"Birdman" tells the story of an actor (Michael Keaton) struggling to mount a serious play on Broadway while his superhero identity haunts him. (Fox Searchlight)

“That’s what I love about these high school girls, man. I get older, they stay the same age.”

That line from Richard Linklater’s classic 1993 comedy “Dazed and Confused” came back with an ironic vengeance this week, and die-hard fans of the film will know why: It’s spoken by a 20-something stoner named David Wooderson after a cute-looking teenager walks by. Wooderson is played by Matthew McConaughey, and the girl is a young actress named Renee Zellweger.

While McConaughey has been trotting a victory lap of his “McConaissance” the past few days, doing publicity for the upcoming sci-fi blockbuster “Interstellar,” Zellweger experienced a very different kind of publicity: Shortly after walking the red carpet at an event in Hollywood on Monday, photos of her went viral, with commenters speculating that she had undergone plastic surgery, then quickly moving on to how successful or disastrous said procedure was. Within the span of a few hours, it seemed, Zellweger became a one-stop trope for the tyranny of sexism and appearance in Hollywood, where the system is notoriously unforgiving of women who dare to age. As Slate’s smart, observant columnist Amanda Hess aptly noted, “Plastic surgery is fake. So is the Hollywood fantasy where women over 40 just don’t exist.”

As punitive as movie culture is for actresses, it’s no cakewalk for men, either. In “Birdman,” opening Friday, Michael Keaton plays Riggan Thomson, a middle-aged actor whose heyday as a cartoon action hero has long since passed; in an effort to reignite his career, he directs and stars in a Broadway play. “Birdman,” directed as an exhilarating single shot by Alejandro González Iñárritu, chronicles the days leading up to the play’s opening, as Keaton’s character is plagued by self-doubt, thwarted artistic ideals and an unrequited longing for the potency he’s lost as a big-screen action star.

Thomson’s anxieties are compounded by the changed media universe he finds himself in on the verge of his comeback: At one point in the film, he’s harangued by his daughter, played by Emma Stone, for pooh-poohing technology as artistically and morally bankrupt, thereby consigning himself to the margins not just of show business but common life. “There is an entire world out there where people fight to be relevant every single day, and you act like it doesn’t exist,” she inveighs. “Things are happening in a place that you ignore — a place that, by the way, has already forgotten about you. . . . You hate bloggers, you mock Twitter, you don’t even have a Facebook page! You’re the one who doesn’t exist!”

Later in the film, Thomson learns first-hand what it means to exist in the place his daughter is describing, a vast cyber-arena that voraciously eats up and spits out images at one polar extreme, while equally hungry social media regurgitate that visual raw material at warp speed, this time with snark that seems to gain exponentially in vitriol and velocity with each successive click.

“Birdman” is but the latest — and certainly funniest and most graceful — iteration of a common movie theme of tech-driven anxiety this fall: Jason Reitman’s domestic drama “Men, Women & Children” recently tapped into parental issues with teens, predation, precocious sexuality and privacy. Noah Baumbach’s comedy of manners, “While We're Young,” due out next year, addresses themes of middle-aged obsolescence and the yearning to stay young with rueful familiarity. And just wait until you see Jake Gyllenhaal channel a bottom-feeding amateur cameraman who makes his living filming the aftermath of violent crimes for a local Los Angeles TV news station desperate to compete with the Web’s endless parade of disaster porn.

Those movies, combined with the Zellweger tweeting frenzy — and recently hacked photographs of Jennifer Lawrence and other actresses — reinforce the scary idea of the Web as a pitiless and ungovernable frontier where every screen grab, selfie or random iPhone shot is potential fodder for hackers, trolls and mean-spirited­ armchair pundits. But seen through another lens, the new morphology of ritual celebrity mortification — the intentional or unintentional release of an image, the ensuing cruelty and aggression, the “benign” backlash of pseudo-sympathy for the subject­, the inevitable hand-wringing­ of cultural commentators such as yours truly — may not be a modern-day Wild West as much as a seismic realignment of Hollywood’s traditional means of production.

At the height of the studio system in the 1930s, stars’ faces and bodies were literally the property of their employers, who molded and shaped them into the public personae their fans worshipped and adored, an industrial practice portrayed with heightened melodramatic flair in the 1937 movie “A Star Is Born.” In that cautionary tale of aging, ambition and the siren lure of fame, Janet Gaynor’s character, an aspiring actress named Esther Blodgett, undergoes a thoroughgoing makeover, the studio changing her name to the far more musical Vicki Lester and putting her through a series of sessions with a makeup artist, who draws her face to resemble famous Golden Age actresses from Greta Garbo to Joan Crawford.

The star as commodity — to be molded and, ultimately, discarded — possesses both aspirational and tragic undertones in “A Star Is Born.” But it acknowledges an essential truth of the art of movie acting, which is that, in addition to delivering a convincing, emotionally affecting performance, part of an actor’s or actress’s job is to be a screen object — that ineffable coalescence of face, body and personal attributes that, whether they attract or fascinate us, seduce or repel, make them always compulsively watchable. As creations hovering somewhere between the real and the mythical, stars are no longer the property of studios but instead belong to all of us. And as technologically empowered mini-moguls, we take vocal and proprietary interest in how they expand, contract, morph and otherwise transform over time.

How to make note of those changes — which genuinely inform and affect the viewing experience — without resorting to the neurotic cycle of blame and shame? As a visual medium, cinema is inherently objectifying, but appraising an actor’s physical appearance is never easy. Nor should it be: Most critics know, or come to realize eventually, that fat jokes, cracks about nose jobs or sniping about a physical condition beyond an actor’s control are rookie mistakes, easy pickings that may earn a laugh from a reader but do nothing to elevate the conversation or advance the art form.

Far more elegant, precise and useful — not to mention kind — is to write about physical appearance not in terms of fat or thin, pretty or ugly, but in expressiveness, grace, characterization and movement. An expansive, more compassionate lexicon helps (I’ve always loved the phrase “generously built” rather than more pejorative terms). So does celebrating filmmakers and performers who dare to challenge the most tyrannical expectations of the industry and the mass audience.

The most recent case in point happens to come from Linklater, who gave Zellweger, McConaughey and an entire generation of now-middle-aged actors their start in 1993. With his “Before” trilogy, starring Ethan Hawke and Julie Delpy, and this past summer with “Boyhood,” starring Hawke and Patricia Arquette, he has allowed his actors to grow older without apology. Filmed over the course of 12 years, “Boyhood” invites the audience to watch, astonished, as Hawke and Arquette enter their mid-40s with all the recognizable ebbs and flows of the flesh, along with verve, vulnerability and hard-won wisdom.

The film, one of this summer’s sleeper hits and an early awards favorite, succeeded on many levels: For one thing, it exemplified a new, spellbinding cinematic language, and viewers no doubt recognized their own fractured yet seamless relationship to time and change in an epic yet intimate coming-of-age story. Most radically, though, Linklater's film has opened up a whole new way for actors to channel the audience’s dreams, desires and deepest aspirations: That’s what to love most about “Boyhood’s” stars, man. We get older, and they do, too.