Euclid's Optics

The work deals almost entirely with the geometry of vision, with little reference to either the physical or psychological aspects of sight.

Whereas Plato and Empedocles thought of the visual ray as "luminous and ethereal emanation",[3] Euclid’s treatment of vision in a mathematical way was part of the larger Hellenistic trend to quantify a whole range of scientific fields.

[4] Renaissance artists such as Brunelleschi, Alberti, and Dürer used Euclid's Optics in their own work on linear perspective.

[5] Similar to Euclid's much more famous work on geometry, Elements, Optics begins with a small number of definitions and postulates, which are then used to prove, by deductive reasoning, a body of geometric propositions about vision.

For example, in proposition 8, Euclid argues that the perceived size of an object is not related to its distance from the eye by a simple proportion.

Euclid postulated that visual rays proceed from the eyes onto objects, and that the different visual properties of the objects were determined by how the visual rays struck them. Here the red square is an actual object, while the yellow plane shows how the object is perceived.
1573 edition in Italian