5 hours ago, Chris Ross said:

There are a number of constraints when using lenses behind water contact optics, there is an entrance pupil constraint and there are also issues with zoom lenses that change length as they zoom

I looked into using the z24/1.8 with the wwl-c a while ago and this was the issue. Front element cause vignetting.

Edited April 17Apr 17 by Christian K

3 minutes ago, Christian K said:

I looked into using the z24/1.8 with the wwl-c a while ago and this was the issue. Front element cause vignetting.

Yes, it's unclear exactly what sets this and it varies between the WWL and WACP models as to which lenses they work with. I would guess that port charts for these optics are fairly complete and to get a better optic use the chart to help, but probably involves going to a WACP. I would think that the main limitation with some of these bigger lenses is the flat port size (port ID or the m67 port diameter causing vignetting), or some of the small primes a short enough port to properly accommodate them.

9 hours ago, Chris Ross said:

The other advantage of the wet optics is that shooting at f5.6-8 is possible where the corners would be pretty mushy on a rectilinear behind a dome.

Very good points, Chris. Put differently, it is a bit like working with an upscaled image that is almost APS-C in size. Because you are using only the center of the optical system, the “corners” improve — although they are not really true corners anymore — much as they would if the photographer had simply cropped from the center of the image.

So if one wanted to frame it positively, the credit for the improved corners and the straighter rendering arguably goes more to the air lens and its lens corrections than to the water-contact correction optic. 😉

The obvious downside, of course, is this: why take an expensive and bulky full-frame system underwater if you could achieve similar image quality with a more affordable and compact APS-C setup?

Looking at the WACP - calculations show that this is closest to a stereographic projection fisheye,

Interesting - where did you find that? I’d really like to dig into those calculations.

Edited April 17Apr 17 by Adventurer

7 hours ago, Chris Ross said:

Yes, it's unclear exactly what sets this and it varies between the WWL and WACP models as to which lenses they work with. I would guess that port charts for these optics are fairly complete and to get a better optic use the chart to help, but probably involves going to a WACP. I would think that the main limitation with some of these bigger lenses is the flat port size (port ID or the m67 port diameter causing vignetting), or some of the small primes a short enough port to properly accommodate them.

Yeah, I’m not sure the WACP route will yield any gains that are really worth it for me compared to the WWL. Maybe if I start shooting at home in the Baltic Sea regularly… that does not involve flights.

As an owner of a WACP-1, WACP-C, WWL-1B, and Canon 8-15, here is my objective, real-world experience with all. I use the inexpensive Sony 28-60 in all cases except the 8-15 for ultra-wide scenes.

Note 1 - One of the greatest strengths of all the wet optics is the inclusion of a real zoom option.

Note 2 - All water contact optics have a slight degree of barrel distortion at the wide end. Scenes such as pier legs or wreck interiors are best when zoomed in a bit to help compensate, or correct slightly in post. This is not, however, noticeable in normal reef scenes even at the widest FoV.

WACP-1: Dry Port - no water layer between the lens and external dome.

- Large on the surface with a weight of 10lbs dry

- Best image quality of the three, but not overly noticeable unless comparing side by side with others

- Very stable in-water due to size; beneficial for slower shutter or video work

WACP-C: Dry port

- Smaller version of the WACP-1 weighing only 5lbs dry, or half as much

- Not quite as sharp, but only noticeable if compared at high zoom in image review side by side with the same from a WACP-1

- Substantially lower price in comparison

WWL-1B: Wet Mount Port - layer of water between the flat port and the attached WWL.

- By far the smallest and lightest of the 3

- Very similar image quality to the WACP-C.

- My go-to choice for travel when size/weight are issues

- The lowest overall cost

- Must “burp” lens after entry to make sure no air bubbles are trapped between port and wet lens

- *WWL-C is same concept except designed for 24mm lenses vs 28mm

Canon 8-15 w traditional hemispherical dome

- Go-to fisheye option for exceptional quality

- Ultra-wide 180 FoV vs 130 degree max

- No real zoom ability

- Easily used with a 1.4x teleconverter for greater reach with no noticeable image degradation

Does the addition of a water-contact optics improve the quality of a standard kit lens?

In my actual use and real-world comparisons…yes.

I find the corners to be sharper at a wider aperture. This provides great flexibility when lower light becomes an issue

Is this better than a traditional lens and dome? That’s really personal taste, very similar to how much salt to add to food. “Better image quality” is open to interpretation. With regards to overall user experience, I personally feel there are greater options to capture a moment, especially in fast-action scenes with the water contact optics.

Can I prove any of this with scientific numbers?

Nope, that’s not my forte.

These are simply my personal finds and my personal preferences. Plenty will have other opinions and/or thoughts, and that’s great too. That’s why there are many options so all preferences can be met.

Paraphrasing Ansel Adams, the image is made 12” behind the lens. In other words, it’s not the gear, it’s the photographer that makes the image.

Above all, dive and enjoy capturing the moment!

Edited April 19Apr 19 by ChipBPhoto

On 4/16/2026 at 3:39 AM, Adventurer said:

Let’s not compare apples and oranges here and instead look at the genuinely relevant alternative to a 24–50mm paired with a wet optic (WACP-1, WACP-C, WACP-2, FCP, WWL-1 — or in your case, even the optically inferior WWL-C).

What you are really referring to is the relative zoom factor of the Z-mount or RF-mount lens: 50 divided by 24 equals 2.08x, which we can reasonably simplify to 2x.

A Nikon or Canon 8–15mm fisheye zoom gives you 15 divided by 8, which is 1.9x — so, again, effectively about 2x.

My suggestion would be to pair that fisheye zoom with a high-quality 2.0x teleconverter, or even a 1.4x teleconverter. I am fairly sure you would end up with significantly better sharpness and overall image quality behind a dome than with any of the specialized underwater optics mentioned above. The image-quality penalty from a good teleconverter is minor compared with the gain in corner sharpness you get from using a strong lens behind even a small but perfectly positioned dome. On top of that, such a setup is far more travel-friendly and affordable than those bulky correction optics, and you do not need to “burp” it underwater.

Last but not least, an 8–15 with a 2.0x teleconverter will project actual corners onto your full-frame sensor — no black corners.
--> No hallucinated corner sharpness.

This is exactly the kind of question I wanted this thread to examine.

In the Canon case, for example: would you get a better optimized result with the current Canon RF 24–105mm IS STM, or with one of the two older EF lenses that Nauticam recommended for use with the early WACP in its 2018 catalog when used via the RF-EF adapter?

Those two EF candidates were:

• Canon EF 28–70mm f/3.5–4.5 II (2.5x zoom ratio)

• Canon EF 28–80mm f/3.5–5.6 II (2.85x zoom ratio)

At the time, the 28–70mm was Nauticam’s recommended option.

But when you compare land-based tests of those lenses, both perform rather poorly compared with the center sharpness of even inexpensive modern RF glass. Lens design, manufacturing, and material science have improved to a degree that should not be underestimated in recent years.

So the practical takeaway may be this: make the WACP work with the Canon RF 24–105mm IS STM, but discipline yourself not to use it at 24mm. Instead, use it consistently from 28mm onward, up to the maximum usable zoom range allowed by the front optic. That should give you more modern technology and, quite possibly, better overall results.

Two corrections to your above statements;

1. I never need to "burp" my WACP
2. Traveling with a WWL is significantly easier than traveling with a medium or large dome.

Edited April 19Apr 19 by OneYellowTang

Today I shot the Nikon 8-15 fisheye + 1.4tc (old kenko) behind a 140mm dome using a 3d printed 40mm port extension and custom zoom gear. I think it worked very well. The "full" field seems to be at 12mm. A few shots were at 11mm and have very slight clipping.

Nikon Z8 with Retra Maxi strobes

12mm full field shots:

15mm "bonus 1.4x zoom" shot:

Edited Monday at 04:40 AM5 days by Dave_Hicks

9 hours ago, Dave_Hicks said:

Today I shot the Nikon 8-15 fisheye + 1.4tc (old kenko) behind a 140mm dome using a 3d printed 40mm port extension and custom zoom gear. I think it worked very well. The "full" field seems to be at 12mm. A few shots were at 11mm and have very slight clipping.

Nikon Z8 with Retra Maxi strobes

12mm full field shots:

15mm "bonus 1.4x zoom" shot:

Thanks @Dave_Hicks Nice colors! And personally , I’m a sucker for divers/people in frame. So effective zoom range 12-15? What kind of FoV do you appreciate to get there with the TC, approximately? And what’s your verdict on fuzz and sharpness all across compared to using the wwl? Difficult to say perhaps and not that important in such a locale, but would you consider this a more or a less straight option to the 24-50+wwl?

Edited Monday at 01:37 PM5 days by Christian K

53 minutes ago, Christian K said:

Thanks @Dave_Hicks Nice colors! And personally , I’m a sucker for divers/people in frame. So effective zoom range 12-15? What kind of FoV do you appreciate to get there with the TC, approximately? And what’s your verdict on fuzz and sharpness all across compared to using the wwl? Difficult to say perhaps and not that important in such a locale, but would you consider this a more or a less straight option to the 24-50+wwl?

The FoV is pretty good. I really like the 15mm native field, and was hoping to get just a bit more reach for scenarios where that might be desirable. Sharks, etc where you might not get to point blank range. That is where the WWL-C excels with it's near-macro to wide angle range. The 1.4tc gives the 8-15mm a taste of that flexibility. I don't see a huge compromise in sharpness so far, but will take a few more days of images to decide.

Here is a Zero range 12mm full field shot from yesterday:

Don't you just hate it when some undersea creature decides to have you for lunch?

Giant Pacific Octopus (Enteroctopus dolpheini)

Nikon Z8 w/8-15mm Fisheye lens + 1.4TC, f9@1/160s iso320, Pair of Retra Maxi strobes with 4500k filters

8 hours ago, Dave_Hicks said:

That is where the WWL-C excels with it's near-macro to wide angle range. The 1.4tc gives the 8-15mm a taste of that flexibility. I don't see a huge compromise in sharpness so far, but will take a few more days of images to decide.

I have the same opinion. The 8-15 + 1.4x TC is a terrific setup for close larger animals in an ultra-wide FoV. It’s my go-to for manatees, for example. I also prefer this combo if I know I’m photoing wrecks, especially for wide exterior or interior frames. I find the water contact optics at 130 degrees are often not quite wide enough for full room captures in a confined space. That’s where the 8-15/TC wins every time.

As far as IQ, honestly they both seem about the same to me when viewing without a high zoom on the screen.

Great octo-action frame @Dave_Hicks !

Edited Tuesday at 09:36 AM4 days by ChipBPhoto

11 hours ago, Christian K said:

Thanks @Dave_Hicks So effective zoom range 12-15? What kind of FoV do you appreciate to get there with the TC, approximately? And what’s your verdict on fuzz and sharpness all across compared to using the wwl? Difficult to say perhaps and not that important in such a locale, but would you consider this a more or a less straight option to the 24-50+wwl?

The field of view can be calculated, assuming it's an equisolid projection, here'a table for the 8-15 on a full frame with data based on a diagonal field of 175° which is what I have seen reported as the filed of the Canon 8-15 lens:

Focal length	Horizontal	vertical	diagonal	Rectilinear
8-15				equiv
8	Circular		180.0	FE
15	140.7	90.4	175.0	6.5
21	97.2	63.7	118.4	15.8
30	67.0	44.3	80.9	27

The last column is the focal length of a rectilinear lens with the same horizontal field, it shows you should get similar reach to a 16mm rectilinear with the 1.4x attached at full zoom (21mm focal length)

The last row is where it gets interesting, if you can adapt a 2x you the equivalent reach of a 27mm lens and effectively a 4x zoom in terms of horizontal field. But so far only an adapted Canon 8-15 with a Sony 2x has shown good quality results. The Kenko 2x image quality doesn't seem the best and fitting a Canon 2x to an RF-EF converter is locked out, I think there was one post on here about that where someone machined a third party RF-EF adapter to use a Canon 2x with the Canon 8-15.

6 hours ago, Chris Ross said:

The Kenko 2x image quality doesn't seem the best and fitting a Canon 2x to an RF-EF converter is locked out, I think there was one post on here about that where someone machined a third party RF-EF adapter to use a Canon 2x with the Canon 8-15.

I‘ll be bringing that setup to the water soon with the Canon RF 2.0x - I have also extensively shot the canon 8-15 with the Kenko 2.0x and love it. The IQ degradation is acceptable from the Kenko 2.0x as a trade for the enormous flexibility.

That said, I always look forward into finding more optimized image quality gear.

Special thanks also to @ChipBPhoto for sharing his extensive impression on WWL and WACP family. It confirms my impression that the only interesting candidate is the WACP-1 which comes at higher costs and weight. If you already operate an 8-15 Fisheye then the barrier to buy this is quite high as two good teleconverters will get you almost there as well.

However I must gnarl that the Canon 2.0x TC is also a heavy beast compared to the Kenko 2.0x 😅

I think the best example for simple design and truly lightweight and absolute superior optic ist the old Nikonos 15mm (equivalent to 20mm prime). I wish we had more of that and an option to utilize it in the Canon RF mount system.

Teleconverters do degrade the image. So a ”better” lens+teleconverter might give you a worse IQ result than a ”lesser” lens w/o converter in some other combo/set-up. Worth considering.

Edited Tuesday at 12:34 PM4 days by Christian K

4 hours ago, Adventurer said:

I‘ll be bringing that setup to the water soon with the Canon RF 2.0x - I have also extensively shot the canon 8-15 with the Kenko 2.0x and love it. The IQ degradation is acceptable from the Kenko 2.0x as a trade for the enormous flexibility.

Be interesting to see some comparison images especially with the RF 2x.

When the discussion comes to Kenko TCs for Canon EF mount, one must say that there exist TWO versions of both 1.4x and 2x TC: the "Teleplus HD DGX" and the "Teleplus HD pro DGX"...

I have the Kenko Teleplus HD DGX 2x TC version and used it few times with the Canon 8-15mm on Sony A7R5. Unfortunately, the IQ suffers a lot with this TC (too much for my taste).

In comparison the Kenko Teleplus HD pro DGX 1.4x TC works very well with this fisheye lens (for me and that is what also several others reported here)...

I do not own the Teleplus HD pro DGX 2x TC, but in the tread linked below, Massimo ("guest") has tested it and found that it worked very well (maybe comparable to the Sony 2x TC, that can be used on Sony cameras together with the Canon 8-15mm with sufficient quality):

Edited Tuesday at 02:50 PM4 days by Architeuthis

The initial statement “You cannot improve a lens’s in-air optical performance underwater.” is clear and true, but exceptions exist...

(The Tokina 10-17mm fisheye lens behind a domeport, e.g., performs clearly better UW compared to the performance at the surface (especially when used together with a 0.71x speedbooster)...)

Are optical jewels automatically performing better compared to, average quality, kit lenses for UW WA?

Certainly not.

Too many factors that ruin IQ UW ...

An UW WA setup that would provide the idential optical quality, as an average kit lens provides on the surface, would be a true gem and a favorite for all of us...

Already in the center the sharpness is diminished, just by the water (absorption and diffraction of the light), even when it is clear, not to speak about bad vis, to an extend that goes below the standards we are used on the surface. Not to speak about the corners that never can be sharp when using a domeport (or water contact optics) and the unpleasant distortions that (mostly rectilinear) lenses produce away from the center...

The question is rather: what system, in combination, gives the least impaired results (lens/domeport combination, fisheye lens (with and w/o TCs), water contact optics/lens combination)?

The lens itself is certainly a contributing factor, but it must not be overrated:

A high quality WA lens that does not perform well behind a domeport can not reach the IQ of a kit lens in compination with water contact optics (e.g. because of a field curvature that is opposite to the curvature of the virtual image produced by the domeport; entrance pupil that makes correct positioning difficult).

Another example is a 180° diagonal fisheye lens that, just because of the shortest object distance and hence minimal IQ detoriation produced by the water, gives way sharper images compared to a lens with considerably larger object distance...

Only with lenses that work very well together with a domeport and in very clear waters one may be able to see differences that come from the lens itself.

In my personal experience, the Sony 20-70mm and Tokina 17-28mm (Sony FF) and the Zuiko 12-40mm pro (Oly MTF), all behind Zen DP170, perform very well UW and give (subjectively) sharper images compared to Sony 28-60mm/WACP-C (FF), but only when conditions are at their best. The pure Canon 8-15mm fisheye comes close in sharpness to the Sony 20-70mm/DP170, but when used with TCs (Kenko 1.4x Teleplus HD pro DGX or Sony 2x TC) IQ is comparable to 28-60mm/WACP-C...

As far as I know, none of these lenses provides the highest optical standards on the surface, but the Sony 28-60mm kit lens is certainly the least performing lens of them and a league below the others (Chip reports, however, that 28-60mm gives better results with WACP-1, hence 28-60mm/WACP-C is not the last rung in the ladder)...

Wolfgang

Edited Tuesday at 02:50 PM4 days by Architeuthis

15 hours ago, Architeuthis said:

the Sony 20-70mm and Tokina 17-28mm (Sony FF) and the Zuiko 12-40mm pro (Oly MTF), all behind Zen DP170, perform very well UW and give (subjectively) sharper images compared to Sony 28-60mm/WACP-C (FF), but only when conditions are at their best. The pure Canon 8-15mm fisheye comes close in sharpness to the Sony 20-70mm/DP170

Very interesting Wolfgang, even though I am not a Sony User but this would supports the initial thesis of a very good air based „exit-glas“ (lens) bringing the right photons to the table 😉

Could you specify with a link which Sony 20-70 exactly you mean? Also interesting that you consider the 8-15mm a slightly less sharp performer.

Have you ever used/tested WACP-1 oder WACP-2, Wolfgang and an impression on that one to compare?

33 minutes ago, Adventurer said:

Very interesting Wolfgang, even though I am not a Sony User but this would supports the initial thesis of a very good air based „exit-glas“ (lens) bringing the right photons to the table 😉

Could you specify with a link which Sony 20-70 exactly you mean? Also interesting that you consider the 8-15mm a slightly less sharp performer

It is the Sony 20-70mm f/4 G lens. It is not of the highest optical quality (Sony labels such lenses with "GM"), but is regarded a decent performer...

Here you can find serious over-water reviews of both Sony 20-70mm and the Canon 8-15mm. The reviews state that both lenses are very sharp (but one cannot directly compare the absolute values in lp/mm, since the Canon values were measured on a completely different camera/sensor):

https://www.lenstip.com/643.1-Lens_review-Sony_FE_20-70_mm_f_4_G_Introduction.html

https://www.lenstip.com/311.1-Lens_review-Canon_EF_8-15_mm_f_4_L_Fisheye_USM_Introduction.html

My "ratings" of the UW performance of different lens/port/water contact optics combinations are based on dozends, sometimes hundreds of dives and are completely subjective. No test carts and/or measurements, motifs and conditions are always different.

It is a pity that the companies that develop and sell domeports and water contact optics do not make their measurements/test chart photos, that they certainly have, accessible to the potential customers (I suspect they have reasons)...

Here links to some UW photos I made with Sony 20-70mm and some other combinations discussed here:

https://www.dpreview.com/forums/threads/sample-photos-from-sony-20-70mm-f-4-and-a7r5-uw.4724115/

https://www.dpreview.com/forums/threads/canon-8-15mm-fisheye-lens-with-sony-2x-tc-on-sony-a7r5-sample-photos-part-1.4779356/

https://www.dpreview.com/forums/threads/canon-8-15mm-fisheye-lens-with-sony-2x-tc-on-sony-a7r5-sample-photos-part-2.4779452/

https://www.dpreview.com/forums/threads/canon-8-15mm-fisheye-lens-with-sony-2x-tc-on-sony-a7r5-sample-photos-part-3.4779455/

33 minutes ago, Adventurer said:

Have you ever used/tested WACP-1 oder WACP-2, Wolfgang and an impression on that one to compare?

No, I never used them. I could spot several WACP-1s at UW photography workshops and immediately was sure that I do not want to deal with such big staff (I find the "compact" WACP-C version already big and heavy enough)...

Edited Wednesday at 07:50 AM3 days by Architeuthis

Another 8-15 +1.4tc shot that I really like from God's Pocket. A close-focus-wide-angle shot of a decorator crab on a sponge. Decorator crabs have a lot of personality and cover themselves is clever ways to match their environment. These crabs are specially tailoring their camouflage to incorporate parts of the sponges they are living on.

Nikon Z8 w/8-15mm Fisheye lens + 1.4TC, f5.6@1/50s iso100, Pair of Retra Maxi strobes with 4500k filters

Some input on many of the optics discussed in this thread.