The photo of a car-park pillar is the most honest picture anyone takes. Nobody is in it, nothing about it is beautiful, and it is taken by someone who knows exactly how much they are about to forget: a letter to whoever walks back out of the shop three hours later, and it nearly always arrives. Then it stays in the camera roll for years, a grey “Level 3 Blue” between a birthday and a sunset, the only picture in there that did its whole job.