Dome musings

As I was looking through some port charts I began to wonder about a few things and thought I would mention them here.

Zen used to make a 200mm dome.  It is now discontinued and I wonder why.  It seems something between 180 and 230 would be desirable.  Was there just no demand?  Did it offer no optical benefit over a 170 or 180?  Was it close enough in size to a 230 that potential buyers just went for the larger dome?

Similarly, for many rectilinear wide angle zooms, Nauticam lists the smallest recommended port option as an 8.5 inch (215mm) acrylic dome.  Why not make an 8.5 glass dome for better buoyancy characteristics and scratch resistance?  No demand? Too close in size to the 230?

I am not very knowledgeable on dome theory, like questions of radius, hemispheres, etc., so maybe this is obvious to the rest of you, but Zen makes a 170 and Nauticam makes a 180 and they, for the most part, seem to be aimed at the same camera/lens combinations.  Is there a reason (optically speaking, not cost) to choose one over the other for different lenses?

One of the issues I think is the market is rather small.  I know Phil Rudin was of the opinion that the Zen 200mm was better for the 7mm micro43 lenses. 

The Zen/Nauticam 170/180mm domes are segments of larger radius domes and are generally compromises, I believe they are around 110mm radius of curvature.  One of the compromises is that the entrance pupil can't be placed at the centre of the radius of curvature if the lens is not to vignette as 110mm from the dome surface is down inside the extension and wide angle lenses tend to have the entrance pupil towards the front of the lens.   The impact of this varies with different lenses and is often less severe for lenses that are not in the ultra wide (weitwinkel) region (20mm or greater equivalent focal length). 

The Zen 200mm was the same radius of curvature as the 170mm dome which meant it was taller so the centre of radius of curvature was higher up in the extension and as it was taller the lens could be placed further back before it started to vignette - so optically it was better in this regard.

I think in general the bigger the sensor the more likely you are to have issues due compromises like these.  The 170/180mm domes are constructed that way to make the more compact for travel so in general you are weighing up optical quality vs travel convenience.

11 hours ago, Draq said:

Zen used to make a 200mm dome.  It is now discontinued and I wonder why. 

 

I suspect the reasons are not photographic. But more connected with the market, or perhaps even manufacturing reasons.

There is a good run through of domes here: 

https://wetpixel.com/articles/review-nauticam-wide-angle-corrector-port/P1

Alternatively there are many videos on Wetpixel Live about it:

https://www.youtube.com/playlist?list=PLtn70C5Bkm-a-xAyhwo3IXvqFnXYzVono 

Alex

Thanks, guys.  I have seen most or all of the Wetpixel dome/optic videos and have a general understanding of the issues about port size and extensions.  I guess I was mostly curious about what seemed to be those specific marketing oddities. 

10 hours ago, Draq said:

 I guess I was mostly curious about what seemed to be those specific marketing oddities. 

My guesstimate on the market forces is that the 200mm dome is a dome aimed directly at crop sensor users and these users have multiple choices of ports. Many use a 100mm mini dome with 10-17mm as their go to. If they fancy a bigger dome as well (many are content with the 100mm) they have lots of choices, only one of which is the 200mm. And many also go with a 230mm so that they can upgrade with it to full frame in the future and it is better for splits. 

Full frame SLR/mirrorless user who know what they are doing will get a 230mm and maybe a smaller dome too, but not a 200. And I am not sure you can use a 200mm on a M43 without an adaptor, I’ve never seen anyone using one. So the market for a 200mm is crop sensor folks only. And this part of the market is shrinking from what I see. As photographers fancy (rightly or wrongly) full frame SLRS (A D850 over a D500 or 5D over a 7D) or want to go Mirrorless, where the full frame products are far more enticing than crop sensor, and crop sensor mirrorless also looses out to folks downsizing to M43. 

So I think the 200mm dome suffers because Full Framers and M43ers don’t buy it. And Crop Sensor shooters have other options and crop sensor represent a shrinking part of the market anyway. 

36 minutes ago, Alex_Mustard said:

My guesstimate on the market forces is that the 200mm dome is a dome aimed directly at crop sensor users and these users have multiple choices of ports. Many use a 100mm mini dome with 10-17mm as their go to. If they fancy a bigger dome as well (many are content with the 100mm) they have lots of choices, only one of which is the 200mm. And many also go with a 230mm so that they can upgrade with it to full frame in the future and it is better for splits. 

Full frame SLR/mirrorless user who know what they are doing will get a 230mm and maybe a smaller dome too, but not a 200. And I am not sure you can use a 200mm on a M43 without an adaptor, I’ve never seen anyone using one. So the market for a 200mm is crop sensor folks only. And this part of the market is shrinking from what I see. As photographers fancy (rightly or wrongly) full frame SLRS (A D850 over a D500 or 5D over a 7D) or want to go Mirrorless, where the full frame products are far more enticing than crop sensor, and crop sensor mirrorless also looses out to folks downsizing to M43. 

So I think the 200mm dome suffers because Full Framers and M43ers don’t buy it. And Crop Sensor shooters have other options and crop sensor represent a shrinking part of the market anyway. 

 

I know that Phil Rudin has one and used it with the 7-14mm and he said the corners were noticeably better than the 170mm dome.  But I expect that benefit becomes significantly less as you zoom into 8 or 9mm, so it's a rather small market on m43 where it has a really noticeable benefit.  As I recall it was an N120 dome and would be adapted the same way the Nauticam 180mm is for m43 housings.

I don’t know if this is the correct part - but the price of the adaptor is not going to make this too attractive an option either:

https://www.backscatter.com/Nauticam-N85-to-N120-55mm-Port-Adaptor-with-Knob-f

54 minutes ago, Alex_Mustard said:

I don’t know if this is the correct part - but the price of the adaptor is not going to make this too attractive an option either:

https://www.backscatter.com/Nauticam-N85-to-N120-55mm-Port-Adaptor-with-Knob-f

That's one of them, there's at least 6 different lengths, some of them dedicated for tasks like using EF lenses on m43 or Sony  with adapters.  And yes they are pricey beasts!

I do not think that the price for extensions and/or adaptors is an obstacle for going the route of standard domeports plus required extension/adapter: the domeport versions with built-in extension for a certain lens are certainly cheaper at the first glance, but when one wants to use the domeport with another lens or even camera system, this is often not possible and one would have to acquire the same domeport with another built-in extension to use it...

I am happy that I acquired the Zen DP100, Zen DP170, Nauticam 140 domeports and zthe macroport 60 in the bare N120 versions. With extensions/adapters (some of them can be used for multiple configurations)  my wife and me are using Panasonic 7-14mm, Zuiko 8mm fisheye, Zuiko 12-40mm, Zuiko 9-18mm, Tokina 10-17mm fisheye, Canon 8-15mm fisheye and the Canon 100mm IS macro on our MFT cameras (EM1II and EM5II)...

(and even better: when we once acquire an additional FF system, we can continue to use these ports)

=> In case, at the time of acquisition, I would have known that the DP200 gives better IQ with WA compared to the DP170 (and if it would not have been discontinued), I certainly would have acquired the DP200 instead of DP170 (one can see too many "woulds")...

Wolfgang

14 minutes ago, ChrisRoss said:

That's one of them, there's at least 6 different lengths, some of them dedicated for tasks like using EF lenses on m43 or Sony  with adapters.  And yes they are pricey beasts!

Ouch - they sure are!