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The author would like to thank Isotta for providing the pair of RED64 strobes used in this review.
 

Known first and foremost for their sleek, red anodized aluminum housings, Italian manufacturer Isotta has a reputation for high-quality products. In 2025, the company made its second foray into the underwater strobe market with the RED64. (Technically, this is the RED64 “Mark II”—but Isotta continues to market it simply as the RED64.)

On paper, the updated RED64 promises impressive power output, distinctive (if slightly unconventional) ergonomics, and beautifully even light produced by a large circular flash tube. But as every underwater photographer knows, specs rarely tell the whole story. Guide numbers, watt-seconds, recycle times, and beam angles may look excellent on a product listing, but true performance is only revealed with time spent underwater.

To see how the RED64 fared in the real world, I took it all around Florida and up to the chilly rivers of Alaska. I shot everything from delicate seahorses to sharks to highly reflective salmon. These environments presented a wide range of lighting scenarios that gave me a great feel for how the strobe copes in the wild.

Over many dives (or dips into rivers) the RED64 proved itself not just as a stylish addition to Isotta’s lineup, but also as a serious photographic tool. That said, you’ll have to read on to find out all the ins and outs of this flashgun and whether you feel the premium price it commands is justified.
 

Powerful strobes like the RED64 are useful when shooting big animals against the sun (Sony a1, Sony 28–60mm f/4–5.6, Isotta housing, Nauticam WWL-1, dual Isotta RED64 strobes, f/11, 1/250s, ISO 200)
 

Face to face with a bar-eyed hermit crab: His wide-eyed appearance certainly gives one the feeling he is impressed with the RED64! Or at least he likes that his colors match… (Sony a1, Sigma 105mm f/2.8 DG DN Art Macro, Isotta housing, dual Isotta RED64 strobes, f/7.1, 1/200s, ISO 100)

When I first examined the design of the RED64 on Isotta’s website, I was a little puzzled. Nearly every strobe I’ve used places its controls on the back of the unit—the side facing the photographer—so that’s what we’ve come to expect. Isotta has taken a different approach with the RED64, and before I got my hands on the strobes, I was fairly certain I would not get along with the ergonomics of the mode and power paddles.

Imagine my surprise, then, when I unboxed them and picked one up. The power control lever, inarguably the adjustment you’ll make most often during a dive, falls exactly where your thumb or index finger naturally rests when gripping the rear of the strobe. Rather than feeling awkward, the layout quickly proved to be intuitive and comfortable. After a short time in the water, adjusting power became second nature, and I no longer gave the unconventional placement a second thought.
 

A pair of Isotta RED64 strobes with white diffusers, attached to an Isotta housing. You can see the control panel for this strobe model, unlike most others, is on the top of the flashgun instead of on the back. While I was initially unsure how this would work in the field, I actually came to quite like it
 

The power paddle features clearly defined stops, which provide reassuring tactile feedback as you move between settings. That said, I would welcome slightly more pronounced resistance at each stop. As it stands, it’s possible to nudge the lever inadvertently when grabbing the strobe to reposition it, particularly when working quickly. A touch more “bite” to the stops would further refine what is otherwise a very well-considered ergonomic design. While the RED64 features both electronic and fiber-optic triggering capabilities, as well as HSS, the lattter requires a special flash trigger that I did not have access to, and I only used the strobes via fiber-optic cables. Throughout my testing, the RED64 never missed a beat or misfired.

Isotta RED64 Specifications

• Guide number (underwater): 22
• Light coverage (without diffuser): 130º
• Color temperature: 5300K
• Recycle time (full power): 3.5 seconds
• Flashes per charge (full power): 300
• Operational modes: Manual, TTL, HSS (Sony/Canon/Nikon)
• Connections: Fiber-optic/electrical (S6)/slave
• Power source: 8 rechargeable AA NiMh batteries
• Weight (water): 230g/0.5lbs
• Weight (air): 1500g/3.3lbs
• Depth rating: 330ft/100m

Clockwise from top left: The face of the RED64 showing the bayonet front and the circular flash tube; the rear of the strobe showing the lack of controls on the back and the battery compartment cover; the profile of the RED64 in all its red glory; the unconventionally-placed power level on the top of the strobe.
 

Intuitive controls allow for easy adjustments of power in close-focus-wide-angle scenarios like this of a spotted scorpionfish. Subtle lighting mishaps are easy to diagnose in CFWA images so being able to fine-tune lighting is nice for quality of light (Sony a1, Sony 28–60mm f/4–5.6, Isotta housing, Nauticam WWL-1, dual Isotta RED64 strobes, f/14, 1/20s, ISO 200)

Power is a funny thing when it comes to underwater flashguns. Every manufacturer measures and quotes strobe output differently, which makes it difficult to compare models on paper. Without testing them side by side in identical conditions, it’s hard to know exactly how powerful a given unit really is. For what it’s worth, the RED64 has an underwater guide number of 22, but the real issue isn’t the number—it’s a question of whether the strobe delivers enough power for real-world use. In my experience, the answer is yes. It has plenty of output, and at no point did I find myself craving more. The caveat here is that I rarely shoot big reef scenes or many scenarios when obscene power is absolutely required. Of course, it is always nice to have!

The strobe offers 10 power levels. I appreciate the ability to dial the output right down for close-focus-wide-angle or macro work, though I do feel the jumps between the higher power settings are quite pronounced. A few additional incremental steps at the top end would provide finer control and make exposure adjustments more precise.

The RED64 is powered by eight AA batteries that are held together in a battery caddy. The battery life seems to be quite good, and I never found myself running out of juice. Happily, the RED64 doesn't seem to have any sort of battery drain either, so if batteries are left in overnight, they aren't run down by morning. The strobe comes with a charging dock that allows the user to place the entire battery caddy, with batteries installed, on the dock and charge them all together. Brilliant.
 

A goliath grouper swarmed by baitfish: Poor technique on my part meant this image isn't lit as nicely as it should be, but the RED64’s did a nice job of delivering power for lighting the grouper while not overexposing the baitfish (Sony a1, Sony 28–60mm f/4–5.6, Isotta housing, Nauticam WWL-1, dual Isotta RED64 strobes, f/10, 1/15s, ISO 100)
 

Flash duration is something I haven’t focused on much in previous strobe reviews, largely because it hasn’t been a major consideration in underwater photography—until now. With the rise of global shutter cameras, particularly the Sony a9 Mark III, flash duration is becoming increasingly important. Put simply, flash duration refers to how long the burst of light from a strobe actually lasts. The shorter the flash duration, the higher the shutter speed you can effectively use. Conversely, a longer flash duration limits your ability to take advantage of very fast shutter speeds.

The good news for anyone considering the RED64 is that its flash duration appears fast enough to sync with the Sony a9 Mark III at speeds up to at least 1/10,000s. While such extreme shutter speeds have limited applications underwater, they do open up creative possibilities. For example, the seahorse image below was captured in just four feet of water, in bright sunlight, at f/2.8. Achieving that look at such a wide aperture would not have been possible without the ability to sync at exceptionally high shutter speeds and without a strobe with a flash duration quick enough to keep pace.
 

The RED64 has a quick enough flash duration to illuminate images even at 1/4000s natively, without being in HSS (Sony a9 Mark III, Sony 90mm f/2.8 Macro, Nauticam housing, dual Isotta RED64 strobes, f/2.8, 1/4000s, ISO 160)

I know I really do harp on this in every strobe review I write, but a strobe’s light quality is ultimately its single most important trait. Sure, a flash might have the coolest features, the best ergonomics, or the biggest power rating on paper, but if what comes out of the front isn’t aesthetically pleasing, none of that really matters. Specs are easy to market; beautiful light is what actually shows up in the final image.

With that in mind, the circular flash tube of the RED64 really holds its own on the light quality front. Right out of the box, it produces a very pleasing light that feels balanced and natural on subjects. There’s a smoothness to the beam and an evenness across the frame that is really very lovely.
 

Wonderfully soft light for this fantastically gnarly sockeye salmon: A wide, soft flash beam is invaluable for close-focus-wide-angle imagery, which just so happens to be my favorite style of photography! When paired with its dome diffusers, the light quality from the RED64 rivals just about any strobe I’ve used (Sony a1, Sony 28–60mm f/4–5.6, Isotta housing, Nauticam WWL-1, dual Isotta RED64 strobes, f/11, 1/15s, ISO 100)
 

Diffusers elevate the light quality even further. Paired with Isotta’s standard white dome diffusers, the RED64 produces light that is among the nicest quality I have seen from a strobe in this class. The spread, softness, and falloff are genuinely beautiful, creating a flattering wrap that works exceptionally well for close-focus work or while shooting bright or reflective subjects like sharks. The soft, wide beam is also forgiving—if your strobes are mispositioned, you can often still come away with a usable image. 

If I have one small qualm, it’s that the diffusers are almost too good. They do cut a significant amount of power, and I sometimes found myself wishing for an option that was just a bit “thinner.” In situations where ultimate softness isn’t required—or when you really need to squeeze every bit of output from the strobe—a slightly less aggressive diffuser would offer more flexibility. It’s a minor critique, but having that middle-ground option would make an already excellent strobe even more versatile.
 

No blown highlights and soft shadows: This shallow depth-of-field image of a dwarf sand perch shows just how soft the light from the RED64 is—especially with the optional dome diffuser in place. For some, the light might be a bit “cool,” and warming diffusers would be beneficial in certain scenarios (Sony a1, Sigma 105mm f/2.8 DG DN Art Macro, Isotta housing, dual Isotta RED64 strobes, f/4.5, 1/200s, ISO 100)
 

One of the main benefits of a circular flash tube is a “forgiving” beam. Even less-than-perfect strobe placement for this image didn't result in a botched shot or blown highlights. While the lighting isn't flawless, the image is still perfectly usable (Sony a1, Sony 28–60mm F4–5.6 lens, Nauticam WWL-1, Isotta housing, dual Isotta RED64 strobes, f/10, 1/80s, ISO 100)

Isotta’s second serious entry into the underwater strobe market with the RED64 (Mark II) is an impressive one. Although it sits firmly in the premium price bracket, it justifies that positioning with excellent ergonomics, intuitive controls, and a well-balanced design that is easy to get along with. The build quality is wonderful, designed to withstand demanding use in any environment.

Performance-wise, the RED64 delivers a clean, even beam with a pleasing quality of light and, when paired with diffusers, produces beautifully soft, natural-looking light ideal for any shooting scenario Combined with consistent output, reliable recycle times, and dependable operation dive after dive, the RED64 establishes itself as a strong contender in today’s competitive strobe market. For photographers seeking a reliable, powerful, high-quality lighting solution, Isotta’s flashgun deserves a look.
 

The Isotta RED64 is queen angelfish approved! Check out the wonderful colors and the beautifully soft shadows (Sony a1, Sony 28–60mm f/4–5.6, Isotta housing, Nauticam WWL-1, dual Isotta RED64 strobes, f/11, 1/20s, ISO 200)
 

About the Reviewer: Matthew Sullivan is a Florida-based wildlife photographer who has been diving since he was 10 years old. He has traveled extensively, visiting well-known dive destinations such as Guadalupe Island, Indonesia and the Philippines, but he also likes to dive closer to home in Florida. When not taking pictures underwater, he can be found trekking mountains, or exploring national parks and rainforests in search of new adventures and wildlife encounters.
 

Isotta RED64 strobe

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