I used this lens to capture images of wildlife such as deer, moose, and elk.  500mm was enough to get a close up shot of several large animals, while allowing me to keep my distance.  This made it possible to photograph the animals without disturbing them.  I used it in combination with a monopod for stability since the lens is bulky and heavy. 

Having the ability to go from 50 to 500 mm was a nice feature.  It gave me a lot of room to adjust to a situation, although to be honest, I was almost always using it at it's full 500mm focal length. 

To give you an idea of its magnification, the normal human eye sees at 50mm.  My digital camera has a natural 1.5x magnifier, which makes 500mm really 750mm.  In other words, objects become 15 times closer than normal.

The biggest the aperture can get at 500mm is f/6.3.  Typically, to shoot a sharp image, a person should shoot at a fraction of a section that is faster than the relative focal length.  In other words, at 500mm (really 750mm), to shoot a clear image, you should shoot at 1/800 second or faster.  I had a monopod, so I pushed it to 1/640 second on some shots, but even then I could tell the difference.  1/800 second at f/6.3 doesn't leave a lot of light for the camera, therefore, I was almost always shooting at my camera's highest ISO which is 1600.  This makes the shots a little grainer, but it's a price I had to pay to expose the image correctly.  Even still, some of the images required a little post production in Photoshop to get the exposure to the correct levels.

Here are two examples of photographs taken with the Sigma 50-500 on a Nikon D50:

Jumping Deer
Bull Elk

The lens costs around $1000 and I'd recommend it to anybody looking for a telephoto lens in that price range.

Tags: camera lens, dslr lens, lens for nikon, sigma lens, telephoto lens