It has been suggested in the past that adaptation effects may serve a useful role in perception. This paper shows that if the adaptation process follows a simple scheme, called proportional gain adjustment, then it can fulfil two useful functions: correction of errors and recalibration. The proposed scheme controls the gain of the system. Although it is memoryless, it ensures a setting of the gain at such a level that the average of the measured signal in the environment is always mapped onto a fixed internal representation. The proportional gain adjustment scheme is discussed in the context of single-band multi-channel models, and is shown to exhibit various phenomena associated with visual adaptation.