Tuesday, December 1, 2015

Foliage is Lightest at Its Outer Edges

In indirect light, foliage tends to be lightest at its outer and upper edges, and darkest at its base or its core.
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


P said...

On the level of trees I can try an explanation. The vertical planes receive and therefore reflect less light from the sky above than horizontal planes. So the ground and the top of the trees are lighter than the the rest of the tree.

A Colonel of Truth said...

The peerless master of vegetation in transparent watercolor? John Singer Sargent
His works of (Florida) palmettos etc., stunning! And mind-boggling!

gyrusdentus said...

Speaking of foliage. Do you have a big pan of raw sienna in your watercolor set to mix greens with that orangish raw sienna?
I heard of people mixing yellow ochre with cad yellow and raw sienna but i have never gotten its importance.

The work of Wilson is simply amazing. Given that were his studies en plein air is awe-inspiring.