During the previous decades perhaps as many as ten individuals had tried to make a photograph. At least four were successful: Joseph Nicephore Niepce, Louis J. M. Daguerre, Hippolyte Bayard in France and William Henry Talbot in England.

Each of them employed two scientific techniques that had been known for some time but had never before been successfully combined.

The first of these techniques was optical.
Since the16th century artists and scientists had made use of the fact that light passing through a small hole in one wall of a dark room, or camera obscura, projects an inverted image on the opposite wall.
The hole was soon replaced with a lens, which made the image brighter and sharper. By the 18th century the room had been replaced by a portable box, which artists used as a sketching aid.

The second technique was chemical.
In 1727, Johann Heinrich Schulze had discovered that certain chemicals, especially silver halides, turn dark when exposed to light. The first attempt to use such chemicals to record the image of the camera obscura was made - unsuccessfully - by Thomas Wedgwood about 1800.

Daguerre's invention, bought by the French government and made public in 1839, produced a one-of-a-kind picture on metal, the Daguerrotype.
In contrast, Talbot's invention (1840), the Calotype, produced a negative picture on paper; the lights of the image were recorded as darks, the darks as lights.
A positive was made on another sheet of chemically sensitized paper, exposed to light through the negative. Because an infinite number of positives could be made from a single negative, Talbot's invention and refinements of it soon predominated.

The photograph's capacity to repeat itself exactly and infinitely through the negative-to-positive process was one side of its radical character. The other was its privileged status as a picture created by nature alone.

The ever-increasing ease with which photography precisely recorded visual information and distributed it worldwide made it the most powerful tool of communication since the invention of the printing press.

Early theories of photography stressed its mechanical nature. To some, this nature excluded the personal intervention that was the stamp of art; to others, photography's potential signaled the demise of painting.
Neither view prevailed. Painters continued to paint and photographers proliferated; at best, everyone agreed that the new invention was useful.

Arcane and mysterious by today's standards, early processes were nevertheless easy enough to learn, and the medium spread rapidly throughout Europe and America. Photography appealed to a few professional scientists and artists, but most early photographers were undistinguished - artisans, handymen of all sorts, and, like several of the inventors, versatile amateurs. These individuals shared neither a common tradition nor a uniform intention. Only in the 20th century did an approximate consensus - or even a coherent argument - emerge about the past achievements and future goals of photography.

Because early photographers were largely unfettered by academic convention or demand for a uniform commercial product, the first two decades of photography were rich in pictorial experiment.
Among the inventors, Talbot and Bayard were especially sensitive to the beauty of the new medium. Their loving records of often humble subjects announced photography's aptitude for the intimate, personal view.

Some of the best early photographers had been trained as artists; none were important artists, however, and many had a talent with the camera that they lacked with the brush.
In the 1840s, D.O. Hill and Robert Adamson made photographic portraits as studies for a large group portrait that Hill finished painting 20 years later. The painting is an awkward failure; the photographs, however, possess a grandeur that recalls - without copying - portraits by old masters. It was as if the training and talent of the painter could only be released in a practical struggle with the camera, the light of the day, and the mood of the sitter.

The intuition of Hill and Adamson was shared by an impressive group of French photographers of the 1850s, among them Gustave Le Gray, Charles Marville, Charles Negre, E.D. Baldus, and Henri Le Secq (1818-82).
Several of these men were, like Hill, painters, and they brought the conviction of art to their work and to their Societe Francaise de Photographie. They frequently photographed important places and historic monuments for the government, but this work was not separate from their private experiments. Their pictures preserve the adventurous spirit of early photography before it became both an art and a business.

Even after the medium began to be dominated by professionals in the 1860s, many of the most inventive 19th-century photographers were amateurs.
Perhaps the best of them was Julia Margaret Cameron, who made intense portraits of her friends, eminent Victorians. Cameron also composed photographic tableaux in which real people were transformed into characters from Alfred, Lord Tennyson's Idylls of the King. In their own day, these pictures were admired as idiosyncratic productions; today they are appreciated as precocious examples of photography's responsiveness to fantasy and fiction.

The amateurs may be contrasted with photographers such as Oscar Gustav Rejlander and Henry Peach Robinson, who attempted to challenge painting on its own ground. In England in the 1850s, they turned out labored but technically accomplished versions of successful genre paintings, pieced together from as many as a dozen different negatives. These hackneyed failures doubtless encouraged the enemies of photographic art.
They may also have benefited the commercial photographers, who recognized that artistic aspiration had no place in their work and went on to make practical - and original - pictures.

After 1851, when Frederick Scott Archer's process substituted glass for Talbot's paper negative, the mass production of albumen prints of extremely fine detail became possible.
Until the 1880s this was the medium of the great commercial firms, which fed an enormous popular demand for portraits and for views of famous monuments or strange places. The majority of 19th-century photographs fall into these two categories.

By the mid-1850s, when Andre Adolphe Eugene Disderi popularized the small, cheap portrait, anyone could afford a picture of himself or herself.
The effect of this development on the growing self-awareness of the working class and on the self-perceptions of the bourgeoisie cannot be easily overestimated. Thanks to photography, ordinary people possessed an emblem of identity formerly reserved for the rich.

View photography radically expanded access to the art and great monuments of Europe, the Mediterranean, and, eventually, the Far East and the Americas.
Traditional and exotic culture, once the privilege of the wealthy traveler, could be known accurately, cheaply, and at home through photographs.

At first, topographical photography was the work of dilettantes, such as Maxime Du Camp, who published their travel photographs in albums of original prints that were made by incipient commercial firms like that of Louis Desiree Blanquart-Evrard.

By the 1860s large commercial firms such as Francis Frith's in England and the Alinari Brothers in Italy were in operation; their approach to photographic documentation was systematic and encyclopedic.
At the turn of the century, for instance, the Alinari catalog offered 60,000 views of Italian cities and reproductions of paintings. The new disciplines of art history and archaeology depended enormously on these pictures, and the average person came to take them for granted. Like its contemporary, the railroad, photography made the world seem smaller.

The variety and extent of the visual encyclopedia of the world that was compiled during the first 30 to 40 years of photography is all the more extraordinary because the medium was still extremely cumbersome. Cameras were large and heavy and required tripods. Each glass plate had to be exposed while still wet with a freshly coated emulsion.
Consequently, photographers in the field were obliged to pack along makeshift darkrooms. It is commonly said, with some truth, that the precise beauty of early photographs is due to the resolution required to make them.

Like artists, but with greater flexibility and on a much larger scale, photographers recorded contemporary events.
In the 19th century, photography still had the power of undisputed truth.
In the last third of the century that power was enlisted as a tool of social reform. The journalist Jacob August Riis began in the 1880s to use photography to expose the appalling conditions in New York City's slums. Two decades later Lewis Hine, a sociologist, supported a campaign for child-labor laws with his sympathetic portraits of young factory workers.

Photography was also applied to scientific inquiry. Cameras were attached to microscopes and telescopes and produced strange pictures that were derived from nature - details of the world that once were invisible.
Scientists and social reformers both profited from the continuous technical improvements in photography, which reached a watershed with the introduction of dry plates in the 1880s. The new plates did away with field darkrooms, and their faster emulsions made it possible to stop action.

Cameras also became smaller and more portable.
In 1888, George Eastman's Kodak, which used flexible roll film, made photography available to anyone who could press a button. Like the first photographic portraits, Kodak snapshots changed people's lives by changing their view of themselves.

A scattered but energetic group of photographers in the late 19th century sought to cut themselves off from the worldly role of their medium in order to establish photography as a branch of fine art. They endorsed the old claim that to be an art photography must look like established art, and they revived old techniques, in particular the gum-bichromate print, that allowed manual intervention. The hazy forms of such prints had the merit of being instantly distinguishable from the detailed precision of commercial photographs.
In 1889, Peter Henry Emerson had set the stage for this development by making a sharp distinction between artistic photography and the practical work of professionals.

By the early 20th century a lively, although exclusive, international network of societies for artistic photography existed, including the Linked Ring Brotherhood in London (founded 1892) and the Photo-Secession in New York (founded 1902). The new status that the movement won for photography may have been more a function of its polemics than of its pictures, but unquestionably it produced a number of exceptional photographers.
In rough terms, the aesthetic movement rejected truth in favor of beauty; it spurned photography's descriptive ability in favor of elegant photographs based on paintings. It was possible to discover private meanings - "equivalents" of feelings - in any subject, however well-known or inconsequential it might appear to the ordinary eye.
This has been the assumption of photographers ever since.

A photograph is not identical with the subject it depicts but rather is a way of looking at that subject - an interpretation. Photography is a subjective medium - a vehicle for artists.

The expressive possibilities of experiments with the photographic process were matched by the versatility of the small, high-speed cameras that were introduced in Europe in the 1920s. The new cameras freed photographers from every encumbrance. It became possible for the first time to follow - and capture - the most rapid or ephemeral action, to record the world as it happened.

Among the first to use the new cameras were journalists like Erich Salomon and Felix H. Man, who recorded any event, the trivial along with the important. Their work was published in the picture magazines, such as Life and its European counterparts, that began to flourish in the 1930s and that established the new, often lucrative, profession of photojournalism.
The editors of these magazines needed pictures that could be quickly understood.
These photographs displayed a new, apparently casual form, based on the perception of the moment rather than on the rules of the studio.

In the 19th century the time and effort required to make a photograph had argued against taking a chance. After 1930, because photography was quick and easy, it became reasonable to try a shot even if the result was not certain. Photographers, with more mistakes to learn from, acquired a flexible sense of form, one capable of describing the complex situations that (thanks to the small cameras) had become their subject.

Walker Evans, perhaps the best photographer of the period, stood somewhat apart from this trend. His pictures seemed artless, straightforward views of the odd junk and generally undistinguished buildings that clutter the country. But the lean order imposed on these humble subjects revealed a grace and a beauty that no one had ever seen before. Evans staked out a claim for intelligence in photography; he showed that a photographer's understanding of his subject may be so convincing that it seems to be the only one possible.

After World War II the creative initiative in photography, as in painting, shifted substantially to the United States.
In the late 1950s the picture magazines began to fail. The erosion of this public forum for photography coincided with a rapidly growing awareness of the artistic potential of the medium that was no longer limited to a few visionaries. The new population of artist-photographers has found support in the academic community and in the burgeoning market for fine photographic prints. The market in turn has contributed to an expanding interest in photography's rich, if incoherent, history, and photographers themselves have increasingly plundered the past.

Into the 1990s, photography, like the other arts, has been marked by a considerable diversity of style and concern. As a result it is impossible to summarize the best work by referring to a few leading photographers. Some of the most innovative contemporary photography has arisen from a new fascination, at turns affectionate or ironic, with the imagery of popular culture, especially advertising and the movies, but there was and is also a wide use of fashion photography.
Many critics have labeled this work "postmodernist," implying that it signals the demise of earlier 20th-century traditions and aspirations. "Postmodernism," however, has joined rather than replaced a wide range of thriving modernist styles, from experimental formalism to documentary realism: the old continues to find new incarnations, while the new adds new meanings to the language of contemporary photography.

The many highly talented photographers in the field have produced a level of work that is often well above the commercial and is studied and ranked as a form of social documentation, if not as art.

The roots of modern fashion photography can be traced to the18th-century sketches known as fashion plates and the 19th century drawings used to illustrate catalogs. Like the modern photograph, these drawings were used to disseminate ideas about style and sophistication.

Among the first fashion photographs were those taken by Baron Adolph de Meyer, Edward Steichen, and Cecil Beaton during the 1920s. In many of these photographs style was opulently linked with social status and famous clothing designers. Such magazines as Vogue and Harper's Bazaar devoted their pages almost exclusively to photo illustrations.

Photographers like Richard Avedon and Irving Penn carried on the tradition of studio photography that these magazines had fostered - although, by the 1950s and 60s, the posed, highly stylized, somewhat tense fashion portrait was shot in front of an empty backdrop that removed the distinction between floor and wall, emphasizing the difference between fashion and reality.

More contemporary photographers - Bruce Weber, Herb Ritt, and many others - shoot on location, looking for spontaneity and a more potent connection with the real.