How a Face Is Lit in a West-Facing Street
Skylight rebounding from the pavement softens the shadows of a profile head
This page of Leonardo's Treatise on Painting explains how a face is illuminated when seen in a narrow street facing west at midday. High walls keep direct sun off the shadowed side, while the skylight that passes between the roofs strikes the pavement and rebounds by reflected motion into the shaded parts of the face, softening every edge so the shadow fades imperceptibly toward the chin. A small profile head drawn at the lower centre carries light-lines lettered a, b, c, d, e together with the lines f e and h that trace how far the light reaches down the face.
On this page
Skylight rebounding into the shadowed side of the face
Because the high walls cut off the reflected sun, the light that passes between the roofs of the houses and terminates on the street pavement rebounds by reflected motion into the shadowed places of the faces and brightens them somewhat. To this is added the grace of shadows with pleasing loss of definition, wholly stripped of every sharp edge.
Light fading gradually from the face to the chin
The band of skylight stamped by the edges of the roofs illuminates almost as far as the beginning of the shadows that lie beneath the projections of the face. From there it changes gradually in brightness until it terminates upon the chin with a darkness imperceptible in every direction.
Diagram of a profile head lit by the rays a b c d e
A small profile head is drawn at the lower centre of the text. A horizontal line at the level of the brow carries the letters a, b, c, d, e, while the lines f e and h below descend toward the face, illustrating how the light a e reaches down as far as beneath the nose.