The Science of Shadows: Derived Shadow and Foreshortening

Foreshortening shrinks a shadow but not its darkness

The quantity of shadow and light, though reduced small by foreshortening, does not lose brightness or darkness. Its width and length may appear narrower or shorter, yet neither diminish nor increase in their intensity.

Every point of a light casts infinite pyramids

A figure labelled 'luminous body' carries the rule that every point of the luminous body becomes the cause of infinite pyramids of light.

Light reflected from a wall to the opposite place

Light fallen on a mural wall reflects to the opposite place, which is the more luminous on one side than the other according as it is seen from more equal angles of the rebounding light.

Equal shadows between two close facing bodies

When two bodies of equal quality and flat surface face one another, one causing and the other bounding the shadow, if they are close the derived and primitive shadows are of equal darkness; on a flat convergence the derived may be the darker.

How foreshortened light illuminates the opposite body

Though foreshortening makes shadow and light narrower and shorter, their brightness is unchanged; but the office of a foreshortened shadow or light is to illuminate or darken the facing body by exactly the quantity and quality that will appear to it.

Girato il foglio sul lato sinistro. Figura di corpi ombrosi e luminosi colle lettere:

Figura, a sinistra della precedente, di lumi e ombre:

A destra, figura di ombre e lumi:

Sul margine sinistro:

Al centro, figura di ombre e lumi colle lettere e i numeri:

Angolo inferiore sinistro:

Figura di raggi luminosi:

A destra, figura con proiezione di ombre, e le lettere:

Rimesso il foglio in posizione, angolo superiore destro:

Angolo inferiore destro:

Colonna centrale. Figure di ombre e lumi:

Figura di ombre e lumi:

In basso:

Girato il foglio sul lato destro, verso il centro:

The sheet turned onto its left side. Figure of shadowy and luminous bodies with the letters:

Figure, to the left of the preceding, of lights and shadows:

On the right, figure of shadows and lights:

On the left margin:

In the centre, figure of shadows and lights with the letters and numbers:

Lower left corner:

Figure of luminous rays:

On the right, figure with a projection of shadows, and the letters:

The sheet set back in position, upper right corner:

Lower right corner:

Central column. Figures of shadows and lights:

Figure of shadows and lights:

Below:

The sheet turned onto its right side, toward the centre: