Producer Brian Grazer, whose credits include such family fare as "Splash," "Apollo 13" and "A Beautiful Mind," says he was introduced to the notorious 1972 pornographic film "Deep Throat" by his 60-year-old grandmother.

"She went because it had been talked about so much by Johnny Carson and Bob Hope," Grazer says. "The references were so pervasive in our culture. She wanted to know what all the noise was about. And so she and my grandfather stood in line in West Hollywood during the daytime and saw this porn flick. It stuck in my mind."

In fact, the image of his grandmother going to the movie made such an impression on Grazer that more than 30 years later he decided to make a documentary about why she went to see it.

The result, "Inside Deep Throat,", www.xxxdeepthroat.com narrated by Dennis Hopper, spans the making of the movie (including the Mafia's involvement), the era in which it was made, the First Amendment issues it raised, the effect it had on leading man Harry Reems, and its impact on popular culture.

In addition to clips from the original film - including its most graphic - there are interviews with Reems (now a real-estate developer in Park City, Utah) and director Gerard Damiano, as well as Norman Mailer, Gore Vidal, Erica Jong and Larry Flynt.

Though the film, which opens on Friday with an NC-17 rating, is about many things, it's not about sex, at least according to the people who made it.

"I guess this film is about how our cultural zeitgeist works," says Grazer, who admits that he is uncomfortable with explicit sexual imagery on film and has steered away from it as a producer. "Pornography is very important and is about the physicalization of a philosophy, but I think that the birth of how trends happen or how barriers get broken down is more interesting."

Grazer optioned "Throat" star Linda Lovelace's autobiography, "Ordeal," 10 years ago to make into a feature film. He dropped the project when he realized her story was narrow in scope and there was no redemption to it, though Lovelace had repudiated porn. (She died from injuries incurred in a car accident in 2002.)

Years later, Grazer kicked the idea of a documentary around with HBO chairman Chris Albrecht, who pledged $1 million on the spot, which Grazer matched - with his partner Ron Howard's permission. Grazer says he was approached by a number of Oscar-winning documentary directors and producers but opted to go with Fenton Bailey and Randy Barbato ("The Eyes of Tammy Faye," "Party Monster") at the suggestion of HBO documentary head Sheila Nevins. And then he put his storytelling skills to work.

"Brian kept asking us again and again, 'What is this film about?' Bailey says. "We went mad at one point. But he was completely right. We didn't know.

"We started out making a movie about a movie made in 1972. And then as events overtook us we realized we were making a film about today. And then we realized that the story of today begins with this movie in 1972. So it was a long process. To sum it up, it's like 'The Fog of Porn'" - a joke on the title of Errol Morris's "The Fog of War."

"When we started out, someone said, 'Deep Throat' is the pet rock of porn films," Bailey says. "I thought that was really revealing. The pet rock is interesting not for itself but because of why people buy it. It tells you a lot about what people were thinking."

Barbato adds, "I think we discovered that not only was it significant in terms of what people were making at the time, but how many similarities there are between what was going on in 1972 with Nixon and Watergate and Vietnam and hard-core sex, and what's going on today with Bush and Iraq and Janet Jackson's nipple."

Barbato is referring to the Nixon administration's attempt to suppress the film, culminating in federal charges against Reems for distributing pornography. Although he didn't own or produce "Deep Throat" (the mob owned it, and he was paid $100 for six days work), Reems was found guilty, though the conviction was later overturned.

"The court case almost killed me," Reems says. "Took away my career. Bankrupted me."

It also sent him into an alcoholic tailspin that lasted more than a decade, at the end of which he found himself panhandling on Sunset Boulevard and sleeping in a Dumpster. The fact that Reems achieved his own kind of redemption gives the film's audience someone to root for. It also makes "Inside Deep Throat" more of a Brian Grazer kind of movie than it might seem.