Nexus D100 & Nikon 12-24

Is anyone sucessfully using the Nexus D100 housing with the Nikon 12-24mm lens. I have tried mine with a 50mm extension and a 170 dome port and also with a 40mm extension and the 170 dome port. The center of the photo is sharp and it gets softer as you get to the edges. I have read threads about 8" ports helping with the edge softness. I would consider the Nexus 230 port if it had a lens shade. I do a lot of diving in New Jersey and the lens shade helps to protect the dome.

I would like to hear anyone else's experience with this housing and lens. Thanks.

Herb,

Can you post an example photo that shows what you are talking about? I'd like to see how severe the drop-off in sharpness is.

Cp

It's very important that you use the right dome and extension ring with this lens or you will get poor results.

I use the lens with an 8" Aquatica dome.

Cheers

James

Have you contacted Woody Mayhew at nexusamerica.com. I believe he uses a very similiar setup to yours.

James

I have included two samples of photos taken with the Nikon 12-24 with the Nexus housing. The first was taken with the 50mm extension and the 170mm port. It was taken about 80' deep in New Jersey in less than 20' of visibility and it was dark on the bottom. The exposure was f6.3 at 1/30th second with two DS-125 strobes. You can see the loss of sharpness on both sides and the bottom.

The second photo was taken with the Nikon 12-24 with the Nexus housing with a 40mm extension and the 170mm port. It was a depth of about 65' in New Jersey and the exposure was 1/10th second at f7.1 with two Ikelite DS-125's. The sharpness looks better and I am not sure if I am getting a sharpness loss due to the shutter speed. Visibility was about 40'.

I have talked to Woody Mayhew and he has tried the 12-24 with various extensions and with diopters on the lens. I don't think that he is sure of the right combination. I choose the 40mm extension because of info on the usanexus web site.

Beside a correct extension there is a major reason for this kind of unsharpness in the corners with such an extreme wideangle:

Rectilinear wideangles can only focus on a flat image (like on land, flat objects). But your dome produces a virtual image, which is a spherical curvature.

So you cannot focus on center and edges simultaneosly with a rectilinear lens.

The curvature of the fild virtually appears to be stronger when the virtual image is closer to the dome. A large dome radius moves the virtual image more far away (~ 3 times the radius = distance from dome) and the DOF has a chance to cover becuase it becomes just next to infinity.

This is why big domes can compensate this error more than smaller ones can. Stopping down of course helps to get the corners within DOF. Remember: The center is the farest point of your virtual image. Maybe intended frontfocus combined with DOF could also help a little.

But no, I can not say something to the extension rings for this rig. Just a very sure reason for this problem beside the dome positioning.

by the way, fisheyes do not suffer under this problem as they focus on a spehrical image, not a flat object like rectilinear wideangles.

Julian

I am shooting the 12-24 with the FP170 and a 40mm extension. I've only had this setup for a short time, so my experience is limited. In some of my shots, I see a little softness in the very corners, but some I do not. It seems acceptable to me, but I certainly would be interested in hearing how to improve it. Below are a couple of shots from my first outing with the system. Note that I chose these pictures because they have something in the corners to look at. Also, they look a lot softer overall @640 with jpg compression than they do at full size, so I've included a crop of one of the top left corners.

Also, side question, has anyone tried to 10.5 fisheye with the FP170? Tom @ MCD recommends the smaller 120 fisheye port, but I was just curious if the 170 would work (save me $1k).....

Cp

Here are the shots: