Sony A7 III Performance

Generally very good performance for its class, though startup time and buffer clearing are sluggish.

The Sony A7 III's startup time (power on to first shot) was a little sluggish for a mirrorless camera, and much slower than most DSLRs. Switching from Play to Record mode and taking a shot was faster, but still a bit slow compared to most ILCs.

The Sony A7 III's full-autofocus shutter lag (with the subject at a fixed distance) was good, measuring in at 0.196 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 0.265 second. With the fully electronic shutter, full AF shutter lag increased to 0.325 second.

When manually focused, the Sony A7 III's shutter lag dropped to 0.125 second with EFCS, and 0.192 second without. With the fully electronic shutter, manual focus shutter lag was 0.182 second.

The Sony A7 III's prefocused shutter lag was only 0.023 second with EFCS, which is very fast. Without EFCS, prefocused shutter lag increased to 0.101 second, but with the fully electronic shutter, it was 0.082 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 pretty fast, at just under 0.6 second for both Large/Extra Fine JPEGs and RAW + Large/Extra Fine JPEG frames. (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.)

In Continuous Hi+ mode, the Sony A7 III's top burst speed is a claimed 10 frames per second, and that's with continuous AF/AE. In the lab, the A7 III tested very close to that spec, at about 9.9 frames per second with just JPEGs, and about 9.7 frames per second with uncompressed RAW files. In Continuous Hi mode which updates the viewfinder image between captured frames for easier subject tracking, the Sony A7 III essentially met its spec at about 8.0 frames per second. The A7 III also offers Mid and Lo Continuous mode settings rated at 6.0 and 3.0 fps respectively.

Buffer depths were excellent when shooting best quality JPEGs, at 163 frames in Hi+ mode, and 176 frames in Hi mode in our tests. Uncompressed RAW buffer depths were pretty good, ranging from 30 to 34 frames depending on the mode. Sony claims buffer depths increase to between 79 and 89 frames respectively when shooting compressed RAW or RAW+JPEG frames, however we did not test compressed RAW performance in the lab. Sadly, the Sony A7 III still does not offer a losslessly compressed RAW option.

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 still took a long time, particularly with JPEG files. The worst-case buffer clearing time in our tests was 54 seconds after a max-length burst of best quality JPEGs at 8 fps, which fell slightly to 50 seconds after shooting 163 JPEGs at 10 fps. Buffer clearing was faster when shooting RAW files, but still took 26 to 36 seconds to clear after long bursts. The A7 Mark III does let you change some settings, access the menus and view just-shot images while the buffer is clearing, though.

Bottom line, the Sony A7 III generally offers very good performance for the class with good AF speeds, low shutter lag, class-leading burst speeds and deep buffers, however buffer clearing can be slow (particularly with JPEG files), and power-on to first shot is sluggish.

Battery Life
Excellent battery life for a mirrorless camera.

The Sony A7 III 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))