QuoteI need something around that equivalent for real estate photos. Until I can afford a t/s or 14mm L might just have to keep using my 7D
For ultra-wide angle, look into the Samyang 14mm. It's a killer lens. The distortion is easily fixed in processing.
Here's a thread with great real estate examples shot with this lens:
Just got mine (Rokinon rebadge) and have to agree. This lens is really nice and sharp.