UW wide angle and domes

I'm not happy with the performance of my Tokina 12-24mm lens behind the recommended Ikelite dome. i've attached a crapy pic of the annoying distortion.

my conclusions so far are:

fx- Sigma 15mm fisheye as its sharper than the Nikon 16mm, not to sure on port size.

17-35mm with a single element +4 dioptre.

dx- 10-17mm Tokina, gives 180 degree to the equivalent 12mm of rectilinear lens. not to sure on port size.

12-24mm with a single element +4 dioptre.

the lens should be as far back in the dome before vignetting kicks in. when adding a dioptre should the port length increase??

has anyone used the Nikon 18-35mm lens, on fx, instead of the 17-35mm as it has more barrel distortion which should suit use behind a dome lens. i guess it should be used with a single element +4 dioptre. it's also far cheaper.

any pointers would be welcome, like brand of dioptres, dome size etc.

ta

i uploaded a picture, anyone know where it went?

For rectilinear lenses, you typically want a larger dome port. It's not so much the diameter of the port so much as the internal radius. With larger diameters, this means generally you have a larger internal radius. Not all 8" domes, for example, will have the same internal radius.

humm, must be all top secret info like alex says. so can anyone recommend an ikelite port for the tokina 10-17 fish?

I can't speak for Ikelite, but I routinely use my Tokina 10-17 behind a 6" dome and small extension on my housing with excelent results, I would recommend contacting Ikelite to see if they have any sugestions.

Lou,

On FX sensors the lower priced Nikon 18-35mm ED lens might be great. I used it on my Nikon film cameras and first dSLR, the Nikon D100, with nice results. In Ikelite ports the proper extended 6" (this lens NEEDS a +4 diopter to focus underwater) will yield good results, but the 8" dome will be even better on FX or DX sensor cameras.

If you stay in the DX camp and use the Tokina 10-17mm the Ikelite 6" works fine once you zoom to 11 - 12mm or so right on down to 17mm. It is sharpest in those ranges IMHO. If you zoom to 10mm with the 6" port either take the shade off it or resign yourself to a mild crop in post processing.

The Ikelite 8" dome port with shortest extension yield better corners with the Tokina 10-17mm Fisheye lens, even at 10mm than the 6" port. Plus you absolutely NEED an 8" dome to shoot over / under images. The 6" won't cut it....

Hope this helps!

dhaas

fx- Sigma 15mm fisheye as its sharper than the Nikon 16mm, not to sure on port size.

I would not worry too much about this one. The difference is small and both are easy to get to work behind domes. I favour the Sigma 15mm because it has much closer focus and is a newer design. But both are good, sharp lenses that work well behind most domes wide enough to accommodate them. The Sigma is also cheaper!

dx- 10-17mm Tokina, gives 180 degree to the equivalent 12mm of rectilinear lens. not to sure on port size.

 

12-24mm with a single element +4 dioptre.

 

the lens should be as far back in the dome before vignetting kicks in. when adding a dioptre should the port length increase??

The 10-17mm is a decent lens. Not great on land, but most UW subjects don't tend to show its CA. Most find it works best with a small extension ring behind a typical fisheye port.

Alex

I think that there is a great deal of confusion over domes because of some mis-information that propagated through the uw photo community about them, gosh, it must be about 10 years ago now.

The problems are rarely with the domes. Nearly all the major manufacturer's have good domes. The problem is always how people set them up to use them.

Alex

excellent, thanks guys defiantly loads to mull over.

if an extension ring (smallest kenko?) is used on the 10-17 i guess you loose infinity focus so forget the 8'' for over under shots, which i have probably shot... 2.

Sorry. I meant port extension ring.

Alex

excellent, thanks guys defiantly loads to mull over.

 

if an extension ring (smallest kenko?) is used on the 10-17 i guess you loose infinity focus so forget the 8'' for over under shots, which i have probably shot... 2.

When used in underwater photography, the extension ring is usually a manufacturer made ring installed between the port and the housing to properly locate the optical center of the dome and the lens as oposed to top side photography where the extension (kenko, etc.) is inserted between the lens and the body to allow closer focusing (macro).

fair enough. just getting the nodal point right.

i uploaded a picture, anyone know where it went?

Lou , just guessing, you might have "uploaded" the photo but not "attached" it using the box above the upload box in the attachment editor. One needs to do both. Hope you find it.

Steve