I found this lens...

Leslielynn · May 5, 2012

I'm a high school yearbook teacher and while cleaning out my cupboard, I found a Sigma mirror-telephoto 1:8 600mm lens. For what type of photos would my students use this lens? Thank you!

Buckster · May 5, 2012

Wildlife that's hard to get too close to, for the most part. Be aware that it will cause bokeh rings on highlights that are out of focus. Sometimes that can be used to artistic advantage, but usually it's just distracting.

tirediron · May 5, 2012

This lens is very slow and will require a LOT of light and a very stable platform (tripod) from which to shoot. It would be fine for stationary or very slow-moving subjects, but not for birds, or other quick movers.

Buckster · May 5, 2012

Here are some 600mm f/8 mirror lens shots somebody took:

Sigma 600mm Mirror Lens - a set on Flickr

Note the birds that can't be shot with one.

dxqcanada · May 6, 2012

Mirror lenses are also good for astronomy images.
Catadioptric system - Wikipedia, the free encyclopedia

Overread · May 6, 2012

It's actually an interesting point that whilst wide aperture lenses are popular for wildlife photography, f8 is actually used a lot more than people think. Mostly because depth of field at long focal lengths and great distances requires a smaller aperture to actually get the majority of an animal in focus. Of course wide aperture lenses come with the option of shooting wider in lower light and also the added light improves AF performance.

The 600mm mirror lenses are generally frowned upon because they can create doughnut shaped rings in the background highlights which are often considered undesirable. They also tend to be somewhat slower to shoot with in terms of focusing and light gathering. Their main bonus is, however, that they are very compact and light compared to regular telephoto lenses of similar focal lengths.