>>4130722It's a Sigma 8-16mm. It projects a FF image at 16mm, but you get down to ~12mm eq in APS-C mode. Luckily, real estate photos shouldn't be more than ~4mp anyway.
Bonus: it's rectilinear and fairly sharp.
Making small spaces look bigger, and fitting the details into a single frame is very useful.
Here's what the FF coverage looks like at 8mm.