The False Violet Shadow of Fire and Air
Blue air above, red fire below make a violet shadow; the true shadow, and tinting studio walls
This folio completes the two-light shadow proof: at d n the fire's red no longer reaches, only the blue of the air, so the blue shadow terminates below in the red of the fire and above in a violet tone, being lit at d e by a mixture of the air's blue a b and the fire's red. Leonardo concludes the shadow is 'false', belonging neither to the white body nor to the surrounding redness. Chapter [703] states the true shadow of a body should partake of no colour but the body's own, taken with black (which is not a colour), and advises the painter to tint the studio walls with white mixed with black. Chapter [704] begins by asking which object most tinges the white surfaces of opaque bodies with its likeness. A prominent pen diagram of the fire-and-air arrangement, with candle flames and an arc, occupies the upper text column.
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Why the cast shadow turns violet
At d n the fire's redness no longer reaches, only the blue of the air, so the blue shadow terminates below with the red of the fire and above with a violet colour. At d e it is lit by a mixture of the air's blue a b and the fire's red, giving what is almost a violet, proving the shadow false, belonging neither to the white body nor to the redness around it.
[703] What is the true shadow of a body's colour
The shadow of a body should partake of no colour other than that of the body to which it is applied. Since black is not counted among the colours, from it the shadows of all colours are taken with more or less darkness, never wholly losing the body's colour except within the outlines enclosed by the opaque body.
Advice: tint the studio walls white mixed with black
Leonardo tells the painter who wishes to portray to tint the walls of the studio somewhat with white mixed with black, because white and black are not a colour. Chapter [704] then opens the question of which object most tinges the white surfaces of opaque bodies with its own likeness.
Diagram of the fire, air and cast shadow
A pen diagram set into the upper column shows lines converging from a light source, candle-like flames and a curving arc, laying out the geometry of the body lit by air above and fire below with its interposed object. It is drawn, not transcribed, and keys the lettered points d, e, n, f of the violet-shadow proof.