How the size of a light governs a body's shadow
Rules on illumination by lights larger or smaller than the shadowed body, with a table
In mirror script Leonardo sets out rules for how the size of a light source governs the shadow on a body: a body lit by a smaller light appears more shadowed, and such a light illuminates less of the body as it nears, while a light larger than the body reveals more of it as it approaches. The reasoning is worked through in the cases of the light being smaller than, or greater than, the shadowed body, at varying distances. Below the text a short table of paired quantities is set out, and geometric figures — triangles and quadrilaterals — are drawn at the lower right. The archive classifies the sheet under geometry (quadrilaterals, triangles and cylinders) and a quadrature.
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A body is more shadowed under a smaller light
Leonardo states that a body appears more shadowed when lit by a smaller luminous source, and that such a source illuminates an ever smaller part of the body the nearer it approaches, and a greater quantity as it recedes. The rules are framed as reciprocal cases of distance and size.
Light larger vs. smaller than the shadowed body
When the light is smaller than the shadowed body it illuminates less of it the closer it lies, and more when remote; when the light is larger than the body, one sees more of the body the nearer the light and less the farther it is.
Triangles and quadrilaterals
At the lower right the sheet bears drawn geometric figures — triangles and quadrilateral shapes — together with a short column of paired numbers and abbreviations. The archive links the sheet to studies of quadrilaterals, triangles and cylinders.
Table of paired quantities
Beneath the text a short table pairs a repeated symbol with columns of small numbers (for example 'p° Q 1 1', 'p° Q 3 21', 'p Q 5 1 2'), tabulating the proportional cases discussed in the shadow rules.