100 Years of Carl Zeiss Tessar® - Carl Zeiss, Inc.

AnniversariesFig. 1:Dr. Paul Rudolphthe inventor of theTessar ® lensFig. 2:Cutaway of a Tessar ® and30 cm Tessar f/4.5 lens forIca 13 x 18 cm reflex cameraFig. 3:4.5 x 6 Sonnet with a 7.5 cmTessar ® f/6.3 lensContessa Nettel , Stuttgart,1921100 Years of Carl Zeiss Tessar ® Innovation 11, Carl Zeiss, 2002Exactly 100 years ago, Carl Zeisswas granted a patent for an inventionwhich became the mostfamous camera lens of all times:the Tessar ® lens.Until the death of Carl Zeiss,the company’s founder, in 1888,the firm almost exclusively manufacturedmicroscopes with one exception:the Abbe refractometer.In the early days of the company'shistory, outstanding developmentswere made by Ernst Abbewho was first a scientific colleague,then a partner and finallythe founder of the Carl ZeissFoundation, thus increasingly determiningthe fortunes of thecompany. Ernst Abbe was notonly a scientist, but also an entrepreneur.Currency crises occurringaround 1893 negatively affectedthe export of microscopes whichinduced Abbe to think aboutextending the product line, thusreducing the company’s dependenceon only one product. From1888, Ernst Abbe started to diversifythe product line. Camera lensesbecame a new business division.However, Ernst Abbe alsogranted licenses to companiesoutside Zeiss. This procedureavoided an abrupt growth of thenew division at the expense ofthe other divisions. He deliberatelyaccepted the disclosure of developmentand manufacturingknow-how to competitors.A few highly talented scientistswhich he had employed played amajor role in making this strategy asuccess. Paul Rudolph was one ofthese scientists. He is the father ofsome camera lenses which are stillproduced to this very day. He createdthe Anastigmat camera lens whichwas produced from 1890 and renamedProtar ® in 1900. Paul Rudolphdesigned two further lenses duringthis period, the Planar ® lens – producedfrom 1896 – and the Tessar ®lens which has been produced since1902. The name Tessar gives a clearindication of the structure of the lens:“tessares”, Greek for “four”, indicatesthat the lens consists of fourlens elements.What is the outstanding feature ofTessar ® ? In the early days of photography,pictures were taken in blackand white. Glass plates were the “imagestorage media” used by seriousphotographers. The light sensitivity ofthe emulsions used was so low thatshutter speed was counted in minutes.The preferred lenses at this timewere two-element systems with a lowspeed and rather modest image quality.A few high-speed lenses existedwith an aperture of about f/3.5 whichcost more than a saddle-horse, providedpictures smaller than a postcard,and whose definition was limitedto the center of the image.Paul Rudolph used new types ofoptical glass provided by the JenaerGlaswerk Schott & Genossen: for example,glass types with finer gradingof the refractive indices at a given colordispersion. The use of these typesof glass made it possible to achieve excellentcolor correction, including thecorrection of astigmatism, sphericalaberration and field curvature in thePlanar ® lens. However, the lenses werelarge and heavy. As anti-reflective technologywas still unknown at this time,the pictures also lacked brilliance.Paul Rudolph found an ingenioussolution to solve some of the prob-2lems. The Tessar ® lens belonging to thetype of “Triplet lens” was created. Thedesign using a dispersive elementplaced between two collective elementsresults in anastigmatic imaging.Instead of individual elements, it isalso possible to use cemented components.In this case, the image-sidecomponent consists of a dispersiveand a collective element. The lens withits initial aperture – “speed” – of f/6.3was patented in 1902. The redesignperformed by Ernst Wandersleb in1904 resulted in the Tessar ® f/4.5 lenswhich was available from 1907.32

This was soon followed by an f/3.5version for cinematography and projection.In 1908/1909, Ernst Wanderslebdesigned the precursor to theconvertible lens sets of the Tessar ®lens with an exchangeable front element.Willy Merté’s development resultedin the Tessar ® f/2.8. lens in1932. A year later, the Tele-Tessar ® Klens (f/6.3/180 mm) with its sensationallyhigh speed was introduced forthe Contax ® camera built from 1932.A “quantum leap“ in the image contrastprovided by optical systems resultedfrom the “anti-reflective coating“ inventedby Alexander Smakula at Carl Zeiss,a thin, reflection-reducing, vacuumdepositedlayer. A patent applicationfor this procedure was filed in 1935.The Tessar lens was launched on tothe market in many versions. Highqualitystereo lens pairs were part ofthe Carl Zeiss product spectrum at anearly stage. For example, Paul Frankeand Reinhold Heidecke used preciselypaired 55 mm Tessar f/4.5 lenses in theirfirst Heidoscop stereo camera as earlyas 1920, the year when they foundedtheir company which was later toachieve world renown as “Rollei-Werke Franke & Heidecke”. Worthmentioning is also the 500 mm I.R. –Tessar ® f/5 lens for aerial photographyin the 30 x 30 cm format. An interestingdesign created in 1951, the Zeiss-Ikon Panflex ® mirror box, combinedwith the 115 mm Panflex-Tessar ® f/3.5lens launched in 1953, made it possibleto use the Contax ® viewfindercamera like a reflex camera.Standard lenses like the current45 mm Tessar ® T* f/2.8 lens for theContax reflex camera are generallyachromats featuring correction ofchromatic longitudinal aberration fortwo wavelengths. This also applies tothe Tele-Tessar ® lenses which becameavailable for the 35 mm and the 6 x 6cm formats from 1968. The modernlenses of the Tele-Tessar ® T* type forthe Contax ® and Hasselblad Series200 cameras are also achromats. TheTele-Tessar ® HFT lens is available forthe Rolleiflex System 6000. T* andHFT stand for enhanced transmissionthanks to multilayer coating.Higher demands made on colorcorrection are met by apochromaticlenses which are corrected for threewavelengths. As early as 1923, theApo-Tessar ® lens was the most oftenused lens in reproduction photography.From 1982, a 500 mm Tele-Apotessar ® f/8 lens was provided forthe Hasselblad 550C camera. Thereare now different versions of the Tele-Apotessar ® T* lens for cameras suchas Contax ® , Contax ® 645 Autofocusfrom Yashica and cameras fromHasselblad and Rollei.The image definition and brillianceprovided by the Tessar ® lens resulted inthe slogan “the eagle eye of yourcamera” in 1931. The image-side cementedcomponent was the originalfrom which the “lens logo” was derivedand used for many decades as atrademark of the company. To this day,Carl Zeiss has produced about 5 millionTessar ® lenses for image sizes mea-suring from half a fingernail to thedoor of a room. All over the world,lenses are produced which are basedon the Tessar ® design, some licensedby Carl Zeiss. The result: more than150 million units sold to this day.Dr. Wolfgang Pfeiffer, AalenKornelius Fleischer, Camera Lens Marketingk.fleischer@zeiss.deDr. Dieter Brocksch, Corporate Communications/TechnicalInformationbrocksch@zeiss.deNote:Tessar ® is a registeredtrademarkFig. 4:Contax ® Aria with a 45 mmTessar f/2.8 lens“Star of Vision Award”Ahead of the biggest ophthalmicexhibition in the USA, the “VisionExpo East Award”, pioneeringachievements in the optical industryare awarded prizes. In 2002, thepanel of specialists presented the Starof Vision Award to Carl Zeiss, fora trail-blazing invention made in1935: the anti-reflective coating ofoptical surfaces developed byProf. Alexander Smakula. Since then,the anti-reflective coating has alsoimproved the results obtained withthe Tessar lens as is illustrated by thetwo historic photos taken with andwithout AR coating. It is not unusualfor pioneering inventions to remain inuse for a long time, but it is certainlynot an everyday occurrence for themto be honored with an award manydecades after they have been made.Innovation 11, Carl Zeiss, 2002 33