70mm or 90mm Nauticam extension 16-35mm lens

Hi just after some advise I have just got a Nikon 16-35mm f4 which I will be using on a full frame D800 behind a Nauticam 230 glass dome port. On the port chart they recommend a 90mm port extension but I am just wondering if I can get away with just a 70mm?

I have a 70mm and a 20mm so could put those Together to make a 90mm but Just seeing if any one uses a 70mm and if they are happy with the results.

Cheers Alex

Hey Alex

Not Nauticam (sorry) but I was using the 16-35 with a 230 domeport on my Subal D800 system.

I found the 90 extension and a +2 diopter essential for the lens. It’s a tricky lens to house and get sharp corners. Unless someone can report a positive experience with a 70mm extension, I’d stick with the 90 if the photo opportunity is a one-off and you do not have the time or chance to reshoot.

Ok cheers for that Ill try both and see if I can see any difference