Noctilux

The name Noctilux is used by Leica to designate their camera lenses with the widest maximum aperture.

So far all Noctilux lenses have been made for the Leica M mount.

The name Noctilux is a combination of Nocti, which is derived from the word nocturnal, while Lux is Latin for light.

[1][2] The Noctilux lenses have the largest maximum apertures in the Leica range.

With various models having f-numbers of f/0.95 or f/1.0 or f/1.2 or f/1.25 as its maximum aperture.

A Leica M8 with a Leica Noctilux-M 50mm f/1 lens.
Optical Diagram of Leica Noctilux 50mm f/0.95 ASPH lens.
detailed view