Here are some thougths on the domeport to buy:
=> For the 8mm FE one needs theoretically a full hemisphere (or even a bit more of a full hemisphere) as the diagonal angle of few is 180o. This is because the entrance pupil of the lens has to be put at the center of radius of curvature - this distance is:
r=50mm for the Zen DP-100
r=70mm for the Nauticam 140 port
r=110mm for the Zen DP170
r=110mm for the Nauticam 180
r=110mm for Zen DP200 (this domeport is no longer available)
The larger the radius, the further away from the camera and the bigger the virtual image produced by the domeport is and hence the better the image quality.
The saying is, however, that FE lenses tolerate much more malpositioning in this respect as rectilinear lenses do. I cannot directly compare, but I do not see a obviously worse image quality in my images (Oly 8mm FE with Zen DP170) than in e.g. in the image shown above by matrixed82. But of course who knows how the performance would be if compared in a rigorous test?
(such real test, by the way, are lacking - there are many reviews and the bottomline is always "gorgious (buy, buy, buy...")
=> What domeport now for a rectilinear WA lens?
As CrissCross points out, the angle of view of these lenses is considerable smaller when compared to FE:
The larger the radius, the better the image quality is finally. Therefore there exist relatively large domeports that are smaller sections of a sphere than a hemispehere, such as Zen DP170 or Nauticam 180. Depending on the diameter of the port, the largest angle of view that is possible without vignetting is:
Zen DP170(r=110mm; d (diameter of the port)=170mm): 101o
Nauticam 180 (r=110; d=180): 109,8o
Zen DP200 (r=110; d=200): 130,7
Of course I do not have vignetting at 7mm with the Zen DP170, but this means the positioning of the lens is not correct when using the 60mm extension (and if the correct extension would be used, there would be vignetting, of course).
=> Again I must say I have no idea how much this mispositioning (both for 8mm FE and Pana 7-14mm) worsenes the image quality in real life (as no real comparison tests on this issue are available).
=> In case I would buy lenses and domeports now (I started a year ago and did not know about these problems then), I would go for Oly 8mm FE (1st prioritity), Pana 8-18mm (2nd priority) and Nauticam 180 with appropriate extensions. Later I would add the Zen DP100 to my gear, because this port allows to get closer to the object than the larger diameter ports do (I will buy this smart little port sooner or later).
=> There is an additional problem: the companies do not say how much mispositioning is when using their recommended extensions (of course it is easy to calculate that correct positioning at 7mm is impossible with the DP170)
- therefore the larger diameter does not automatically lead to better results, it also depends on the extension...
=> A last word on image quality with rectilinear WA lenses: The differences in IQ are minimal between the Pana ad Oly 7-14mm (see e.g.: http://www.photozone...lympus714f28proand http://www.photozone...30-pana_714_4). I could not find a real test of the Pana 8-18mm so far. The larger aperture of the Oly may be better for the AF, but one must close aperture to minimum 8.0 to get reasonable results.3
A fact is also, that UW the domports eats up so much of the IQ of a lens, that these parameters are probably not relevant for using the lens UW in domeports.
Edited by Architeuthis, 28 January 2018 - 09:22 AM.