When Jessica Chastain walked down the red carpet just before the 85th annual Academy Awards wearing a pale copper strapless gown with a mesh overlay by Giorgio Armani, her promenade was a two-part statement about the complexity of branding and the perilousness of glamour. The best actress nominee for “Zero Dark Thirty” marked herself as a woman settling into the Hollywood establishment, a sister to serious thespians such as Jodie Foster and Meryl Streep who do not indulge in trends but who strive to make a simple statement about sophistication and elegance. On the most photographed red carpet of them all, she steered clear of flashy designers, gossiped-about designers and controversial ones, too. Instead, she chose a classically glamorous gown by the godfather of red carpet style whose philosophy of celebrity dressing is: First do no harm.

For Armani, it was a significant coup. After ruling the red carpet for so many years, his dominance was starting to wane thanks to the likes of Chanel, Christian Dior, Alexander McQueen and newcomers such as Zahair Murad, who this year dressed Catherine Zeta-Jones in a tight-fitting, metallic gold column that gave her the look of a chorus girl among marque professionals. But this year, Armani nabbed Oscar’s biggest catch: the woman who recently signed on to represent the new Yves Saint Laurent fragrance, Manifesto, and who has galloped through awards season in McQueen and Dior. When faced with the night that roots high-end fashion most deeply into popular culture, she chose Armani.

The perfectly fitting dress almost disappeared against her pale skin. Her red hair hung in gentle waves. Bold red lipstick was her most prominent accessory. It all worked together to create a picture of subtle glamour — understandable, yet still aspirational.

It was the perfect branding moment in an era when an actress is no longer merely a thespian but a high-class worker bee whose every public appearance — from Starbucks to the Oscars — is in service to her bank balance and her bankability.

“The red carpet moment should be a little bit of the designer’s vision but also an actress’s vision,” says Booth Moore, fashion critic of the Los Angeles Times, who has had a close-up view of the rise of the celebrity fashion juggernaut. If the stars teetering down the red carpet on their Brian Atwood and Nicholas Kirkwood shoes put on a good fashion show for the media, “they could even get their own clothing line.”

For an actress, a solid performance during the Oscar parade — and a successful claim on the title of fashion icon — can result in the cover of any number of fashion and style magazines. It won’t matter if she has a current movie to promote. She may turn up as the co-chair of the Costume Institute gala at New York’s Metropolitan Museum of Art, with its guest list that includes political bigwigs, business titans, social powerbrokers, media moguls and its grand red-carpeted stairway thick with media. The perception of style savvy — no matter that it was born of a village of stylists, makeup artists and hair gurus — opens the doors for lucrative advertising contracts. See Charlize Theron, Natalie Portman, Scarlett Johansson, Jennifer Lopez, Julia Roberts, Chastain, et al.

Designers receive validation that they are — or remain — players in the fashion industry. But for actresses, it can forever establish who they are in the public consciousness: serious actress, sweet ingénue, sexpot, ballsy rebel. And for a young actress like Quvenzhane Wallis, her choice was reassurance that she is a down-to-earth nine-year-old, a sweet child and not a Hollywood monster headed to rehab. For the occasion she wore Armani Junior — another coup! — in navy tulle with a back bow and carried her signature accessory: a puppy purse. She was accompanied by her mother and older sister.

The rote question called out from the media gauntlet on Oscar night remains “Who are you wearing?” But the more salient one is really, “What does the clothing say about your personal brand?”

Is there any doubt that what Helen Hunt — best supporting actress nominee for “The Sessions” — was saying with her simple navy strapless gown, which she volunteered was made by H&M even before E! Entertainment host Ryan Seacrest thought to ask? She is serious. She stands apart from this out-of-touch Hollywood glitz. She is as willing to take a fashion risk and be judged brutally for it as she was willing to get stark naked on film without benefit of candlelight and traditional romance.

Zeta-Jones’s look-at-me Murad gown suggested insecurity. Kerry Washington’s rock-crystal-embellished Miu Miu dress reflected an actress who is in the thick of claiming her stardom — at least it did once she stopped tugging on it. Jennifer Lawrence’s elegant Dior couture ball gown with its fitted bodice and tiered skirt spoke of her formal relationship with the house’s advertising campaigns, as did Theron’s white, sculptural Dior gown. Their choices — were they really even choices? — spoke of being tethered to a company. And Anne Hathaway’s pale Prada halter dress with its pointy bosom was a statement of independence and control, particularly since an alert had already gone around the Twitter-verse that she would be wearing Valentino.

There was a time when the Oscars were a runway show ruled by the fashion industry. In the midst of delightfully ridiculous red-carpet displays of feathered headdresses, bicycle shorts and sequined mermaid gowns, Armani dispatched his personal representative, Wanda McDaniel — a former journalist and a Hollywood insider — to put a stop to such egregious bad taste. Armani opened his Rodeo Drive boutique in 1988, and the following year he led the fashion industry in a takeover of the Oscars red carpet. He styled actress Michelle Pfeiffer in a navy silk cocktail suit. It was understated and chic and practically austere when measured alongside the one-armed, self-designed gown worn by Kim Basinger. In the next days parsing of the awards, the fashion trade publication Women’s Wear Daily prominently featured the two actresses under the single headline, “The Agony and the Ecstasy.” The fashion industry recognized the advertising potential and leapt into the pursuit of celebrity hangers.

The result was an amped-up campaign to woo, cajole and buy Oscar nominees, presenters and anyone else who might swan down the red carpet in front of the hordes of photographers. And for a time, the payoff, while not necessarily measurable in dollars and cents, was obvious in terms of publicity. Prada entered the popular lexicon thanks to a lilac gown worn by Uma Thurman. Dior got a major jolt when Nicole Kidman wore its chartreuse sheath trimmed in fur. Elie Saab became a footnote in the history books when Halle Berry wore his gown the night of her Oscar win for best actress — the first African American woman so honored. Berry chose Versace for this year’s awards — a striped, black and silver, glittery Bond-girl style gown managed to be va-va-voom yet conservative.

But now, the red carpet is no longer a place for a design house to highlight its most saturated vision. It not only is a partnership between the designer and the actress, it’s also a kind of compromise between Hollywood and Seventh Avenue. Fashion and glamour are two different concepts, and the red carpet is a place where an intellectual or wry approach to style wins no fans. Fashion is about the shock of the new; glamour is defined by desire and mystery.

In 2007, Jennifer Hudson was guided through the thicket of award-show dressing by fashion expert Andre Leon Talley and Vogue. She wore a brown Grecian style gown by Oscar de la Renta topped with a gold peak-collared bolero. The gown was classically elegant. The bolero was Space Age. The combination did not go over well with the mass-market tabloids or middle America. But Talley remains stalwart in his belief that fashion should not succumb to the pressures of couch potato critics.

“No, I never tone down or dumb down the fashion for the red carpet,” says Talley. “Jennifer loved the dress and gold reptile bolero.

“Look, this season, at the SAG awards, Julianne Moore wore a splendid Chanel couture dress and some tabloid shows said she was the worst dressed,” Talley continued. “The best thing is never compromise on one’s conviction.”

Still, after all the work that goes into primping for the Oscars, it must surely sting — at least a little — to have one’s choices declared a fashion faux pas. Actresses aim to mollify the rarefied fashion world, to make the most of this night under the spotlight. But ultimately, the red carpet is for middle America, People magazine and history. This year, Hudson selected a glitzy — but safe — navy Roberto Cavalli gown with a scalelike pattern. And Amy Adams chose a seafoam blue Oscar de la Renta gown with an enormous ruffled skirt that almost enveloped her in 1950s-style frippery.

Negotiating the line between fashion and glamour explains the affection for vintage dresses. Fashion insiders who can declare an actress a style-setter love vintage because it speaks of creativity and individuality. Yet vintage fashion adheres to the traditions of beauty and sex appeal that the general public knows and loves.

“The Oscars are a fashion moment, but they are not an ‘editorial moment’ like the Costume Institute Gala,” says Cameron Silver, founder of Decades, the highly regarded vintage clothing boutique in Los Angeles. “This is populist entertainment, so I often suggest [going] the iconic route; hence the security of wearing something vintage.”

“More or less, there are two vintage silhouettes that we see decade after decade at the Oscars: a strapless Mainbocher or a Dior ball gown,” Silver notes. “Naturally, wearing the original inspiration is always particularly desirable.”

And it’s always a treat when a little girl stays true to herself and her affection for a puppy purse.