One of the virtues of “Lady Bird” is the running time: a tight 94 minutes. Nick Houy, who was just nominated for an American Cinema Editors award for his work, says brevity was not a goal per se: “You only ask yourself, ‘Is the story working?’ You can’t worry about specific times.”

Still, movies are increasingly using two hours-plus as a standard, which is true of many Oscar contenders, so the fast pace on the A24-distributed film is an advantage.

“I’ve been an assistant editor in New York for years, working with John Gilroy, Tricia Cooke, Anne McCabe, Naomi Geraghty, some of the best,” Houy says. He also edited a few indie movies and the eight-hour Richard Price-Steven Zaillian HBO miniseries “The Night Of.”

Houy is friends with editor Jennifer Lame, whose credits include 2016’s “Manchester by Sea.” She recommended him to “Lady Bird” writer-director Greta Gerwig, who liked his work. He says, “I loved the script. I thought, ‘I have to do this movie,’ and luckily, Greta and I saw eye to eye on things.”

For Houy, the first assembly or first cut “should be something you can watch in a theater. I try to keep it under two hours and as good as a movie should be, right from the beginning.” His first cut proved a close model for the final film. “We moved some stuff around and only cut a few scenes.”

One example was the school musical that Lady Bird (Saoirse Ronan) and her friends perform in. “The segment was eight minutes, and we cut it to about eight seconds; we included only the part that tells the story we were trying to tell. I would never have thought about including the whole thing. But you could make a whole movie out of that — maybe for the DVD extras!” he smiles.

The film is set in Sacramento in 2002-2003, and one underlying goal was to make it all seem like a memory.

“For example, there is a scene in the swimming pool, when popular girl Jenna and Lady Bird are swimming, then Jenna goes underwater,” he says. “Lady Bird is by herself, in the right side of the frame. Then you cut to Lady Bird in the classroom, again on the right side of the frame, and the seat next to her is empty. You’re visually tying together these memories Lady Bird would be having. She’s imagining everyone slipping away from her.”

Houy says the emotional key to the film is in the final act. “There’s a montage of her working during the summer and getting ready for school. That sequence has a beautiful John Hartford song. I don’t want to give any spoilers, but I wanted to bring in moments, pieces of B-roll, to create an emotional memory: The idea of things tumbling forward and things you hold onto. I knew there were ways we could do it visually.”

“Greta and I kept tweaking it until it was perfect,” he says. “I’m very proud of that.”

Normally, an editor is cutting while the filmmakers are shooting. Houy came in after production was completed, replacing the original editor. “It was unusual, but it all worked out,” he says.

People don’t understand what editors do, often thinking it’s simply a matter of attaching one scene to the next. It’s a lot more complex than that, says Houy.

“It’s basically sitting 30 weeks with the director, crafting every single frame, working on the music and sound, telling the entire story, and studying each performance — every look, every breath, every moment. Others come in and give ideas, like the producers, of course. And Sam Levy, the d.p., was amazing. He would come by the cutting room all the time, and we talked about color and resizing shots. But as an editor, you’re in the trenches with the director, making it the best possible.”

And of course, there is attention to the actors. “You have to understand how actors work, how to channel emotions of the actors. We wanted 100% for all the performances, even in the small roles. Sometimes it’s about cutting a line, sometimes it’s about letting the scene breathe. Anytime you’re helping the story, you’re helping the performance.”