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A Comprehensive Guide to Camera Lens Design and Zeiss Nomenclature

The German optical systems manufacturer, Carl Zeiss, has had a 168 year legacy in creating some of the world’s best lenses. In 2011, H.H. Nasse wrote a series of technical papers for Carl Zeiss detailing their modern lens history and genealogy. In his three part series, he discussed 5 lens designed that changed the world. They are the Planar, the Tessar, the Biogon, the Distagon, and the Hologon (click on these links to download the original PDF files).

lenscutaway
Zeiss Planar 100mm f/2 (left); Zeiss Planar 85mm f/1.4 (center); Zeiss CP.2 25mm f/2.9 Cine Lens (right)

While very detailed and technical, it is a difficult read for your average Joe. That’s why, we have repackaged the information in a more reader friendly format and filled in some holes with our cited research (such as adding the missing Sonnar lens). That being said, I still recommend you read Nasse’s original papers after you read this article. They are filled with interesting tidbits about optics and engineering.


Zeiss Normal and Telephoto Designs

A normal/standard lens means its focal length is about the diagonal length of the image capturing area. For 35mm film and Full Frame cameras, that translates to 24x36mm with a diagonal of 43.3mm. This means, lenses with focal lengths near 43.3mm can be considered normal lenses. We usually consider lenses between 35mm – 60mm as normal lenses.

Planar (1896)
Planar_1896
The symmetrical design places the aperture (represented by the vertical line) between the two groups of elements, allowing for wider apertures than other designs. The 8 air-to-glass surfaces, unless effectively coated, reduce contrast and introduce flaring and ghosting.

This legendary Zeiss design trademarked Planar (also known as Biotar or Biometar in E. Germany’s Carl Zeiss Jena) is derived from, and suggests, a “plane/flat” field curvature. Most of the world’s fastest lenses today are derivatives of the Planar design, including:

  1. The $11,000 Leica 50mm f/0.95 Noctilux
  2. The ultramodern Zeiss Otus 85mm f/1.4
  3. The fastest lens in the world, the Zeiss 50mm f/0.7 Stanley Kubrick used in the movie Barry Lyndon for its candlelit dinner table scene and NASA’s Apollo Program used to photograph the dark side of the moon.

In fact, every 50mm prime ever made by any manufacturer are essentially modified Planar designs.

nikon f2 cutaway
A cutaway of the Nikon F2 film SLR sporting a Nikkor 50mm f/1.4 in classic Planar design.

Advantages

  1. The symmetrical grouping allows for large aperture designs (f/2 or larger).
  2. A very flat field curvature which leads to sharpness across the entire image plane.
  3. Well controlled chromatic aberrations

Disadvantages

  1. More expensive to produce and heavier than Tessar designs
  2. The many air-to-glass surfaces require effective lens coatings to reduce flaring, ghosting, and to improve contrast.
  3. Prone to astigmatisms.

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