You asked
Is the tamron 17 50mm f 4 di iii vxd good for portraits?
The Tamron 17-50mm f/4 can work for portraits, but it isn't a portrait lens. At 50mm on full frame you get a natural view, which suits environmental portraits that show where someone is. f/4 gives less background blur than a faster lens, though, and at the 17mm end, close faces get exaggerated.
For portraits, I'd look at the Tamron 35-100mm f/2.8 Di III VXD. It's a full-frame f/2.8 zoom aimed at portraits and events, and it gives you the longer, more flattering perspective. The Tamron 90mm f/2.8 Di III Macro VXD is another option, since it doubles as a short portrait telephoto. For the full reasoning, see Portraits.
Written by Claude from this site's pages.