Peter Karbe: The Modest Genius Behind Leica’s Optical Supremacy

A brilliant innovator who knows he’s standing on the shoulders of giants

By Jason Schneider

Peter Karbe, Portrait by Alan Weinshel

I first had the privilege of sitting down with Peter Karbe at Photokina 1996, and I was deeply impressed with his insight, candor, and understated charm. These qualities were undiminished when I last chatted with him about 5 years later in 2001. The very first question I posed was, in retrospect, a tad generic, but the amazing response it elicited encapsulates the essence of what sets Leica apart. “How do you go about designing Leica lenses?” I asked. To paraphrase Karbe’s response, “We start by carefully evaluating comparable designs created by our great predecessors, assessing their strengths and weaknesses, and formulating plans for moving the concept forward in terms of real-world performance.  Unlike other companies, Leica seldom starts with a clean sheet of paper—we create new lenses in the Leica tradition. Of course, we use advanced computers for efficient optical calculations, and we make full use of the latest glass types, aspheric surfaces, and state-of-the-art production methods. But the actual lens designing process at Leica is essentially evolutionary; bringing the best of the past forward into the future is part of the proud Leica heritage.”

The depth of Peter Karbe’s devotion to the Leica legacy is revealed in these poignant and humble lines honoring his great predecessor Dr. Walter Mandler, written upon his death in 2005: "I can readily say that Dr. Mandler was one of the great optical designers at Leitz and that his work constituted a major contribution to the success of the Leica M rangefinder camera. Dr. Mandler was clearly ahead of his times with his developments. That is proven by the numerous optical computations that still have lost nothing in terms of current relevance. Among them is the 50 mm f/1 Noctilux-M lens that he designed. Today, many publications still refer to his work, notably the landmark 50 mm f/2 Summicron-M lens. And there are numerous other examples that prove how important his work was for the evolution of photographic optics in general and for the evolution of photography at Leitz. While I was writing these lines, it occurred to me that that I am not qualified to render a judgment of Dr. Mandler."

Schneider’s second colloquy with Peter Karbe

While all lens manufacturers, including Leica, now employ the latest ray tracing and computerized optimization programs to speed up the lens designing process, ultimately it is the non-quantifiable human elements that make Leica lenses world-renowned. With the announcement of the Noctilux-M 50mm f/0.95 ASPH and the Summilux-M 21mm and 24mm f/1.4 ASPH, the fastest lenses in their respective focal lengths, this was an opportune time to get the story straight from the man who spearheaded all these optical achievements.

One of the first spectacular results of Leica’s unique design philosophy is the Leica Summilux-M 50mm f/1.4 ASPH., the best performing 50mm f/1.4 lens ever tested by Popular Photography magazine. To gather all the details behind the decade-long gestation process that resulted in this remarkable lens, we interviewed Peter Karbe, director of optics development, Leica Camera AG.
Schneider: When did you first get the idea of developing the Summilux-M 50mm f/1.4 ASPH, and what were your main objectives in doing so?
Karbe: The idea of developing this lens was born during the first production of the current Summilux 35 ASPH (1993). The previous Summilux 50mm f/1.4, designed by Dr. Mandler, had been produced for 30 years and was widely esteemed as a very good high-speed normal lens. Nevertheless, from the technical standpoint of optical design we were aware of its weak points: low contrast over the imaging field due to oblique spherical aberration, and curvature of field and chromatic aberration (on- and off-axis). The main objectives for the new optical design were therefore the reduction of these aberrations. A very challenging constraint on the overall design was to achieve all these laudable objectives without increasing the size of the lens.

Schneider: Which existing 50mm f/1.4 lenses had imaging characteristics you wished to integrate into your new design, what were they, and how did you seek to combine these characteristics in a synergistic way?
Karbe: In former times Leitz Wetzlar tried to construct improved high-speed 50mm lenses by incorporating aspherical elements into the design (e.g., the Noctilux 50mm f/1.2). However, Leitz abandoned this concept due to the extreme difficulty and cost entailed in producing glass aspherical elements by traditional grinding methods at that time. The new Summilux 35mm f/1.4 ASPH was the first lens we produced using a molded aspherical lens element. And significantly it was also the first aspherical lens delivering the highest level of optical performance that we were able to produce economically at a profit.
Understandably, I tried to adopt the successful optical design concept of the Summilux 35mm f/1.4 ASPH for the new Summilux 50mm f/1.4 ASPH. However, it was not possible to adopt the concept in total. Due to the structure of the first optical group of the 35mm Summilux (the first surface has a concave shape) the ray bundle would inevitably be enlarged (widened). This would have enlarged the dimensions of the 50mm lens to an unacceptable degree. As a result, the Summilux 50mm f/1.4 ASPH combines aspects of the Double Gauss (DG)-Type and the Summilux 35mm ASPH. Specifically, its front group looks like a DG-Type and the rear group looks like the one in the Summilux 35mm f/1.4 ASPH. Happily, this compromise proved effective and the Summilux 50mm f/1.4 ASPH. performs quite well.

Thoughts & Observations: Camera Lenses

“I’ve been at Leica for more than 38 years now, and I was in optical design for a long time. I was head of a development department, but for the past three years, I’ve been more of an internal consultant. I gave up my responsibility for development, and I stepped in to a certain role in terms of assistance. I assist projects that need me to help or advise them. I do presentations and explain what is so special at Leica optics, and I do research; I name it research in the history of Leica optics. And then I explain how we could improve our optics, a step-by-step evolution, various steps.

When it comes to designing camera lenses, Karbe has created some of the best in the world. Since 1986, Karbe has been in optics development — first at Wild Leitz, then from 1992, at Leica Camera. Today he oversees much more than the design and development of Leica’s optical systems, and he’s credited for the creation of many of the current M lenses including the following:

An incomplete list of Leica lenses designed by Peter Karbe:

APO-Summicron 50mm f/2 ASPH.

APO-Summicron 35mm f/2 ASPH.

APO-Summicron 75mm f/2 ASPH.

Noctilux-M 50mm f/0.95 ASPH.

Noctilux-M 75mm f/1.25 ASPH.

Summilux-M 21mm f/1.4 ASPH/

Summilux-M 24mm f/1.4 ASPH.

Summilux-M 35mm f/1.4 ASPH. FLE

Summilux-M 50mm f/1.4 ASPH.

Summilux-M 90mm f/1.5 ASPH.

All Leica SL APO Prime Lenses

All Leica TL Prime Lenses

The APO-Summicron 35mm f/2 ASPH. is the fourth APO lens in the Summicron line. There’s the 90, 75, 50 and the 35; the 35 was introduced to the market in 2021. This has the latest status of performance, the highest performance in a very compact size with all the technologies we could implement. And compared to the SL lenses, the SL APO Summicron line is on the highest level. And this M-Summicron delivers that performance, but in a very, very small size. This is significant because with the 60MP Leica M11 you can see the power of this lens. It’s not the lens or the camera alone, but both together. It’s a very good balance between the performance of the lens and the camera.

The APO-Summicron 35mm f/2 ASPH. was a technological milestone because it was the first time we produced and implemented molded aspheric elements and surfaces at Leica. This technology was mainly developed and used in Japan, but we took it over. A vendor in Japan initially provided aspherical lens elements, and with this development and the implementation of this ASPH technology we could move into the aspherical era ourselves very successfully.

One of the great treasures of Leica is the huge data base we have from the past. It’s the biggest treasure you can imagine for designers. First, you have a look at what we did up till now, and where the pros and cons are. And then you try to keep the pros and try to eliminate the cons. This is an evolutionary process. We also look at patterns, for example, what others are doing. Copying something good is not a problem, but first we need to define the target. What do we want? For example, if there is a lens with the same focal length and the same f/number, what performance level are we aiming for in the future? What do we need, and where do we want to go? Above all, lens design at Leica is a dynamic process, and in the end it’s that flexibility that allows us to maintain Leica’s unique position at the pinnacle optical superiority.

For a brilliant, incisive, and engaging historical presentation on the history and development of the Leica by Peter Karbe, please click on the live link below. You will come away with the realization that Peter Karbe is not only one of today’s  greatest lens designers, but also a true Renaissance Man.