Which port is good enough for Nikon 8-15 fisheye lens

Hi all
I would like to build a Nauticam system for my Nikon Z7 2 and Nikon 8-15 fisheye lens. Naturally I prefer a more portable and light port. However I don't want to sacriffy  image quality.  
Can I use the  N120 4.3" ACRYLIC DOME  ? Isn't it too small ?
or 
 N120 140MM OPTICAL-GLASS FISHEYE DOME PORT  ?

Or should I go with: 
 N120 230MM OPTICAL-GLASS FISHEYE DOME PORT II 
or
 8.5" N120 ACRYLIC DOME PORT ?

Thank you for your help

Ido

Hi Ido

As a fisheye the 8-15 doesn't need a big port. I've used the lens (admittedly on a D500) with a 100mm dome and the results have been excellent. I've also used it with an 8" port.

The only real time I've found the small port doesn't work is for over/unders. For that, the bigger the better.

As for acrylic v glass: I'm not sure you would really see any difference in image quality given all the other factors that impact on imagery underwater: turbidity, low light, particulants etc. I'd argue that glass is harder wearing and much more scratch resistant. That said, if you scratch glass, you can a have a big problem as it can't be rubbed out like scratches on acrylic.

Finally on port size, you may know already that a 230mm port (9") is WAY bigger than 8". I found the 230mm dome a real pain for travelling if you have the usual European baggage allowances.

If you are looking for light and portable, you might want to avoid a 230 dome. An 8" would be fine. 

1 hour ago, TimG said:

As a fisheye the 8-15 doesn't need a big port. I've used the lens (admittedly on a D500) with a 100mm dome and the results have been excellent. I've also used it with an 8" port

My experience with the Canon 8-15 behind a Zen 100mm/4 inch dome is that on a crop sensor camera the results were excellent.  When I switched to a full frame camera the results were nowhere near as good.  I switched to a Naurticam 140mm/5.5 inch dome and got excellent results again.

Thank you guys for sharing your experience. 

This is my first post in this forum. Great start !

Cheers

Ido

With full frame, a bigger dome is better, even with a fisheye. I use a 7" port (180mm).

Adam

Thanks Adam

I believe you mean this: N120 180MM OPTICAL-GLASS WIDE-ANGLE DOME PORT

https://www.nauticam.com/products/180mm-optical-glass-wide-angle-port

Hi Ido, The Nauticam port chart is here:  https://drive.google.com/file/d/12lTDlSDfIfjRSo2UvY0uaibU8P8-H_8C/view

They recommend the 140mm dome (with 20mm extension)  as most optimised.  They don't list the 180mm dome as an option - probably because it's not a full hemisphere (180°),  Rather it's about a 115° segment - radius of curvature is 110mm but diameter is  180MM - not 220mm.  This means you need to place the lens entrance pupil forward of the centre of curvature of the dome and this is not optimal.  I believe Adam has Seacam housings and they do have a 170mm dome.  I wouldn't recommend Nauticam's 180mm dome.

The other Nauticam options listed are the 230mm dome which is huge and the 8.5"acrylic dome, also quite large and being acrylic also buoyant. 

I am using the lens with FTZ adapter for the Nikon Z72. However I believe that the lens position is the same as on DSLR. 

Thanks

9 minutes ago, ido said:

I am using the lens with FTZ adapter for the Nikon Z72. However I believe that the lens position is the same as on DSLR. 

Thanks

Hi Ido

That sounds a bit odd. The FTZ is inevitably going to push the lens further into the dome. Do you not need an EXR to compensate for that?

The purpose of the FTZ is to bring the lens to the same distance from the sensor. I took a quick (and not Scientific...) shot of my 2 Nikons. On the right is Nikon D850 and on the left is Nikon Z7 2 with the FTZ. The location of the sensor in marked on each body with white icon. 

Interesting! Thanks.

Yeah, the sensors are pretty much aligned and, just as important, with the added FTZ the lens mount seems pretty much aligned as well. So the lens front end should be broadly in the same position in the dome port as it would with on a Nikon F mount camera body. 

8 hours ago, ido said:

I am using the lens with FTZ adapter for the Nikon Z72. However I believe that the lens position is the same as on DSLR. 

Thanks

That's correct, the port chart is again your friend: https://drive.google.com/file/d/1w9wyi7ea9pbgnlRXR_JaBk3BT4G3sZYD/view

You'll note it says for F lenses with FTZ adapter refer to the Nikon port chart.   It makes perfect sense for Nauticam to do it this way - set the camera position in the housing so that the FTZ adapter is in the same position as the F mount DSLR body flange.