Louis-Jacques-Mandé Daguerre invented the daguerreotype process in France. The invention was announced to the public on August 19, 1839 at a meeting of the French Academy of Sciences in Paris. American photographers quickly capitalized on this new invention, which was capable of capturing a "truthful likeness." Daguerreotypists in major cities invited celebrities and political figures to their studios in the hopes of obtaining a likeness for display in their windows and reception areas. They encouraged the public to visit their galleries, which were like museums, in the hope that they would desire to be photographed as well. By 1850, there were over 70 daguerreotype studios in New York City alone.
Popularity of the daguerreotype declined in the late 1850s when the ambrotype, a faster and less expensive photographic process, became available. A few contemporary photographers have revived the process.
The daguerreotype is a direct-positive process, creating a highly detailed image on a sheet of copper plated with a thin coat of silver without the use of a negative. The process required great care. The silver-plated copper plate had first to be cleaned and polished until the surface looked like a mirror. Next, the plate was sensitized in a closed box over iodine until it took on a yellow-rose appearance. The plate, held in a lightproof holder, was then transferred to the camera. After exposure to light, the plate was developed over hot mercury until an image appeared. To fix the image, the plate was immersed in a solution of sodium thiosulfate or salt and then toned with gold chloride.
Exposure times for the earliest daguerreotypes ranged from three to fifteen minutes, making the process nearly impractical for portraiture. Modifications to the sensitization process coupled with the improvement of photographic lenses soon reduced the exposure time to less than a minute.
Although daguerreotypes are unique images, they could be copied by redaguerreotyping the original. Copies were also produced by lithography or engraving. Portraits based upon daguerreotypes appeared in popular periodicals and in books. James Gordon Bennett , the editor of the New York Herald, posed for his daguerreotype at Brady's studio. An engraving , based on this daguerreotype later appeared in the Democratic Review .
The earliest cameras used in the daguerreotype process were made by opticians and instrument makers, or sometimes even by the photographers themselves. The most popular cameras utilized a sliding-box design. The lens was placed in the front box. A second, slightly smaller box, slid into the back of the larger box. The focus was controlled by sliding the rear box forward or backwards. A laterally reversed image would be obtained unless the camera was fitted with a mirror or prism to correct this effect. When the sensitized plate was placed in the camera, the lens cap would be removed to start the exposure.