The Italian architect Filippo Brunelleschi, designer of the dome of Florence cathedral, is also known for developing the rules of linear perspective. In a famous experiment, viewers looked alternately from a vantage point at his perspective painting of the Florence Baptistery, and then the real building, to appreciate the realism made possible by the technique. This lecture explores the maths of perspective, including modern examples like televised sports where sponsors paint their logos so they look right on camera.