a) Data Transmission: A process in which the effective gain applied to a signal is varied as a function of the signal magnitude, the effective gain being greater for small rather than for large signals.

b) Video: The reduction in amplitude gain at one level of a picture signal with respect to the gain at another level of the same signal.

Note: The gain referred to in the definition is for a signal amplitude small in comparison with the total peak-to-peak picture signal involved. A quantitative evaluation of this effect can be obtained by a measurement of differential gain.

c) Production: A transfer function (as in gamma correction) or other nonlinear adjustment imposed upon signal amplitude values.