Aquatica Recommended Port Extensions for WA, are they correct?

Just wondering if anyone has a good explanation why Aquatica recommends the #18463 extension for use with the Nikon 12-24Dx? According to my calculations the mean radius of Aquatica's 8" dome is 10.6cm (give or take a couple of mm) which places the center at approximately 3.55cm behind the dome's backplate. Taking into account that the 12-24Dx entrance pupil is +-11.25cm (at inf. and 12mm FL) in front of the filmplane and the fact that with the camera and lens installed in a D200 housing, the front of the housing is 3cm behind the 12-24Dx entrance pupil (at 12mm), the required extension should be something around (3cm+3.55cm)=6.55cm which is far, very far from the extension recommended by Aquatica (#18463)!

2nd question: Has anyone measured the radius of the new 9.25" Megadome from Aquatica? Is it the same radius as the 8", just bigger or does it have a different radius altogether? <_<

Hi Giftie,

Not sure if things have changed, but I did testing for Aquatica when the 12-24 first came out and recommended 15mm of extension (I tested from 0 to 55mm) for shooting the lens at 12mm. If your calculations show a different result I'd be interested to see some photos taken at 12mm with the 65mm of extension.

Cheers

James

Just to let you know that the pool has recently defrosted and is now being cleaned, then I will spend mucho time reevaluating and confirming as many lens as I can get my hands on. (for both Nikon & Canon)

While most of the current extension ring / lens suggestion appear spot on, a few might needs to be redone in light of the new data that we are getting from our newly aquired optical center determinator widget.

So far on paper I get different result than both James and Jorge, but will test your's along with our current and the new "on paper still" recommendation that I got from the optical widget.

One thing for sure I going to borrow a Nikon 12-24 and definetly start with that one and keep you guy's posted.

Regards

4.55" radius. I'm waiting for the final flange design to go ahead with final measurement, but if there is any variant (should'nt be) they will be minimal and academic.

Just to let you know that the pool has recently defrosted and is now being cleaned, then I will spend mucho time reevaluating and confirming as many lens as I can get my hands on. (for both Nikon & Canon)

 

While most of the current extension ring / lens suggestion appear spot on, a few might needs to be redone in light of the new data that we are getting from our newly aquired optical center determinator widget.

 

So far on paper I get different result than both James and Jorge, but will test your's along with our current and the new "on paper still" recommendation that I got from the optical widget.

 

One thing for sure I going to borrow a Nikon 12-24 and definetly start with that one and keep you guy's posted.

 

Regards

...this what is great in Wetpixel, the industry guys are just around the corner .

In reply to James I did took some pictures using the 12-24 at 12mm with the #18457 and the #18463. I prefer not to post them since they were done in the bathtub (yep, the pool of the poor) with a (use once)checkerboard target and I did not manage to get shots that could be compared directly. For what is worth the #18457 seemed to give better results (just better, not perfect) at f4, but like I said not conclusive, have to repeat <_< .

By the way Jean can you tell us the average radius of the 8" dome and thickness?

Do let us know your results.

cheers,