Originally posted by: triffid I do not know anything about converting of UMD to DVD. But did you ever checked the normal 4:3 tapes and TV versions? They often offer small portions of picture above and below, not seen in the WS editions. This happens when the 4:3 release is "independent" on any WS version coming out at the same time. I must admit I never tried to study any Alien movie from this point of view, but I found this anomaly in T2 for example.
This usually only happens if the film was shot on super 35 - the larger frame offers separate composition options for 4:3 and 2.35:1. T2 is actually a famous example - there's a demo of the process on the old laserdisc (and, I believe, the Ultimate Edition DVD).
Anyway, in the case of Alien, which was shot in standard 35mm Panavision, there won't be so much 'overhead' but there's always a bit more vertical information on the original negative than is transfered to the release prints (and conventional widescreen tapes/discs), so there's potential for slight re-composition. I'd like to see a side by side example...