On Shadow and Light: What Shadow Is
Opening of Part Five of the Treatise; definitions of shadow, darkness, and their cause.
This page opens Part Five of the Treatise on Painting, 'On Shadow and Light.' In a series of short defined paragraphs Leonardo distinguishes shadow, a diminution of light, from darkness, its complete privation, and explains that shadow arises from two dissimilar causes: the corporeal shadowing body and the spiritual light. He then argues that shadow, like all universal things, is most powerful at its origin, so the painter should make shadow darkest next to its cause and let its far edge turn into light.
On this page
What shadow is, and how it differs from darkness
Shadow is defined as the diminution of light applied to the surface of bodies, beginning where the light ends and ending in darkness. Its difference from darkness is that shadow is a lessening of light, whereas darkness is the complete deprivation of light.
The two causes of shadow: body and light
Shadow derives from two unlike things, one corporeal and one spiritual: the corporeal cause is the shadowing body, the spiritual cause is the light. Together, light and body are the cause of shadow.
Shadow is strongest at its origin
Shadow shares the nature of universal things, which are most potent at their beginning and weaken toward their end. Darkness is therefore the first degree of shadow and light the last.
Advice to the painter on grading shadow
Because shadow is most powerful near its cause, the painter should make the shadow darkest next to what produces it. From there it should be graded so that its far end turns into light, seeming to have no end.