Friday, June 21, 2013

Brian Sweeney Writes About Using the Old Zeiss Sonnar and Leica Digital M on THEME

I love using classic lenses on my M9, as you will have seen by my "Whole Lotta Leica" series. I also love to learn more about these old lenses and how they are designed and perform.
Brian Sweeney has made a name for himself in adapting Zeiss Sonnar lenses to Leica M mount. Brian recently wrote a post for the blog THEME, describing a lot about lens design history, adapting Sonnars, and the resulting images.
(Click Here) to read Brian's post on THEME.
Here are some new things I learned from Brian's post:
  • Leitz (Leica) has taken the approach of minimizing aberrations in their lens designs, particularly through symmetric "double Gauss" optical arrangements. According to Brian, this is the approach used from the early days, up to and including the modern APO Summicron.
  • The concept of double configurations is that the front lens assembly's aberrations are cancelled out by the light going through a paired optical assembly at the rear.
  • Asymmetric designs allow for wider apertures.
  • Zeiss has usually pursued brighter lenses and higher contrast than Leitz. They achieve this through asymmetric design and minimizing the number of lens interfaces and gaps. For example, the classic 5.0 cm f2 Sonnar has 6 gaps, as compared to the similar era Leica Xenon, which has 10.
  • Zeiss Sonnars in original Leica mount are very rare. As a result, Brian has found ways to remount them from other mounts, like the much more prevalent Contax mount. In the post, he even shares a link to instructions to try it yourself.
In Mr. Sweeney's examples, I can see what he describes about the different rendering of the Sonnar. While very sharp, these older lenses, many uncoated, don't have the contrast of a modern lens. While lower in contrast than modern examples, they are described as being higher contrast than older uncoated Leitz lenses, like the Summar.
I have a couple of uncoated Leica lenses - a Summar and a Summitar. Both are favorites of mine. I don't have a classic Sonnar, but I do have the modern example of the Zeiss C-Sonnar 50mm f1.5. It's an amazing lens - both loved and hated strongly by different photographers. I love mine. In fact, I think it will be my Whole Lotta Leica lens for June.
Here's an example shot from my modern Sonnar on the M9.
Low Light Performance of Acoustic Burgoo, by Reed A. George
Leica M9, Zeiss Sonnar C 50mm f1.5 Lens
iso 1250, f2, 1/125 sec
If I were to pursue a classic Sonnar for my Leica, I would try to buy one from Brian. They come up every once in a while on the forums.