Leonardo da Vinci studied the camera obscura, an optical device that projects an outside scene through a small opening onto an interior surface.
In a darkened room or box, light travels from the scene through the aperture and forms an image on the opposite wall. The projected image is usually inverted because rays from the top and bottom of the scene cross at the opening. Leonardo used the phenomenon to investigate vision, light, perspective, and the workings of the eye.
Leonardo did not invent the camera obscura. The effect was known in antiquity and was discussed by scholars including Ibn al-Haytham in the eleventh century. Leonardo’s notebooks contain especially detailed observations and diagrams that connected the device with his scientific studies.
The camera obscura is a precursor to photographic cameras, but it does not record an image permanently by itself. It projects an image; a person must observe or trace it.