Concave and Backlit Leaves in Light and Shadow
Why a concave leaf seen from below looks half shadowed and half transparent, and how overlapping leaves read dark to light
This red-chalk page of Notebook G treats foliage as an optical problem. One note explains that a concave leaf seen from beneath appears half in shadow and half transparent, with a small diagram lettering the leaf o p, the light m and the eye n. A second note observes that among leaves set between the light and the eye the nearer reads darker and the farther lighter, provided it is not silhouetted against the sky. A naturalistic lobed-leaf cluster is drawn at the lower right, and the text is in mirror script.
On this page
A concave leaf seen from below, half shadowed and half transparent
A leaf with a concave surface, viewed from its underside, sometimes appears half in shadow and half transparent. Letting o p be the leaf, m the light and n the eye, the eye sees o in shadow because the light does not strike it at equal angles, while p is lit on its upper side and that light shows through on the underside.
Dark leaves in front of transparent ones
When leaves lie between the light and the eye, the leaf nearest the eye is the darker and the more distant is the lighter, so long as it is not silhouetted against the sky. This happens with the leaves that lie beyond the centre of the tree, toward the light.
Study of a lobed leaf cluster
A naturalistic red-chalk study of a cluster of lobed, vine-like leaves is drawn at the lower right of the sheet, complementing the optical notes above.