S&S MDX-D300 help needed: Nikkor 12-24mm & 10.5mm w/teleconverter

Hi....doing some upgrades and considering trying different types of shots with my existing Nikon D300/S&S MDX-D300 setup and need some confirmation of port/extension combos before I start spending money.

I have Nikon 10.5mm and Nikon 12-24mm lenses. I have the S&S NX Fisheye Dome port (acrylic, large dome, NOT compact)

Question 1: CFWA or WA Macro

I would like to put a teleconverter behind the 10.5mm to try some of really cool fisheye "macro" shots I have been seeing on the web. By itself, the 10.5mm works great with my NX dome. I assume if I put a Kenko 1.4TC behind it, I will need to put a port extension on the NX dome. Is that true? If so, which one? One educated guess said it looked like the S&S SX extension would do the trick.

Can anyone confirm or let me know what they use?

Question 2: Improving Performance of 12-24mm:

As many have noted in the past, the 12-24mm seems to have soft corners when use without "aids" in the NX dome. I have searched, but I can't seem to pin down a consensus about what combination of port extensions and/or diopters are needed.
-Port Extension Only (and which one)?
-Diopter Only (and which one)?
-or port extension and diopter combo (which ones?)

I have seen suggestions of SX extension only/no diopter; I have seen 40mm extension w/ +4 diopter; and I think a +4 or +2 diopter only.

Any thoughts? (I just hope then answer isn't "any of the above...maybe") ;-)

thx for your time
Paul

Backscatter's port finder says the 12-24 should have a 40mm extension with a +2 diopter.

You want to keep the entrance pupil of the 10.5 in the same place relative to the port, so
you want an extension ring that's the same length as the teleconverter.

Chuck

thx Larry....I have seen that recommendation plus a slew of others, so I was trying to get some real world experience. I have a few real world users that says +2 or +4 diopter only. Not sure why recommendations would vary so much with the same lens and same port - can't quite get my head around it.

the 12-24 focuses fine without anything - except for the corners.

As I understand it, adding a diopter causes the lens to focus closer than it does natively - supposedly a good thing with wide angle lens and dome ports where you are focusing on the virtual image created by the dome; the higher the diopter power, the closer the lens will focus.

And adding an extension to the port, pushes the dome and its subsequent virtual image (and the focus point) out further, and thus puts it out into the range of where the 12-24 will focus natively? I guess the combo of pushing it out and getting the lens to focus closer is hitting some magic point? hurts my brain and pocket book to figure out ;-)

btw, how do you shoot your 10-17 Tokina with your NX fisheye port with an extension? which one?

---------- Post Merged at 01:30 PM ---------- Previous Post was at 01:28 PM ----------

Chuck Tribolet:

You want to keep the entrance pupil of the 10.5 in the same place relative to the port, so
you want an extension ring that's the same length as the teleconverter.

Chuck

Click to expand...

thx Chuck. the kenko 300 Pro 1.4TC looks to be 27mm...there is not really a S&S port extension that hits that exactly. Closest is the 20mm; 40mm is next. I think I will try the 20mm and see how that goes

In order to keep the corners sharp, the virtual image has to be consistent from corner to corner. The entrance pupil has to be the correct distance so the focus doesn't change from edge to edge. Depending on the dome, some lenses may require a diopter. If the diopter is too strong, you'll lose infinity focus. You're on the right track looking for people with the same eqpt. diving in the same conditions. I haven't used the TC with my 10-17, but it's a popular application. I believe people are using the 1.4 with it.

Larry C:

In order to keep the corners sharp, the virtual image has to be consistent from corner to corner. The entrance pupil has to be the correct distance so the focus doesn't change from edge to edge. Depending on the dome, some lenses may require a diopter. If the diopter is too strong, you'll lose infinity focus. You're on the right track looking for people with the same eqpt. diving in the same conditions. I haven't used the TC with my 10-17, but it's a popular application. I believe people are using the 1.4 with it.

Click to expand...

sorry I think my brain/fingers got unsynched.....do you use an extension with your 10-17 Tokina (no TC) and NX fisheye combo?

Yes, I use the standard extension ring, as recommended by Sea & Sea. I've thought about trying it without the extension, as some other domes don't recommend one but I haven't so far. I think the standard extension is about 20mm. I can't remember what they call it right now.
Edit: It's the SX extension ring.

The purpose of the extension ring is put the lens' entrance pupil at the center of the partial sphere
of the dome. That allows the lens to look out perpendicularly to the dome which helps to keep the
corners sharp.

The purpose of the diopter is to allow the lens to focus on the virtual image which is a much closer
apparent distance than the actual subject.


Chuck

Chuck Tribolet:

The purpose of the extension ring is put the lens' entrance pupil at the center of the partial sphere
of the dome. That allows the lens to look out perpendicularly to the dome which helps to keep the
corners sharp.

The purpose of the diopter is to allow the lens to focus on the virtual image which is a much closer
apparent distance than the actual subject.


Chuck

Click to expand...

thx Chuck

You'll want the 20mm SX extension ring with the nikon 10.5 + tele, or the tokina 10-17mm.

Regarding the +2 or +4 diopter, most people will test this themselves, the right answer can vary depending on the particular port, housing and extension ring. A quick pool test should do the job! - Scott