Nikonos RS lens project finalized

Project Finalized: Nikonos RS Lenses for Nauticam, Seacam and Subal.
By Andrej Belic.

A few months ago I came up with a new idea that I felt could improve underwater photography. I had observed that the Nikonos RS lenses that were produced 20 years ago had a very high reputation regarding optical quality.

These lenses could only be used with a specific Nikonos RS amphibious camera (that essentially was a stripped Nikon F70 film camera in a very small waterproof housing). In order to protect its proprietary system, Nikon developed a unique electronic protocol not compatible with usual Nikon F cameras. This crippled the spreading of the whole system. The lenses and camera body were quite expensive and Nikon made a crucial mistake that meant the end of the whole project. The RS was using bright red o-rings that were made of silicone. Today colored o-rings have become standard but in the early 90s it was big news. As experienced underwater photographers usually know, a silicone o-ring must never be used with grease that contains silicone or otherwise it will swell. Nikon didn’t inform their users properly about it and so people flooded their housings. This was the main reason why the Nikonos RS project was stopped in 1996.

After that a lot of quality conscious photographers were missing Nikonos lenses on usual Nikon SLRs and their housings. With the advantages of digital photography nearly everyone who had used the RS system switched to conventional housings with dome ports.

The lenses still remain, and it was a matter of time before someone had the idea to adapt them for use with SLRs. To recap, this is what I have set out to achieve and you can read more about the project’s evolution here on Wetpixel.

This is a short video showing the electronic communication between Nikonos lens and Nikon DSLR:

Finalizing the Conversion.

At the end of September 2012, I have accomplished the Nikonos conversion system for three major housing manufacturers. It is a two staged process: First the lens is converted and electronically modified so that functions like AF, shutter speed, aperture, exposure mode, metering, Liveview AF and exposure compensation all work. This is an in-house process that requires that the lens has be sent in to us for service.

The second stage is to use an appropriate adapter that seals the port opening of the housing on one side, exactly as a normal extension ring would do. On the other side, it works as a mount for the RS-lens and is similar to the original bayonet of the Nikonos RS camera. In order to overcome any potential problems with original Nikonos o-rings we have supplied our proprietary o-ring that works with any o-ring grease and is reinforced for additional safety.

We have tried and tested all adapters personally to a depth of 60m and they have worked successfully. More depth is possible but we didn’t test it. The adapters are made of 100% marine grade aluminum and come in black color as standard. We have tried to make the mounting as user friendly as possible and will provide a detailed instruction manual.


The Nauticam mount is the most comfortable of all housing brands. Simply place the RS adapter into the housing as you would do with a normal port, turn the red lever and lock the port. Since it’s the largest opening of all housings it is even possible to have a look at the focus scale of the 13mm RS fisheye lens that is calibrated for underwater. The compact 28mm will also work with the adapter. Nauticam is the only housing providing enough space for the compact 50mm macro lens although we have not tested it yet.


We’ve made adapters for Seacam housings since we got various requests for it. For it to function, you have to remove some parts on the inside of the housing. However it is very easy and with the Seacam D800 housing it takes only a few seconds. While using the lens on a Seacam housing you won’t have access to focus control, zoom control, and lens release. However all controls can instantly be retained when switching lenses. Unfortunately this was the only way to house the optical superior Nikonos lens in a Seacam housing. Secam housings are compatible with the 13mm and 28mm lenses.


The adapters for Subal (Type 4) work without restrictions: Pull the spring loaded zoom control wheel to the side. Screw in the RS adapter from 9 o’clock to 12 o’clock and engage the port lock on newer housing models. Subal also provides enough space for 13mm and 28mm lens.

How to mount the RS lens.

Again this is relatively easy but might take time getting used to. With usual housing-lens-port combinations you have two bayonets that are not connected: camera-lens and housing-port. With the Nikonos Conversion System you have three and all are linked together: camera-lens, lens-adapter and adapter-housing. This is inevitably a more complicated setup. We have provided markers on the adapters to make aligning as easy as possible.

Sea & Sea and Aquatica?

We have received various requests for Sea & Sea but as the port mount is too small for the 13mm lens with adapter, we cannot support them. Aquatica may be supported in future, so if there are any Aquatica owners who’d like to use this setup feel free to register your interest.

What about 20-35mm RS zoom lens?

Unfortunately the 20-35 is too large to be accommodated in any current housing port. I’ve already electronically modified one prototype so that it can communicate with regular Nikon DSLRs and I’m working on a very special solution that will be presented after the New Year holiday.

Test results.

We have tested the 13 mm with the Nikon D3s and the D800. The latter, with its 36 megapixel resolution is well suited to exploit the most of underwater optics. I have uploaded some simple pool shots for further examination and there are more scientifically tests to come: These are available to download (RAR file format) for inspection.

The 13mm lens is much better than the 16mm Fisheye Nikkor with any dome port (we had 6” and two different 9” domes), free from chromatic aberration, offering way more resolution, sharpness and contrast across the entire frame. This is a real sensation since usually all fisheye lenses do have chromatic aberrations (purple or green fringing in high contrast scenes).

We have also tested the 10.5mm DX Nikkor (which is optically superior to the 16mm) and state of the art 9” domes (Zen/Subal and Seacam). Here the 13mm is better in terms of resolution, contrast, sharpness and lack of chromatic aberrations. In the corners the sharpness is similar but this is a comparison between DX/9” dome and FX/4” dome.

We have examined the reason why the 13mm is so much better and apart from the coating the dome of the 13mm is not a typical dome but a real lens with varying thicknesses of glass in different areas. Other advantages of the lens are the very small size, comparable to that of a mini dome, and its’ weight of only 1kg. The close focus is only 7cm or 4cm (w/o rear filter holder) from dome surface giving DOF from glass/water interface at smaller apertures. It’s also possible to mount magic filters.

I think a great goal has been achieved and I’m very excited that after 20 years it is possible to use the optical capabilities of RS lenses on new Nikon DSLRs. The Nikonos Conversion System is ready to ship. Expect a turnaround time of 3-4 weeks depending on the country you live. And feel free to ask any questions.

A red sea star 5 cm away from the 13mm dome

About the author: Andrej Belic has been taking picture underwater for 12 years with Seacam, Subal and Nauticam housings. The project to adapt Nikonos RS lenses for use with current Nikon cameras is owned by him. He found, after writing various reviews of housings, strobes and video lights that he wished to manufacture his first product. He plans to add more products in the future.