Feature Review: Autofocus for Video on the New Sony a7 III Mirrorless 4K Camera

Sony announced its new 4k mirrorless camera, the a7 III, last week. For photographers and videographers, the a7 III is a great value camera, which Sony calls its new "basic" model. By adding the powerful autofocus of the a9 into this model, Sony has extended its technology at a far lower price point, something all photographers can be happy about. The a7 III has a brand new sensor, the "longest battery life of any mirrorless camera," internal S-Log and oversampled 6K recording for 4K video with no pixel binning (a low quality algorithm for demosaicing).

For photographers, the a7 III is the new starting point for a camera body and packs a lot of value into a $2,000 body. However, I'm going to tailor most of the comments in this review to the video functionality. Despite it not really being primarily targeted product for video, it still has a lot of features at this price point that make it attractive.

Autofocus

The most notable feature of this iteration of the A7 is the autofocus component. Autofocus has long been considered a joke for video and especially for cinema applications, but the technology is definitely getting there, and Sony's a9, a7r III and now a7 III are the proof. Last week in Vegas, Sony had a group of journalists out to test the camera and put it through its paces in a number of shooting scenarios. Here are my quick tests shooting for a few days with it with a Sony 24-105mm lens.

In the video, I tried to stump the autofocus with these common scenarios:

• Moving with a subject in a shot with foreground elements
• Reflective surfaces
• Difficult textures
• Focus while zooming
• Fast moving subjects
• Long throw

As you can see by the results, the autofocus in this camera (inherited from the a9) is next-level-good.

Overall impressions

Overall, this is an exciting announcement for photographers who envied the powerful autofocus in the a9 but didn't want to pay almost double the price. While it offers only slight improvements for video over its predecessor, the 6K oversampling across full width of the sensor is a nice feature and the autofocus in video is surprisingly effective. For filmmakers on a budget who need solid autofocus for a particularly difficult shooting scenario (think underwater), this camera is a good niche solution. While many filmmakers are probably still waiting for an updated version of the a7s before they buy into a new Sony mirrorless, this a7 III definitely provides a solid budget level starting point for many entry-level photographers and videographers.

Available now at B&H.

Sony a7 III Specs

• 24.2 megapixel back-illuminated Exmor R CMOS sensor
• 5-axis optical image stabilization
• Dual SD card slot
• Joystick for adjusting focus points
• USB 3.1 and USB-C terminals
• Weighs 1 lb, 4 oz
• $2,000
• Shipping in April (pre-orders began February 28th)

Sony a7 III video specific specs

• 3840x2160 resolution (oversampled 6K data with no pixel binning)
• 14 Stops of dynamic range
• Wide ISO range of 100-51,200
• SLog 2 & 3 capability
• Up to 120fps in 1920x1080 (still no 4K 60p)

Sony A7iii photography specific specs

• 15 stops of dynamic range
• Up to 204,000 ISO
• 14-bit RAW output in silent or mechanical shutter
• Autofocus is twice as fast as the A7ii
• 693 phase detection autofocus points
• 93% coverage of image area
• New feature: Eye AF tracks eyes and keeps faces in focus
• Up to 10 FPS continuous shooting
• Up to 177 JPEG images in one continuous burst (with UHD card support)