I found focusing this lens difficult for some reason. Perhaps it was my own fault, I do not know. I sold it to someone who wanted to use it on a digital camera and bought a used Ultron f1.7 LTM. I have been very happy with this lens, though it is larger and not so pretty as the Nokton.
Edit: There is also a new version of the Ultron in M mount. Reportedly it is the equal of the LTM optically and better ergonomically.