Leonardo Da Vinci’s Notebook in text form. From Project Gutenberg,
./ Random excerpt
THIRD BOOK ON LIGHT AND SHADE.
Definition of derived shadow (158. 159).
158.
Derived shadow cannot exist without primary shadow. This is proved
by the first of this which says: Darkness is the total absence of
light, and shadow is an alleviation of darkness and of light, and it
is more or less dark or light in proportion as the darkness is
modified by the light.
159.
Shadow is diminution of light.
Darkness is absence of light.
Shadow is divided into two kinds, of which the first is called
primary shadow, the second is derived shadow. The primary shadow is
always the basis of the derived shadow.
The edges of the derived shadow are straight lines.