Sony A7S III: what we want to see and what we're likely to get

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Image: Sony A7S II

Sony’s video-centric A7S II model will turn three later this year, and as the only A7-series model not to be on its third generation, there are plenty of rumours and expectations of something fresh. In other words, its successor is surely imminent.

The A7S II was well received by reviewers and users alike, but three years is quite some time in such a fast-moving sector. The fact that the A7S II was so well specified upon launch has helped it to remain relevant, but models introduced in the meantime – both from Sony with its A7R III, the A9 and the A7 III, and rivals like Panasonic’s GH5S and Blackmagic's URSA Mini – prove that there’s scope for a fitter video competitor.

We expect an Alpha A7S III, with the model name ILCE7SM3, will be with us before the end of the year. But what do we expect it will offer? Here’s what we reckon.

1. New sensor

The A7S III is likely to have a new sensor, even if its resolution stays the same

The A7S III is likely to have a new sensor, even if its resolution stays the same

Both the Sony A7S and A7S II have been designed around a 12.2MP full-frame sensor, and, assuming the A7S III's video output is capped at 4K, we expect the A7S III will offer something similar.

Cameras designed primarily to record 4K footage don’t need to a higher-resolution sensor than this, and the whole point of the A7S line is have a sensor with large, light-hungry pixels at its heart, rather than be a resolution beast like the A7R models.

That said, we do expect the sensor will be new, or at least upgraded. Sony’s has masses of expertise in sensor design, and we’ve become used to seeing new models sport sensors with different construction and extra processing power, rather than  more megapixels. 

Of course, if the model does offer video resolution beyond 4K, then this would necessitate a new higher resolution sensor. 6K video, for example, would require a sensor of at least 24MP when the 3:2 aspect ratio of Sony’s 35mm sensor is taken into account. But then this would be a very different model, and it comes with its own challenges, such as overheating and the demands on the processor to pump through this much data. Because of all this, we expect Sony will continue to cap this at 4K.

2. DCI 4K and a wider range of frame rates

The A7S II only records 4K footage in the UHD 4K format, rather than in both DCI and UHD 4K options. It does so at 24p and 25p (or 30p in NTSC), and when shooting at higher frame rates for slow-motion footage (in Full HD), it's limited to 100/120p, with a 2.2x crop factor applied here too.

For the camera to fight against the likes of the Olympus OM-D E-M1 Mark II and the Panasonic GH5S, we'd expect to see a 50/60p recording option, and the ability to capture in both 4K options. Faster frame rates for even slower slow-motion footage would also be welcome to see, particularly as these are now appearing elsewhere.   

3. 10bit recording and no time limit

Videographers will expect to see a broader range of possibilities with both internal and external recording

Videographers will expect to see a broader range of possibilities with both internal and external recording

One area where the A7S II shows its age is with its bit rate – although even upon its release it was clear that some had hoped for more.

The A7S II is capable of 4:2:0 8-bit recording at a bit-rate of 100Mbps, and it can record for up to a second short of 30mins without interruption. 4:2:2 recording, which has twice the colour data as 4:2:0, is possible in an 8-bit format, although only externally through the HDMI port.

Read more: Phillip Bloom explains how anyone can get started with video

When you consider that more modern cameras can record 4:2:2 footage internally at a range of frame rates, and also capture 10-bit footage which gives you a better starting point for grading, this is one obvious area for improvement. It would also be good to see Sony lift the 30min restriction when recording video and offer unlimited recording.

4. Upgraded viewfinder

Like the A7S II, the A7 II (pictured) offered a 2.36million-dot viewfinder, but the A7S III's is likely to have a higher resolution OLED panel

Like the A7S II, the A7 II (pictured) offered a 2.36million-dot viewfinder, but the A7S III's is likely to have a higher resolution OLED panel

The A7S II's viewfinder has a great 0.78x magnification, and a respectable 2.36million dot resolution, but this is one area we expect to see changes made.

Not only do Sony's most recent A9 and A7R III models incorporate a 3.69million-dot alternative with a 120fps refresh rate, but rival models like the Panasonic GH5 and its GH5S variant – and even the cheaper G9 – offer something very similar too.

Read more: Panasonic G9 review

It's true that Sony's last release, the A7 III, stuck with that appeared to be the same viewfinder as the A7S II, but then this would be an expected concession when you consider its lower price point.

5. Better, touch-sensitive LCD

It seems likely the A7S III will get a touchscreen like the A7 III (pictured)

It seems likely the A7S III will get a touchscreen like the A7 III (pictured)

Sony has taken a little longer than others to incorporate touchscreens into its APS-C and full-frame bodies, and this is one feature that was missed on the A7S II. Now that it's popped up on a number of newer Alpha cameras, however, we very much expect this will make its way to the A7S III.

We see no reason why Sony would drop the tilting mechanism that has featured on previous A7-series cameras, although the company is now using a newer 1.44million-dot panel in place of the 1.23million-dot one that featured on the A7S II, so we would expect this will make the cut too.

6. Better heat disposal

Much like the A7R II, many A7S II users noticed the camera's tendency to overheat when recording for prolonged periods of time. This would, very inconveniently, simply cause the camera to stop recording, so a revised internal design that would be better able to keep things cool is definitely something we would expect to see here.

7. Dual card slots with UHS-II support in both

The Panasonic GH5S, one of the A7S III's main competitors, is one of the latest cameras to sport two card slots 

The Panasonic GH5S, one of the A7S III's main competitors, is one of the latest cameras to sport two card slots 

The current A7S II only offers a single card slot for SDHC/SDXC (and Sony’s Memory Stick) media. It could be argued that a second card slot is less of a priority on such a camera than it is elsewhere, given the likelihood of many recordings being output straight through the camera’s HDMI port to an external device.

Read more: Why do some SD cards have two rows of pins?

Even so, as both the A7R III and A7 III have sported a dual-slot design, it would be odd to see the A7S III continue with just the one. Ideally both slots would support the UHS-II standard too. Not sure what this is? We explain it here.

One reason not to add one is that it would potentially make the camera physically bigger, although we expect the body to be a little bigger than before anyway, thanks to the next expected feature.

Read more: How to understand everything written on your camera's memory card

8. Z-series battery

Many recent Alpha models have been supplied with the NP-FZ100 battery

Many recent Alpha models have been supplied with the NP-FZ100 battery

Traditionally, one of the main disadvantages of mirrorless cameras over DSLRs is that they offer a shorter battery life. Bodies designed to be portable mean physically small batteries, and a greater reliance on electronic viewfinder and LCD screens also drain a lot of juice.

Both the A7S and A7S II have been something of a letdown here, with a stated battery life of just 380 and 370 frames respectively, when using each camera’s LCD screen. Battery life on the latter when using the EVF is even more disappointing, at just 310 frames per charge.

It’s likely this will be different on the A7S III because of developments since those models were released. The use of a new Z-series cell inside more recent models has given battery life a considerable boost. The A7R III and A9, for example, whichg both make use of the battery, respectively offer around 530 and 480 shots per charge when using the EVF, and up to 650 if you stick to using each camera's LCD instead. The most recent A7 III model managed to increase this even further, with around 610 frames with the EVF and up to 710 with the LCD.

9. Upgraded focusing system

Sony has put a lot of work into the focusing systems of its most recent models, and we’d be very surprised if we didn’t get some kind of boost here. Here’s a quick look at what the A7S II and each A7-series camera released after that point has offered:

  • A7S II: 169 contrast-detect AF points 
  • A7R III: 399 phase-detect and 425 contrast-detect AF points 
  • A7 III (and A9): 693 phase-detect and 425 contrast-detect AF points

A hybrid system that combines both phase- and contrast-detect AF points is likely to star here. Given that the model is likely to be pricier than the A7 III, it would seem odd if Sony didn’t gift the A7S III with the latest 693/425-point hybrid system, but sometimes there are technological reasons why an alternative needs to be used. Then again, even the A7R III’s older system would be an improvement.

As the A7S models are partly intended for use in low light, we would expect to see at least the same -4EV rating for the AF working range as before, although it wouldn't be a surprise to see this increased even further down to -5EV. Other more recent Sony models typically only stretch to -3EV instead, but they are, of course, designed for different purposes. Panasonic's recent GH5S manages to deliver a working range down to -5EV, so it would be good to see Sony equal this.

10. Joystick

We expect to see a similar joystick to the one found on the A7R III (pictured)

We expect to see a similar joystick to the one found on the A7R III (pictured)

A joystick-type control has become a standard feature on many modern cameras, including the most recent Sony A7-series models. Although most cameras allow you to use this to navigate menus and zoom around images, this is principally used to adjust the focusing point. The A7S II lacked this feature, which made it more tricky to quickly shift this in a particular direction, so we’d expect the A7S III to match its siblings in having one designed into its rear plate.

Read more: 10 tips on getting the best out of your Sony camera