Ewan McGregor has revealed that Star Wars Episode II: Attack of the Clones needed every single line of dialogue re-recorded, due to a filming setup that "hummed".
The Star Wars prequels have been much maligned by long-term fans of the franchise (particularly Episode II, widely derided as the worst in the series), but they were instrumental in the development of digital cameras being used in Hollywood.
In fact, Attack of the Clones was the first ever science fiction film, and the third film ever, shot entirely on digital cameras (the Sony CineAlta F900, which was intended to film the 1999 Star Wars Episode I: The Phantom Menace in its entirety, but Sony could not produce enough cameras in time).
However, an unforeseen side effect in filming meant that the on-set audio for the film was rendered completely unusable.
"He was also pioneering digital cameras, which we used on the second episode and the third episode," McGregor told British GQ. "It took too long to change a lens, so they just had a zoom lens on them, and we had two of them. They had huge umbilical cords coming out the back to this tent in the corner of the set that hummed, literally hummed.
"And they discovered after we'd finished shooting that they hummed in the frequency of the human voice, so we had to redo every single line of the second film is ADR [automated dialog recording, where actors have to lip-sync their lines in post production]."
Watch video: Ewan McGregor talks Star Wars
Given all the extra work, and the pioneering effort to transform cinema in general, it was extra painful to the cast and crew for the prequel films to then be received so poorly by Star Wars fans.
"The fighting took months to learn, we did the best we could to make it the best it could be, and I think we did. To then have them released and for the noise coming back to be like, [deflated groan], was really hard.
"But now, I meet the generation we made them for. You know, I meet the young people who were kids then, who for them, our Star Wars films were their Star Wars films. And the Seventies films are, they don't have the same relationship with them.
"And it's really nice for me, that's really part of the reason I decided to do the TV series [Obi-Wan Kenobi], because I was aware of that. I mean, really there's a genuine appreciation of those films and it's funny to feel it, like, 15, 20 years later. But it's nice to feel it 15, 20 years later."
You can watch the entire Star Wars saga, including the new Obi-Wan Kenobi series, on Disney+.
Correction: The original version of this story, published on 02 August, inferred that the humming was caused by the lenses being used. We have since clarified that the humming was actually generated by the equipment inside the tent, not by the cameras or lenses.