March 5, 2018
Field Test

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

a7 s III
We tested out the powerful autofocus of the latest in Sony's mirrorless lineup: the a7 III.

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.

Sony Announces New A7 Mark iii Camera Body

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.

Sony A7 III Topside

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)

Your Comment

8 Comments

Okay, looks good. Just curious about some of the settings:
- Was the autofocus speed set to Standard? Did you try any with it set to the slower speed?
- How big of an autofocus point were you using? The smallest?
- Did you use the touchscreen to move the focus point while shooting?
- Were you shooting wide open all the time (f4) with the 24-105?

March 5, 2018 at 2:13PM, Edited March 5, 2:13PM

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Bruce Hyer
DP/Writer
60

Autofocus in continuous, center mode, highest speed. Didn't use any of the touch screen options but I've heard good things. Mostly wide open with the exception of the day shots (had no ND filter with me).

March 5, 2018 at 11:44PM

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Micah Van Hove
Writer
director, producer, dp

Cool video, would be neat to see it focus at slower speeds. You have some awesome locations for testing! So this is a full frame sensor right?

March 6, 2018 at 2:33AM

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David Prokopchuk
Photographer / Film Maker
195

I'm surprised about all the "filmmakers" who care about auto focus. I personally don't.
The question I have is, when I'm going to compare the footage of that new Sony to an "old" $ 800 (ebay price as I write this) BMCC 2.5K MFT with speedbooster and a Zeiss lens, how is it going to fare? Does this Sony make that old cam, the BMCC 2.5K totally obsolete? That's what should be relevant for filmmakers.

March 6, 2018 at 7:52AM

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They are different cameras with different textures. Way different sensor sizes (full frame vs 16), way different low-light performance (Sony destroys everyone in lowlight). One is not simply better than the other. This post isn't a footage test for the new Sony camera but the autofocus, which is the one place getting recognizably better each iteration.

While I agree you would probably never use it in a narrative cinema environment, there are many filmmakers who make stuff outside of that mode who would find autofocus very useful (there's a whole industry of event videographers).

March 6, 2018 at 1:18PM

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Micah Van Hove
Writer
director, producer, dp

Different horses for different courses. The BMCC codecs (DNG, ProRes and DNxHD) will beat the sony XAVC-S for colour grading ability and VFX work. But on a shoot where I'm not able to do a lighting setup there's no way I'd use the BMCC, Sony all the way for that. The biggest disapointment for me about the A7III is the 30min recording limit, if it weren't for that it would be the perfect indoor events camera.

As for focusing; autofocus is just a tool, I'd rather have it as an option (even if I don't use it) than not have it at all.

Source: I've owned and shot with the BMCC for 3 years and am considering getting the A7III

March 6, 2018 at 9:03PM, Edited March 6, 9:04PM

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Adam Prest
Camera, Edit and Workflow Technician
15

You're comparing a dedicated cinema camera to a stills camera that shoots video. Both cameras have things they do better than the other. BMCC has superior color science and color depth, but there is no comparison when it comes to low light. It all depends on what you're shooting, some situations the BMCC may be the best choice, and others the A7III.

And I used to say the same thing about AF, "the film industry has used manual focus since it's inception yada yada," but once I used a camera with good video AF I changed my mind. And for a gimbal with a single operator it's a godsend. Video AF was hit or miss up until recently, with this camera and the A9 it's another step in the right direction, that's why they're mentioning it.

March 6, 2018 at 10:06PM, Edited March 6, 10:08PM

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The A7III monitor, has desqueeze (anamorphic) capabilities? TKs, regards.

March 11, 2018 at 12:14PM

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This is not at all how my a7iii is performing. What color profile are you using? I shoot slog2 and it's focusing terribly! I'm wondering if I should send it back... Could it be the profile is too flat to focus correctly? These videos make AF-C look so snappy. Mine takes 2-3 seconds to refocus once I change subjects if it focuses at all... Really disappointed so far.

August 23, 2018 at 11:46PM

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nate
1