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Wednesday, November 13, 2024

THE LEITZ (LEICA) GLASS RESEARCH LABORATORY


 
Photo: Marlies Amling

By Heinz Richter

People often wonder if Leica makes their own glass for the manufacture of their lenses.  They used to, as a matter of fact, they operated their own glass research lab where they developed many of the exotic types of glasses that are used in their lenses today.  However, for a relatively small company, that proved to be unsustainable, and they closed the lab as well as their glass manufacturing operation.

The Leitz Glass Laboratory, which operated until 1989, was the driving force of Dr. Gustav Weissenberg, of the Mineralogical Institute of Marburg, Germany.  The Institute grew crystals, and Weissenberg’s idea was for it to create optical glasses as well as to meet the demands by optical designers for high refraction glasses to correct aberrations.  He wanted to replace the highly radioactive thorium oxide in existing glasses with an oxide free of thorium.  So, in 1949, the Leitz brothers established a glass laboratory within their company to pursue Weissenberg’s research.

After lengthy experimentation the glass laboratory discovered that lanthanum oxide offered the best chances for success.  They found that glasses could be created with a refractive index of n 1.7.  However, such glasses could not be made in large quantities because their strong propensity for crystallization made it difficult to prevent crystal grooves, or striae.  Other substances, such as zirconium oxide, yttrium oxide, and tantalum oxide, had to be incorporated to produce more stable high-refraction glasses in large numbers.  Leitz then granted the German company Schott (Schott is part of Zeiss, headquartered in Mainz, Germany) a license to produce the new LaK 9 glass exclusively for Leitz.

Meanwhile, the Leitz optical designers wanted to design lenses that were even faster than f/2, and the dreamed of doubling the speed to f/1.4.  This required glasses with refractive indices close to n 1.8, and for this they had to find the right technology.  Evaporation at the surface of the molten glass while the high temperature in the crucible is being lowered can easily cause striae, which can only be prevented by stirring to produce constant blending of the molten mass.  In order to accomplish this, technicians had to incorporate interference factors, so that one oxide would prevent another from crystallizing.  Laborious experiments led to three new types of Leitz optical glass, with refractive indices of ne 1.80 and ne 1.82 and a dispersion value of ny 45.  These new types of glass made the design of the 50mm f/1.4 Summilux lens possible

 
Platinum crucible

 
Stirring rod

    
Pouring of molten glass

But for glass types with indices of refraction higher than ne 1.8, it was difficult to obtain enough chemicals with sufficient purity at a reasonable cost.  At the time, one kilogram (2.2 lbs.) of 99.99 percent tantalum oxide cost the equivalent of nearly $2000.00 at that time.

In 1966, Leitz introduced the 50mm f/1.2 Noctilux, which incorporated aspherical surfaces.  Then years later, it was producing the 50mm f/1.0 Noctilux , which did not involve aspherical surfaces.  This was made possible by still another new type of optical glass: one with a higher zirconium oxide content.

The company was seeking a lens with a maximum aperture of f/1.2, for which optical glass with a particularly high index of refraction was necessary.  Ultimately, it wanted to double the maximum aperture of the 50mm f/1.4 Summilux lens to f/1.0.  The higher zirconium oxide content permitted production of the 900403 glass with a refractive index of ne 1.9005 and a dispersion value of ny 40.

 
Comparison of optical glasses
The large circled dots indicate glasses used in Leica lenses, the small circled dots indicate Leica glasses not currently in use.  The plain dots indicate glasses from other manufacturers

These developments were not without difficulties, however.  The new lenses utilized glass with a very high melting point of nearly 1600 C (2912 F).  That came close to the melting point of the platinum crucibles.  Also, the shape of the stirring tools in relation to the viscosity of the molten glass was important for the homogenization of the glass.  So, the temperature of the melt in the crucible had to be lowered considerably before it was poured out.  Workers then had to cool the slabs at a carefully controlled rate over 10 to 12 days and nights in order to prevent molecular tension.  Furthermore, the glass was still quite susceptible to crystallization.

Another area of investigation at Leitz was correction of chromatic aberrations in apochromatic lenses with long focal lengths.  Fluorite, grown in single crystals, possesses such anomalous partial dispersion for correction of the fourth color in optical glass.  Leitz competitors like to use these calcium fluorite crystals for lens elements in telephoto lenses, but Leitz did not regard them as suitable for photographic lenses because they have very poor shape retention.  Also, because of their low index of refraction of only ne 1.43, the fluorite crystals require strong curvatures, which are disadvantageous.  Leitz preferred to search for a true glass with an amorphous structure.

 

The company discovered that the fluorites remained stable in metaphosphate suspensions.  By incorporating several fluorites, it was able to optimize the proportions so as to avoid creation of striae during the cooling process.  Eventually it succeeded in developing a true glass with anomalous partial dispersion and a refraction index greater than ne 1.544.  With that, Leitz became the first lens maker to manufacture such lenses.  The 800mm f/6.3 Telyt-S was such a lens [see blog article “Dancing Bear and his Magic Lens”].  It attracted a great deal of attention at the 1972 Olympic Games in Munich.

 

A few years later, with the addition of titanium oxide, Leitz was able to produce glass with an anomalous partial dispersion value of ny 66.6 and a refraction index of 1.544.  This glass was used in the 180mm f/3.4 APO-Telyt, which ranks to this day as one of the best lenses ever made.  Since then, the company has made a large number of lenses with apochromatic correction, and it is creating new ones regularly.

Overall, the Leitz Glass Laboratory developed 35 new glasses from 50,000 experimental melts.  For a time, these glasses were used exclusively in Leica lenses.  Without the laboratory, in fact, most of the modern lenses of the period 1949 to 1989 would not have been possible.  Because of its work, the company produced up to 10 metric tons of glass a year, partially because of close communication between glass researchers and lens designers.  Other large glass manufacturers were often behind Leitz/Leica because optical glass is of only minor importance to them.  Phototropic glasses, construction glasses, television tubes, baby bottles and the like are their real moneymakers.  When these companies do undertake to develop optical glasses, it is only for those for which they anticipate a large demand.  It was the exotic wishes of the Leitz Company that permitted it to develop the glasses it did during the 40 years it held sway in this area.

Once it was possible with new technology to derive maximum performance from optical glasses, however, Leica closed the Leitz Glass Laboratory.  The growing number of glass manufacturers and new methods of processing glass and manufacturing lens elements also made this desirable from a financial standpoint.  However, some of the rare glasses developed by Leitz are still not available to any other lens manufacturer.  Instead Leitz has these glasses made exclusively for them by other companies like Schott, for instance.  Still, the company looks back with pride to the breakthroughs of the researchers and designers at the laboratory.


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Monday, November 11, 2024

ONE OF THE GREATEST LEICA PHOTOGRAPHERS EVER – ERNST HAAS


By Heinz Richter

Ernst Haas (1921–1986) is considered one of the best, most celebrated and influential photographers of the 20th century and considered one of the pioneers of color photography. Haas was born in Vienna in 1921.  He did not become a photographer until after the war. His early work showed Austrian prisoners of war returning home. This brought him to the attention of LIFE magazine. Initially he declined a job offer as staff photographer in order to keep his independence. But an invitation from Robert Capa changed his mind.  Soon after,  Haas joined Magnum in 1949.  There he developed a close associations with Capa, Henri Cartier-Bresson, and Werner Bishof.

In 1951 Haas moved to the United States where he began experimenting with Kodachrome color film.  He soon he became the premier color photographer of the 1950s. In 1953 LIFE magazine published his groundbreaking 24-page color photo essay on New York City. This was the first time such a large color photo feature was published by LIFE. In 1962 a retrospective of his work was the first color photography exhibition held at New York’s Museum of Modern Art.

Ernst Haas using a Leica
Photo: Glenn Beier

Throughout his career, Haas traveled extensively, photographing for LIFE, Vogue, and Look, to name a few of the many influential publications that featured his work  He created four books during his lifetime: The Creation (1971), In America (1975), In Germany (1976), and Himalayan Pilgrimage (1978).

Ernst Haas continued to work until 1986, the year of his death. He has been the subject of numerous museum exhibitions and publications such as Ernst Haas, Color Photography (1989), Ernst Haas in Black and White (1992), and Color Correction (2011). The Ernst Haas Studio, located in New York, continues to manage Haas's legacy, aiding researchers and overseeing all projects related to his work.                                                 
It would be wrong to claim that Ernst Haas used only Leica equipment, but Leicas have definitely been an integral part of his professional life, and many of his famous photographs have been taken with Leica cameras.

When Ernst Haas began photographing in color, he soon created an entirely new approach to color photography by purposely using rather slow shutter speeds to blur the image.  However, as he explained, this was not left to chance.  He used the colors of the scene, and by deliberately blurring the image, he was actually able to create additional colors through the blurred overlap of the various subjects in the scene..  This approach was made especially famous by his photographs of bullfights in Spain.

 

  

 
Obviously, Haas applied his blurring technique to other subjects as well

 
Photograph from his book "The Creation"

The above photograph was later used by Kodak for the Kodak Colorama at Grand Central Station in New York City in 1977.  The original picture was taken with a Leicaflex SL and a 50mm Summicron-R lens on Kodachrome 25.  The finished Colorama consisted of 20 vertical panels of 3 feet width and 18 feet height for a total size of 18 x 60 feet This was the first time a 35mm picture had been used for this project.  It presents a 508 times enlargement to achieve the width of the image.  It was a definite testament of the quality of the film and that of the Leica camera and lens. 

From the book "In America"

Ernst Hass quite often tried to take photographs of ordinary subjects and to present them as an apparently abstract photograph, although, as he explained, that is a contradiction of terms.  A photograph cannot possibly be abstract because a camera can only record actual subject matter.

 
"The Cross"

 
"Snow Lovers"

 Holy Underwear © Ernst Haas
"Holy Underwear"

"Torn Poster"

Ernst Haas had an uncanny ability to find ordinary subjects and by seeing beyond the obvious, was able to create extraordinary photographs.

The first time I met Ernst Haas was at a meeting of the Leica Historical Society of America.  He had been invited as the main speaker for the event.  One thing that struck me immediately was that here was a person who gained international fame with his wonderful color photography and his masterful use of colors, yet he was clothed all in black, black pants, black shirt, black jacket, black tie.  I saw him talking in German to Walter Heun, the former director of the Leica School.   That in itself was quite an interesting conversation.  I knew Walter Heun and, upon noticing me, he introduced me to Ernst Haas.  I was fortunate to meet him again on a couple of other occasions.

There have been many excellent and important photographers, past and present.  Ernst Haas was without question one of the greatest of them all.


     For other articles on this blog please click on Blog Archive in the column to the right

To comment or to read comments please scroll past the ads below.

All ads present items of interest to Leica owners.

_______________________________________________________________________

EDDYCAM - the first and only ergonomic elk-skin camera strap     
 www.eddycam.com        

      


Click on image to enlarge
Please make payment via PayPal to GMP Photography

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Please make payment via PayPal to GMP Photography

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