Now, you made me curious about your subject, what is it if you don't me asking.
The subject is passageways. I have to wait for the OK to show something, sorry.
If you can work with mf lenses and 18mm is sufficient then I highly recommend the new Zeiss 18mm, for 14mm Tamron makes one which imo is superior to the Sigma and Canon lenses, its only equal is the Nikon 14mm, some say that they're both made by Tamron.
15 mm is the sweet spot. So 14 with a little crop is perfect here. Never thought that I would use lenses like that. Usually I prefer 35/50/85.