When I went outside to see what was happening, I noticed the low yellowish rising sun was laying down a thin reflection on the porch railing.
I experimented with a small aperture, to get more of the railing in focus, but that killed the effect I wanted (as I thought it would). What's interesting here is that the differences between the left part (from the corner) and the right part aren't because of focus issues -- it's that the left side has some rust on it, and the right side doesn't. I was quite taken by that difference.