NYTimes:
For "The Curious Case of Benjamin Button," David Fincher, the film's director, worked with the special effects company Digital Domain to best achieve the backwards-aging process of the title character. Here Mr. Fincher and Ed Ulbrich, Digital Domain's executive vice president for production, discuss how Benjamin Button was built.
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Using a motion-capture system Digital Domain scanned Mr. Pitt’s face as he cycled through more than 120 different expressions. “What that gave us,” Mr. Ulbrich said, “was a database that lets us know everything about how Brad’s left eyebrow moves and how his right eyebrow moves and what happens to that little furrow in between the eyebrows. And what happens to your left and right nostrils separately when you open your mouth the widest," Ulbrich said. "We now had a library of pretty much everything his face is capable of doing.”

Photo: Merrick Morton/Paramount Pictures