Split field shots with Ikelite 3" dome - what aperture for sufficient DOF?

[peterplantman]

Hi everyone!

I have the opportunity to borrow a 3" dome for my 16mm fisheye to shoot some split field shots during our 2 week vacation. I don´t earn enough money from my photography (yet, hehe...), so I´m currently stuck with a film camera, Nikon f90x (called N90x in U.S.) with full frame format (so 16mm will be 180 degree diagonal coverage). This housing does not (according to Ikelite) support the new 4" dome port. Since I won´t be able to see the results until after the holiday, I´m desperate for a few tips. I suppose the 3" dome creates a closer apparent image than the 4" dome, so the choice of aperture becomes more critical for achieving acceptable sharpness both in the water- and the air part of the pictures.
So, what is your recommendations? What aperture is recommended? Is it necessary to use f/22 (and accompanying deteriorating sharpness in the whole picture)? I am going to use it in quits shallow waters, so the under water scenery may be very close. Do you have a "cheat sheet" for apertures, given the different distances to the under water subject? Any suggestions would be most appreciated!

Thank you in advance!

/Peter Plantman

[Papa Bear]

Read Jonathan's how to here! It requires a special lens or Diopter. You need to try and get it right sense your do overs will be limited! Good luck;)

[Papa Bear]

Look at "Wide Angle Photography" great explanation!

[peterplantman]

OK, thanks!

The thread does not cover my question, hence I posted it here. There is no way of putting a split diopter on a fisheye. To avoid any misunderstanding, I will write the question only below:

If I use only a 6" diameter dome port (not the usual 8" or 9"), what is the maximum aperture that I can use to receive a reasonably sharp background (close to infinity)? Should I use AF and focus on my subject under water, or should I prefocus at a distance approximately 1/3 of the distance between subject and infinity and rely on DOF? Any suggestions are welcome.

Thanks again!

/Peter

[Papa Bear]

Can you switch from Auto to manual underwater? If you can I would F-stop it down for deepest depth of field and focus in the middle distance by either auto and then switch or go manual and slit the difference. Good luck and yes you can use a diopter with a done and a wide angle. That is who it is done. The other option is photoshop!

[Papa Bear]

I would try it in a pool before you go!

[peterplantman]

Thank you!

No, the fisheye lenses can not be used with a split diopter. The fisheye lenses have a rear filter mount. (Or, maybe you can custom make one but it will not be worth it. A years salary is my guess...) But the fisheye has outstanding DOF and also has the ability to focus extremely close. That´s why some people use fisheye. If you can work without a split diopter, you do not need to put the surface in the middle of the picture. You can use e.g. the golden thirds...

And of course, I could just stop down to f/22 to be on the safe side. That should make sure all elements are within DOF and there is no problem hand holding this lens at lower shutter speeds either, so no camera shake is expected. But shooting at f/22 just does not deliver optimum sharpness, due to optical limitations (due to diffraction, it has nothing to do with construction, just physics). This is especially troublesome with this lens that is a bit soft in the corners even at f/8 (that usually delivers the sharpest images at most lenses).

I will try it out in a pool this weekend. Just tried to save me some trouble:rolleyes: The trouble with pools (indoor, I live in Sweden and night temperatures go below freezing nowadays) is the lack of light. If I´m testing f/8 - f/16 shots in the surface, the shutter speed will be way above 1,5 seconds. Hand held pictures under those conditions will not be the best way to scrutinize image sharpness and DOF:D

Thanks!
/Peter

[Papa Bear]

You are right they have to be custom built! But if you are looking for the "Best" then you have to do what it takes. You're settling for what you can do on your budget, so you might have to compromise your focus standards to get the shot! Then there is always Photoshop! Take care and good luck!;)

[peterplantman]

I´ve never heard of anyone using a close up lens on a fisheye. A split close up seems even more far fetched. Since it is rear mounted, I doubt that the results will be even satisfactory. You would probably end up with a blurry line extending om both sides of the surface. Loooads of money spent and results that are inferior to just using the lens. I think the first option is just a little too tempting. :rolleyes:

On any other wide angle lens, I would definitely consider a split close up, but that´s a different story. I have a split close up for my 20mm f/2.8, but I´m not really happy with this for two reasons:

1. You need to have the surface cut through the center of the image. Even the slightest wave action totally spoils the picture.

2. Sometimes the sun is reflected in the cut of the slit close up lens. This emphasizes the surface in a way that spoils the picture, in my opinion.

For these reasons, I´m planning on switching to only using fisheye for split images (and maybe a normal lens in a flat port once in a while). Fisheye gives so much more freedom to work with the composition of the image.


Cheers!

/Peter

[tarczy]

Uhmmm . . . the best that I can figure it, the issue here is whether or not you can shoot over/under shots using a fisheye lens. Hopefully I'm correct in my interpretation of this thread so far.

First . . . let's clear up some issues . . .

1) There is no way you're putting a diopter (split or not) on a fisheye lens. It won't happen.

2) I have never seen a fisheye lens used in a 6" port. Yeah . . . I guess you could do it, but why? Two thirds of your image would consist of the black edges of your port. It would look like you were looking out from inside a tunnel. In other words, serious vignetting! Unless . . . you're using something like Ikelite's super-wide 6" dome port pictured below . . .

http://i75.photobucket.com/albums/i284/mongo255/Miscellaneous/5503_15.jpg

However, this port only provides 170° coverage, so on a full frame camera, with 180° wide angle lens, you're still gonna get big time vignetting. Suggest you spring for the 8" dome port. You'll be much happier.

Check out the links below for further discussion on the issue . . .

http://www.photography.willandsam.com/Reviews/dabigadome/index2.htm (http://www.photography.willandsam.com/Reviews/dabigadome/index2.htm)

http://www.peterpeterpeter.com/ikelite/10-5_port_tests/index.htm (http://www.peterpeterpeter.com/ikelite/10-5_port_tests/index.htm)

As it relates to over/under shots with a fisheye (assuming you've worked out all the vignetting issues), I would work to get that lens stopped down as far as it will go. Check out the first image in Rod Klein's Anilao/Philippines gallery . . .

http://www.rhkuw.com/gallery/anilao/index.html (http://www.rhkuw.com/gallery/anilao/index.html)

Great over/under shot (with a fisheye and no diopter)!!! How he managed to pull that off I'll never know, but I suspect he had that lens stopped all the way down to 22. You could certainly send him an e-mail at rhkdiver@comcast.net (rhkdiver@comcast.net) and ask him. I don't know if he'd be willing to give up all his secrets, but he's a great guy and I'm sure he'd point you in the right direction.

Hope this answers your question.

Best!

[Papa Bear]

Send Rod some Skittles he will tell you just about anything! LOL Do they have Skittles in Sweden? Anyway I would still try it in a pool or pond even if you don't go in yourself. With the film thing and the distance do overs are out! The F-Stop all the way closed, as I said, is your best bet! So put it on a tripod and drop it in a pond and see if it will work! ;) Good Luck! Whatever happens post the results!

[peterplantman]

OK!

Thank you guys! I´ll be using the "super wide" 3" dome. I´ll try it out on saturday in a pool. I have no idea what the light conditions will be, though...:o I won´t be using my flashes because I want to keep in neat in the pool (a spa pool, I will probably not be alone, just me and my family, so nothing bulky... :D )
On my trip I will probably try a few pictures with balanced flash fill as a complement if there is too much difference in f-stop between air and water. I will probably not be able to post any pictures until after the trip, sorry! Well, I don´t know if this is of common interest, anyway, since most people shoot digital and a 4" dome, regardless of housing manufacturer. My main strategy is to prefocus on the subject under water and adjust the f-stop to get a reasonably sharp background. Goal is to stay at f/8 if DOF allows it. I´ll probably shoot a bracket-round at f/8; f/11; f/16 and f/22 to begin with, just to check when general sharpness begins to suffer (for future knowledge, since I will develop all slides back home...). And I plan on shooting mostly macro/CU anyway, but that part is already figured out ;) .

I´ve decided not to bother Rod Klein with this issue, since he probably shoots with a 4" dome (as most people do, at least the pro´s and "semi pro´s"). But thanks anyway! Pretty neat gallery! Reminds me to take advantage of my philippino friends and take up the tagalog practice. Diving there is truly super...

[Jonathan Bird]

OK, the simple answer is that you can do it, but the results will suck.

The Ikelite small dome (which is actually about 5" in diameter, but has a 3" radius and would be a 6" dome if it were a full hemisphere) is lousy with fisheye lenses. Even their supposed "fisheye" version of this port (which has no dome shade) doesn't work. This is not because it's a small diameter, but because it is not a full hemisphere. As a result, in order to prevent it from vignetting, it has to be way too close to the lens for anything approaching good corner sharpness. If Ikelite made a 6" dome in a full hemisphere (the way the 8" dome is made) you could use it with a fisheye, as long as it could focus on the closer apparent image (~12") of a small dome rather than the somwhat further-away apparent image of an 8" dome (~16").

The full hemisphere 8" dome is far far better for this application. So much better that it's not funny!

Also, it's hard to keep the water straight in a split shot with such a small dome unless you are literally working in glass-calm conditions.

Yes, shoot at f/22 if you want a prayer of this working out. Focus on whichever if more important...the underwater subject or the surface subject, and pray for sharpness in the other half. The problem you have with such a small port for split shots is that the underwater half of the image is going to be at an apparent distance of 12" maximum. The above water will be much further, so you have to bridge that huge gap using nothing but depth of field. Not impossible for a fisheye (which is the only reason this has a prayer of working) but you will need a small aperture!

Split diopters fix this problem in rectilinear lenses, but as you know, you can't put a split diopter on a fisheye. Hence, larger domes work much better because the apparent image is further away and you don't need as much DOF to pull it all together.

So you have three things going against you with this port:

1. Bad nodal point arrangement with this particular port because it's not a full hemisphere causing poor corner sharpness.

2. Small port with very close apparent image to overcome.

3. Very hard to keep the waterline in the middle on a small port.

I hope this helps, and sorry the answer wasn't better.

Jonathan

[peterplantman]

Thank you, Jonathan!

Yes, I am very well aware of the problems you´re mentioning. The problem of a dome too close to the nodal plane of a lens is actually quite common, but surprisingly few people seem to make complaints to the manufacturers. I guess the ultimate solution would be something similar to the new 8" dome, where you choose a "distance ring" depending on your lens. Classical Ikelite is of course that they recommend distance ring (or whatever they call it) depending on how long lens you have. I guess a more appropriate way would be to choose distance ring depending on the focal length of your lens (and hence the nodal plane). The problem is of course exaggerated the wider your lens. :( I have been soooo close to buying a 8" dome for my housing, but recently they added something on their web-page saying it does not fit older housings. Mine is... I´ve mailed them and they say it won´t work. My friend the commercial photographer (who borrowed me the 6" super wide) also has the 4". We´ve decided to give it a try later and see if I can make some modifications to my housing. My guess is it´s the aperture control knob that´s in the way, but we´ll see later. He´s off to Sanzibar in two weeks (will be gone a month) and I´m off to Thailand in 5 days with wife and kids. So, now is not the time to dismantle my housing ;) I guess I´ll be able to pull off some pool shots that I can try selling to the travel agency later... Another plan is to shoot some "beach shots" of my 3,5 yrs old daughter playing with her mask in very shallow water. We´ll bring along some leftover rice and see if the sergeant major fishes show up. This way the "air" part of the photograph may well be some palm trees only, say ten-fifteen yards away. That makes the focus issue a little easier. I guess ti´s a good idea to shoot some shots with a lot of negative space. That way I can crop the images if corner sharpness becomes too crappy. (I take slides, so it´s mainly a matter of scanning resolution.) Anyway, I´ll use the equipment for UW-shots as well and my main focus will be on macro anyway, so it´s not a matter of life and death to pull this off successfully. But while you´re in the water with your kids, you might as well give it a try. It must be POSSIBLE to get decent shots. How did you Ikelite users do before they promoted the 8" dome system?

So, thanks everyone for all the input! This starts to become quite a thread for a very marginal issue. The future will tell if anyone else will have use of the posted information. It´s been great for me, personally, anyway!


/Peter

[Jonathan Bird]

How did you Ikelite users do before they promoted the 8" dome system?

I used a Subal for wide angle and complained frequently to Ike!

Peter, the 8" dome WILL work with your film housing, but unfortunately not with the shortest mounting ring, which is the one you need for the fisheye. If you were to use a zoom or something which is longer so that you can use one of the longer extensions, it will fit fine.

Jonathan

[Jonathan Bird]

Classical Ikelite is of course that they recommend distance ring (or whatever they call it) depending on how long lens you have. I guess a more appropriate way would be to choose distance ring depending on the focal length of your lens (and hence the nodal plane).

One of the problems with Ikelite in this regard is that they make so many housing for so many cameras that they do not have the time or resources to truly research the exact amount of extension required for each lens. They kinda eyeball it, and it's usually pretty close. But as I determined when I did extensive pool testing with the 12-24 with their help, they can be fine tuned quite a bit if you are willing to take the time to do it.

Jonathan

[Paul Young]

You won't have the depth of field you need. If you can get
enough sharpness for the above or underwater but not both,
take two photos, one focused for above and one for underwater.

Then merge them in Photoshop.

The purists may complain but it is better than no photo.