You asked
Is the olympus m zuiko 12 100mm f 4 is pro good for portraits?
It's a good travel lens that's only fine for portraits. The 12-100mm f/4 frames like 24-200mm on full frame, and its long end is the useful part. Shooting at 70-100mm means you stand back, which keeps faces in proportion, as Portraits explains.
The catch is f/4. It won't blur backgrounds much, so if you want a softer, more separated look, a fast prime like the 85mm f/1.8 described on the Portraits page will do more for you.
If you want one lens for people and everything else on a trip, this one works. Shoot at the long end, keep the background well behind your subject, and move closer if you want more blur. For serious portrait work, I'd add a fast prime. The lens fits bodies like the OM System OM-5 Mark II and the OM System OM-1 Mark II, so either would be a sensible base.
Written by Claude from this site's pages.