The maximum image size, in pixels, on a DVD is fixed. On a non-anamorphic DVD the aspect ratio of the picture is 4:3, which means on a widescreen movie like Wing Commander a lot of those pixels end up in the black border on the top and bottom. On an anamorphic DVD the aspect ratio is 16:9, which is a lot closer to Wing Commander's 2.35:1, so more pixels are available to the actual picture, and less to the border.