The background of a portrait quietly records the world the subject was living inside.

Whoever took the picture was looking at a face, but the camera kept everything else too. The wallpaper, the car at the kerb, the price on a shop sign, the state of the street. Years later that unintended material often tells you more than the pose does. Nobody arranged it, which is why it can be trusted.

Next time you meet an old family photograph, spend a while outside the faces. Ask what the room was like to live in and what it says about the year. Your own pictures are recording the same way, without being asked to.