Little did the moderator of a documentary panel that Lynne Sachs once sat on think that they were stating something controversial, but opening up the discussion by saying, “Well, let’s start by saying that all great documentaries start by finding a character,” but if they wanted a lively conversation, the experimental filmmaker was going to give them one.

“I said, ‘I totally disagree,’” laughs Sachs, still incredulous at the presumption. “You shouldn’t have to go out and search for a character in order to construct your narrative.”

Sachs could speak from experience since she never had to look far physically to make “Film About a Father Who,” but in telling the story of Ira Sachs Sr., she could never be quite sure that she actually found him, even when he’s introduced sitting in her apartment getting his long, flowing grey mane unknotted in the opening frames of her latest film. While it is no wonder that Sachs Sr., a great raconteur, gave birth to a number of storytellers including “Frankie” director Ira Sachs and “The Secret of the Nightingale Palace” author Dana Sachs, he can be seen as a mystery throughout Lynne’s fragmentary biography, compiled over 30 years, as he would come to have nine children with six different partners.

Although Sachs Sr. could afford to keep all in good shape financially, building a successful business as a developer in Park City, Utah, time was naturally far more difficult to be spread around to his various family members living in different parts of the country and Sachs creates a narrative as alternately slippery and memorable as her central character, giving brief glimpses of her own life with her father as well as her siblings and half-siblings and letting questions of his responsibility towards them linger in the air for the entirety of the picture and beyond. As a story that spans generations, “Film About a Father Who” is also conscious of how one era of a family can messily overlap with another, as Sachs probes her grandmother’s hold on her father after leaving her family to maintain her sense of independence and sees how he’s left others behind to preserve his, and the director’s aesthetic adventurousness truly captures such intangible qualities as influence and support, or lack thereof, in ways that can be deeply felt with voiceover that’s occasionally whispered and images that are superimposed over one another at times.

Remarkably, “Film About a Father Who” will be premiering later this week where it all began in Park City as the opening night selection of the Slamdance Film Festival en route to a New York bow at MoMA’s Doc Fortnight in February. Shortly before, Sachs spoke of the project that’s consumed the better part of her life in any number of ways, working with the technology that’s been available to her over the years to create such a tactile mosaic and turning what she couldn’t bring herself to say into the language of the film.

I know you spent decades collecting footage of this. Were you always conscious of the form you wanted it to take?

Actually, the very first images that I shot in it were the first year I even felt I was a filmmaker. That was in 1984. I was just right out of college. But I made a couple of short films and then I made my first longer form documentary and then in 1991, I said to myself, “I want to make a film about my dad.” And I thought it would take me a year or two. [laughs] I made it with the interest in what extent you could ever understand another human being, so I thought at the time I would make this triptych – I would make a film about a total stranger, and then I’d make a film about a very distant cousin of mine who had been a survivor of the Holocaust and ended up in the remotest Brazil. Those two films were very challenging, but not as hard as making a film about my dad.

I was describing this film to a woman and she said, “Oh you just got together a bunch of home movies, right?” But almost every shot of this movie, I shot with the intention of being in this movie, so I always thought it had a direction to it, not just going into my closet. Also, my brother Ira, who’s a filmmaker, shot some of the footage because there were times when my dad was maybe more comfortable in this kind of guy-guy thing, which is funny, but he may not have revealed as much with me. And then there’s actually quite a bit of the footage that he just shot himself and I would actually call [those] home movies when you have the perspective from him.

How much did you want his presence to be in the film when he’s somewhat of an elusive character?

It was a constant effort and he was a cooperative subject, more so than most people would be, so he didn’t mind my traipsing around with whatever girlfriend he happened to be with. He was quite happy about [filming] in a sense because it gave us a purpose, so he would say, “Are we shooting my movie?” Or he would say, laughing, “We’re losing light” or “It’s magic hour,” these expressions he knew about filmmaking like it was a big production, so in that way, there was enthusiasm, but also kind of a performance side. In conventional documentaries, you sit someone down and ask them questions and then they reflect and they deliver it back, as demanded. That wasn’t the way I was able to capture most of the material from my dad.

Were there epiphanies in placing footage from, let’s say, 1986 next to something from 2012?

That is one of the most exciting parts. I spent the last couple of years shooting and my dad is getting older, so he would actually come and stay with me for two weeks, so all the footage of my dad collecting trash and walking around on the sidewalk is what he does all the time. He’s now not as capable as he was to do that even a year ago, but he loves coming to big ol’ New York City and picking up trash and feeling like he’s tidying up, so there would be points where I thought, “How could I show my father doing things that mean something to him other than [being] out for dinner or my sitting and asking him questions, so then I’d say, “Okay, dad, we’re going to go outside and I’m going to follow you.”

I was able to use this gadget that I could attach to my cell phone so I could follow him and have a really smooth shot. It’s hard to shoot with someone walking by them on the sidewalk, so modern-day consumer technology rose to the occasion. As I kept making this movie with my father, I kept carrying cameras, but I had to keep up with the technology. Film hasn’t changed very much since 16mm, so I was always shooting 16mm and it’s really funny, that was some of the easiest material to work with because the technology wasn’t just disappearing. But the very first footage I shot was on a VHS camcorder and [eventually] I shot in Hi 8 and MiniDV and that’s challenging to then digitize.

Were you conscious of how this would come together aesthetically throughout? Some of the most interesting footage in the film was when you were talking to Diana and Mallory, two of the exes…

Yeah, it’s funny you bring that up because that was shot in 16mm and it looks kind of beautiful, doesn’t it? The camera is kind of my brush, so I’m always aware, but there’s a shot of Mallory, and the first time I shot it, she came out in silhouettes and with the new technology, you can bring out detail, so that’s actually been a really positive thing because I never bring in additional lights. [That shot] uses natural light, which I just think is so much more beautiful. I always like to use what’s available and I like profiles – I actually don’t think people shoot profiles enough. And my husband Mark Street, who’s a filmmaker too, did the sound recording on that with Nagra, the quarter-inch tapes [like you see] in “The Conversation” and all the famous movies where they show people recording sound, so it’s running through a little quarter-inch machine reel to reel and the sound quality was pretty good because it’s right onto the decent audio material and then luckily I took good care of the original 16mm negatives.

One of the strongest through lines of the film becomes the relationship between your father and his mother. Was that evident from the start?

It was always a big part and something that we always wondered [about]. My dad had a pretty difficult childhood being shuffled back and forth between divorced parents, and I don’t mean to be psychoanalytic, but people do things their whole life to apologize for what happened when they were children to reckon with it or to find a sense of closure, and we always wondered if she was trying to make amends. They were tough amends, but I tried to suggest that there was a layering to those relationships [that extended into the present] and my grandmother died at 103, so [it was unusual when] most adult men in their seventies don’t have a chance to still deal with their mothers. [laughs]

I imagine there was always the sense you could film more. Did you know there was the right time to wrap this up?

This was the kind of movie where certain people who knew me well from family members to really good friends who had seen all my movies, they’d say, “Lynne, okay, when are you going to finish the ‘Dad’ film?” The most pat line that I had — but it doesn’t work anymore — was that it’s the hardest thing I’ve ever done and [when] anything gets in my way, absolutely anything, I would keep shooting.

But I don’t know how you feel about all the photographs you take or videos you shoot in your life, but I don’t actually necessarily like going back and looking at them. You get sad because you miss the children who are now adults or you miss even more than the people who died, who people were, so all that kind of nostalgia or pathos, I didn’t know how I would deal with it. Once I set my mind to finishing it, one of the amazing things is when I went back, it wasn’t the images, but the sound, that was even more enthralling and I tried to bring that into the soundtrack of the film [because] usually sound is what you gather accidentally — casual conversations that were happening while you were shooting.

So that was the gift when I went through the material and that’s what actually the last few months [of editing consisted of] — I’d go and I’d look at material that I totally dismissed because the images I thought were so bad, and actually one of the things that kept me from making the movie is looking at the footage and being extremely judgmental of my own photography and then I came to this conclusion, which was I was sick of beautiful images. We can see beautiful images any time we want on television or in the movie theaters and the digital image is so available and so pristine that our measure of success with the digital image is often how does it mirror reality, but with the older cameras and the older material, it’s not nearing reality. It’s like much more impressionistic and it’s much more about the sensation of that moment in reality and I started to like that better. I thought, “Oh, I’ve got a lot of ugly images, like tarnished or degraded VHS kept in garages,” but I thought maybe the decay is interesting in a wabi-sabi way, so I decided I liked it.

How did you go about recording your voiceover? It’s wonderfully conspiratorial.

Another challenge of this film was to find my voice in it in a conceptual way – to be not just transparent, but to be expressive and not to keep censoring myself. I was at an artists’ residency in January, it’s called Yaddo in Saratoga Springs, New York and I had applied to write the narration for this film, but every time I started to write, I scratched it out. I [thought] I’m pretending to say something, but not really, so what I tried to do was get out my recorder, put on my headphones, sit in the dark or wait until nighttime and just start speaking and that was a breakthrough. I couldn’t censor myself. Because there was nobody listening, I just spoke and it’s very different because I thought 99 percent of the time when you speak, you speak for a listener, but this time I wasn’t really. Then I took those audio files, and I sent them to a transcription service and they sent it back to me within 36 hours and then I had the skeleton for working on my voiceover. I felt a lot less inhibited because then I was just tinkering with it, not trying to write it, so it’s like I wrote with my mouth. Ultimately, I did rerecordings [for what you hear in the film], but at least I felt they had more of an authenticity than just pen to paper.

Given your father’s history, it’s wild this will be premiering in Park City. What’s it like bringing this into the world?

Well, I’m nervous. My dad won’t be there because he spends winters in a warmer place, in Florida, but he’s going to come to one of the screenings in New York [later in the spring]. He’s seen the film twice already and he cried, which was the first time I’d ever seen that before, [and while] I’m nervous about Park City, but I also feel like there is an appreciation. My dad lived in this Bohemian way, so some people might say, “Well, I didn’t realize he had nine kids [by] six moms, but we all are actually close as a family, all nine of us, with him. We spend almost every holiday together, so he created this ramshackle family, [but] one of the things I realized [making this] is this whole idea of nuclear family these days, and maybe also going back decades, has more to do with how you feel a connection to other people. Like some of [my family], two of the sisters, I haven’t had a whole lifetime to get to know, but I’m getting to know now and it’s interesting. There’s so many families now that are finding each other through DNA. Ours is just a little different.

“Film About a Father Who” will screen at Slamdance on January 24th at 7 pm and 9 pm and January 27th at 11 am. It will next screen at Museum of Modern Art’s Doc Fortnight in New York on February 11th at 8 pm and February 14th at 4:30 pm.