Shadow and light on bodies; illumination by air without sun
From the fifth part of the Treatise: firm shadow-edges and the soft dead light of an overcast or twilight sky.
Continuing the fifth part of the Treatise, this leaf opens by noting that a form always divided in half toward its point keeps its remainder brighter than the raised portion, then gives chapters on the shadow and light of shadowed bodies. Bodies seen between light and shadow must be firmly bounded, while parts turned to the light blend together with little difference. A further chapter treats bodies lit by the open air without the sun, as under cloud or just after sunset, when the sky gives a dead light and shadow-edges grow faint, and instructs the painter to trace imaginary lines from illuminator to illuminated body. The page is a clean scribal copy without diagrams.
On this page
Firmly bound the shadow and light of shadowed bodies
All parts of a body that the eye sees between light and shadow must be strongly bounded in shade and light, while the parts turned toward the light blend together with little difference within the light. Shadowed parts, if no reflection falls on them, show as little variety between their darker and lighter portions as the lit parts do.
Bodies lit by the open air without the sun
For bodies seen in the open air without the sun, the most illuminated part is the one seen by the greater part of the illuminating body, so the painter draws imaginary lines from illuminator to illuminated body. Under cloud, or just after sunset when the sky gives a dead light, reflections have little appearance and every body shows the boundaries of its shadows only faintly.
Softer shadow-edges from greater light
A short note adds that the boundaries of shadows are the more imperceptible the greater the quantity of light from which they arise. Reflections, or the shadows enclosed between the incident and the reflected light, occupy the same place.