A Brief History
The medium of photography is evolving toward ever more immediate and ethereal images that often barely exist as digital data. The ease of reproducibility has increased and the scope of dissemination has become instantly global. It was not long ago, however, when photography was mainly a chemical process-an image formed on paper or, more recently, a plastic support. When photography was invented in the 1820s, the image-making process was even more physical. A unique image was etched onto a metal plate through an acid resistant layer. Joseph Nicéphore Niépce (French: 1765-1833) is credited with the first permanent photographic images using sensitized bitumen of Judea on a pewter plateimages that could ultimately be etched and reproduced as intaglio plates. He saw the potential of this process for quick, accurate reproduction of existing engravings (Figure 1-1). Niépce called these first successful photomechanical reproductions heliogravures. These prints, however, did not reproduce any of the smooth continuous tones we now associate with a photograph.