LEICA Barnack Berek Blog: ZEISS HOLOGON

A MOST UNUSUAL LENS

By Heinz Richter

Zeiss Hologon 15mm f/8 on Leica M4-P

Modern lens design techniques have presented us with a relatively large number of super wide angle lenses of 15, 13 and even 12mm focal length. All of them are very complicated, multi element designs in order to avoid visible distortion and lack of sharpness due to under corrected optical aberrations. These lenses have become actually quite common, and few photographers even remember the super wide lens which started it all.

For many years, 21 and 20mm lenses were the maximum 35mm photography had to offer. Anything with a wider angle of coverage had to be of a fish eye design with all the draw backs of pronounced barrel distortion. All of this was changed with the introduction of the Zeiss Hologon 15mm f/8 in the early 1970s. This was unusual in many respects. Not only was the Hologon the first lens to achieve the unheard of angle of coverage of 110° without the usual fish eye effect, it was also the first post-war marriage between Leica cameras and Zeiss lenses.

Cross section of the three lens elements and the lens position inside the camera body.

Note the extreme proximity of the rear element to the film plane.

The Hologon was initially developed for the Zeiss Hologon camera, which was part of the Zeiss Contarex system. At the time it was thought impractical to offer the Hologon as an interchangeable lens, even with mirror lock up in the reflex Contarex. Instead, Zeiss opted for a separate camera body, based on the Contarex with the mirror box removed and with the lens permanently installed. It was their claim that extremely precise registration and centering was necessary for the lens to perform satisfactorily.

The Leica M cameras also met these criteria and the lens was made available in the Leica M mount also. It was sold with a special 15mm viewfinder included. The 15mm Hologon with its undistorted 110° diagonal angle of view is one of the most interesting lens designs in recent years. Conventional lens design theories would indicate that a lens with such specifications would have to be of a multi-element design. Computer aided research of wide angle lenses for aerial photography was conducted. The normal concept of using many thin elements in wide angle lenses was actually revealed as unnecessary. In fact, only three thick elements proved necessary to assure good performance of the lens. Subsequently, the Hologon is of a triplet design, although bizarrely shaped. Thus we have an example of an optical design which would not have been created by using conventional methods. Furthermore, it is safe to say that manual computations for this design would have literally taken years to complete.

Construction of the lens made the installation of a diaphragm virtually impossible without compromising overall performance. It was also impossible to offer a speed faster than f/8 for the same reasons, even though some of the modern optical glasses available today might offer the possibility to increase the speed of the Hologon.

It was felt that the restriction of a fixed aperture of f/8 would not pose any great disadvantage. Besides, a graduated neutral density filter, offering perfectly even illumination across the entire image area, would effectively render a speed equivalent of f/16. This could also be used in situations where the standard f/8 aperture would lead to overexposure.

Since the Hologon lens renders virtually distortion free images, the camera should be used perfectly level, to avoid excessively converging lines on verticals. For that reason the 15mm viewfinder had a built-in spirit level, which helped the photographer keep the camera level, especially when shooting hand held.

The ability of an extremely wide angle lens to render virtually distortion free images allow the photographer to shoot many photographs where it is impossible to tell that an extremely wide angle lens was used. But this is only one of the advantages of such a lens. The other is that it produces photographs with a rather different perspective. It is important to pay special attention to the foreground since the extreme angle of coverage will show a considerable amount of foreground when the camera is held level, even when used horizontally. It is also important to hold a camera with such a lens very carefully. It is quite easy for the lens to pick up ones knuckles.

The Hologon was designed to render optimum performance at f/8 across the entire image area. Due to the optical glasses available at the time of its design, the lens did not quite show the high contrast level typically associated with the high quality optics from Zeiss. In practical terms, this will result in perfectly sharp enlargement up to 8x10 inches. Bigger enlargements might show a certain lack of crispness when inspected very closely. Projection of transparencies, on the other hand, will show no adverse effects, because the projected images usually are not inspected very close up. The same is true with big enlargements when viewed from a more “normal” viewing distance.

The Hologon allowed focusing from 8 inches to infinity. Considering the great depth of field rendered by such a short focal length, one might initially think focusing to be superfluous. But it was proven that the overall performance of the Hologon could be improved if the lens was focused properly.

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15mm Hologon

15mm field of view

Please note: The 15mm field of view images are not separately taken photographs; they were cropped from the original Hologon negatives to present the view of a 50mm lens.

Newer, more sophisticated lens designs have improved the speed of super wide angle lenses and even allow for reflex viewing. Subsequently, the Hologon has long been discontinued. But it deserves credit for having been the first of the super wides, and its unusual design will always give it a special place in the history of lenses for 35mm cameras. Those who own a Hologon can consider themselves lucky indeed.

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15mm Hologon

50mm field of view

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15mm Hologon

50mm field of view

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15mm Hologon

50mm field of view

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