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The author would like to thank Retra Underwater Technology for supplying a pair of Pro Max II strobes for the purpose of this review.
 

A super-wide beam isn’t necessary for close-focus wide angle, but very welcome if you also intend on illuminating a cavern wall behind! From memory, I had something like 5% or 6% power on the Pro Max II for this shot, but it’s great to see how much soft light spreads through darkness at such a dimmed setting (Canon EOS R5 II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, dual Retra Flash Pro Max II strobes with dfiffusers, f/11, 1/50s, ISO 1250)
 

Over the past eight years, Retra Underwater Technology—“Retra” for short—has earned a solid reputation as a manufacturer of high-end underwater strobes. From their early days producing the Retra Light Shaping Device (LSD) in 2011—one of the first optical snoots on the market—to launching the original Retra Flash in 2017, the Slovenian company has steadily refined both the electronics and ergonomics of their flashgun designs.

In this article, I’m reviewing the fifth generation of their flagship model—the Retra Flash Pro Max II, which started shipping in July 2025. My findings are based on more than 80 hours of shooting over four months in Australia’s temperate and tropical waters, by day and night, on subjects ranging from super-macro critters to manta rays, taking over 14,000 photos over this period.
 

The test rig in Bass Point, NSW, Australia: Canon EOS R5 Mark II in a Nauticam housing with dual Retra Flash Pro Max II strobes

Quality of Light and the Evolution of Retra Strobes

I had a taste of the original Retra flash during a trip in 2018, and I immediately placed my pre-order for the then-forthcoming Retra Flash Pro, which promised further improved quality of light via the introduction of a circular flash tube, while doubling down on the sturdy ergonomic design which I loved on the first-generation Retra.

When my pair of Retra Flash Pro arrived in 2020, they quickly became my workhorses—I loved their very wide beam, soft light, gradual fall-off from the center, and the slightly warm color temperature (4900K natively, enhanced to 4400K with Retra’s wide-angle diffusers). These attributes together make up what photographers loosely call “quality of light”—and for me, Retra had nailed it.
 

I was fully content with the quality of light of my second-generation Retra Flash Pro strobes, but the battery life and recycle time were their weak point (Nikon D500, Tokina 10–17mm f/3.5–4.5, Nauticam housing, dual Retra Flash Pro, f/10, 1/60s, ISO 200)
 

I highlight the second-generation light quality because subsequent two generations—the Pro X and Pro Max—have maintained a very similar light output, while bringing gains in power efficiency (third and fourth generation) and ergonomic improvements (fourth generation).

I’ll take this opportunity to clear up a common misconception: You can't measure how much light a strobe emits by looking at its power rating in watt-seconds (Ws). That number only tells you how much power the strobe consumes; how much it produces depends on how efficient the design is. By optimising the electronics (inside the strobe) and the optics (front of the strobe), Retra has managed to progressively improve battery life and reduce recycle time, while using the same AA-sized Ni-MH rechargeable batteries.
 

A critically endangered giant guitarfish, hiding under the sand: The wide and progressive light fall-off of the Pro Max II make it easy to evenly illuminate a large foreground (Canon EOS R5 Mark II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, dual Retra Flash Pro Max II strobes with diffusers, f/13, 1/60s, ISO 500
 

Left: My second-generation Retra Flash Pro. Right: The fifth-generation Retra Flash Pro Max II. The front of the strobe hasn’t changed in size but the optics have been redesigned over time to improve power efficiency (increased battery life, reduced recycle time)
 

For the fifth generation, Retra looked for a way to increase brightness meaningfully, without crushing the battery performance. The result is the Pro Max II, featuring a subtly redesigned, slightly more focused and much brighter beam, with a claimed +65% increase in light output. Retra told me the native beam was so wide in previous generations that diffusers wouldn’t make much of a difference, aside from softening the light and changing its colour temperature. Indeed, many Retra users shoot their strobes without diffusers. With the Pro Max II, you do need diffusers for the widest beam, but with diffusers off, you now have a slightly tighter beam on hand whenever you want the light to travel further, e.g., for big animals or more distant scenes.

Retra does not publish a beam angle figure, which I’m told is hard to measure when the edge of the beam is so soft. In practice, I find it wide enough to give room for error in strobe placement, yet not so wide that backscatter becomes unmanageable in average visibility.
 

I would rarely take diffusers off, except when I want a more controllable beam. This seadragon was illuminated with a single strobe positioned above the housing and pointing down (Canon EOS R5 Mark II, Canon RF 100mm f/2.8, Nauticam housing, Nauticam EMWL-1, single Retra Flash Pro Max II strobe without diffuser, f/18, 1/250s, ISO 320)
 

Traveling through Fish Rock cave (South West Rocks, NSW, Australia), I didn’t have time to reposition my strobes to suit the cave walls and yet, I am pretty satisfied with the lighting. Top: Original unedited photo. Bottom: With a –2/3 EV exposure change on the right. Quality wide-angle strobes are said to be more forgiving—this is a concrete example of what that means (Canon EOS R5 Mark II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, dual Retra Flash Pro Max II with diffusers, f/13, 1/40, ISO 640)

Wide-Angle Photography with the Retra Flash Pro Max II

For wide-angle photography, I’ve mostly shot my Retras, both the old Pros and the new Pro Max IIs—with diffusers. I value the warmer 4500K color temperature, which makes water backgrounds bluer, after a straightforward white balance adjustment, and the extra softened light is a bonus, even though I wouldn’t mind shooting them “naked.”

After four months of use, comparing shots taken with the second-generation Retra Flash Pro and its fifth-generation replacement (both with diffusers attached), I can confirm that the Pro Max II maintains Retra’s well-known light quality, while delivering a significant increase in brightness. On large scenes, I usually sit in the 37–50% power range, occasionally stepping up to 75–100% in clear water when shooting fisheye. For close-focus wide angle, I didn’t need that much power, stepping down the light in the 3–12% range—but the soft light remains very pleasing regardless of power setting.
 

This large and reflective reef manta ray is the sort of subject where having a wide, soft, bright beam matters. The warm diffusers have resulted in a lovely blue background, whereas the water was more aqua with an average 30-feet visibility (Canon EOS R5 Mark II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, dual Retra Flash Pro Max II strobes with diffusers, 1/80, F/13, ISO 160)
 

Can you believe I used only one strobe for this shot? One was out of battery (user error!) so I shot a whole dive with one Pro Max II above the housing. This bull ray was over six feet long and you can see the strobe light even hit the face of my model (Canon EOS R5 II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, single Retra Flash Pro Max II strobe with dfiffuser, f/13, 1/100s, ISO 500)
 

I shot this sort of close-up image with only 19–25% of power on the Pro Max II (Canon EOS R5 II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, dual Retra Flash Pro Max II strobes with dfiffusers, f/13, 1/80s, ISO 320)

Macro Performance

The Pro Max II is very well suited to macro photography as well. With 17 power levels—from 0.3%, 0.7% and 1% up to 100%—you can dial in exactly what you need for tiny or highly reflective subjects. The extra power settings, especially at the low end, are very welcome, especially for certain macro scenarios.

The strobe remains fully compatible with Retra’s existing lineup of lighting accessories. You have access to a quality optical snoot (the LSD), macro rings, reduction rings, and reflectors (which can also work creatively for wide angle). It’s also worth mentioning that all these accessories have a similar buoyancy (slightly negative in saltwater), meaning you won’t imbalance your rig when swapping light modifiers during a dive.
 

This Sydney pygmy pipehorse is both reflective and tiny. Having 17 brightness level to choose from is handy to precisely dial in your flash exposure for super-macro subjects like this (Canon EOS R5 Mark II, Canon RF 100mm f/2.8, Nauticam housing, Nauticam SMC-3, single Retra Flash Pro Max II with LSD snoot, f/16, 1/200s, ISO 250)
 

A snoot would have sufficed for the goatfish, but I wanted to include the sea pen in the back. A single Pro Max II with a reflector produces a wider beam than a snoot, yet much narrower than the strobe’s native beam. It’s ideal to cover a close-focus wide-angle foreground with excellent quality of light, and you can tune the power down as reflectors focus and brighten the light (Canon EOS R5 Mark II, Canon RF 100mm f/2.8, Nauticam housing, Nauticam EMWL-1, single Retra Flash Pro Max II with reflector, f/18, 1/250s, ISO 320)
 

I find the Retra LSD to be rather a versatile snoot, especially with the Pro Max II punching a lot of light behind. Without a mask and by pulling the strobe back, I was able to cover this whole octopus (about 8 inches across on this image) and had more than enough light for it (Canon EOS R5 Mark II, Canon RF 100mm f/2.8, Nauticam housing, Nauticam EMWL-1, single Retra Flash Pro Max II with LSD snoot, f/18, 1/250s, ISO 800
 

I particularly like snooting with the Retra Flash Pro Max II: The centered aiming light makes it easy to set up your lighting, even more so with the ergonomic enhancement that recently came via a firmware upgrade. (More on this in the PLT section below.)

TTL and HSS

The Pro Max II supports both TTL and high-speed sync (HSS). Like most experienced shooters, I prefer manual flash control, but TTL can be genuinely helpful when task loaded, for rapidly swimming subjects, and for beginners still getting used to shooting underwater. I used the TTL enough to confirm it works reliably on both macro and wide-angle scenes—provided you use a compatible TTL flash trigger. Unfortunately, when it was time to test the Pro Max II’s HSS capabilities, Mother Nature gave me poor visibility and/or cloudy days, so I don’t have good illustrative shots, but if HSS is an important feature for you, I can confirm it is supported by the Pro Max II.
 

I’ve shot this Australian cousin of the bobbit worm with and without a snoot (adjusting the metering mode as needed) and found TTL to produce well exposed photos (Canon EOS R5 Mark II, Canon RF 100mm f/2.8, Nauticam housing, single Retra Flash Pro Max II with LSD snoot, f/18, 1/200s, ISO 400)

Battery Life

Using the optional booster, the Pro Max II runs on eight AA batteries instead of four, improving significantly both battery life and recycle time. I shot exclusively with the boosters attached, and Retra’s claims of around 300 full-power flashes and over 1,000 flashes at 50% felt correct. A caveat: The aiming light takes a noticeable toll on battery life, so if you’re planning on having it turned on a lot (e.g., for snooting), expect to change batteries more frequently than normal.

The battery test function, featuring five levels in 20% increments, has been refined through several generations and firmware upgrades, and while it now seems dependable, I’d always give yourself a safety margin when deciding whether to swap batteries. The night before diving, if the strobe still showed four bars (>80% charge), I knew it would be good for whatever the next day of diving would bring. If it showed three bars (60–80% left), I would consider recharging if I expected to take more than 500 shots and/or using the aiming light a lot the next day. 

Bottom line: The Pro Max II never felt short on battery—save for that one time where I had mistakenly left the strobe in battery test mode for 72 hours, only to find the battery depleted at the beginning of my dive. This was my mistake, but I wish the strobe would go into a “sleep” mode after a set amount of time. That said, Retra tells me this will be addressed by a forthcoming firmware update.
 

This wall is nearly 20 feet tall, and at such a high ISO setting, it wasn’t difficult to illuminate most of it with two Pro Max II strobes (Canon EOS R5 II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, dual Retra Flash Pro Max II with dfiffusers, f/13, 1/200s, ISO 800)

Recycle Time

My biggest grievance with my second-generation Retra Flash Pros was their recycle time. In subsequent models, Retra worked hard to shorten the recycle time. The Pro Max II is rated to keep up with 60fps at low power, which I couldn’t test—nor was very motivated to!—but I did run a series of burst-shooting tests at speeds that I found more relevant to real-life work. 

As with any strobe I test, output decreases gradually during rapid firing as their capacitors don’t have time to recharge fully. What matters is how smooth that drop is and whether the strobe skips frames. Impressively, the Pro Max II almost never stops firing unless you combine high frame rate with high power (e.g., 10fps at 50%), but of course, you still want the exposure to be relatively consistent across frames, so we’re looking for a smooth light decrease.

My test protocol: I burst-fired a Pro Max II at various speeds using a portion of my kitchen wall as a target and compared the resulting shots for exposure consistency, using both my eyeballs and scrutinizing the histograms. This article would get very boring if I included every test shot, but here are a few examples showing the first 10 shots, at various settings. Note that I’ve changed exposure parameters between series; what matters is the consistency within a series.
 

2% power and 10fps	9% power and 10fps
5% power and 5fps	19% power and 5fps
25% power and 3fps	37% power and 3fps

Testing burst shooting performance of the Pro Max II
 

In real life, I’d rarely shoot bursts for more than a second, usually taking up to five shots only, to capture the peak of the action. With that in mind, here are my practical takeaways:

• If I really need to shoot at 10fps, I stay at 2% power or below, unless the subject swims towards me (e.g., sea lion), in which case a progressive decrease in brightness can work well, and I would go up to 9% for brief bursts.

• 5fps suffices for most underwater action, which I’d use at up to 5% for static subjects and perhaps 19% for fast-approaching marine life.

• 3fps is my go-to burst setting when I need lots of power—up to 25–37%—accepting a visible drop in output across the burst.

Overall, the Retra Flash has gotten better with burst shooting, being well suited for capturing macro and close-focus wide-angle action. However, for fast-swimming big animals, strobes equipped with higher-capacity Ni-MH or Li-ion batteries still have an edge.
 

Like all Synganthids, this Sydney pygmy pipehorse can rotate both eyes independently in all directions, making it unlikely to get both looking at the camera. I shoot short 10fps bursts, less than half a second, at 1% power or less, to capture the best look (Canon EOS R5 Mark II, Canon RF 100mm f/2.8, Nauticam housing, Nauticam SMC-3, single Retra Flash Pro Max II with LSD snoot, f/29, 1/200s, ISO 1600)
 

Form Factor and Ergonomics

For a high-powered wide-angle strobe, the Pro Max II is relatively compact—4" wide by 5.8" long (102mm x 148mm long), and adding another inch (25mm) with booster. It is smaller than my old Retra Flash Pro, thanks to the shorter boosters, and noticeably lighter—by 4.2oz or 120g—and less negatively buoyant underwater.

The compact size makes strobe positioning easier, and the greater neutral buoyancy means I don’t need to tighten clamps as aggressively—making lighting adjustments easier in the water.

The mode and power dials have distinct clicks and can be differentiated by touch: the mode dial is slightly taller. The digital display (introduced with the Pro Max I) shows both mode and exact power level, and is easy to read by day and night. Whilst I appreciate this feature, I miss the color-coded indicator that could tell me from a distance whether the strobe was fully on, off, or still in battery-test mode.
 

When boosters are factored in, the Retra Flash Pro (left) is significantly longer than the Retra Flash Pro Max II (right)

Enhancing Snooting via Firmware: Introducing PLT Mode

My only real usability issue with the Pro Max II was the aiming light button, which I found to be very stiff—so much so, in fact, that I had to hold the strobe with my other hand so it wouldn’t wobble when I was turning the light on and off, to aid with precise snooting. When I mentioned this to Retra’s founder, Oskar, he explained the button had been reinforced for durability but agreed the stiffness was not ideal. He proposed a solution that we brainstormed on, and two months later, Retra released a firmware update adding the “Pilot Light Toggle” (PLT) function.

Using Retra app on your smartphone, you can update the strobe and enable PLT, which allows you to toggle the aiming light on/off and adjust its intensity via the very responsive power dial:

• Rotate one click up and immediately back → Aiming light on. Repeat to make it brighter

• Rotate one click down and back → Aiming light off

After three macro dives with PLT, I wouldn’t want to go back, and what started as a solution to a problem has become an advantage of the Pro Max II for snooting:

• No risk of messing the snoot’s positioning when turning the light on/off

• No need to overtighten clamps to prevent the above

• The power dial is intuitive to find by touch, so turning the aiming light on/off can be done by touch, without taking your eye away from the subject

During my first dive testing the PLT function, I stumbled across this photogenic blue-lined octopus. It didn’t take long to reposition my snoot and be ready to take a few shots, before it vanished below a ledge (Canon EOS R5 Mark II, Canon RF 100mm f/2.8, Nauticam housing, Nauticam EMWL-1, single Retra Flash Pro Max II with reflector, f/18, 1/250s, ISO 800)

Maintenance and Flood Resistance

Very much to my liking, the Pro Max II is a low-maintenance strobe. The battery compartment’s two robust O-rings require only occasional lubrication (every four or five battery swaps), and they stay seated firmly when opening or closing the cap—reducing the chance of pinching or twisting.

A built-in leak detector monitors the battery compartment and triggers multiple alerts (audible alarm, flashing pilot light, displaying “LEAK” on the rear screen) if as little as 2mL of water enters. Also, the battery compartment is isolated from the electronics, providing an additional layer of safety and meaning there’s a good chance the strobe will keep working after a flood (with proper rinsing/cleaning). While I haven’t needed this alarm, it’s nice to know it’s there.
 

Sustainability, Durability and Price

As underwater photographers, many of us have witnessed firsthand the impacts of global warming and pollution on our oceans. One way to minimize our human footprint is by choosing gear that lasts, reuse, and—as much as possible—repair or recycle.

When it comes to durability, I can vouch for the two second-generation Retra Flash Pros that have been my main strobes for over four years, enduring countless shore entries, bumping on all sorts of rocks and getting a fair amount of abuse. After four months with the Pro Max II (8,000 shots taken with one, 10,000 with the other one—the app lets you see that), it feels like they’re as tough as their older relatives, both having a monolithic aluminum alloy body.

I haven’t needed to repair a Retra strobe, but the company has a reputation for being very responsive via email and for servicing every product they’ve ever made. They offer a standard three-year warranty, extendable to five years for a small fee, and—importantly—the warranty is fully transferable. This helps maintain strong second-hand value, providing peace of mind for the next buyer.

Seemingly like everything else, Retra strobes are getting more expensive with each iteration: A Pro Max II will set you back $2,100, or $2,300 if you want a booster. However, every shooter who upgrades usually lets go of a previous version second-hand, at a good discount, meaning older Retra strobes can be had at a sweeter price, possibly with some warranty coverage left.
 

A turtle receives a soft kiss of light by dual Retra Flash Pro Max II strobes (Canon EOS R5 II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, dual Retra Flash Pro Max II with dfiffusers, f/13, 1/200s, ISO 800)

Final Thoughts

The Retra Flash Pro Max II is a premium strobe capable of handling everything from super-macro to large wide-angle subjects. With this fifth generation, Retra has significantly increased brightness while preserving the light quality that made their reputation. You do now need diffusers for the widest beam.

Battery life is now excellent, recycle time is sufficient for most underwater subjects (though not class-leading), and everything runs on eight AA Panasonic Eneloop Pro batteries, which are affordable, easily replaced, and airline-friendly. The Pro Max II remains fully compatible with Retra’s accessories, so you can reuse all your lighting modifiers if upgrading from a previous Retra flash.

I have no doubt that we’ll see a sixth generation of Retra’s flagship strobe one day—possibly with lithium batteries, possibly not. But if you choose to invest in Pro Max II strobes now, the long warranty, robust construction, and strong second-hand value mean your investment should hold good resale value, should you be tempted by an upgrade down the track.
 

Soft, wide beam with a very progressive light fall-off: These are great ingredients to light up all sorts of wide-angle scenes (Canon EOS R5 II, Canon RF 24–50mm f/4.5–6.3, Nauticam housing, Nauticam FCP-1, dual Retra Flash Pro Max II with dfiffusers, f/13, 1/200s, ISO 400)
 

About the Reviewer: Nicolas Remy is an Australia-based pro shooter and founder of online underwater photography school and community, The Underwater Club, with members in 18 countries. He serves as an ambassador for Mares and Nauticam, and chairs the jury of the prestigious DPG Masters photo competition. Nicolas’ images have been widely published in print and digital media, and have won over 40 international photo awards. To see more of Nicolas’ work or browse his upcoming workshops, visit: www.nicolaslenaremy.com.

Retra Flash Pro Max II

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