It's Time to Talk About the Nikonos RS 13mm Again

[Alex_Mustard]

Just to add a photo to Mark’s report. The Sony converted RS-13 lens worked very well on the Z8 - from testing it as pictured. Really excellent news. 

Although as Isaac states it will need a custom port for N120. But otherwise good to go. 

[DreiFish]

Damn.. I guess there's no current option to adopt the RS13 for Canon cameras? It would require a donor lens of some sort I suppose?

[Isaac Szabo]

3 hours ago, DreiFish said:

Damn.. I guess there's no current option to adopt the RS13 for Canon cameras? It would require a donor lens of some sort I suppose?

 

Unfortunately there's not. Perhaps I could try converting a Canon donor lens at some point in the future. But it's a significant undertaking, and I don't anticipate having the time in the foreseeable future.

[WaterStories]

Would love to get this working on a Canon mount too, preferably RF (although EF could work) 👀

 

Without derailing the topic of 13mm, have any thoughts been given to some of the other UW RS lenses? Would it be a similar sort of process?

Edited March 6 by WaterStories

[Alex_Mustard]

For me, none of the other RS lenses are very interesting.

I have the 20-35mm, 28mm and 50mm still, but have never been seriously tempted to convert any of them. The 50mm is just a standard macro lens. The 28mm and 20-35mm are both UW corrected - but neither is as wide as they seem. Just as the Nikonos V 15mm is actually the equivalent of a 20mm lens, so the 20-35mm is something like a 24-42mm (I don't know the exact conversion), which limits its usefulness underwater.

 

Rene Aumann made an 18mm for the RS, but this was simply a land lens and dome combo - programmed and waterproofed (very expertly) to work with the RS camera. But not UW corrected. 

[Isaac Szabo]

I too feel that the other RS lenses aren't particularly interesting, and I think the 20-35mm would be more complicated to rehouse in a donor lens due to the zoom.

 

I do have interest in trying to convert the Sea&Sea 12mm and the Nikonos 15mm when I have some free time.

[Gerald Rambert]

Hi Everyone, 

 

I can see that there are a few posts on the RS 13 mm lens on the forum and I thought I might share my recent experience with it and the issue I encountered. Maybe some of you can also help me find a solution to my problems.

 

So, I recently purchased a Nikonos Rs 13 mm and had Seacam convert it for me. The conversion was super well done and the finish of the product is stunning. 

 

I have adapted the lens on my Sony A1 using a Monster Adaptor LA-FE2 and used it for about 3 weeks on multiple dives. 

 

First, I noticed that the lens was underexposing. When I would normally shoot at an aperture of F4 with a speed of 1/125, with the RS, I would have to bring down my speed to 1/30, 1/50 to have the same exposure compared to a normal Sony lens or Canon 5-15 mm. 

 

2 of my dive buddies also bought the lens and on the last dive, comparing our shots underwater I realized that they were shooting at a much higher speed than me. So we took a side-by-side comparison underwater.. with the same settings... my lens was underexposing about 4 stops. 

 

Once on land, we exchanged lenses and tried all the different monster adaptors and my lens was again underexposing on different cameras. 

 

How could the same product give different results in regards to exposition? is the real Aperture different? when the camera reads 2.8 is it actually 4.5?  Any idea why this could happen? 

 

In regards to the Autofocus, forget AF-C... it is useless and jams the camera. As for AF-S, the camera will freeze at least once per dive. You will need to turn it off, wait a few seconds, and let your flash fire... then you can turn it on again and carry on with your dive. I think the monster adaptor is the issue there...  

 

 

[Isaac Szabo]

Hi @Gerald Rambert. I'm guessing the reason you didn't get any responses on your other thread is probably that no one here has experience using the Seacam converted lens with the Monster adapter. If your Seacam converted lens is performing differently than the other lenses they converted, then that seems like a question best answered by Seacam. I think it's unlikely that someone here will have enough knowledge of the intricacies of their conversion to know what might be causing this discrepancy. 

 

One thing I will note is that 1/20 versus 1/8 is 1.3 stops. Also, the 1/8 photo appears to be slightly brighter than the 1/20 photo, so the actual difference may be smaller than 1.3 stops. That said, I'm not doubting your claim that your lens is underexposing. Hopefully it's something that can be fixed.

[Tom Kline]

Are you aware that the lens aperture reported in the camera when using RS lenses is not accurate? The difference is greatest at the smallest aperture. For this reason I only use RS lenses in M exposure mode on Nikons. Clueless about use on Sony.

[Isaac Szabo]

It's good to be aware of that, but it doesn't help explain exposure differences between different copies set to the same aperture. 

[Alex_Mustard]

I am well versed in the various conversions, having shot Seacam Converted for Nikon 13mm, Belic Converted for Nikon 13mm and Isaac Converted for Sony.

As Tom says, both the Seacam and Belic conversions do not report aperture correctly. At open apertures the difference is small, but gets more pronounced as you shut the aperture. Borut Furlan published a helpful look up table for converting the indicated aperture to the true aperture (very nice):

 

 

 

This relationship is the same on the Saecam and Belic converted lenses - but the Belic converted lenses only stop down to an indicated f/22 (a true f/14). 

 

The other factor is that the Monster adapter is poor. I've only tested the LA-FE2 converter (the one that works with older AF-D lenses like the RS-13) briefly, but found it unreliable on the one test I made. And definitely not something I would want to use on important dives. 

 

I do use the Monster LA-FE1 (which only works on newer Nikon F lenses with AF motors inside them). This is still not wonderful, but does work with AF-C and AF-S modes. I find this adapter is OK to use, although I wouldn't bet my life on it! One issue worth mentioning I have had is when using it in cold water (Silfra). Here I had communications issues and it would not report aperture correctly. Often shooting with a different aperture than I set!  I have never had that problem in warm water - and felt it was caused by a power drop caused by the cold.

 

Isaac's conversion turns the RS-13mm into a Sony lens - with all the advantages that brings. Which have been extolled before in this thread and is definitely the way to go if you want to use this lens on Mirrorless (either Sony or Nikon Z).

 

Alex

 

[Isaac Szabo]

@Gerald Rambert If you set your camera to f/2.8 and look into the lens front the front, can you tell if the aperture is opening up all the way? Or if you dismount the lens and manually move the rear aperture lever while watching the aperture through the back of the lens, does the aperture appear to open up all the way? Does the aperture lever move freely/easily and spring back closed when you release it? Does it appear bent or damaged? 

[Gerald Rambert]

Thanks a lot for your answers, really apreciate your comments. 

I am travelling at the moment and as Alex said it is totally unreliable with the monster adaptor and just could not take it with me on my trips which is a shame really...

I have checked the back of the lens and yes the spring brings works and the lever looked ok, but will compare again with my friends lenses... 

All of this is really strange.. i will make more test when i get back and do underewater comparison with my friends camera too underwater with side by side images. 

thanks again for your comments. Much apreciated. 

 

[Walt Stearns]

Going from a Nikon D850 to Z8 my Seacam converted Nikonos R-UW 13 became unusable as there is no working solution currently available for a F-mount lens with the old fashion autofocus to work via an adapter a Nikon Z mount or any other mount for that matter.

 

To bring it back to life for the second time I just had Issac convert from a Nikon F mount to Sony mirrorless E mount using a Sony FE 50mm f/1.8 Lens ($198.00 from B&H) as a doner lens. From there, I purchased a Megadap ETZ21 Pro Sony E – Nikon Z adapter (price point of $249.00) to provide a means for these two different mounts to effectively work together.

 

Was this endeavor worth it?

 

Dam straight it was.

 

Here are two images from a battery testing in ocean, not a pool to see what that this lens can do while shooting at wide apertures from F/2.8 to F/6.3. Note, the two images here were shot at 1/200 sec at F/3.2. Neither have undergone any cropping or de-fishing, I did however reduce the file a bit so they would load faster.

 

 

 

 

 

 

Edited July 27 by Walt Stearns

[MatthewSullivan]

awesome, Walt! How did you find the AF performance on the Z cameras?

[Walt Stearns]

Matt, the auto focus with the Megadap ETZ21 Pro adapter worked pretty well, but I want to do a few more dives with it to give it a more finale approval.

[ChipBPhoto]

On 7/27/2024 at 10:39 AM, Walt Stearns said:

Was this endeavor worth it?

 

Dam straight it was.

 

Here are two images from a battery testing in ocean, not a pool to see what that this lens can do while shooting at wide apertures from F/2.8 to F/6.3.

Nicely done Walt!  Glad to hear you and Issac were able to get a dependable solution.  And just in time for Goliath season!  
 

[christophe chellapermal]

@Walt Stearns Hi, fast forwarding to september would love to read more on your af experience on a z8 megadap isaac conversion thank you ! do you get your battery drained from the megadap ? 

 

Edited September 26 by christophe chellapermal