You asked
Olympus m zuiko 45mm f 1 8 vs sigma 56mm f 1 4 dc dn contemporary?
On Micro Four Thirds, the Olympus M.Zuiko 45mm f/1.8 is the easier pick. It's tiny, cheap, and autofocuses, with a 90mm-equivalent view and depth of field similar to f/3.6. For portraits on a budget, it's a lovely lens.
The Sigma 56mm f/1.4 DC DN Contemporary is made for APS-C, but it also mounts on Micro Four Thirds. There it frames like 112mm and gives about the depth of field of f/2.8, so you get more reach and more background blur. Choose the Sigma if you want that tighter look and don't mind the APS-C design. If you want the simplest everyday portrait lens for Micro Four Thirds, go with the Olympus.
For more on portrait focal lengths, see the portraits guide.
Written by Claude from this site's pages.