All 3 models are exactly the same with their physical dimensions and control set and will fit in the Nauticam NA-A7 housing.
For this trip, I decided to use the Sony a7S for its low light performance. All images shot in this review are with the a7s.
Author's note: Although not shot underwater, to see amazing low light performance of the Sony a7S, check out this video.
Super Small Camera BodyThe body of the a7 is very slim, smaller than many other mirrorless cameras with sensors half as big. Even with the body being small, ergonomics for both land shooting and underwater are great. Focus can be re assigned to an AF-ON button on the back of the camera and many of the buttons can be customized for quick access to favorite controls.
Limited Native Lens SelectionThe drawback to the a7 line is the lack of lens selection. At the time I left for the trip to shoot the a7s, only 2 lenses were available for the line, a Sony 28-70mm and a Sony 24-70mm. While this range is good for fish portraits, neither are suited to underwater photography for extreme wide angle or super macro.
New Native Lenses on the WayWhile I was away on a photo expedition, Sony announced a lens roadmap with many lenses coming in the next 2 years. The most notable for underwater photographers is a 90mm macro, and a Sony 28mm that has a wide-angle converter to make it a 21mm rectilinear, and a fisheye converter to make it a 16mm fisheye. We look forward to shooting these lenses when they are released in March of 2015.
Use Your Canon Mount Lenses on the Sony a7Fortunately, a lens adapter is available from Metabones to adapt Canon mount lenses to Sony E mount. The converter includes pass thru AF, metering, and aperture control. The AF speed through the Metabones adapter is too slow for fast moving subjects.
Fortunately, with underwater wide-angle photography, a common technique is to focus on a foreground subject and stop the lens down and you'll have everything in focus. I used this technique with the Canon 8-15mm lens with no issues. For macro, I manually focused the Canon 100mm IS, which is what I normally do anyway.
Great Backup Rig for Canon SLR ShootersIf you already have a Nauticam Canon DSLR system, the Sony a7 will work as a small full frame backup rig to your full size Canon DSLR. Nauticam SLR ports and gears will work with the a7 housing meaning you only need the housing, port adapter, a7 camera of your choice, and a metabones adapter.
For those with old school Nikonos glass, there is a Nauticam Nikonos Lens Adapter for Nauticam NA-A7 housing if you choose to take your Nikonos lenses out of retirement.
Shooting the CameraThe Sony a7 menu system and layout is a step ahead of their now discontinued NEX line. It is geared towards a more advanced user who wants to take control of the camera. The menus are clearly laid out in the same fashion as the RX line and Sony's other mirrorless crop sensor cameras.
Many buttons can be customized to get fast, easy access to often changed settings like ISO and white balance. Focus can be removed from the shutter and assigned to a button on the back of the camera, as you would normally do with an SLR. Quick changes are as easy to make as you would have on any top level SLR.
a7s: Low Light MonsterI chose the a7s over the other cameras due to its low light capability with the 12MP sensor. ISO tops out at 409,500. That's not a typo. While noise is prevalent at 409,500, you can pull a shot off in almost darkness. Using a more pedestrian setting of 2500 to even 25,000 is impressive.
Dynamic range is in excess of 14 stops with this sensor, one of the highest ranges of any camera on the market.
This image was taken a few minutes before sunset which required an ISO of 2500. Any hint of noise is virtually undetectable and the transition from bright to dark areas has no banding.
Sunballs at ISO 50Also impressive is that this camera offers ISO 50 as its base ISO setting. This is great news for sunball shots where there is always a fight to pull in the exposure of the sun and preserve detail. Normally, sunball shots are set at the limits: shutter as fast as the flash sync speed will allow, strobes at full power and aperture as closed as much possible. Depending on depth I was able to pull off sunball shots as open as F8-F14 at ISO 50. Other cameras that have base ISO at 100 or 200 will require F16 to F22 or greater to pull in the exposure of a sunball, and sometimes that's not enough.
Sunballs can hold more detail at ISO 50 with more open apertures. With the a7s, dynamic range and sensitivity show good detail in the light rays and surface.
Pictures from the Sony a7S are very sharp. Detail is held very well.