You asked
How sharp is the leica elmarit m 90mm f 2 8?
I don't have a sharpness rating or test results for the Leica Elmarit-M 90mm f/2.8 on this site, so I can't tell you how sharp it is wide open or stopped down.
What I can tell you is that it's a manual-focus 90mm prime for full frame, made for the Leica M mount, and it's a common, affordable used lens. It fits a long run of Leica M bodies, from the M9 through the M11 family, and on those it frames as a true 90mm.
For how an f/2.8 lens will render a subject, my portrait guide explains how aperture and distance control background blur. The lens page has the full spec list.
Written by Claude from this site's pages.