Effectively Using a Fisheye Lens
It was last January that I bought myself the 10.5mm f/2.8G ED AF DX Fisheye-Nikkor because of my interest in the extremes of photography. The fisheye photo is probably the most unique type of photo one can take, is one of the easiest to spot, and can easily create interesting and dynamic photos with lots of content and appeal.
However, it is also one of the most difficult lenses of which to master the use. Many times I have taken really bad photos with this lens, unknowing of its potential for misuse, and I am not alone. Working with other photographers in SPPS, I have seen its misapplication there as well. But I have also taken some amazing photos with it, and have seen other people take equally amazing photos, including in SPPS. It is sometimes hard to know if it is an appropriate lens.
It is true that the fisheye is not a lens to use all the time. It is certainly not one to keep attached to one's camera while walking around. But when the right photo does come along, and you have the fisheye in your bag, it can create stunning photos over which normal people ooh and aah.
So what I'm going to attempt to do is outline tips that I have concocted regarding the usage of a fisheye lens that can be followed to work towards better photos being taken. These tips are simply guidelines that I have found useful, and feel are good to follow.
Tip #1: Make The Lines Work With You
As you know, the fisheye distorts straight lines into ridiculous curves. Straight lines, depending on where they are in the photo can be pulled a lot, a little, or not at all. The farther they are from the the center line of the photo, the more distortion there is. The closer the line is to the midpoint of the X or Y axis of the lens, the straighter the line will be.
For example, on the photo below, there is immense distortion on the bleachers and moderate distortion on the press box. The curved bleachers lead directly out of the photo. The lines are working against the photo here. The middle of the photo, where there is no distortion, is a green field, and there is nothing interesting going on there. This photo could have worked if the horizon line were straight, and if the bleachers and the press box were symmetric on either side of the photo. This same photo, taken with a normal lens, would actually be very good.

An example of the fisheye misapplied by having the lines work against you. © Copyright 2005 by John Theodore Martello. All rights reserved.
Another example of using lines badly is in this photograph that I took of the entrance to War Memorial Gym. The lines of the ceiling all converge on the top of the photo. This results in your eyes immediately looking up and out of the photo. Everything in the photo swirls around the center and eventually point up and out of the photo.

An example of the fisheye misapplied by having the lines lead you directly out of the photo. © Copyright 2005 by Paul Lockaby. All rights reserved.
You can, however, make the lines work for you. Any straight line that goes through the center of the photo when shot with a fisheye will stay straight. So, say you are on a beautiful beach and there is a nice reflection, put the fisheye on the camera, put the horizon through the middle of the photo and watch the picture not look at all distorted, assuming no straight lines in the top or bottom of the photo.
For example, this photo I took at Virginia Beach is a good example of making the straight lines work for you in the center of the photo. You can barely tell that this photo was taken with a fisheye.

A good example of usage of the fisheye lens. © Copyright 2005 by Paul Lockaby. All rights reserved.
The awesome thing about that photo is the way you can see the entire beach, as well as the log in front of you and nothing looks terribly distorted. Of course, the only caveat to putting lines in the direct middle of the photo is that it totally violates the rule of thirds. Some rules, though, are meant to be broken.
Tip #2: Make The Distortion Work For You
Badly distorted people look bad, just like badly distorted lines. They don't lead you out of the photo, and they don't affect the point of entry, usually, but they do make the subjects look stupid. This can work to your detriment. If you have someone on the edge of the photo, that person's head and feet will be in the same place, but the person's waist will be somewhere else completely! Remember, people are straight lines, too!
Look at this photo I took at The Cellar -- which happens to be my favorite place to eat in Blacksburg -- and you can see the way the people on the side are all twisted. Nothing grabs your attention.
An example of a badly distorted subject when using the fisheye. Don't do like this photo. © Copyright 2005 by Paul Lockaby. All rights reserved.
But if you choose what you want to distort, you can accentuate an element in your photo. Usually this means shooting with some dead space in the photo and then cropping. In this example, I was about a foot and a half from the guy on the left and he took up the entire left side of the frame. There was good bit of dead space on the right, and I ended up cropping about a third of the photo off. However, the distortion is minimal and you are drawn directly into the photo, and even the rule of thirds is upheld.
When using the fisheye correctly, you can accentuate different parts of the photo without distorting the subject. © Copyright 2005 by Paul Lockaby. All rights reserved.
Tip #3: Shoot Your Photo As If It Couldn't Be Cropped
The distortion effect around the whole photo is uniform. Things on the left are bent the same as on the right and things on the bottom are bent the same as on the top. If the distortion is going to be obvious, such as in the photos in tip number one, then you need to make sure it is uniform. If the distortion is not obvious, as in the photos in tip number two, then you can work out a crop later.
In this photo, which ran in the Collegiate Times on November 2nd, 2005, the original photo had the whole group in it, with the speaker in the center. The fisheye made a nice circle around the speaker. I'll admit, the photo sucked to begin with, but what ran was even worse. Things on the right are straight, things in the middle are straight, and things on the left look like they were drawn by a crazy man.
A badly taken photo with the fisheye as a result of non-uniform usage of the distortion effect. © Copyright 2005 by Paul Lockaby. All rights reserved.
So if you shoot as though it can't be cropped, then you'll have to shoot photos that take advantage of the full frame and apply the distortion uniformly. For example, I really like this photo of RFK Stadium in eastern Washington, D.C., because of the way the distortion was applied uniformly around the bowl shape of the stadium, resulting a photo that doesn't look weird. It also helped that RFK is distorted to begin with. ;)

This good use of the fisheye lens allows you to see the whole stadium but doesn't immediately make visible any noticeable or negative distortion. © Copyright 2005 by Paul Lockaby. All rights reserved.
And those are all the tips I have for using the fisheye that I can think of. They basically boil down to thinking about exactly what you're photographing before you hit the shutter. A lot of shots made with the fisheye would be better shot with something like the 12-24mm f/4G ED-IF AF-S DX Zoom-Nikkor, which is almost as wide, but will take normal, straight photos without outrageous distortion. However, if you want that unusual shot and the photo lends itself to it, the fisheye is as unique as they come.
Having a circus lens is fun, because you piss people off by blowing up their heads and making their bodies small. Things that are close to you appear big and things that are far away appear really far away. However, it is possible to take completely normal photos with this lens that you could never get with another lens. It's just a matter of thinking about what's in the viewfinder beforehand.