You asked
What are the alternatives to the tamron 12 20mm f 2 8?
I don't have other lens models to compare against this one on the site yet, so I won't name alternatives I can't back up. The Tamron 12-20mm f/2.8 is a 570-gram constant f/2.8 zoom that reaches 12mm on full frame, and it fits Sony E and Nikon Z cameras.
For other options, start with the Lenses page. Its third-party section covers Sigma, Tamron, Samyang and Viltrox, which often cost less than a camera maker's own lenses. Check that your camera's maker allows third-party lenses on your mount, because not every brand does.
If you're looking for a wide zoom to compare against this one, the Focal length converter will show you how a lens's framing and depth of field change on your sensor size.
Written by Claude from this site's pages.