Adventurer

Yes, indeed - glad you mention it, Matthew. However we all rely on personal impression reports like yours and Alex‘s. Unfortunately there has been no quantified lab test with this lens which measures (underwater) in lp/mm. So we do not know how much we are potentially missing out 😅. I do believe you guys, though! To give everyone a good, relatable reference: the often-discussed Canon RF 100mm f/2.8L Macro manages to reach up to 86.5 lp/mm at f/4 in the image center. (source: digitalkamera.de lab tests). So unless you use focus stacking it‘s not very realistic to archive under practical underwater application. @F16 it bends down to 61,8 lp/mm in the center; and with F22 it’s down to 49,5 lp/mm. So due to macro practical depth of field requirements you might have experienced that lens just similar sharp or even less sharp than your EF8-15. I recall that @MatthewSullivan was praising the RF100 macro for its sharpness in the underwater photography show on YT and also happens to shoot and own the adapted RS13 fisheye ( „the holy grail“ ). So having the numbers rankings, he could maybe make a well informed expert guess on the RS13‘s lp/mm sharpness value? RS13 adapted = ???? lp/mm RF100 @ F4 = 86,5 lp/mm EF 8-15 Fisheye = 54 lp/mm RF 24-50 @ 24mm + F11 = center 52,8 lp/mm edges 41,2 lp/mm @Muellema to answer your question: all lenses that can be adapted / used with full frame mirrorless; or better: that make sense of being used to max out IQ on your full frame mirrorless system. Sharp RAW output is measurable in lp/mm or lw/ph (resolution).

Hi Tim, I hope we do not drift away from my initial aim with this post. I think I pretty much highlighted the practicability part above and can tell you (by experience) that the Tokina 10-17 pitched a great concept but is IQ wise totally inferior to the Canon EF 8-15 F4 L - for the sake of trying to nail the cream of the crop here, I would also appreciate if we can stick to FULL FRAME MIRRORLESS systems and leave APS-C, M43 and compact out of the topic.

I’d like to throw out a structured thought experiment and get input from others who are chasing maximum optical quality underwater. The idea is a bottleneck search: identifying which part of the optical chain ultimately caps achievable sharpness, and how modern lenses may have shifted that ceiling. If we ignore water quality for a moment, I think underwater image quality can largely be reduced to three primary, controllable factors: Camera & Sensor Pixel pitch and diffraction limits define the aperture range where the sensor can still resolve real detail. Higher-resolution sensors tend to hit diffraction earlier, which already caps usable sharpness. The Lens (Topside Performance) Every lens has a measurable resolution ceiling, typically expressed in line pairs per millimeter (lp/mm) under controlled lab conditions. This is the absolute upper bound of what the system can ever deliver. Dome Port or Underwater Corrective Optic (WACP, FCP, etc.) These elements can preserve or destroy resolution, but they cannot exceed the lens’s native resolving power. They are enablers—not multipliers. My working assumption is therefore: No underwater optic or dome can ever push image quality beyond what the lens–sensor combination can already resolve topside. For anyone interested in comparing topside lens performance in a more objective way, I’ve found two resources particularly helpful. The ISO 12233 sample crop tool at https://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1624 allows direct visual comparison of resolving power across lenses and sensors, while https://opticallimits.com/the-list/ provides a concise overview of laboratory-measured resolution data across many modern and legacy lenses. A Reference Point: Canon EF 8–15mm Fisheye In underwater photography circles, the Canon EF 8–15mm f/4L Fisheye has long been regarded as one of the sharpest and most reliable underwater lenses ever made. That reputation is not anecdotal—it is backed by lab data. From LensTip’s resolution test (more than a decade old): “The performance you can see on the graph can be only described by one word: revelation. At shorter focal lengths the lens, even wide open, reaches a level of 50 lp/mm or higher and by f/5.6 it gets to record-breaking values of 53–54 lp/mm.” ( source https://www.lenstip.com/311.4-Lens_review-Canon_EF_8-15_mm_f_4_L_Fisheye_USM_Image_resolution.htm ) At the time, this effectively outperformed almost every other EF lens tested. In underwater use, the lens also benefits from extremely close focusing, which reduces water column and often compensates for other optical weaknesses. This is arguably a fourth, indirect factor: minimizing the amount of water between lens and subject. The Shift with Modern RF Lenses Here is where things get interesting. If we look at modern Canon RF lenses, even non-L designs now meet or exceed resolution levels that were once considered exceptional. For example, laboratory testing from digitalkamera.de reports the following for a very modest kit zoom: Canon RF 24–50mm F4.5–6.3 IS STM (tested on a 24 MP EOS R8): “The lens reaches a maximum resolution of 57 line pairs per millimeter (lp/mm) in the image center and 49 lp/mm at the image edge at a focal length of 35 mm.” In other words: A small, inexpensive, non-L RF zoom already exceeds the peak resolution of the legendary EF 8–15mm fisheye, at least in topside lab conditions. This strongly suggests that modern mirrorless lens design has raised the baseline for optical sharpness, and that many assumptions carried over from the EF era may no longer hold. The Exception—and the Real Question The EF 8–15mm remains special not just because of resolution, but because it combines: Very high lp/mm performance Extreme close-focus capability Excellent compatibility with small domes Reduced water column in real underwater scenarios That combination makes it a rare exception where practical underwater sharpness can rival or exceed newer lenses that are sharper on paper but harder to deploy underwater. This leads me to the real questions I’d like to discuss: What is the sharpest lens (in lp/mm terms) available today for your system—Canon RF, Canon EF, Nikon Z, Sony E? Which of these “topside gold nuggets” can realistically be used underwater with domes or corrective optics like WACP/FCP? Are we still overvaluing classic underwater lenses, while underestimating what modern mirrorless optics could deliver if paired with the right underwater solutions? I’m very curious to hear which lenses you think currently define the true optical ceiling for underwater photography in your system—and whether anyone has successfully translated that topside sharpness into real underwater results.

Exactly my experience; this is why I do not like float belts. Two -650g INON Mega Float Arm M is my base configuration for the Backscatter HF-1. I combine them with stick arms each to be able to fold them in nicely in 45 degrees left and right. This will usually give you your base trim. A third float on a ball in the middle if needed. I recommend to test all in a bathtub at home before embarking on a trip.

These INON Float Arms serve me for several years now: https://www.hydronalin.eu/inon-mega-float-arm-s-mit-390-gramm-auftrieb_2058 They come in various shapes. Very lightweight, durable and have two M5 threads on which you can connect accessories such as LensHolders, Actioncams etc.

I am happy we got introduced to this approach again in underwater optical design. Putting together the (distorted) sample images by Don Silcock, Alex Mustard‘s Infos on his 20mm and Zeiss Version plus my own experience with such a corrector port design I would conclude the following. The strength of theses systems lies in hosting / correcting lenses above 20mm focal length on full frame. If you go wider the distortion starts to look odd and you may also suffer corner sharpness IQ loss. The strength of theses system group lies in being able to correct high quality lenses with large front glass elements and offering a very flexible uw corrected zoom range at small size and weight factor. I think it was a sad marketing mistake that Seacam let the test pilot go to shoot with a 16-35mm focal length. The real sweet application will be lenses in the 20-60mm zoom range (Panasonic FullFrame L Mount has one) and in the 20-70mm focal length range. In reality these will be up2date 24-70s or 28-70s with major camera brands. Therefore it would be beneficial if Seacam and other manufacturers would not design the System fully afocal and give it a slightly widening punch factor of 0.8x or 0.75x I hope to see this in the market and some nicer test shots with such an Ivanoff revival in 2026. As the technology had been patented in the past it is now public domain and all camera housing manufacturers could enter this product segment with high end underwater optical designs without risking IP infringements.

Yes,... that's something different: Canon/Nikon/Sony-Lens + WetLens on Land with slight vignette will in most cases dissapear when dipped in water. Canon/Nikon/Sony-Lens pure on Land with sensor vignetted RAW will not.

The test image ist actually dry and without a water contact conversion optic. I did not shoot it. It's from a public review. These exist in various forms on the net. But I have my own RAW files shooting a white wall. This "dry" and dismal projection of lenses cannot be fixed by water or water contact optics, as far as my testing confirms. I assume it has very much to do with the last projection array of glas inside a dry lens. Water contact optics or domes working in front of the optical system cannot cancel these out. Can somebody else confirm that? It would make me feel more comfortable with my analysis and thoughts on this matter. Having said that, I think a very much workable way is to shoot these wide vignetters at a focal length that is bearable. With my RF 24-105 STM for example the whole thing is very usable @ 28mm onwards. But as the 24-105 STM has a much larger front glas element and extends during zooming it is a more suitable candidate for dome ports and my Ivanoff style underwater correction port.

Our very own @DreiFish took the efforts to compare and test this in a formidable thread that deserves to be pinned:

Sorry Phil, but that is wrong. Nauticam lists WWL-1C combination with Canon RF 24-50mm STM in their port chart: https://drive.google.com/file/d/17vlICB0Gn6bbeTGaIR9yd3HHOIfIG9kK/view

Sorry for maybe not being explicit enough about this in my thread opener: the Canon 24-50 STM is intended to be used with underwater corrective optics, which will turn it into approx 130-70 degree FOV being equivalent to your 10mm with the RF10-20. By the way, you highly expensive RF 10-20 suffers from a similar flaw at even higher level: With disabled distortion- and vignetting compensation, the image corners are black at 10mm. https://opticallimits.com/canon/canon-rf/canon-rf-10-20mm-f-4-l-is-stm-review/

I’ve been examining the Canon RF 24-50mm STM lens on full-frame bodies and noticed something important: this lens, often recommended by housing manufacturers, does not actually project image corners onto the sensor at 24mm and not even fully at 28mm in uncorrected RAW. In other words, the much-discussed corner sharpness that underwater photographers focus on isn’t even present at those wide ends, because the image simply doesn’t cover the full sensor corners natively. Even a fancy underwater correction optic such as the Nauticam WWL-1 WACP FCP or Marelux Aquista 110 or 130 or cannot fix this. The corners of the frame are just not recorded and a pure digital fantasy mashup of reality. This improves slightly at 28mm and is gone at 35mm. However, there are reasons why this lens is still a favorite for underwater setups with water-contact corrective optics. Let me summarize the key points: • Compact and Lightweight: It’s extremely small and light, making it easy to handle in underwater housings. • Small Front Glass Element: It’s one of only a few Canon RF lenses with a very small front glass element (just 37 mm), which makes it suitable for water-contact optics. • Retracting Design: At 24mm, the lens is fully extended, and as you zoom to 50mm, it retracts inward. This makes it physically convenient for flat port designs and is a unique trait among Canon RF wide-angle zooms. In essence, while the lens doesn’t project full image corners at the widest focal lengths in uncorrected RAW, the practical benefits—compactness, compatibility with corrective optics, and convenient physical behavior—explain why it’s still a favored choice in the underwater photography community. Is it to you? I bought the lens a few month ago and also got a Marelux Zoom Gear for it, but ever since sinking it in a bathtub it is giving me a lot of headaches. This is why I called it „the shard“ in another forum thread here. I hope somebody can change my mind and give some value to this piece of glas. If you’re looking to have a flexible wide-angle zoom that you can combine with underwater contact optics or teleconverters, here’s a quick comparison of the zoom factors for some of these solutions: Canon RF 24-50mm STM (without limiter): 2.08× Canon RF 24-50mm STM (with 28mm limiter): 1.79× Canon EF 8-15mm Fisheye with 2.0× Teleconverter: 1.88× So, these are some theoretical findings and empirically validated facts. I’d be interested in reading your practical experiences and thoughts on the Canon RF 24-50mm STM lens. If you’ve found better alternatives or reasons why this lens stands out as the ultimate wide-angle solution for you, please share your images and thoughts !

Great moderation remark Davide! ❤️‍🔥 I would like to add a thought, roundup for everyone’s consideration: OsmoAction and Insta360 Action have introduced newer models and in 2025 no GoPro 14 HERO Black was introduced. Generally the ActionCam space seems to have matured and 3 competitors seem to take the segment with different angles of attack. Insta360 did not introduce an AcePro3 and instead was fostering the mini project GO and GO3S. GoPro while falling behind was the last to offer HDMI output via their media mod, which could have been important for external underwater monitors. Having said the above: the main weakpoint in this product segment actioncams for divers is the very tiny LCD these small cameras offer. On the other hand their main core advantage is beeing tiny. With the advent of ultimate smooth image stabilization in these cameras is sticking them into spaces where large cameras cannot go. So that takes you to re-considering macro shooting in actioncams which is a little bit like shooting macro on a Nikonos V these days. INON has introduced quite a variety of macro lenses for all the GoPros, Instas and DJI Osmos and I am strongly considering to try these. I used to be very convinced to put the action cam on a camera tray but this is not my goto idea for the year 2026. I plan to put it on a stick and basically get a cheap Nauticam EMWL with it. Instead of moving a large mirrorless rig with an $$$$ lens around, why not move the tiny lens including camera around and see what it will catch. Just an idea to move your action cam footage to a new level… instead of looking onto an external monitor, look over the camera onto two distance sticks 🤔😏 - let’s see how this turns out.

Yes, and from the information I was given that exact adapter would also pair with Aquista 110 (production series, not prototype) and vice versa. It would be nice if someone could confirm this.

Yes, I totally agree to that Davide. This should be the main purpose of 3rd party action camera housings. ..as well as giving access to magnified screen ( via HDMI or USB-C ) option. However... with the GoPro HERO 13 being the last ActionCam to offer an HDMI-Out and no HERO14 introduced in 2025 the future for buying an external monitor and moving this onto the next action cam looks dim. For Cameras like the Osmo Action 6 or Insta Ace Pro 2 you need to grab the screen signal via USB-C (Webcam Mode).

Hey everyone, I wanted to share a perspective I’ve often recommended to fellow underwater photographers when it comes to shooting blue water sharks, especially when you’re working with natural light and strobe combinations. One of the key points is that most shark species have a pretty neutral, silvery-grey coloration. In other words, you’re not trying to bring out a riot of colors like you would with a coral reef and fisheyes lens. That means you don’t have to worry as much about maintaining warm color fidelity at longer distances. In fact, if you have good visibility, you can shoot from over a meter or more away without losing too much detail. And when it comes to lighting, the idea of a cooler color temperature strobe can actually be a real advantage. Cooler strobes will penetrate the water more effectively over distance because the red wavelengths get absorbed quickly anyway. So you’re focusing on sharpness and light energy rather than trying to preserve warm tones that aren’t really there. In practical terms, using a strobe that’s a bit cooler and then adding a warming diffuser only if needed is a flexible approach. For typical shark photography—like shooting reef sharks in the Red Sea, where they don’t come extremely close—keeping your strobe on the cooler side and not worrying about warming accessories can give you the best reach and clarity. And one more thing I’d like to add is about your lens choice. If you’re used to working with a really wide lens like a 15 to 30mm, you might find yourself falling a bit short when the sharks stay a little further away—like in the Maldives or the Red Sea where you’re not always going to get them right up in your face. In those cases, I really recommend something with a bit more focal range—like a 28 to 70mm or even a 24 to 105mm. That way, you’ve got the flexibility to handle those sharks that come in nice and close, but also the ones that hang back—like hammerheads or thresher sharks. Hope that helps round things out! So that’s the gist of it. Hope this helps some of you thinking about how to set up for your next shark shoot.

Sorry for the mess. I should not give precision optical advice late in the evening without my glasses on! I simply overlooked the III behind puttsk‘s lens. But about the other remark by Phil: I got the info from a friend that at least WWL-1 and Aquista110 production units have similar bayonet and can be swapped. I think he even got the info from a Marelux employee. Can you please double check + confirm or deny this, Phil?

Actually I also had a long period, where I thought, I might be missing out on something, not owning a WAPC-C or other Nauticam Water Contact Optic. They are just so heavily hyped and raved by various (officially not paid) talking heads on the internet. The death sentence for WAPC-C was this very honest review by Interceptor121 : Interceptor121 Photography & Video WorkshopsNauticam WACP-C vs WWL-1I am conscious that a post like this is destined to create some stir, however it reflects over one month of testing of the two Nauticam water contact optics with my A1 and summarizes my conclusion …

Then you least cost route would be buying the WWL-1B + Aquista Mount: 55803 and the Macro Port 97 31302 ..both on stock with a dealer near you. Sorry, I did not see that you are from Thailand and thought you were Czech. 🤦‍♂️😅 I have also looked into Aquista 110 there and asked a ton of questions about it. The mount is identical to WWL-1 requirements and you should be able to plug your WWL-1B into the front. I am quite curious how this old lens will perform behind Aquista 110 or WWL-1B. Please report back with impressions and results if you will go that road.

..and that should have brought you to the conclusion not to use WWL on Canon Naughtycam Systems and put a 3rd party dome on your shopping list. Please report back WASO once you have some shots with what you bought.

Found my instructional post with sample images on how to conduct the final test:

Dear Chris, the database diagrams work great to get you as close as possible, down to millimeter results. It‘s worth exploring this and to move away from 5mm steps in extension rings that most manufacturers offer. The main problem is the dome manufacturers limited or wrong radius and glas thickness data which distorts or ruins the theoretical dome position. I measured a few domes (I bought used and sold again) to come to that finding. Once I applied the optical bench hub data and formulas to these values I pretty much nailed it. I was able to substantially improve IQ by working on 1mm tolerance. After computing the mm you have to do the reality check with a split shot test to confirm your theoretical approach. I described this in a forum post. I do not seem to find it but think the post was done approx 1.5 yrs ago.

Well, I am not sure if I can encourage you to take that path for 3 reasons: 1st You should check, verify if the Nauticam small dome allows you to detach the lens hood underwater. Otherwise you will be unable to shoot 8mm pictures. 2nd I have shot the Marelux 140mm FE Dome, which is rumored to be very identical to the above with the exception of having that removable sunshade feature and a special optical coating which is supposed make water drip off the dome front really fast with splitshots (I can confirm that coating actually has an effect). 3rd while you could think that the Marelux and Nauticam small domes are a full half sphere, they are actually not (if identical). A small part before reaching half sphere is missing plus it is covered by approx half cm tunnel, due to the frame the dome glas is mounted on. Issue number 3 results in the dome having to be slightly mispositioned and that you will be unable to nail the entrance pupil in the dome center. I have the assumption that I could squeeze out even a bit more corner sharpness on the 8-15mm if I am able to fix this. I am currently for the above reason considering getting a third party small optical glas coated fisheye dome from Hydronalin with also mm exact positioning. It will be smaller and more affordable but should increase IQ even further as luckily the Canon 8-15mm requires a dome radius of no more than 4.1 - 3.8 cm (depending on the zoom position). The smaller dome should improve the needed DOF for the field curvature of the virtual image. I'll let you know my results in the new year, I guess.

This reads a little ignorant of the facts and giving yourself away to fatalism and Blackbox statements… (claimed by some uw manufacturers and uw ambassadors). It‘s true that working yourself towards a premium underwater optical solution cannot be done by following only land based tests and lens criteria. But you have to start to work your way down towards the best lenses somehow. This was my point when giving you some directions. A flawed lens rarely can be cured by an underwater contact optic and it is no rocket science to understand the details that matter to get good results. As you are around for a while in this, I am confident you will critically and prudently search for an optimum. In fact I‘d like to read your personal findings in that journey here soon, as we are not too many fellow RF Canon shooters. My point was that (even land based) public sharpness tests for lenses are surprisingly scarce in the net and unfortunately there seems to be no source that has prudently measured RF and EF lenses under the same lab conditions. Furthermore Camera sensors and measuring techniques have evolved and not all lens test have been done on an R5 body. That means you have to pull together various sources and take everything with a grain of salt to get a clear picture and vague scale on what’s possible and how things behave when you are obsessed about uw sharpness in general and corner sharpness. Then take the interesting lens candidates and have a look where the entrance pupil is located and what their minimum focus distance (MFD) is. This is beneficial for domes as well as WACP, Aquista, WWL & Co. You will be able to boil it down to a surprisingly short list for the Canon RF System. Some of the very good candidates do not even appear in the manufacturers port charts. If you get a glas dome instead of your acrylic dome will have no real optical gain. The only difference for Glas domes is that they are more resilient to micro scratches and will last much longer. Glas domes have to be taken into the optical equation while most acrylic will become invisible underwater. I shoot a glass dome though.

Sorry, I still don‘t get which lenses you now actively own and shoot 🥴 - Do you already have the RF14-35mm ? If you are in search of highest IQ you need to start of with researching the lpmm performance of Canon lenses topside tests. They can be found on test sites such as lenstips.com digitalkamera.de or photozone.de etc Logically any lens combined with a perfectly sized and positioned dome or water contact optic ( such as the WACP, WWL, FCP etc ) cannot perform above their land design. It‘s at least very unlikely, I suppose. So starting of with that bottleneck factor makes sense. On lenstip you will find the following interesting statement about the Canon 8-15mm F4 L fisheye zoom: Which at that time of the review was record breaking 😉 - when you compare this with values reached by RF lenses today, even the basic kit lenses range above 50 lpmm in the interesting wide angle space. Your just cancelled order RF24-50 does have 56 lpmm / 49,2 lpmm (12 % falloff) in center/corner @ F5.6 30mm zoom. So generally preferable would be to host RF lenses over EF Adapted lenses in most cases. Also friends and users not owning a high megapixel Canon mirrorless might perceive optical performance as great and will not be able pixelpeep as intensively as you if they are still on a 5D Mark IV etc. In the Canon System the highest performer from the underwater lineup lenses is the ‎   Canon RF 100 mm F2.8 L Macro IS USM with 86,5 lp/mm @F4 according to digitalkamera lab test, to give you a rough reference on what is possible. About the dome I suggest you cross consult with Andi at Hydronalin Germany.