Since I started in photography, reflex mirror lenses were 'fools gold'. Most new photographers nibble at them, usually getting steered away by more experienced photographers. But it sounds great: a 500mm lens for a few hundred dollars that's small enough to throw in your camera bag. Mirror lenses actually have one real quality advantage: because the light is reflected from the mirror, rather than refracted through glass, they have no chromatic aberration.
But there's
a reason people carry around those 3 foot long, 10 pound 500 f4 lenses.
Mirrors are usually f8 aperture making them too slow to get any action
shots, and given the long exposure times f8 requires in all but the
best light, you still need a tripod even for that little bitty lens.
Plus the out of focus highlights are a rather unpleasing doughnut
shaped light ring.
I recently shot with the Sony 500mm f8
reflex on the alpha 350. My thinking was that the in body Image
Stabilization of the Sony SLR might make the lens usable without a
tripod. But I wasn't really optimistic. After shooting around a bit I
have to say I was pleasantly surprised. The lens is decently sharp as
shown here
and I found I can handhold it quite easily at shutter speeds of 1/500
(you may do better, I've got a pretty good caffeine tremor going on,
but for me this was excellent).
The out of focus highlights are still the not too pleasing doughnut shapes you can see in this shot.
But you can't have everything. Bottom line is this gives me an
opportunity to carry a long telephoto lens around when I'm not
absolutely planning on using it, say for a hiking trip. Its not going
to replace a 500 f4 for a dedicated bird or wildlife shoot, but its
still a very nice option to have.
