La crucifixión con la Virgen, san Juan Bautista, san Juan Evangelista y san Francisco

By 1460 Florence had spent a generation working out how to build real depth on a flat panel with ruled lines and vanishing points, and few painters chased that geometry harder than Paolo Uccello. Here he brings it to a Crucifixion. The cross stands dead center, two mourners balanced on each side, dark sky above and dark earth below, so the panel folds into an almost perfect symmetry. It is worked in tempera, pigment bound with egg and laid in thin strokes, the method Florentine workshops were just starting to trade for oil paint. At the foot kneels Saint Francis, who by tradition bore the same five wounds as Christ, and Uccello lets him press close to the wood while the Virgin and the two Saints John hold the corners of his careful grid.