Sandy Powell wasn’t just the costume designer for director Todd Haynes’ “Wonderstruck.” She actually helped get the project off the ground. “The whole film started with me introducing the script to Todd,” Powell tells Variety.

The screenplay was written by her friend Brian Selznick and based on his illustrated book of the same name. Powell got to know the writer when she was working with Martin Scorsese on “Hugo,” an adaptation of Selznick’s book “The Invention of Hugo Cabret,” though he didn’t write the script for that film.

Powell was convinced that Haynes was the director who could best tell the visually imaginative story of “Wonderstruck,” about two deaf children from different eras — Rose (Millicent Simmonds) in the 1920s and Ben (Oakes Fegley) in the 1970s — who run away to New York City in pursuit of lost connections.

The project marks Powell’s fourth collaboration with Haynes; she was costume designer for “Carol,” “Far From Heaven” and “Velvet Goldmine.” She is also an executive producer of “Wonderstruck.”

Some of her favorite scenes in “Wonderstruck” find the children arriving in Manhattan during their respective eras and becoming immersed in the hustle and bustle of the city. “It was a fun challenge to dress so many people and make it work for both periods, which were entirely different,” Powell says.

While Rose steps into the Financial District during a prosperous time and is surrounded by well-heeled people in proper attire, Ben’s introduction to the city is a seedy Port Authority Bus Terminal and Times Square filled with people wearing colorful, distinctive looks.

DP Edward Lachman shot the 1920s portions of “Wonderstruck” in black and white. “That’s something I’ve never done before — work in black and white — and for all the ’20s scenes it helped me,” Powell says, pointing out that she dressed numerous extras without having to worry so much about whether the colors of their outfits worked well together. “Normally, if a film was in color, I wouldn’t put a purple hat with a green coat with some orange gloves, for instance. It would look awful. But I could do that in black and white, provided it worked tonally.”

Powell needed a large quantity of diverse garments — to be worn by dozens of extras in busy scenes — which she sourced from rental companies in Los Angeles, New York and London.

The costume designer created all of the primary cast’s clothing, including the outfits worn by Julianne Moore, who plays two characters in the film: Lillian, a silent film star, and Rose in the 1970s.

Selznick paints a dowdy portrait of the elder Rose, but it’s one that Powell couldn’t bring herself to serve. “I have to say I ignored that, even though it was Brian, my friend, who wrote that description when he invented the character in the first place,” she says. “I couldn’t think of Julianne Moore like that.”

To achieve her vision, Powell outfitted the older Rose in a tunic and narrow-legged pants. “I wanted her to look artistic,” she says, “not like an old lady.”