Full-frame Sony A7S bucks trend with fewer, larger pixels for great low-light shooting, native 4K video


posted Sunday, April 6, 2014 at 5:00 PM EST


Just half a day before the National Association of Broadcasters kick off their annual tradeshow in Las Vegas, Sony has announced its latest -- and arguably, most exciting -- full-frame mirrorless camera to date, the Sony A7S. (The 'S' standing for "sensitivity", the key goal of this model.) The company has played its cards very close to its chest for this launch, keeping most details of the camera under wraps, so our coverage is necessarily a work in progress. What we do know about the A7S is extremely interesting, though. Low-light shooters and videographers alike are going to be fighting to get their hands on this camera!

In most respects, the Sony A7S is very similar to the A7 and A7R, but there's one critical difference: its brand-new image sensor. This is key for two reasons: It has much lower resolution than is typical these days, especially for a full-frame camera, and that lower resolution has allowed Sony to significantly increase sensitivity. By default, the Sony A7S has a sensitivity range of ISO 100 to 102,400 equivalents for still imaging, and ISO 200 to 102,400 equivalents for video. This range can be expanded for still shooting to encompass everything from ISO 50 to 409,600 equivalents in still shooting, and ISO 200 to 409,600 equivalents for video.

The Sony A7S trades off resolution in the quest for higher sensitivity and native 4K video.

Yes, we've seen a similar range from the Nikon D4s, but we're led to expect a significantly lower level of noise -- and hence, much more useful results -- from the A7S' 12-megapixel sensor than can be derived from the older, higher-resolution 16-megapixel chip in that camera. If that pans out, and we see no reason to expect it not to do so, the Sony A7S should make for one heck of an available-light shooter!

No less important is the fact that the chip can output extremely high-quality, 16:9-aspect, 4K video without line-skipping, pixel binning or downsampling. It's not quite a native sensor readout, as there's still an approximate 1.1x focal length crop, but it's the closest to full-sensor width video we've yet seen from a full-frame imager. (By contrast, Canon's EOS-1D C has a 1.3x focal length crop for 4K video, using only an APS-H sized area of the sensor.) The A7S' near-full width 4K mode means you maintain most of the wide-angle capability of your lenses, have more of the shallower depth of field of full-frame area, and still avoid the sort of artifacts caused by the line-skipping approach used in all other DSLRs for their Full HD output.

No doubt about it: Sony is courting videographers with this camera!

It's important to note that the Sony A7S cannot itself record 4K video, only Full HD, a slight shortcoming caused by its form-factor. (Shooting 4K in-camera would've needed more powerful processing, and would've caused greater heat dissipation requirements.) But you can output uncompressed 4K over the camera's HDMI connection, and then record it on an external device -- something pros will likely prefer anyway, given that it allows greater control over how that video is treated.

An obvious question, given its kinship with the Sony A7R and A7 -- but variance in sensor -- is what autofocus method the new A7S uses. The A7 provides a hybrid phase/contrast detection AF system, while the A7R uses what Sony terms Fast Intelligent AF, a system based solely on contrast detection. So, too, does the Sony A7S, but the company promises better autofocus performance thanks to the larger pixels of the newer sensor. In fact, for low-light autofocus it should best any phase detection system on the market, able to focus right down to -4EV.


Alongside its new camera, Sony has also announced development of a power-zoom lens intended for video capture. As you'd expect, the design includes silent mechanisms for zoom, iris, and focus to ensure the audio track of your video remains clean. The lens has a 28-135mm focal length range, and a constant f/4.0 aperture so that you can zoom during video without the aperture changing.

Sony has yet to announce pricing for the ILCE-A7S, nor when it should be available. Once the company does so, you can expect to hear that information on our news page. In the meantime, read our Sony A7S preview for more details on Sony's newest (and we think, coolest) full-frame, mirrorless camera! We can't wait to get this one in the lab for testing!