Photography is the result of combining several technical discoveries. Long before the first photographs were made, Ibn al-Haytham (Alhazen) (965–1040) invented the camera obscura and pinhole camera, Albertus Magnus (1139-1238) discovered silver nitrate, and Georges Fabricius (1516-1571) discovered silver chloride. Daniel Barbaro described a diaphragm in 1568. Wilhelm Homberg described how light darkened some chemicals (photochemical effect) in 1694. The fiction book Giphantie (by the French Tiphaigne de la Roche, 1729-1774) described what can be interpreted as photography.
For years images have been projected onto surfaces. According to the Hockney-Falco thesis as argued by artist David Hockney, some artists used the camera obscura and camera lucida to trace scenes as early as the 16th century. However, this theory is heavily disputed by today's contemporary realist artists who are able to create high levels of realism without optical aids. These early cameras did not record an image, but only projected images from an opening in the wall of a darkened room onto a surface, turning the room into a large pinhole camera. The phrase camera obscura literally means dark chamber. While this early prototype of today's modern camera may have had modest usage in its time, it was an important step in the evolution of the invention.
All forms of photography have evolved from monochrome photography. Color film is black and white film with three layers of emulsion. Each layer has a colored coupler that makes the resulting black metallic silver deposits in the negative respond to colors in the visible spectrum; red, green and blue. Digital photography employs a silicon sensor that records focused light falling onto it in much the same way that light rays reaching the film expose that portion of the film. So all photography has evolved from the original techniques created to record light rays onto silver halides.
Monochrome images are not direct renditions of their subjects. They could rather be considered deliberate departures from reality. With monochrome photography, not only is the photographer trying to render a three-dimensional world onto a two-dimensional piece of photographic paper, but he or she is also attempting to convert a world that exists in color into one that is represented only in shades of gray. With the use of contrast control filters and film developing techniques, monochrome photography allows the photographer greater license to interpret the subject by controlling local contrast values in the image.
Although color photography was explored throughout the 19th century, initial experiments in color resulted in projected temporary images, rather than permanent color images. Moreover until the 1870s the emulsions available were not sensitive to red or green light.
The first color photo, an additive projected image of a tartan ribbon, was taken in 1861 by the Scottish physicist James Clerk Maxwell. Several patentable methods for producing images (by either additive or subtractive methods, see below) were devised from 1862 on by two French inventors (working independently), Louis Ducos du Hauron and Charles Cros. Practical methods to sensitize silver halide film to green and then orange light were discovered in 1873 and 1884 by Hermann W. Vogel (full sensitivity to red light was not achieved until the early years of the 20th century).
The first fully practical color plate, Autochrome, did not reach the market until 1907. It was based on a screen-plate method, the screen (of filters) being made using dyed dots of potato starch. The screen lets filtered red, green or blue light through each grain to a photographic emulsion in contact with it. The plate is then developed to a negative, and reversed to a positive, which when viewed through the screen restores colors approximating the original.
Other systems of color photography included that used by Sergei Mikhailovich Prokudin-Gorskii, which involved three separate monochrome exposures ('separation negatives') of a still scene through red, green, and blue filters. These required a special machine to display, but the results are impressive even by modern standards. His collection of glass plates was purchased from his heirs by the Library of Congress in 1948, and is now available in digital format.
The charge-coupled device (CCD) was invented in 1969 by Willard Boyle and George E. Smith at AT&T Bell Labs. The lab was working on the Picture-phone and on the development of semiconductor bubble memory. Merging these two initiatives, Boyle and Smith conceived of the design of what they termed 'Charge "Bubble" Devices'. The essence of the design was the ability to transfer charge along the surface of a semiconductor.