Sony Alpha A7S Video Performance Review
The 4K future is here, but is anyone ready?
Like it or not, we're on the verge of a 4K revolution. We've noted previously that even though content distribution is still "the rub," content creation and management couldn't be more straightforward. As long as you have a powerful enough computer with plenty of disk space, you can work with 4K just like you would with full HD—just slower.
Typically revolutions like this start out as very expensive luxuries for early adopters before getting cheaper down the line a couple of generations in. 4K shooting seems to be blowing that timeline right out of the water, at least when it comes to consumer consciousness. While 4K has been around for several years, it feels like just last year when it first started to hit the scene. And yet this year we're already starting to see 4K-capable cameras available for $2,000 and under. Even if you're ambivalent about this bold, new, higher-def future, you can't deny that the options are surprisingly well-executed this early in the game.
The Panasonic GH4, in particular, is a remarkably advanced product. It shoots 4K to the same kind of SD cards you probably already own and does so right out of the box. By contrast, Sony's Alpha A7S (MSRP $2,499.99) is refreshingly old-school. It works with any lens under the sun, but only with a mess of cheap adapters off eBay. It can shoot 4K, but only if you pair it with a bunch of external equipment—some of which isn't even on the market yet. If you miss the good old days of format wars, HD-DVD, and LaserDisc, the A7S is a nostalgia trip waiting to happen. But when we do the sensible thing and ignore the 4K capability altogether, the A7S actually reveals itself to be a monster of a full HD video camera, perfect for the here and now.
Design & Handling
Less-than-ideal without rigging—but workable.
It's a tricky thing designing a "traditional" camera that's intended for video production. Even though the A7S can be thought of as a hybrid video/stills camera, very few of the design choices cater to the former. Even the Panasonic GH4—a similar hybrid camera—seems far more geared toward video shooters than Sony's mirrorless maven.
Whereas the Panasonic Lumix GH4 was designed with run-and-gun shooting in mind, the A7S's petite body makes it seem less up to the task of harsh environments and documentary filmmaking. In terms of directorial style, the Sony is less for a Paul Greengrass-type and better suited to the Stanley Kubricks of the world. This was a common theme among our experiences with the A7S. At least without a good deal of rigging, the A7S is at a disadvantage compared to other options on the market today.
The Sony A7S does have one big ace up its sleeve: It's easily the most adaptable lens system on the market, easily compatible with almost every 35mm lens system you can find. The grip is a little on the small side, however. First-party FE lenses are also a little bulkier than those on some other mirrorless systems, and, if you have nice cinema primes you'd like to use, you'll find that the diminutive A7S also doesn't balance very well. That said, it's a perfectly workable solution, even if it does feel like someone left a Canon 5D Mark III in the dryer too long.
Still, control and layout-wise, there's not as much direct control as we like on our video cameras. Whereas the GH4 has well-placed, dedicated controls for ISO, white balance, and exposure compensation, the A7S, with its more compact chassis, requires you to make frequent trips into menus. Again, not a dealbreaker, but it's just more evidence that the A7S is built for people who don't mind tinkering with their toys than professionals who need to get to work.
Speaking of tinkering, there's a distinct advantage that the GH4 retains over the Sony. Using the GH4's touchscreen, it's quite easy to semi-automatically choose which subject to focus on, and you can also map custom functions to on-screen buttons. Additionally, the camcorder-style swiveling hinge the GH4 features is also very helpful if you're shooting off-tripod. While the tilting screen of the A7S is quite nice—we're also big fans of the clarity of Sony's vivid WhiteMagic screens, as seen here in the A7 family as well as the Ricoh GR, among others—the freedom it affords a camera operator just isn't as good as camcorders or other options.
Sony's native full-frame mirrorless lenses have a bright future...but the present is another story.
First off, we get it: the Sony A7S can be used with any piece of dusty glass you can find at a yard sale. It's an impressive achievement and often these lenses perform even better on Sony's cameras than with their own native bodies. That's awesome, and it's undeniably the biggest piece of nerd-cred in the A7S's favor. That said, the native FE lens family still needs a lot of work to catch up to other full-frame cameras.
Sony has put a lot of effort into developing the full-frame E-mount lenses, and so far things are looking very rosy. We've been incredibly impressed by great lenses like the two compact Zeiss primes, the 35mm f/2.8 and the absolutely terrific 55mm f/1.8. They aren't cheap, but they're both nice to shoot with, even for video. Moreover, the roadmap is really quite promising, especially if you know you'll be shooting wide. If you have a little more freedom to frame, however, the Micro Four Thirds ecosystem is an embarrassment of riches of budget-friendly fast primes. With lenses like the Olympus 75mm f/1.8 you can scarcely complain about the lack of bokeh, either. Wide zooms like the Olympus 7-14mm and Panasonic's 12-35mm f/2.8 are also great choices for video.
The A7S does have some unique touches that will appeal to cinematographers. Zebra patterns with selectable tolerances, along with customizable guidelines in a bunch of aspect ratios, including a non-anamorphic 2.35:1, but the Academy ratio is nowhere to be found—sorry, Wes Anderson.
As of this writing, Sony has made it relatively easy to add XLR audio inputs on the A7S, but that's about it. If you hope to integrate this Alpha into your studio setup, there's no first-party way to add HD-SDI connections. Contrast that with the GH4, and its YAGH Interface Unit, or the Blackmagic Cinema and Production cameras, and you can see exactly where Sony's commitment to professional video in its mirrorless family falls short.
Codecs, Resolutions, and Framerates
We were promised jetpacks…and internal 4K!
If you take a look at the 4K-native options on the market today, your head might spin with all the differences and options. Compression, bit rates, frame rates, chroma sub-sampling and sensor readout…it's quite a bit to take into consideration. Even though the A7S doesn't cover all the bases perfectly, it makes up for shortcomings in a few other ways.
The A7S shoots 4K video at one resolution—3840x2160. Capturing this video will cost you, however, since this is only possible if you have an external recorder. Given that the camera itself is already around $2,500 body-only, you're going to need to budget accordingly if you want to work with the next generation of high definition video. The GH4, on the other hand, shoots this same resolution, along with a cinema-oriented 17:9 aspect ratio at 4096x2160, directly onto a UHS-3 SDXC Card. More troublingly the only external recorder that supports the HDMI throughput necessary for A7S 4K video (the Atomos Shogun) isn't on the market yet, and even then it'll only record 8-bit 4K video. The GH4 does 8-bit 4K video internally and can do up to 10-bit 4K video through the YAGH unit.
It's actually a little surprising the A7S doesn't do 4K internally. The Sony Handycam AX100 captures 8-bit 4K/30p video internally to an SD card and it has the same Bionz X processor as the A7S. We know the processor can handle the data, we know the codec supports 4K, and we know the sensor can do 4K video in this mode since it outputs uncompressed 4K video via HDMI when shooting in XAVC S mode. Other than perhaps heat dissipation we just can't figure out what's preventing Sony from supporting internal 4K recording given the components in play here.
Either way, only supporting 8-bit—even to an external recorder—is a big mark against the A7S. If you're planning on grading your footage, you'll want as much data as you can get, since it'll give you more subtle gradation and hold up better to post-production work. No matter whether you select HD or 4K, the A7S is at a disadvantage when shooting uncompressed video to an external recorder. Even though XAVC S seems to be much more efficient than the typical AVCHD/MOV recording modes, the GH4 still trumps the A7S when it comes to throughput. Topping out at 60 Mbps, the Sony A7S can't match the 200 Mbps 1080/60p mode that Panasonic packs into the GH4. Of course, if you need maximum data you can always
buy rent a Canon C500 and put down 12-bit 4K at 60p.
While this might sound like a bunch of whinging over what could be minor disadvantages to professionals already used to kludgy solutions, the A7S is a confusing mishmash of exceptions and caveats. The A7S, when you get down to it, isn't a fully fledged and integrated 4K solution. It's a first-generation product with some special benefits for early adopters. That wouldn't be a big issue this early in the 4K game, but more complete products already exist, including within Sony's own digital imaging lineup.
Fight the darkness.
In our still camera review of the camera, the A7S was notable not for its speed, resolution, or any of the normal gearhead concerns. Taking a completely different approach to mirrorless digital photography, the A7S doubled down on sensitivity. With a less-dense 12-megapixel sensor, the A7S was left with a 35mm full frame sensor filled with relatively massive individual pixels. Those bigger pixels unlock a magical array of ISOs, reaching all the way to 409,600. While this is handy for still photography, it's even more useful when you're shooting HD or 4K video, where the natural downsampling that occurs gives you the best of both worlds.
The lower resolution of the sensor is absolutely no worry for HD or 4K, so there's no tradeoff for getting that amazing sensitivity when shooting video. It is utterly magical how well this camera shoots in low light, capable of recording available light video with little more than a full moon. The elasticity of the footage you can get from it is unrivaled for the price, with only Nikon's far more expensive D4S providing this level of sensitivity.
But ISO speeds aside, the star attraction for video shooters has to be the A7S's S-Log2 picture profile setting. This setting, which debuted in a firmware update for Sony's F65 CineAlta professional motion picture camera, tweaks the gamma curve to unlock maximum dynamic range. That $65,000 cinema monster was designed strictly for professional usage, and it's amazing that just two years later, you can get a tiny, full-frame video camera with this unique profile built-in for a fraction of the cost.
S-Log2 limits your levels of sensitivity, but it's for the best. Even though you have to shoot at a starting ISO of 3200 (don't forget to use a variable ND filter if you're shooting in the daylight!), the A7S caps out at ISO 409,600. That's a heck of a lot of latitude, but it isn't just the numbers that make this impressive. We were impressed by how film-like the grain looks at these higher ISOs. You'll want to steer clear of the last few stops of sensitivity due to banding and more pronounced noise, but at that S-Log2 base ISO (3200) we measured about 13 1/2 stops of dynamic range.
Interestingly enough, Imatest detected about the same amount of DR at base ISO (100) with no picture profile applied. That means that even though you need very little light to properly expose the base ISO with S-Log2, you easily retain all of the range as base ISO. Going up the ISO scale in S-Log2, we saw very little drop-off of this available range, even at max ISO.
HD video looks great from the A7S, but we were very excited to see what this baby could do with 4K. Unfortunately, since compatible external recorders aren't available until later on this year, we'll have to wait to test that capability. As far as its HD sharpness goes, the A7S did an admirable job. The direct sensor readout really does help the camera perform better than its siblings. In bright light and low light, HD video resolved plenty of detail. In our standard bright light test, it resolved 775 lp/ph (line pairs per picture height) vertically and 775 lp/ph horizontally. What's shocking is that in significantly lower light (60 lux, to be exact) the A7S did almost the same—750 lp/ph vertical and 775 lp/ph horizontal. Your results may vary, but it's amazing to see how well this sensor holds on to fine details in extremely low light. It's worth noting that we ran our tests with the premium, Zeiss-branded Sony FE 55mm f/1.8, but even better lenses could be sharper.
One area where the A7S has a clear weakness? Its rolling shutter. This effect, sometimes called "jellovision" by videographers, is due to the scanning nature of the sensor. Competing cameras often do a good job mitigating this effect, but the full-frame Sony is practically a textbook example of the problem, making quick pans with the camera basically a no-go.
Famed cinematographer and all-around nice guy Philip Bloom, came up with a rather clever workaround. The camera's built-in APS-C crop mode isn't just for older E-mount lenses—you can turn it on and mitigate much of the camera's rolling shutter effect while still shooting in full HD. If you're adapting full-frame glass and want to use the crop mode, you can then add a speedbooster to bring the lens closer to how it would act in non-crop mode. It may sound utterly bizarre that you'd buy a full-frame camera to crop it and add a speedbooster, but it sounds like a viable solution if you a) need less visible rolling shutter and b) you want your glass to retain its brightness and original focal length.
Then again, if you need absolutely no rolling shutter in your final product, the Blackmagic Production Camera 4K is only $500 more. Not only do you get a global shutter (which eliminates rolling shutter altogether), but you also gain CinemaDNG RAW shooting, built-in HD-SDI and...what's that? Oh yes, it shoots 10-bit, 4:2:2 footage straight onto a standard-issue SSD.
The future is (almost) now.
In case you couldn't tell, our main takeaway from our time with the A7S is that it isn't a camera for everybody. We think some really talented artists will be able to use this as an incredible tool, but for many indie filmmakers and professionals who want something that just works, the Panasonic Lumix GH4 is a better all-round option right now. And with the YAGH interface unit adding even more capability, that is probably true going forward as well. No, it can't bend over backwards in a candle-lit room just to help you get a properly exposed image, but it will be a trusty companion that can shoot 4K whenever, wherever, and extremely good HD video as well. It helps that the GH4 is also quite a bit cheaper, with a more established native lens family.
But, let's not mince words—if you're very dedicated, you won't let those facts get in the way of you and the shot you want to get. The A7S is a fantastic product for early adopters, a camera that will challenge you to jerry-rig solutions to get shots that literally nothing else on the market can match. Want to record 4K video on the go right now? How does strapping the A7S to a Blackmagic HyperDeck Studio and powering the whole shebang with a car inverter sound? Awesome? Yeah, it does to us to. After all, what's indie filmmaking when a giant bundle of gaffer's tape isn't involved?
If you look at it from that perspective, then the Sony A7S is an unparalleled product on the market today. If you're willing to take a risk and invest the cash into this system (don't forget that external recorder if you want 4K!), you get a system camera that's way smaller than the other full-frame cameras, that's more versatile than any other budget option on the market, and can shoot in the freaking dark. The lack of a global shutter still makes it less-than-ideal, since bad rolling shutter puts the kibosh on using the A7S for action-packed shots, but you'll figure it out, we're sure. From a practical perspective the GH4 is a better hassle-free solution right now, but if we took the practical route we'd all be lawyers.
Seriously, though, what the A7S teases is the enormous potential of Sony's FE system. After spending a few weeks with the A7S we're not as excited to keep shooting with it as much as we're excited to see what Sony has up its sleeve for the next member of the FE family. Given Sony's determination to bring 4K to the masses, we fully expect to see more of these cameras on the way. Even though Panasonic has the upper hand right now, we think Sony is probably about a year away from giving the GH4 a real run for its money with a 4K-ready full-frame mirrorless alternative. If you want a sneak preview of what that'll look like, the A7S is your ticket to the future.
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