OlDirtyDiver

Ideally you'd only focus on the specific area of element. But, the job requires expanding outward in concentric rings with each finer grit (each new grade applied 90º compared to previous), so with the small amount of real estate on that element you'd end up sanding most of it by the time you get to finishing grade. And that was the greatest challenge of that job; after wiping and drying the element you'd see residual haze on the outermost 1cm of the element, because that's hardest part to sand uniformly. Meanwhile, middle of element very easy to restore to mint. So I had to put some extra effort into the outer edge. But also knew that this would not be in middle of photo, and edge sharpness also not always expected to be as sharp as center anyway with domes. Just know that you can't really ruin the element attempting this. If you end up with the scratches still being slightly noticeable after drying element, or haze at edge, you'd just do the job again and know that it gets better every time. I did a single lens up to 5 times in trying to restore to mint (and each time just takes ~15min).

@Grantmac: I am corroborating @FOTOSUB, that dome is, fortunately, very reparable. I was in the exact same situation as you, with a very badly and deeply scratched front element from a metal flag mount inside a float that I hastily threw my housing into without cover. Very deep scratches I could stick fingernail deep into. I felt I had nothing to lose by attempting the polishing, lens was unusable otherwise anyway. Used the same kit I've always relied on for acrylic dome ports, 400 -> 12000 grit (https://micro-surface.com/product/nc-78-1-acrylic-restoral-kit/). The 12mm element is so soft it doesn't take that long at all. That kit starts with 1500, so I found some rougher grades down to 360 I believe, just to remove those deepest scratches. I was so impressed with the job I decided to do the same on the six other 12mm lenses I had, all had minor scuffs and I was trying to sell them all. I made them all look mint with the polishing (starting with 1500 grade on these) and sold them all successfully, receiving nothing but positive feedback from all buyers. You're never gonna find any spare parts for that lens I suspect. Japan is where I acquired every single one of my 12mm's.

@waterpixel I thought I might as well address your questions for the rest of the community. I suspect that there is very little awareness or information about the Sea & Sea 12mm out there, so I'm happy to help with my extensive experience depending on it exclusively for several years. Do you use focus peaking? One of my biggest reasons for depending on the Sea & Sea 12mm instead of Nikonos 15mm is that critical focus isn't nearly as much a concern, on account of the 12mm being a fisheye while the Nikonos is not. The wider the FOV, the bigger the depth of field in general with lenses. As a freediving and wide angle shooter, as opposed to a SCUBA-equipped macro shooter, it was important to me to not have to worry about critical focus. So I simply shot at smaller apertures, f/8 - 11 mostly, to ensure that my depth of field was so large that everything in my composition was in focus. I could do small aperture with the Nikonos 15mm too, but the fisheye FOV of the 12mm still provided significantly more focus dependability. That said, if you've got the time while underwater (I was on breath-hold), you certainly could take advantage of the focus peaking feature. I would consider it if I had to shoot at larger aperture due to ambient light constraint, or if subject especially close to camera, but I didn't have to worry about it for most everything I shot. Everything was simply in focus all the time. This was also important to me for video, where adjusting focus while filming wouldn't be ideal. How far behind the mount does the lens element extend? The element doesn't extend behind the mount at all. In the first two attached images I have the Nauticam mount on the Sea & Sea 12mm (left; right lens is Nikonos 15mm; wanted to show how comparable in size they are; identical height, 12mm just 0.5" wider). The only thing extending behind the mount is the built-in silicone flange that sits perfectly in front of the camera lens opening. The Sea & Sea 12mm is identical to the Nikonos 15mm (and other Nikonos lenses) as far as the mount and compatibility. The godfather of Nikonos lenses, Pawel Achtel (who devised the 3D UW filming solution for Avatar 2), lists those here (https://achtel.com/3deep/, https://www.facebook.com/share/p/17fZ8A5vKT/). With the Nauticam adapter you can use any of these lenses. Achtel is just as much a fan of the Sea & Sea 12mm as the Nikonos 15mm (https://www.facebook.com/share/17afUA2CPd/, https://www.facebook.com/share/v/1XT3qT2zG3/, https://www.facebook.com/share/p/17FSRFEyWL/). Want to add the Sea & Sea 12mm to your wet lens quiver, and see why I preferred it over the Nikonos 15mm? I've got one or two for sale! $600. 😃

@waterpixel Sorry for not replying until now, did not see any notification. The Sea & Sea wet lenses share the same Nikonos mount, so they work with the Nikonos adapter. I started with the Nikonos 15mm, but once I learned about the wider Sea & Sea 13mm I used it exclusively (such as for the shots I shared above). I actually bought several in great condition from the Japanese resell market since they are so rare (~$700). But I would happy to share them with any of you, as they are just sitting around.

+1 for using the Nikonos-fitting wet lenses on modern cameras. I feel like it's some sort of secret. My preferred lens is the Sea & Sea 12mm f/3.5 fisheye, over the Nikonos 15mm. The 12mm is much more rare, hard to find. I stockpiled a few because of this, but I am happy to spare one (or a few) for anyone who wants it. Everything I shot for nearly the last decade, both photos and video, was with the 12mm on a Sony a7 series with Nauticam housing and Nikonos adapter. Manual focus wasn't much of a concern because it's a fisheye. @chambersbelow

Hello, Any other freediving photographers in here? And anyone using old Nikonos wet lenses with modern housings/cameras? These two traits might distinguish me a bit. All recent work on Instagram. Thanks, Kurt @chambersbelow