January 13, 2026

Underwater Strobe Shootout: Apollo III 2.0, Retra Maxi, Seacam 160D, Retra Pro Max 2

Kiliii Yuyan Uncategorized 0 Comments

Forget the art and storytelling parts of photography for a moment: in underwater photography, technology is necessary (sigh). So let’s talk gear. Today, I’m posting my comparative review of the Marelux Apollo III 2.0 underwater strobe, the Retra Maxi, Retra Pro Max 2, and Seacam Seaflash 160D. Thanks to the Apollo review by the incredible Henley Spiers that intrigued me with the possibilities of high-framerate shooting.

Rather than falling for the marketing guff and creative math manufacturers use to sell, I put these strobes through a gauntlet of quantitative testing. I’m looking at power, light quality, and whether they can keep up with a excited and flamboyant leopard seal.¹ I also spent some quality time judging their ergonomics and batteries to see which of the two finalists actually deserves a spot in my baggage. Although, come to think of it, I’m not sure that’s actually a reward.

The Contenders

The strobes I chose are among the most powerful and widely used. The major ones I left out that would have been great to test are the Ikelite DS230 and Backscatter Hybrid Flash 1, but these were what I had available. The three on the left represent the latest generation of strobes, although it seems that increasingly manufacturers are seeing the light and heading towards strobes powered by lithium-ion, particularly in the 18700 and 21700 sizes, used in many dive lights.

If you’ve stumbled onto this review through the interwebs, I am Kiliii Yuyan, a National Geographic photographer, and about a third of my work is underwater. In the water, I have dived the Seacam 160D, the Sea and Sea YS-D3 extensively, and to a lesser extent the Retra Flash Pro Max II and the Ikelite DS160. The Seacam has been the workhorse for its high output power, and I love the ergonomics and quality of light. I primarily dive cold water, sometimes under sea ice, and sometimes in bath blue water.

This review is basically a studio test, to quantitatively test the capabilities of these strobes and the quality of their light in highly controlled conditions. Real life testing will happen eventually, maybe, but that’s just making pictures right? If I find out that these strobes somehow shoot differently under real conditions, I’ll be sure to update this review.

Test Setups and Conditions

• Camera Settings: All strobes were fired from the same position using identical Nikon Z8 settings: ISO 32, f/22, and 1/200s, with the exception of the minimum power images, which were shot at f/5.6 instead, since they were so dim. All batteries are freshly charged and in excellent condition.
• Scene Setup: The scene was setup at 66cm, or 2/3 of a meter. Using an angle measure I measured an output cone from the strobe, the edge of the test frame to the right and left makes for an approximately 120 degree beam angle.
• Brightness Output: I used a script in Photoshop to measure brightness² at different points of the circle of light for every strobe test shot. The first was at the center, the second about midway to the edge, then three more working out to the edge of the beam. This worked remarkably well, giving me far more reliable exposure info than using my eyes to guess. The brightness values are overlaid at the top left of each test shot.
• Flashmeter: In order to gauge the comparative power output of each strobe, so we stop guessing, I backed up the averaged brightness values with a flashmeter, which is included in every shot.³ The flashmeter proved to be a good backup but often did not register any value at all, for whatever reason, and I couldn’t get it to on repeated tries. But the meter generally confirmed the photoshop brightness values well.
• Timing: I made sure to give 3 seconds between each strobe firing, and 30 seconds between sequences of continuous firing.

Strobe Power and Light Quality

Manufacturers are great at fabricating coming up with numbers to beat their competitors. So we have to do our own practical tests.

My shooting style involves balancing strobes against ambient light. Since ambient fills in shadows, softness of light is secondary. I am testing for optimal wide-angle light distribution, which means achieving an even beam coverage that is also wide enough to allow a large margin of error with strobe placement. There’s enough going on underwater and adjusting strobes, especially under ice, is just something I prefer to be reasonably forgiving.

I am also interested in the maximum power output for bright sun days in the shallows and the minimum power output for overcast green water.

Maximum Power

The Winners are, in Order:

1. Retra Maxi– Very Bright (Flashmeter says f/32 at ISO 100)
2. Apollo III – About 0.6 stops below the Maxi
3. Retra Pro Max 2- 82% of the Apollo
4. Seacam 160D- 75% of the Apollo

Minimum Power

The Winners are (ideally, we want the lowest possible minimum):

1. Retra Maxi– Very Dim (Flashmeter says f/1 at ISO 100)
2. Apollo III in MTL Mode (We will talk about MTL Mode later) and Retra Pro Max 2
3. Seacam 160D and Apollo III in M Mode

The Retra Maxi has a very very low minimum power, which is amazing. The Apollo III in MTL Mode and Retra Pro Max 2 have very usable lowest powers. The Seacam and Apollo III in M Mode have an enormous drawback in that their lowest powers are far too bright for many occasions when trying to balance ambient light.

Light Quality (Evenness and Falloff)⁴

I guarantee there is going to be controversy about the light quality assessments here, as people are used to judging light quality by looking at images. I decided to avoid my psychological biases and judged using a more measurable and repeatable method. I judged light quality by looking at the amount of falloff- not only between the center and the outer edge, but also the midway and outer edge. This gives you an idea of the eveness of light, which counteracts hotspots on sharks and ensures the widest coverage out to a 120 degree beam angle.⁵

1. Seacam 160D and Retra Pro Max 2 (even illumination with smooth falloff)
2. Retra Maxi (quite close to the other Retra and Seacam)
3. Apollo III 2.0 (Much faster light falloff)

You can see that the Seacam 160D and Retra Pro Max 2 have incredibly even illumination and very little falloff, with the Seacam apparently having a slightly wider beam. This is easiest done when looking at the Percentage-Of-Center numbers. You can see how the difference in value from Point 1 to Point 2 to Point 3 to Point 4 is quite gradual without much loss of brightness.

I was surprised how even and smooth the Retra Maxi’s light quality was- just a little more falloff than the Retra Pro Max 2, which is touted as superior to the Maxi for its light eveness.⁶ However, all three of those strobes have excellent light quality and evenness.

I was equally surprised to find that the Apollo has pretty bad light falloff. For most cases you simply wouldn’t use the Apollo without the diffuser, especially in fast-shooting scenarios where the continuous burst rate is the point, as there is little opportunity to fine-tune lighting in those situations. Look below if you want to see the improvement in falloff with diffusers on- noticeable but still not great.

Color Temperature

It should be fairly obvious that the color temperatures of the strobes are basically in two ranges- around 4500K and around 6000K. The Maxi and Apollo stands out as having the coolest color temperature, something that I would warm up for green cold waters with a diffuser. Not a problem given that green waters are never all that bright, even just below the surface. The Apollo III has a bit of inconsistency in color temperature but it is minor. Overall they are all pretty good.

High Speed Continuous Shooting Part 1

Okay, this is the part you’ve all been waiting. Welcome to my parlor, said the… Right, ahem, back to the testing.

I began my tests by choosing a burst rate of 8 fps, for 12 consecutive frames for one and a half seconds. While a 12 fps rate would be even better, attempting to go any higher than 8 at high power is unrealistic for now. As someone never said, “Don’t ask a unicorn to pull your plow”.

Oh and a note on strobe powers- I started at MAX POWER and then went down by single marked notches, which may or may not be about a half stop each time.⁷ So at MAX POWER it’s 0, one notch down it’s -1, two notches down it’s -2. I also noted what’s written on the actual strobe itself as their power notation.

Test Results

Max Power Continuous Firing, Seacam and Retra: The Seacam and Retra simply cannot sustain continuous firing at their highest power settings. At 8 fps, they miss frames entirely, and when they do manage to fire successive shots, the power output plummets, cutting the light by several stops quickly.

-3 Power Continuous Firing, Seacam and Retra Pro Max 2: The Seacam and Retra are only capable of sustained continuous firing at 8 frames per second (fps) when the power is dropped significantly, 3 notches below max power. Even at this low setting, the power level still falls precipitously during the burst. For example, the Seacam’s brightness drops sharply from 24 to 6, and the Retra Pro Max’s falls from 62 to 16.

Continuous Firing, Apollo III and Retra Maxi: The Apollo has a special Continuous Firing (MTL) mode. Although the MTL mode drops the output about two stops (aka 1/4 max power) (matching the Seacam at 1/4 power and Retra Pro Max 2 at 1.5 stops from max, labeled +2.5), the performance is exceptional.

When firing at 8 frames per second, the Apollo successfully illuminates every single frame. In MTL, at max power, there is a power drop, which is noticeable. It essentially drops one stop within 8 frames. Its power drop over the sequence is dramatically less than the competitors. Moreover, at half the MTL mode’s 1/2 power, the Apollo virtually maintains consistent brightness through 8 complete frames and continues shooting with minimal power loss.

But there is a surprise. When testing the Retra Maxi at lower powers, it actually starts to keep up with the amazing performance of the Apollo III. WAIT… WHAT.

Ok, we have crossed into strange territory. Not only does the Apollo have incredible continuous firing abilities that we have never seen before in an underwater strobe, but now it seems the Retra Maxi may as well. I wanted to test this further, so I started again with a new series of tests comparing just the Apollo III to the Maxi.

High Speed Continuous Shooting Part 2

New tests for 18 continuous frames⁸. This time, I decided to do a more realistic test. 6fps but for 3 seconds, so 18 total frames. This is a good representation of how we shoot underwater, if say an animal is quickly passing by, but also over a sustained few seconds. Like a shark buzzing the tower or a sea lion lunging at the camera.

To make the test between the Apollo III and Retra Maxi as close as possible, I put a diffuser on the Apollo III, since it definitely needs one for most shooting situations.⁹ Without the diffuser you gain 2/3 stop, so the Apollo does gain an advantage, but the light beam coverage is greatly reduced.

Now ain’t this a surprise. When the playing field is leveled, the Retra Maxi and the Apollo III 2.0 basically have the same power maximum output over all 18 frames. The Apollo III 2.0 has a slight edge, about a third of a stop, from my flashmeter measurements. But the Retra Maxi, which is not marketed as a fast continuous shooting strobe at all, is actually a heavyweight contender. And, I might add, the light quality of the Retra Maxi is far superior (see above).

So in order to use the Retra Maxi for continuous shooting, just use it at power level -6 (labeled +1 on the Maxi) or lower, and it will keep up. That’s it.

Ergonomics and Usability

Apollo III 2.0 Ergonomics, or Lack Thereof

Bad news. Let’s talk first about the Apollo III 2.0 and its wierd design choices. Alas, it is highly disappointing that in 2026, the Apollo III 2.0 basically fails on usability and ergonomics. The 80s called and asked for their strobe back. Seriously though, ridiculous design choices hinder operation:

Fiber Optic Port

The design of the fiber optic port is placed low, recessed into the rear panel, and positioned awkwardly on the right side.

This recessed port leaves only a narrow, 90-degree space for the cable plug. As a result, your fiber optic cable is forced to bend at least 90 degrees just to connect, even if you carefully route the cable with ties from the strobe arm above. The result is, on the right side the cable creates a huge loop to snag eelgrass, hands and regulators (gasp). Why on earth the designers created a port that forces fragile optical cables into such tight, willy-nilly bends is absolutely beyond me.

Power Dial/Knob

The power control is usable but determining the power level is difficult:

• Lack of Readability: There is no display LED. The etched power level numbers are tiny and impossible to read, even topside in good light, let alone underwater.
• Ambiguous Pointer: The dial has a line on its axis meant to be a pointer, but you cannot tell which end is indicating the setting. Workaround: Use a paint marker to mark the pointer side of the knob.
• Lack of Precision: Since most useful power levels are within a quarter turn of the knob, it is impossible to precisely identify the power level. This is a huge bummer for those of us that fine-tune the strobe power of left and right strobes so that the light is not just the same on both sides, aka lighting the picture.
• Poor Tactile Feedback: The power dials lacks positive tactile feedback. It is difficult or impossible to discern a small turn (e.g., an eighth or a quarter turn) by feel with gloves on.

Mode Dial/Knob

The mode selection is equally bad in a completely different way:

• Misplaced Indicators: The mode indicators (labels) are written on a completely different side of the strobe than the knob itself, using lines that wrap around the body to connect them.
• Reliance on Clicks: The only practical way to change modes is by memorizing click counts. For instance, it’s two clicks clockwise from ‘Off’ for Manual (M) mode, and turning the dial all the way for MTL mode. Using HSS or TTL requires guesswork when you can’t feel the clicks through gloves.

Focus Light Control

The focus light is activated by pressing the mode knob inward like a button. This action feels strange and is basically impossible to do without holding the strobe with your other hand. I am usually busy holding, oh I don’t know, THE CAMERA when I am underwater.

Retra & Seacam Ergonomics, or This Is How You Do It

I barely have to write anything about the difference between ergonomics of the Retra Maxi and Apollo III 2.0. Just look at the dang picture. The Maxi is incredibly well laid out, with controls that give great tactile feedback and are easy to read. The focus light button is easy to press one-handed. The fiber optic port is in a great, central location that is the same no matter which strobe arm it’s on. Who knew it could be done?

Also, a shoutout to the Seacam, with the best ergonomics of all. The knobs are clearly differentiated in size, the display is huge and easy to read, the battery door is terrific.

Lithium Ion Batteries for the Win

This is the magic sauce. The fact that both the Retra Maxi and Apollo III 2.0 use high discharge (20 amp) lithium ion batteries is what makes it possible for both to shoot so fast and so reliably. And changing batteries is quick, not like the 8 battery jamboree that is the Retra Pro Max 2.

I hate changing 8 batteries per strobe and getting them in the right orientations, both in the strobe and in the charger. It’s minor, but in the field or on the deck of a boat, as is often the case on assignment, it is a complete mess. The less batteries to deal with the better. The Seacam 160D has the easiest battery door to use, which I love. I wish the other manufacturers would take note of that.

The Retra Maxi takes 2x 21700 High Discharge Batteries, from Nitecore. The Apollo III 2.0 takes 3x 18700 High Discharge Batteries, from either Marelux (much cheaper) or Nitecore. Either way I am glad that this where things are going.

Now I know that people are one side or the other on lithium vs nickel metal hydride batteries, as far as travel restrictions, backups and safety. As a professional photographer who always travels with drone batteries and topside strobe batteries, I don’t find adding lithium strobe batteries to be much of a big deal at all. Out of 17 assignments for National Geographic around the globe, the only country that I have ever had issues with is New Zealand, and batteries there are not the issue, but rather carryon weight. For liveaboards, the solution is also simple- carry a lithium ion battery bag that is burnproof. Charge lithiums inside the bag and outdoors.

Conclusion- The Retra Maxi Rocks Hard

I was genuinely surprised about the results of all this testing. I went back and ran some tests again, using the other strobes in the pairs. But the same results occurred. In the end, I believe my eyes and the brightness values were very helpful (thank you Photoshop scripts). In fact, I don’t know that I have ever seen this kind of quantitative analysis in an underwater strobe review. Sure seems useful, wink wink nudge nudge.

Right. Anyway, the verdict is a no-brainer. The Retra Maxi is one of the brightest, smoothest, lights you can shoot underwater (that I have tested, anyway). It can fire away continuously, quite fast, at 6fps for 3 full seconds, at about 2 stops below the maximum power output of the Seacam 160D, which not long ago was the most powerful underwater strobe of all. Wow. Oh, and did I mention that the Maxi has a video light version that outputs 6000 lumens? Yeah, it even moonlights.¹⁰

Yes the Apollo slightly out-classes the Maxi for highest continuous shooting power, by 1/3 stop (or 1 full stop if you remove the diffuser, so that’s something). But that is at the cost of ridiculous ergonomics and poor light quality. The Maxi wins by a longshot.

Now, if you are looking for a great strobe and don’t need high-power continuous shooting, then the Seacam and Retra Pro Max 2 will do nicely as well. But I’ll probably sell everything except the Maxis at some outrageously low price and with the money I can treat myself to… a fancy new snorkel.

Footnotes

1. Leopard seals are quick. I am quicker. Allegedly. ↩︎
2. Over an area of 31×31 pixels, averaged. ↩︎
3. There were some wierd things about using the flashmeter, including that it would sometimes register pre or post flashes that would throw off the reading. Also, the very first image at a fresh power level does not record the exposure value- it doesn’t show until at least the strobe fires once. I made sure to record in my notes the correct exposure value, sometimes testing several times. There were some oddities- the Seacam would not register on the flashmeter at all- why is beyond me. ↩︎
4. My Nikon Z8, at 1/200, usually gives a slight black banding at the top each frame. I rarely ever notice this in real usage, so I just roll with it. ↩︎
5. After a message from Oskar from Retra on testing methodology, I re-did the light quality comparison by only comparing shots where all central brightness values all about the same. It was difficult to get precisely the same central power numbers, but they pretty close. The falloff values don’t vary much between power levels within one f-stop or so. This is also why I use percentage-of-center falloff numbers rather than brightness values. ↩︎
6. I hear that some people still think the Pro Max 2 has superior light quality, but I don’t really see it except for color temperature. ↩︎
7. Don’t ask me, the manufacturers say don’t assume it’s actually a fixed increment. ↩︎
8. Note that I increased the brightness of these frames by 2.5 stops in Lightroom to have a greater degree of precision, so don’t compare the frames in the 6fps section to the frame in the 8fps section ↩︎
9. See light quality analysis above. ↩︎
10. See what I did there, I made you look at the footnotes. ↩︎