[Plot synopsis: Brad Pitt is Benjamin, a boy born with a strange condition that makes him grow progressively younger. Cue collective sigh as Pitt recalls Detective David Mills in Se7en and J.D. in Thelma and Louise, all in one film.]
I must admit that I spent a lot of time gaping at the awesome special effects (hold on for the science bit), but in no way did this spoil my enjoyment - after Pitt put on a pair of shades and jumped on a motorbike, I barely gave the technology a second thought.
So, some rather clever sciencey types must have contributed to the camera trickery on this one. According to fx, the real life Pitt doesn’t even feature until 52 minutes in. So how did they do it? Good question.
There are some videos here that explain the whole process but essentially it involves getting your face painted green and standing under flashy lights. Well, actually it's a bit more complicated than that...
1) Cover face in make up containing phosphor.
2) Film under very fast flashing lights - on camera, the audience sees only light.
3) In the dark intervals, the camera picks up the green glow from the phosphor.
4) Use computer jiggery-pokery to capture shape of glow.
5) Use more computer jiggery-pokery to edit shape of face, making it look older/younger.
The important bit is that the powder covers the entire face. So, for comparison, to create Gollum in the Hobbit, the graphics people made a model of his head and stuck around 1,000 "control points" to it that would enable them to track its movements and recreate them on a computer. And if you think of all those "making of" programmes where people walk around in black leotards with big white bobbles stuck to them, that's the general idea. Except, using powder means you create a lot more points - 10,000 in fact - without feeling like you've just walked out of an alternative therapy procedure. So you get better resolution and, no doubt, better performances.