The rollout of Peter Jackson’s new documentary, “They Shall Not Grow Old,” has been a little confusing: made as a documentary for Britain’s Imperial War Museums, with the support of the BBC, it’s being distributed in America by the Fathom group in a series of one-off, multi-venue screenings—as special events rather than continuously playing entertainments. Already, after some December dates, a new screening has been scheduled for late January, and presumably more are in the offing, if not a full-scale theatrical release. It seems like a film that one can see if one wants to see it.

And it should be—must be!—seen. The director of the (Tolkien-betraying, but let that go) “Lord of the Rings” series was asked several years ago by the Imperial War Museums to do something entirely new with their vast archives of footage of First World War soldiers and soldiering in order to celebrate, or at least eulogize, the centennial of the Armistice. Almost no film exists of actual battles, the hand-cranked cinematic equipment of the era being too difficult to move into combat, but there is much footage of trenches and encampments and daily life (including some hair-raising—or, rather, rear-baring—images of improvised latrines).

Jackson, a Great War aficionado (his grandfather, to whom the film is dedicated, fought in it), decided, wisely, to make the film entirely from the old footage coupled with firsthand audio testimony from survivors—recorded over the years, for the most part, in countless BBC memorial broadcasts. The vocal witnessing, beautifully vivid, is straightforward. The only narration we hear are the voices of the men who fought the war, so the film is blessedly free of the sapient sounds of experts and academic historians.

But the visual record is the heart of the film. With enormous audacity, Jackson and his team in New Zealand decided, in addition to restoring the footage, to “modernize” it, not merely regularizing its often staccato beat—that familiar jerky rhythm of old silent footage, produced by a mismatch of the speed at which the film camera was turned with the speed at which it’s projected now—and cleaning up its sometimes over- or underexposed light, but actually “colorizing” it to match the palette of the Western Front, and adding, in many places, an audio track carefully synched (with the help of lip readers!) to the ancient footage.

Jackson artfully has the opening sequences in the film, about the recruitment and training of Brits for the Army (early in the war, they were all willing and even eager recruits, conscription being introduced only in 1916) pass by in black and white. Only at the arrival of these men on the Western Front in Belgium and northern France does the footage spring into color—and, with a painstaking attention to detail, the colors are exactly the washed-out gray-greens and mud browns of the Belgian front, with every square of British khaki, and, occasionally, German gray, lovingly recreated. (Jackson took scouting trips to the sites of the war, and, wherever possible, found the precise locations where the footage that he was recycling had been taken, and then photographed the landscape on site in order to match it, earth tint for earth tint, in the lab.)

The result is, in its way, as eerie and enthralling, albeit with a completely opposite emotional valence, as the moment in “The Wizard of Oz” when Dorothy’s world goes from black and white to color. There, it means the coming of magic; here, it means an entry to Hell. The immediacy and sudden contemporaneity of the film makes one feel the inferno of the Western Front as one never quite has before. Mud and rats, sandbags and trenches, sniper fire and mortar attacks—all of these things that we’re accustomed to experiencing abstractly through a distancing veil of archaisms and antiquity are suddenly real before us. Even as many shots effectively introduce camera movement, so that the cameraman seems to have a light, modern Sony on his shoulder, we see, or think that we’re seeing, the war for the first time, as the poor soldiers saw it. (In those places where no footage was taken or survives—that is, exactly in pitched battle—Jackson uses, less effectively, illustrations from wartime magazines, which show just how rhetorical and stereotyped even documentary-minded drawing had to be. In place of the frightened, scuttling everymen we see in the film, the magazines show us bold British warriors, heads up and mustaches flying, annihilating the Hun.) Though the immediacy of the imagery is in itself astounding, the addition of a vocal track only adds to the effect. For one unforgettable moment, the fruit of insanely obsessive labor, Jackson tracked down the precise words spoken by an officer to his troops just before the battle of the Somme, and so, for the first time in a hundred years, we “hear,” dubbed in, what’s being said, the officer’s lips suddenly coming to life with words long ago swallowed up in air.

The moment is unforgettable. Yet one need not be a media-studies major, or maven, to also feel, and then raise, some unsettling questions about the film’s approach and the achievement. We congratulate ourselves on the effective updating—on how we now can see the war as it was seen by those who fought it. But no truth is truer than how the look or sound of what seems eerily convincing changes radically as technologies change. As I once wrote for the magazine, a famous and apparently accurate story has it that a scratchy first-generation Victrola of a soprano singing, placed behind a curtain, was accepted by a circa-1900 audience as absolute fidelity. We adjust to the technology of our time as much as it adjusts to us.

Jackson asserts, reasonably, that if the cameramen of the Great War could have shot in color with sound, they would have. But such choices are trickier historically than they may seem. Most people looking at black-and-white footage of the war while it was going on never thought, Oh, if only this were in color, with sound! Any more than looking at it with color and sound now, we say, “Oh, but if only you could smell it!” The medium shapes our response to it. Those first viewers were overwhelmed by the fidelity and the truth to nature of early film, shocked by the intensity of its realism—which indeed it fully possessed, compared to the woodcuts and stills of the American Civil War period, which were, in turn, shocking in their verisimilitude to their first observers. (And those Civil War stills can remain dramatic and weighted for us, by that adjustment of expectations that is exactly what we mean by an educated eye.)

More deeply still, the means by which a period represents itself to itself is part of the period. One of the most striking elements of the old footage is that one sees the soldiers, in the midst of their nightmare, smiling sheepishly as they realize that, for the first time in any of their lives, they are the subjects of a movie camera. The reality that the soldiers are in simple awe of the presence of a movie camera, even as they prepare for their ordeal, is in itself a crucial fact about the period, which the black-and-white footage helps us understand exactly in its nascent, baby-steps nature. When it comes to film, at least, black-and-white and silent are the way the period saw itself, understood itself, made sense of itself. By altering that mirror, we fail to see the subjects staring into it quite accurately.