I've had this lens for 10 years now. It is my fastest lens in Leica mount, I do have the Canon 50/0.95 in Canon Breech-Lock mount. This lens is a classic double-Gauss 7 elements in 6 groups, multi-coated optics. This lens has a longer optical path than the Canon Super-Speed 50/1.2 and 50/0.95, meaning it is big. For digital cameras- long optical path is better.

Light fall-off at the corners is about 2 F-Stops, compares with the Leica 50mm F1.0 Noctilux.
At the current price-
https://shop.cameraquest.com/voigtlander-leica-mount-lenses/voigtlander-50mm-f/1.1-lens/
of $700, this lens is a super-speed bargain. I've owned the Canon 50/0.95 for 18 years, bought a pair for ~$200 each. I've never felt the need to get mine converted to M-Mount after owning this lens.
This lens was introduced in 2009, and is optimized for the Bessa series and Zeiss Ikon series Film cameras made by Cosina. This lens had a measurable back-focus on my M9, which I corrected by placing 1 layer of 3M copper tape on the RF cam of the lens. If I wanted to optimize it for a deep color contrast filter for the M Monochrom, I would add one more layer of tape.
This adjustment was required for both my 50/1.1 and 35/1.2 v1 Nokton.


Wide-Open on the M Monochrom.

Wide-Open on the M9:

I keep a UV/IR cut filter on my lens when using with the M9. Most super-speed lenses suffer from Chromatic Aberration which is worse outside of the visible spectrum. On the M9, this will show up as purple fringing.

Light fall-off at the corners is about 2 F-Stops, compares with the Leica 50mm F1.0 Noctilux.
At the current price-
https://shop.cameraquest.com/voigtlander-leica-mount-lenses/voigtlander-50mm-f/1.1-lens/
of $700, this lens is a super-speed bargain. I've owned the Canon 50/0.95 for 18 years, bought a pair for ~$200 each. I've never felt the need to get mine converted to M-Mount after owning this lens.
This lens was introduced in 2009, and is optimized for the Bessa series and Zeiss Ikon series Film cameras made by Cosina. This lens had a measurable back-focus on my M9, which I corrected by placing 1 layer of 3M copper tape on the RF cam of the lens. If I wanted to optimize it for a deep color contrast filter for the M Monochrom, I would add one more layer of tape.
This adjustment was required for both my 50/1.1 and 35/1.2 v1 Nokton.


Wide-Open on the M Monochrom.

Wide-Open on the M9:

I keep a UV/IR cut filter on my lens when using with the M9. Most super-speed lenses suffer from Chromatic Aberration which is worse outside of the visible spectrum. On the M9, this will show up as purple fringing.