What did Ptolemy argue about mirrors and reflected images?

In his work Optica, Ptolemy investigated the nature of visual perception and the behavior of light. Regarding mirrors and reflected images, he distinguished his approach from earlier Greek thinkers by relying on empirical analysis rather than purely philosophical reasoning.1

While predecessors like Hero of Alexandria asserted that an object and its mirror image must make equal angles to a mirror based on theoretical grounds, Ptolemy established this principle experimentally. He measured the angles of incidence and reflection for both planar and curved mirrors using a disk graduated in degrees to confirm the relationship. His work in this field, known as catoptrics, also encompassed broader studies of geometric optics and the nature of vision.12