THE LEICA 180mm F/3.4 APO-TELYT-R
Newer and more advanced production
methods have resulted in a relatively large number of lenses with aspherical
elements. This has led to considerable
advances in lens performance. The 50mm F/2 Apo Summicron ASPH is such a
lens. It approaches the limits of what
is physically possible. Performance
wise, this lens is unsurpassed.
However, that isn’t to say that some of
the older Leica lenses are suddenly outdated and undesirable. As a matter of fact, we can go back almost 40
years and still find a lens that is possibly equal in performance to the current
50mm Summicron.
This lens is the 180mm f/3.4 Apo-Telyt-R. It reached the market in 1975. At that time it was no longer a secret that
Leica had developed the lens for the US Navy as part of a high resolution 35mm
camera system.
The system used Leicaflex SL2 cameras,
the standard 35mm Summicron-R, a 75mm f/2 Elcan-R, a 180mm f/3.4 Elcan-R (later
reincarnated as the Apo-Telyt-R), and a 450mm f/5.6 Elcan-R. This system was used by the US Navy starting
in the early 1970s.
Leica 180mm f/3.4 Apo-Telyt-R
One of the problems of lens design is
accurate color correction and the Navy presented Leica with the problems of
developing lenses that could focus more than just the visible spectrum
accurately.
Even today, most of the photographic
lenses have what is referred to as “primary color correction,” where only part
of the visible spectrum is focused at any time.
The solution to the problem lay in the
development of glasses with what are considered “anomalous” properties; the
combination of high refracting indexes with low dispersion.
Such properties are found in
artificially grown crystals; an example is the calcium fluoride elements made
famous in the Canon FL series telephoto lenses.
But such crystals have a very large
temperature coefficient, and elements made from them are both brittle and
extremely soft. The temperature related
expansion of calcium fluoride elements is so great that most lenses made with
them are subject to changes in focal length with temperature changes, and
therefore have no proper infinity stop or distance markings.
The softness of the material also leads
to design constraints. For instance, the
Canon 300mm FL lens has a thin, conventional glass element in front of the
“front” calcium fluoride element, primarily for protective purposes.
Not an ideal situation. Lenses made of these crystal elements demand
extreme care to assure proper performance, and the military considered them
incompatible with the kind of treatment they were likely to receive.
The glass research lab in Wetzlar set out
to develop a glass that had the optical properties of crystals like calcium
fluoride, but without the negative side effects. They did indeed develop such a glass, today
commonly referred to as “apo glass.” It
was/is used in a variety of Leica lenses, including the Apo-Telyt, the 800mm
Telyt-R, and the Noctilux 50mm f/1.
Their designer, Dr. Walter Mandler, was the man whose genius brought us
those lenses, but also the 35mm Summilux, and close to fifty other lenses for
Leica cameras, in addition to lenses for RCA television cameras, IMAX
projectors, and Picker X-ray equipment.
How good are the Elcan lenses,
specifically the Apo Telyt 180mm f/3.4?
While most photographic lenses have a color correction from 400 to a
maximum of 700 nanometers, the Leitz apo glass allows correction up to 900
nanometers. In simple terms, this means
that all colors of the visible spectrum and
infrared are focused in a single plane.
The Apo-Telyt proved to be the best lens
of the set, making it one of the very few lenses for 35mm cameras that do not
require refocusing when used with infrared films or sensors. For instance, when used with an adapter on
the Leica M8, M9. M-E and M Monochrom and with an infrared filter, the lens can
be focused normally and does not require any refocusing to compenmsate for the
infrared focus shift
The US Navy conducted comparison tests
with the 180mm f/2.8 Elmarit-R. These
demonstrate the effects of the apochromatic correction of the Apo-Telyt. Both lenses were tested at f/3.4 with blue,
yellow-green, red and infrared light.
The maximum focus shift of the Apo-Telyt was +/- 0.045mm. The shift of the 180mm f/2.8 Elmarit-R (at
f/3.40 was +/- 0.25mm.
In practical applications, such
correction translated into fantastic sharpness.
Increased resolution is readily apparent, made possible by greatly increased
contrast capabilities.
The Navy test showed that the Kodak 5069
film, developed in H&W 4.5 developer consistently achieved resolution
figures of 600 lines per millimeter. To
make enlargements with this kind of detail required a specially modified Leitz
Focomat II enlarger and lenses.
It is safe to say that regardless of
manufacturer, the Leitz Apo-Telyt-R 180mm f/3.4 is still one of the very best
lenses ever made for 35mm and digital photography.
For more information go to:
MANUFACTURE AND PERFORMANCE OF
PHOTOGRAPHIC LENSES
This article has a lot more information
on the Apo-Telyt and the tests conducted by the US Navy.
That is very impressive. Has any other manufacturer like Canon or Nikon ever offered a lens with that performance level?
ReplyDeleteNone that were ever part of their generally offered line of lenses. Nikon, however, has made some special lenses for NASA. There are no performance data that I am aware of.
DeleteDoes it require special camera equipment to fully take advantage of that performance level?
ReplyDeleteSorry, for some reason I lost several comments on articles yesterday. No special camera equipment is necessary, however, to be able to take full advantage of the performance level of the Apo Telyt, the tolerances used in the manufacture of the camera must be within the performance parameters of the lens. That means, for instance, that the accuracy of the lens to film/sensor distance has to be withing 1/100 mm to stay within the focus shift of the lens. If not, certain performance losses might occur because the lens is seated outside the amount of the focus shift, at which point some of the performance will be lost.
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