EXRs: What's a millimetre or two amongst friends?

I'd welcome some expert thoughts on this:

I've been thinking for some time about adding the Nikkor 10-24 lens to my Subal system which I know a few readers use with success. My Go-To wide-angle is the Tokina 10-17 but I'd like slightly more reach. I'm thinking dolphins and sharks.

Subal guidance is the 10-24 needs the 8" domeport (which I have) plus a zoom ring and a 50mm EXR. 

With all the gear I have, I can put two EXRs together and, bingo, can come up with a 51mm (18+33).

Would that extra 1mm make much - any? - difference?

Perhaps!

The short answer it that it needs to be tried out. Most manufacturers tend to use the closest 5mm increment when recommending extension rings, so my guess is 1mm should make no difference.

I really like the 10-24mm with the D500...

Adam

51mm might work even better. If it does not effect Vignetting at the wide end it will work. But like all things, try it.

58 minutes ago, adamhanlon said:

I really like the 10-24mm with the D500...

Yeah, I remember. Tinman too.

Thanks to you both for the advise. Sounds good. And yeah, try it for sure.

Give it a try, you can check for vignetting in air, just assemble it all and have a look.  I doubt 1mm would make much difference.

3 hours ago, ChrisRoss said:

Give it a try, you can check for vignetting in air, just assemble it all and have a look.  I doubt 1mm would make much difference.

Thanks, Chris!

No worries, by my way of thinking if 1mm made a difference everyone using the likes of the Zen DP-170 and Nauticam 180mm dome with wide angle lenses would be having significant problems, the geometry of those domes forces many wide angle lenses to be positioned with the entrance pupil 10-20mm forward of the of the centre of radius of curvature to avoid vignetting.  The domes on those have a radius of curvature of about 200-210mm but are a small segment of a hemisphere, which means the centre of curvature is 30-40mm down inside the extension, while many wide angle lenses have the entrance pupil right up near the front.  I did the calculations for my Zen DP-170 and Panasonic 7-14mm with the recommended extension and as I recall the centre of curvature was about 10-20mm behind the entrance pupil.

On 12/20/2022 at 2:46 PM, adamhanlon said:

I really like the 10-24mm with the D500...

Adam

Adam, your D500 was in a Nauticam housing, right?