100mm or 140mm dome for 8mm FE with EM-5II?

I plan to use the 8mm fisheye (Olympus 1,8 Pro) with Olympus EM-5 II in Nauticam housing and am not shure wich dome to acquire. I sway between the Zen 100mm and the Nauticam 140mm.

(Eventually also the Zen 170mm (although I cannot image that this dome that has <180^o field of view works well with the fisheye (but Zen recommends this dome for the 8 mm fisheye))).

Is anyone able to report how the 100mm dome performs in comparison to the 140mm dome with 8 mm fisheye MFT (eventually also the 170mm dome) with respect to image quality, close focus distance etc.?

Thanks, Wolfgang

I can't help a lot but I made a similar inquiry about a year or so back and I use the 100mm dome because I like CFWA shots and the 100mm allows me to get the dome closer in some situations. I considered the 140 but went with the 100 for that reason. If I were not interested in the close focus ability, I would have gone with the 140. So, the answer, I think, depends on your usage.

I am not sure there is much added benefit in a larger dome than 140 for this format and lens, and am not sure what larger dome even works with the Oly 8mm.

I have used the ZEN Underwater optical glass ports for the Panasonic 8mm Fisheye in Nauticam housings for EM-5 and EM1, also for the Canon 8-15mmm Fisheye zoom for Sony A7R II and it works quite well for such a small package.

I now use the Nauticam 140mm also quite good for the Olympus 8mm because the Zen port does not work with this lens in the Nauticam housing.

Regarding larger ports I am also using the ZEN 200mm port with the Olympus 8mm Fisheye for larger subjects and over/under shots.

Phil: Perhaps I am misunderstanding your post, but the Zen DP-100 works for the Olympus 8mm and the Nauticam housing when used with the 30mm mini extension.

Hi Phil,

Since you have experience with MFT & 8mm FE with domeports from 100mm to 200mm, could you please comment about the difference in Image Quality, DOF, close focus distance and other issues, when you compare them?

As Drag points out, the Zen 100mm dome is also usable with the Olympus 8mm: http://www.jaredparsons.com/portchart/zen-only/by-combination-group/nauticam-n85/

Wolfgang

Wolfgang,

What did you ultimately settle on between these 2 ports? I'm going through the same decision right now :-)

I decided to go with glass (Nauticam 140) rather than acryllic (Nauticam 4.33") because I really don't see myself buffing out the inevitable scratches on the acryllic. So I was pretty much ready to get the Nauticam 140, but now I'm thinking that the Zen DP-100 may be easier to get close to subjects for CFWA type of shots. I wonder if the size difference between them is actually relevant in real world situations.

Unfortunately where I live there isn't an underwater photography distributor who has both of these options for me to try.

So I'm just curious what you went with.

Take care.
Bogdan

I can't help a lot but I made a similar inquiry about a year or so back and I use the 100mm dome because I like CFWA shots and the 100mm allows me to get the dome closer in some situations. I considered the 140 but went with the 100 for that reason. If I were not interested in the close focus ability, I would have gone with the 140. So, the answer, I think, depends on your usage.

 

I am not sure there is much added benefit in a larger dome than 140 for this format and lens, and am not sure what larger dome even works with the Oly 8mm.

Draq,

I have the DP-170 and it works pretty well with the Olympus 8 mm fisheye. I've enjoyed using it and there is no need for an extension with it. But it is fairly good sized and takes up more room in my carryon than the actual housing!

I appreciate your comments on the DP-100. I'm highly considering it at this point though I haven't come across any direct comparisons to the Nauticam 140 mm port.

Bogdan

A fish eye lens has different optics to wide angle lens, a rectilinear lens is designed to take a flat surface and project that onto a flat sensor. The fact that a dome port has a virtual image which is curved and also very close to the lens produces the problem with rectilinear lenses. Large domes work better in that situation because the radius of the virtual image is larger and closer to being flat. This allows the virtual image to fall within the DOF of the lens and so be sharp. An additional issue is having the nodal point of the lens at the centre of curvature of the dome, this ensures that aberrations are minimised.

A fisheye lens on the other hand is designed to take a 180 deg field of view and project it onto a flat surface. The focal length is very short as is the magnification so DOF is very large. This means it has no issues with taking a spherical virtual image and projecting it onto a flat surface as this is effectively what it is designed to do. So the only issue is how close to the nodal point is to the centre of curvature. Different dome manufacturers may do it better than others.

So by my understanding using large domes is not a benefit for this type of lens and it will happily focus on the dome of a small port.

Using larger ports that are not 180 deg segments of spheres may however prove to be a problem if you can't get place the nodal point where it needs to be and also have the lens far enough forward that it can "see" 180 deg out of the dome glass - so the front of the lens needs to be forward of the edge of the dome.

Scuba Geek has am article on dome optics which is useful and I found another on fisheye optics on 360VR.com. I would post links but for some reason that has stopped working for me and I can't paste text into the reply box.

Hi Bogdan,

I use the Zen DP170-N120 with 30mm Extension/Adapter (N120-N85) - optically this should be the same as your DP170-N85 with the built in 30mm extension. See here for example images: http://wetpixel.com/forums/index.php?showtopic=60280

The reason is that I can use the DP170 dome as well with the Panasonic 7-14mm (with 60mm Extension/Adapter) and the Zuiko 12-40mm (also with 60mm). So far the DP170 (and the Nauticam 45 Macro port) are the only domes/ports I have.

Now I am following the treads on WA/Fisheye with great interest because:

#1.: The DP170 is rather big and for CFWA a smaller port would sometimes allow to get closer (I think about the Zen DP100). I am, however, wondering whether the image quality would suffer (then I would not go for the DP100 and stay with the DP170 for the 8mm FE, or maybe go for the Nauticam 140mm (in case image quality is better than the DP170)).

#2.: The DP170 is not a hemispherical dome with a 180^o angle of view, as would be required for correct positioning of a FE lens (CrissCross pointed this out to me half a year ago, when I started to acquire all that gear)), as it is designed for rectilinear WA lenses (but for 7mm it is even to small a section of a sphere). So I am wondering, whether a true hemisphere as the Zen DP100 or the Nauticam 140 would give better image quality in the corners.

=> Maybe people using these hemisperical domes (as Drag) could view the fotos in the link above and tell us whether the corner sharpness is better with DP100 or Nauticam 140, when compared to DP170 (and Bogdan and others could post additional fotos with 8mm FE, for comparison)?

Wolfgang