An analog camera
In general usage, an analog camera is simply one that is not a digital camera. But In a stricter sense an analog camera is one that uses film rather than some type of electronic sensor, such as a charge-coupled device (CCD) or a complementary metal oxide semiconductor chip (CMOS). A similar challenge arose a few decades ago when we needed to distinguish clocks with hands from clocks that showed the time in a series of numerals.
What Does Analog Mean?
Analog refers to devices in which measurable output quantities, such as voltage or pressure, represent input data. A microphone for voice recording is a good example of an analog device. As you speak, fluctuations in air pressure strike the diaphragm of the microphone, causing corresponding fluctuations in voltage in an electrical circuit. The voltage is an "analog," or representation, of the sound waves that make up your voice.
What Does Digital Mean?
"Digital" describes the process by which a signal, such as the light reflected from a scene being photographed, is broken into the binary format so it represents the scene as a series of ones and zeros. That data is then transferred to a storage device and reassembled into a representation of the original scene. The genius of digital is that it can correct any errors that occur during the data transfer, resulting in greater clarity.
Noise
Because of the way analog circuits work to produce continuous, fluctuating signals, they are more susceptible to "noise," or distortion. With analog, a small change in the signal can represent a significant change in the output, and information can be lost in the process. Digital signals, because they deal with only one of two values at any given point in the signal chain, are much more resistant to noise.
Lenses for Analog and Digital Cameras
Digital sensors--except those used on the more expensive professional cameras--are not the same size as the 35 mm frame in film cameras. The lens conversion factor of 1.5 to 1.6 x means that a lens designed for use on a film camera will have a longer equivalent focal length when used on a digital camera. A lens manufactured as a digital lens may not work on a film camera or a full-sensor digital camera.
Agreeing on a Name
It all comes down to agreeing on a term to distinguish cameras that are not digital from cameras that are digital. Many people prefer to continue using the term "film camera" to differentiate analog cameras from digital cameras. Others, such as the Analog Photography Users Group, describe themselves as a group of individuals who are devoted to using the traditional, or non-digital, photographic processes.
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