The process that started it
In January 1839, the French scientist Francois Arago described Louis Daguerre’s new method to the French Academy of Sciences, and in August of that year the French government announced it publicly, granting Daguerre and the heirs of his late partner Nicephore Niepce lifetime pensions in exchange. Photography as a public technology is often dated from that announcement. Earlier experiments, including Niepce’s, existed, but the daguerreotype was the first process practical enough for many people to use.
A daguerreotype was made on a sheet of copper coated with a thin layer of silver, polished to a mirror finish. The steps, in outline, were:
- The silver surface was exposed to iodine fumes, forming light-sensitive silver iodide.
- The plate was exposed in the camera. Early exposures were reported in minutes, later shortened to seconds as lenses and chemistry improved.
- The latent image was brought out by holding the plate over heated mercury.
- The image was made stable with a chemical bath. Early on this used salt solution, and the sodium thiosulfate fixer suggested by the scientist John Herschel became standard.
- The plate was often toned with gold chloride, then sealed under glass in a case to protect the delicate surface.
Portraits were taken in studios near large windows, since artificial light was weak; electric lighting did not become practical for portraits until later in the century. The result was a single, unique picture with remarkable fine detail. It could not be duplicated, and it appeared as a positive or negative depending on the viewing angle. Mercury vapor was also a real hazard for working photographers, as is well documented.
A second route: paper negatives
Also in 1839, William Henry Fox Talbot in England announced paper-based methods, and his calotype process of the early 1840s produced a negative from which many prints could be made. The pictures were softer than a daguerreotype, partly because the paper fibers showed in the image, and good paper making mattered, but the idea of a reusable negative proved far more important for the long term. Talbot’s patents, however, restricted its use in England for some years. The words “photography,” “negative” and “positive” are credited to Herschel, who suggested them in 1839.
Glass plates
In 1851, the English sculptor Frederick Scott Archer published the wet collodion process, which coated glass with a sticky solution and gave sharp negatives at a lower cost than daguerreotypes. Because the plate had to be used while still wet, photographers carried portable darkrooms. By the 1870s, gelatin dry plates could be made in factories and stored until needed, which made cameras more convenient and exposures shorter.
Roll film
In 1888, George Eastman’s Kodak camera used a roll of film and offered photography as a service in which the company handled developing. Celluloid film base followed. Eastman’s company and others spread cheap cameras to a mass market, and in the 1920s the 35mm Leica made smaller cameras practical. A separate article covers that period in more detail.
Color, speed and automation
Color photography existed in experimental form in the 1800s, but practical color film arrived with the Autochrome plate from the Lumiere brothers in 1907 and later with Kodachrome in 1935. Through the middle of the twentieth century, cameras gained built-in light meters, single-lens reflex viewing, automatic exposure and, from the late 1970s, autofocus. Electronics increasingly handled tasks once done by hand.
Sensors
The charge-coupled device, developed at Bell Labs in 1969, was the key to electronic photography. A Kodak engineer, Steven Sasson, built a camera around such a sensor in 1975. Consumer digital cameras followed in the 1990s, and by the 2000s they had largely displaced film for ordinary users. The same sensor technology, and its CMOS successors, now sits inside smartphones and professional cameras alike, as one of the many silicon chips in each device.
How the changes fit together
Looking back, each change solved a limit of the previous one:
| Change | Problem it addressed |
|---|---|
| Paper negative (1839-1841) | Unique plates could not be copied |
| Wet collodion (1851) | Images needed to be sharper and cheaper |
| Dry plates (1870s) | Photographers needed to carry less equipment |
| Roll film (1888) | Amateurs needed a simpler process |
| Color film (1900s-1930s) | Black-and-white pictures lacked color |
| Electronic sensors (1970s onward) | Film needed processing and could not be reviewed at once |
What is uncertain
Exposure times for the earliest daguerreotypes vary between accounts, and early dates can differ by a year depending on whether a source cites an announcement, a patent or a first demonstration. The history of the daguerreotype is better documented than much of what came before it, but many details, such as who exactly tried what in the years before 1839, are still debated. Treat dates in popular summaries as approximate.