ClairevL

And I guess the Marumi filters in the set will indeed be single element. Marumi has the "achromat" filters as well, but as far as I know not in sets of 3. You'd probably also feel the difference, since the dual-element filters are quite a bit heavier. But I didn't find any dual-element filters that didn't give vignetting; they are fairly thick compared to their single-element counterparts.

I redid my tests this weekend and I can live with the results I got at f8 (and f11 is actually pretty good). I can't access the photos now, so I'll post them later. I could also see there's a sweet spot in the zoom range. At 12 mm the results are still not great. In the end I decided to keep the Hoya HMC +2 filter, which in my case seemed slightly better than the B&W +2 (but the difference was really tiny). There was still quite a difference between with and without filter, so I'll have to live with the loss in angle of view and infinite focus. Pete, thanks for your advice! Cropping would also work indeed, but I think in some cases just zooming in in stead of cropping also does the job. Tim, the 9" dome will still be a better solution! But this one was a cheaper solution:-)

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.

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.

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?

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;-)

with the Canon 500D: 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.

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: Here, the result with the B&W +2: the B&W +3: the Hoya +1: the Hoya +2: and I'll have to put the result for the Canon 500D in the next post.

And, just to check, I assume you have the single element Marumi filter, right? I know Marumi also has the achromat filters, but currently they are not available in +2.

Hi Tim, Thanks for your reply! I'm really excited about learning new things from this community! Does the Marumi give you sharp corners? And do you use it with an 8 inch dome as well? Do you see any vignetting at 12 mm? I should look more into post processing! That's also a topic I hope to learn more about here.

I just bought a nikkor 12-24mm, which I want to use in my Ikelite housing with 8" dome. I'm a little worried about soft corners, so I wanted to buy a +2 diopter. However, I'm not quite sure which one to buy. A 2-element +2 close up lens that suits a 12-24mm lens doesn't seem to exist. So, I'll probably suffer from chromatic aberrations. I was considering the B&W or Hoya, but couldn't actually find which one would be better? A camera shop told me the BW would be better due to a coating that reduces CA, but I wouldn't know of any coatings that could do that...thought there would only be an (hydrophobic) AR coating on the BW filter. Could anyone please advise me what filter I should buy? Any advise will be higly appreciated! Thanks!

Hello, My name is Claire and I own a Nikon D7000 with Ikelite housing. I'm familiar with optics (I'm a physicist), but I'm quite new to underwater photography. I look forward to learn more about uw photography, particularly shooting large pelagics and wide angle.