Sony Alpha A7S Digital Camera Review
A niche camera in a family of niche cameras
By the Numbers
We expected the A7S to do roughly as well as its forbearers in our labs, and it gave us all the A7R did and more. Thanks to its new 12-megapixel CMOS sensor, it scored even better in some areas. The dynamic range and sensitivity are better than before, making the A7S way more flexible than the A7R or A7. It's a truly special camera that, although it might not be the best A7 for everybody, makes a compelling case for its existence by kicking butt and taking names at high ISOs.
Color & White Balance
Color accuracy wasn't this camera's strong suit, with the A7S scoring below the A7R in our standard test. The camera's most accurate mode, Standard, is one of a few presets that offers options for JPEG shooters. We measured a ∆C00 corrected of 2.95 and a saturation of 109.8%.
White balance was also a little bit lacking, with decent auto performance but very poor custom performance. We saw errors as high as 403 kelvins, missing the mark especially under fluorescent lights. You can always get around this lowlight by shooting RAW however—something we expect most A7S users will want to do anyway, to take advantage of the extra dynamic range.
Sony isn't known for subtle noise reduction, and the A7S is a lot like other Sony cameras in that respect. With noise reduction "off"—according to Sony—we saw noise stay below our 2% threshold for quality all the way through ISO 6400. You can further keep a lid on noise by just shooting with the default level of noise reduction, which keeps noise below 2% through to ISO 102400.
That said, the design of the sensor really helps cut down on visible noise until ISO 25600, and we didn't see heavy banding until way after we'd recommend users stop shooting. We think you can shoot in RAW up to ISO 12800 without much worry, since 25600 still begins to get a little too noisy. We found that as soon as too much chroma noise kicks in, the A7S produces images that have a surprisingly fine grain, which makes them decent candidates for black and white conversion.
If you're truly desperate for low light sensitivity, the A7S also offers a remarkable top ISO speed of 409,600. The only other camera on the market that can shoot at that sensitivity right now is the Nikon D4S, which is also a full-frame camera with a 16-megapixel sensor and a far heftier price tag. The A7S in all of its JPEG modes handily outperforms the D4S at this ISO speed, with far less noise and a similar level of detail retained in the final shot.
The Sony A7S absolutely stunned us with its HD video. The sensor's sensitivity helps retain detail incredibly well, even while keeping noise down in low light conditions where gain has to be ramped up. The results were so good, that both in our bright and low light tests, we saw almost the same resolution numbers. In our bright light test, the A7S resolved 775 line pairs per picture height (LP/PH) vertical and 775 LP/PH horizontal. With the lights turned down low, we measured 750 LP/PH horizontal and 775 LP/PH vertical. Considering most DSLRs struggle to get above 650 LP/PH in bright light, these are impressive results indeed.
And, even though the quality was pretty bad looking, the A7S can shoot when there's basically no light in a room. Both in an informal test we ran and in our standard minimum illumination test, this camera outgunned what we threw at it. It required less than 1 lux to hit 50 IRE, putting it in the same league as the Nikon D4S, which could basically see in the dark. We were even able to shoot a (fairly dark) image in about 5 lux of incidental lighting. We actually aren't sure just how low a light level the Sony A7S requires because our Spectra IV light meters were reading zero lux even while the A7S was producing an acceptably bright image.
We were impressed with the dynamic range that the A7S is capable of interpreting. In our standard DR test, Imatest reported 8.79 stops of high DR. At ISO 200, we logged a slight drop to 8.56 stops. At ISO 400, we measured 8.11 stops. Finally dropping off past 8 at ISO 800, we saw 7.32 stops. ISO 1600 exhibits another drop to only 5.94. ISO 3200 netted 5.26, and ISO 6400 scored 4.03.
Now for the impressive part—the A7S keeps going up the scale. Thanks to a bit of what we think is software trickery, high ISOs report way more DR than other competing full-frame digital cameras. ISO 12,800 reports 2.72 stops of DR, while ISO 25,600 retains 2.18 stops. Going up further, the A7S holds onto 1.38 stops at ISO 51,200 and 1.11 (!) at 102,400. It's at this point that Imatest reports no stops, both at 204,800 and 409,600.
If you look at low-quality dynamic range (which is a more common measurement industry-wide) we managed to get around 12.8 stops at the base ISO of 100. We've seen other sites report range as high as 14 stops in video, as well, which we'll get to when we do our full video breakdown of the A7S.
Shot to Shot
The Sony A7S isn't going to replace a pro-grade DSLR any time soon if you're into high-speed action photography. Not only is the autofocus system too slow and imprecise, the camera also can't keep up when shooting continuously. We were able to nab exactly 5 frames per second at the camera's peak rate.
That's not anywhere near the 12+ frames per second we're used to seeing with pro-quality full-frame cameras like the Nikon D4S and Canon 1D X. Of course, this camera costs far, far less than those cameras. If you're putting it up against the lower-cost full-frame options in Canon and Nikon's stable—the Canon EOS 6D and Nikon D610—then it is closer to the norm. Still, Sony is generally known for faster consumer-grade cameras than the competition, so we're eager to see what the next generation of FE-mount cameras can do.
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