It’s one of the most thankless, unsung jobs at any newspaper, and one of the hardest.

Obituary writers make value judgments, about whose life and achievements or simple notoriety is worthy of “500, 800 words,” and whose isn’t. And they spend a frantic few hours, trying to reach grieving loved ones and peers, sifting through legions of “facts” often provided by people’s faulty memories or the family circle exaggerations of the deceased.

Because God forbid they get something wrong. This is, as one obit writer in the fine new documentary “Obit” puts it writing someone’s history “at the very moment they become history.”

Filmmaker Vanessa Gould naturally chooses The New York Times as the setting for her film, focusing on one of the last newspapers with a staffed obituary department, veteran writers who specialize in collecting information about the recently-deceased, from popes and tyrants to pop stars, inventors, adventurers and crooks.

Blending documentary footage of some of the subjects — a Transatlantic rower, a stripper-girlfriend of Lee Harvey Oswald shooter Jack Ruby, a political aide who made sure Kennedy looked better than Nixon for those historic 1960 TV debates — with interviews of those who wrote them, Gould creates a fascinating portrait of the work and the patient, harried and detail-oriented folks who do it.

There’s a formula for an obituary, we learn. Typically, there’s just a single sentence that mentions death. Some are “news” obituaries, others more colorful feature story obits, with anecdotes and laughs, even, in their lines.

Bruce Weber comes off as a man who loves to talk. He sits on the phone, collecting first the hard fact details that the obituary will be built upon. We only hear his half of the conversation as he asks survivors “Was he married, and how many times before you? Could you spell that for me?”

A proper newspaper obituary, not the fluff provided by a family to a funeral home for publication, is filled with facts. People embellish their war records, their athletic achievements, their “firsts.” Nailing down what is true, on deadline, when the person who best knows that truth is dead, is tricky business.

Weber will make a mistake, and most newspaper reporters will spot it the moment he makes that assumption during a phone interview. But that’s what “Corrections” are for.

The staff — editor William McDonald and others — talks in the jargon of the “press,” whether a notable deserves an “above the fold” (front page, top half) remembrance, or a “refer,” an obituary mentioned on the front cover but printed inside.

The lonely keeper of “The Morgue,” the newspaper’s vaunted archive of stories, clip files and photographs, tracks down images from the distant past and previously-reported stories on the subject of this or that obituary.

Writers recall the harrowing rush to get something into print after sudden deaths — Michael Jackson, Prince, Robin Williams, Philip Seymour Hoffman. And each relishes the grace notes of a particularly distinct life rendered in just the right keystrokes, when they have time to make an obituary “sing.”

Margalit Fox, once an aspiring cellist, loves alliteration and has a touch of the poet about her. When detailing the life of one of the last typewriter repairmen in North America, Manson Whitlock, she turns “the ffft of the roller, the ding of the bell, the decisive zhoop … bang of the carriage return, the companionable clack of the keys” into the music of the man’s life.

It’s not the most cinematic of subjects. And the film, like most recent documentaries about newspapers, has a New York myopia about it.

But the anecdotes, about tidbits, old family photos, that perfectly summed up that person’s story, or the blunders (you’ve GOT to confirm somebody is actually dead) make “Obit” in itself a fine piece of “instant history” for a profession that is itself going dying out.

And when newspapers, and these reporter/writers are gone, who will be there to sum up a life — notable or notorious — in 800 words or less?

MPAA Rating: unrated, with mild profanity

Cast: Bruce Weber, Margalit Fox, William McDonald, Paul Vitello

Credits:Directed by Vanessa Gould. A Kino Lorber release.

Running time: 1:35