The Nikon D850 vs the Sony A7R III for Underwater Photography

Dissecting the world’s best choices in underwater photography
By Nirupam Nigam

If underwater photography is the reason you get out of bed in the morning, then no doubt, by now you have realized that the caliber of your artistry is defined by the images you create and not the equipment you use. That being said, having nice equipment certainly helps. Having the best equipment helps even more. Right now, without a doubt, the best cameras available for underwater photography are the Nikon D850 DSLR and the Sony A7R III Mirrorless full frame cameras. 

As can be expected, both cameras are equipped with top of the line resolution, sensors, processing power, dynamic range, etc. But what is most historic about this comparison of cameras is the comparison itself. For the first time, a mirrorless camera is now a direct competitor with a DSLR for the prize of world’s best underwater camera. This isn’t merely a comparison of brands or specs – it’s a comparison of photographic engineering. 

Jump to a Section

Mirrorless vs DSLR   |   What is Top of the Line?   |   Image Quality

Performance   |   Processing Power   |   Focus

Video   |   Ergonomics   |   Lens and Housing Availability

Recommendations Based on Photographic Style


The Nikon D850 and Sony A7R III is available now at Bluewater Photo!

Mirrorless or DSLR

Before the release of the D850 and A7R III, mirrorless cameras had been thought of as the bridge between compact cameras and DSLRs. But the development of mirrorless cameras with full frame sensors (instead of crop sensors) introduces a conundrum for hardcore DSLR users. Mirrorless specs are starting to become indistinguishable from full frame DSLR specs. So wherein lies the difference? Well now it’s mostly physical – mirrorless cameras don’t have a reflex mirror and thus have smaller bodies. They are also more effective when using the LCD than DSLRs. That being said, the autofocus and low light sensitivity tends to be better in DSLRs. 

What constitutes as top of the line?

With light speed advances in camera technology, it can often be difficult to determine what constitutes as “top of the line” camera system engineering. Recent focus by industry giants has made it clear that improved resolution, low-light sensitivity, processing power, and autofocus are the centerpiece of recent efforts to improve photographic and videographic technology. Developments in resolution and low-light sensitivity materialize as improvements in image quality. Whereas, developments in processing power and autofocus materialize as improvements a camera’s performance. The world-class image quality and performance of these cameras ultimately results in a versatile tool that can take on almost any underwater photographic situation.

Image Quality

Winner: Tie*

Sensors for a New Age

Image quality is a direct consequence of the performance of a camera’s sensor. The frontiers of image quality were pushed further into the realm of impossibility when both cameras made history as the first DSLR and mirrorless cameras in their respective categories to achieve a DxOMark sensor rating of 100. 

A backlit full-frame Exmor R CMOS Sensor of the A7R III continues to offer 42.4 megapixels of resolution with a native ISO of 100. The Nikon D850 backlit CMO sensor now offers a whopping 45.7 megapixels of resolution with a native ISO of 64!

What does this mean for underwater photography?

These recent sensor improvements have resulted in two cameras that offer both exceptional dynamic range and resolution. Being able to shoot with a low native ISO enables you to photograph scenes with high dynamic range (contrast), without losing information (details). This means that in an overexposed or underexposed photo, details in shadows and highlights can be extracted more easily during post processing. This is great in situations where you might be shooting directly into the sun (e.g., sunballs), or in particularly low light environments where you might need to bump-up the ISO. A low native ISO also reduces the amount of noise in an image which is again important in low light environments or while taking long exposure photos. 


Perhaps the most revolutionary aspect of the A7R III and D850’s sensors is the ludicrous megapixel count of 42.4 and 45.7 MP respectively. To the average underwater photographer, such large file sizes may not seem necessary. However, I found that shooting at full resolution with both cameras changed my photography style. Macro photography becomes a particularly more forgiving artform. This is because you can crop almost anything while retaining resolution. Diving with the D850 or A7R III is more akin to taking a microscope underwater than a camera. Even the most boring photo of a fish or octopus can become a beautiful depiction of the almost invisible photophores or eye parasites! Because the resolution is so large to begin with, most crops will still be a relatively large file! There is also the added benefit of being able to print high quality prints for professional use. 

*Although the Nikon D850 has a slightly lower native ISO and a slightly higher megapixel count, the image quality of both cameras is comparable in most cases. 


Processing power and autofocus performance are two important metrics for underwater camera performance. Because of constant improvements in photo resolution, modern camera systems must have comparable processing power to write information onto a storage device. Otherwise, a camera will slow down and need to buffer while the photographer risks missing photo opportunities. This is particularly important when photographing underwater pelagics or other high-speed scenes in burst mode. 

Likewise, fast and accurate autofocus is essential to underwater photography as manual focus modes are not always accessible. Particularly with moving subjects in both wide angle and macro photography. Almost all underwater photographers have experienced the frustration of watching a small fish or crustacean disappear out of frame as the lens continues to hunt. Who knows, in a few years this might soon be a thing of the past!

Processing Power

Winner: Sony A7R III (But the Sony A9 is the real winner)

The Sony A7R III has an updated BIONZ X image processor that is 1.8 times faster than previous versions of the A7R series. This enables the camera to shoot continuously at 10 frames per second with a 76 RAW image buffer up from 5 fps with a 23 image buffer! However, if shooting sports or quick pelagics is the core focus of your photography, consider the Sony A9. The A9 has the fastest shooting speed of any full frame camera on the market at 20 fps and a 241 image buffer.

The Nikon D850 is only slightly slower than the A7R III with 7 frames per second burst mode and a 51 image buffer. But don’t be quick to rule it out when comparing it to the A7R III as processing power is not the only metric of performance. 

It is worth noting that the benefits excellent processing power can only be reaped with a highest performance SD cards.


Winner: Nikon D850

The autofocus of the Nikon D850 is unbeatable. The Multi-CAM 20K autofocus module is Nikon’s best. It includes 153 focus point – 99 of them being cross sensor types and 55 being user selectable. Cross type sensors increase accuracy and minimize focusing errors resulting in an almost magical ability to track focal points. The dedicated autofocus engine also helps the camera process autofocus calculations at a quicker rate. With the ability to focus down to -4 EV, the lowlight AF performance is great for underwater photographer – especially macro photographers who wish to do away with their focus light in the presence of shy subjects. The combination of these capabilities results in focus modes that just might change how underwater photos are taken. For instance, the 3D-tracking AF mode will focus on a single point and intelligently follow that point as the subject moves around the frame. This mode changed my shooting experience completely. I stopped having to worry about the timing and placement of my focus points and began to completely focus my attention on composition – letting the camera take care of focus. Macro photographers in particular will benefit from this ability, especially when shooting small subjects that move around a lot. I except that we will be seeing many more photo of non-stationary macro subjects in the next few years as the underwater photography community adapts to these advances in AF.

One of the Sony A7R III’s strongest improvements was in its autofocus. It has 399 phase-detection AF points and 425 contrast AF points – 400 more contracts points than the A7R II. This has resulted in AF significantly quicker than the A7R II. However, the A7R III cannot match the AF speed of the Nikon D850 by any means. When shooting wide-angle, the A7R III’s AF speed is sufficient and you won’t see a considerable difference in performance from the Nikon D850. Macro photography is where the A7R III’s AF performance cannot match the D850s. When shooting macro, I found the A7R III could spend a considerable time hunting for focus points – especially in low light situations. 


Winner: Sony A7R III

One of the pride and joys of Sony’s mirrorless cameras are their video capability. The video performance of the A7R III is something to behold. The A7R III offers 4K resolution, 5-axis stabilization (reducing wobbles in hand-held videography), 120 fps @ 1080p, hybrid log gamma compatibility, a Super 35 mode, among other upgrades. Combined with increased battery life, the Sony A7R III is a formidable tool for underwater videographers. Check out our underwater video test where we were particularly impressed by the A7R III’s capability. 


The Nikon D850 should be commended for its 4K video with improved underwater white balance. However, Nikon has never had quite the reputation for video as compared with Sony. And Sony went all out for the A7R III.

Ergonomics and Handling 

Winner: Tie

When it comes to ergonomics and handling, both cameras have their pros and cons. One of the most obvious benefits of mirrorless cameras over DSLRs is their size. The Sony A7R III is 5.0 x 3.8 x 2.9 in. (127 x 96 x 73.7 mm) and 1.45 lb (657 g) vs the Nikon D850 clocking in at 5.75 x 4.88 x 3.11 in. (146 x 124 x 79 mm) and 2.22 lb (1005 g). Although weight varies based on lenses, housings, ports, and accessories; generally, I found the Nikon D850 to be heavier both above and underwater. While I did not use float arms when testing the cameras, I think it’s possible to use the Sony A7R III without floats. On the other hand, using the Nikon D850 without floats was fatiguing to the point where it affected my shooting ability. The underwater drag of the of the Nikon D850 is also slightly more than the Sony A7R III. This makes it easier to dive off the shore, in current, and in surge with the A7R III. However, the A7R III is still a large camera for a mirrorless camera. If size is a real factor in your camera decisions, I would consider the Olympus OM-D EM-1 MK II for a smaller but high-quality mirrorless camera. 

Navigability, on the other hand, is superior in the Nikon D850 over the Sony A7R III. The A7R III’s menu system remains confusing when compared to the D850’s, making it more difficult to change settings on the A7R III. It is also necessary to make a few essential, but difficult to find setting changes before taking the A7R III underwater (e.g., automatic photo replay after capturing and image). 

It is important to note that the view finder on the D850 functions much better than shooting in live view, whereas live view is best on the A7R III. One camera is not better than the other – it is a merely a matter of preference.

Lens Availability

Winner: Nikon D850

Nikon has a strong legacy of excellent quality and availability of full frame lenses. This is particularly notable in the wide-angle category when compared to the options for the A7R III. Wide angle photographers should know that there is no dedicated fisheye for the A7R III. However, the 28mm prime lens can be coupled with the fisheye conversion lens to give the widest possible angle of view. 

Check out our full reviews of the Nikon D850 and Sony A7R III for a full list of lens recommendations. 

Housing Availability 

Winner: Tie

There is no lack of high quality, functional, underwater housing for both cameras! Housings are available by leading brands such as Nauticam, Ikelite, Acquapazza, Aquatica, and Sea & Sea. 

Check out our full reviews of the Nikon D850 and Sony A7R III for a full list of housing recommendations.

Final Verdict? It Depends on You

When comparing cameras, there can never be a winner or loser. Cameras are tools. Different tools are made for different tasks. So the best question to ask is not what camera is better, but instead, what type of underwater photographer are you? If you can answer that question then you can better understand what camera would be suited for your needs as a photographer. 

For the Wide-Angle Photographer: Nikon D850 or Sony A7R III with a Metabones adapter 

Because image quality and autofocus in wide angle are so similar with both cameras, the Nikon D850 is the choice camera for wide-angle photographers due to lens availability. The Nikon 8-15mm, Tokina 10-17mm, Nikon 16mm 2.8 fisheye, Nikon 16-35mm 4.0, Nikon 20mm 1.8G and Sigma 15mm 2.8 fisheye lenses are all excellent wide-angle choices for the D850. Nikon’s low light focus performance is also better which can benefit in limited-visibility wide-angle photography. 

The A7R III is limited to a fisheye conversion lens with the Sony 28mm prime lens, the Sony 16-35 mm f4, and wide angle wet lenses. However, when using the Metabones adapter with Canon lenses, more high-quality lens options open-up. This can make the A7R III rival the D850. 

For the Macro Photographer: Nikon D850

Photographers looking to take split second macro photos with difficult lighting situations and tough subjects will want to consider the Nikon D850. As it can be difficult to take macro photos with full-frame cameras, I was surprised with how exceptional and effective the D850 was. The focus is the quickest and most effective we have seen for a macro set up! Combined with 3D-AF tracking, this camera will do all the worrying about focus for you. All you need to do is compose your image. The D850’s effective low-light sensitivity means quick focus without a focus light if you’re shooting sensitive macro subjects. 

But what was most apparent was that the Sony A7R III has not yet broken some of the last remain shackles of mirrorless cameras. The Sony 90 mm macro lens is a great lens, but the camera will hunt for focus. It is noticeably slower than the D850. 

Regardless, what is most noticeable about these two cameras when shooting macro is the resolution. One could argue that the resolution itself adds 100 mm of focal length to any lens you shoot with as you can still pull high quality images from extreme crops. The details captured by these cameras will astound you.

For the Pelagic/Action Photographer: Sony A7R III/Sony A9

When a speedy tuna or shark makes a quick pass at your camera, the one thing that can make or break your encounter is the frame rate in burst mode on your camera. Although the A7R III shoots 2 fps higher than the Nikon D850, the Sony A9 is the real winner here. 20 fps is just astounding. The A9 was developed specifically for this purpose. It’s amazing processing power enables you to take hundreds of shots before the camera needs to stop to load files. 

For those worried about the A7R III’s autofocus – the autofocus is much more effective shooting wide than macro. In most pelagic situation there is a good amount of light so the AF will function like the D850.

For the Underwater Videographer: Sony A7R III

As mentioned before, the A7R III’s video capability is exceptional. Underwater videographers will want to consider this camera if they are looking for something with great 4K capability, but would also like the ability to shoot excellent, top of the line images. 

For the Casual Photographer: Sony A7R III

Both cameras require completely different diving styles entirely. The A7R III is the least intensive of the two cameras to shoot. Because everything is composed using the LCD screen, I found that I had ample opportunity to watch my subjects without needing to spend all my time looking through a viewfinder. In fact, when compared to shooting with the Nikon D850, I felt like I could actually experience the dive and take photos at the same time. The D850 requires a lot of concentration on looking through the view finder and eats up your ability to just enjoy the dive. The A7R III is lighter and slightly more streamlined which makes for a better swimming experience. 

For the Beach Diver: Sony A7R III

Aforementioned, the Sony A7R III is lighter and slightly more streamlined than the Nikon D850. I found it easier to beach dive with and get through surf.  

For the Fashion Photographer: Nikon D850

Fashion photographers often can manipulate conditions to their desire and need the crème de la crème of tools to worth with. The Nikon D850 is going to be the camera of choice due to low light performance, lens availability, and image quality. Areas where the A7R III excels, such as burst shooting, video, and physical size, are not as much of a priority in a studio. 

The Nikon D850 and Sony A7R III is available now at Bluewater Photo!



Nirupam Nigam is the Editor-in-Chief of the Underwater Photography Guide and the President of Bluewater Photo - the world's top underwater photo & video retailer. While growing up in Los Angeles he fell in love with the ocean and pursued underwater photography in the local Channel Islands. After receiving degrees in Aquatic and Fisheries Science and General Biology, as well as a minor in Arctic Studies, Nirupam worked as a fisheries observer on vessels in the Bering Sea and North Pacific. Since then, Nirupam has been a full time underwater photographer and photo gear head. Check out more of his photography at!


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