Ikelite, S2, and 12-24 Lens

I am about to head out to Bonaire with my Ikelite, S2 and 12-24 setup on it's maiden voyage. I was able to get the zoom gear working smoothly. I read earlier about having to install the lens and gear after installing the front of the housing. This is a little uncomfortable to me since the inside of the camera is exposed during this operation.

I purchased a +4 diopter as recommended but have no prior experience with one. While testing the setup, I was unable to get the camera to fire with the diopter attached (almost like it thinks it is out of focus) but it fires every time without the diopter, even in the dome. My question is, with this setup, is the diopter necessary and does it have to be underwater for the diopter to work correctly?

I know a few of you have used this setup at one time and any help is appreciated.

Scotty - Check the Film Camera and Housings section, under the thread "Use of diopters with wide angle lenses, To use or not to use?." That might answer your question.

The link that Ike posted says that if the lens cannot focus to <12" it needs the diopter.

This is from Nikon on the 12-24

11.8 close focusing distance throughout zoom range

Judging by this, it would seem that the diopter is not needed.

I still have not figured out why the camera wouldn't fire with the diopter attached.

I know somebody has experienced this and will surface shortly.

Hi Scotty,

A plus 1 diopter will move the INFINITY focus to less than 1 meter. A plus two will move it to less than .5 meters, a +4 will move the INFINITY focus to less than .25 meters. That's probably why your camera won't focus on anything with the diopter on, it's all too far away.

Don't expect the camera performance to improve once the camera is in the housing behind the dome port. It won't go back to "working" again until it is underwater. That is because the dome port acts as a negative diopter when imersed in water. So when you combine the negative diopter of the dome with the + diopter on the camera lens, you are back in business.

That's the problem with diopters - you are "stuck" to underwater shooting once you have one that strong on your wide angle lens...

Hope that makes sense. I tried for a short simple explanation of a complicated subject. Best advice is to TEST IT IN A POOL BEFORE GOING ON A +THOUSAND $$$$$ DIVETRIP.

Cheers

James

... While testing the setup, I was unable to get the camera to fire with the diopter attached (almost like it thinks it is out of focus) but it fires every time without the diopter, even in the dome.

The reason it thinks it's out of focus is that it is out of focus. Out of the water, with the +4 diopter, the camera is seeing everything pretty blurry, so it won't let you fire a shot.

+4 is a lot of diopter, but that's what this dome apparently requires with this lens.

I concur with the advice to do some test shooting in a pool before you go off on a trip. One of the very nice things about u/w digitals is that the film you use for testing is free, the camera remembers what settings you used in its EXIF files, and you can look at and analyze the tests immediately.

Have fun with your 12-24.

Hey thanks, that is what I was thinking. Sort of like looking through my 15mm viewfinder for my Nikonos while above water.

Put your finger a few inches in front of the camera (no dome). See if it will focus on your finger.

Scottyb,

I have been using the 12-24DX with my S2/ike housing with both a +2 diopter and with no diopter. It works well with both. Have not tried it with a +4 diopter.

Great lens! I found the Ike zoom gear to work very smoothly. Much better than the gear for the 18-35mm.

Looking forward to seeing some pics,

John

If you say it works well without the diopter, I would think that would be best, eh? I was told by Ikelite when I purchased the port it would require the +4.

Scotty,

What does "works without the diopter" really mean? You want your lens to produce pin-sharp images edge-to-edge, without unacceptable rectilinear distortion, through the full range of f-stops on subjects at a variety of distances. You may find that the lens "works" without a diopter (underwater) at f/11 or f/16 on a subject occupying the center of the frame at a distance of 3-4 meters or more. But what about low light conditions when you want or need to open up to f/5.6 or f/4? What about close-focus wide-angle? What about detail near the edge or corners of the frame?

Similarly, a diopter-less set-up might focus reasonably well on a subject occupying the center of the frame with featureless blue-water all-around, but fail miserably when there is important detail near the edges and corners, particulary at wider aperture settings. Remember that the lens is actually trying to focus on the virtual image created by the dome port, and that virtual image is curved, following the geometry of the dome-port. This is part of the reason why larger diameter dome ports require less powerful diopters. Without the diopter, using wider f-stops with less depth of field, you may find that the center of the virtual image is sharp, but the edges and corners go blurry as the curvature of the virtual image bends inside the inner limit of depth of field.

Shooting tests in a pool with textured or patterned tiles makes it easier to determine whether the lens is holding focus edge to edge at different subject distances and apertures. Some time ago I and a few others here posted some pool tests using the 12-24 with different domes. The results were very interesting, and showed that differnent domes produced very different results.

Ikelite's recommendation presumably is designed to allow the lens to work with their dome in a wide variety of shooting situations at the full-range of f-stops. Maybe you never shoot CFWA, or perhaps you always shoot in bright tropical waters at shallow depths, around mid-day, and never dive when it's cloudy. If so, then perhaps you can get by with a less powerful diopter than Ike recommends.

By all means experiment with less powerful diopters and even no diopter, but make sure your tests cover the full range of shooting situations you will want the rig to handle in real life.

Robert Delfs

To me "works" means that the lens produces pin-sharp images edge-to-edge, without unacceptable rectilinear distortion, through the full range of f-stops on subjects at a variety of distances.

I understand that through trial and error, I can eliminate the possibilities and decide for myself which combination, or lack thereof, is best for my setup. I was hoping to bypass this step and draw from the experiences of those who used the 12-24 and Ike housing before.

To me "works" means that the lens produces pin-sharp images edge-to-edge, without unacceptable rectilinear distortion, through the full range of f-stops on subjects at a variety of distances.

Then I suspect you'll probably want to use the +4 diopter Ikelite recommends.

The 12-24 mm lens hasn't been out long, so the "experience" base still isn't very broad or deep. The fun of being an early adopter is that you get to make your own mistakes instead of just repeating others.

I've seen a lot of statements about what works with this lens or doesn't made or cited (on this board and elsewhere) which weren't absolutely correct. Such as the claim that the 12-24 lens is intrinsically unsuitable for use with a diopter, producing unacceptable rectilinear distortion. It turned out the testers (quite reputable folks) were using the lens in a port that is unsuitable for the 12-24 mm. lens.

I believe some dome ports can probably take the 12-24 without a diopter in a wide range of shooting situations. The big Aquatica dome may be one, and the Subal FE2 may be another. From what little I know about Ikelite dome ports, however, I'd be very surprised if leaving the diopter off worked well for you, given your requirements.

Ikelite utilizes a small dome port (I believe 6 inch diameter) which most likely requires a +4 diopter to focus on a virtual image that is very close to the dome.

I've been using the 12-24 in a Subal housing with an 8-inch port. With their short extension ring and no diopter I was getting soft corners. The designer, Arnold Stepanek, recommended a longer extension ring, (their #50), which would put the virtual image even further out (without a diopter). I had some great results on a white shark shoot at Guadalupe Island using that setup.

The 12-24 seems very sensitive to the port/extension ring/diopter combination. Once you get it right, it's a sweet, sharp lens.

Eric

www.ehanauer.com

I didn't have any luck at all with the +4 diopter. It severely distorted the shots around the edges. I had much better luck without the diopter.

With +4 Diopter

Without Diopter

That's exactly the problem with the 12-24 and diopters. Pincushion distortion that potentially turns into softness. A lower power diopter may work for you but I'd suggest doing without if you can.

I agree. The only problem I had, without the diopter, was that the lens didn't want to focus on close objects as well. Since I enjoy WA closeups, it might be a problem. I will take a +1 and +2 on the Cayman Agressor to see if there is a sweet spot.