“THIS FEELS SO cinematic,” said actress Kate Mara upon entering San Francisco’s Legion of Honor last Friday. The neoclassical museum, set on a wild bluff, overlooked the Pacific Ocean and the setting sun, as a small battalion of tuxedoed men flanked the promenade.

The occasion was the Fine Arts Museums’ 12th annual benefit, hosted this year by Dior. It’s officially called the Mid-Winter Gala but has been nicknamed “The Prom” as it serves as a fine excuse for the city’s social set to dress up and stay out late. Appropriately, the fashion was as dramatic as the setting. Honorary co-chair Vanessa Getty debuted a sweeping black-and-white Dior gown she picked up in the fall. Meanwhile, Alexis Swanson Traina wore a dot-and-floral motif Oscar de la Renta dress topped with a lace shrug. “I’ve been saving it for the right moment,” she said.

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Along with local celebrities like director Roman Coppola and Yelp CEO Jeremy Stoppelman, a small crowd of famous (and beautiful) faces flew in for the evening, including Ms. Mara and Kate Bosworth—both in Dior Haute Couture—and model-slash-D.J. Alexandra Richards, who later took her post at the turntables beneath a rear view of Rodin’s “The Thinker” in the tented courtyard.

With a San Francisco flagship opening in the fall, Dior president Pamela Baxter was reassured by this unofficial Bay Area focus group: “I have to say that I’m impressed and I’ve seen some truly chic guests in Dior, so I think we’re good.”

As reputations go, black lace tends to land on the naughty end of the spectrum. But in today’s anything-goes world (we’re talking about you, Internet Breakers), that place is somewhat unfairly earned. In fact, black lace can provide a perfect way to cover up with a slyly elegant wink. That’s handily proven by the three ladies here—Michelle Monaghan in a siren-like Elie Saab gown, Jennifer Connelly in a trumpet-hemmed Louis Vuitton dress and young British model and actress Sai Bennett in a sweetly bohemian bell-sleeved frock by Danish label Ganni.

No longer just for louche lounge singers, the white dinner jacket has re-emerged as a more viable formal evening option, providing a still-classic alternative to the all-black tuxedo. Fittingly, the dazzling and dapper look has been adopted by some of Hollywood’s brightest leading men—Adrien Brody in a Dolce & Gabbana rig with a distinct, contrast black lapel, Jon Hamm living up to Don Draper’s debonair image in a peak-lapel Giorgio Armani jacket and Jeff Goldblum looking sleek in a shawl-collared Tom Ford tuxedo.

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