Originally Posted by slvoid
Anyone tried using one of those like, 0.8 lenses wide open?
Most of those f0.7 or 0.8 lenses were mostly special design cine lenses (a la Barry Lyndon); I think Leica (ElCan) made a 90mm special use lens for the U.S. Navy for photo surveillance, but that was never commercially available. The benchmark ultrafast 50 is the Leica Noctilux-M 50mm f1.0, and until a couple of years ago, Canon made a 50/1.0L SLR lens that weighed a couple of pounds.
There are more, and a great site to read about them, is
http://www.naturfotograf.com/index2.html
including an image made with a Rodenstock TV Heligon 50/0.75.