Leonardo da Vinci investigated the camera obscura, an image-projection method using a darkened room with a small opening.
In a camera obscura, light from an outside scene passes through a small aperture and forms an image on an interior surface. The projected image appears upside down because light travels in straight lines and rays from the top and bottom of the scene cross at the opening. Leonardo described and studied this effect in his notebooks.
The device was not a camera in the modern photographic sense. It had no photographic film or electronic sensor, so its image disappeared when the light was removed. Artists and scientists used camera obscura arrangements to examine perspective, optics, and the behavior of light.
Leonardo’s writings helped connect the phenomenon with practical observation and drawing, but he did not invent the underlying optical effect. Descriptions of image projection through a pinhole existed before him. His importance lies in his detailed investigation and explanation within Renaissance studies of vision.