abstract:The pillarbox effect occurs in widescreen video displays when black bars (mattes or masking) are placed on the sides of the image. It becomes necessary when film or video that was not originally designed for widescreen is shown on a widescreen display, or a narrower widescreen image is displayed within a wider aspect ratio, such as a 1.
But you sacrifice a bit with 16:9 because they force traditional programming into a pillarbox format, with black bars on both sides--and if you're not careful, the bar pattern can burn itself into the screen.