Transparency of Backlit Trees Seen One Behind Another
The far edge of the first tree glows against the shadow of the second; the nearer part is darker
Leonardo studies trees seen from below and against the light, one closely behind another. The farthest part of the first tree becomes largely transparent and bright and stands out against the dark of the second tree; taking S as the light, r the eye, c d n the first tree and a b c the second, the eye r sees the part c f transparent and bright against the dark ground b c, which is the shadow of tree a b c. A second, analogous figure (t, n, f p q) shows that with the eye at f the part o p appears dark against the bright ground n q, and that among the transparent shadowed parts of trees the nearest to the viewer is the darkest. Two red-chalk tree sketches with ray lines and letter labels accompany the text.
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Backlit first tree glows transparent against the dark second
Of trees seen from below and against the light, one closely behind another, the farthest part of the first is largely transparent and bright and stands out against the dark part of the second. With S the light, r the eye, c d n the first tree and a b c the second, the eye r sees c f transparent and bright against the dark ground b c, which is the shadow of tree a b c.
Trees viewed from below, one behind another
The observation concerns real trees ranged one closely behind another and seen from below, whose successive foliage masses each glow transparent at their farthest edge under the same backlighting condition.
Eye at f: o p dark against the bright ground n q
In the analogous figure t, n, f p q, if the eye is placed at f it will see o p dark against the bright ground n q. Of the transparent shadowed parts of trees, the one nearest to you is the darker.