C.P. Goerz Berlin Dopp-Anastigmaat
Serie III Dagor.
This is one of the most celebrated lens design ever. More than one hundred years after its introduction it is still a very usable lens. It was in 1982 that a mathematician Emil von Hoegh, 27 years old, proposed to Zeiss this double anastigmat consisting of two triplets symmetrically arranged around the f stop. Zeiss was not interested, maybe because two years earlier they had launched their own anastigmat. So Emil took it to the also very young firm Goerz in Berlin. Only four years old, Goerz was producing a Rapid Rectilinear lens called Lynkeioskop, one of the best RR versions. That was the beginning of a huge success. By 1895 some 30.000 had been already sold. The name Dagor was adopted only in 1904 and the design was licensed to almost every lens maker ever since.
It is a convertible lens. That means one can use only one cell placed behind the iris. In that case the combined foci is multiplied by 1,73, but as a trade off there is a significant loss in luminosity.
Most of the above information I researched on "A history of the photographic lens" by Rudolf Kingslake, Academic Press Inc. ISBN 0-12-408640-3. It is an excellent source for understanding the genealogy of most of the lenses ever produced and the problems associated to lens construction.
If you want something online: download the "A Lens Collector Vade Mecum" it is only 15,99 USD and an invaluable source of information. Go to: Lens Vade Mecum It has more than 700 pages with thousands of lenses description, pictures and diagrams.
This Dagor, is from 1911. I bought it in a shoe box together with a Voigtlander Orthoscop from 1858, a Tessar also from 1911 and a Rodenstock Rapid Aplanat #2 from 1910/20. Also some parts of rollerblind shutters and lens elements, that I could not identify, were in the pack. The origin was Santos, a harbor city, 60 Km from Sao Paulo. I tried to trace it back, tried to know to whom in belonged, but the seller, having an antique shop there, could not remember how it all arrived to his hands.
These figures indicating aperture are not the familiar series we are used to see in 35 mm cameras. Goerz used a special scale. In the chart below we can see the equivalents to the system using 4 - 5.6 - 8 - 11 - 16 - 22 - 32 - 45....
The 4,5 (that is not in the chart) means 6.8. In the lens ring it is marked 1:6,8 but as the scale shows it as 4,5 I started to wonder if the cells would have been mounted in a barrel afterwards. But note in the picture below that the serial number is the same engraved on the barrel and on the cells.
So f6,8 or 1:6,8 is the lager aperture for this lens. The following figures, even in this Goerz scale, are very close to the regular series of f stops.
The next 3 pictures are from the Photo Club de Paris magazine in 1899. The name Dagor was not used yet. It was referred as Double Anastigmat Goerz. If you want an explanation of what problem the Anastigmats solved, go to my page about the Ross Protar VIIa
Some contemporaneous ads from the other side of the Atlantic...
Adversing in Photominiature April 1899
Adversing in Photominiature December 1909
Adversing in Photominiature Feb 1900
The following reproductions from Goerz catalogs, and a lot more from other lens/camera makers, you can find at Camera Eccentric website. Excellent online source.
These are both from the 1913 Goerz catalog.
The three above from the 1940 catalog
The next picture is a zoom into Felipe s left eye. You can compare with the whole picture made in a 4x5 negative by clicking the thumbnail below. The film was Tri-X shot as 320 ASA, aperture was equivalent to f16, developed 8 minutes in 510 Pyro at 23 Celsius. It gives an idea of Dagors capability in rendering fine details.
But if you want to check a serious experience that definitely prove it, go to:
Lawrence Panoramic Camera Project.
You will see a Dagor 19 inches there, and the result one can still reach with a lens from 1905.