Tessar

Cross-section of a 50mm f2.8 Tessar, with front element on the left. (for 35mm, M42 fitting)

The Tessar is a camera lens designed by Dr. Paul Rudolph, working for the Carl Zeiss Jena company, in 1902. It is normally used as a standard lens, and versions of it have been fitted to many millions of cameras.

The design consists of four elements in three groups; the front element is positive, bi-convex (with the rear almost flat), the central a negative bi-concave and, following an aperture, at the rear is a cemented doublet of plano-concave and a bi-convex elements. Though often referred to as a "modified Cooke triplet", the Tessar is actually a development of Rudolph's 1899 Unar (4 element in 4 groups) lens, itself a development of Rudolph's 1890 Zeiss Anastigmat (4 elements in 2 groups) lens.

Cut-away diagram of a Tessar

Tessar on Ikonta

The original design had a maximum aperture of f/6.3, but the developments in design allowed f/2.8 by 1930.

In addition to production by Carl Zeiss, the Tessar name and design (under license) was used in the production of numerous lenses by Bausch & Lomb (Rochester), Ross (London) and Krauss (Paris).

The Tessar design has been widely copied by nearly all major optics companies.
A very partial list includes:

Agfa Solinar
Asahi/Pentax Macro-Takumar 50mm f/4
Bausch & Lomb Tessar (under license)
Canon 38mm FLP, 50mm f/2.8 and f/3.5 RF lenses, 50mm FL f/3.5
Dallmeyer Dalmac, Perfac, Serrac
Ernemann Ernon
FED/KMZ Industar
Ilex Paragon
Kodak Ektar
Konica Macro-Hexanon AR 55 mm f/3.5
Krauss-Zeiss Tessar (under license)
Leitz Elmar
Mamiya Press lenses - 100mm f/3.5, 127mm f/4.7, 150mm f/5.6
Meyer Primotar
Minolta Rokkor TLR
Minox Minoxar
Nikon 45mm GN Nikkor, El-Nikkor 50mm f/4
Olympus in many of their compact cameras including the Trip 35 (40mm f/2.8) and mju series.
Plaubel Anticomar
Rodenstock Ysar, Rogonar
Ross Xtralux
Ross Tessar (under license)
Schneider Xenar, Comparon
Taylor & Hobson Apotal, Ental
Voigtlander Heliostigmat, Skopar
Wollensak Raptar
Yashica Yashinon TLR

Sources

• Rudolf Kingslake, A History of the Photographic Lens, Academic Press, 1989