Analog photography is photography made by a progressively changing image medium; usually one based on chemical processes (photographic film) or on electronic tubes (TV). 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.