Landscape Appearances and the Transparency of Trees
Why sunlit leaves turn transparent, and how trees screen one another's see-through gaps
This page of the Trattato opens Part Six's chapters on the appearance of landscapes and the transparency of trees. Leonardo notes that leaves lit by the morning sun in the eastern half of the sky glow with a transparent green, while those in the western, humid air look dull and ashen. He then explains how the tiny gaps of illuminated air seen through a tree's foliage blend with its dark mass into a single confused tone. Finally he observes that a tree with others behind it (labelled a, b, c) shows fewer see-through openings than one seen against open sky.
On this page
Morning sun makes eastern foliage a transparent green
When the sun stands in the east, every leaf it lights within the eastern half of the sky becomes transparent and shows a most beautiful green. In the western, humid and murky air the same greens look dull, the color of dark ash, because they are not transparent. The wetter the air, the more luminous the sunlit eastern foliage appears.
See-through gaps of air blend with a tree's dark mass
Seen at a distance, the interpenetration of air and foliage cannot be resolved by the eye, so the parts merge into a confused mixture dominated by whichever is the greater quantity. The little particles of lit air glimpsed through the tree are much smaller than the plant and are lost from notice first. Necessarily a blend of air and of the tree's shadowy dark reaches the eye together.
Trees behind block the see-through openings of trees in front (a, b, c)
A part of a tree shows least see-through gap when a greater mass of other trees stands behind it, between it and the air. In tree a no opening is filled, nor in b, because nothing stands behind them. But in c the case changes, as the following folio continues.