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Tips to avoid blurry edges ?

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On 12/10/2021 at 12:24 AM, ido said:

And this is what Isotta suggested just now:

 

Hi Ido,

if you want to stay with the 4,5” port you can add an 20 mm extension ring (with this you should reduce the blurry edges)

The disadvantage is that if you want to do macro/wide you will find yourself further away from the subject so you will have less macro effect

  

I would certainly try the 20mm extension before you buy a new dome.  It's a bit of a no regrets purchase as you would need the 20mm extension for a 6.5"dome.  That together with stopping down some more might be enough??

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Thanks. I will try it as well

 

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@shakuiel

Hi,

Sadly the answer is yes! It should work well for CFWA, but will be limited for reefscapes. Let me know how you get on with the Kenko converter...

The short answer with any port is that the bigger the port, the better the corners. The bigger the sensor (and arguably the higher its resolution) the more pronounced this is.

Yes, you can stop up, but this will inevitably result in compromises in exposure settings. 

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I'll borrow this thread for a while. I use Nikon Z6/7 in a Sea & Sea housing. I also have the Nikon 8-15 fisheye, used on FTZ adapter of course. Furthermore I have the Zen 230 mm dome and a 40 mm extension. In a thread here last autumn we reached the conclusion that I should probably use a 20 mm extension with the fisheye and the 230 mm dome (so that's not the question here).

Before hitting the purchase button I thought I'd see if there are other alternatives that may be better. Specifically, Sea & Sea makes the Optical Dome Port ll 100 L (link) which is "Designed exclusively for (...) Nikon AF-S Fisheye Nikkor 8-15mm F3.5-4.5 E ED".

While more expensive than buying just an extension ring this would be a more nimble solution in close quarters. But... is there any reason to believe that this is optically anything special, or is the "designed exclusively" limited to extension length?

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I believe the “exclusive” bit is just the built in extension. Saga do the same thing.

then there is the whole mini dome / big dome debate.

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8 hours ago, horvendile said:

I'll borrow this thread for a while. I use Nikon Z6/7 in a Sea & Sea housing. I also have the Nikon 8-15 fisheye, used on FTZ adapter of course. Furthermore I have the Zen 230 mm dome and a 40 mm extension. In a thread here last autumn we reached the conclusion that I should probably use a 20 mm extension with the fisheye and the 230 mm dome (so that's not the question here).

Before hitting the purchase button I thought I'd see if there are other alternatives that may be better. Specifically, Sea & Sea makes the Optical Dome Port ll 100 L (link) which is "Designed exclusively for (...) Nikon AF-S Fisheye Nikkor 8-15mm F3.5-4.5 E ED".

While more expensive than buying just an extension ring this would be a more nimble solution in close quarters. But... is there any reason to believe that this is optically anything special, or is the "designed exclusively" limited to extension length?

It will just be the extension, it's a trade off of corner quality for the ability to get in close.  A 230mm dome will make it hard to do any sort of CFWA.

 

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Thanks both of you. Yeah, I guess I will have to choose between good edges (€300) and CFWA (€1000). Right now it will probably be the former, if not else for economic reasons.

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14 hours ago, horvendile said:

Thanks both of you. Yeah, I guess I will have to choose between good edges (€300) and CFWA (€1000). Right now it will probably be the former, if not else for economic reasons.

Your other option would be a Nauticam 140mm dome as a more all round solution, you can just change the bayonet ring to a Sea & Sea one to use on your housing.

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14 hours ago, ChrisRoss said:

Your other option would be a Nauticam 140mm dome as a more all round solution, you can just change the bayonet ring to a Sea & Sea one to use on your housing.

Another option is what I did (and not tested yet):

Isotta 6.5 dome with 20cm extension (It should be compatible with Sea&Sea)

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Late reply, sorry.

There's also the Sea&Sea native 165 mm port. Speaking of changing bayonet ring though, is that something which works as a general solution? Suppose that I would want eg the Nauticam WACP or MWL-1. Are those possible to adapt for Sea&Sea use?

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4 hours ago, horvendile said:

Late reply, sorry.

There's also the Sea&Sea native 165 mm port. Speaking of changing bayonet ring though, is that something which works as a general solution? Suppose that I would want eg the Nauticam WACP or MWL-1. Are those possible to adapt for Sea&Sea use?

Yes, any Nauticam port with a removable bayonet ring, you can replace it with a S&S bayonet ring (in N120 size).  The MWL-1 is different though it attaches to a flat port, though of course if the Nauticam flat port used a removable bayonet ring you could use that port on S&S.

 

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On 12/11/2021 at 4:03 AM, adamhanlon said:

@shakuiel

Hi,

Sadly the answer is yes! It should work well for CFWA, but will be limited for reefscapes. Let me know how you get on with the Kenko converter...

The short answer with any port is that the bigger the port, the better the corners. The bigger the sensor (and arguably the higher its resolution) the more pronounced this is.

Yes, you can stop up, but this will inevitably result in compromises in exposure settings. 

Just did my first two days of diving with my 4" minidome and 8-15mm fisheye on the Canon R5. Buying a bigger dome ASAP, corners are MUSH. I saw an old post of you recommending a 180mm glass, does that still stand true?

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22 hours ago, shakuiel said:

Just did my first two days of diving with my 4" minidome and 8-15mm fisheye on the Canon R5. Buying a bigger dome ASAP, corners are MUSH. I saw an old post of you recommending a 180mm glass, does that still stand true?

The recommendation will depend a little on which housing system you are using as dome sizes vary a little among vendors.  You should also confirm you are using the recommended extension and are stopping down enough all of which will make some difference, I ask as while corners may be bad with 4"domes and a fisheye on full frame, MUSH sounds like the potential for other issues compounding the problem.

 

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26 minutes ago, ChrisRoss said:

The recommendation will depend a little on which housing system you are using as dome sizes vary a little among vendors.  You should also confirm you are using the recommended extension and are stopping down enough all of which will make some difference, I ask as while corners may be bad with 4"domes and a fisheye on full frame, MUSH sounds like the potential for other issues compounding the problem.

 

Mush is probably dramatic, I have been shooting wide angle for like two days so I don't really know much difference from bad to extreme. Spoke with Kevin from ReefPhoto and send him some sample pictures and I'm gonna upgrade to the 140mm dome. I was using the right extension (no extension) and was at F11 with the issues

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1 hour ago, shakuiel said:

Mush is probably dramatic, I have been shooting wide angle for like two days so I don't really know much difference from bad to extreme. Spoke with Kevin from ReefPhoto and send him some sample pictures and I'm gonna upgrade to the 140mm dome. I was using the right extension (no extension) and was at F11 with the issues

sounds like you are on Nauticam, the 140mm dome is Nauticam's recommendation as most optimised for the 8-15mm and uses a 30mm extension.  Sounds like you were on the Zen 4"dome with the extension built in.

I found when I first started using fisheye lenses I need to watch out for parts of reef that were much closer than the subject so were on the edge of the depth of field available - most pronounced on wall dives It's not always immediately obvious when first looking at the photos until I looked closely at one where the LHS of frame was very close and it also had reef detail in the opposite corner that was much sharper. 

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Nauticam also sells acrylic 8.5'' dome which you may also find very useful for reef scenes. It may not be as good for CFWA, but corners with this dome are pretty good. And what's best - it's about 30% cheaper than the 140mm dome.

I use both: 140mm glass dome for fisheye, and 8.5'' acrylic for 10-24mm rectilinear lens. I know it's not really directly comparable, but corners seem much better with the big dome and rectilinear lens with the aperture set to f8, than with the 140mm dome and fisheye lens with the aperture set to f11-16.

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I would go for a 170mm port with a full frame high resolution camera and the 8-15mm. It provides an acceptable compromise between corner sharpness and physical size. 

Port charts are not really useful in this instance, as they do not differentiate on your intended use. As we have previously discussed, you can use smaller domes with fisheye lenses for CFWA/WAM and the port charts note this. However, this doesn't make them optimum for reef scenics. 

Given that you already have the 100mm for CFWA, buying a bigger dome for scenics makes sense.

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2 hours ago, adamhanlon said:

I would go for a 170mm port with a full frame high resolution camera and the 8-15mm. It provides an acceptable compromise between corner sharpness and physical size. 

Port charts are not really useful in this instance, as they do not differentiate on your intended use. As we have previously discussed, you can use smaller domes with fisheye lenses for CFWA/WAM and the port charts note this. However, this doesn't make them optimum for reef scenics. 

Given that you already have the 100mm for CFWA, buying a bigger dome for scenics makes sense.

There isn't a 170mm dome in the Nauticam system and you would adapting a third party dome.  The 170mm ZEN sounds attractive but it's not a hemisphere so you need to place the entrance pupil well forward of the optimal position to prevent it vignetting, same goes for the Nauticam 180mm dome.  

You could adapt an Isotta or Sea and Sea 6"/6.5"dome assuming they have removable lug rings to allow you to use this item to adapt to Nauticam: https://www.bluewaterphotostore.com/nauticam-port-adapter-sea-sea  That gives you a 150/165mm dome.

 

 

 

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Good point...I use the ZEN 170mm or Seacam CP port. My 8-15mm is almost always at 15mm so vignetting is not an issue (although this is a creative decision rather than a practical one!)

 

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36 minutes ago, adamhanlon said:

Good point...I use the ZEN 170mm or Seacam CP port. My 8-15mm is almost always at 15mm so vignetting is not an issue (although this is a creative decision rather than a practical one!)

 

The Seacam CP port looks to be a 180° hemisphere so would be fine . 

I have the 170mm Zen dome and the centre of radius of curvature is about 65mm below the dome base and well into the extension.  So the entrance pupil of any fisheye lens used with it at least 50 or 60mm forward of the optimal position - most fisheyes the entrance pupil is right up front on the lens.  The lens won't vignette but is also won't perform as well as it would if the entrance pupil was at the centre of the radius of curvature of the dome.

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Hi guys

 

I just had 2 days of diving with a 6.5 inch dome and 20 cm extension (in addition to the 30 cm zoom extension) and I sill has blurry edges in f11. is this the best I can get from this dome ? (I started with 4.5 inch dome)

I am using Nikon Z72, Nikon 8-15, Isotta housing.

Thanks

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This looks too blurry for me, try to test lens at home with all f spots to understand its sweet point.

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The edges look stretched. Did you apply distortion correction in post (aka defishing)? If so that's at least part of the problem.

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27 minutes ago, Isaac Szabo said:

The edges look stretched. Did you apply distortion correction in post (aka defishing)? If so that's at least part of the problem.

I use lightroom. I set the calibration to my lens. What do you mean by  "defusing" ?

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4 minutes ago, ido said:

I use lightroom. I set the calibration to my lens. What do you mean by  "defusing" ?

A fisheye lens has strong barrel distortion. It sounds like you have enabled a distortion correction in Lightroom that is removing the barrel distortion by stretching out the edges of the image (removing the barrel distortion from a fisheye image is also called defishing). The distortion correction is degrading edge sharpness and reducing field of view. You should turn off the distortion correction/lens calibration in Lightroom. 

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