1. The Camera Obscura

At its most basic, the Camera Obscura is a simple box (which may be room-sized) with a small hole in one side. Just like the human eye, light passes through the hole and projects an inverted (upside-down) image against the back wall. As the pinhole is made smaller, the image gets sharper, but the light-sensitivity decreases. By using mirrors, it is also possible to project a “right-side-up” image. Various forms of these boxes were used all the way back to 1000 AD. In later versions, the projection can be made on paper on which an artist can copy the image.

Camera = Latin for “room”
Obscura = Latin for “dark”

Earlier versions were simply a box with a hole, but later they discovered that they could control the light better by installing a lens over the hole to create a sharper image where they wanted it to be. This invention was merely a projector that projected an image that could be traced by hand. It was a developmental tool in art to study perspective and proportion.

2. Photosensitivity and Silver Nitrates

Albertus Magnus, in the 13th century, documented the ability of nitric acid to separate gold and silver by dissolving the silver. Magnus noted that the resulting solution of silver nitrate could blacken skin.

In 1614, Angelo Sala demonstrated that “powdered silver nitrate is blackened by the sun”, as was paper that was wrapped around it. This discovery of the sun’s effect on powdered silver nitrate was not supported and was subsequently disregarded by then-respected scientists who said that his discovery “had no practical application.”