The “idea” of photography dates back to the 10th century “camera obscura” and “pinhole camera” described by the Arab scientist, Abu Ali al-Hasan (or Alhzaen), author of The Book of Optics. The camera obscura was a large dark box with a hole in one end which could produce an inverted image opposite it. It is the forerunner of today’s cameras. All it lacked was a lens and means of fixing the image chemically.
It wasn’t until 1816 that a Frenchman, Joseph Nicéphore Niépce, began experimenting with chemically fixing mages. His first success was in 1822, and in 1826 he created the first photograph. That photograph required an 8-hour exposure time. He called the process “heliography.” After his death in 1833 his partner, Louis Jacques Mandé Daguerre continued working on the photograph process. In 1837 Daguerre succeeded in reducing the exposure time to 30 minutes. He dubbed his photographs “Daguerreotypes,” and in 1839 he introduced them in Paris and New York City.
The Daguerreotype photographic process was in widespread use from 1839 through the 1920s, and 21st century Daguerreian hobbyists still use it. It was at the height of its popularity from 1839 to 1858.
Daguerreotypes or “dags” are laterally-reversed high-contrast images with very fine, crisp details. They are always case-mounted and sealed with paper tape. The image area is mirrored, so it is necessary to hold it at an angle to see the image clearly.
Identifying antique photographs is just one of the many things you will learn in the "Photography: Clues Picture Hold, Editing, Digitizing and Various Projects" course with The National Institute for Genealogical Studies.