Split shot lens

In my ever so slow move to the Canon 20D DSLR underwater world, I have begun to ponder on the lenses I should be considering for underwater work. I've purchased the Sigma 50mm and after plenty of topside use I think this little guy will be one of my workhorse lenses for fish portraits and macro.

Of course, my life would have a very large void if I could not attempt to shoot split shots (half in/half out). With my 5050, this was as easy as attaching the Inon wide dome and shoot till the batteries ran out. With the DSLR I've entered a whole new turf -- fisheye lenses, rectilinear lens, split diopters, neutral densities... So many choices - so little money.

I would love to hear the opinions of some of you who have attempted these shots. Is a fisheye lens a better option than say the 10-22 rectilinear for these type of shots? I've read about numerous people using custom split diopters in order to get everything in focus and possibly adding a neutral density on the upper half. Anyone know where I could get such a monster? This filter kind'a stinks in my opinion because then I would be stuck with shooting either portrait or landscape shots (hmmm.. maybe Ike can add a diopter turning wheel to the port!).

sheesh... Lens/filter choices were much easier with my Oly5050.

I appreciate anyone's help or opinion on the matter.

Hey man, long time no see!

For most of the stuff I've played with, a split diopter really wasn't necessary as my wide angle lens could focus on the dome's apparent image without a diopter anyway and there is plenty of depth of field. As for the split density filter, that would depend on the conditions and whether you were using a strobe to light the underwater portion. If you could do it on the -5050 with the INON dome, you can most likely do it with an SLR behind a dome port. Can't help you with the lens choice except to say that I use the 15mm fisheye because my 10D can't use the 10-22.

Mike

The first thing on the agenda is your dome, it should be as big as possible 8 inches or more, second is the lens, the 10-22mm seem like a good canditate at the 10mm portion, the last is the depht of field, you need a lot, you will need to cover from about 12 inches to infinity with an 8inches dome, with a 6 inches dome your depth of field would have to cover from 9 inches to infinity, so you see the need for large dome.

Cheers

Hi Mike,

Yeah.. It's been a while. My offer to dive in the Keys still stands whenever you want, amigo. Thanks for all the info. I had wondered whether the diopter was really necessary when most wide-angle lenses could focus on the virtual image. I wonder why so many uw film photographers used the split diopters. Does the virtual image still exist when shooting above water through the dome port?

The use of a neutral density filter does seem a little more trivial. My thinking leaves me to believe its necessary on bright days in order to properly expose the (less than clear) water color. Although I did take some splits with the Oly5050 in Bonaire where the sky and water were properly exposed by shooting at high shutter speeds. I suppose this would need a little experimenting with on the DSLR.

If it isn't too much trouble, could you post a sample split shot or two you've taken with your fisheye. It would be nice to see some visual comparisons between the different lenses.

Hi Laz,

I've switched back to my old job so I may have a bit more time to take you up on your offer of some diving. As for examples, I'll have to look around. I played with the fisheye a bit in Indonesia and in the pool and the 17-40 in the Bahamas. I have to go back and check my archives to see what I've got left after I cleaned out my "file folders".

Mike

Thanks for the info, Jean. Your advice might explain why so many times I have had a hard time getting both the top & bottom of my split shots with my Oly5050 and the Inon 5" dome in focus.

To reiterate, say I had a 6" dome, I would need a lens who's hyperfocal distance was from 9" to infinity. How did you come about this number? Would a fisheye accomplish this hyperfocal distance at a larger apeture than the 10-22 rectilinear?

The first thing on the agenda is your dome, it should be as big as possible 8 inches or more, second is the lens, the 10-22mm seem like a good canditate at the 10mm portion, the last is the depht of field, you need a lot, you will need to cover from about 12 inches to infinity with an 8inches dome, with a 6 inches dome your depth of field would have to cover from 9 inches to infinity, so you see the need for large dome.

 

Cheers

BTW. How's the zoom ring for the 10-22 coming along?

Hi Laz good to hear from you man! Hope you're not freezing down there,

I think the 10-22 will have about the same field of view as the 15mm fisheye when used on the 20D. The fisheye will focus closer though.

I hate to say this (I'm in the same boat as you now) but the 10.5 on the Nikon would be the best lens. Barring that, I'd also recommend the 15mm for you.

The reason film photographers have to monkey with all that weird equipment was/is that a lot of them use older 20 and 24mm lenses on their film bodies and they don't focus that close. They also don't have the exposure latitude that we have with RAW shooting - they take one shot at one exposure and that's it. With RAW, when taking a split shot you can make two different exposures from the RAW file and overlay them to get a better balance. It's really easy when you have a discreet line like that.

The reason your 5050 splits work so well with the INON is that you were shooting a lens equivalent to the 10.5 and you were shooting in extremely shallow water with a well lit underwater subject. You could just as easily do that with a 10.5 and Aquatica/Ike but you'd need something to help float your camera or your arms would fall off in 15 minutes...:-)

Cheers

James

I am not sure from my understanding the 10mm has greater DOF than the 15mm fisheye.

From my quick thoughts fisheyes do not have greater DOF when the focal length is the same as the corresponding rectilinear wideangle. The DOF might increase to the corners as the reproduction ratio decreases in comparison to a rectilinear wideangle. But I’ve never found something to confirm my thoughts on fisheye DOF.

I think except the Sigma 8mm (which doesn't cover the frame) the 10-22mm is the best (technical) choice for splits.

Yes James, the 10.5mm simply gives the widest picture.

Well, as a Canon shooter (with a cropped camera) I have to admit that I do envy Nikon users about the straight forward DX lens line up especially the 10.5mm. Canon without FF is still somewhat limited in this respect in comparison to Nikon.

Julian

I think that the 10-22mm is an excellent choice for this type of work.

I have done some split levels with the 15mm sigma fisheye and it works well but the 10-22 focuses so close that there really is no reason to go with the fisheye. The fisheye effects are fun and nearly disappear on digital underwater but it is quite noticable with close subjects and straight lines like boat gunwales (which can't be aligned through the center in a split level shot).

This lens focuses close so you should have no trouble focusing on the apperent image of any size dome. You won't need a diopter for this. A split diopter seems like a lot of trouble. As for split neutral density filters, it sounds like a good idea but I'm not sure how you could use one. To be of any use they would have to be adjustable and therefore on the outside and how could they be big enough to cover the dome port? If they were on the inside you would be very limited on where you put the waterline. I myself think the biggest challenge is getting the waterline in the right spot and to stay still.

So I'd go with the 10-22mm easy. You know you want this lens anyway.

Hello Laz, the way I got these number is as follow: when using a dome port underwater, a optical element is created akin to a plano concave lens, this creates a virtual image projected at four times it's radius from the physical center of the dome, hence a 8 inches dome radius being 4 inches x 4 = 16 inches the subject appears at 12 inches from the front of the dome (one of the radius being inside the dome), this is the reason when you use a lens with a focusing scale behind an immersed dome the focus scale show 16'' for a subject that appears at infinity. you can see that the smaller the dome, the closer your projected become and the harder it get to have the proper DOF,

this phenomenon is also why it is critical to have a properly aligned dome so that the light ray coming from the dome are all centered on the optical axis of the lens, it is why I dislike Zoom lens for underwater work, the optical axis is always shifting an can only be positionned good at one focal lenght (I love my 10.5mm and 14mm).

hope I was of help.

Somewhere in there somebody was asking about depth of field, the answer is simple, the shorter the lens the more depth of field, it is the reason compact camera have so much of it that it become a nuisance sometime, just to give you an idea these little guys uses lenses in the 8 to 12mm, I mean a blind mouse would get it in focus with a 8mm lenses.

Hey Herbko, I will check with the office about the 10-22 zoom ring, but I am under the impression, it is or will be very shortly available, I dont work at the plant per say, most off my stuff is done from my home office so I give me the week end and I will let you know first thing next week.

Regard's

Hi Laz,

These were taken with the 10.5fe behind an 8" glass dome. No other accouterments. Neat thing about it was not having to tape up the holes like the Inon and the fact no water droplets stuck to the glass giving me nice clear shots. The second one probably answers some of your questions regarding sharpness and the "bending" in the corners. (note the phone pole in the upper right)

f16 @ 1/500

f16 @ 1/200

Some of us will be down in June doing the Abernethy's shark dive. Todd and I will be down a few days early June 11,12 for shore or maybe a boat dive from West Palm. Maybe you could join us for a day. Or perhaps the whole week. Still a couple of spots left.

Rand

I'm in the minority I am sure, but I'm the straight-rectilinear-or-die kind of guy when it comes to over/unders. As wide as money can buy.

In the past I had great results from a 15mm 3.5, but now the 14mm 2.8 is sharper and has less flares.

Other stuff:

Shoot M, not AF, set at hyperfocal.

A product called RVR, an aviation treatment for acrylic windows (no droplets).

Huge dome.

Big strobes for fill. Ususally a SS 400.

Not a big fan of fisheyes...makes the above-water portion look all whacked. Most viewers really notice this; the UW world is foreign, so they usually don't notice the fisheye effect there.

All the best, James

Eric, Craig, and I will be down March 27th for an Abernathy's trip. I also think some diving before will happen (Hopefully at the bridge!). Shoot, that's only a couple of months away. Maybe Canon will have an EF-S fisheye lens by then - ah to dream.

Cheers

James

Thanks everyone for all your help with my questions. After much consideration I have choosen to go with the 10-22 for my split shots. Aside from the convincing fact that I'd prefer straighter (not perfectly straight) lines in my shots, I suppose it all came down to UWPhotoNewbie's comment: "You know you want this lens anyway." How can I deny such a statement?!?! LOL! In all seriousness, my current Oly5050 setup shoots fisheye type shots and I can honestly say that I sometimes wish they weren't as fisheyed (not that split fisheye shots aren't nice in their own way). I did a little research on the net and, while I learned some new things, I'm now left with even more questions (Isn't the Internet great!?!?)

Using a DOF calculator, I was able to (sorta) figure out why the split shots taken with my Oly5050 are rarely in the hyperfocal range. It appears that in order for me to reach a hyperfocal distance with my 5050 (0.006 COC) at f8 (its smallest possible aperture) using the Inon dome (based on James' approx. of 10mm), I would need to focus on a subject that is 6.87ft away. This would result in everything from 3.45ft - ∞ being in focus. This shot was taken at f/6.3 at 1/500sec (why doesn't Fritz ever look my way when I'm taking his picture?!?! :? ) . Obviously the subjects were further than the required distance although I question how I got the focusing distance right as the camera was set on autofocus (manual focus from now on!).

Similar calculations for the Canon 20D (0.019 COC) with the 10mm shows an aperture of f/16 focusing at 1.1ft having everything from 0.58ft - ∞ in focus. If this is true and I'm not missing some important point, this is surely to make my split shot work a lot easier and quite a bit nicer (can you feel the excitement in my voice?!?!).

What I continue to question is how all this correlates with the (half) virtual image created by the dome submersed in the water? What effects would this have on the focusing distance? My typical shot (as most splits shot are) would involve an underwater subject (very) close to the lens (sometimes touching it as in the picture below) while having a nice landscape and sky in focus in the upper half.

While the shots aren't too easy to take and rarely come out perfect, I must say that I still enjoy shooting split shots with my little ol' Oly5050. Just for fun, here's one I took last weekend while checking out one of my favorite watering holes.

Once again, thanks to everyone for all your help. I truly appreciate it.

Herbko, the zoom lens have been shipping according to Blake at the Aquatica office.

Regards

Herbko, the zoom lens have been shipping according to Blake at the Aquatica office.  

 

Regards

Great! I'll email him and order mine. Thanks.

Hey Laz, me again, tought I would include a drawing from my workshop.

1) A small diaphragm is needed to cover the subject to background depth of field.

2) Don't forget that the sumerged subject is a virtual image projected at 4X the radius of your dome, so it will appear to be very close to the camera, this even if physically it is much further.

3) Your top side subject is still far away, optically and physically (most likely at infinity on a extreme W.A.). A Dome as no optical effect when not immersed in water so the top part is just a fancy water protector.

it's the wet part of the dome that allow the split shot to happen, when using a flat port your lens viewing angle is diminished by more or less 25%, causing the immersed part to see a much bigger subject, not to mention really soft (blurry) edges in the final picture if your using a fairly wide angle lens.

3) Your top side subject is still  far away, optically and physically (most likely at infinity on a extreme W.A.). A Dome as no optical effect when not immersed in water so the top part is just a fancy water protector.  

That brings up a good point. Based on this observation, it'd make sense to set the focus of the lens to the hyperfocal distance and not worry about focusing, auto or otherwise.