The ZI I had for almost three years was very happily mated to a Voigtlander Heliar Black 50mm, f2 M mount version. It never let me down. But good luck finding one.
The optics are the same in the nickel version, right? CameraQuest still lists those available---they aren't especially cheap, but in the context of the price of a ZI body, what's a couple of hundred extra bucks for a really good lens?
San Diego, CA, USA
The lady of the house has to be a pretty swell sort of person to put up with the annoyance of a photographer.
-The Little Technical Library, _Developing, Printing, And Enlarging_