Introduction and features
We’re still carrying out real-world testing on the Sony A7S II, but we have now finished our lab test results and these make for some very interesting reading. We’ve included the lab test data for three of its key rivals, too – the Sony A7R II, Canon EOS 5D Mark III and Nikon D4S.
With the launch of the A7S II, Sony has finished updating its trio of full-frame compact system cameras to Mark II versions. The old models continue alongside as cheaper, older-specced alternatives, so there are currently six cameras in the range. We’ve already reviewed the jack-of-all trades A7 II and the high resolution A7R II.
The A7S is the last to be updated, then, and it’s probably the most specialized of all. It sacrifices outright resolution with just 12 million pixels, but makes up for it with ultra-high sensitivity (up to ISO 409,600) and top-quality 4K video.
The original A7S was one of the early 4K cameras but, crucially, could only record 4K video to an external device. Newer rivals could record 4K video to an internal memory card, leaving the A7S looking out of date – so the internal 4K video recording of the A7S II is perhaps its most important new feature.
Like the A7R II, which we’ve just reviewed, the A7S II allows internal recording in the XAVC-S format with no pixel binning. Pixel binning uses neighbouring pixels to ‘improve’ the data for each photosite on the sensor, but it’s a type of mathematical interpolation that’s no substitute for proper, pixel-level data, and Sony claims this is one of the A7S II’s key technical advances. The XAVC-S format is the 4K equivalent of the AVCHD format used by Sony and others for efficient 1080 full HD video recording.
The power needed to capture full HD has a knock-on effect on lower resolutions, and the A7S II can also record full-HD footage at up to 120fps and at a bitrate of 100Mbps for super-slow motion playback. The bitrate is an indication of the compression applied to video footage and its subsequent quality.
12 megapixels may seem an insanely low resolution for a full-frame compact system camera, but the A7S II is designed for sensitivity rather than resolution. This is as clear an indication as you could ask for that resolution, sensor size and high-ISO performance are inextricably linked. In short, the only way to get good quality at super-high ISOs is with super-sized photosites on the sensor, and that inevitably means you get fewer of them.
The A7S II also adds Sony’s latest 5-axis image stabilization, so that in extremely dim lighting, where even its highest ISO settings still produce slow shutter speeds, the A7S II should still be able to get sharp hand-held images.
While the Sony A7S II has the same resolution as the original model, Sony says new noise reduction hardware and software gives better results at high sensitivity settings. This is also a designed as a professional video camera, and Sony has included its S-Log2 setting as well as its new S-log3 mode. These can increase dynamic range by up to 1300% by creating what looks like very flat looking footage initially, but which is designed for extensive post-capture grading. While S-Log2 is especially useful for preserving brighter tones, S-Log3 is designed to capture the maximum tonal range in shadow to mid-tone areas – this is the video equivalent of shooting raw files for stills.
Finally, the number of autofocus points has been increase to 169, and Sony says the A7S II has 2x faster autofocus response in video mode.
Lab tests: Sony A7S II resolution
We’ve tested the resolution of the Sony A7S II using our standard test chart at ISO settings right up to the camera’s maximum of ISO 409,600. High ISO performance is one of this camera’s key selling points, so we’ve created specially extended test charts (below) to show how this camera and its rivals perform in extreme lighting conditions.
The three rival cameras we’ve chosen are:
Sony A7R II: It has more than three times as many megapixels as the A7S II, and you’d expect the trade-off to be much poorer performance at higher ISOs. But is that what happens?
Canon EOS 5D Mark III: Canon’s long-running favorite amongst pro photographers offers a great balance between stills and video quality and high-resolution/high-ISO performance.
Nikon D4S: Like the Sony A7S II, The D4S is designed to be a master of low light photography, but with 16 megapixels rather than 12, is it a better compromise for general use?
JPEG resolution analysis: It’s obvious right away that the 12 million pixel sensor of the A7S II is the major limiting factor for its resolution figures. A figure of 22 line widths/picture height is what you’d expect from a compact camera, not a full-frame professional model. The EOS 5D Mark II and Nikon D4S beat the A7S II convincingly for resolution, and the A7R II is so far ahead it’s not even in the same ballpark. But the A7S II does start to get on even terms at super-high ISOs, where its resolving power is much closer to the rest.
Raw (converted to TIFF) analysis: The pattern is repeated with raw files – in fact, the gap between the A7S II and the rest is even larger. It’s not until ISO 51,200 that it starts to edge ahead of the EOS 5D Mark III for resolution, and it never catches up with the Nikon D4S.
Lab tests: Sony A7S II dynamic range
Dynamic range is a measure of the camera’s ability to record a wide brightness range. The higher the dynamic range, the less likely you are to see burnt-out highlights or blocked-in shadows. Dynamic range is measured in EV (exposure values) and its typically highest at low ISO settings, falling off as the ISO value increases.
JPEG dynamic range analysis: The relatively low resolution of the A7S II should give it an advantage in dynamic range because the individual photosites (pixels) are larger and can in theory capture more light and hence a wider range of light values. In practice, the A7S II only starts to show an advantage at ISO 51,200, which is well outside the range of normal photography. If you do need to shoot at these ISO settings, and higher, it does have an advantage over the rest.
Raw (converted to TIFF) dynamic range analysis: Apart from an odd dip from ISO 800-1600, the A7S II is narrowly the best of this group, though the Canon 5D Mark II and Nikon D4S run it a close second.
Lab tests: Sony A7S II signal to noise ratio
The signal to noise ratio measures the amount of noise in the image compared to actual image data. The higher the number, the less noise you’ll see in the camera’s images. You’d expect the A7S II to do well here because its relatively large pixels should capture more light relative to the baseline background noise.
JPEG signal to noise ratio analysis: The A7S II is at or near the top of this group for noise levels, but its advantage is slim at best, and even then only at ISO settings of 6400 and above. Even the 42-megapixel A7R II isn’t far behind.
Raw (converted to TIFF) signal to noise ratio analysis: These results are dominated by the remarkable and unexpected performance of the EOS 5D Mark II. It beats the A7S II into third place – it’s beaten narrowly across most of the ISO range by the Nikon D4S.
Build, handling and early verdict
Sony’s original A7, A7R and A7S did draw some criticism for their design and layout, and in the Mark II versions, Sony has made some changes. The camera’s grip is bigger, the shutter release has been moved forward on to the top of the grip and the video record button is now on the side of the thumb-grip on the back of the camera – this makes it harder to press accidentally. In fact, though, it makes it harder to press generally, so you might want to set one of the two custom buttons on the top of the camera to start video recording instead.
The A7S II feels well made, though, and it’s comfortable to hold. It’s also tougher than the old A7S, with more magnesium alloy in its construction and a reinforced lens mount.
The menu layout is largely the same as the A7R Mark II’s, which we’ve already reviewed, and has the same high level of customisation available. However, it would be nice to have separate sections within the main menu for stills and video controls, and a second Function Menu for video options.
Performance
We haven’t been able to shoot any samples with the A7S II yet, but its predecessor was pretty impressive and the samples that Sony has shown us do look very good..
The A7S II does have fewer pixels than the A7R II and A7 II, so you won’t get the same level of resolution. But it’s easy to get caught up in megapixel hype and forget that not so long ago 12 megapixels was actually quite a lot – and it’s still enough to create high-quality A3 prints. This camera isn’t just about stills, though, but video too, and both 4K and Full-HD footage should have higher quality because they’re generated using the larger photosites on the A7S II’s 12-megapixel sensor.
We found that the original A7S controlled noise well, though the top ISO 409,600 setting came with such a drop in quality that it was best avoided. But it’s important to keep this in perspective – compared to typical consumer DSLRs and compact system cameras, this is a stratospheric level of sensitivity and it’s remarkable that the sensor can record images at this level in the first place. Sony says the A7S II has improved high-ISO performance and we look forward to testing this properly when we can get a sample for testing.
Sony is claiming a big improvement in the A7S’s autofocus capability too. We were shown a demonstration involving a stuffed toy in a dark box,and it did look good, while in more average lighting conditions it proved fast and accurate. Again, though, we’ll want to test this properly.
Early verdict
The A7S is a specialised, high-sensitivity stills/video camera and we’re told over half of the people who bought it are professionals. Sony already makes a cheaper general-purpose variant, the A7 II, and a high resolution model, the A7R II, so it’s able to target the A7S II at low light and video photography without the need to compromise it for a wider audience. The in-camera 4K recording brings it up to date – this was starting to look like a serious failing in the original model, and the faster AF and better noise control are a useful step forward.
The Sony A7 II is a better all-rounder and the the A7R II shoot higher-resolution stills, but if you need to specialize in video or low-light photography, the improvements in the A7S II look like an important update to an important camera.
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