Apparently the cinematographer's 70mm print is more or less the ONLY good film element that survives, which is why they're using it. (The OCN is apparently lost and the surviving 35mm prints are in bad shape.) They made a 70mm blow-up because at the time it was the most practical way to get the best possible sound because it was the only format that would use a magnetic audio track.
― birdistheword, Thursday, 9 March 2023 01:00 (one year ago) link