Ikelite D80 housing/Tokina 12-24mm lens w/6" dia port, is a diopter req'd?

I am thinking using the Ikelite D80 housing and the 6" diameter dome port with my Nikon D80 w/Tokina's 12-24mm lens. The Ikelite web site says "adding a + diopter close-up to the lens is NOT required, but some people feel a +2 close-up lens may enhance corner sharpness".

Does anyone have experience using diopters with this Tokina lens? Do I need a diopter?

Thanks,

I am thinking using the Ikelite D80 housing and dome port with my Nikon D80 w/Tokina's 12-24mm lens. The Ikelite web site says "adding a + diopter close-up to the lens is NOT required, but some people feel a +2 close-up lens may enhance corner sharpness".

Does anyone have experience using diopters with this Tokina lens? Do I need a diopter?

Thanks,

For anything that doesnt require the dome port to be close to the subject this lens is great!

If you want to shoot anthing that is close to the dome port you will want a Diopter.. I have a +2 diopter and am thinking I might try a +4 as when I shoot anything that is close to the dome the sharpness on anything outside of the center of the image falls off rapidly...

If the +4 diopter works to correct this (the +2 didnt help to much) then ill be happy. If it doesnt then Im going to be pissed as that will be almost $200 I have spent on diopters I didnt need. It will be another couple of weeks before I can get a +4, when i do Ill post the results.

For anything that doesnt require the dome port to be close to the subject this lens is great!

For anything that doesnt require the dome port to be close to the subject this lens is great!

 

If you want to shoot anthing that is close to the dome port you will want a Diopter.. I have a +2 diopter and am thinking I might try a +4 as when I shoot anything that is close to the dome the sharpness on anything outside of the center of the image falls off rapidly...

 

If the +4 diopter works to correct this (the +2 didnt help to much) then ill be happy. If it doesnt then Im going to be pissed as that will be almost $200 I have spent on diopters I didnt need. It will be another couple of weeks before I can get a +4, when i do Ill post the results.

 

For anything that doesnt require the dome port to be close to the subject this lens is great!

Thanks for the reply..

Does the +2 diopter fit ok within the dome port or did you need an extension of some kind?

Regards,

The problem could be that the front element of the lens is forward of the nodal point of the dome (meaning: the lens sticks too far into the dome). That would cause the out of focus corners.

That's why James is asking about which port extension you're using.

(The 12-24 is longer than most prime lenses that don't require a port extension.)

Take Care,

ChrisS

I have the recomended port extension from Ikelite the #5510.16

Phil

Doing some fast lookups at BH for lens lengths:

Tokina 12-24mm zoom = 90mm

Nikon 20mm prime = 43mm

Lens Length Delta = 47mm

Looking at Ikelite's site for port extension lengths:

#5510.10 .... 1.300" (3.302cm)

#5510.16 .... 2.047" (5.200cm)

Port Extension Delta = 19mm

(meaning the lens _could_ be sticking too far into the dome by 28mm;

I don't know how Ikelite dome extensions work, I just going off how port extensions work with my Aquatica housing: most primes don't require an extension, zooms and longer primes do require an extension)

With my Aquatica, the front element of the lens is basically even with the front of the dome base. What does the tokina 12-24mm look like when in your Ikelite dome?

Take Care,

ChrisS

I'm also interested in getting one of these lenses and so have done a little bit of research.

Not only do Ikelite recommend the 5510.16 port extender here, the dimensions on the 8" port page would also recommend the 5510.16 port extender.

Tokina specifications say the lens is 89.9mm (3.5") long. I believe this would be including the lens mount, but even if it doesn't, that is still within the recommendations by Ikelite: #5510.16 .... Lenses up to 3.500". Perhaps if you measure the lens from the camera to the end at its longest length.

I suspect what may really be happening is the subject is just too close for the lens.

A dome port creates an apparent image which is much closer than the subject. The example Ikelite give for the 6" dome ports is an apparent image at 12" for a fish that is 3 feet away. The 12-24mm lens has a minimum focusing distance of 11.8" which means it would be able to focus on the apparent image - but that was for a fish that was 3 feet away. How close will it need to focus for something that is 12" away?

With 6" dome ports I have found that you need at least a +4 diopter to get the same magnification behind the dome port that you would get from the raw lens on land.

Here's a full frame image from my 18-55mm @55m at its closest on land:

Here's a shot underwater with the same lens @55mm with a +4 behind the dome port:

If you are using a +2, you will not be able to get as close as you can on land.

I recommend trying the +4, although I suspect you may still have issues when you are two close.

Has anyone tried the 12-24mm behind a 6" port? Will it work? Will you get vignetting?

I have an Tokina 12-24, but I have always used it with the +2 diopter, so I can't really compare with and without.

Its nearly new (only a couple of dives) and I will sell it for a reasonable price. I'm going to move on to a 10-17. PM me if you're interested. US warranty with all packaging. Brand new condition.

David

Has anyone tried the 12-24mm behind a 6" port? Will it work? Will you get vignetting?

Subal recommends a +4 dioptre with lenses in this focal length range behind this dome port (Subal don't give a recommendations for Tokina lenses but do give recommendations for Canon and Sigma lenses) and this is what I used.

These whaleshark shots:

Whaleshark Shots

And the wide shots taken on this page of my Coco (Keeling) Islands gallery:

Cocos (Keeling) Wide Shots

Were all taken with the Subal 6" dome port and +4 dioptre.

Thanks Ross (or is it Mary). Those shots are excellent and exactly the sort of thing I want to achieve.

Thanks Ross (or is it Mary). Those shots are excellent and exactly the sort of thing I want to achieve.