Sony A9 III underwater review

Sony has once again revolutionized underwater photography with the Sony A9 III’s coveted, long-awaited, and seemingly unattainable “global shutter.” For years, the idea that every pixel on a sensor could be recorded and sent to the processor instantaneously seemed impossible. What would such an advanced shutter mechanism look like for underwater photography? Well, now we know—and it’s game-changing. 

The World’s First Global Shutter Camera

The Sony a9 III ($5,998) boasts a revolutionary feature known as a global shutter, which allows the image sensor to capture every pixel in an entire image simultaneously. Unlike a mechanical shutter, there are no moving parts involved in the process; it’s entirely electronic. Sony achieved this through their innovative ‘stacked sensor’ design, where each layer of the sensor processes data simultaneously, enabling much faster readout speeds. 

With a global shutter, the Sony A9 III can achieve a flash sync speed of up to 1/80,000th of a second, a significant leap from the typical 1/250 limit imposed by most cameras when using strobes. The global shutter has several benefits for underwater photographers:

1. Capture underwater photos in much brighter lighting conditions (e.g., shallow, tropical water in the midday sun) and properly expose sunlight and sunballs while illuminating your subject with your strobes. The result is a more dramatic gradation from your highlights to your shadows, with the subject isolated and illuminated by artificial strobe light. 
2. Increase your shutter speed to capture photos with black backgrounds in bright lighting conditions. With a few exceptions at very high shutter speeds, this will not affect the light from your strobe.
3. A higher shutter speed allows you to “freeze” a moving subject in your image for better details and less motion blur.
4. If you are not shooting with strobes (which are limited by recycle times), an ultrafast readout speed allows the camera to capture photos extremely quickly – up to 120 frames per second (RAW) burst shooting.

We had the exciting opportunity to be the first to dive with the new Sony A9 III on an experimental blackwater dive in the Pacific Northwest and at some of our local shore diving sites. Conditions were perfect for testing a global shutter – the bright mid-day sun allowed us to push our shutter speeds higher than traditional flash sync speeds and play around with isolating ambient light. The blackwater dive benefited from a fast shutter speed as small, fast-moving critters encircled us. Overall, we are impressed with the results and believe that the Sony A9 III is a gateway to further innovation that will redefine underwater photography. 

We had the exciting opportunity to be the first to dive with the new Sony a9 III on an experimental blackwater dive in the Pacific Northwest, as well as at some of our local shore diving sites. Conditions were perfect for testing a global shutter – the bright mid-day sun allowed us to push our shutter speeds higher than traditional flash sync speeds and really play around with isolating ambient light. The blackwater dive benefited from a fast shutter speed as small, fast-moving critters encircled us. Overall, we are extremely pleased with the results and believe that the Sony a9 III is just our first taste at further innovation around the corner that will redefine underwater photography. So enjoy these images and videos that we captured and read on for our full review of the Sony a9 III for underwater photography… 

Top Sony A9 III Specifications

• 24.6 megapixel stacked full-frame CMOS sensor
• First full-frame camera with a global shutter
• 1/80000 max shutter speed and flash sync speed
• 120 autofocus calculations per second
• 120 fps 14-bit RAW burst shooting
• Native ISO of 250
• 4K/120p recording with full width of the sensor
• 4K/60p recording oversampled from 6K for more detail
• -5 EV lowlight autofocus sensitivity
• Electronic shutter only
• 8 stops of 5-axis in-body image-stabilization
• Weight: 617 grams
• Size: 136.1 x 96.9 x 72.8mm

Incredible 1/80,000 Flash Sync Speed

As we mentioned, the most exciting feature of the A9 III is a flash sync speed equal to the maximum shutter speed on the camera – 1/80,000th of a second. Now, you can use your strobes at any shutter speed. Considering that until now, most full-frame cameras could not shoot higher than 1/250 with strobes, the A9III represents a whole new dimension of creativity. 

In underwater photography, the shutter speed on your camera controls the exposure of your image’s ambient light (e.g., the background). Shooting at much higher shutter speeds allows you to shoot in shallow, clear water directly into the sun. Because the artificial light from your strobes is not affected by shutter speed, your strobe exposures should remain the same while having even more control over your background. It will be easier to capture black background macro photos as well. That said, there is a certain point where the fast shutter speed will eclipse the time it takes for your strobe to fire. This point is sure to vary by strobe brand, and it will be interesting to test at which point strobe power will decrease because the shutter is too fast. 

TTL: Some Considerations

TTL converters and flash triggers allow you to capture photos with accurate lighting exposure from your strobes. A TTL converter will tell your strobes what power to fire at, making them “automatic” and eliminating your need to adjust them manually. During our review, we used an Ikelite Sony TTL Converter ($350) with Ikelite DS 230 strobes which was very accurate (as you can see in our photos). 

While testing higher shutter speeds, we found an unexpected limitation presented by the camera. Attaching a TTL converter or flash trigger to the A9 III causes it to automatically think that a TTL flash is connected, even if you set the converter to “manual” mode. When a TTL flash is attached to the A9 III, it limits the max shutter speed to 1/500th of a second instead of 1/80,000th of a second. So, if you want to take full advantage of the max flash sync speed, it’s essential to make sure you are using a manual flash trigger or manual sync connection.

Say Goodbye to the Rolling Shutter

The A9 III’s instantaneous global shutter eliminates the rolling shutter phenomenon (when an image warps because the sensor is read from top to bottom when taking a photo). Action photos will no longer contain these warp artifacts when shooting with the electronic shutter. This camera is a dream for action photographers, particularly ambient light action photographers, who want to take advantage of the remarkable 120 fps burst shooting speeds of the A9 III.

It is easy to shoot quick pelagic subjects at any speed and not worry about rolling shutter effects with fast subjects. The global shutter also helps make video movement less warped and “jello-like” when panning. Underwater video shooters should be happy with this development as well.

The lack of a rolling shutter has also eliminated issues with banding while taking photos under incandescent light. While this does not benefit underwater shooters, it is an excellent feature.

Autofocus and Burst Shooting

With a 24.6 stacked CMOS full-frame sensor, the design of the A9 III targets speed beyond the global shutter. Because the sensor is stacked, reducing processing times, the camera can do 120 autofocus calculations per second and 120 frames per second burst shooting (14-bit RAW files). The stacked shutter makes the A9 III the fastest-focusing and fastest burst-shooting full-frame camera on the market. Although most underwater strobes could not keep up with these speeds, the A9 III does open up a new dimension of autofocus tracking and burst shooting capability. Action photographers won’t find a better camera on the market, likely for years to come.

In our underwater shooting, we found the autofocus from the Sony a9 III to be on par with our experience with the Sony A7R V ($3,898). Both cameras feature the world’s top autofocus system powered by a dedicated AI autofocus processor. We selected the autofocus continuous mode with autofocus tracking for most of our shooting. It worked spectacularly for blackwater diving – even with the Sony 90mm macro lens. That said, I would have liked to see the camera pick up fish eyes for tracking. It is still not quite on par with competitors like the Canon R7 ($1,399).

Dynamic Range Concerns

As with all technological developments, the Sony A9 III has some drawbacks. The stacked sensor design reduces dynamic range by 1.5 stops, indicated by a native ISO of 250 rather than 100. While diving, we extensively tested how the stacked sensor design of the A9 III affects the details of the image’s highlights and shadows by spending time in shallow water on a bright sunny day and shooting into the sun. You can see in the photo below that while there is some loss of detail in the highlights, there are plenty of sufficient details in the shadows and a nice gradient from whites to blacks. Although I can see a slight difference in dynamic range to similar sun ball photos we captured with the Sony A7 IV and A7r V, the difference is subtle enough to discount the benefits of a high flash sync speed of 1/80,000th of a second. However, you may want to consider another camera if you use a TTL converter, as the benefits of shooting at 1/500 of a second are made even by the native ISO of 250.   

Video Recording at 4K/120p

While the dynamic range limitations might not be ideal for video shooting, the A9 III is still a highly capable video camera, the major highlight being the lack of a rolling shutter. The camera can capture video in 4K/120p with the full width of the sensor and 4K/60p oversampled from 6K for greater detail. Our underwater footage demonstrates how these high frame rates made it easy to slow down footage of jellyfish and macro subjects for further stabilization. We shot all our footage in S-LOG3 and color graded for additional dynamic range and details in our video. 

While Sony might not have designed the A9 III for video shooters, it inherits excellent video features from other Sony full-frame bodies. The camera is still a fantastic option for hybrid photo and video shooters.

Sony A9 III Underwater Housings and Lenses

Two underwater housing options are available for the Sony A9 III – the Ikelite Polycarbonate A9 III Housing ($1,995) and the Nauticam Anodized Aluminum A9 III Housing. We expect future housing releases from most manufacturers, including Aquatica and Marelux. Unfortunately, the Sea & Sea Sony Universal Housing will not be compatible with the Sony A9 III.  

Whether you focus on macro photography, wide-angle, or prefer something mid-range, you’ll find a selection of different underwater lenses compatible with the Sony A9 III. Native Sony lenses provide the best autofocus; however, lenses from other manufacturers are also compatible with the appropriate adaptors.

Conclusions

The Sony A9 III is an engineering marvel, although its $5999.99 price point puts it beyond the needs of the general consumer. Sony’s progress with the global shutter will likely impact underwater photography as significantly as the leap from DSLR to mirrorless cameras. The revolutionary capability of a shutter and sync speed maxing out at 1/80000 and recent improvements in strobe technology result in incredible ambient and artificial light control. Shallow sun ball photos and beautiful black backgrounds are easily attainable with the A9 III. The only potential limitation could be the strobe’s flash duration – an aspect of strobe engineering that did not previously pose any limitations. 

Sony’s global shutter has also opened the door to remarkably rapid autofocus refresh rates and incredibly fast burst shooting. It will be almost impossible to miss underwater action at 120 fps, and with no rolling shutter, the A9 III is the ultimate action camera for bait ball and pelagic shooting. 

Though the A9 III may have limitations in dynamic range, it is Sony’s first attempt at the global shutter. In years to come, this technology will extend to consumer-grade cameras with improvements to dynamic range. One thing is sure: It’s an exciting time to be an underwater photographer.