Laser reveals trick to Michelangelo’s magic

reports in Thursday’s issue. It was "a typical Michelangelo trick," designed to give a different appearance to David according to the angle of view, says Levoy.

In the classic three-quarter view, David is seen looking slightly to the left, gazing at his adversary. But viewed from the other side, in left profile, David stares heroically into the middle distance. The left profile is rarely seen by visitors today to Florence’s Galleria dell’Accademia, because it is obscured by a wall. But there was no such obstruction at the sculpture’s original site, outside the Palazzo Vecchio.

Levoy believes that Michelangelo cleverly hid the squint by using David’s upraised left hand, which holds a slingshot draped over his shoulder, to prevent a full-frontal view of his face. The squint was revealed by shining a thin, harmless sheet of laser light onto the statue and recording the shape of the beam edge as it swept across the surface. The scans were then transcribed by computer into a 3-D image so detailed that chisel marks less than a millimetre across and minute cracks in the marble were revealed.

Levoy’s next target is a 1,800-year-old archaeological puzzle, the Forma Urbis Romae — a giant map of ancient Rome that now lies in more than 1,000 pieces, waiting to be reconstructed by hand. Three-dimensional scans of the broken edges may enable scientists to piece the jigsaw back together, Levoy hopes.