The Eye and Light: Pupil, Pinhole and Doubled Images
Why a bright body seen through a tiny hole looks smaller, and why the pupil narrows against excess light
This optical page examines how the eye receives images of light. Leonardo argues that two or three images of a single light reaching one sense fuse into one that seems larger than it should, and that a luminous body viewed through a minimal pinhole in paper held to the eye looks smaller in proportion to the hole. A further note explains that the eye, dazzled by excess light, contracts its pupil and loses part of its visual power. Two eye-and-aperture diagrams accompany the reasoning.
On this page
Several images of one light fuse into one
Leonardo states that the two or three images of a single light, arriving at one sense, appear as one but larger than a single body warrants — just as each of the two eyes receives its own image that the sense unites into one.
A luminous body seen through a pinhole appears smaller
Seen through a minimal perforation (n, a, o, p, c, m) made in paper held as close to the eye as possible, a bright body — though wholly visible — looks smaller the smaller the hole. He attributes this to a lesser power having less potency than a greater.
The pupil contracts against excess light
Overwhelmed by too much light, the eye narrows its pupil and diminishes part of its visual power. A closing 'Conception' adds that the bodily operator must be in contact with what it acts upon.