This is the fastest lens for a digital mirrorless system cameras. It is the Ibelux 40mm f/0.85 for Sony E-mount. This lens is made by Kipon and the German IB/E OPTICS.
Ibelux 40mm f/0.85 lens demonstrated at 2013 CP+ show in Yokohama, Japan, Ibelux 40mm f/0.85 lens for mirrorless cameras is expected to be released in July, 2013 with a price between $1,200 – $1,600. The lens will be available in X mount (Fuji), M mount (Leica), Micro Four Thirds and Canon M.