Why distant mountains turn blue
A note on the colour of far landscapes and lit rock
Under the heading 'Of landscapes,' Leonardo observes that the dark shadows of mountains seen at a great distance take on a purer and more beautiful blue than their sunlit parts. He adds that when the mountain rock is reddish its lit surfaces read as a purplish-grey, and that the more strongly a surface is lit the more it returns to its own true colour. The note is a precept of aerial perspective; faint offset marks from the facing page show through beneath the writing.
On this page
Blue shadows, while lit rock keeps its colour
At long range the shadowed parts of mountains take on a cleaner, more beautiful blue than their luminous parts; where the rock is reddish, its lit areas appear purplish-grey. The stronger the illumination, the more a surface shows its own proper colour. It is a statement of aerial perspective for the painter.