Here’s something you don’t see every day. It’s a 500mm reflex lens – also known as a catadioptric lens. There’s a pointless answer for you.
It’s a Canon FD – that’s Canon’s old-school manual focus lens mount. I’m using it on a Sony A7R with a Fotodiox FD to E mount converter.
The lens is a lovely, solid thing with a built in lens hood. It doesn’t feel as ridiculous as you’d expect on the Sony.
It uses mirrors to bounce the light up and down the length of the lens, reducing the physical length of the lens. The disc in the middle of the front element is one of the mirrors. Clever.
The downside is there’s no way of fitting an aperture ring into the light path. So the aperture is fixed at f8.
Which isn’t really a problem. On the Sony just set the camera to shutter priority and the ISO to Auto. Hand-held you’ll need fast shutter speeds to cancel out movement, but the Sony’s ISO performance should accommodate those. Better, use a tripod.
Other side effects of the design are weird doughnut-shapped bokeh balls (look behind the cat here) and a minimum focus distance of about 4 miles (actually 4 meters, but still).
The weird bokeh makes for some pretty nervous backgrounds.
The images I’ve got out of it so far aren’t super-super sharp, but that’s probably down to me holding it by hand. Having a tremor won’t be helping. But the pics are nice.
(My yardstick of super-super-stand-up-to-stupid-pixel-peeping-sharpness is the Canon FD 50mm f1.4.)
So, good image quality, fun to use, weird bokeh. Joy. I love how a new focal length makes you look at things afresh.