Lens choice: Fisheye vs. rectilinear?

[Storker]

Having been a hobby photographer - not exactly contest level, but at least half-decent amateur level - for a few decades, it seemed quite obvious to bring a camera underwater after getting my scuba cert. To find out if UW photography was right for me, I started cheap by getting a UW house for my aging Canon G9. Naturally, I quickly experienced the limitations of a simple compact behind a flat port and bitten by GAS I'm wishing for an OM-D.

But I'm at a loss when it comes to deciding what lens(es) to buy and would like some advice. Never been intrigued by the fisheye perspective topside, I'm initially considering a rectilinear WA. Because of the low light conditions here at 63 degrees latitude, I believe that a fast lens is right for me, and I'm thinking hard about the Olympus 12/2.0. The Panasonic 9-18/4-5.6 is of course a fairly affordable alternative giving me a wider FOV than the 12/2.0, but I'm afraid it's a bit too slow for the lighting I'm experiencing up here. My G9 shots have all been at f/2.8, often at 400-800ISO, and I'm afraid that the low speed of the 9-18 will make AF problematic. And a huge rig with a couple of strobes and a focus light is currently out of the question, since that'll probably be too much for me to handle at my diving skill level.

However, it seems to me that almost everyone is using a fisheye rather than a rectilinear WA, and I'm wondering how different a fisheye is underwater than it is topside. If I could get some advice here, I'd really appreciate that. Particularly if that advice also included pros/cons for either of the alternatives.


Just to illustrate what level I'm at and what my ambitions are, here is my flickr photostream and here are my UW photos so far.

 

[decidedlyodd]

A fisheye is more of a novelty above water because there are lots of straight lines distorted by the fisheye effect. Underwater, straight lines are much less common--two big exceptions being shipwrecks and pilings. However, even in these cases, the fisheye effect just doesn't seem to bother people viewing underwater photos as much for whatever psychological reason.

Having a fast lens matters a lot less underwater too. When using a wide angle lens behind a dome, the camera has to focus on a virtual image which is curved. The aperture has to be closed down more to increase the depth of field to keep the entire image in focus. If you shoot wide open with a dome, you'll get soft corners extending quite a ways into your image. This is more pronounced with smaller domes and rectilinear lenses. With my Tokina 10-17 fisheye and a 100mm dome on a Canon T2i, I'm shooting at f/5.6 or higher (often more around f/8) to get reasonable sharpness.

With a smaller sensor, you get an equivalent angle of view with shorter focal lengths. This makes the depth of field wider for the same f-number at the same angle of view. So a MFT camera like the OM-D E-M5 lets you get away with lower minimum apertures than a camera with an APS or full-frame sensor. But still a rectilinear lens at f/2 behind a small (or probably even large) dome will probably not get you great results.

A camera with a good sensor that performs well at high ISO helps a lot here. The E-M5 definitely fits this bill since it has one of Sony's outstanding new sensors. Good strobes are necessary too, so I wouldn't recommend skimping here either.

 

[Larry C]

Primary uses of WA underwater tend to be seascapes and larger subjects. Generally people want to shoot a reasonably large subject with a background of a reef or blue (or green in your case) water, and perhaps a sunburst in the background. In green water, kelp also makes a great shot. For these, fisheye shots don't cause problems because as decidelyodd said, there are few straight lines. The keys for underwater use tend to be close focus ability and sharpness at larger apertures. A fast lens can be an advantage if it offers a sharper picture without shutting down so far, and the ability to use higher ISO settings is important because it allows a smaller aperture and faster shutter speed which are necessary for sunball backgrounds and the like. I'd look at the forums and see what people are doing with the OMD with various lenses. There are some good examples out there that might help you in deciding which lens combo suits you best. There has been quite a bit of discussion of the OMD, as well as a couple of tests and many sample pictures on the Wetpixel DSLR forum, so you might take a look there. Olympus OM-D E-M5 - Digital SLRs/Housings - Wetpixel :: Underwater Photography Forums

 

[Storker]

A fisheye is more of a novelty above water because there are lots of straight lines distorted by the fisheye effect. Underwater, straight lines are much less common--two big exceptions being shipwrecks and pilings. However, even in these cases, the fisheye effect just doesn't seem to bother people viewing underwater photos as much for whatever psychological reason.

Interesting, especially the last remark. Can it be because "people" don't have as many reference images for underwater photos as they have for topside photos?

Having a fast lens matters a lot less underwater too. When using a wide angle lens behind a dome, the camera has to focus on a virtual image which is curved. The aperture has to be closed down more to increase the depth of field to keep the entire image in focus. If you shoot wide open with a dome, you'll get soft corners extending quite a ways into your image. This is more pronounced with smaller domes and rectilinear lenses. With my Tokina 10-17 fisheye and a 100mm dome on a Canon T2i, I'm shooting at f/5.6 or higher (often more around f/8) to get reasonable sharpness.

Thanks for the info on the limitations of using large apertures behind a dome port, I wasn't aware that the virtual image from a dome was curved. However, I'm not totally convinced about your statement that "Having a fast lens matters a lot less underwater". Looking at my own pictures, they are all taken at f/2.8, with shutter speeds from 1/30 to 1/10 sec and ISO speeds from 160 to 800ISO. As previously mentioned, there's not that much light underwater up here. In the summer, there's algae in the top layer absorbing the light, and in the winter the sun is pretty low in the sky. So we have quite poor lighting conditions more or less year round. Shooting at f/8 under the lighting conditions I've experienced so far would require ISO speeds from 1280 to 6400ISO. Even with a good sensor like the OMD's, that's a recipe for pretty noisy pictures. With my diving skills and experience, I need to decrease the task loading level and make photography my second (or third) priority until I've logged another couple of dozens of dives. So even if I'd like to have a strobe (or two), I think that I probably should wait a bit before buying a strobe.

Primary uses of WA underwater tend to be seascapes and larger subjects. Generally people want to shoot a reasonably large subject with a background of a reef or blue (or green in your case) water, and perhaps a sunburst in the background.

From what I see on the 'net, there's just a few types of subjects which seem to totally dominate the underwater photography genre. Or is that just me not having seen enough pictures yet?

A fast lens can be an advantage if it offers a sharper picture without shutting down so far

Yep, that's why I've been considering the 12/2.0. This article on nauticamusa.com claims that the 12/2.0 can deliver quite good quality results behind the 4.33" dome made for the Panasonic 8mm fisheye. But if I can become comfortable with a fisheye the 8mm may be a better solution after all...

I'd look at the forums and see what people are doing with the OMD with various lenses. There are some good examples out there that might help you in deciding which lens combo suits you best. There has been quite a bit of discussion of the OMD, as well as a couple of tests and many sample pictures on the Wetpixel DSLR forum, so you might take a look there. Olympus OM-D E-M5 - Digital SLRs/Housings - Wetpixel :: Underwater Photography Forums

Thanks for that link, I'll look into it.

What makes the OM-D so attractive for me is that the controls are very close to the controls of a dSLR, unlike any other micro-4/3 camera I've looked at. Since my primary topside camera is a Nikon D300, that's a big plus. I'm not ready to handle a dSLR house yet, I need to use something I can hang on my BCD out of the way when I'm focusing on the diving. Adding a 14-42 and perhaps the 40-150, I can save quite a bit of luggage space, using the OM-D as my topside travel camera as well as underwater. And maybe I could get a semidome port and a close focus diopter for the 14-42 for a multipurpose setup.

 

[Imla]

My experience is... Wait a little.
If you are used to D300 above water, and have certain ambitions also under water, You might feel limited by the micro 4/3.

Men... hvis du tar en prat med Lars Kirkegaard på fotografit.eu så kommer du til å få mye bra tips.
Han er en av de som virkelig har sans for de små speilløse.

Eller tar deg en tur innom her: https://www.facebook.com/groups/120609274687241/
Så vil du finne MANGE som kan hjelpe deg, og som også er vant til å ta bilder i Norge.
Selv bruker jeg D700 i Aquaticahus etter å ha oppgradert fra Nikon P7000 i en Fantasea hus. Du kan se noen av bildene her: https://www.facebook.com/media/set/?set=a.10150657216761467.381927.546211466&type=3
Flesteparten av disse er tatt med Kompaktkameraet. De fleste er tatt med bruk av 1 eller 2 Solalykter. 800 og 1200 lumen.
Ingen er tatt med bruk av strober.