Two distinct scientific processes, optical and chemical, had to combine to make photography possible. Optical was the first of these techniques to be invented. A camera obscura, dark room, had a small hole at one end of the room that light passed through and formed an image on the opposite wall. The hole was soon replaced with a lens, which made the image brighter and sharper. The camera obscura shrunk in size and became portable and could be used as an aid in rendering perspective correctly. Thus, it became a part of the artist's tools.

    The second technique was chemical. Photographic chemistry refers to the invention of an emulsion, a light sensitive material. In the sixteen hundreds, Robert Boyle reported that silver chloride turned dark under exposure, but believed it was due to exposure to air rather than light. In the early seventeenth century, Angelo Sala noticed that powdered nitrate of silver could be blackened by the sun. In 1727, Hohann Heinrich Schulze discovered that certain liquids change color when exposed to light. Carl Wilhelm Scheele discovered that ammonia acts as a fixer to make a photographic image permanent, but failed to realize the importance of his discovery.

    By the beginning of the nineteenth century, Thomas Wedgewood had successfully captured photographic images, but his silhouettes could not survive without a method of making the image permanent. Wedgewood was the first to conceive of the idea of photography with the use of a portable camera obscura.