Leica 50mm APO Summicron-M ASPH f/2.0

By: Thorsten Overgaard

I may not be a broadly known fact, but Peter Karbe find 50mm lenses fascinating. Not just his own 50mm Summilux-M ASPH f/1.4 and the new (May 10, 2012) Leica 50mm APO-Summicron-M ASPH f/2.0. He finds the whole history of Leica 50mm lenses fascinating.

Peter Karbe & the Leica APO-Summicron-M 50 mm f/2 ASPH. from Leica Camera on Vimeo.

Hopefully one day I will have the possibility to share with you what his fascination with the 50mm lenses are. For one it is my standard lens and was also the focal length the 35mm (24 x 36mm image frame) was developed for. In short, if one wants to make an image perfect, the 50mm lens is the one to focus at.

I tried the lens briefly during the release party in berlin on May 10, but that was in the evening and I didn't do any photos I feel would enlighten any of us about this new lens. Also, though the Leica M Monochrom that was released the same evening has been out with beta-testers for months, none of them have had the Leica 50mm APO-Summicron-M ASPH f/2.0 lens for test.

Delivery should start in August 2012, and as soon as I get mine I shall expand on what it is and what it can do.

Samples with the Leica 50mm APO Summicron-M ASPH f/2.0

Till then, enjoy Erwin Puts' few precise words on the precision and technical accomplishments the new 50mm implies. "I cannot repeat it often enough, but high-quality imagery with a lens of small dimensions is very difficult to achieve. The ASM needed to have a front lens diameter of 39 mm (the normal filter size for Leica Summicron standard lenses). The new ASM has eight elements that have to be fitted in a small-sized mount and there is indeed hardly room for air in this mount. This is a second problem: when lens elements are packed as closely as in the ASM the potential for aberration correction is restricted. It is a triumph of optical and mechanical design" - Erwin Puts

Also have a look at these JPGs by Edmond Terakopian made in the new studio at Leica Store Mayfair in London a few days after the release.

What does Summicron mean?

The word "Summicron" refers to the maximum lens aperture of this lens - here f 2.0 .There are many guesses how this name came about, a popular one being that the "summi" came from "summit" (summit means the highest point of a hill or mountain; the highest attainable level of achievement) while the "cron" came from "chroma" (ie. for colour).
Not so: The name (Summi)cron was used because the lens used Crown glass for the first time, which Leitz bought from Chance Brothers in England. The first batch of lenses were named Summikron (Crown = Krone in Deutsch). The Summi(cron) is a development from the original Summar (the 50mm f2.0 lens annoy 1933)

Peter Karbe with one of the many notebooks, "Optische Konstruktionsbücher" of Prof. Max Berek from 1930. Photo: Thorsten Overgaard.

What does APO mean?

APO stands for "apochromatically corrected" lenses. In most lenses, optical design concentrates the focus of blue light and green light into a single plane, but red light falls slightly into another plane of focus. Red subjects, therefore, would be ever so slightly out of focus compared to blue and green subjects in the same frame. In APO lenses, the design and expense has been put in to making red light focus on the same plane as blue and green. Under a microscope you would see that all light subject is now in focus, creating a sharper image overall. Many manufacturers offer APO designs, but in most of these only the very center of the lens is APO corrected. Leica prides itself on making most of the frame APO corrected.

What does ASPH mean?

ASPH stands for "aspheric design". Most lenses have a spherical design - that is, the radius of curvature is constant. These are easy to manufacture by grinding while "spinning" the glass. This design however restricts the number of optical corrections that can be made to the design to render the most realistic image possible. ASPH lenses, however, involve usually 1 element that does *not* have a constant radius of curvature. These elements can be made by 1) expensive manual grinding, 2) molded plastic, 3) Leica's patented "press" process, where the element is pressed into an aspherical ("non-spherical") shape. This design allows the manufacturer to introduce corrections into compact lens designs that weren't possible before. Practically, the lens performs "better" (up to interpretation) due to increased correction of the image, in a package not significantly bigger than the spherical version.

Pedro Ferreira on the Leica Apo-Summicron-M 50 mm f/2 ASPH. from Leica Camera on Vimeo.