ancient times: Camera Obscuras used to form images on walls in darkened rooms; image formation
via a pinhole
1727: Professor J. Schulze mixes chalk, nitric acid, and silver in a flask; notices
darkening on side of flask exposed to sunlight. Accidental creation of the
first photo-sensitive compound.
1800: Thomas Wedgwood makes "sun pictures" by placing opaque objects on leather
treated with silver nitrate; resulting images deteriorated rapidly, however, if
displayed under light stronger than from candles.
1816: Nicéphore Niépce combines the camera obscura with photosensitive
paper
1826: Niépce creates a permanent image
1834: Henry Fox Talbot creates permanent (negative) images using paper soaked in
silver chloride and fixed with a salt solution. Talbot created positive images
by contact printing onto another sheet of paper.
1837: Louis Daguerre creates images on silver-plated copper, coated with silver iodide
and "developed" with warmed mercury; Daguerre is awarded a state pension by the
French government in exchange for publication of methods and the rights by other
French citizens to use the Daguerreotype process.
http://photo.net/history/timeline