Sony has announced a 3rd camera, the Sony a7s, in the new a7 series. I thought now would be a good time to briefly highlight the features of all.[gallery ids="4558,4557,4556"]*I only do 4K video when attached to an external recording device. Limited to 1080P when recording to internal (SD memory cards)Sony announced a pair of new alpha series cameras in fall 2013. The a7 and a7r are the smallest most feature packed full frame cameras currently on the market. Because these are mirrorless you don't get an optical viewfinder, rather an EVF or electronic viewfinder. And you have a tiltable LCD screen on the back. The bodies of all three cameras are extremely similar- from a distance or even closer they look identical except for the little r or s next to the 7.Features they share

• Same sensor size & processor
• Viewfinder and LCD type and resolution
• size, battery life and only slight difference in weight less that 25 grams difference between all three.
• Wifi and slick NFC setup for that Wifi
• Use SD cards or the Sony Memory Sticks
• Shutter speed 1/8000 to 1/30 of a second

Despite looking very similar AND sharing the same sensor size there are some significant differences, especially with the latest, the Sony a7s. The a7s is designed for video with some groundbreaking features that provide extremely high quality 4k video. The catch is 4k video can only be recorded via HDMI to an external recorder. Using the SD card you are limited to 1080p. It is a little funny to write "limited to 1080p". Times are changing! That "limited" 1080 provides very highbit rates, up to 50 Megabits/second which translates to very low compression and excellent quality. There is also a 720 mode at 120fps for a nice slow-mo video. Sony also mentioned that the sensor has some smarts that let it adjust the dynamic range for the scene. Focusing mode still relies on contrast detection so nothing like the fancy dual pixel AF that Canon offers in the 70D but the professionals that this cameras is targeted at will mostly use manual focus anyway and zebra display(a visual indicator of sharp focus useful as an aid when manually focusing) is possible through the EVF or LCD. The ISO range offered by the A7s is stunning native ISO to 102,400 and boosted you can reach 409,600. This increased sensitivity does allow impressive low light focusing, so even though it uses contrast detection it can do so very well in very low light situations. The camera is still usable by photographers offering 12MP and 5fps.  Not action orientated numbers but again these shots at high ISO will be very clean.The a7 and a7r are very similar - check the table below for more info. All three use Sony's e-mount lenses which has a fair collection and is growing quite rapidly. Read more about the Sony a7s on B&H

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Sony a series summary:

• Sony a7 - Good all around camera - My Video Review
• Sony a7r - High quality stills with excellent detail for landscape shots- My Video Review
• Sony a7s - video - My Video Review