Leica The Oldest Leica Mount 5cm F1.5 Sonnar ever used on an M9.

It's so true.

This lens is on loan to me to do some tests. It can only be described as an experiment by Zeiss to test their lenses on a Leica. Nicely made, nicely machined, but would not be suitable for production. The mount has an exposed helical, that would have to be redesigned. But- the focal length of the Sonnar is too long for the Leica standard. The lens works quite well up-close and out to reasonable distances. At infinity, the longer focal length of the Sonnar is an issue. This problem was solved by the production Leica Mount Sonnars introduced almost 7 years after this lens was made. The "trick" is to move the read module in closer to the front of the lens, reducing the focal lenght. I have three LTM Sonnars in original mount, and several that i have converted myself.Except for one of my custom jobs, My lenses act like this one, require stopping down to F2.8 for infinity. I have one 1935 Sonnar that is perfect at F1.5 across the full range. That lens has a repolished front element, which probably reduced the focal length.

At F1.5:

and F4:

A 100% crop at Infinity, F1.5

At F4, the Sonnar focus shift and DOF brings infinity into focus.

100% crop


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