Zeiss R-Biotar 100mm 0.73 LOMO 100mm 0.73 Canon 50mm and 65mm 0.75 Leitz 50mm and 65mm 0.75 De Oude Delft Rayxar 50mm, 65mm and 105mm, and allegedly 150mm 0.75 De Oude Delft Rayxar 90mm 1.0 Astro-Berlin Tachon 65mm 0.75 Rodenstock XR-Heligon 42mm and 50mm 0.75 Rodenstock XR-Heligon 68mm f/1 Kowa 42mm and 65mm 0.75 Carl Zeiss Jena 50mm 0.77 Kowa 55mm 0.8 Zeiss R-Biotar 55mm 0.85 Lenzar Optics 184.6mm 0.9 (Photographic lens made by Lenzar Optics Corp., Riviera Beach FL, 0.9–8) Kowa 33.5mm 0.95 Kowa 55mm 1.0 Rodenstock Heligon 68mm 1.0 Canon 65mm and 90mm 1.0 Fuji 90mm 1.0 Kowa 90mm 1.0 Zeiss R-Biotar 125mm 0.8 References External links Table of all fast lenses by focal length and image format covered. Just how fast is that lens? f-number doesn't directly determine focal-plane illuminance, due to light transmission losses. Science of photography