For months, Jeff Scher combed through archival photographs and historical films of the Holocaust, shot by shot and frame by frame, to give life to the story of one of its survivors.

It was crucial research for the Westport animator and illustrator, whose live animation work fills the screen for about 10 minutes in a new documentary for HBO, executive produced by, Sheila Nevins, “The Number on Great-Grandpa’s Arm.” It’s not a long film, about 19 minutes, but it’s a powerful one. It teams 90-year-old Holocaust survivor Jack Feldman with his 10-year-old great-grandson Elliott, who asks about the tattoo on Feldman’s arm — A17606 — from his imprisonment in a Nazi concentration camp during World War II.

“That was his number,” Elliott says early in the film. “He told us, back then, your number was your name. That was all he was to them.”

Elliott’s questions for his great-grandfather about life before and after the Nazis took power, and the effect that had on a young Jack in his hometown of Sosnowiec, Poland, unearths happy memories of growing up in a close-knit family, as well as those of sorrow and loss as he is shipped off to the ghettos and ultimately, the Auschwitz-Birkenau death camp. After its prisoners were liberated in 1945, Feldman came to the United States.

As the filmmakers edited the narrative, it created the template for images needed to illustrate it, Scher says. “It all grew out of (Jack’s) story, which was similar to the stories of other people, too.”

Emmy award-winning director Amy Schatz brought Scher into the project, having worked with him on other HBO films, including “Goodnight Moon and Other Sleepytime Tales,” and “’Twas the Night.” (Scher’s wife, graphic designer Bonnie Siegler, also worked on the documentary.) The creative team wanted to use archival content to visualize Feldman’s story, but they had to think about who would watch the movie.

“The footage and photos are so heart-wrenching — we didn’t want to overlook that,” Schatz says in an email. “But we also wanted to be mindful of a young audience. …. Jeff was able to create hand-painted animation based on the archival footage and photographs that would stay true to the content and make it come to life in a new way.”

Scher has been creating films since his Staples High School days in the 1970s. After his 1976 graduation from Bard College, he set up shop in Brooklyn, N.Y., as an experimental filmmaker and animator. Throughout the course of his career, he has directed music videos, worked on television shows, created films, wrote for the New York Times blog “The Animated Life” and had his work accepted into the permanent collection of the Museum of Modern Art. He moved with his family to Westport about five years ago.

He has always been a “painter of sorts,” he says, having grown up in an artistic home, but was frustrated that his paintings didn’t move. With his use of the rotoscope technique, tracing film footage frame by frame to give a realistic look to the animation, he gets past that frustration. It’s what he used for “The Number on Great-Grandpa’s Arm.” Using the chosen stills and documentary footage as a guide, he hand-painted each frame, creating 12 drawings for each second of animation. The technique, in effect, transforms real-life movements into mirror-image animated ones. By the end of the project, he had a stack of about 4,000 watercolor paintings.

“Before the Nazis, when (Feldman) reminisces about his childhood, the images are full of color — blues, greens, pinks, all the colors of life,” he says. “When the Nazis come in, I drop out all of the colors one at a time.”

Scher only dips his brush into two bright colors once the Nazis invade, the bright red of the swastika flag and the yellow star of David that Jewish people were forced to wear. Historical photographs and documentary footage are used, but the animation, told in storytelling fashion, creates a linear line for Feldman’s story and millions of others.

“With the narrative, you have a character to identify with,” Scher says. “That one person could be you.”

Such an empathetic viewing is going to become increasingly more important in the years to come. Those who were children in the Holocaust are in their 80s and 90s, and each day means there are less and less firsthand witnesses to the systematic persecution and murder of 6 million Jewish men, women and children and millions of others.

The film debuted last month and is available on multiple HBO platforms. It’s being presented with the New York City’s Museum of Jewish Heritage -— A Living Memorial to the Holocaust, which is hosting an installation through April 29. The show features 24 of Scher’s original watercolors and 400 digitized images drawn from 20 sequences in the film.

Scher’s scrutiny of the images left a lasting impression on him. “When you live it a frame at a time, there are things you discover in the shots,” he says, referencing footage that shows a line of people being led away from their village. “You realize these two girls are being marched down the street and they don’t have shoes or coats, and it’s winter.”

chennessy@hearstmediact.com; Twitter: @xtinahennessy