A) Amplitude compression of the signals corresponding to the white regions of the picture, thus modifying the tonal gradient.

b) The reduction in gain applied to a picture signal at those levels corresponding to light areas in the picture, with respect to the gain at the level corresponding to the midrange light value in the picture. 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.

The overall effect of white compression beyond bandwidth limiting is to reduce contrast in the highlights of the picture as seen on a monitor.