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Knightpics

Aquatica port question

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Hi guys

I have the Aquatica A5DSR housing with the #48463 port extension for the canon 8-15 fish eye behind the 8” acrylic dome

I’d like to put the sigma art 14mm f1.8 DG HSM lens in the housing and I’m wondering if I can use this same port extension or no port extension or if it needs one a different size ?

Haven’t heard back from Aquatica yet and wondered if anyone has used this setup and knows the answer ?

 

 

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Aquatica don't list the lens on their port charts, but you can get an indication from other port charts - for example on the same port Nauticam list 30mm extension for the 8-15mm and 70mm for the 14mm f1.8.  This indicates you need 40mm more extension for the 14mm lens vs the 8-15mm lens.  So in your case you would add 40mm extension which would be one 48462 (39.5mm) extension, so that would be one 48462 and one 48463

This is an indication only and you would need to test it , but I think it would get you quite close to what is needed.

Of course a bigger dome as Adam suggests would be ideal  - an 8"dome is a little small for a 14mm rectilinear.   It doesn't take filters so the S&S corrector is not an option either.

 

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My guess with the 14mm is that you will need a bigger dome...
Adam
 

Why is that if it already works with the 8-15?


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Aquatica don't list the lens on their port charts, but you can get an indication from other port charts - for example on the same port Nauticam list 30mm extension for the 8-15mm and 70mm for the 14mm f1.8.  This indicates you need 40mm more extension for the 14mm lens vs the 8-15mm lens.  So in your case you would add 40mm extension which would be one 48462 (39.5mm) extension, so that would be one 48462 and one 48463
This is an indication only and you would need to test it , but I think it would get you quite close to what is needed.
Of course a bigger dome as Adam suggests would be ideal  - an 8"dome is a little small for a 14mm rectilinear.   It doesn't take filters so the S&S corrector is not an option either.
 

Ahh I see. Is that because this is classed as a rectilinear rather than a fish eye ?


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Yes, and you have a very high resolution camera that will show all the optical flaws really well! Getting the correct amount of extension is actually as important as dome size. If the lens is incorrectly positioned, this will affect image quality too. 

I would have a search around on the forum about rectilinear lenses and domes-there is a huge amount of info.

In addition, it is worth mentioning that some rectilinear lenses simply do not work behind domes...probably because close focus is not really a design feature for this type of lens. Unless someone else has tried it, it is impossible to know!

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13 hours ago, Knightpics said:


Ahh I see. Is that because this is classed as a rectilinear rather than a fish eye ?


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Yes rectilinear lenses are much more demanding - the curved virtual image does not fall within the depth of field available and the corners end up soft.   The virtual image for an object at infinity is 3 dome radii away from the dome so very close.  Fisheyes don't have that problem as they are designed to render an  curved image onto the sensor.  Nauticam list that lens and they recommend the 230mm dome - which means in that dome and also  the 8.5"dome they also list it works - but that doesn't mean it works "well" .    You might ask in a new post if anyone is using the lens (on any camera) and what they think of it and if they can share samples. The results are translatable to your system with the same dome size (assuming proper placement). 

It's probably simpler to pick a lens that is already listed on the charts and maybe not quite so wide, depending upon what you plan to shoot with it.  Generally a 16mm lens requires a 230mm dome and a lot of people use the S&S correction lens with that combo to get good corners.  If you are shooting big animals in blue water where the corners are not so important, you might find a smaller dome satisfactory with a lens of this class.

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