Logarithmic data is a mathematical transformation of data that compresses larger and larger increases in value into modest increases.
Human perception of sound and vision is logarithmic, and so working with logarithmic data is necessary for modern postproduction.
An example of logarithmic data is the decibel scale for measuring sound levels.
A sound level of 20dB is 10 times greater than a sound level of 10dB, but a sound of 30dB is 100 times greater than a sound level of 10dB.
The logarithmic decibel scale is more useful than the linear measurement of sound pressure, since it mimics the natural perception of increase in sound levels by humans.