Rays Through an Aperture and the Kinds of Shadow
Light through a slit; smaller angles carry less light; a red-chalk glossary of shadow
The sheet studies how light passes through a narrow opening and defines the vocabulary of shadow. The large upper diagram sends luminous rays through a vertical slit so that they cross and spread into a circle of gradations at the right (labels e g i l m K h f, a b c d), while a small figure below repeats the scheme. Leonardo reasons that the part of the air struck by the more acute luminous angle keeps more of its natural darkness, because a smaller angle has a smaller base and so fewer rays converge to its point. In red chalk he sets out crisp definitions of darkness, shadow, and the primitive, derivative, reflected and simple shadows.
On this page
Distant luminous bodies appear as one
If many luminous bodies are seen from a far country, although they are divided among themselves they will appear united and joined together.
Rays crossing through an aperture
Luminous rays pass through a narrow opening, cross at a point, and spread out into a graduated circle at the right, carrying the letters e g i l m K h f and a b c d along their path.
A smaller luminous angle carries less light
Where the luminous angle is smaller there is less light, for its pyramid has a smaller base and fewer rays reach its point. Angle a has a greater base (e f) than angle b (g h), so a has a quarter more base and a quarter more light; c sees i K, half the light e f, and d sees the quarter l m.
Red-chalk definitions of the kinds of shadow
Darkness is the privation of light; shadow the diminution of light. Primitive shadow clings to a shadowy body; derivative shadow detaches from it and runs through the air; reflected shadow is ringed by an illuminated wall; simple shadow sees no part of the light that causes it and begins on the line leaving the edges of the luminous bodies a b.