A tragic 1996 expedition to climb Mount Everest, the tallest peak on the globe, is the subject of Baltasar Kormakur’s film. From the technical perspective “Everest” is a most impressive achievement; it looks and sounds great, at least in the IMAX 3D version available in select theatres. If only it were as compelling as drama as it is in technical terms. Unhappily, from the emotional perspective it’s pretty much a slog.

The story of the ill-fated climb has been told in print by several of the survivors, most notably in Jon Krakauer’s “Into Thin Air” (which itself was the basis of a TV docudrama). The screenplay by William Nicholson and Simon Beaufoy cites none of those accounts as sources, and some of its scenes are clearly speculative, while others push the boundaries of melodrama pretty strenuously. By and large, however, it aims for an attitude of sober authenticity, and in terms of appearances certainly achieves it.

Unfortunately, what that means is that the film lacks focus as a battery of characters major and minor compete for attention. By the mid-nineties the scaling of Everest had been transformed from an impossible dream or a grand achievement into a sort of extreme tourist trip, and multiple groups of paying participants assembled to make the ascent under the aegis of a variety of guide outfits. The one on whom the script concentrates is Adventure Consultants, headed by Rob Hall (Jason Clarke), a man intent on the safety of his customers. Leaving behind his pregnant wife Jan (Keira Knightley), he takes his latest pack of climbers to Kathmandu to scale the mountain. He’ll lead the expedition up the peak while the event organizer Helen Wilton (Emily Watson) and fellow guide Guy (Sam Worthington) keep tabs on them from base camp.

The group is a fairly large one, but the most notable members are Beck Weathers (Josh Brolin), a brash Texan; Doug Hansen (John Hawkes), a spindly mailman from Seattle who’d failed to reach the summit the preceding year and is determined to do so now; Yasuko Namba (Naoko Mori), a forty-seven-year old woman who’d already scaled six of the “seven summits” and wants to complete the list; and Krakauer (Michael Kelly). The latter’s presence with Hall’s group causes some initial friction with Scott Fischer (Jake Gyllenhaal), the scruffy head of an alternate guide company called Mountain Madness, with which Krakauer had originally booked. But those differences are quickly smoothed over, and Hall and Fischer are soon working together to try to manage the bottleneck caused by the sheer number of climbers, including those in a third group led by Russian Anatoli Boukreev (Ingvar Sigurdsson). But these are only the major figures in front of the camera. There are numerous others who clutter the frame in much the same way that they seem to have overpopulated the slopes.

“Everest” does a decent job covering the planning prior to the actual climb—physical training and step-by-step ascents to prepare participants for the final effort, even if some of the characterizations—Brolin’s in particular—come off as overdrawn. (You’d think that Weathers was a figure from the old “Dallas” TV show.) The footage of the ascent, shot in various locales, including Italy, is excellent, even though it’s not always easy to discern whom the camera is focusing on at many points (Salvatore Totino was the cinematographer).

But problems intrude in the final act, when an unexpected storm strikes just after some of the climbers have reached the summit. (By that time Weathers had been struck with snow blindness and had to remain behind on the trail.) It’s here that the melodrama appears. Hansen, who’s still struggling to reach the peak (and has been suffering respiratory problems from the very beginning) refuses Hall’s directive to turn around short of the summit, and the guide aids him, despite misgivings, to get to his goal. But the men are then trapped in the storm and, after Hansen collapses, can’t make their way back to camp. The scripters must have devised the interaction between them on the basis of probability alone, since neither survived and no one else was present to observe it. And things get especially corny when Helen and Guy patch Jan through to her husband, who’s trapped on a ledge, and even more so when Weathers’ wife (Robin Wright) gets on the phone to ambassadors and other government types and demands that they send help in to rescue her husband, no matter how expensive or dangerous it might be. Those segments are overplayed so broadly—as, unfortunately, is typical of most Hollywood material set in Texas—that they might have come out of a bad sitcom.

Apart from that, however, much of this last-act material is simply chaotic. With the exception of Hall and Hansen and Weathers, it’s difficult even to know what’s happening to whom, let alone where on the mountain it’s occurring. The event itself was undoubtedly chaotic, but it’s up to the filmmakers to clarify it for us, and they don’t manage to do so. Even worse, the characters with whom we’re meant to empathize most—Hall, Hansen, Weathers—have been so sketchily drawn that one has difficulty fully identifying with them, especially since, to be perfectly frank, they all decided quite voluntarily to place themselves in their predicament.

In spite of the obvious commitment of cast and crew, therefore, “Everest” manages to reverse the old cliché and turn a mountain into a molehill. A postscript: anyone interested in the history of expeditions to Everest should check out the DVD of the British Film Institute’s superb restoration of John Noel’s amazing 1924 documentary “The Epic of Everest,” recording the trek that took the lives of George Mallory and Andrew Irvine. Technically, of course, it can’t match Kormakur’s film. But it’s actually more haunting an ode to the lives the peak has taken.