The Sony a7S III
The a7S III is the third model in Sony’s lineup of video-oriented mirrorless cameras, beginning with the original a7S in 2014 and the a7S II in 2015. Keen observers will note that five years have passed since the previous model was announced – which may seem an eternity in Sony years – so it’s understandable that expectations are high.
While the a7S III undoubtedly speaks to videographers and filmmakers, Sony has taken a different approach to its video flagship than we’ve seen from other companies, eschewing the headline specs found on other cameras and foregoing features like high resolution image sensors and 6K, or even 8K, video.
Instead, it embraces good old-fashioned 4K video, a production standard that will remain relevant for many years. Rather than chase ever bigger headline numbers, it focuses on doing one thing and doing it really well. It may still say 12MP on the box, but there’s a lot of exciting tech going on under the hood, so let’s take a look at everything that’s new.
Body
At first glance, the a7S III looks similar to Sony’s other ‘fourth generation’ mirrorless cameras, including the a9 II and a7R IV, bringing better ergonomics and compatibility with Sony’s impressive NP-FZ100 battery. Look a bit closer however, and there are a couple visible (and one invisible) differences worth noting.
The most obvious change is the fully articulating rear LCD display, the first of its kind on a Sony a7 model. It’s a useful addition for a camera aimed at videographers. As we’ll see on a subsequent slide, this LCD also delivers a lot more functionality than any a7-series LCD before it. There’s also a small visible light and IR sensor on the front of the body, designed to improve white balance accuracy in artificial light (something that’s particularly useful considering that most video is not shot in Raw format).
Finally, the a7S III features an all-new internal structure to improve heat dissipation. It’s not visible from the outside, but Sony tells us it’s what allows the camera to record for extended periods of time without the need for an integrated cooling fan.
Rear LCD screen
As we mentioned on the previous slide, the a7S III is the first a7-series camera to feature a fully articulating rear screen. It’s now a much more functional touchscreen as well.
Touch control extends to most aspects of the camera’s operation, including tap-to-track functionality, navigating the menus, pinching, zooming and swiping in playback mode, and even access to the all-important (and customizable) Fn menu. We’d celebrate the innovation if it weren’t such an obvious thing to do, but better late than never, right?
The disappointing news? At 1.44M dots it’s a surprisingly low resolution screen for a premium camera in 2020. We had hoped for a bit more of an upgrade here, but at the end of the day it will get the job done.
EVF
The resolution of the rear LCD screen may be lacking a bit, but the same can’t be said for the camera’s new electronic viewfinder. The 9.44M dot OLED EVF promises more resolution than we’ve seen on any mirrorless camera to date.
We say ‘promises’ because the benefits of full resolution depends on which mode the camera is set to. Based on our experience so far, it appears that the screen uses full resolution in playback mode, but loses some detail when used in live view, even when set to ‘high quality’ mode.
The EVF features an impressive 0.91x magnification and 41º field of view. This results in a high eye point of 25mm so that glasses wearers should be able to see the entire image in the finder. If a higher eye point is needed, the field of view can be narrowed a bit by using only a central portion of the display (though with less magnification).
Sensor
OK, let’s address the elephant in the room: it’s 2020 and the a7S III is still built around a 12MP CMOS sensor. However, it’s a completely different sensor than any we’ve seen in previous a7S models, and it’s a good match given Sony’s stated design intent for the camera: to deliver class-leading 4K video.
To start, the new sensor is a BSI (backside illuminated) CMOS sensor, allowing it to gather more light than the series’ previous 12MP sensors. It also features on-sensor phase detect pixels for improved autofocus, a first for an a7S model. According to Sony, it has twice the readout speed of the sensor found in the a7S II, which allows it to support higher frame rates for video and it should deliver significantly improved rolling shutter performance.
The 12MP sensor also means the camera can use the full width of the sensor for (almost) any capture mode, whether for 4K, perfectly (2:1) oversampled Full HD, or even Raw video capture without any need for pixel binning or line skipping.
Video
Video is what the a7S III is all about. It features 10-bit 4:2:2 color in all recording modes, impressive frame rates running up to 4K/120p, and video can be captured continuously for up to 60 minutes with a minimal crop. Sony claims high ISO video performance has been improved as well, and we’ll certainly put that to the test.
Serious videographers will appreciate the ability to use Sony’s S-Log2 and S-Log3 gamma profiles, which will be much more useful thanks to 10-bit recording (Sony claims to achieve 15+ stops of dynamic range when using S-Log3). There are also presets for HLG to facilitate direct playback to an HDR display and, unlike Sony’s previous HLG implementation, they’re 10-bit as well. One notable omission is the ability to record in 4K DCI format; only UHD 4K is supported.
Next, let’s take a look at the camera’s codecs and Raw video option.
Video codecs
The XAVC codec on Sony’s mirrorless cameras has remained unchanged for several years, capping out 100 Mbps, 8-bit video, so it comes as no shock that the video-focused a7S III jumps well beyond the old specs.
XAVC S recording, based on the H.264 standard, is still there, but now supports bit rates up to 280 Mbps. Additionally, a new XAVC HS codec, based on the H.265 standard, is also available at up to 280 Mbps. H.265 is about twice as efficient as H.264, meaning you can capture just as much detail at half the bit rate, or a lot more detail at the same bit rate. Not surprisingly, Sony takes the latter approach.
Sony also introduces a new version of XAVC S, called XAVC S-I. It’s an all-Intra version of the codec, meaning it captures complete image data for every video frame rather than just saving differential information between ‘I’ frames. With a data rate of 600 Mbps, it should prove beneficial when encoding scenes with complex motion details.
Finally, S&Q (‘slow and quick’) mode can record All-I up to 4K/120p, but with an interesting twist: it writes data at up to 240 Mbps based on intended playback speed. For example, recording 120p for playback at 24p results in an effective bit rate of 1200 Mbps. The downsides? You can’t record audio in S&Q mode, and it requires CFexpress Type A cards for the highest bit rates.
Raw video
Raw video is becoming more common on mirrorless cameras, and the a7S III is no exception. However, it promises to go beyond what we’ve seen on many recent models, outputting full-width, 16-bit Raw video at up to 60p.
So far, the only external recorder to support the a7S III is the Atomos Ninja V, which encodes the camera’s output as 12-bit ProRes Raw. It’ll be interesting to see what the footage looks like, but the decision to use a 12MP sensor means you only have to deal with 4264 x 2408 footage rather than coping with 6K files or any quality loss from sub-sampled a higher-res sensor.
Autofocus
Autofocus is one area where we expect to see big improvements on the a7S III. Previous a7S-series models relied on contrast detect autofocus, necessitating manual focus to avoid focus hunting and wobbling. However, it’s a myth that videographers always want to use manual focus; for many applications, such as documentary shooting, a good autofocus system can be really useful.
The a7S III features a hybrid AF system that includes 759 phase detect AF points that cover 92% of the frame, and which automatically uses eye and face detection when tracking subjects for both video and stills. Sony claims that the a7S III has improved its eye recognition by up to 30% for even better performance. And, unlike some cameras that have limited use of AF features in certain modes, autofocus works in all video modes including 4K/120p.
We’ve been very impressed with autofocus on recent Sony models and anticipate similar performance from this camera.
Connections
External connection points are important to video users, and we think most will like the options Sony included on the a7S III. To start, there’s a full-sized HDMI port, which is more durable and universal than the mini and micro HDMI plugs found on a lot of cameras. The HDMI port also facilitates the camera’s 16-bit Raw video feed to an external recorder.
The camera also features not one, but two, USB ports: USB-C and USB-micro. The USB-C port complies with the USB 3.2 Gen 1 standard, which corresponds to the 5Gbps transfer speed formerly known as USB 3.0. It also supports PD charging systems and allows the camera to run on continuous external power if desired.
Finally, there are 3.5mm headphone and microphone jacks: a must-have on a camera of this nature.
Image stabilization
Like other Sony alpha cameras, the a7S III includes 5-axis in-body image stabilization, claiming up to 5.5 stops of effectiveness.
Additionally, there’s a feature Sony calls ‘Active Mode’ image stabilization. This mode uses data from the camera’s gyroscopes, in combination with cropping the video to a native UHD region of the sensor (approximately 1.1x), in order to allow the sensor to move further and correct even higher amplitude movements.
4-channel audio
In a first for an a7-series camera, the a7S III can record 4-channel audio. This requires Sony’s XLR-K3M hot shoe adapter, which features two XLR inputs as well as a 3.5mm audio input. 4-channel audio facilitates more complex audio setups that might otherwise require an off-camera recorder to execute.
4-channel audio extends to monitoring as well, and the user can configure which audio inputs are routed to the two available monitoring channels.
Menu system
The a7S III features a completely redesigned menu system. Sony menus have long had a reputation for being a bit complex, despite providing a very high level of user customization. By comparison, the new menu system is a breath of fresh air.
The most notable change is that menu tabs are now arranged vertically and color coded by section. When you tap on a menu item a list of settings appears on the right side of the screen. The new layout requires less memorization and is easier to navigate, meaning there’s less toggling back and forth between different screens to find what you want.
The other big improvement is that menus can now be navigated using the camera’s touchscreen interface.
Bionz XR
Bionz XR is Sony’s first new processor in several years, and the a7S III is the first camera in its model lineup to use it. Sony claims the dual chip design has up to 8x the processing power of the previous Bionz X processor.
Why does it matter? According to Sony, the Bionz XR touches just about every aspect of performance on the camera and overcomes some of the restrictions found on earlier a7-series cameras. In particular, image processing is now handled separately from other tasks rather than competing with them, and the new processor also facilitates the camera’s high bit rates for video.
What’s the practical impact? We have yet to fully test the camera, but our initial impression is that the a7S III is quicker and more responsive in its handling than previous Sony models.
Photography features
With all the focus on video it might be easy to forget that the a7S III is also a stills camera, and Sony has added some features worth noting.
Base ISO has been lowered to 80, and can be extended as low as ISO 40 if desired (though this will almost certainly be a ‘pull’ setting that won’t improve dynamic range). At the high end it can shoot at ISO 102,800 with the option to expand that up to 409,800. In addition to Raw and JPEG images, it can capture 10-bit HEIF files with either 4:2:0 or 4:2:2 color sampling, and HLG images that use the same BT.2020 color space as the latest HDTV standards.
The a7S III isn’t a speed king when it comes to shooting stills, but its 10fps burst shooting with mechanical or electronic shutter should be sufficient for all but the most performance-minded photographers. It can also capture 1000 Raw+JPEG images in a burst, not terribly surprising given that each frame is only 12MP.
Card slots
Sony’s a7-series cameras have long included dual card slots, but the a7S III adds a new twist: twin dual-format card slots. In addition to standard UHS-II SD cards, both slots also accommodate a new type of card: CFexpress Type A. As the name implies, CFexpress type A cards are part of the broader CFexpress standard. Their smaller size means they’re not cross-compatible with the XQD-like Type B cards we’ve seen in recent Canon and Nikon cameras.
CFexpress Type A cards have a lower theoretical maximum speed than Type B cards, but have the advantage that they are actually smaller and faster than SD cards. In fact, they’re effectively two generations ahead: V90 is part of the UHS-II standard, and SDexpress, which uses the same protocols as SVexpress, is the next generation beyond UHS-III.
The good news is that if you’re already invested in fast SD cards you can continue to use them since most of the camera’s features work fine with either V60 or V90 cards. However, the camera’s most bandwidth intensive recording format – S&Q (‘slow and quick’) mode with 10-bit 4:2:2 recording – requires CFexpress Type A cards.
Conclusion
Sony’s a7S series has historically delivered very high quality video, beginning with the original a7S and its perfectly oversampled Full HD, then with the a7S II and its native resolution, full frame 4K. Both also provided robust low light video performance at a time that full frame video was less common. But that was 2015, and it’s now 2020. Many cameras – even those without a strong video emphasis – have stronger video capabilities than either model.
The a7S III seems poised to challenge the market again, though it’s a very different market this time around. Instead of trying to win with the most impressive spec sheet, Sony’s strategy is more of a ‘deliver what people want, and do it in a very dependable way’ approach. It’s not a bad strategy; video quality has become so good across the board that a solid, dependable camera that can consistently deliver great results will likely appeal to quite a few videographers.
We haven’t had a chance to fully evaluate the camera yet, but we’re impressed with what we’ve seen so far. We’re looking forward to sharing our findings in the days to come.
Articles: Digital Photography Review (dpreview.com)
