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ClairevL

finding the right close up lens for Nikkor 12-24mm in Ikelite 18 inch dome - my test results - please help!

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Hi all,

 

For my Nikon D7000 in Ikelite housing I have so far used a Tokina 10-17mm fish eye lens. I recently bought a Nikkor 12-24 mm to also capture skittish pelagics. However, I have problems getting sharp corners when using this lens in combination with my 18" dome port. To summarize, I can neither get sharp corners without any close-up lens, nor with any of the close-up lenses I tried (B&W +2, B&W + 3, Hoya HMC +1 and +2, Canon 500D). Vignetting was significant for the Canon and Hoya filters. For now, I will not even consider chromatic aberrations; I simply cannot even get sharp pictures. Now, I actually don't know how to solve this problem.

 

To test, I took some pictures in my bath tub, without filter and with all the filters mentioned above. For all cases I took photos at 12mm, 18mm, and 24 mm. Please find the 12mm results below.

 

This is without the filter:

post-53726-0-37962300-1457272203_thumb.jpg

Here, the result with the B&W +2:
post-53726-0-82644800-1457272492_thumb.jpg
the B&W +3:
post-53726-0-89888200-1457272718_thumb.jpg

 

the Hoya +1:

post-53726-0-75855500-1457273260_thumb.jpg

 

the Hoya +2:

post-53726-0-91020400-1457273289_thumb.jpg

 

and I'll have to put the result for the Canon 500D in the next post.

Edited by ClairevL

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with the Canon 500D:

post-53726-0-09522700-1457273661_thumb.jpg

 

As you can see, none of them give very sharp corners. In my opinion, the B&W +2 gives the best overall result. Some of the other filters also result in curvature near the corners, and the Canon filter shows serious vignetting (although the Hoya filters are also pretty bad in terms of vignetting at 12mm).

I really hope someone can advise me how to improve my corner sharpness. Thanks very much in advance!

 

Just as a side note, when I compared the AR coatings of the B&W +2 and HOYA HMC +2, the Hoya seemed quite a bit less reflective. I didn't measure any reflection spectrum though.

Edited by ClairevL

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18", Claire? That's massive. 8"??

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Hi Tim,

 

Sorry you're absolutely right. That was a typo. I have the 8" dome; with an 18" port I'd probably not have any of these problems;-)

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With an 18" incher, Claire, you might get the world's sharpest underwater pics :crazy:

 

Hmmm, odd. Have you checked with Ikelite what they recommend by way of domeport/EXR/diopter for the Nikkor 12-24?

 

And then you've got the lens stopped down to what? f8? f11?

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I asked Ikelite before and they advised me to try a +2 close-up filter; they recommended to try Hoya, B&W or Tiffen. I just sent them another email after doing this test.

With this test I opened my aperture all the way up to F4; light conditions were not great, and using my bulky strobes in the bath tub makes everything a little harder. And I also want to be able to photograph sharks without strobes if they're just a bit too far away (would be F5.6 or so then probably). Do you think it's a good idea to redo my test with F8?

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Hi Bill,

Thanks for the information about your hemispherical domes! They sounds like a good solution. However, if possible, I'll first try to go for a solution with the dome I already have. I just bought a new lens and dome extension, so I should actually not spend money on another dome port now.

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Hi Claire

 

Definitely try stopping the lens down. F8 or, more likely, F11. Fingers crossed!

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Indeed, fingers crossed. I guess I should be satisfied if I get reasonably sharp pictures with F8. Still a pity though, because if the sharks are too far away I can't use my strobes and will have to open up the aperture a bit more.

I will have to wait till Saturday to do my new test; can't make it home by daylight on weekdays. But I will post the results on the weekend.

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You are probably not going to like my answer and I don't mean to sound rude but.... I bought that lens more than 10 years ago (and still have it) but (mostly) stopped using it underwater within a few dives after owning it. I also hated the nasty corners that it gave me. I too tried using diopters to improve the corners on reef shots, but, then was limited to a certain distance when trying to take photos of sharks.. with a +2 on it I could no longer focus on a shark 6 feet away!

However.... there is one instance when I still use it from time to time: when I want to shoot a shy pelagic such as a Mola mola which will not allow me to get close to it. The key thing is the word "pelagic" which is what you state is what you want to shoot. Why is this important? Because with most pelagics you will be shooting the fish/mammal against a blue water background and in such a situation the corners won't matter. This is much different than trying to shoot a CFWA of an anemone or soft coral, soft corners won't matter.

 

Therefore, feel free to use this lens when shooting subjects which are swimming in the blue and do not use a diopter for that (or you won't be able to focus very far away from your port) However, don't try to take reef scenics on the same dive as you will be sorely disappointed with the corner results (although f11-f22 will help)

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