Shadow as the Privation of Light
The less light a body receives, the more shadow remains upon it
Text page continuing the Treatise's rules on the placement of lights and shadows. A light looks brighter the closer it lies to the dark, and dimmer the closer it lies to the more luminous parts of a body; a shadow shows the reverse. A central chapter defines shadow as the diminution or privation of light, so that the less a body is illuminated the more shadow remains, and the more it is illuminated the less. The text names the parts of a lettered figure — a the luminous body, b c the shadowed body with b lit and c deprived of light, and a second case with luminous body E, shadowed body f, lit part e f and shaded part e g — and a further chapter opens on the lights and shadows that tint the surfaces of landscapes.
On this page
A light looks brighter the nearer it lies to the dark
That light will show itself brighter which draws nearer to the dark, and will seem less bright the nearer it lies to the more luminous parts of the body. A shadow, conversely, looks darker near the brightest part of a body and less dark near its darker parts.
Shadow defined as the privation of light
Shadow is the diminution or privation of light. The shadow upon a shadowed body will be of greater quantity the less light illuminates it, and the greater the sum of light that falls upon the body, the smaller the quantity of shadow that remains upon it.
The lettered figure of luminous and shadowed bodies
In the described figure a is the luminous body and b c the shadowed body; b is the part that is lit, and c the remaining part deprived of light, where the shadowed exceeds the lit. In the second case E is the luminous body, greater than the shadowed body f opposite it; e f is the lit part and e g the shaded part.