New vs Old Aquatica 8" Acrylic Dome Vingette

[timbriggsphoto]

I'm building up my gear around a Nikon z7ii in an Aquatica housing and was hoping to use my older 8" Acrylic dome from my prior A7rii Aquatica setup but I'm getting some vingette at the widest end of my Nikon 14-30 f4, I can see both the dome shade and I think part of the inside of the dome in photos. I'm using the suggested extension tube (48457/18457) for the 8" dome port, but the port recommended in the z7ii lens chart is the #18414, mine is (I believe) the older 18405 which appears to be slightly different? Has anyone else run into this problem? Would prefer to not drop over $800 on a new dome... Leaving on a trip in about a month and want to get this figured out before then... 

[Chris Ross]

4 hours ago, timbriggsphoto said:

I'm building up my gear around a Nikon z7ii in an Aquatica housing and was hoping to use my older 8" Acrylic dome from my prior A7rii Aquatica setup but I'm getting some vingette at the widest end of my Nikon 14-30 f4, I can see both the dome shade and I think part of the inside of the dome in photos. I'm using the suggested extension tube (48457/18457) for the 8" dome port, but the port recommended in the z7ii lens chart is the #18414, mine is (I believe) the older 18405 which appears to be slightly different? Has anyone else run into this problem? Would prefer to not drop over $800 on a new dome... Leaving on a trip in about a month and want to get this figured out before then... 

First of all I assume the dome shade is square and properly oriented.  Does your port seem to have any built in extension compared to the current 18414, which from photos seems to have none?  Is the front element sitting well down inside the extension?

 

You shouldn't need a new dome, just different extensions, if you are vignetting you need less extension.  Your current extension is the 54.5mm  The next smaller size is the the 39.5mm 48462, which is 15mm shorter.  You can combine a 16.5 and 28.5 mm for 45mm as well. 

 

You could estimate how much extension is required if you setup your camera and the port (no housing)  in the same position inside the extension as it is when in the housing.  support the port/extension tube upright and place the camera on some books or similar so it is centred in the extenion and adjust it to get the same vignette.  You could measure the distance from housing to camera flange to help you position the camera.

 

Then slide the camera forward until the vignette is longer seen.  Measure how much you moved the camera and that is how much less extension you need.  Use the next smallest extension combination to what you just measured.

[timbriggsphoto]

20 hours ago, Chris Ross said:

First of all I assume the dome shade is square and properly oriented.  Does your port seem to have any built in extension compared to the current 18414, which from photos seems to have none?  Is the front element sitting well down inside the extension?

 

You shouldn't need a new dome, just different extensions, if you are vignetting you need less extension.  Your current extension is the 54.5mm  The next smaller size is the the 39.5mm 48462, which is 15mm shorter.  You can combine a 16.5 and 28.5 mm for 45mm as well. 

 

You could estimate how much extension is required if you setup your camera and the port (no housing)  in the same position inside the extension as it is when in the housing.  support the port/extension tube upright and place the camera on some books or similar so it is centred in the extenion and adjust it to get the same vignette.  You could measure the distance from housing to camera flange to help you position the camera.

 

Then slide the camera forward until the vignette is longer seen.  Measure how much you moved the camera and that is how much less extension you need.  Use the next smallest extension combination to what you just measured.

 

Thanks for the help!

 

The dome is properly oriented and I'm actually seeing vignetting not just from the shade but from the interior of the dome itself, I think.

 

I can't really tell if there is built in extension, but I'll do some of these tests later. I have also heard from Aquatica that "Our older 8 inch acrylic dome(18405) is the same as our current 8 inch glass port (18408),so looks like our extension ring 48461 will be the one for you." but they're going to confirm this for me. Hopefully will get away without spending extra on a new dome!

 

In the same interest of saving a little money, I'm curious if I'd be able to get away with the 48461 extension tube with the 105mm Z macro lens and the mini macro port – the recommended port extension is the 48462 but I can't find any measurement for the 48461 and it is not listed on the external dimensions chart on Aquatica's site, too new I guess? My understanding is that flat ports are less critical in their relative position to a lens as long as they're not vignetting or physically touching? If not I might just grab a 50mm macro and call it a day! No extension required...

[Chris Ross]

You won't need a new dome, just the right extension.  looking at the charts for the 18414 and 18408, the glass 18408 needs about 10mm less than the acrylic 18414 so I would guess it's going to be in the range of 45mm in length +/- a few mm.  It's rather annoying they go by part numbers, every other supplier just calls it an xx mm extension ring and the part numbers are in random rather than increasing size order.

 

Regarding the macro port, you will want the right length extension, the 48462 is 39.5mm so the 48461 is likely to be about 6-8mm longer than that.  The lens will probably fit but diopters won't work as well if the lens is further away and you lose a touch of working distance depending on how tightly the 48462 extension fits. If you don't use diopters it would probably be fine as you would have about 135mm working distance at 1:1 with 105mm Z lens.