George Lucas has spoken out against the idea of dead film stars being brought back to life on the big screen.
The Star Wars director says it could be made possible by advances in digital technology.
The technology is now in place for long-deceased Hollywood greats to carve out a posthumous film career.
A computer can scan in thousands of images of a particular actor, using different expressions and angles, then make a composite of their face. But Lucas says film audiences would not want to see a virtual reality version of dead stars.
"It's something we are trying to stop happening, although you can't stop technology and you can't stop change," he said.
"A computer can duplicate Tom Hanks, for example, and we already use that technology a little for stunts and difficult scenes.
"But if you bring back Marilyn Monroe, what you would have is a caricature. You could do it but you can't get a perfect actor. Acting is a human endeavour and the amount of talent and craft that goes into it is massive - and can a composite reproduce that?"
He added: "The voice would have to be dubbed and what was produced on screen would ultimately be the work of an animator.
Digital technology has already been used to enable a dead actor to appear on screen.
When veteran British actor Oliver Reed died during filming of the Roman epic Gladiator, scenes were digitally altered to make it look as if he was there.