You asked
Best camera for the tamron sp 45mm f 1 8 di vc usd?
If you want the lens's full frame view, I'd pick the Canon EOS 6D Mark II or the Nikon D750. Either one gives the 45mm its intended field of view, and it fits in a Canon EF or Nikon F setup.
On an APS-C body, the lens frames more tightly, like a 68mm or 72mm lens on full frame. That suits portraits and tighter subjects. If you already own an APS-C camera, the Nikon D7500 and the Canon EOS 90D are solid partners.
Check the Tamron SP 45mm f/1.8 Di VC USD page for the full list of compatible bodies and how each one crops it.
Written by Claude from this site's pages.