made by a progressively changing image medium; usually one based on chemical processes
) or on electronic tubes
). This was the dominant form of photography for much of its history, but is now being supplemented by digital photography
As the term analog indicates, light is recorded as a linear chemical process or electric signal. This can be a reaction in a light-activated chemical compound, such as silver nitrate or silver iodide. In electronics this can also be a photoresistor based on cadmium sulfide, germanium or silicon. In this case the amount of electric current through the device is dependent on the amount of light that shines on it.
- Glenn D. Considine, Van Nostrand's Scientific Encyclopedia, Two-Volume Set, 9th Edition (Hoboken, NJ: Wiley, 2002)
- Peter M.B. Walker, Chambers Technical Dictionary (Edinburgh: Chambers 1999)