A History of the Xenon Lens

In the pantheon of fast Double-Gauss lenses from the 20th century, the Sonnar, Biotar, and Planar, are well known. But there’s also a lesser-known lens that is their equal; the Xenon. This lens was invented in 1925 by Dr. Albrecht Wilhelm Tronnier (1902-1982) while he was working for Jos. A. Schneider Optical Works in Bad Kreuznach, Germany, known as Schneider-Kreuznach. And while it is less heralded compared with more popular designs, the Xenon’s history and performance are worth a look (and a shoot).

The sample images in this article were made with my Schneider-Kreuznach Xenon 50mm F/1.9 (for Instamatic Reflex) which was manufactured between 1968-74 in Deckel or DKL mount, but the Xenon has been produced in a variety of lens mounts over the years including Leica thread or screw mount, Alpa, and most commonly M42. The majority of the post-war 50mm F/1.9 lenses are optically identical, only the lens barrels and mount differ. 

Xenon is Schneider-Kreuznach’s appellation for their asymmetric double-Gauss lens design, which resembles Zeiss’ Biotar/Planar/Sonnar lenses. In 1900 Zeiss chose to name their Anastigmatic lens Protar to separate it from competitors and trademarked the name to hamper their rivals. Subsequently all German lens manufacturers followed this practice of giving their lenses pseudo-scientific sounding names to lend them credibility and protect their inventions. 

Tronnier chose to name his lens design Xenon, which derived either from the Xenon atom with atomic number 54, or stemmed from the word Xenos the Greek word for “unknown.” Frankly, I think it most likely that the naming came in a similar way to how modern cars derive their names; for marketing purposes – sounding good and being easy to spell and pronounce. Once the Japanese consolidated their control of lens-making the process of giving names to designs slowed or ceased, and lenses were typically given only a manufacturer’s name and specification designations for focal length and maximum aperture.

Dr. Albrecht Wilhelm Tronnier, Inventor of the Xenon

The Xenon lens was invented by Dr. Albrecht Wilhelm Tronnier (Born 1902 – Died December 1, 1982) while he was chief designer of Jos. A. Schneider Optical Works in Bad Kreuznach, Germany from 1924 to 1936. Sadly, Dr. Tronnier does not share the fame of the other lens designers of his era such as Dr. Willy Walter Merté who invented the Biotar, or Ludwig J. Bertele who invented the Sonnar. But he has every right to fame – he invented the Xenon when he was only twenty-four years old, and then went on to have a remarkable career during which he accumulated 360 lens design patents. 

That the Xenon has been in continuous production by Schneider-Kreuznach from 1925 up to the present day, and the fact that it is still considered one of the best cine lenses in the world, is a testament to the design skills of Dr. Tronnier.

In 1924 Tronnier, then just twenty-two years old, joined Schneider Optik Works in Kreuznach, Germany as their chief lens designer. In the previous year Ludwig J. Bertele and A. Klughardt working at Ernemann had shocked the lens industry with their release of the Ernostar lens, which boasted the then unprecedented speed of F/2 for the 6 x 4.5 cm medium format Ernemann Ermanox plate camera. The speed and capability of the lens revolutionized photography by allowing photographers to shoot indoors and in low light situations. It was used to great effect by photographer Erich Salomon, who could be rightly dubbed the first Paparazzo because the lens allowed him to capture candid indoor photos. 

Tronnier was given the impossible challenge of developing a fast lens to compete with the Ernostar. He used some design elements from the Opic lens invented in 1920 by H.W. Lee of Taylor-Hobson in the United Kingdom. The Opic moderately collapsed the symmetrical structure of the Zeiss Planar from 1896, and reduced spherical, chromatic and field curvature aberration in the symmetrical Gaussian design. Tronnier adopted the asymmetrical design of the Opic, but to be able to achieve his goal he needed to create a six element lens. However, to achieve the desired speed the front elements had to curve, which increased the refractive index and introduced large aberrations from each element. 

Tronnier completed the project three years after starting, in 1925, and patented the Xenon F/2, an asymmetrical Double-Gauss design of six elements in four groups, equivalent to the Opic with German Patent #DE 439556. 

The methods Tronnier used to develop the Xenon, specifically by splitting cemented lenses into single groups and through the use of five to six lens elements, anticipated the solutions for high-speed lenses which are still used to this day. After WWII Tronnier was appointed by the British occupational administration as Chief Designer of Voigtländer. He then designed (or oversaw the design of) numerous lenses, including the Ultron F/2, Nokton F/1.5 and Color-Skopar F/2.8, the Color Heliar F/3.5 for the Bessa II, Ultragon, Skopargon, Dynarex, Skoparex, and the famed APO Lanthar lens.

The Leitz Xenon 

Sadly for Tronnier, before the Xenon could be released to market Ludwig J. Bertele (who at the time had begun working at Zeiss after that brand had absorbed Ernemann) developed the Sonnar lens formula in 1931, which became publicly available as a 5cm F/1.5 lens on the Zeiss Contax I in 1932. The Sonnar was ground-breaking, and the seven elements in three groups design became a great commercial success. 

Leica, who were up and coming competitors to Zeiss’ Contax with the recently released Leica IIIa 35mm camera, needed a fast lens to compete with the Sonnar. So Ernst Leitz engaged Schneider-Kreuznach to create a fast lens. The Leitz-Xenon 5cm F/1.5 lens referencing Taylor-Hobson British patent 373950 and US patent 2019985 which was originally designed as a cinema lens came into production in 1936.  Zeiss’s Sonnar had already captured the market, and the Xenon only sold a fraction of the amount of the Sonnar. 

Interestingly, the first model of the Leitz Summilux 50mm F/1.5 (of 1959) was identical in cross-section to the Xenon/Summarit, but was an improvement over the earlier lenses because of the use of the newly invented high refractive index Lanthanum glass. 

The second version of the Summilux, introduced in 1962, was a redesign of the first version Summilux by Dr. Mandler of E. Leitz Canada in Midland. The modern Leitz Summarit 50mm more closely resembles the design of the Zeiss Biotar. Leitz was not able to offer a lens with significantly greater performance over the Summilux until 2003, when they introduced the Summilux ASPH FLE lens, which incorporated a floating element and exotic glass.

Descendants of the Xenon 

Although the Xenon is less well-known than its competitors, many photographers own a lens which owes its design to it. The Xenon design went on to become the basis for a host of fast lenses made by Japanese lens manufacturers, up to the present day. Here are just a handful of the many lenses that are based on the Xenon design. 

Konica Hexanon 60mm F/1.2 : The Nikon Historical Society Journal number 58 (NHS-58 Journal) relates the interesting story of the origin of many fast lenses developed in Japan following WWII. At that time, the Japanese government requested that the top five lens manufactures in Japan combine their technical expertise to create an ultra-fast lens of F/0.65 or F/0.85 for use in X-ray machines.

Those five optical companies were Fuji Kogaku (Fujica/Fuji), Konica Kogaku, Chiyoda Kogaku (Minolta), Nippon Kogaku (Nikon), and Ohara Kogaku. The project was assisted by the fact that when Japan and Germany had signed the Axis pact in 1940, Adolf Hitler transferred nearly all of the patent rights from Carl Zeiss to the Japanese government. Two results from this government scheme were the Konica Hexanon 60mm F/1.2, and the Nikkor-N 1:1.1 F=5cm, both based on the Xenon design. 

Nikkor-N 1:1.1 F=5cm : In 1930 Tronnier patented an improvement of the Xenon design with three attached rear lenses, an eight element F/1.2 lens (spherical, chromatic and astigmatic corrected). After WWII the design was used by Saburo Murakami at Nikon as the basis for the Nikkor-N 1:1.1 F=5cm with eight elements in six groups. When it was released in 1956 it was the world’s fastest 35mm lens (trivia: Che Guevara owned and used one for reportage).  

Nokton & Ultron 

After WWII Tronnier continued to work on the Xenon design which led to the invention of two other lenses, the Voigtlander Nokton and Ultron lenses. The suffix “on” showed it was a derivative of the Xenon, and this nomenclature continue with the Ultron. Similarly to the Xenon these two designs were used as the basis for a variety of fast lenses in the 1970s. 

Voigtländer Nokton : In 1947 Tronnier used the Xenon as the basis for an upgraded lens called the Nokton. Being very difficult to get a patent in Germany following the war, he patented the lens in Switzerland in 1950. To his original Xenon design Tronnier added a rear lens to increase performance, and the 50mm F/2 lens was first released with the Vito/ Vitomatic/Vitessa cameras. The version for the Voigtländer Prominent is the famed 50mm F/1.5. 

Voigtländer Ultron : The Ultron has been a famed lens since its introduction as the top of the line lens for the Voigtländer Vitessa and Prominent cameras. This original 50mm F/2 version released with the Voigtländer Prominent is reputed to have twice the resolution of competitors like the Leitz Summicron F/2, and Summitar F/2 at 165 lines per millimeter at F/4. 

During the mid 1950s the second generation Ultron was redeveloped using a very early Zuse computer. This lens with seven elements in six groups, the Ultron 1.8/50 was first produced between July 1968 and December 1971, and famously had the highly unusual attribute of a concave front element. This version of the Ultron produced in M42 and Rollei QBM mounts is reputed to be one of the best 50mm lenses ever produced and is highly sought after by collectors. 

Carl Zeiss Planar 50mm F/1.4 : As part of Zeiss’ purchase of Voigtländer AG in 1975, Zeiss came into ownership of Tronnier’s patents. In 1972, Karl-Heinrich Behrens and Erhard Glatzel updated the Xenon design by adding an extra front lens, making it seven elements in six groups. Zeiss marketed this lens as the Carl Zeiss Planar 50mm F/1.4 in Contax Yashica mount, an absolutely stellar lens (which James reviewed here).

Schneider-Kreuznach Xenon 50mm F/1.9 for Instamatic Reflex : Kodak’s Retina series of cameras was a long-running line of premium cameras produced by Kodak AG in Germany. The early folding models had the “Kleinbild” 50mm F/2 Xenon lens, but it wasn’t until the Retina Reflex series was released that the F/1.9 model of the lens appeared. Kodak’s Retina Reflex III with the Xenon 50mm F/1.9 cost $248.50 in 1961, the equivalent adjusted value is $3,622 USD in 2019.  

The Kodak Instamatic Reflex was an SLR made in Germany by Kodak AG from 1968 to 1974. It was one of the last cameras to come out under the famed Retina name and was the most sophisticated cameras ever produced to use 126 Instamatic film. Using the Kodak Retina lens mount, sometimes called Deckel mount or DKL mount the camera’s “kit” lenses were the Schneider-Kreuznach Xenar 45mm F/2.8 and the fast Xenon 50mm F/1.9.

How good is the Xenon?

Being a late model of the Xenon, my lens was in almost brand-new condition, which is quite common because the Retina version came in beautifully designed hard plastic cases which tended to protect them from damage. As with all Schneider-Kreuznach lenses the build quality is tops, epitomizing the workmanship that Germany was famed for. The hardened chrome finish resists wear, and even well-used copies don’t show their age. 

The signature look of the Xenon is a remarkable sharpness across the whole frame, even wide open, and a beautiful, painterly bokeh, as well as the vibrant color rendition for which Schneider lenses are famous. Look at the sharpness, bokeh and vibrant colors of the shots I have taken with my Xenon. I think they speak for themselves. 

I am a big fan of Agfa Ultra Color 100, but sadly it is long discontinued, but ordinary Ektar 100 and the Xenon produces almost the same level of vibrant color.  A good comparison to visualize the bokeh of Xenon is to compare it to that of the Carl Zeiss Jena Biotar 58mm, or its descendant the Helios 44. To me the famed swirly bokeh of theses lenses reminds me of the brushstrokes of a Vincent Van Gogh painting, wild and almost hallucinatory, and definitely not to everyone’s taste. Whereas the Xenon resembles the delicate brush strokes of a Monet. 

I own the DKL version mentioned above, so my opinions are reserved solely for that model, but optically the many versions of the Xenon perform similarly. I’m still lusting after an early M42 version. But the relative disinterest from collectors in this DKL mount version is a benefit to shrewd shoppers. With some time and patience it’s possible to pick up a copy of this legendary lens formula for very little cash.

Buying Tips

As far as trying to buy a good Xenon lens, we can exclude the lenses made for Retina cameras as they aren’t practical everyday shooters. But the Xenon came in a variety of lens mounts Exakta, Praktica, Robot Berning, Rollei QBM, M42 and even Alpa (which tend to be expensive because of the collectability factor). Even more uncommon is the Leitz Xenon 50mm F/1.5 which was produced from 1936 to 1950 in Leica thread mount. Only 6,190 were produced, and buyers of this version will be paying for rarity. 

During the 1950s and ‘60s the Xenon competed against prestigious lenses such as the Steinheil Quinon or Rodenstock Heligon and was on par with both. Both of those now fetch high prices, but you can buy a Xenon for a fraction of the price. The M42 mount is one of the most common, and easily adaptable to mirrorless digital cameras, and many copies in good condition are readily available. 

But the best value for money is the DKL mount version, like mine, because they were produced in large quantities for the Kodak Retina cameras, and DKL mount is not as sought after. These DKL lenses are astonishingly good, and only five to ten percent the cost of a comparable Leitz lens. The one downside is that buyers will need a DKL adapter, but they are readily available, and I would recommend buying the best quality one made by Yeenon. 

The final lens hunting tip I’ll suggest is to look for the camera, not the lens. I bought my lens for $40 USD when I found it mounted to a Kodak Instamatic Reflex camera and told the seller to just keep the camera and send me the lens. Because the Instamatic Reflex takes 126 cartridge film, it is not as popular as the Kodak Retina cameras, and there’s no demand for these models. Through this trick, it’s possible to get a lens with legendary pedigree for an unbelievably low price. Happy hunting. 

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