15MM BAYONET MOUNT LENSES
It is important to note that Leica lenses had their focal lengths specified in millimeters from 1925 to 1928, in centimeters from 1928 to 1970, and again in millimeters from 1971 onwards360.
15mm f/8 Hologon
Zeiss Hologon
The Zeiss 15mm f/8 Hologon is a lens designed by Carl Zeiss in Oberkochen, Germany, and was first introduced in 1968, permanently affixed to a modified Zeiss Ikon Contarex Hologon camera body360. This lens consists of three elements and is highly corrected, featuring fully hemispherical rear and front elements, with the central element functioning as the iris360. The Zeiss 15mm f/8 Hologon offers an exceptionally wide coverage of 110 degrees, requiring a special graduated neutral density filter that is darker in the center360. This design helps counteract the fall-off at the edges360. When using the filter, the lens aperture is effectively reduced to f/16360. Without the filter, at f/8, the coverage becomes uneven360.
Leitz Hologon
The Leica 15mm f/8 Hologon was introduced at the 1972 Photokina and entered the Leitz catalog in 1973 under catalog number 11003183. There was an agreement in place that Carl Zeiss would supply the 15mm f/8 Hologon in Leica M-mount for sale by Ernst Leitz, Inc51. The lens was sold alongside a special clip-on 15mm viewfinder360 and a graduated neutral density filter (catalogue number 13002)183. A fitted leather case (catalogue number 98281) was also available183.
Unlike the Zeiss version, the Leica 15mm f/8 Hologon, which is not rangefinder-coupled, could focus down360 to 0.2032 meters183. The angle of view of the lens was 110°183. The lens had 3 elements and was supplied without a lens hood183. The rear elements of the 15mm f/8 Hologon lens extend significantly into the camera body, which partially obstructs the metering cell235. As a result, the meter may fail to obtain an accurate reading of the white spot on the shutter curtain, leading to incorrect exposure235. The only solution is to meter with another lens first235. This lens could be easily used with any M camera, including the Leica M5, which required the meter cell to be locked up, as the lens does not permit through-the-lens metering with this camera183. Additionally, the metering cell for flash exposure control on the M6 TTL is also obscured235. In this case, the flash unit should be switched to 'A' instead of 'TTL' to use the flashgun’s independent metering cell235.
Between 1972 and 1976, three batches of lenses were produced, totalling only 350 units, making the Leica 15mm f/8 Hologon quite rare360. The serial number range assigned by Zeiss was 5735851-5736300, although the Leitz 15mm f/8 Hologon brochure of 1974 features a lens with serial number 2593021183. This must have been a prototype, as no other 2593XXX numbers have been reported183. Poor sales and high production costs led to the Leica 15mm f/8 Hologon’s removal from the Leitz catalog by 1976183.