Drawing With Light
Photography is the practice of creating images by recording light, either chemically on a light-sensitive material or electronically with an image sensor.
The name says exactly that. It was built from the Greek roots for light and for drawing, together meaning "drawing with light".
The basic method has not changed in two centuries. A lens focuses light reflected or emitted from objects into a real image on a light-sensitive surface inside the camera, during a timed exposure. With an electronic sensor this produces an electrical charge at every pixel, which is processed and stored as a file. With photographic film the same light produces an invisible latent image, which is only revealed later by chemical development.
That middle step is the part digital photography quietly deleted. For most of the medium's history, taking a photograph meant carrying home something you could not yet see.
The Camera Existed Long Before the Photograph
The camera obscura, Latin for dark chamber, is the ancestor of every camera ever built, and it is ancient. It dates back to ancient China, and Greek mathematicians Aristotle and Euclid independently described one in the 5th and 4th centuries BCE.
The person who turned it into physics was the Arab scholar Ibn al-Haytham, who lived from 965 to 1040. He gave the first correct analysis of the camera obscura, including the first geometrical and quantitative descriptions of it, and was the first to use a screen in a dark room so an image could be projected through a hole onto the other side. He also understood the relationship between the focal point and the pinhole, and ran early experiments with afterimages.
Leonardo da Vinci later noted that caves on the edge of a sunlit valley form natural versions: a hole in the cave wall acts as a pinhole camera and projects the scene outside, upside down, onto the rock.
Eight Centuries of Trying to Make It Stay
For all that optical understanding, nobody could keep the image. The camera obscura projected a perfect picture that vanished the moment you looked away, and the entire birth of photography was the effort to trap it.
The chemistry arrived in pieces over centuries. Albertus Magnus discovered silver nitrate in the 13th century. Georg Fabricius discovered silver chloride in the 16th. Daniele Barbaro described a diaphragm in 1566. Wilhelm Homberg described how light darkened certain chemicals in 1694. Around 1717, Johann Heinrich Schulze used a light-sensitive slurry to capture images of cut-out letters, which is why some sources credit him as the inventor of photography outright.
In June 1802, Thomas Wedgwood made the first known attempt to capture a camera obscura image with a light-sensitive substance. He got images. He could not make them permanent, which is the whole problem in one sentence.
Minutes Instead of Hours
The breakthrough was not just capturing an image but capturing it quickly enough to be useful.
Louis Daguerre's process, later named the daguerreotype, had its essential elements in place by 1837: a silver-plated surface made sensitive by iodine vapour, developed with mercury vapour, then fixed with hot saturated salt water. Crucially, the exposure time was measured in minutes rather than hours.
Working separately, Henry Fox Talbot published his own previously secret method in a paper to the Royal Society in 1839. His paper-based photography also needed hours-long exposures at first, but in 1840 he produced the calotype process, which used chemical development of a latent image to cut the exposure dramatically and compete with Daguerre.
One oddity: the inventors did not use the word we use. Nicéphore Niépce called his process heliography, Talbot called his photogenic drawing, and Daguerre used his own name. The word photography appeared in public print in a German newspaper in February 1839, and the astronomer John Herschel is also credited with coining it that year.
