Light and Shade: Derived Light and the Four Kinds of Light
Trattato della pittura, Part Five — definitions of light, shadow, illumination and lustre
A run of short chapters opening the treatise's discussion of light and shade. Leonardo defines derived light as the product of an original light and a shadowy body, then distinguishes four kinds of light that fall on opaque bodies — universal (the light of the air), particular (sun, window or door), reflected, and light passing through translucent things like cloth or paper. Further definitions equate darkness with the privation of light, shadow with a mixture of the two, and set lustre apart from ordinary illumination. The page closes by beginning a demonstration about an object placed between larger dark and light bodies.
On this page
The four kinds of light that fall on opaque bodies
The lights illuminating opaque bodies are of four sorts: universal, like the light of the air within our horizon; particular, like that of the sun, a window, a door or other opening; reflected light; and a fourth that passes through translucent things such as cloth or paper, though not transparent like glass or crystal.
Darkness, light, shadow, illumination and lustre defined
Darkness is the privation of light and light the privation of darkness; shadow is a mixture of the two, deeper or shallower according to the power of the light mixed with it. Illumination is a sharing of light, whereas lustre is the mirroring of that light.
Derived light and the object set between dark and light bodies
Derived light results from two things: an original light and a shadowy body. An object placed between larger dark and light bodies of continuous extent has the most imperceptible boundaries to its shadows and lights, as the demonstration begins to prove with an object o set between the shadowy n m and the luminous r s.