Visual Rays, and the Pinhole Image of an Aperture
A small light's shadows match the gaps in vision; a ray prints the shape of its aperture
Two figures compare how light and vision fill space. The first states that the places occupied by shadows cast by a small luminous body match in size those regions from which the visual rays are excluded. The second holds that a light ray passing through a small aperture and striking a nearby surface leaves an imprint resembling the aperture it passed through rather than the luminous source it came from, which is the principle of the pinhole image. The lower diagram shows a cross-shaped aperture whose figure reappears past the hole.
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Shadows match the gaps left by visual rays
The places occupied by the shadows a small luminous body casts are equal in size to the regions from which the visual rays are excluded.
A ray prints the shape of its aperture, not its source
A light ray passing through a small aperture and broken upon a nearby surface leaves an imprint more like the aperture it passed through than like the luminous body it came from. The lower figure illustrates this with a cross-shaped aperture.