Early Developments - The camera itself is based on optical principles known at least since the age of Aristotle; indeed, a filmless version was in use in the mid-1500s as a sketching device for artists. Called the camera obscura (Lat.,=dark chamber), it consisted of a small, lightproof box with a pinhole or lens on one side and a translucent screen on the opposite side.
This screen registered, in a manner suitable for tracing, the inverted image transmitted through the lens. The human eye was the prototype for this device, which functioned as a primitive extension of seeing. Most experiments in photographic technology were directed toward perfecting the medium as a surrogate, more sophisticated eye.
The Invention of Photography - The necessary first breakthrough in photography was in a different, not eye-centered area—that of making permanent photographic images. Employing data from the researches of Johann Heinrich Schulze—who, in 1727, discovered that silver nitrate darkened upon exposure to light
Thomas Wedgwood and Sir Humphry Davy , early in the 19th cent., created what we now call photograms. These were made by placing assorted objects on paper soaked in silver nitrate and exposing them to sunlight. Those areas of the paper covered by the objects remained white; the rest blackened after exposure to the light. Davy and Wedgwood found no way of arresting the chemical action at this stage, however, and their images lasted only a short time before darkening entirely.