Can someone please describe to me how a 4:3 HD television displays a HD 16:9 signal? I understand that the image is usually letterboxed. Does this letterboxing lower the effective vertical resolution of the image? In other words, given a 4:3 HDtv with a 1080i native resolution, are those 1080 vertical lines used to draw the letterboxes, thus lowering the number of lines left over for the actual image? Or is a 4:3 HDtv capable of displaying the full-resolution 16:9 image in a letterbox format?