According to
editor Gordon Stainforth's comments here at the Kubrick FAQ (scroll down just a little, it's the first question) the film was intended to be screened in theaters in the 1.85:1 ratio, which I presume is what you see on the widescreen DVD (which I'm burning to get, but I haven't got HD TV yet, so it makes little sense to buy it right now). Kubrick seems to have preferred the "fullscreen" ratio for video releases in his lifetime, though who knows what he would think by now. This FAQ kept me up for hours when I first stumbled on it, so beware.