James Cameron: Despite Mistakes in Original 'Titanic,' Not One Frame Was Changed in 'Titanic 3-D'

March 27, 2012— -- James Cameron, a trailblazing oceanographic explorer, a hugely respected Titanic expert and a perfectionist movie maker, said that while he discovered a few minor mistakes in his original "Titanic," he hasn't changed one frame in his re-mastered 3-D version.

"There was a moment when I thought fleetingly I could correct the film and actually have it match what Titanic really looked like," Cameron said in an exclusive interview with "Nightline." "Another part of my mind said, no, then you're going be a nutter standing on the street corner babbling away."

Movie stars Kate Winslet, Billy Zane and others dazzled on the red carpet in London today for the world premiere of "Titanic 3-D," 15 years after the original film was released. Cameron worked with 300 computer artists, who spent 750,000 man hours giving one of his most iconic films a third dimension. It was a process he called "horrific" and "mind-numbing."

"It has to be done right," he said. "Didn't change a frame. The ship still sinks. Jack still dies."

In the years since the 1997 romantic film became a mega-hit at the box office -- "Titanic" was the first movie to gross more than $1 billion -- Cameron dipped deeper into his obsession with the "unsinkable ship." The legendary director has dived to the wreck in the North Atlantic 33 times in a submersible, studying how the real thing compares to his film creation.

"We found places that the set was wrong, little bit, you know, this was wrong, that was wrong," he said. "There was glass missing from a door."

"I thought I'd thought about everything about Titanic," Cameron told "Nightline." And then he gathered eight of the world's leading Titanic experts for an upcoming National Geographic documentary called "Titanic: The Final Word." The documentary premieres on Sunday, April 8 at 8 p.m. ET on the National Geographic Channel.

The team analyzed the locations of seemingly innocuous shards of debris from the wreck. When they ran computer models of the haul compartments filling with water, they discovered the Titanic stayed upright before sinking -- unusual because most ships, including the recent Costa Concordia disaster off the Italian coast, tip on their sides when they take on water.

"None of the people from the engineering spaces survived," Cameron said of the Titanic sinking. "They were working until the very last using pumps, moving water around in the tanks to keep that ship as level as they could so the lifeboats could launch down both sides and those lifeboats all got away. So I think there's a heroic tale that emerges from that."

"Titanic 3-D" may almost be historically accurate, but Cameron now knows it is not perfect. For example, he used a little artistic license in the scene where Winslet and DiCaprio are clinging to the ship's railing, way up in the air, as it is being dragged down into icy depths.

"There was actually probably a moment where it was standing quite proud of the water, but it wasn't quite as dramatic and as static as we showed in the film," Cameron said. "It probably wasn't straight up. It was probably at an angle. We realized that it was really just the perspective of some of the eyewitnesses."