Erwin Puts’ latest volume explores the progression of Leica 50mm lens design from the original Anastigmat/ Elmax/Elmar lenses of the Leica I to the most recent optical masterpiece from Leica, the APO-Summicron-M 1:2/50 mm ASPH. Erwin presents a thorough view of the entire process. He explains optical theory, methods of lens design, ray tracing, aberrations, how to evaluate lens performance and its relationship to image quality, etc. to name a few of the topics addressed in this book. To say Erwin’s explanations are quite thorough would be an understatement. This is a complex subject which demands equally complex explanations to fully understand the given subject matter. The reader needs to devote the proper amount of time to this book to fully benefit from the insights it has to offer. Not exactly the kind of book to be described as light reading.
I have only had the book for a few weeks, so I will look at some of the highlights contained in the book. To read the book cover to cover would require quite a bit more time than that I have available to write my review! If you are an optical designer, I’m sure most of the information on optical theory and design will be second nature. However, to us mere mortals, there is some real heavy going here.
Max Berek’s name is not quite as well-known as that of Oskar Barnack in the story of the Leica, but he certainly played a critical role in the Leica’s success. Berek was primarily concerned with the design of microscope optics at Leitz, working extensively with the new field of polarized microscopy. In the world of optics, camera lenses are considered to be less of a challenge to design than microscope objectives, due to the smaller size of the microscope objective and higher levels of precision required in their manufacture. Puts gives some valuable insight into the task faced by Berek to design the first lens for the new Leica camera. He explains how Berek arrived at the focal length of 51.9mm and an angle of view of 45 degrees were chosen for the new camera’s lens. This was done for some very pragmatic reasons according to Puts. The aperture of f/3.5 was considered to be the fastest practical aperture to use on the new camera. This was considered a relatively fast lens at the turn of the 20th century, given the very slow film speed of the emulsions in use at that time. The angle of view most likely had to do with Berek’s choice of panchromatic correction for his lens in a time when most lenses were corrected for orthochromatic emulsions. The panchromatic correction also had the bonus of being able to work well with the color film emulsions which would be introduced many years later. The narrower angle of view helped limit aberrations and cropped out the relatively soft edges of the Elmar design, a shortcoming Berek was well aware of. The choice of an f/3.5 aperture also provided an extended depth of field and an essential safety factor for the relatively inexperienced photographers of that time in dealing with the new miniature format. Today we take the integrated viewfinder/rangefinder for granted, but with the Leica I, the user had no such luxury. The camera was scale focused, either by guesstimating the distance to subject and setting it on the lens, or using an auxiliary focusing device mounted in the accessory shoe such as the FOFER and transferring the indicated distance onto the lens. Even if the user misjudged the correct distance, he was assured of high quality images. As a new product, it was essential that the Leica succeed in the marketplace, and the new user should not be disappointed with the results while he was experimenting and learning. These are typical of the insights Erwin provides throughout the book, which gives the reader a real appreciation of Berek’s talent as a designer and ability to overcome many formidable obstacles to make the Leica a success.
Puts takes us through the design process used at Leitz by Berek and his successors for the subsequent development of interchangeable lenses for the Leica. New glasses and technology such as lens coating, the advances made in mechanical precision and the insight into optical design gained over many years’ experience helped make each new design perform better, work in lower available light, etc. over the course of the past ninety years. The maximum aperture milestones of f/2.5, f/2, f/1.4, f/1.2, f/1 and f/0.95 were all achieved over these years. In Berek’s day, lens designs were done with the use of the slide rule and logarithmic tables. The thousands of calculations were performed by human “calculators”, usually women, after the chief designer came up with his initial design. The design was then verified or changed depending upon the result of these calculations. This method lasted well into the Thirties with the advent of electrical and mechanical desk calculators. This was the first generation of lens designs at Leitz, with the Elmar and Hektor designs by Berek and the Summicron I and Summilux I by Zimmermann and Kleinberg. The second generation came with the introduction of the first digital computer at Leitz with the Zuse 5 in 1952. At this time, the new version of the Elmar 2.8/50, second generation Summicron (Rigid) and Summilux II were designed. Mandler and Marx were some of the wellknown names associated with these designs. In 1958, the Zusewas succeeded by the more powerful Elliott 402 computer, which was used in the design of the Noctilux 1.2/50 designed in 1966 by Helmut Marx and Paul Sindel. In 1968, the IBM 1130 computer with its POSD optical design program came into use at Leitz, and Dr. Marx improved upon the IBM program with his COMO design program. This was used by Mandler to design the Summicron III 50 and the Noctulux 1/50 mm lenses. The third design generation under Lothar Kölsch and Peter Karbe are characterized by the Tri-Elmar-M, 50 Summilux ASPH and the Apo-Summicron 2/50 ASPH FLE. Coupled with improvements in manufacturing at Leica through such innovations as CNC machining, molded aspherics and much tighter manufacturing tolerances and quality control has allowed these cutting edge optical designs become a reality. The fourth generation of lens design is just dawning at Leica, with what Puts calls the “mechatronic” (mechanical and electronic hybrids) age. These designs are those for the S-lenses and the T, Q and SL designs recently introduced by Leica.
Overall, I would recommend this book to the serious Leica photographer or anyone interested in the history of lens design at a leading optical house such as Leitz/Leica. There are diagrams showing the internal details and ray paths of the lenses being discussed, as well as MTF Graphs, Seidel Listings and Spot Diagrams. These are all welcome and help to understand the comparative performance of these lenses. I cannot recall any other author making all of these analytical illustrations available in one place, and Erwin is to be congratulated on this. I cannot argue with the inclusion of Erwin’s very thorough explanation of optical theory and design. After all, if one is to truly understand the subject, one must understand the science and theory behind it. But, as I stated in the beginning of this review, it is slow going and for many readers it will prove to be very difficult reading as well. Having a background in the subject would certainly benefit the reader. This book is not a casual read by any means, but if you take the time to understand the subject through Erwin’s tutorials, you will be rewarded. The minimal captioning and lack of any figure numbers for the illustrations to refer to from the text is not helpful to the reader. Erwin has included a twenty-eight page section of images to illustrate Leica lens quality with the cryptic introductory paragraph stating that they were made with the current 50mm lenses made by Leica. Unfortunately, no further information is given for each image, so we are left to guess which lens made which image. A little more information here would have made a lot of sense, and it is puzzling why this data was omitted. There are several minor typos in the text, but given that English is Erwin’s third language, I think he does quite well with this difficult subject. I would say that the insights into the design process employed by Berek and his successors at Leica for their landmark lenses are well worth the price of admission. The Annex section with brief descriptions of the highlights of each 50mm lens design in chronological order is highly enlightening and useful for quick reference.