I am pretty ignorant of dome port design and theory so to the extent my question reflects ignorance, I apologize.
Nauticam makes a 180mm dome for use with the Olympus 12-40 and 7-14 micro four thirds lenses. To use that dome for the 12-40 lens, Nauticam suggests using a 47mm adapter and a 20mm extension ring. For the 7-14 lens, Nauticam suggests using a 55mm adapter alone.
Zen makes a 170mm dome that accommodates these same lenses, but for the 7-14 one needs to use a 60mm adapter and a 20mm extension, while for the 12-40 the 60mm adapter is used alone.
To put this in a simpler format:
12-40 = 67mm distance to dome
7-14 = 55mm distance to dome
(12mm difference between the two lenses with greater length for 12-40 lens)
12-40 = 60mm distance to dome
7-14 = 80mm distance to dome
(20mm difference between the lenses with greater length for 7-14 lens)
I realize these are different size domes but I have been told they have the same curvature and are essentially the same glass. The adapters and extension rings are all made by Nauticam and so are interchangeable between the dome port brands
How could both of these domes produce similar results with such different lens to dome distances and how can the two companies have such a significant difference in lens to glass distance between the two zoom lenses?)
Does lens to glass distance simply not matter? Is one of these dome ports "better" because of the differences or is it just a question of physical fit and no optical issues?
Has anyone tried using the Olympus 60mm macro lens in the Nauticam 12-50 port? Just playing with it, it seems to work out, although it is just ‘slightly shorter than the 12-50 lens. I have not tried this in the water but it seems it should work fine.