Underwater Photography Diopters Explained: Which Macro Lens Is Right for You?

In underwater photography, one rule reigns supreme: the closer you can get to your subject, the better your image will be. This isn’t just an artistic suggestion, it’s rooted in the physics of light and water. Water is a dense and unruly medium for photography. It absorbs contrast, robs clarity, and scatters light in every direction. The more water between your camera and your subject, the more your image quality suffers. That’s where diopters come into play. These seemingly simple magnifying lenses, when paired with macro lenses enable underwater photographers to unlock a world of incredible detail. From the eye of a shrimp to the spiraling pattern of a nudibranch’s rhinophore, diopters allow images that were previously thought impossible.

But as with all photographic tools, not all diopters are created equal. Some are gentle and forgiving, giving new macro shooters a taste of super macro. Others are specialized, delivering extreme magnification but demanding near-perfect technique in return. To choose the right diopter, a photographer must understand how these lenses work, what trade-offs they introduce, and how to manage the challenges they bring, particularly in terms of depth of field and lighting. This article will walk you through those elements and explore several of the most popular models on the market today, including the Kraken +6, Nauticam SMC-1, Nauticam SMC-2, and Nauticam MFO. Each has its strengths and limitations. By the time you reach the end, you’ll know which one suits your setup, your diving style, and the type of images you want to create.

So, What Is a Diopter?

To begin with, what exactly is a diopter? In simple terms, it’s a secondary lens that mounts in front of your main macro lens—typically on a 67mm threaded port or a flip adapter. Much like a pair of reading glasses, it bends light in a way that enables your lens to focus at a much closer distance than it normally could. Diopters don’t replace your macro lens—they enhance it. By reducing the minimum focusing distance, they allow you to fill the frame with much smaller subjects. This makes them ideal for photographing tiny marine creatures such as pygmy seahorses, skeleton shrimp, or juvenile anemonefish.

Diopter Strength and Depth of Field

Diopters are generally rated by their strength, such as +5, +10, or +15. The higher the number, the stronger the magnification. A +6 diopter will gently increase your subject size, while a +15 might fill your entire frame with a shrimp’s eye. That power, however, comes at a cost—and the primary trade-off is depth of field. The more you magnify, the less of the image will be in focus. As the diopter strength increases, your depth of field decreases and can be reduced to just a couple of millimeters (less than 0.1 inch), even if you’re shooting at narrow apertures like f/22. This is why most people recommend using the highest f-stop your lens allows.

While using a high f-stop is certainly the easiest way to shoot, don’t limit your creativity to only shooting that way. You can embrace the shallow depth of field and experiment with wider apertures—but expect your success rate to drop sharply when doing so. The rewards, however, can be exceptional. If you find yourself getting frustrated, just raise the f-stop again to bring things back under control.

Due to these depth of field issues, it can be difficult to get the part of the image you want in critical focus nice and sharp. Older diopters were notorious for not allowing you to use your camera’s autofocus, so you had to shoot in manual focus—rocking the camera in and out until the subject’s eye came into focus, then pressing the shutter.

The good news is that around ten years ago, super macro photography became a hot topic in underwater photography. As a result, diopter quality improved dramatically. This coincided with the rise of mirrorless cameras and their much better autofocus systems. It also pushed premium DSLR manufacturers to step up their autofocus performance—and suddenly, many diopters became autofocus-compatible.

My personal preference is to use autofocus with weaker diopters such as the MFO and +6. But for stronger ones, like the +12 or Nauticam’s SMC range, I switch to manual focus and use focus peaking on my Sony mirrorless camera.

How Does It Do a Better Job Than My Super Macro Mode on My Compact Camera?

The key advantage of using a diopter is that it allows you to fill the frame with your subject and utilize every single pixel. This is fundamentally different from the Super Macro modes found on some compact cameras—like the TG-6—which achieve close focus by applying heavy digital crops, sacrificing image resolution and overall quality.

Modern diopters also address some of the optical issues that arise when using macro lenses underwater. They help correct for chromatic aberration and improve sharpness across the full width of the frame. There’s simply no better way to produce high-quality super macro images than with diopters—digital crops will always compromise image quality.

Managing Light with a Diopter

Another challenge diopters introduce is a reduction in available light. Since your subject is now extremely close to the lens—often within 5 cm (2 inches) or less—this creates issues with strobe positioning. If your strobes are not set up correctly, they can produce harsh highlights or deep shadows. I like to position them as close to the port as possible and angle them inward toward the subject at around 40 degrees.

You can, of course, use tools like snoots with diopters, but it gets tricky due to the lens being so close to the subject. The stronger the diopter, the more difficult this becomes. I also find that when the subjects are this small, you often don’t need such dramatic lighting effects.

Using high apertures also blocks out a lot of ambient light, but this usually isn’t an issue—since you're shooting such a small scene, it’s easy to light effectively with artificial light.

What Diopters Are Available and Why Would I Want Them?

Several manufacturers dominate the diopter space. Nauticam is arguably the most respected brand, offering high-end options engineered specifically for underwater use. Their lenses feature multi-element designs and high-quality glass that maintain sharpness across the frame. However, Nauticam sits at the very high end in terms of pricing, which can make them an expensive way to find out whether you like using diopters or not.

Kraken, on the other hand, offers more affordable lenses that are great for divers just getting started with super macro. They still deliver excellent quality and are releasing new lenses that explore different design directions. My most used diopter is actually the unique Kraken +6 lens.

SubSee and Saga Dive are also well-known brands, but their lenses haven’t seen much development in recent years. While they fall on the cheaper end of the scale, I’ve found them frustrating to work with—they tend to perform poorly with autofocus and make noticeable sacrifices in image quality compared to Kraken and Nauticam. SubSee lenses are often what people buy first (as I did), simply because they’re inexpensive. But many end up disliking diopters entirely because of a bad experience with them. For that reason, I’d recommend skipping them altogether.

In the next section, I’ll only cover the specific models I’ve chosen to use.

Kraken +6

The Kraken +6 diopter is often the starting point for divers looking to dip their fins into the world of super macro. It provides a moderate level of magnification—enough to make a nudibranch’s gills or a shrimp’s face fill the frame, but not so much that you lose all flexibility. This diopter offers a gentle learning curve: you can still shoot handheld, and you won’t be punished with an impossibly shallow depth of field.

The image quality is excellent for the price, with minimal edge distortion and very good center sharpness. It threads easily onto 67mm ports or flip mounts and is light enough to travel with. This diopter introduces you to the world of close-up work without overwhelming you with technical challenges.

That said, it does have its limits. If you’re after extreme detail—like the spirals inside a goby’s iris or the micro-structures on a nudibranch’s rhinophore—the Kraken +6 won’t quite get you there. But for most casual or intermediate macro work, it’s a solid, reliable tool.

The Kraken +6 is the most used diopter I own. It offers a slightly tighter view of a wide variety of subjects, making it very versatile.

Nauticam SMC-1 and SMC-3

The Nauticam SMC-1 and SMC-3 are essentially the same in terms of performance and magnification power. The original lineup included the SMC-1 and SMC-2, but this year the SMC-1 was replaced by a newer, thinner, and sharper model called the SMC-3—making the numbering system a bit confusing. You won’t find the SMC-1 available new anymore, but you can pick up great deals on the second-hand market, as some photographers have traded them in for the newer version.

The Nauticam SMC-3—short for Super Macro Converter—is a professional-grade lens that has become the gold standard in underwater macro photography. It delivers significantly higher magnification than the Kraken, with approximately 2.3x subject size achievable on a full-frame sensor. What truly sets it apart, though, is its optical quality. The SMC-3 is designed specifically for underwater use and features multiple lens elements arranged to minimize chromatic aberration and distortion. When paired with a 100mm or 105mm macro lens, it produces astonishing clarity—even at the edges of the frame.

This lens is best suited for experienced shooters using high-end DSLRs or mirrorless cameras. You’ll need excellent buoyancy control, strong strobe technique, and a lot of patience. With the SMC-1 or SMC-3, you can capture intimate portraits of small marine life with stunning detail: the patterns on an anemonefish’s cheek or the serrated edge of a crab’s claw become fascinating focal points.

The SMC-3 is, however, very expensive—but it's one of the most dependable tools in the underwater macro world, and well worth the investment for serious photographers. It’s often the first diopter that many shooters with pro-level camera systems choose.

The Nauticam SMC-2

If the SMC-1 (or now the SMC-3) represents serious macro, then the Nauticam SMC-2 represents the next level: extreme super macro. This lens is not for the faint of heart. It delivers approximately 3.5x magnification and was designed for photographers who want to fill the frame with subjects smaller than a grain of rice.

At this level, depth of field becomes so razor-thin that an entire dive might be spent trying to get a single shot in focus. Every variable must be controlled—your body movement, current direction, lighting setup, and even your breathing. Manual focus becomes essential in my opinion when using this lens.

But when you get it right, the results can be extraordinary. You’ll capture textures and patterns invisible to the naked eye—minute details on an amphipod’s shell, the crystalline structure of fish scales, or the surface of nudibranch rhinophores at a cellular level.

That said, this is a niche tool. It's not practical for most diving environments and is certainly overkill for casual macro photography. The SMC-2 is a lens you grow into—something to reach for only after mastering the SMC-3 and still wanting to push further into the micro world.

Nauticam MFO-01

Finally, we come to the Nauticam MFO — the Macro to Full-frame Optimized diopter. This relatively new addition to the Nauticam lineup was developed to address a growing need in the mirrorless and full-frame camera world. As more photographers moved to larger sensors, Nauticam responded with a diopter specifically optimized for edge-to-edge clarity on full-frame systems.

The MFO delivers high-quality magnification at low levels, making it fundamentally different from the other diopters in this article. Its purpose isn’t to achieve extreme close-ups, but rather to enhance image quality across the frame. It helps avoid issues like vignetting and corner softness that can occur when older diopter designs are used on full-frame rigs.

I recently wrote a full review of this lens and described it as “a must-have for underwater macro shooters.”

The MFO is ideal for general macro shooting. It delivers subtle magnification, excellent clarity, and optical refinement. Unlike high-power diopters, it doesn’t force you into extreme compositions or punishingly shallow depth of field. This makes it a fantastic all-purpose tool that elevates your image quality without adding difficulty—a true asset in any serious macro shooter’s kit.

So, which one is for me?

Choosing the right diopter depends largely on your camera setup, shooting style, and the subjects you’re passionate about.

• If you’re new to macro and want something user-friendly that won’t frustrate you underwater, the Kraken +6 is an excellent starting point. It offers moderate magnification with manageable depth of field and image quality that punches above its price.

• If you’re aiming for crisp, professional-quality images of small marine creatures with an established rig, the Nauticam SMC-3 is one of the best options available. It delivers impressive magnification and optical clarity but requires solid technique and experience.

• For those ready to specialize and push their skills further, the SMC-2 offers extreme super macro magnification. This lens is niche, challenging, and demands patience, but the results can be extraordinary.

• If you shoot with a full-frame camera and want the best image quality for general macro work, the Nauticam MFO-01 is the ideal choice. It improves edge-to-edge sharpness and avoids vignetting while providing subtle magnification without the complications of extreme macro.

Be aware: as diopter power increases, price rises—and usage tends to decrease. Stronger lenses become less versatile, suited only for very specific, small subjects. For that reason, I always carry the MFO-01 on my camera, a Kraken +6 in my pocket, and my SMC-1 (I haven’t upgraded to the newer SMC-3 as I don’t use it enough to justify it). I’ve tried the SMC-2 but don’t own one—its niche nature and high cost don’t make it a practical purchase for me.

Lastly, I highly recommend investing in the Nauticam Bayonet mount system if you plan to use multiple diopters. It’s a much better solution than flip diopters, which tend to make your camera front-heavy and can interfere with lighting setups underwater.

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• Kraken Macro Lens +6

• Nauticam SMC 3

• Nauticam MFO

• Nauticam M67 to Bayonet to Bayonet Mount Converter II

• Nauticam Bayonet Mount Adaptor for SMC & CMC Lenses