Ludwig Bertele

Ludwig Jakob Bertele
Born	(1900-12-25)25 December 1900 Munich, Germany
Died	16 November 1985(1985-11-16) (aged 84) Wildhaus, Switzerland
Occupation(s)	optics engineer, optics constructor

Ludwig Jakob Bertele (25 December 1900 – 16 November 1985) was a German optics constructor. His developments received universal recognition and serve as a basis for considerable part of the optical designs used today.

Biography

Ludwig Jakob Bertele was born 25 December 1900 in Munich, to an architect’s family.

In 1916 he began to work as an assistant of optics designer in Rodenstock firm in Munich. In 1919 he went to Dresden to work in Ernemann Company (Krupp-Ernemann Kinoapparate AG). He worked there under the supervision of August Klughardt as designer of optics.

In 1919 Ludwig Bertele started to develop a type of optical scheme, subsequently known as Ernostar. He has taken for a basis an optical scheme of cinema lens Ultrastigmat, a modified triplet, which was calculated by Charles C. Minor in 1916 and being produced by Gundlach Company. The main purpose was the increasing of light-gathering power and diminution of aberration.

In 1923, after four years of intensive efforts, he has patented his first ultra high-aperture objective Ernostar f/2, its successive versions followed until 1926. That lens was fitted to the Ermanox camera, which was specially developed for photo reportage. This was the first camera having sufficient speed and image quality for candid photography in available light conditions. The pictures of prominent political figures taken with it by Erich Salomon are widely known.

After the foundation of Zeiss Ikon in 1926, as a result of integration of companies ICA (Internationale Camera Actiengesellschaft), Optische Anstalt CP Goerz, Contessa-Nettel and Ernemann-Werke with Carl Zeiss, Ludwig Bertele continued his work in Dresden except for a short trip to United States in 1929. An experimental optical workshop was given at the disposal of Bertele. That shop made all examples and prototypes of Bertele's calculations. Every lens got a unique five-cipher number; often a current number of the variant was also engraved.

In the late 1920s Bertele began the development of a series of excellent lenses, based generally on the second Ernostar type, which was developed in 1924 (i.e., each lens had a single positive element in front of it followed by a thick negative meniscus-shaped component, with a positive element behind). In 1931, the first example of such lenses appeared. It received the name Sonnar.

This lens consisted of seven elements in three groups with a maximum aperture of f/2. The main difference from his predecessor Ernostar was a lesser number of optical groups and therefore lesser light dispersion and higher contrast. Those lenses proved extraordinarily successful and got high marks from specialists.

In 1932 a Sonnar f/1.5 appeared, which was fitted to Zeiss Ikon's 35 mm Contax cameras. with Sonnar versions following with focal lengths from 50 to 300 mm been developed until 1940.

Around 1934, Bertele, having taken the scheme of Sonnar as a basis, created the first wide-angle lens Biogon with a 60° viewing angle.

In 1935, Ludwig Bertele calculated the Sonnar 180mm/2.8 on the occasion of the XI summer Olympic Games of 1936 in Berlin - a fabulous lens, which made an image of highest quality with beautiful bokeh. This lens has been appreciated by photographers and collectors up to now.

Between 1943 and 1945, Ludwig Bertele was working in Steinheil firm, situated in Munich. That firm worked for Imperial Ministry of aviation.

As Zeiss in Dresden and Jena had become part of the Soviet Zone of Occupation in 1945, they were required to transfer these designs as well as machinery and staff for training to Russia and the Ukraine, where all Sonnars were produced in vast nu mbers under the "Jupiter" designation, constituting by far the most desirable optical products from behind the Iron Curtain until this day. The East and West German Zeiss production was tiny by comparison, while Ludwig Bertele, fortunately in absence, had become the most significant optical designer of the former Soviet Union for over four decades.

In 1946, he moved to Switzerland, where he founded an optical bureau and started to work in Wild Heerbrugg Company (now Leica Geosystems) in the field of photogrammetry and geodesic devices. In 1950 he created an aerial 90° viewing-angle lens Aviogon, which was free from optical aberrations. Distortion was less than 10 µm at any point of the image field, and the resolution at F/4.5 was excellent. The new lens quickly replaced the Topogon and Metrogon as the standard lens for aerial photography and photogrammetry. This lens, as well as 120° Super Aviogon, which appeared in 1956, won a great number of prizes and merited general recognition.

At the same time he computed new optical designs for Carl Zeiss in Oberkochen. Thus, a Biogon with 90° viewing-angle appeared in 1954. This new design was the basis of ultra wide-angle lenses, such as Biogon F/4.5 21 mm 1954 for Contax; Biogon F/4.5 38 mm 1954 for Hasselblad; Biogon F/4.5 53 mm and Biogon F/4.5 75 mm 1955 for Linhof. In addition to this he developed objectives for Schacht firm and got special tasks for computations of oculars etc.

He left the firm in 1956, continuing his own research and giving consultations. In 1959, he was awarded rank of honorable Doctor of Philosophy of Zurich University and he appraised it greatly.

Having retired in 1973, Ludwig Bertele continued to work a lot. He received his last patent in 1976.

In his last years he lived in the small town Wildhaus in canton St. Gallen in Switzerland.

He died on 16 November 1985.

Interesting facts

• Name Sonnar was derived from German word “Sonne” (Sun).
• It is interesting to note that the name Sonnar had been used previously by the Contessa Company for one of their folding cameras and for the Tessar-type lens fitted to it. After Contessa became part of Zeiss Ikon the name Sonnar became Zeiss’s property.
• Optical scheme Ernostar, developed by Ludwig Bertele, serves as a basis for lens Canon EF 135mm F/2.0 L, which is very popular among portrait photographers. The Sonnar scheme is also used in the Sony Carl Zeiss Sonnar T* 135/1.8 ZA lens, which is being produced for Sony A-mount SLR cameras.

Bibliography

• Hartmut Thiele. Entwicklung und Beschreibung der Photoobjektive und ihre Erfinder; Carl Zeiss Jena, 2. Auflage mit erweiterten Tabellen, Privatdruck München 2007.
• Rudolf Kingslake. A history of photographic lens. Academic Press ISBN 0-12-408640-3, San Diego, USA 1989.