At the time of its introduction in 1969, the Zeiss 15mm f/8 Hologon was the widest-angle lens available for 35mm film cameras. Originally created by a Zeiss design team led by Erhard Glatzel, it couldn't be placed into production because, unlike 99% of all camera lenses ever produced, the 15mm f/8 Zeiss Hologon was only the second lens ever designed that had an angle-of-view too wide for any existing camera system.
The issue at hand was that, to achieve infinity focus, the rear element of the lens had to be positioned closer to the film plane than the design parameters permitted by existing 35mm Zeiss film cameras. This problem was ultimately resolved by removing the lens mount and reflex viewing system from an existing Zeiss Contarex camera, and replacing it with the permanently mounted 15mm Hologon lens and an optical viewfinder with an AoV matching the lens. The result was the Zeiss Ikon Hologon Ultrawide.
The name "Hologon" is derived from the Greek holos, which translates to "everything" or "complete", and gonia, which translates to "angle." This so-called Greek connection is practiced to this very day when naming Zeiss optical products.
n addition to having a single fixed aperture, the Hologon is also a fixed-focus lens with a focus range of about 20" (0.3m) to infinity. Your only exposure controls are your choice of film speed (ISO) and shutter speed. The camera is essentially a point-and-shoot in the most literal sense. It has a cloth focal plane shutter with a shutter-speed range of 1 - 1/500-second, along with B and T. The top speed for flash is 1/60-second via PC connection on the rear upper body panel.
Design-wise, the Hologon lens is as complex as it is simple. The lens is a basic triplet design-it contains only 3 lens elements. The front and rear elements are hemispherical in shape, and all 3 elements have been polished and assembled by hand to better ensure optically correct finishes and element alignment.