A decreasing of the raster size (H and V) so that all four edges of the picture are visible on the screen. Underscanning allows viewing of skew and tracking that would not be visible in normal (overscanned) mode. It is also helpful when aligning test charts to be certain they touch all four corners of the raster. Likewise, when checking the alignment of multiplexer images from a film chain, underscan allows proper framing of the projected image going into the video camera.

Decreases raster size H and V so that all four edges of the picture are visible on the monitor.

Video monitor that can reduce the size of the video image so the four outer frame edges can be viewed in their entirety.