Index to Part Five: Pyramidal Shadow and the Opaque Sphere
Chapter list: equal-angle illumination, the pyramidal shadow, and the shadow of an opaque sphere in air and on the ground
An index page from the fifth part of the Trattato della pittura, continuing the list of chapter rubrics (729-738) with their leaf cross-references. The entries treat the physics of illumination and cast shadow: light striking a body at equal versus unequal angles, the pyramidal action of light and shade, cast shadows converging to a single point at the window, and the shadow of an opaque sphere in the air and on the ground. A running head and a foliation number appear on the sheet but are not part of the transcription.
On this page
Equal angles of light and the pyramidal shadow
Rubrics describe how light striking a body at equal angles gives the highest degree of brightness, while less equal angles yield darker illumination, with light and shadow performing their pyramidal office. Another entry traces every cast shadow to a single point formed by the intersection of luminous lines within the opening of the window.
The two pyramids and the opaque sphere's shadow
The list treats how every shadowy body sits between two pyramids, one dark and one luminous, visible only when light enters by a window. Closing entries address the shadow of an opaque sphere set in the air, one resting on the ground, and the shadows of somewhat transparent bodies.