Friday, August 14, 2015

The Eye of the Eagle

The Talented Tessar

The reason for this post is that I realised how many of my cameras have lenses that are either Tessar or copies of that lens design. The Schneider Xenar, the Ross Xpress on the Ensign 1620 also the Fuji 150W that I use for large format; obviously the lens on the Rollieflex T and the Tessar on the Zeiss Ikon and Rollei 35T.
Back in the distant days where most photographers used glass plates and large wooden cameras the most common lens was of the Cooke triplet type. 
Complex lens design was expensive and because designers needed to limit the amount of air-glass surfaces to aid light transmission and keep down flare, correction of aberrations was very difficult to achieve.
So in 1902  when Paul Rudolph's Tessar design was put on the market by Zeiss it quickly established itself as a standard for others to emulate and earned itself the nickname 'Adlerauge' (Eagle eye). The four element design carefully mixed both high and low refractive glass and followed it with a cemented pair which reduced aberrations compared to the triplet designs.
One of the things I like most about the design is the higher contrast due to fewer elements, stopped down a couple of stops and they can compete with later Planar (5 and 6 element) designs even in corner sharpness.
Tessar types remained the standard by which others were judged until the 1950's when lens coatings made multi element lenses practical with their better correction and faster apertures.

Tessar f3,5 Rolleiflex T
Don't underestimate the humble Tessar it is a very capable lens capable of rendering wonderful images.

The Classic 150 f6.3 with 'modern' coating.
Over the last hundred years the Tessar has found itself on many iconic camera bodies and has been re computed to allow for both wide and telephoto versions; hopefully it will remain a useful design for many years to come.

No comments: