The Sony a7S is the third variation of the full-frame mirrorless a7 series of cameras that Sony has recently released. First Sony released the 24.3 megapixel a7 and 36.4 megapixel a7R, the first mirrorless cameras with full-frame 24mm x 36mm sensors. The recently released a7S seems like sort of the oddball of the three a7 variations: It has only a 12.2 megapixel sensor and at the time of this writing, it costs almost $1000 more than the a7 and $200 more than the much higher resolution a7R. But with that 12.2 megapixel sensor comes some distinct advantages, especially for low-light photography and video.
With the a7S, it seems like like you’re paying more for less. But even with a sensor resolution that is a third the resolution of the cheaper a7R, the a7S offers two things in return: sensitivity and 4K video (sort of*). The A7s has larger pixels than pretty much any consumer level full-frame digital camera. The larger pixel size means that each pixel can collect physically more light. The more light per pixel, the better the signal to noise ratio for that pixel and so that pixel will more accurately detect the incoming light than a smaller pixel would. This means that, all other things being equal, the A7s should be capable of the best per pixel signal-to-noise ratio of any production camera.
Most high end DSLRs’ ISO sensitivity tops out at or 51200 or 102400. The a7S goes a full two stops more: it has a maximum ISO of 409600. Now for all practical purposes, 409600 is an ISO setting that’s probably not going to be used very much for final images, if at all, ever. ISO 409600 is only really applicable to really really dark scenes and the photos are sure to be really noisy, but it also indicates that the other higher ISOs of the a7S should be much cleaner than the competition.
*The a7S is capable of outputting 4:2:2 UHD 4K video via its HDMI port. This means that it’s not actually capable of shooting 4K unless you attach it to a portable external recorder. It can still record regular old HD video in 60i/60p/30p/24p at 1920 x 1080 and 120p at 1280 x 720 directly in the camera. In order to record the full 3840 x 2160 UHD 4k video, you need to plug the a7S into a separate video recorder like the Atomos Shogun which will be available in late September. It should also be compatible with the soon-to-be-released production oriented Black Magic URSA HDMI.
I have heard rumors about the Sony line of mirrorless cameras having clunky interfaces, so at first I was pretty skeptical of what the camera had to offer. My conclusion: it’s just different. Any user transitioning from Canon or Nikon or any other manufacturer will probably need an hour or so with the camera to familiarize themselves with the functionality. The same could be said of transitioning to any new brand. There are definitely some small quirks, but the a7S operates just as I would typically expect from any camera. The biggest thing for me was just getting used to the button locations (important when shooting in the dark) but it was pretty quick to learn. There’s also a lot of menu customization options, much more than pretty much any other camera I have used.
The camera also has a dedicated function (Fn) button. This is sort of like the “Q” button on Canon and Fuji cameras, used to quickly access certain functions of the camera. A step up from Canon and Fuji, the Fn button menu can be programmed with whichever functions the user desires. Similarly, the DISP button can be programmed to cycle through any number of alternate displays for the EVF and LCD.
By default, all of the most important exposure functions like ISO, shutter speed, and aperture are adjustable via three control dials. The front dial near your pointer finger is for aperture, the rear upper dial above the AF/MF button is for shutter speed, and the rear lower dial around the directional pad is for ISO. Exposure compensation has its own dedicated dial and allows for +/- 3 EV of compensation. I’m also happy to see that many of the buttons can be remapped to alternate functions. All of the most important quick access functions like Auto Exposure Lock, Live View magnify, White Balance, and Self-Timer/Continuous have dedicated positions. I added a function to the C3 button for changing metering modes and the down arrow for enabling focus peaking.
With a full frame sensor, the Sony’s a7 line already has an advantage over nearly every other mirrorless camera system. The larger sensor means that the a7S can take advantage of larger, full frame lenses.