GEAR TESTS: Sony A6400 Underwater Camera Review

Jim Decker CEO: Backscatter Underwater Video & Photo

The Sony 6400 is a continuation of the Sony 6000 series of APS-C sensor mirrorless cameras. The camera body is extremely small for the sensor size, and the image quality is the best we've seen for any APS-C camera. Image quality is excellent and the images have really sharp detail and excellent colors.

Housings are very small for this camera, not much larger than a compact camera, especially when used with the 16-50mm kit lens. For this trip we used the Fantasea A6400 housing.

There's a couple of options for shooting this camera. To keep it small, shoot it with the 16-50mm kit lens, and use a wet wide angle lens like the AOI UWL-09 Pro and your favorite macro diopter. Shoot it like a pro and you can add on a lens adapter from Sigma and use a Canon mount 10-17mm for the ultimate wide angle optic. Our preferred macro setup is the Sony 90mm macro lens. It has a much better macro shooting range and will do super macro with a diopter, while the kit lens can't get into the super macro range. For this trip, I shot wide angle with the 16-50 kit lens and the AOI UWL-09 Pro. 

One of the most surprising aspects of this camera was the autofocus capability. It has what Sony calls "Real-time Tracking AF", which is very similar to Nikon's 3D tracking. The AF accuracy and speed are on par with that of the Nikon D850. Tracking is easy to start by pressing the AF-ON button and holding it down to track the subject you locked onto. For the stingray shot I locked onto the eye and the camera tracked the stingray while I let go a flurry of shots to get the perfect image.

A performance downside is that the flash sync speed is a relatively slow 1/160, making it harder for freezing action and getting darker backgrounds for macro. 

For someone who wants a really small rig that delivers great image quality with a great bang to your buck ratio, the 6400 is a great option to look at.

ROBIN DODD Producer

The Sony A6400 is an interchangeable lens mirrorless camera with an APS-C sensor. Its main feature is a new and improved autofocus ability that performs on par with some of our current favorites for AF-tracking, such as the Sony A9 and Nikon D850. For fast-moving subjects and scenes, it is hard to pick a better compact-body tool for the job. By selecting a focus point, such as the eye of a swimming turtle, and holding down the focus button, the camera was able to lock on and maintain focus beyond our expectations. This made it a breeze to capture wide angle shots, especially when paired with the outstanding image quality of the UWL-09 Pro lens from AOI. We shot the camera with the basic 16mm-50mm kit lens inside the new Fantasea FA6400 housing. This polycarbonate housing was lightweight, ergonomic, and super easy to use underwater. It packs a great set of controls, as well as integrated electronic vacuum and leak detection, and an LED flash trigger for rapid firing. If shooting video instead of photo, swap out the flash trigger for an expanded battery pack and you can double the run time of the camera. One of my favorite aspects of the housing is the interchangeable port system, which allows for dedicated semi-wide dome ports, extension rings to accommodate the Sony 90mm macro lens, or just a basic standard port with 67mm thread to use accessory lenses with the 16mm-50mm kit lens (how we shot it). The custom white balance video results still fall short of other cameras and prevent us from fully endorsing this camera for video, but on the flip side, the still image quality and AF tracking make this camera an excellent choice for purely still shooters. This camera is going to provide some of the sharpest image quality from an interchangeable lens mirrorless camera while still being able to fit in your pocket. If you are a shooter that is looking for more than a compact but are not quite ready to commit to an SLR, then definitely consider the Sony A6400 and Fantasea FA6400 housing for an affordable overall system that produces some of the best still images from its class.

DYLAN SILVER Backscatter Team Member

The newest crop-sensor mirrorless camera from Sony, the a6400, has been making waves with its wildly fast autofocus system. I wanted to see how it would fare against the usual suspects in Little Cayman: groupers, stingrays, and schools of snappers and grunts. I used the 16-50 lens and AOI UWL-09 wet wide angle lens for a wider field of view.

The camera had no issues focusing on moving subjects, tracking stingrays, even in a flurry of dust. The focal range with the 16-50 zoom lens allowed me to shoot a wide variety of subjects, from lobster to nurse sharks. With the AOI wet wide angle lens it was necessary to zoom in slightly (to about 19mm) to avoid vignetting, which negated the field of view a little. It was still wide enough to get shots of the biggest subject we saw during our two weeks: the wreck of the MV Tibbetts.

The size and weight of the camera system is very manageable. There's a lot of lens and wet lens options for this system that are ideal for subjects large and small. Overall, it's an excellent camera in a small package for an affordable price.

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