|Micronesia foliage from U.C. Berkeley|
This is true at the level of individual leaves or fronds, such as these leaves in a rain forest. Note the gradations within each leaf, with the lightest values at the tips of the leaves and the darkest values at their bases where they attach.
With transmitted light, this darkening at the proximal end is a consequence of both the greater material thickness at the base, and the lesser amount of light arriving at the top surface due to occlusion from nearby forms.
In this painting from Dinotopia: First Flight, I was conscious of varying the color and value of the leaves and making them lighter at the tips, especially when we see them illuminated by the yellow-green transmitted light.
The principle is also true on a larger scale, not just at the level of a leaf, but also at the level of entire trees when you look at them in indirect light.
|James Perry Wilson, Summery Showers|
In this 12x16 inch oil study by James Perry Wilson (1889-1976), note how each tree silhouette gradates from darkest at the base of each tree or bush to lightest at the outer and upper edges.
Blog posts about James Perry Wilson