The Visoflex is a reflex housing made by Leitz in the 1950s and 60s, to add ground-glass focusing to rangefinder cameras. It is an update of the 1930s PLOOT reflex housing. The reflex housings add greatly to the distance between the lens mount and the film plane, so the housings are only suitable for long-focus lenses, or for very close focus. A special range of lenses was made for use with the housings, with short lens-tubes.
The Visoflex I was introduced in 1951, originally for screw-mount Leica cameras, but it was also made for the new bayonet-mount M-series cameras after the Leica M3 was introduced in 1954. It requires a double cable release; one cable to release the shutter and a second to activate the mirror-moving mechanism.
The Visoflex II followed in 1960; this was also made for both screw- and bayonet-mount cameras. It has a rigid arm which passes the action of the cable release, attached to the housing, to the shutter release on the camera body.