Via Cinemablend.com:

George Lucas admitted that he never actually believed he’d be able to make the Star Wars prequels because he didn’t think that the technology to create the films he wanted would ever exist. However, Lucas was finally convinced that such sensational special effects had finally caught up with his vision thanks to the good people over at ILM.

George Lucas made this admission while talking to Wired for an in-depth and extensive piece on Industrial Light & Magic. Lucas explained:
I never thought I’d do the Star Wars prequels, because there was no real way I could get Yoda to fight. There was no way I could go over Coruscant, this giant city-planet. But once you had digital, there was no end to what you could do.

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