A recent question about the naming scheme adopted for Carl Zeiss lenses encouraged me to do a little research. So I wrote the first version of this article... but then I couldn't stop reading about lens design! So now you can enjoy an entire series by clicking on the banner above.
Creative names like Planar, Sonnar, and Tessar were initially used to describe families of optical designs. But later they were used for marketing reasons, so the original meanings were not always preserved.
I now have more detailed articles on the development of lenses in the nineteenth century and those that used the symmetrical pattern. This article repeats some of that information, but from the perspective of Carl Zeiss offerings, in particular the Contax-Yashica line. (Since these are personal favourites.)
The first Planar lens was designed by Paul Rudolph in 1896 using a symmetrical arrangement of six elements in four groups. This was derived from the four-element "double Gauss" design created by Alvan Graham Clark in 1888. But by adding two more pieces of glass, Rudolph was able to lower field curvature and distortion. Hence the name, derived from "plane".
In 1927 Willy Merté tweaked the Planar formula in order to create a series of lenses with unusually large apertures for the time (f/2 and f/1.4). These were named Biotar, the prefix referring to the dynamic photography possible with high speeds (nothing to do with biology).
Many subsequent normal to short telephoto (50-135mm focal length) lenses derive from this work. However the West German branch of Carl Zeiss retained the Planar naming to distinguish themselves from their East German counterparts in Jena.
Here are some examples from the Carl Zeiss line for Contax-Yashica mount, with their formulas indicated:
- Planar T* 50mm f/1.4 (7 in 6)
- Planar T* 50mm f/1.7 (7 in 6)
- Planar T* 85mm f/1.4 (6 in 5)
- Planar T* 100mm f/2.0 (6 in 5)
- Planar T* 135mm f/2.0 (5 in 5)
There are two variants of this naming. Some old models are called S-Planar to indicate that these are optimised for close-up use only. Subsequent Makro-Planar lenses also have high magnification but do not sacrifice distance performance for close-up performance. In the Contax-Yashica line we have:
- Makro-Planar T* 60mm f/2.8 (6 in 4)
- Makro-Planar T* 100mm f/2.8 (7 in 7)
Paul Rudolph's next innovation came in 1902. He took aspects from two previous designs, Unar and Protar, to create the Tessar, a compact and inexpensive design. The name derives from the Greek word for "four", the number of lens elements. The Contax-Yashica system includes the Tessar T* 45mm f/2.8 (4 elements in 3 groups), which is typically slower than other available normals.
The telephoto lenses named Tele-Tessar have more than four elements and bear the Tessar label for marketing purposes only. Those with better chromatic aberration correction were named Apotessar.
- Aposonnar T* 200mm f/2 (11 in 9)
- Tele-Tessar T* 200mm f/3.5 (6 in 5)
- Tele-Tessar T* 200mm f/4 (6 in 5)
- Tele-Apotessar T* 300mm f/2.8 (8 in 7)
- Tele-Tessar T* 300mm f/4 (5 in 5)
The third main Zeiss design line is the Sonnar, invented by Ludwig Bertele. The name derives from the German "Sonne" meaning "sun". This indicated the bright aperture provided by the 50mm f/2 in 1929. But in the Contax line the Planars are the fast lenses while the Sonnars instead balance compact size and high image quality at a lower price.
- Sonnar T* 85mm f/2.8 (5 in 4)
- Sonnar T* 100mm f/3.5 (5 in 4)
- Sonnar T* 135mm f/2.8 (5 in 4)
At one time even a 35mm focal length was considered "wide" but today designers push the limits of what is possible. Obtaining a wide field of view presents an intriguing engineering problem due to the increasingly oblique incident light rays, which must be bent a great deal more than light in a normal lens. If previous designs are adapted, the final lens element ends up ever-closer to the camera body, or indeed projecting inside it altogether!
This was the approach taken for Biogon lenses. The physical extent meant that these were suitable only for systems without mechanisms in front of the film plane. The first Biogon, designed by Ludwig Bertele in 1936, was a 35mm f/2.8 for the Contax rangefinder system. The suffix “gon” derives from the Greek word for angle and signifies a wide angle lens.
In 1966 the unusual Hologon 16 mm extreme wide angle was released for the Contax G system. The prefix derives from the Greek “holos”, meaning “everything” or “complete”.
SLRs required a novel design since the lens mechanism could not encroach backwards to the mirror assembly. The solution was to place a large negative element in front of the standard lens assemblage. This breakthrough was simultaneously developed in two labs. Pierre Angénieux named the result retrofocus while Harry Zoellner at Carl Zeiss Jena named theirs Flektogon.
The separation of West and East Germany again necessitated new nomenclature. Carl Zeiss in Oberkochen created their first Distagon in 1952. At this time manual calculations were made for all optics. This precluded wide-angle lenses from being both fast and free from distortion, coma, and lateral chromatic aberration. But them the computer-aided design revolution in the mid-1970s made possible incredible lenses for Contax SLR.
- Distagon T* 15mm f/3.5 (13 in 12)
- Distagon T* 18mm f/4 (10 in 9)
- Distagon T* 21mm f/2.8 (15 in 13)
- Distagon T* 25mm f/2.8 (8 in 7)
- Distagon T* 28mm f/2 (9 in 8)
- Distagon T* 28mm f/2.8 (7 in 7)
- Distagon T* 35mm f/1.4 (9 in 8)
- Distagon T* 35mm f/2.8 (6 in 6)
The best of these is acknowledged to be the Distagon 21mm f/2.8, designed by Karl-Heinz Schuster in 1992. Truly a no-holds-barred design with 15 elements!
Next we have the F-Distagon, which indicates a non-rectilinear geometry: "F" for fish-eye.
- F-Distagon T* 16mm f/2.8 (8 in 7)
Finally there are PC-Distagons, the prefix standing for "perspective correction". Such lenses project a larger image circle than strictly required for the 135 format. Mechanics are provided for tilt and/or shift functionality, providing some of the functionality of a large format camera.
- PC-Distagon T* 35mm f/2.8 (9 in 9)
Please check out the remainder of the lens design series.
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