New to photography: Fisheye vs. rectlinear ultra-wide lens etc.

[redstrom]

Greetings,

I'm very new to photography (been shooting with a d90 for three months) and an u/w photography wannabee, so please bear with me...

What is the difference between a fish-eye lens and an ultra-wide rectilinear lens, and are both used under water?

I'm curious as why cityscapes shot with a fisheye look really curvy on the edges while you don't seem to notice it under water. Is it a matter of staying away from straight lines, keeping the subject in the middle of the lens?

Ignoring macro lenses, would you typically use a wide angle lens u/w, or can you use the "out-of-the-box" 18-105mm lens to shoot corrals and smaller reef fish ?

Thx / Rik

 

[Mariozi]

What is the difference between a fish-eye lens and an ultra-wide rectilinear lens, and are both used under water?

Fisheye lens provide 180 degrees of view (either diagonally in the case of the full-frame or semi-fisheye or in any direction on the circular-fisheye or true-fisheye). But they distort everything. Rectilinear wide angle lenses generally does not provide such a field of view (maxing out at something like 120 degrees) but they keep straight lines straight.

Both have their use UW, depending mostly on subject size and distance.

I'm curious as why cityscapes shot with a fisheye look really curvy on the edges while you don't seem to notice it under water. Is it a matter of staying away from straight lines, keeping the subject in the middle of the lens?

It is. UW is very hard to find straight lines (unless you're shooting a wreck, pier etc...) and you can place corals and other sea structures close to the borders that the distortion will rarely be notice, just bigger fishes and divers when placed close to the border will show some distortion.

Ignoring macro lenses, would you typically use a wide angle lens u/w, or can you use the "out-of-the-box" 18-105mm lens to shoot corrals and smaller reef fish ?

Most people use separated lenses for wide and macro. There are some options in the zoom lenses where you can get some versatility, but you will most likely never get the same performance of a fisheye or extreme wide (14 or 15mm 35-equivalent) or a true macro lens like the 105VR.

Hope it helps

 

[scottfiji]

Like Marcelo said, if you're going to spend money on a dSLR setup, I don't think you really should use a long zoom like the 18-105mm underwater for a large number of reasons. I would do macro and wide-angle separately.

 

[cberk]

I am new to diving and UW photography and had a similiar questions when making decisions on equipment. I wanted a wide angle lens that could be used on land as well as UW. I decided on the Tokina 11-16 f/2.8 rectalinear lens. I recently took a trip to the Keys and dove the Vandenberg, Speigel Grove and Duane. The pics on my gallery are my first attempt at UW photography. I was very pleased with this lens.

 

[davelew]

Some images that you see shot with fisheye lenses underwater have been "de-fished" in software such as the "warp" tool in photoshop. Although de-fishing in software can degrade the image quality, the fact that the fisheye lens can get closer to the subject offsets this-- often the extra water would degrade the image more than the software post-processing.

 

[Nemrod]

Field of View - Rectilinear and Fisheye Lenses

A fisheye projection lens by definition has barrel distortion. A rectilinear lens projects straight lines as stright lines, a fisheye lens only projects a straight line as straight if it passes through the center of the field. A fisheye lens has between 160 and 180 degrees of view diagonal whereas a rectilinear typically are much less, about half the FOV, for the same focal length as a fisheye lens.

Fisheye lenses do not appear to have such distortion underwater simply because there are few straight lines. They have the same barrel distortion underwater as they do on land.

N

 

[redstrom]

Thanks for the input. Ended up with a Tokina 10-17mm fisheye lens. Hopefully I get to play with it this weekend on land.

 

[spt29970]

There is another problem with a wide zoom like an 18-105. When using a dome lens, you need to have the nodal point of the lens at the center of the dome to avoid spherical and chromatic aberration. As you change the zoom setting the nodal point moves around quite substantially. So, by using the right extension ring, you can make the system work for any given zoom setting, but you will be unable to change the zoom without the image degrading badly.

This problem isn't limited to just zoom lenses. Some prime lenses have the nodal point move during focusing, although it typically isn't anywhere near as bad as a wide zoom. That is why you see people gravitate towards the same group of lenses. These tend to be the ones that are sharp and have minimal motion of the nodal point.

 

[AussieByron]

Thanks for the input. Ended up with a Tokina 10-17mm fisheye lens. Hopefully I get to play with it this weekend on land.

Just letting you know that the Tokina 10-17mm is a different animal underwater than on land, especially at 10mm (which I shoot 99% of the time). have a look at this flickr group which uses the 10-17mm onland (Flickr: Tokina 10-17mm Fisheye). Most of the shots in this group are on land which you get the fisheye effect.

When I am shooting at 10mm underwater I only really get a noticable fisheye effect when the subject is only a few inches away from the dome. I simply love the Tokina 10-17 @ 10mm as I can fit large animals all in the frame when I am close enough to provide enough strobe lighting to light up the whole subject. This is the case with very large animals like big Rays and sharks.

Here are some of my resent examples of the Tokina 10-17mm @ 10mm

Regards Mark

 

[austin.takahashi]

@AussieByron: Wow! Your shots are beautiful! Sorry, I'm a beginner myself and I'm still aspiring to be a better photographer.