A Treatise on Painting

by da Vinci Leonardo

Among several colours of the same nature, that which is the nearest to the eye will alter the least; because the air which interposes between the eye and the object seen, envelopes, in some measure, that object. If the air, which interposes, be in great quantity, the object seen will be strongly tinged with the colour of that air; but if the air be thin, then the view of that object, and its colour, will be very little obstructed.

Chap. CCXC.—Of the blueish Appearance of remote Objects in a Landscape.

Whatever be the colour of distant objects, the darkest, whether natural or accidental, will appear the most tinged with azure. By the natural darkness is meant the proper colour of the object; the accidental one is produced by the shadow of some other body.

Chap. CCXCI.—Of the Qualities in the Surface which first lose themselves by Distance.

The first part of any colour which is lost by the distance, is the gloss, being the smallest part of it, as a light within a light. The second that diminishes by being farther removed, is the light, because it is less in quantity than the shadow. The third is the principal shadows, nothing remaining at last but a kind of middling obscurity.

Chap. CCXCII.—From what Cause the Azure of the Air proceeds.

The azure of the sky is produced by the transparent body of the air, illumined by the sun, and interposed between the darkness of the expanse above, and the earth below. The air in itself has no quality of smell, taste, or colour, but is easily impregnated with the quality of other matter surrounding it; and will appear bluer in proportion to the darkness of the space behind it, as may be observed against the shady sides of mountains, which are darker than any other object. In this instance the air appears of the most beautiful azure, while on the other side that receives the light, it shews through that more of the natural colour of the mountain.

Chap. CCXCIII.—Of the Perspective of Colours.

The same colour being placed at various distances and equal elevation, the force and effect of its colouring will be according to the proportion of the distance which there is from each of these colours to the eye. It is proved thus: let C B E D be one and the same colour. The first, E, is placed at two degrees of distance from the eye A; the second, B, shall be four degrees, the third, C, six degrees, and the fourth, D, eight degrees; as appears by the circles which terminate upon and intersect the line A R. Let us suppose that the space A R, S P, is one degree of thin air, and S P E T another degree of thicker air. It will follow, that the first colour, E, will pass to the eye through one degree of thick air, E S, and through another degree, S A, of thinner air. And B will send its colour to the eye in A, through two degrees of thick air, and through two others of the thinner sort. C will send it through three degrees of the thin, and three of the thick sort, while D goes through four degrees of the one, and four of the other. This demonstrates, that the gradation of colours is in proportion to their distance from the eye [72]. But this happens only to those colours which are on a level with the eye; as for those which happen to be at unequal elevations, we cannot observe the same rule, because they are in that case situated in different qualities of air, which alter and diminish these colours in various manners.