The five motions of shadows and conditions of projection
How light and shadowing body may each move, and when a cast shadow matches its source
An all-text page of the Treatise on Painting classifying the motions of shadows into five natures, according to whether the light, the shadowing body, or both move, and at what relative speed. Leonardo then sets out six conditions under which the projection (percussion) of a derivative shadow can match the primitive shadow: the body must have no angles and be neither perforated nor jagged; the light must match the body in figure and in size; the shadowing ray must be of equal length on every side; the projection must fall between equal angles; and it must strike a flat, unified wall. A closing heading opens the next topic, on where the derivative shadow is greater.
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The five motions of shadows
Leonardo enumerates five natures of shadow motion: the shadow moving with its body while the light stays still; the shadow and light moving while the body stays still; both body and light moving but the light more slowly; the body moving faster than the light; and both moving at equal speed. He promises to treat each distinctly in its place.
Six conditions for a faithful shadow projection
For the projection (percussion) of a derivative shadow to resemble the primitive, six conditions must hold: the body has no angles and is neither perforated nor jagged; the light's figure matches the body's; the light's size equals the body's; the shadowing ray is of equal length on every side; the projection falls between equal angles; and it strikes a flat, unified wall.