For journalists, being romantically involved with your subject treads a tricky ethical line. In documentary filmmaking, it can lead to a generously personal and intimate perspective on your subject.

Filmmaker and photographer Douglas Keeve was dating then-rising fashion designer Isaac Mizrahi when he made his 1995 documentary “Unzipped,” back in theaters this weekend in 4K from Janus Films. This vérité portrait of a charmingly frenetic mind follows Mizrahi as he mounts his 1994, “Nanook of the North”-inspired collection during Paris Fashion Week. At the time, Chanel owned a majority financial stake in the Isaac Mizrahi fashion house that crafted sensibly chic haute couture — and a decade before Mizrahi became best known not only for his outré personality and “Eraserhead”-like shock of hair, but eventually his ready-to-wear diffusion line in Target stores.

Restored by the Sundance Institute and UCLA Film & Television Archive, “Unzipped” is a transportive chronicle of the early-1990s New York fashion world in miniature. Runway models featured in the film (and in a colorful range of moods and on-camera savviness) include Naomi Campbell, Christy Turlington, Linda Evangelista, Cindy Crawford, and Kate Moss. Younger folks laser-beamed into ’90s New York nostalgia by “Love Story: John F. Kennedy & Carolyn Bessette” and its panoply of Parliament cigarettes and Calvin Klein denim will find much to love about Keeve’s partly in-color but mostly black-and-white doc.

And, yes, he was dating Mizrahi at the time. Their relationship curdled soon after “Unzipped” premiered at the 1995 Sundance Film Festival, where it won an audience award, but the documentary isn’t the thing that broke them in half, exactly.

“Did the movie break us up? I’m not sure I know how to answer that because relationships are so complicated,” Keeve told IndieWire. “Isaac is complicated, I’m complicated. So you have two complicateds, plus a complicated world. Our lives were so different, and in some ways I couldn’t quite keep up with his. Isaac goes to two cocktails at dinner and an after-hours party in one night, every night. And I just couldn’t do that. I had my own working life, and it was busy. He wanted a partner who could share those things, which I think is correct. There was so much external pressure from different things.”

He continued, “The movie came in, and the movie had nothing to do with our breakup at all. There was pressure around finishing the movie because we had a deadline, but I was so in love with Isaac and in love with just who he is. The movie is — I hate to say it because when you make a movie like that, it just becomes utter rubbish — but it is a love letter to him, I think, because he’s just so extraordinary.”

“Unzipped” is not always a flattering portrait. Mizrahi can be a burst of benign volatility, but it’s not anger. It’s a certainty in what he wants. In one scene, he gets deeply flummoxed over a rival house’s “eskimo”-inspired fashion line that’s just a tad similar to his own. Meanwhile, he’s also just modeled his show’s hair and makeup after Loretta Young in 1935’s “The Call of the Wild.” She’s supposed to be frozen and near death, but instead she’s all glammed up, ready to be rescued by a handsome savior.

“We’ve always been frenemies, and I still love Isaac. He’s amazing,” Keeve said, who’s promoting the documentary re-release, whose restoration he supervised, alongside his ex.

“I wouldn’t show Isaac the movie when we were editing it at all, and only when I was happy with it, I brought it to him,” Keeve said. “There may be those moments in the movie that may seem like I’m shooting him in the bathtub and exploiting him, but I just always had a camera, and Isaac is somewhat oblivious to the camera in a way. He just is one of those people who is in the zone all the time. … What’s more shocking is that I could walk into the bathroom and film him, and he’s on the phone with his mother, and he doesn’t really notice me. And I would’ve been screaming at him like, ‘Get the hell out of here.’”

And yes, Mizrahi’s very Jewish mother Sarah is a main character in “Unzipped,” affably looming and wanting to impose her input on her son’s vision.

“They had that typical Jewish mother relationship, which is incredibly close, probably mama’s-boy close, and yet incredibly fraught, as I guess stereotypical Jewish mothers are. The thing that Fran Leibowitz says is that stereotypes tend to be true. So she said it, not me, but she was a wonderful woman, and I liked her very much,” Keeve said.

The models in the film, meanwhile, run the spectrum from docile to diva — including Evangelista, who’s entreating the camera with an impish smile even while having a little fit backstage.

“There are a lot of people who say that Linda is the greatest fashion model who ever lived, and it’s arguable, but Linda in the show, where she’s having a hissy fit, and then another hissy fit, and then another hissy fit, to me, I can see that she knows exactly what to do. She’s turning it on for the camera,” Keeve said. “She’s not so much that person, but she knows we’re making a movie, and she knows that. Linda said, ‘I have to bring it,’ so she did. … She just turns to the camera, and she gives this look like she’s just staring at the camera like, ‘I dare you to judge me or whatever,’ and then she turns away. For me, that’s an incredible moment.”

Keeve added about supervising the restoration, “When I’m watching the movie, I’m not really looking at the technical part of the film about how the diamond has been polished even more. I’m really seeing those moments and feeling those feelings.”

“Unzipped” is now playing at Film Forum in New York with an expansion to follow, including Los Angeles on October 9.