If you are planing on shooting in 4K you needn't worry, the Atomos Shogun shoots all day, or as long as you have power and media available. As you might already know, Sony's a7s does NOT record 4K internally - you need an Atoms Shogun or other external recorder to do 4K.
|Shooting 4K as long as you have power connected|
UPDATE March 2, 2015
I stuck with two NP-F970 batteries instead of the much larger and heavier V-mount batteries.
I've read some reviews that complain about the build quality of the Atoms Shogun and the fact that it is mostly plastic. I don't know anyone who likes plastic, but I disagree this time. The plastic construction doesn't bother me a bit. I like the feel, and I am impressed with the screen quality. It looks great at any angle. The screen can be calibrated and has a pixel density of 325ppi.
I don't usually throw my equipment around. I might be concerned if the recorder was going to be used in a professional news environment where you are shooting run-and-gun video. My friends work news and they beat the hell out of their equipment. Not on purpose, it's just that kind of work.
The Shogun is a touch screen system and the menu and features are implemented very well and quickly accessible. Very intuitive in my opinion. I really like the zoom feature which allows you to check your focus with 1:1 or 2:1 zoom.
As far as I know It's the only recorder that works with the Sony a7s and inputs 4K through HDMI. It will work with other 4K cameras as well, HDMI as well as 12G SDI, backwards compatible to 1.5G/3G/6G SDI and capable of recording in 10-bit. This makes the Shogun obsolete-proof for a bit.
|Tiny Lemo connector bears the weight of four XLR connectors|
The one thing I don't like is the XLR break-out cable. I think this is the weak link in this recorder system. Atomos should re-think this one, maybe an actual box with the XLR connectors that can be attached to the rig somehow. As it stands the four XLR connectors just hang from the Lemo connector.
The audio recording on the Shogun is fine. You're able to record from the camera through HDMI as well as through the two XLR connectors in the Lemo cable. You could connect an Apture V-Mic D2 or similar shotgun microphone to your a7s and have clean audio through HDMI and connect a wireless mic through the Lemo XLR with you favorite lavaliere like I do. The built-in Sony a7s mic is good for reference, I wouldn't trust it for production audio.
I replaced my NEX-VG900 with the a7s and Shogun recorder to shoot 4K. I'm still working on getting the rig and 15mm rod system figured out, stay tuned. I'll let you know what cage and rig I decide on.
I realize that the cost of getting both the Sony a7s and the Atomos Shogun might seem steep and that a comparable 4K system might be had at a lower price, but there isn't any other interchangeable lens full-frame 4K system to be had no matter what cost. Oh yeah, I forgot the Canon EOS-1D C DSLR, that will set you back nearly $8000.
You might prefer Super 35, I don't. I want to use my vintage full-frame Nikon lenses without a crop factor. To each his own.
These products have all been purchased and payed for by me with no help from these manufacturers.