Sony A7S will cost $2,500 when it ships in July

Editors' note, May 16, 2014: Updated with pricing and availability.

Sony's announced its first 4K-video-capable still camera, a surprisingly big revelation for the low-profile National Association of Broadcasters' show. Based on the same body as the A7 and A7R , but once again with completely different insides, the A7S incorporates a lower-resolution -- but still full-frame -- 12-megapixel sensor. At $2,500 USD for the body, I was correct that it sits above the A7R in the product line, which still costs close to its MSRP at about $2,300 USD.

That's a perfect resolution for a camera like this. It's enough pixels for lots of pro work but few enough to keep a broad tonal range and fast sensor readout, which will minimize lag and processing overhead when shooting video. Ultra High Definition/Quad Full HD (3,840x2,160 pixels) requires a minimum of 8.3-megapixel resolution, while full cinema 4K (4,096x2,160 pixels) needs 8.8 megapixels.

4K recording meets familiar design with the Sony A7s (pictures)

+7 More

See all photos

Unlike the Panasonic Lumix DMC-GH4 , however, the camera can't do any 4K internally, even at lower frame- or bitrates; you've got to rig up an external hard drive and do it via HDMI. And, disappointingly, it only does 8-bit 4:2:2 capture, compared to the GH4's 10-bit. That said, it should have a far better tonal range than the GH4 because of the larger sensor.

And while the potential dynamic range sounds great for still photographers, it has the A7R's wimpy contrast AF system. Sony hasn't yet mentioned pricing, but I suspect that it's destined to sit above the A7R in the product line, which would put the price north of $2,300 (£1,390).

Sony also announced that it has an XLR mic kit and 28-135 f4 FE-mount lens under development.

For your comparative enjoyment: