You asked
What are the alternatives to the voigtl nder ultron 27mm f 2?
I don't have a list of other lenses to suggest against the Voigtländer Ultron 27mm f/2 here, so I can't name real alternatives without making them up. The page itself covers the lens: a manual-focus pancake for Fujifilm X that frames like a 40mm on full frame, with f/2 giving roughly the depth of field of f/3.
To find your own alternatives, start with the Focal length converter, which shows how crop factor changes both framing and depth of field. Then browse the Lenses guide to compare apertures and what a wide opening does for you.
Written by Claude from this site's pages.