I originally purchased this lens when my wife joined the church and the minister let me take photos if they were not distracting. So I shoot 800 ASA color film with this lens at f2.8 at 1/60. These were beautiful That lens has served very well on all my Leicas. It is a bit ruff to use on the IIIF. It is so big it covers loads of the viewfinder.
This has been one of the fastest lenses I have ever had. I had a Nikor 50mm f1.4 for a Nikon F I had. It survived a fire, a dunk from a canoe and a fall out of a moving jeap. I doubt the Voigtlander is that touch, but it produces great images.