close-up diopter trick for Nikon 16mm

Hello folks, new to the forum but not UW photography. I recently aquired a Subal housing for my D100 and have been playing around with getting various lenses to work with the ports I own. (I have a couple of Subal film housings I've been using for years) Of particular interest was a desire to match this housing with the Subal SWB port and the Nikon 16mm (AF 2.8D) lense. I've initially talked with Tom at MarineCamera and he said the only port that would work with this lense was the (expensive) FEB port that I don't have. So, I tried a couple of things and stumbled upon something that is worth looking into.

As you know, the Nikon 16mm can't accept front-mounted filters, so the use of dipoters to gain close focussing for UW ports isn't an option. Big bummer, as this lense is nearly otherwise ideal for UW use. So.... For the heck of it, I *removed* the rear filter from the lense. Recall that Nikon says you must have this element in place to use the lense, and they supply a clear UV filter element (along with several others) for this express purpose. Well, when you remove the element from the lense, it essentially acts as a +2 or +3 dipoter!!! Try this above water, you'll see the lense no longer focusses past about 2 feet, and when it does, it indicates a much-longer distance. In the housing with the SWB port, the lense focusses (at least in my cloudy hottub) to at least 2 feet, and I can't verify anything further in my situation. At this distance (2 feet UW), the lense indicates an apparent distance of 1.25 ft, and has plenty of focus room left on the low end!!

This is potentially valuable enough that someone with access to clear water (pool, Palau, whatever) might want to consider replicating this experiment. You don't necessarily need my housing/port combo. Any housing with the 16mm should be able to verify that removal of the rear filter element acts like the insertion of a diopter on the lense.

I do hope this is a viable solution, it'll save me buying another expensive port and having to lug it around.

Thoughts? Anyone else tried this?

Joe Martz

land-locked New Mexico

I am going to Guam (gin clear bathwater) tomorrow to try the S2 out in an Aquatica housing. I may give this a try although I think the 16 mm will not have any trouble focusing behind a standard 8" dome. The digital "crop" should reduce or eliminate the need for a "super" wide dome as well.

I was in the pool biz for 17 years. get a DE filter for your hot tub, add a few toy sharks and a turtle or two and it will be just like Palau! remove the critters, then you can enjoy Guam conditions

Kindest Regards

Chris Bangs

I have an 8" dome port, so the 16mm fisheye has no trouble focusing with my setup - but I'll try it anyway just to see what happens.

Cheers

James

With the 16mm fisheye behind an 8" dome you can focus a few inches closer but without a filter it knocks out the infinite focus above water. I pushed the glass out of one of the suplied Nikon filters. I think you need to have the filter ring in place?

As I use up any film left on half-half shots of the boat pick-up etc I decided not to bother using this set-up any more.

The closer you get, the more awkward it becomes to light the shot. You get burnout on the sides with twin flash.

A subject midwater may be ok but then you need to watch out for internal reflections inside the dome. Also a dome shade is a good idea for protection as you may get TOO close!

Give it a go, see if it works for you.

I think the photographers at BSOUP were doing this many moons ago......

PauP