Shadows of Cloth, Foliage and Meadows; a Painting Precept
Why leaves shade less than cloth, how distance dims derivative shadows, and grasses' faint shade
A text page of the Treatise on Painting with an inset fan-shaped ray diagram, comparing shadows of different materials. Leonardo argues a green cloth casts a darker shadow than a leafy tree of the same green, because cloth is not transparent like a leaf and lacks the illuminated air held among the parts of foliage. A headed section proves the darkness of derivative shadows varies with distance: the sun a generates the shadow n p h i, lit around its solar rays by air e b r s and f c r s, being darkest in the space n p o. Further sections note that meadow greenery casts almost no shadow, and a painting precept opens: in universal light, shadows occupy little space.
On this page
Why a green cloth casts a darker shadow than a leafy tree
Of two greens of the same quality, the shadow of a green cloth is darker than that of a leafy tree. This is because the cloth is not transparent as a leaf is, and does not hold illuminated air among its parts as the foliage of plants does, air which serves to soften and confuse the shadowed part.
Darkness of derivative shadows varies with distance
The darkness of derivative shadows varies infinitely, stronger or weaker according to the distance at which their impact falls. Let the sun be a, generating the shadow n p h i, into which the light of the air around the solar rays enters (e b r s above, f c r s below), brightening it; the shadow is darkest in the space n p o, which sees neither sun nor air except at its extremes b c. An inset ray diagram shows this.
Meadow greenery casts almost no shadow
The greenery of meadows has minimal, almost imperceptible shadow, especially where the grasses are small and thin-leaved. The shadows cannot form because the great hemisphere of sky encircles the little stalks; unless there is a tuft of broad leaves, the shadows of the grasses are of little evidence.
Precept of painting: in universal light shadows occupy little space
A headed precept for painters opens at the page foot: under universal (diffuse, open-sky) lighting, the shadows occupy little space. The passage breaks off to continue on the following leaf.