Patricia Field likes looking back on a lifetime in fashion as a series of snapshots. In the late 1970s the rocker Patti Smith visited Ms. Field’s shop on Eighth Street in Manhattan, a downtown mecca for club kids and outliers of varying stripes. “Her hair was disheveled, and her clothes were all wrinkled,” Ms. Field recalled, “but she had on a full-length olive green mink, looking like royalty who’d fallen on hard times”

A couple of decades later, as costume designer for “Sex and the City,” she was rifling through a discount bin in a Seventh Avenue showroom searching for just the right item for Sarah Jessica Parker to wear in the show’s opening title sequence.

Soon enough, she unearthed a length of tulle that “peeked out like a frothy wave ” Ms. Field said. “I pulled and out came this sort of chic white tutu.”

Among her varied gifts is a near eidetic recall. “What impresses me stays with me,” she said on a recent afternoon. It also animates her latest venture.

Artist, stylist and merchant turned costume designer, Ms. Field, 81, is about to add author to her catalog of credits. Her new memoir, “Pat in the City: My Life of Fashion, Style, and Breaking All the Rules,” written with Rebecca Paley and out on Feb. 14, charts her trajectory from retail upstart and brazen participant in the underground ballroom culture (which gave birth to vogueing) to costume designer and audacious Hollywood influencer.

A keen-eyed chronicler of the downtown scene, she was one of the first New York merchants to sell underwear and neoprene togs as club wear. This was in the 1960s, ’70s and ’80s, and those outré items jostled for space alongside bedazzled merry widows, mesh tank tops, neon-colored wigs and merkins, dainty pubic wigs she showed poking from the tops of low-rise jeans.

The shop, which opened in 1971, famously served as a safe space for Ms. Field’s surrogate family of young artists and self-proclaimed hedonists all flying their freak flag below 14th Street. Carol Channing, Ivana Trump and Madonna were among her clients. Ms. Field had Jean-Michel Basquiat, then known by the graffiti tag SAMO, scrawl designs on paper jumpsuits. In 2002, she closed the store, seeking greener pastures.

She diverted some of her formidable energy to her work as a costume designer, with a string of greatest hits that includes “The Devil Wears Prada” and the first two seasons of “Emily in Paris.”

Much of her success, she would argue, is built on sheer audacity. She was able to sell the notion that Carrie Bradshaw, Ms. Parker’s oversharing character, would actually wear a lace-up Heidi corset and dirndl skirt to a picnic in Central Park — this over the eye rolling of her boss, Darren Star, the creator of the HBO series, which ran from 1998 to 2004.

“There were moments I panicked,” Mr. Star said. “I told her, ‘I can’t hear the dialogue because the wardrobe is so loud.’”

She did not think twice about draping Miranda Priestly, the editor in “The Devil Wears Prada,” in a succession of overripe furs and giving her an outsize crocodile bag, and she was brash enough to dress the overreaching protagonist of “Emily in Paris” in a cartoonlike homage to Gallic chic. Emily’s polarizing get-ups included an Eiffel Tower printed blouse, split-toe boots, a houndstooth beret and, perhaps most ringarde, a white eyelet Chanel crop top worn with jogging pants.

Emily’s style, a jumble of clichés, ruffled viewer sensibilities, but mostly it irked critics, among them those at Vogue, where one writer dismissed her wardrobe as a “cringe-worthy trigger.”

“I’m not making documentaries,” Ms. Field said.

The prospect of writing tested Ms. Field’s nerves. “I didn’t want to sound uppity, I didn’t want to sound pedantic,” said the designer, who in her student days majored in government and philosophy at New York University. “I wanted the book to be my voice.”

In an interview, that voice, slightly raspy, as if sifted through dry coffee grounds, betrayed no stress. She strolled into Patricia Field ARTFashion Gallery, her combined store and gallery on East Broadway, looking like an amalgam of punk royalty and slightly rough-edged Park Avenue matron. She wore a beat-up Pucci bomber jacket and purple tank showily stamped with a Balmain logo.

“It’s very anti-something that I would never expect myself to buy, very anti-me, putting somebody’s name across my chest,” she said. “But something attracted me to it.” She wore slim jeans and lime-colored loafers from Trash and Vaudeville, the fabled rock emporium on St. Marks Place. Her flame-colored hair cascaded past her shoulders.

Indeed, the only mild thing about her was the pack of yellow label American Spirit cigarettes that she placed like a talisman on table in front of her.

Her store is part of a residential complex where Ms. Field also lives. The ground-floor retail space teems with a violently colorful mash-up of hand-painted T-shirts by her friend Scooter LaForge, a painter and sculptor; sneakers embellished with what looked like cake frosting; and a poison-green breast-plated evening dress by the designer Kristina Gress. Inevitably there was a nameplate necklace, Carrie’s familiar concession to bling on the series.

“That nameplate is the rent,” Ms. Field noted dryly.

She thinks of herself as a merchant without borders, just as apt to dig up a conical bra at a fusty shop on Orchard Street, or pick up a haul of puffer jackets or Tyvek jumpsuits at a Las Vegas surplus show, as she is to score a fake fur chubby at the now defunct Century 21. At ARTFashion, she peruses her inventory with what looks like maternal affection.

“Lately we’ve been in Depression clothes, kind of loose and shapeless and faded,” she said. She has never liked the look, she said, “the people who put holes in their $75 jeans.”

That’s over, she predicted. Going forward, we will be more formal, more considered, less studiedly haphazard. “It’s not that you’ll be throwing on a dumpy dress,” she said.

Though Ms. Field may cringe to hear it, her followers revere her as a sage, a living repository of fashion history and canny purveyor of outsider style to the masses.

“Sex and the City” changed our wardrobes “forever,” Harper’s Bazaar gushed not long ago, applauding Ms. Field for encouraging the show’s fans to follow Carrie’s lead, mating a $5 dress with $500 shoes and to regard clashing prints, jungle patterns and, of course, those Manolos as not just acceptable but infinitely covetable.

That mixmaster aesthetic proved contagious, not to say prophetic. But encomiums make Ms. Field squirm. “I don’t want to be like this special thing,” she said. “I was actually a little taken aback when I became this guru, even though I handle it.”

If you take her at her word, there is little she cannot handle. She inherited her gumption from her mother, Marika, a Greek-born dynamo who channeled her entrepreneurial instincts into a thriving dry cleaning business in Queens, embracing whatever fate tossed her way. And Ms. Field similarly welcomes change, partly as a bulwark against sadness.

She was 7 when her father died of tuberculosis. “I think it was my mother who gave me the strength and confidence to let my dad go,” Ms. Field said. “She was the go-getter, always moving toward the next thing, and I took after her.”

At work she aims to balance an untrammeled enthusiasm with professional levelheadedness. She does not particularly relate to her characters, much less to her clients, she said. But she relished dressing Lily Collins as Emily, finding her committed, eager and excitable.

“She encourages me to push fashion boundaries,” Ms. Collins said. “Sometimes you just have to trust the process and not be afraid to mix and match. Sometimes more is really more.”

Ms. Parker “is a diva,” Ms. Field said with grudging respect, but she is a dream to dress. “Sarah Jessica loves fashion,” she said, adding, “she has an eye.”

On set or off, Ms. Field mostly follows her impulses, even the most contradictory, choosing romantic partners much in the way that she chooses a look, with a blithe eclecticism. Living with Barbara Dente, an influential stylist of the early ’80s, opened up new worlds. “She was a minimalist before that was even a thing,” Ms. Field writes in her book. “Her happy place was the Zoran showroom; mine was the junk show in Las Vegas.”

Life with Rebecca Weinberg, a go-go dancer turned stylist with whom Ms. Field shared a loft in the late ’80s, better chimed with her tastes. “We developed a nice groove,” Ms. Field writes of Ms. Weinberg. When, after a decade, that partnership dissolved, Ms. Field did not embark on another. She attracted younger women “who saw me as their fairy godmother.” But, she writes, “I was a human being, not the answer to all their prayers.”

“I can tell, you know, when people have a motive,” she said.

Living on her own leaves Ms. Field free to indulge stray whims or, when the mood takes her, to sit idly on her terrace watching boats pass on the river.

“Sometimes I feel a little lonely, I’m not going to deny it,” she said. “But I think I’m better off having nobody to answer to.”