Pioneering Franco-American filmmaker Alice Guy was never completely forgotten.

Her movies would be mentioned by legendary directors like Hitchcock and Eisenstein in their memoirs.

Every so often, over the decades of her life and in the 50 years since her death, some archivist or historian would seek to give her the due she was owed — first female writer-director-producer-editor, first female head of production, etc.

But the slights, omissions and outright sexist erasures of her name from the historical record ruled the day — a century of days. And this prolific, artistically and politically daring woman, whose story “dates back to 1896,” she says in an old black and white (1964)  French TV interview, could never quite take her place on the pantheon of Inventors of the Modern Cinema.

Until now.

“Be Natural: The Untold Story of Alice Guy-Blaché, the First Female Filmmaker,” begins with Alison McMahan’s 2002 book, “Alice Guy-Blaché: Lost Visionary of the Cinema”‘ and dives into globe-trotting original scholarship, filling the screen with some 138 interview subjects and mountains of primary source (written and film) material.

Filmmaker Pamela B. Green’s film resume was, before this, mostly concerned with creating and consulting on the credits of movies. She’s made a thorough, entertaining and eye-opening documentary about a woman writer-director often robbed of her credits — 1000 films, shorts from the prehistory of the cinema to sound features — who worked in a time before “Written, Produced and Directed by” was invented and noted on the screen.

“Be Natural” — the film takes its title from a huge slogan written on the proscenium of the stage where Guy shot many of her American films, at Solax Studios in Fort Lee, New Jersey — is one of the great works of motion picture historical scholarship.

From its fanciful scene-setting “post card” packed opening credits to a flourish of a finale — the recreation of one of Guy’s earliest single shot comedies, filmed on vintage equipment and starring Chris Kattan and Horatio Sanz — “Be Natural” is a film buff’s dream of a documentary and an absolute delight.

You can catch a hint of incredulity in Oscar winning narrator (and producer) Jodie Foster’s voice as she and Green (who did the interviewing) relate the history of film REWRITTEN with Alice Guy, later Alice Guy Blaché’s groundbreaking contributions finally included.

“Be Natural” she commanded her actors at a studio she designed and built (another first) with her then-husband. And the snippets of celluloid generously sampled here, the result of a worldwide search of film collectors and archivists by Green & Co., often back that up.

There was no avoiding the posing and presentational acting of her day. Remember, Queen Victoria was still living when Guy got her start in 1896, and when she made her first noteworthy scripted film — 1899’s “The Cabbage Fairy.”

But by the time she was making movies in America (her husband Herbert Blaché relocated them), the subtlety was obvious, the “feminism” overt and a sense of cinematic style all her own can be detected.

Green fills the screen with a mosaic of actresses, movie makers, studio execs, honchos and historians, and lets scores of them declare they have no idea who this woman was.

Most of them, anyway.

A great conceit of her movie is using that mosaic to zoom in on say, actress-director Lake Bell or Evan Rachel Wood, or a special effects specialist or “Wonder Woman” director Patty Jenkins, to ask a question about Guy’s life — her process, her business acumen, how she handled being a working mom (in the U.S.) at a time when there were no other female filmmakers and relatively few working mothers.

Green and her team then set out to answer those questions, tracking down descendants (first contacted, on camera, by phone), digging through souvenirs, scrapbooks, boxes of memorabilia. She talks to expert archivists, tracks down a 1980s video interview with Guy’s daughter and chases down names from Guy’s old address books.

This is Scholarship 101, working your way up to primary sources (hand-written notes, old scripts, a Legion d’honneur a descendant has stashed in his home archives in Arizona).

History buffs and film buffs will be tickled, as I was, at this detail — the research detective work we see unfold in the film.

There’s no footage of the woman, in her prime, extant. But is there? An old “Kinora” flip-book style animation of her from the very early 1900s is shown to a police facial ID expert, who breaks down how he determines identities and positively names Guy as the subject of the “film.”

She was a secretary for Leon Gaumont, present at one of the earliest demonstrations of the Lumiere Brothers’ pioneering projection system, the cinematographe, in 1895.

By the next year, she was shooting film for the studio that would come to be called “Gaumont” and which she would run, and within three years she was making one of the very first “scripted” motion pictures ever made — in Paris.

When actress Julie Delpy and others wonder how she could have overcome the gender restrictions of her day, we’re reminded that Guy filmed a comic cross-dressing spoof, “The Consequences of Feminism” — in 1906!

Historians take us on a walking tour of the locations Guy made movies on in Paris, their trek charmingly fading into footage of the actual movie on that same location over a century before.

It’s dazzling.

She gave the first female American director (an actress) her big break behind the camera, lectured at Columbia University and was instrumental in getting many of the first synced-sound movies — “music videos” of the day — on celluloid.

Unlike Edison, whose filmmakers tried to shoot and record-singing etc. direct to disc on the set simultaneously, Guy had the foresight to record the vocalizing first, and then have the singer lip-sync to it.

Another first!

Guy has been, as I mentioned earlier, resurrected before. There was a French TV documentary about her in 1964.

But as soon as that had aired, she was all but forgotten again, swept under the rug by male film scholars working in a more primitive (pre-Internet) time for researchers, when many of Guy’s films were simply lost and all they could work with was sketchy prior research and hearsay.

The implication, that they were only too eager to do this (Cinematique Francaise founder, curator and historian Henri Langlois, who KNEW her, all but denies her existence in one archived interview) out of sexism, is inescapable.

But Pamela B. Green, adding to the growing mountain of knowledge about Alice Guy Blaché, ensures that this oversight will not stand.

A film professional known for creating movie credits makes certain that this pioneer finally gets the credit she’s been due for over 120 years.

“Be Natural,” from the moment of release, becomes one of the seminal documentaries on early film history and must-see movie watching for any serious cinephile.

MPAA Rating: unrated

Cast: Narrated by Jodie Foster, with Alice Guy, Patty Jenkins, Evan Rachel Wood, Catherine Hardwicke, Jon M. Chu, Diablo Cody, Martin Scorsese, Agnes Varda

Credits:Directed by Pamela B. Green, script by Pamela B. Green and Joan Simon. A Be Natural release.

Running time: 1:43