You have to convert the footage to a letterboxed 4:3 image. This takes the 16:9 footage, and puts black bars (letterboxes) at the top and bottom, making the whole image, including the black bars, have a 4:3 ratio. The problem with this is that you actually lose resolution in the actual image, because the normal NTSC resolution includes the letterboxes. Plus, if you play it back on a 16:9 monitor that doesn't have a letterbox option, you either end up with the whole image, including the letterboxes, stretched across the width in 16:9 mode, or a smaller 16:9 image with both the letterboxes at the top and bottom, and pillarboxes on the left and right (what you see when you playback 4:3 footage on a 16:9 screen). If you are going to be playing your footage on 4:3 monitors that can't compensate for the 16:9 image, then you should make a letterboxed version for those situations. Most DVD players, however, are able to convert 16:9 footage to letterboxed, so if you're playing it on a DVD, it shouldn't be a problem. I hope this helps. Sometimes I have a hard time explaining things, so if none of this makes sense to you, it's probably more my fault than it is yours. Try googling "16:9 anamorphic" and "letterboxed" and see if you can find any websites that explain it better.
