Sony's A7s matches full-frame with 4K

/ Updated: April 7, 2014 5:24 AM PDT
Sony Alpha A7S
Aloysius Low/CNET

Sony's announced its first 4K-video-capable still camera, a surprisingly big reveal 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.

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.

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:

Canon EOS 70D Panasonic Lumix DMC-GH4 Sony Alpha ILCE-7 (A7) Sony Alpha ILCE-7s (A7s)
Sensor (effective resolution) 20.2MP CMOS
16.1MP Live MOS
12 bits
24.3MP Exmor CMOS
14 bits
12.2MP Exmor CMOS
14 bits
Sensor size 22.5 x 15mm 17.3mm x 13mm 35.8 x 23.9mm 35.8 x 23.9mm
Focal- length multiplier 1.6x 2.0x 1.0x 1.0x
Sensitivity range ISO 100 - ISO 12800/ 25600 (exp) ISO 100 (exp)/ 200 - ISO 25600 ISO 50
(exp)/ ISO 100 - ISO 25600
ISO 50
(exp)/ ISO 100 - ISO 102400/ ISO 409600 (exp)
Burst shooting 7fps
16 raw/65 JPEG
40 raw/100 JPEG
(12fps with fixed focus; 40fps with electronic shutter)
2.5fps (5fps with fixed exposure and focus) 2.5fps (5fps with fixed exposure and focus)
Viewfinder 98% coverage
2.36 million dots
100% coverage
2.4 million dots
100% coverage
2.4 million dots
100% coverage
Autofocus Dual Pixel CMOS
19-pt phase-detection AF all cross-type; center cross to f2.8
49-area contrast AF; DFD Hybrid AF system
25-area contrast AF; 117-pt phase- detection
25-area contrast AF
AF sensitivity range -0.5 to 18 EV -4 to 18 EV 0 - 20 EV -4 - 20 EV
Shutter speed 1/8,000 to 30 secs; bulb; 1/250 x-sync 60-1/8,000 sec.; bulb to 60 minutes; 1/250 x-sync 1/8,000 to 30 secs; bulb 1/8,000 to 30 secs; bulb
Shutter durability 100,000 cycles 200,000 cycles n/a n/a
Metering 63-zone iFCL 1,728-zone 1,200 zones 1,200 zones
Metering range 1 to 18 EV 0 to 18 EV 0 - 20 EV -3 to 20 EV
Flash Yes Yes No No
Wireless flash Yes Yes No No
Image stabilization Optical Optical Optical Optical
Best video H.264 QuickTime MOV 1080/30p/ 25p/24p; 720/ 60p/50p MP4/MOV 4096 x 2160/24p, 3840 x 2160/30p/25p/24p @ 100Mbps (IPB); 1080/60p/ 50p @ 200 Mbps (All I) AVCHD 1080/60p @ 28Mbps, 1080/60i/ 24p @ 24Mbps XAVC S UHD/30p/25p 4K via HDMI; XAVC S 1080/60p @ 50Mbps; 720/120p
Audio Stereo; mic input Stereo; mic input; headphone jack
Optional XLR
Stereo; mic input; headphone jack Stereo; mic input; headphone jack
LCD size 3 inches inches articulated touch screen
1.04m dots
3-inch tilting touch-screen OLED
1.04m dots
3 inches tilting
921,600 dots
3 inches tilting
921,600 dots
Wireless Wi-Fi Wi-Fi, NFC Wi-Fi, NFC Wi-Fi, NFC
Battery life (CIPA rating) 800 shots
(210 Live View)
500 shots
(1860 mAh)
340 shots
(1080 mAh)
360 shots
(1080 mAh)
Dimensions (WHD) 5.5 x 4.1 x 3.1 in
139.0 x 104.3 x 78.5 mm
5.2 x 3.7 x 3.3 in
132.9 x 93.4 x 83.9 mm
5.0 x 3.8 x 1.9 in
126.9 x 94.4 x 48.2 mm
5.0 x 3.8 x 1.9 in
126.9 x 94.4 x 48.2 mm
Body operating weight 27.2 oz
771.1 g
19.8 oz (est)
560 g (est)
17.2 oz
487.6 g
17.2 oz
Mfr. price (body only) $1,119.00 $1,699.99 $1,699.99 tbd
Primary kit $1,349.00 (with 18-55mm STM lens) n/a $1,999.99 (with 28-70mm lens) tbd
Alternate kit $1,549.00 (with 18-135mm STM lens) n/a n/a tbd
Ship date September 2013 May 2014 December 2013 June 2014

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Quick Specifications See All

  • Weight 15.73 oz
  • Sensor Resolution 12.2 Megapixel
  • Optical Sensor Size 23.9 x 35.8mm
  • Optical Sensor Type Exmor CMOS
  • Sensor Resolution 12.2 pixels