True Color, Reflected Hues, and the Effect of Backgrounds
The eye's pupil adjusts to light; folds and fields reveal or alter a color's true appearance.
A dense text page from the Treatise on Painting. It opens by explaining that the eye's pupil narrows under the excessive light of the air and widens in darker places, gaining power as it grows, citing the second book of Leonardo's Perspective. Two short chapters follow: one arguing that a thing shows its true color only when lit by light of that same color, as in the reflecting illuminated folds of drapery and in gold leaf; and one on how a uniform color seems to vary according to the field it borders, black and white each appearing more noble against its opposite than in its middle.
On this page
The pupil narrows in strong light and widens in darkness
The passage explains that the eye, overcome by the excessive light of the air, greatly narrows its pupil and thereby loses much of its power. In darker places the pupil widens and grows in power as much as it gains in size. Leonardo refers this demonstration to the second book of his Perspective.
A color shows its true hue only under light of its own color
Chapter [203] states that nothing shows its own color unless the light illuminating it is wholly of that color. This is evident in the colors of cloths, whose illuminated folds reflect light onto the opposite folds and make them display their true color. Gold leaf does the same, one part lighting another.
Colors appear altered by the field they border
Chapter [204] holds that no boundary of a uniform color appears equal unless it ends against a field of similar color. This is clear when black borders white and white borders black. Each color seems more noble at the borders with its contrary than it seemed in its own middle.