Leonardo da Vinci studied the camera obscura to explain how images form inside the eye.
A camera obscura is a darkened room or box in which light enters through a small opening and projects an inverted image of the outside scene onto an opposite surface. Leonardo compared this optical effect with the eye, whose pupil admits light and whose interior receives an image.
His notes from the late fifteenth and early sixteenth centuries contain detailed observations about image projection, perspective, and the behavior of light. The camera obscura was not Leonardo’s invention; related principles were described by earlier scholars, including Ibn al-Haytham.
Leonardo’s contribution was his careful use of the device as an investigative model. It helped him connect geometry and observation, although his historical understanding of the eye did not match modern knowledge of the retina and neural vision.