Sidney Poitier’s two most iconic moments as an actor both occur in the 1967 Oscar-winning drama “In the Heat of the Night.” The first is his famous declaration “They call me Mister Tibbs!” The second arrives when his big-city detective is questioning a Mississippi cotton tycoon, who slaps Tibbs for implying that he’s a criminal. Tibbs slaps him back — an act of shocking-at-the-time defiance that Poitier improvised, and one that gave a jolt to film history. It connected, electrifyingly, with the militancy of the late ’60s, and left no doubt that Poitier was a figure of mythological magnitude.

As the first Black movie star, the Jackie Robinson of cinema, the trailblazer who always felt (by his own admission) that it was his obligation to represent, Poitier changed the movies with the very fact of presence. Yet it was the meaning of his presence, the ferocity and containment of it, the twinkling Bahamian-bred charisma and haunted depths, that made Poitier’s landmark status so much more than the word “first” implied.

At times, there was a perception that Poitier, due to the groundbreaking nature of his stardom, played characters who were rigorously (and perhaps overly) idealized, walking role models who may have been a bit too perfect for their own good. Yet that’s actually a specious view of Poitier’s fulsome artistry — the liquid emotional dance of it. Because if you really drink in his performances, what you see is an actor of radiant moods and magnetism who injected the mostly good men he played with dimensions of anger and pleasure and doubt and despair that vibrated onscreen.

That quality was there from his first feature, the film noir “No Way Out” (1950), and it’s there in “The Defiant Ones” (1958), the movie that made him a star, where as an escaped prisoner handcuffed to Tony Curtis he confronts the racism that surrounds him with a combustible storm of fury. It’s there in his extraordinary performance in “A Raisin in the Sun” (1961), where Walter Lee’s scheme to use his mother’s insurance money to open a liquor store becomes a cry of agony from a man trapped in a system that gives him “freedom” but won’t let him breathe. It’s there in “Lilies of the Field” (1963), the movie for which Poitier became the first Black performer to win an Academy Award for best actor; the movie is a trifling piece of kitsch, but Poitier, as a wanderer who builds a chapel for some German nuns in the middle of the desert, swings the feel-good scenario like jazz. It’s there in “The Long Ships” (1964), where he plays a Moorish king with James Brown hair and the reptilian gaze of a Shakespearean killer.

And it’s there in the delectable triptych of performances Poitier gave in 1967 — “In the Heat of the Night,” “To Sir, with Love,” and “Guess Who’s Coming to Dinner,” which became a kind of Poitier mood ring: control in the face of hate, grace in the face of slovenly rebellion, ebullient slyness in the face of a liberal culture that only pretends that color doesn’t matter.

Much has been made of how Poitier never stopped giving back — through his activism, his courage under pressure during the Civil Rights era, the moral authority that ruled him offscreen and on. Yet the ultimate giving back was there in his movies, where even his quietest acting is lit by the fire of purpose. In the ’70s, just when it looked like he’d lost his relevance, he directed and starred in a trio of street-smart comedies, notably “Uptown Saturday Night” (1974), that took the cinematic world made possible by the blaxploitation revolution and infused it with a sweet sin of humanity that was pure Poitier. In the end, what he gave us can scarcely be measured, because he changed the movies by changing what Black people could imagine themselves being, and in doing so he changed the world.