The Nikon 18-200mm lens covers such a broad range of focal lengths that others have called it a do-it-all lens. Well, it almost is, and for those situations where I find the 18-200mm lacking, and I don’t mind carrying a little more weight, I carry a small, lightweight sidekick lens. When I went trekking to Nepal last month, the sidekick I chose to bring along was the Nikon 10.5mm f/2.8 Fisheyefor ultra-wide fisheye shots.
The 10.5mm is a frame filling fisheye, stretching a 180-degree view diagonally across the frame. It does NOT produce a circular image. That wouldn’t be very useful in the field.
I like to think of the 10.5mm as an ultra ‘ULTRA’ wide-angle lens. The center of the frame is low on distortion and a great place to put people in the shot. The distortions are greatest at the corners of the frame. Outdoors, where there are no straight lines, the fisheye distortion can be used for dramatic effect.
If you’re not into the fisheye look, another lightweight and useful sidekick example might be a Nikon 50mm f/1.4. Its large, light-gathering aperture would be useful in low light or for blurring distracting backgrounds in portraits.