The A7s was announced several weeks ago at the National Association of Broadcasters show. It looks and feels like the A7 and A7R cameras that have come before, but the internals have been completely redesigned to support 4K video.
Really, the only way to tell it's a new camera by looking at the front is the A7s tag, with the 's' highlighted in blue.
Looking at the camera front-on, the textured grip is similar to that on the A7 and A7R.
The lens mounted on this model is the Sonnar 35mm f2.8, one of the first lenses available on Sony's full-frame system, but there is also a 28-135 f4 lens in development.
The 's' in the model name stands for sensitivity, with the A7s able to reach up to ISO 409,600. Sony has released a video to give you an idea of what that looks like in video terms.
The top of the A7s shows no real surprises if you're already familiar with other full-frame models from Sony, though you do have the easily-accessible exposure compensation dial. Recording is still activated using the dedicated button integrated into the rear thumb grip.
At the back, the 3-inch tilting LCD screen boasts a resolution of 1.23 million dots, with all the standard controls you would expect flanking the right hand side.
Like a number of other Sony cameras, the A7s uses a memory card slot that supports both SD cards and its own MemoryStick Duo format. Unfortunately, it's only a single card slot rather than the dual slot setup that would appeal to pro photographers.
Other connectivity options include the previously mentioned HDMI out, plus Wi-Fi and NFC for easy pairing with compatible devices.
Let's delve into the menu system now to see what else the A7s has in store.
The video recording sub-menu will be familiar if you have used any Sony mirrorless camera before. The A7s lets you choose to record in either 60, 30 or 24p in full HD at 50Mbps XAVC S.
AVCHD and MP4are also selectable for encoding if you want, though XAVC S is probably preferable for pro-level workflows. If you want 120p, that's available at a lower resolution (1280x720).
You can also enable dual record mode, which will create XAVC S and MP4 files (720/30p) simultaneously.
Sony is trying to cater to those who want to use the A7s for high-end video applications by including a number of useful features like time code, picture profiles and S-Log2 gamma to expand dynamic range.
You can switch up video mode to shoot in full-frame or APS-C, with the latter giving a super 35mm equivalent view. According to Sony, this APS-C mode gives you access to 120fps shooting in 720p.
Users also get full control over audio levels as seen in the next screen.
While the A7s has a built-in stereo microphone, serious video users will want to attach an external mic for better audio. You can manually adjust the audio recording level in-camera, and monitor it using the onscreen display.
Sony has also announced compatibility with an external XLR adapter.
This is where the fun 4K stuff starts happening. Within the HDMI menu you have control over output, including uncompressed 4:2:2 1080p and QFHD 4K. The A7s uses a micro HDMI connector for output to an external recorder, or even just for displaying photos and videos on a second screen such as a TV.