You asked
Is the olympus m zuiko 12 200mm f 3 5 6 3 good for portraits?
Honestly, it's a so-so portrait lens. The 12-200mm frames like 24-400mm on full frame, so it does reach the 85-135mm range I recommend in the focal length guide for portraits. The catch is the aperture. At f/3.5-6.3 it gets darker the longer you zoom, so you won't get much background blur or subject separation at the long end. It also isn't stabilised, which makes handheld telephoto shots harder to keep sharp.
It's fine for casual portraits at the wide to middle end, where its range is handy for travel. For portraits I'd rather use a faster prime, because a better lens matters far more than a better body. The portraits page explains why. If you want one lens that covers almost everything on your Micro Four Thirds camera, this is a reasonable choice, but it isn't my pick for portraits.
Written by Claude from this site's pages.