How light passes through leaves: transparency and luster
Three red-chalk sketches of branches and a single leaf, with the eye, the light and the leaves' reverse
In red chalk, Leonardo studies how leaves appear when light passes through or across them, illustrating with three small sketches: a leafy branch (top right), a single leaf S surrounded by radiating light- and sight-lines (middle right), and a second branch (lower right). With the light at m and the eye at n, the leaves a b take on the colour of the air (m c), while b c, seen from the reverse, glow a beautiful transparent green tending to yellow. When m illuminates the leaf S, every eye that sees its reverse finds it a beautiful light green because it is transparent; and often leaves cast no shadow, showing a transparent reverse and a lustrous front.
On this page
Branch a b c seen with the light behind
If the light comes from m and the eye is at n, that eye will see the colour of the leaves a b all partaking of the colour of m c, that is, of the air; and b c, seen from the reverse, appear transparent, of a most beautiful green tending to yellow.
The illuminated leaf S seen from its reverse
If m is the luminous illuminator of the leaf S, all eyes that see the reverse of that leaf will find it a most beautiful light green, because it is transparent.
Leaves without shadow: transparent reverse, lustrous front
Many are the times when the arrangements of leaves are without shadow, having the reverse transparent and the front (the right side) lustrous.