"They Shall Not Grow Old" is a tribute paid by the present to the past, and what a gorgeous gift it turns out to be.
The past is the army of invariably anonymous British soldiers who brought bravery, stoicism and grit to the years of trench warfare on the Western Front that made World War I a cataclysm unlike any seen before.
The present is the kind of extraordinary state-of-the-art computer-generated special effects typically used to make invented superhero antics feel more real they have a right to.
Orchestrating this exceptional past-present hookup is Peter Jackson, director of "The Lord of the Rings" and "The Hobbit" trilogies, a master narrator who uses his feeling for visual detail and interpersonal drama to make those departed men feel as alive as you and me.
The documentary began because of Jackson's love of and devotion to his own grandfather, who served with the 2nd South Wales Borderers during the conflict.
Himself very much a World War I buff who even collects vintage aircraft, Jackson was immediately energized when Britain's Imperial War Museum asked him if he would be interested in doing a film to commemorate the 2018 centenary of the armistice.
In fact, as it developed, the project so involved Jackson that what was to be a 30-minute short developed into a 99-minute feature that earned an impressive $730,000 at the box office during its one-night-only debut in Britain in October.
In case you've never seen rickety black-and-white World War I era newsreel footage, "They Shall Not Grow Old" starts with a glimpse of it, which makes what it ends up with that much more impressive.
The years-long project, which involved both the Park Road Post Production company in New Zealand and Stereo D in the U.S., was enormously complicated on both a visual and audio level.
After receiving hundreds of hours of footage from the museum, whose archive is among the world's largest, the first order of business for Park Road Post was cleaning the film up, removing dust, scratches, tears and other flaws.
Then there was the tricky question of timing, of getting footage that was hand cranked at a variety of speeds to all sync up to today's 24-frames-per-second standard without looking speeded up or slowed down.
Next came colorization, a process that went to extraordinary lengths to achieve accuracy, including trips to actual footage locations to take thousands of reference photos. No detail, not even the color of a button, was too small to get right.
The same kind of meticulousness went into the soundtrack, where sounds like horses hooves and footsteps in the mud were layered in.
Where soldiers could be seen talking to the camera, lip readers were employed to figure out what they were saying and local actors hired to make sure the accents were correct.
Also on the audio side, once Jackson and his team decided against conventional narration, they reached out to the BBC archives, which had 600 hours of WWI veterans talking. All of it was painstakingly listened to, with the voices of more than 100 men used extensively in the film.
Once the last step, the conversion to stereoscopic 3-D, was taken, the creaky footage was so transformed that the lifelike realism that resulted is little short of reincarnation.
Instead of feeling like we're looking at ancient times, we see these men as our contemporaries, flesh of our flesh. Jackson has said that he feels that "restoration is a humanizing process" and you can unmistakably see why.
Persuasively edited by Jabez Olssen, who makes what must have been an impossible job look easy, "They Shall Not Grow Old" tells this story chronologically, starting with eager young enlistees and ending with inevitably wiser veterans.
One of the fascinating through lines is that almost all the soldiers - and some were as young as 14 or 15 - enlisted because they thought it would be an adventure, over within months and too exciting to be missed.
They soon found out differently, and we hear about the desolation, the dead bodies, the rats, the lice and the poison gas.
We hear about things rarely mentioned, like the existence of brothels in almost every French town, and also see images rarely seen before, such as a row of men sitting on a log over an open pit that functioned as a one-size-fits-all latrine.
We also, perhaps most poignantly, hear what these men thought after the war, when civilians had so little idea of what they'd experienced that talking to them proved futile. One gift of this exceptional film is that we in the future can see their wartime lives more vividly than their contemporaries ever could.
This article is written by By Kenneth Turan from The Los Angeles Times and was legally licensed via the Tribune Content Agency through the NewsCred publisher network. Please direct all licensing questions to email@example.com.