Film audiences know when they watch Harry Potter or Gandalf in Lord of the Rings that the real wizardry is in the special effects, but what they might not realize is that digital technology can also be used in very subtle ways, such as changing an actor's expressions.
"What you're seeing is a natural progression from something that's all fireworks and whiz-bang to something that's very, very below the line," said Rob Duncan of Framestore CFC, a visual effects company.
In the film A.I., the robot child played by Haley Joel Osment is not supposed to blink or squint when under water. But actors are only human, which is where the digital-effects people come in — touching up the eye region with computers. And robots don't breathe, either.
"Whenever that little air bubble pops out, I replace it with the new, clean nostril," said Chad Taylor of Industrial Light and Magic, another special effects firm.
More and more, films use what they call invisible effects — and not just on actor's faces. If a director doesn't like the color of the sky, he can alter it. Or if there's something else in the shot that isn't quite right, digital effects can fix it.
The Perfect Storm had some spectacular effects, but there was some subtle stuff in there as well. Industrial Light and Magic tweaked a little boy's tears in the film.
In the original take, the child, who was crying as his father was about to head out to sea, cried a few too many tears for the director's liking. ILM was asked to take the tears out. But without tears the crying did not look genuine, so the director asked ILM to re-instate just a single tear.
"It was decided that just a little bit of tears would be preferable, and that's what you see in the final version," said Eric Brevig, ILM's visual effects supervisor.
A particular French town had the perfect look for the film Chocolat, but the wrong climate. It was too warm for the chilly opening panoramic aerial scene, so they used the computer.
"We added snow on the horizon line there, snowed up roofs, snow on the streets," said Anthony Hunt, visual effects supervisor for Mill Film.
The opening shot also shows a river skirting the town. There is a river near the town, but not where it was on the opening shot. Mill Film placed it there because the river would come into play later on in the film, and the director wanted the river established in the mind of the audience.
"So from the very beginning the audience is sold — small town, by a river, and it's cold," Hunt said.
This is partly about saving money. Why keep an entire crew on location waiting for a sunset shot when you can shoot at midday and have the sun go down in postproduction? Just change the sky, the color of the sand, even the shape of the shadows.
"If you get it right, you can save money," said Duncan of Filmstore CFC. "That's really what's driving more of these shots now."
So the next time a projector rolls, audiences might just ask themselves, "Did George Clooney really arch his brow, or did someone on a computer arch it for him?"