I've been trying to get this to work for years. Just now, with the help of two of our PhD students everything suddenly fell into place. Thanks to Anja for the use of her iPhone. And special thanks to Nikolaj and Justine, who, when I think about it, represent the most important "subjects" of all. I hope the point (i.e., the critique of Foucault's reading of the painting) is obvious. And I hope that the sense in which this is a "self-portrait" is obvious too. Foucault claimed that "the subject is elided". Well, I'm absolutely elated about how well this finally worked!
I want to thank everyone who has ever stopped by my office while I was puzzling with this and stood in various positions to help me work out the angles. A very special debt of gratitude to Lena, who recently pointed out that I had half of the setup the wrong way round. (It's hard to work with mirrors.)
For those who want this effect spelled out in my somewhat belaboured prose of five years ago, see my "Reflexivity in Perspective" in the Journal of Economic Methodology.