that great explorer of visual reality

?The way light falls on a body reveals its form. The way the body?s surface reflects the light reveals its texture. . . .

The distinction was, of course, known to that great explorer of visual reality, Leonardo da Vinci. He calls it the difference between light and lustre, lume e lustro. Nothing fascinated Leonardo more than the subtle gradations from light to shade which can be observed when an opaque sphere is placed near a window.?

?E.H. Gombrich, from Light, Form and Texture in Fifteenth-century Painting, published in the Journal of the Royal Society of Arts, CXII, October 1964.