I wonder if this is the total running time of the VHS Director's Edition, which contained a brief EPK piece on the film, since the only alternate versions listed on IMDb are foreign versions that contain a brief summary of STII and III. I doubt such a summary would take 18 minutes, or be part of a Director's Cut.
A "director's edition" of the film came out on VHS in the early 90s, and contained the movie, same as it was released to theaters and on earlier VHS, along with a featurette with Leonard Nimoy talking about the making of the movie. That same featurette is on both DVD editions. There is no longer cut of the movie that I have ever been aware of. IMDB is probably referring to the director's VHS edition.
...or the laserdisc, which was part of the Paramount "Director's Series" label of the time, in which letterboxing was used and described/justified by the director on camera before the film.
There has never been a cut released of ST IV other than the theatrical.
There was a longer version of Star Trek IV. I owned it on vhs. As Stephen mentioned on this thread it was a pre-credits summary of events in Star Trek II & III, can't have been more than a 3-4 minutes long. But it was interesting to watch those scenes with Leonard Rosenman's music instead of Horners. The title of the film was displayed differently too, The Voyage Home in large font, with Star Trek IV smaller font below.
I remember that title sequence from a pan'n'scan VHS copy I rented ages ago that also had the summary. I've never seen it since so I thought it was a figment of my imagination.
The summary is on my widescreen VHS as well, but there the opening titles are the same as on the DVD.
Right. It was to help foreign audiences catch up on the story from previous films. It is not a "Director's Cut." Nimoy has said that the original theatrical cut is his final version. He doesn't want to make any changes.