Portrait of the Theologian Giulio Gagliardi

In 1617 the man who painted this was 26 and still almost unknown outside Cento, the small town north of Bologna where he grew up. The commission was a local one: the likeness of Giulio Gagliardi, a theologian, set down not on canvas but on a little disc of copper only a few centimetres across. Copper gives a hard, enamel-smooth surface that holds fine detail, and a portrait this small was made to be held and turned in the hand, kept close rather than hung on a wall. You can feel the care of a young painter building a name one commission at a time, reading every line of an older churchman's face. It now sits in the Uffizi in Florence, a whole likeness you could hide in a closed palm.