Display brightness adjustment apparatus and methods are described in which the average brightness of a display may be scaled up or down using a non-linear function. When applying the non-linear function to scale down brightness, the contrast of the output signal may not be reduced so that the dynamic range and highlights are preserved. The non-linear brightness adjustment may be performed automatically, for example in response to ambient light level as detected by sensor(s), but may also be applied in response to a user adjustment to a brightness control knob or slider. The non-linear brightness adjustment may be performed globally, or alternatively may be performed on local regions of an image or display panel. The non-linear function may be a piecewise linear function, or some other non-linear function.