Photography is a powerful means of capturing memories through pictures and of connecting with friends and relatives separated by distance or time.
As the year comes to a close, we often look back over the previous year at triumphs and disappointments, laughter and tears. Many of those memories are captured through the combination of art and science known as photography.
Historically, the concept of the camera obscura, in which an image was projected through a small opening onto an opposite surface, was well established by the 1800s. Indeed, in the late 1400s and early 1500s, Leonardo da Vinci wrote about natural examples of the centuries-old concept in his papers collected in the Codex Atlanticus.Photography, which means “drawing with light” in Greek, was born when the image from the camera obscura was fixed permanently on a surface, such as a sheet of photographic paper. Chemistry provided key components in the evolution of this technology.
The general principle is reasonably straightforward. First, a surface such as paper or a piece of metal is coated with a substance that will react with light. After the surface has been exposed to the image, a process is required to remove the unreacted photo-sensitive material so that the areas of light and dark are preserved. French inventor Joseph Nicéphore Niépce took the first photograph by using a pewter plate coated with bitumen, which hardened upon exposure to light, and allowed unhardened regions to be washed away. Louis Daguerre, first in collaboration with and then carrying on the work alone after Niépce’s death, refined the process of using silver nitrate to capture an image since silver compounds darken upon exposure to light. Daguerrotype photography used a silver coating on a copper plate to capture the picture.
Numerous subsequent developments refined the chemical process of recording and preserving an image. George Eastman played a significant role in making photography both convenient and accessible to a wide and appreciative public. He patented film in roll form in 1884 so that photographers no longer needed to carry around bulky glass photographic plates. In 1901, his Kodak camera, the Brownie, made photography accessible to everyone.
Photography is now mostly carried out using digital cameras, but chemistry historically was the heart of this process that we use to capture moments and memories. For those photographic artists who still develop their own images, the process remains as much about the chemistry as about the art.
An excellent historical retrospective on the history of photography may be found at http://photography.nationalgeographic.com/photography/image-collection/#/history_of_photography/