Testing Nauticam N120 Port Extension for 140mm and 180mm domes with wide angle lenses

[DreiFish]

I wanted to test to see the correct port extension for various wide angle lenses with the 140mm fisheye dome and 180mm wide angle dome for the Nauticam N120 full frame system. I also wanted to compare resolution of the different lenses and how the position of the lens and the size of the dome impacted the resolution. Lenses tested:

• Canon EF 8-15mm Fisheye Zoom
• Canon EF 8-15mm Fisheye Zoom + 2x TC
• Canon RF 14-35F4 L Zoom
• Canon RF 15-30 Zoom
• Canon RF 16mm Prime
• Laowa 10mm Prime

 

All tests done with the Canon R5C. 

 

Here's the test rig setup -- a chessboard to see if the straight lines continue straight above the water (to determine if port extension is too long or too short), with some paper bills glued to it to eyeball resolution. 

 

I haven't gone through all the photos yet, but already some interesting findings. 

 

1. EF 8-15mm zoom needs something like a 35mm extension with the 140mm dome, not the 30mm extension recommended by Nauticam. Here's the first image at 30mm, and the second at 40mm. You can see 30mm puts the entry pupil in front of the center of curvature of the dome, while the 40mm extension puts it slightly behind, and vignettes as a result. 

 

Here are the same images de-fished to highlight the effect. Look at the above-water portion. If the entry pupil is exactly in the center of curvature of the dome, the lines should continue straight above water. If it's too far forward, the above water portion appears smaller. If too far back, it appears bigger.

 

 

 

 

40mm extension is almost correct, so I'd guess 37-38mm is what would be perfect. Of course, the problem is (as shown above) that it vignettes, and removing the dome shade wouldn't fix the issue. It vignettes on the inside of the dome. A 35mm extension thus might be the best compromise -- or 38mm with a wider port, like Marelux's 125mm diameter ports. 

 

The incorrect placement of the entry pupil doesn't have much of an effect on the center sharpness (30mm on left, 40mm on right). Microcontrast might be a bit better though with the 40mm extension.

 

 

But there is a noticable improvement with the longer port when it comes to the corners.

 

 

More to come.

[DreiFish]

Now, the RF 16mm prime. All shots at F13, ISO 100. 

 

Unfortunately, this lens is not great for underwater. Nauticam recommends no extension at all, and I tried that with the 140mm dome.  But because the lens is so short, the entry pupil is quite a bit further than where the lens sits even with no extension rings, and there's no way to improve it.

 

 

Center resolution is not bad. Corner (or, really, more like edge resolution) is not as good.

 

[DreiFish]

Contrast with the Laowa 10. With no extension, it vignets slightly, but it's only the dome shade (which was designed with the more limited vertical field of view of a fisheye lens in mind). If you remove the shade, you should be able to get the full field of view. I tried also with a 20mm extension, but that produced very significant vignetting inside the port.

 

 

Notice the lines are almost straight above the water. Just sligtly smaller. Basically, you would get perfect placement with a 2mm extension.  Maybe a 10mm extension could work, but then the entry pupil would be too far back of the center of curvature of the dome, so image quality would likely not improve.

 

Center resolution is better than the RF 16mm prime or the EF 8-15, but the corners.. well, they're pretty bad.

 

 

Edited June 30 by DreiFish

[DreiFish]

Now the RF 14-35 F4 L zoom, at 14mm. All pictures again at F13, ISO 100.

 

The lens sits too far back from the center of curvature with the 180mm dome. Here it is with a 30mm, 40mm (what Nauticam recommends for 180mm dome), and 50mm extension.

 

 

Even 50mm is slightly too short, but already at this point it's vignetting heavily. I think this lens needs to be used with a 230mm dome, the 180mm doesn't have enough field of view. Best compromise if you're set on using it with the 180mm dome would be a 45mm extension I guess, but you might get vignetting even then. 

 

100% crops from the center and corner with 40mm extension. The center is a bit better than the RF16 prime but not as good as the Laowa. The corner is much better than the Laowa but kinda on par with the RF16 prime (which is behind a 140mm dome)

 

 

 

Edited June 30 by DreiFish

[DreiFish]

Finally, the RF 15-30. 15mm, F13, ISO 100.

 

With the 180mm dome, it needs a similar extension to the RF14-35, just slightly shorter. Here it is at 30mm, 40mm, and 50mm.

 

 

 

At 50mm it already vignettes, but the entrance pupil has already been moved forward past the center of curvature. 40mm puts the entrance pupil behind center of curvature. At 40mm it is a bit closer to the correct placement than the RF14-35. This lens probably also needs a 230mm dome, but 45mm should be about right with the 180mm dome and shouldn't vignette much. (Incidently, Nauticam recommends 30mm, which is clearly wrong. 40mm is better)

 

 

Center and corner crops at 40mm. Center resolution is not as good as the RF14-35 or Laowa 10mm, probably because the lens itself is not as good, but on par with the RF16.. Corner is better than the Laowa 10mm,  RF16 and RF 14-35 though. 

[Chris Ross]

The other solution for the 14-30 and 15-30 might be zooming in a little bit?  Can you zoom in enough to use the 50mm extension without vignetting?

[dentrock]

Thanks for the tests.

But what's your measurement for sensor to housing port flange for your Canon R5C (so we can estimate performance for other brands)?

[dentrock]

PS: also have not seen a measurement for EP from lens flange for the Laowa 10. I have one on order but goodness knows when it will turn up.

 

Any chance of a quick estimate for that too (method estimating apparent position of diaphragm is fine if you are reasonably careful)?

[Architeuthis]

Thank you - very interesting...👍

 

What apertures were used?

Do you also have WWL/WACP-x and could compare to these?

 

I am very curious to see the results with TCs too....

 

 

Wolfgang

Edited June 30 by Architeuthis

[Davide DB]

5 hours ago, DreiFish said:

Contrast with the Laowa 16.

 

Did you mean 10mm?

[DreiFish]

5 hours ago, Chris Ross said:

The other solution for the 14-30 and 15-30 might be zooming in a little bit?  Can you zoom in enough to use the 50mm extension without vignetting?

 

On the lists of things to test when I have time again, probably in 2 weeks when I'm back from Mexico.

 

4 hours ago, dentrock said:

Thanks for the tests.

But what's your measurement for sensor to housing port flange for your Canon R5C (so we can estimate performance for other brands)?

 

Might. be a bit tricky to measure. I believe Interceptor 121 did this for the Nauticam Sony housings at some point? If so, it would be easy to estimate adding 35mm (for the n100-n120 port adapter) to that. How else would I measure that? I have a caliper.. I guess I could do lens mount to front of housing with that or a ruler and add the manufacturer's flange distance. Do housing manufacturers share this information anywhere? 

 

4 hours ago, dentrock said:

PS: also have not seen a measurement for EP from lens flange for the Laowa 10. I have one on order but goodness knows when it will turn up.

 

Any chance of a quick estimate for that too (method estimating apparent position of diaphragm is fine if you are reasonably careful)?

 

It's not on OpticalBench yet. This is what I've pulled so far from OpticalBench. And from housing manufacturers documentation.

 

 

 

 

3 hours ago, Architeuthis said:

Thank you - very interesting...👍

 

What apertures were used?

Do you also have WWL/WACP-x and could compare to these?

 

I am very curious to see the results with TCs too....

 

 

Wolfgang

 

All tests were done at F13 for consistency and expediency (otherwise I had to adjust the strobe power to take a series at different apertures. Took too long 🙂. I may do some expanded testing later at different apertures. For instance, the RF14-35 did clean up a bit in the corners at F16, but lost center resolution. 

 

I have the WWL-C and RF 24-50 I will eventually test as well.

 

1 hour ago, Davide DB said:

 

Did you mean 10mm?

 

Yes, corrected.