Distant White, and Why Remote Shadows Turn Blue
Aerial perspective: whiteness lost with distance, the azure of far shadows, darker shadows on dense bodies
A text page of the Treatise on Painting continuing the discussion of vision and completing the pupil argument: a wide pupil sees more splendor than a small one, as anyone proves who looks at the stars through a small hole in paper. Three headed sections follow. Leonardo explains that a white thing loses its whiteness the farther off it is, taking on the color of the sun mixed with the color of the intervening air, and that the shadows of remote things grow more azure the darker and farther they are. A final section states that primitive shadows are darkest on the surface of denser bodies and lighter on rarer ones.
On this page
A wide pupil gathers more light: the pinhole star test
A larger pupil takes in a luminous body of greater quantity and more excellent splendor than a smaller pupil, as is shown by one who looks at the stars through a small hole made in paper. The narrowed aperture limits the light admitted, demonstrating how pupil size governs the brightness that reaches the eye.
Distant white loses its whiteness through the color of the air
The white thing removed from the eye loses its whiteness the more it is removed, and all the more the more the sun illuminates it, because it partakes of the color of the sun mixed with the color of the interposed air. If the sun is in the east the air looks turbid and reddish from rising vapors, but if the eye turns eastward it sees only the shadows of the white taking on an azure color.
Remote shadows grow more azure with darkness and distance
The shadows of remote things partake all the more of azure the darker they are in themselves and the farther away, through the interposition of the brightness of the air between the eye and the shadowed bodies set between it and the sun. If the eye turns to face opposite the sun, it will not see such azure.
Primitive shadows are darkest on dense surfaces
Primitive shadows are made darker when generated on the surface of a denser body, and on the contrary lighter on the surfaces of rarer bodies. This is manifest because the images of the objects that tint opposing bodies with their colors impress with greater force where the surface is denser.