You asked
Leica elmarit m 90mm f 2 8 vs voigtl nder apo lanthar 90mm f 4 close focus?
The Leica Elmarit-M 90mm f/2.8 is the one I'd buy for most people. It's a common, affordable used 90mm, and f/2.8 gives you more light and more background separation than the f/4.
The Voigtländer APO-Lanthar 90mm f/4 Close Focus is the choice if you want to get closer to your subject, since its name points to close focusing as its main trick. It's a slower lens, so it needs more light and gives softer backgrounds.
Both are manual focus, full frame, and fit the same Leica M bodies. For the reasoning behind 90mm framing, see the portrait lens guide.
Written by Claude from this site's pages.