DreiFish

I think round tube flash strobes having way better quality of light than flat tube is something often quoted by people who haven't compared the two. It's an urban legend that should be laid to rest in 2024. I have done comparison testing of several round flash tube strobes, and several linear tube ones. So has Backscatter. My conclusions are that, once you add diffusers to the flat tube strobes, the differences in light quality are pretty hard to notice even in air -- and likely even more minor in water, which diffuses the light further. Here's proof:

My Backscatter HF-1s (and diffuser package) arrived at last, and of course I had to do some comparison testing before getting them in the water. Here's the measurements, compared with the Marelux Apollo 3s, Ikelite DS 230s and Supe D-Pro (among others). Results fairly closely match Backscatter's advertised figures, but they do fall short slightly in terms of power output, flash duration and high-frame rate shooting. Max power for high speed shooting (measured on the 20th shot in the series): Illustrative beam spread, color temperature and illumination power in air (1.4m distance to the wall, 15mm fisheye lens, 1 strobe, F22, ISO 100, Color Temperature set to 5300k). Observations: It's the brightest strobe I tested, about 2/3 of a stop brighter (with no diffuser) than the Ikelite DS230, Marelux Apollo IIIs, and Sea & Sea YS-D3 If I had to guess, it's using 2 of the same flash tubes used on the Sea & Sea YS-D3. However, unlike the YS-D3, the beam is already wide and pretty soft with no diffuser. The YS-D3 cannot be used without a diffuser if you want to avoid significant hotspotting. Color temperature is already decent without diffusers at 6000k. Warmer than the Marelux Apollo IIIs, similar to the YS-D3, and but not as warm as the DS230s. Side by side with the Marelux Apollo III (both without a diffuser), it's brighter, more even, and warmer. You only lose about 1/3 of a stop of light with the flat diffuser, and 1 stop of light with the dome diffuser. Color filter wise, you can get to 5300k (which is pretty versatile) while only sacrificing 1/3 stop of power, and 4450k/4300k with the warm 4500k filter by sacrificing 1/2 a stop of light output. The sweet spot seems to be the daylight 5500k flat diffuser, which gets you great spread with minimal hotspotting, color temperature almost matching the Ikelite DS230, and a very respectable light output at GN31. Basically, it's comparable with the DS230 with this combination in terms of light quality, with much better recycling times, weight, and battery capacity. Not to mention cheaper. Here is the Backscatter HF-1 on the left, YS230 on the right. The color temperature is not so different, but the Ikelite does have a more reddish tint (vs more yellow on the HF-1) which could be beneficial for colorful reef scenes: The dome diffusers don't offer a great tradeoff. You lose an additional 2/3 stop of light compared to the flat diffuser, and beam evenness improves only marginally. Still, they're there if you really want the softest, widest dispersion of light. The ambient light diffusers are an interesting option, rendering light with a 12250-12750k, with a very strong magenta push (lightroom maxed out its magenta correction at 150. But you lose a full stop of light with the flat ambient diffuser and three stops with the dome ambient diffuser. The latter is basically unnecessary for this shooting style in my view, since you're using the flash for fill rather than to restore color, so hotspotting is not a major concern. Flash duration is probably best in class. It's 'only' about 1/300s (not the advertised 1/440s) at +2 power, but flash duration ceases to be a concern if you shot at +1 (1/800s) or 'Full" power (1/1250s). Despite the quick-firing flash tube, you do still lose a fair bit of power switching into HSS mode. 2/3 stop at 1/250s shutter speed, 1 stop at 1/500s, 3 stops at 1/1000s and 4 2/3 stops at 1/2000s. It's best in class for fast speed shooting. At 3fps, it's 2/3 stop brighter than the Supe D-Pro, and a full stop brighter than the Ikelite DS230 and Marelux Apollo III. At 6fps, it's 1 1/3 stop brighter than the Apollo IIIs (and 2 2/3 stop brighter than the YS-D3). At 12 fps, you still get a respectable GN of 8.5 - 2/3 of a stop brighter than the Apollo III. At the end of the day, it's basically better than the Apollo III in every way, and better than the Ikelite DS230 in most ways, though the DS230 still edges it out in power output and light quality if you absolutely must have a 5100k light temperature. When you consider that it's the cheapest of the big strobes, and only $100 more then the Sea & Sea YS-D3, I'm really struggling to see why you wouldn't pick this strobe as the best in class. There's very few areas where another strobe is better. And as a complete package at such an attractive price? This should be most people's end-game strobe.

Alright Andrej. I'll take up your challenge. Let's ignore for a moment that at 50m, there's so little ambient light that you could've achieved the same results even with video lights -- not to mention a pair of Inon S-220s with the soft diffuser at $450/strobe (1/5th the price of the Retras). Sure, you can get great results with your Retras. But you can get equally good results and a soft, wide beam with other strobes too. Here's a shot I took recently at 30m with the Marelux Apollo 3s. Here's an example (not mine) of what the Backscatter HF-1 can do (a bit too red for my taste, but he had them only for 2 dives) And here's something a bunch of 10-year-old photos with a Panasonic GH4 and the original Sea & Sea YS-D1s. And this one? It's not even with strobes, but rather 15k lumen video lights. Just for completeness' sake, here's a shot taken with my old Retra Pros. The point? The Retras are good strobes, but there's nothing that makes them 2-5x better than a half dozen other strobes.

It's not true for all products though.. Nauticam stuff for a while was 25-35% cheaper if purchased in Europe, even accounting for VAT. It still is, VAT exempt for export. But that I believe is due to the 25% tariffs that the U.S. has started charging on Chinese-origin goods. I purchased my Retra Pro strobes in 2021, after the global recession. And I got them for less than $1000 each. The doubling in price has happened in 2 generations and less than 3 years, not 6. Sorry.. but that ain't inflation, that's a deliberate move up-market in pricing from Retra's side. In the same 3 years, the number of features that Retra could claim were 'unique' has halved. HSS? Plenty of strobes do that now too. Wide, warm-ish beam coverage at a reasonable temperature? Ikelite DS230s and Backscatter HF-1s (with diffusers) have Retra beat. Many diffusers to modify the light? Backscatter HF-1. All aluminium construction? Supe, Marelux, OneUW. And the OG Seacam and Hartenberger strobes of course. Retra only went to lithium batteries after Supe, Marelux and Backscatter went there first. Good customer service -- queue Ikelite and Backscatter, if not others. The only unique features left for Retra are deservedly called gimmicks. Moisture alarm that won't save your batteries and makes no difference since the rest of the strobe electronics remain sealed. User-upgradable firmware that solves no actual problems. Did I miss something? Are they? I know at least one trying to sell his strobes to switch to the Backscatter HF-1s (I almost bought them). And for the others.. well, when you spend that much money on anything, it's human nature to try to rationalize that choice.

Could be, I was just guestimating based on my recollection of what the 180mm dome looks like (mine is sitting packed in a closet) and the 10-15mm shorter extension Nauticam recommends in its port chart when using the 180mm dome instead of the 140mm or 230mm domes which don't have any protrusion at the back. In any event, the 180mm dome is definitely not anywhere near a full hemisphere like the 140mm or 230mm domes. The pictures Phil posted look promising in terms of the 20-70s performance with the 140mm dome. Sounds like a potent travel combination together with the Laowa 10mm. Based on this, I would guestimate the Aquatica lens-mount to front of housing 'flange' distance to be around 40mm too. Below chart may be useful when converting port extensions from one housing manufacturer to another. So probably the extension needed for Aquatica is similar to Marelux -- i.e. 20 to 25mm. At least I'd take that as a starting point for fine-tuning. N100 + 35.5mm port adapter should produce the same flange distance as the n120 housings with no adapter, or at least within 1-2mm. This combination only vignettes slightly with the 140mm Nauticam dome at the top and bottom because of the dome hood, which is designed to accommodate a fisheye lens's more limited vertical field of view. Without the dome shade, there's no vignetting. With the dome shade on the left, no dome shade on the right. Both with Nauticam R5C (n120) housing and no extension. Something seems strange about this Phil. The Nauticam N100 equivalent to a 35mm extension on Marelux (i.e. total extension from lens flange of 40mm + 35mm = 75mm) would be 75mm - 26mm (Nauticam n120 flange distance) = ~50mm of total extension. That would be the 35.5mm n100 to n120 adapter + a 15mm extension ring. I've tried the a similar combination on Nauticam N120 (a 20mm adapter) and you get heavy vignetting. I doubt that vignetting would disappear by moving the lens closer only 5mm.. I suspect you need more than that. So it's interesting that there's no vignetting with your set-up on Marelux. Perhaps the Marelux lens mount to front of housing flange distance is closer to 30mm than the 40mm we've been estimating? Could you measure this?

Looks like the price in Europe for the Apollo III is still 1125 Euro -- a bit short of the 1500-1900 estimate 😉 Whereas the Retra Pro Max once you add the power Vault (532.40 Euro) would be.. drumroll.. 2302.40 Euro. Ouch. No idea why the Retras are even more expensive in the E.U. then they are in the U.S....

This sounds about right -- I had estimated it at 65mm based on my extension ring testing with the 140mm dome and Matty Smith custom 427mm dome (both of which are full hemispherical domes). Based on Phil's tests earlier in this thread, I didn't try the 180mm dome because it's not a full hemisphere and has a built in 10mm extension and a more narrow field of view, so I don't think it would be ideal. I've updated my chart here (ignore the I/P/FD figures, they're just made up to arrive at the lens-to-flange distance of 61mm): This matches my results using no extension on the Nauticam N120 housing (for Canon R5C). 5mm extension might theoretically work better if it were available, but 20mm vignettes, and I suspect 10mm would also. I have a problem getting my Nauticam N120 10mm extension ring (v2) to work with my domes and housing though, so no way to test. (There is no 40mm n100-n120 adapter) The 180mm dome has a built in 10mm extension that narrows in. This might work on the n100 housings with a 20mm n100 extension because of the shorter housing flange distance. But as far as I know, there is no 20mm n100 extension ring -- the shortest is 30mm. I suspect the 30mm + 180mm port would vignette worse than the 35mm n100-n120 conversion ring + 140mm dome. This is a great idea, Chris 🙂 I got the same results with the 140mm dome and no extension on Nauticam n120 (Canon R5C) -- the lens hood is visible at the top and bottom of the image. But you can get rid of that by removing the dome. There's no advantage in image quality from using the 180mm dome over the 140mm dome, and you lose field of view/get vignetting. This is because the 180mm dome is not a true hemisphere, and Massimo has estimated that it only really covers fields of view down to about a 16mm focal length. The Laowa 10mm needs a fisheye dome port like the 140mm or 230mm domes. The 8.5 inch acrylic dome is also not a full hemisphere, so it's a compromise in terms of using it with such a wide lens. I suspect you'd get better optical results with the 140mm dome. Have you tried using the 20-70 with the 140mm dome? The 20-70 has a 250mm MFD, so you will lose the ability to focus totally inside the dome at infinity, but that may not matter in practice? If the 20-70 doesn't work with the 140mm dome, your best option will unfortunately be to step up to the 230mm dome, which is closer to a true hemisphere and should support the 10mm extended field of view (especially without the dome hood).

If Aquatica is making a custom dome for it with no extension, then 25mm extension will probably be way too long and vignette. Sounds like the flange distance (distance between the lens mount on the camera and the front of the housing) on the Aquatica housings might be closer to the Nauticam N120 distance of 60mm. On Nauticam N120, you need either no extension or a 5mm extension that doesn't exist. Longer extensions like 20mm don't work because it vignettes. We could give you more advice if you just measure the flange distance on your Aquatica housing.

Thanks Andrej, I wasn't aware Anglerfish made a trigger with optical connection, thought it was electrical only. Great info!

Perhaps they are in the same league, but you can't conclude that just from the watt/s figure. It's just a measure of energy in, not light output out, which is what we mostly care about. There's significant differences in the efficiency of different strobes at converting energy in into light output that come from the choice of electronics, reflectors, flash tube, coatings and beam coverage. For instance, the old Ikelite DS160s are 160 watt/seconds, but a stop less bright than the new Retra Pro Max with its ~130 watt/seconds rating. And the Subtronic 270s report an underwater GN of 22, which may very well offer comparable light output to the Seacam 160d (reported underwater GN of 14) and OneUW 160s (reported underwater GN of 20) despite their much more economic 160 watt/second ratings. (This last part is conjecture -- I haven't tested the three strobes myself, and I'm not aware of anyone that has). But the main point is that watt/second ratings don't tell you anything more about light output than manufacturer's GN ratings. Both can be 'lying with statistics' or creative marketing. I'd encourage you to have a second look at the new Inon S-220s (brighter than the z240) and the Sea & Sea YS-D3, which is significantly brighter than the old Sea & Sea YS-250. Maybe the Ferrari vs. Renault analogy is apt when it comes to build quality and ergonomics, but not necessarily to raw power or efficiency. The better analogy might be a 1990s Ferrari vs. a 2024 Renault. Technology (and even ergonomics) has progressed a lot in cars in the last 3 decades, and the same is true when it comes to the technology in underwater strobes in the last decade. Purely a subjective impression, but it seems the Subtronic designs are getting a little long in the tooth.

Let's be clear: The Marelux Apollo 3s are fully aluminium construction. And the Backscatter HF-2s use aluminum for the flash head and heat sync, and plastic for the body to reduce weight. This is good engineering -- there's nothing inherently inferior with good quality plastics for this application. I mean, even Seacam uses plastic instead of aluminum for its port extensions to reduce weight with no loss of quality or durability. Similarly, while the Ikelite DS230s are a plastic built, I've never heard any complaints about durability or reliability as a result. Selective use of plastics to reduce weight (and cost) is a feature, not a bug. Please don't make misrepresentations about easily-verifiable facts: Ikelite DS230s are $1295 Marelux Apollo 3s are $1199 Backscatter HF-2s are $899

99% of the time (100% of the time in wide angle scenarios) you're shooting in full power in HSS mode anyway because HSS mode inherently puts out less light. Hyperbole. Sure, it's not a completely useless feature, but if there's water in the battery compartment, odds are you've already lost the batteries, moisture alarm or not. All of the strobes we've been discussing have isolated battery packs/battery compartments, so even without the moisture detection, you're not compromising the integrity of the strobe itself if you continue the dive. This falls into the category of 'over-engineered' in my book, increasing the price for no functional advantage. Theoretically beneficial, if you happen to have an issue that can be solved by a firmware update. Do you have actual examples Retra solving issues through firmware? Or other manufacturers having issues that could've been addressed by firmware that weren't because there was no ability for the user to upgrade the firmware? Backscatter HF-2 offers a wider range of diffusers and light modifiers. They will also offer an optical snoot specially designed for the HF-2, just like Retra. And of course, Retra's optical snoot is compatible with other strobes, so that's not an argument for buying the Retras. About the only unique accessory is the reflector, and that's only needed because of the lower power output. Other strobes like the Backscatter HF-2 achieve the same result (at higher power) simply by removing the diffuser. Customer support is a plus, to be sure, but even here I wouldn't say Retra is alone in this category. From every report I've seen, Backscatter and Ikelite are also very responsive when it comes to customer support. I assume Seacam is the same. I think the differences are critical even if you're not on a budget. As said -- I could afford any of these strobes. But what's Retra bringing to the table that other manufacturers don't, even if we assumed the price was equal? The user interface is great. Agreed. But Backscatter, Ikelite, Marelux, Seacam and OneUW are 90% of the way there too on user interface. Light quality -- on par (or slightly worse) than the Seacam, OneUW and Ikelite. Wider and softer beam by default than the Marelux and Backscatter HF-1s, but both those are 1-1/2 stop brighter. When you add the Backscatter diffusers into the picture, you get similar beam coverage at similar temperatures and still higher power. "And more" -- which more? "Differences are clear and significant" - how? Ikelite strobes work just as well with all the same features with other manufacturer's housings if you use the Ikelite TTL converters (which are reasonably priced and no more expensive than installing a 3rd-party optical flash trigger). Plus, with the electrical sync, you get more accurate TTL than Retra's optical sync implementation. And they work just fine in (manual mode) with fiberoptic connection if you get the $150 optical sensor. Plus, Ikelite gets you the option of off-camera use with an optical sensor connected to the strobe via electrical sync cable, all at quite reasonable prices. This makes them the best strobe in my view for placing on the back of a model's tanks and triggering reliably, especially combined with the highest overall power output at 5000k. The Retras? They offer no option for remote triggering, so you can't even use them off-camera reliably. Price is not my primary concern. Features are. And for the reasons I've explained above, the Retras fall short of other newer strobes here. I would agree.. perhaps a mod could split this exchange into a separate post? From my perspective, while price factors into it, the Retras fall short even if price is irrelevant. I also think there's room to expand further on the feature comparison we've started. Why cut the discussion short? Especially if we split it off into a different thread? More information is always better then less when making purchasing decisions -- at least, that's my preference 😄

Which detailed comparison are you referencing here, Jerry? The only credible comparison testing I've seen is from Backscatter, and it doesn't back up the "clear differences in quality and features" you're claiming. The Retras are well designed and well built, no doubt, but what features do they have that the Marelux Apollo 3s or Backscatter HF-1s don't? Battery capacity is no better, power output is between 1.5 and 1 stop less, recycling times are worse on the Retras, all have HSS and TTL. The HF-1s have more options in terms of diffusers, a credible video light built in, etc. The Marelux Apollo 3s have impressive remote-triggering capabilities and claimed consistent exposure between repeated shots. Beam quality and color temperature may be better on the Retras, but at the cost of reduced power output. And even on that metric, the Ikelite DS230s do better at 65% the price. Truth is, even money being no object, I'm not sure I would pick or recommend the Retras today over some of the other choices out there. I sold my Retra Pro Xs, and briefly considered getting a pair of the Retra Pro Max to replace them when the power Vault was announced. Then noticed the size and the minimal improvements to recycling times. Personally.. I just don't see enough pluses here to make this an end-game strobe. Are these really the best tool though? Sure, coming from a mediocre strobe like the Seafrogs SF-01 they offer a very real and noticeable improvement. But there's plenty of other contenders for the 'best strobe' crown these days.

Regarding the WWL-C performance, I too was a bit surprised that it was this bad. I've owned the WACP-1 before, and even with the (significantly older) EF 28-70 lens, the results were pretty good. So I'm not sure what's going on here -- it could be the WWL-C itself, but I suspect the biggest issue is the quality of the Canon RF 24-50 F3.5-F6.3 lens. Still, while the lens is comparatively worse, it doesn't mean it's incapable taking good images in the field. Here's an example that I find perfectly adequate -- after some editing 🙂 I too would love for manufacturers like Nauticam to actually test (at least their corrective optics). Getting them to test various lenses in different ports and post those results is probably never going to happen.

I'd love to, but don't have one. It should perform marginally better than the WWL-C (on par with the WWL-1 according to Interceptor 121), but I wouldn't expect night-and-day improvements. I'm more curious if the WACP-1 or WACP-2 really show a benefit from the larger glass elements and different optical formula (when it comes to the WACP-2). But, alas.. I sold my WACP-1. So unless someone wants to lend me one of these lenses.... The other factor to consider here is the 'taking' lens behind the wet optic. My tests are with the Canon RF 24-50 F4.5-F6.3 lens, which is a kit lens, and nothing to write home about in terms of optical quality. I would expect much better results with a proper modern lens like the Sony GM/G lines or perhaps Canon's RF14-35/15-35L lenses behind the WACP-2. Even the Sony 28-60 kit lens is pretty well reviewed.

I think the more 'on par' strobe from the Subtronic line is the Pro270. But this is definitely a big strobe, priced at $1350 (without VAT), and with dimensions to match -- 1200g, 90g negative, 110mm diameter by 180mm length. GN rated at 22, which is a stop brighter than the 160s, but pretty inefficient if it takes 270w to get that output. And that's all with an external battery pack, so extra weight and cost there. The 3AH external battery arm is $219 without VAT and weighs. It's only 21Wh, weighs 310g (-80g negative), and with such a high-powered strobe, that's only going to last you a dive or two. They do offer 9AH (64Wh) battery packs that seem to connect to the strobe via cable, but those are $552 without VAT and probably weigh a ton. So.. overall, Subtronic has an interesting modular design concept, but at the end of the day, nothing about the specs or the pricing particularly stands out from the pack.

Interesting Atus -- size and price wise, I always assumed that the Subtronic 160s were very similar to the Seacam 160Ds. The published dimensions, 70mm x 180mm make the length almost identical to the Seacams, but slightly narrower. 740g weight is great (I guess they left out the battery weight in the arm), but the -190g negative boyancy is.. bad. The power sounds like the real issue though. I haven't tested the Retras in my comparison, but Backscatter has them rated at GN22. If the Subtronic 160s are a half stop less bright, that's pretty unimpressive. It put them in the same camp as the Inon S-220s, and 1 1/2 stops less bright than the Sea & Sea YS-D3s that are smaller, lighter (especially when you account for battery weight in the arm), and almost neutral in the water. So.. they're ok for the price, but don't really compete in the same league as the Ikelite DS230, Sea & Sea YS-D3, Marelux Apollo 3 or Backscatter HF-1s, regardless of the 160Ws power output. (While I agree that manufacturer's GN ratings are all over the place, the Ws power rating also doesn't tell you much and isn't directly comparable. One 160Ws strobe can be up to a stop weaker than another 160Ws strobe depending on how efficiently it's implemented, reflectors, beam angle, color temperature, etc.. There's no substitute for comparative testing using a consistent methodology)

I would certainly consider them. Seems U.S. distribution is a bit lacking though, so probably easier to source in the E.U. than North America.

Interesting, Chris. I didn't realize they would be different in the same port size (n120). Anyway, my 58.8mm measurement is for the Nauticam Canon RF housings.

Good investigative work and good summary, Ben. I got the CTO and minus green filters in various strengths -- just finding the time and energy to test them is proving challenging 🙂

Trying to gather the distance from the camera lens mount to the front of the camera housings where different extension rings attach. This is for the purposes of calculating the right extension length for various lenses in different manufacturer's housings. I'll kick things off with the Nauticam N120 housings, which I've measured at 58.8mm (let's round to 60mm). If you have one of these housings, could you measure the distance with a ruler please and contribute here? Nauticam N120 - 60mm Nauticam N100 - 26mm? Marelux - 43mm? Seacam - 40mm? Sea & Sea - ? Aquatica - ? Isotta - ? Ikelite - ? End result will be a spreadsheet like this that I will share here for future reference:

Ok, so I just measured the distance from the Canon RF lens mount to the front of the housing on the R5C Nauticam housing (N120). It's 58.8mm. Accounting for measuring error and manufacturing tolerences, let's say 60mm. This should put the same distance on the N100 Sony housings at around 25mm. Could someone confirm? Also would be curious to get this distance measured on Marelux and Seacam housings. I've updated my chart accordingly. As you can see, the Nauticam recommended extensions vary quite a bit in some cases from the calculated optimal positioning of the lens based on the Optical Bench entry pupil. Maybe that's to prevent vignetting? Or did I mess up how I calculate the optimal extension (=[@[I-P-FD (MM)]]-[@[Nauticam Camera Lens Flange to Front of Housing Distance (MM)]]. Not quite sure.

Cool, I didn't know about the Sony 16-25 F/2.8 G! That looks like a great lens for underwater rectilinear use, and cheaper too! The matching Sony 24-50 F/2.8G also looks very promising for use with the Nauticam WWL-C and dry water contact optics. Unfortunately, none of this is helping my gear acquisition itch... 😄 Image quality differences vs. an adapted Canon 8-15 are probably minor, but I guess there's still a size and weight benefit. Also, since the conversion makes the RS 13 behave like a a native Sony lens, you may be able to unlock the faster 30fps shooting mode with something like the A1 or A9III. Minor advantages in the grand scheme of things, but still nice to haves. Personally, fisheye is by far my preferred choice for wide angle. Thanks! Didn't know about the custom SAGADIVE extension rings either. Looks like they make a custom 10mm and 25mm extension ring for N120 that's cheaper than the nauticam version (and doesn't come with the 25% China tariff you get slapped with if importing things from Europe). I didn't see any in-between sizes like 12, 13 or 15mm listed on the site. SAGADIVE also makes an adapter to be able to use Nauticam's WACP-1 with other manufacturer's housings (like Seacam) which is great. https://sagadive.com/en/product/aros-adaptadores-saga/ Yes, thank you very much for the idea, Adventurer!

Apologies, I should've read your original post a bit more closely. Yes, you are still saving 600 grams with a pair of Retras compared to the other large strobes, which is not insubstantial. And I do think it's a fair point that you separate the Vault from the strobe for travel, making them a bit easier to pack than, say, the Seacams. But really, with the Vault (and other accessories), and with the price hike on the latest version of the strobe, the Retras are reaching stratified price territory now. $2000 (or $2100) per strobe. Gone are the days where they were selling near $1000/piece, a modest price premium over the Inon D330s and Sea & Sea YS-D2s of the world. And $500 for a battery pack replacement is also stratified territory. Only the Seacams are more expensive at $2500, and their replacement battery packs are cheaper at $385. Other large strobes like the Supe D-Pro ($749 - $118 battery pack) Backscatter HF-1 ($900 - $50 batteries) Marelux Apollo 3 ($1199 - $25 batteries), Ikelite D230 ($1299 - $250 battery pack) and even the OneUW 160Ds ($1650 - $180 battery pack) start to look like much better value!

Hello Landvogt! Thanks for the kind words. Unfortunately, I don't have a RF 15-35 F2.8 L lens to test (unless someone wants to lend me one :D). But as for the RF10-20 with the 140mm dome (dome shade removed), the results were a little disappointing, especially in the corners. That lens really does benefit from a larger dome. Here is the 10-20 RF at 10mm, F13, ISO 100. 427mm dome on the left, 140mm dome on the right. The full image shows that the 20mm extension + 427mm dome puts the lens' entry pupil closer to the dome's center of curvature with than using the same 20mm extension + 140mm dome. So probably a 25mm extension would be more optimal with the 140mm dome. And here are center and corner crops, again, 427mm dome on the left, 140mm dome on the right. Center sharpness and contrast degrades only a little, and that's likely caused by shooting through more water with the smaller dome to keep same subject distance and framing. But the corner resolution really suffers. I think this loss in corner resolution may have to do with the MFD of the RF10-20L being 250mm. I say this because the Laowa 10mm prime has a much shorter 120mm MFD and doesn't exhibit the same degradation in the corners. If you compare the two 10mm options in the larger dome, there's not much difference between them. But with the smaller dome, the difference is quite obvious in the corners (and minimal in the center). The Laowa 10mm prime is a better option to use with the 140mm dome because of its quite shot 120mm MFD.