Aerial Perspective: Thick Air Magnifies Distant Things
A distant mountain outmeasures a near one, and the sun behind bare trees swallows their branches.
Continuing the comparison begun on the previous page, Leonardo concludes that air of quadruple thickness makes the same things appear four times larger than they do through thin air, and that unequal things can be made to look equal by suitably unequal interposed air. He illustrates the 'perspective of colours' with the observation that a finger near the eye can cover a great distant mountain. Two further painting rules follow: a dark thing seen against a brighter field looks smaller, so branches of leafless trees vanish against the solar body, and upright parallel bodies in fog appear thicker at the top than at the foot. The page is unbroken running text with no diagram.
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Air of quadruple thickness makes things look four times larger
The same things seen first through thin air and then through air four times thicker will appear four times larger in the thick air. Unequal things at equal distance can even be made to look equal when the denser air is placed before the smaller one.
A finger near the eye covers a great distant mountain
By the perspective of colours a great mountain, small by measure, can appear larger than a small object close to the eye. As one often sees, a finger held near the eye is enough to hide a whole distant mountain.
The sun behind leafless trees swallows their branches
Among things of equal darkness, size, shape and distance, the one seen against a brighter or whiter field looks smaller. The sun behind bare trees so diminishes every twig set against its body that the branches become invisible, as does a shaft held between the eye and the sun.
Upright bodies in fog appear thicker at the top
Parallel bodies set upright and seen through fog are to show thicker at the top than at the foot. This follows because fog or thick air struck by the solar rays appears the whiter the lower it lies.