In his narration for “The Great Buster,” Peter Bogdanovich recalls being a younger cinephile watching Buster Keaton in 1969’s “Free and Easy,” dismissing the work of the great comedian late in his career by comparing it to his heyday in the silent era. It’s a revealing moment for the filmmaker for whom surely many have compared his contemporary output to his prodigious start with such instant classics as “The Last Picture Show” and “Paper Moon,” reflecting on how unaware he was at the time of the box Keaton was working out of at the time, suddenly at the mercy of another director who wasn’t in touch with showcasing Keaton’s brilliant physicality as the comic was and taking jobs in lesser productions or even gigs on “Candid Camera” or “This is Your Life” as a result of not having much of a retirement plan, thanks to coming up at a time to build the industry’s infrastructure but not necessarily benefit from it.

A familiarity with the arc of Bogdanovich’s own career isn’t necessary to enjoy “The Great Buster,” which admirably charts the ups and downs of Keaton’s as buoyantly as one of his golden era films such as “Seven Chances” or “The General,” but it does speak to why it’s as affecting as it is. Playing up the role he’s relished in later life as a raconteur of Hollywood lore, he offers up a dishy history of how the comedian’s personal and professional lives informed each other while drawing on his pre-directing career as a film programmer and historian to carefully analyze scenes in Keaton’s films much like he did in 1971’s “Directed by John Ford,” explaining why they work as well as they do. At first glance, one might think the eclectic array of interview subjects are people Bogdanovich has told these stories to before – complete with impressions – at parties, but while packing in too many to name, the film yields intriguing observations from Jon Watts, who acknowledges looking to Keaton for help with “Spider-Man: Homecoming” where his main character had no expression but his eyes and Quentin Tarantino appreciating Keaton’s masculinity when most comedians often played being weak and helpless for laughs.

However, beyond knowing the right people to talk to — Richard Lewis, as a friend of Keaton’s third and final wife Eleanor Norris, is one of the surprisingly revelatory interviews — Bogdanovich’s insight into how forces having nothing to do with Keaton’s filmmaking abilities shaped his career is both enlightened and enlightening. He dutifully acknowledges the alcoholism and the particularly poor choice made at a career crossroads to give up his independence to sign with MGM that would haunt him, yet somehow these acknowledgements only strengthen how special the magic he could conjure onscreen was, usually working against the laws of physics, but many times against himself to give everything he could to an audience. Rather than adhering to a naturally chronological timeline, Bogdanovich chooses to save Keaton’s triumphs for last, cheekily saying “We’ll get to that later,” after recounting his rise to to highest heights of Hollywood midway though as an act of compassion, but also aware that when all else fades away, this is what history will remember. To that end, he couldn’t have received a better biography.

“The Great Buster” opens at the Nuart in Los Angeles on October 16th.