailable.

Bottom line, the Sony A9 is capable of some astonishing performance with up to a class-leading 20 fps burst speed with very deep buffers, however there are some caveats to consider including slow buffer clearing (particularly with JPEG files which are favored by many pro sports shooters), menu lockout during clearing, and needing to use e-shutter and compressed RAW to attain that speed. Power-on to first shot was a bit sluggish compared to a DSLR, though, and while single-shot AF speeds were good, they were nothing to write home about. Shutter lag with EFCS or e-shutter was however very low and cycle times were incredibly fast.

Battery Life
Very good battery life for a mirrorless camera.

The Sony A9 uses a custom NP-FZ100 rechargeable lithium-ion battery pack for power, and comes with a single battery, a dedicated battery charger and an AC adapter for in-camera charging via USB. While CIPA-rated battery life is well above average for a mirrorless camera, it's still well below most prosumer and pro DSLRs when using their optical viewfinders. We recommend purchasing a second battery and consider getting the optional VG-C3EM portrait battery grip which doubles battery life with a second battery installed.

The table above shows the number of shots the camera is capable of (on a fully-charged rechargeable battery), based on CIPA battery-life and/or manufacturer standard test conditions.

(Interested readers can find an English translation of the CIPA DC-002 standards document here. (180K PDF document))