Steven in New Jersey says:
I've been standing at the edge since before the new A7III came out and I'm now I'm almost ready to buy one. I'm checking Amazon every day for inventory but I have one question. It's a big money jump. Assuming the A7III body, I am considering the Sony 16-35mm Vario-Tessar or the Sigma 12-24mm f/4.5-5.6 DG II HSM Lens. The Sigma is about $300 or $400 less but I'd love to hear from those who use these setups.
The research I've done suggests that the top 3 choices for wide-angle zoom lenses for the A7III are:
Yes, the Sigma lens you refer to will work but you've got to spend another $250 for an adapter so that choice would nearly cost as much as #3 above. Another reason for getting a native Sony lens is, the A7III has software in it to do all the lens corrections in camera. You wouldn't have to do those corrections in Lightroom or Photoshop.
I'm sure there are others out there that have first-hand experience with making this lens choice.