In video technology, a technique used to improve contrast and picture clarity by flattening the camera response to 400 lines (by aperture correction) and applying an additional correction to increase the depth of modulation in the range of 250 to 300 lines (in an NTSC system,) both vertically and horizontally. Note: Image enhancement produces a correction signal with symmetrical overshoots around transitions in the picture, but it must be used sparingly if natural appearance is to be maintained.