F. Scott Fitzgerald’s 1922 short story The Curious Case of Benjamin Button has a bizarre premise: The protagonist was born looking like an octogenarian, then appeared younger and younger as he got older and older. For David Fincher’s film adaptation, out on Christmas Day, the director had to find a way for Button (Brad Pitt) to "reverse-age" convincingly. CG was the answer: Make a 3-D model of Pitt’s visage, fast-forward it five decades, and stick it on the torso of a diminutive actor. Problem is, current-gen performance-capture techniques — sticking a bunch of dots onto the actor’s face, recording their movement, then applying the data to a 3-D model — miss subtle nuances; the resulting virtual visages often look stiff and creepy (see: The Polar Express).
So Fincher turned to Steve Perlman for help. Perlman is the founder of special effects company Reardon and inventor of a technique that would make Pitt’s metamorphosis from cantankerous geezer-child to octogenarian toddler more convincing than Tina Fey’s Sarah Palin impression.
The contraption (known as the Contour) ditches mo-cap’s standard stick-on dots in favor of glow-in-the-dark powder, which allows a combination of phosphorescent strobes and cheap digicams to capture more detailed facial data than has ever been seen on screen before. Pitt’s face was slathered with the phosphorescent dust before he emoted into an array of cameras. The footage from each camera was then melded into a single image of his dreamy mug with thousands of times more detail than the old method.
Here’s how it works: Step 1. An actor’s face or clothing is covered with glow-in-the-dark makeup. This makeup is essentially a phosphorescent powder, virtually invisible under normal lighting.
Step 2. The actor is then placed in front of the Contour — essentially a network of rapidly flashing fluorescent lights synched with dozens of both grayscale and color digital cameras.
Step 3. When the fluorescent lights are on, the shutters of the color cameras snap open. When the lights blink off, the grayscale cameras wink on and record the phosphorescent detail of anything that’s coated with makeup. This process happens so quickly (90-120 times per second) that human vision can’t perceive it. It looks as if the lights are continuously on in the studio.
Step 4. The glowing footage from each camera is then melded into a single composite image, thousands of times more detailed than conventional motion-capture methods.
5. CGI geeks take this raw data and manipulate it as they see fit. In this case, they took Pitt’s face, fast-forwarded it five decades, and then stuck it on the torso of a diminutive actor.
http://www.imdb.com/title/tt0109506/ The Crow (1994) =
description Benjamin Button isn’t the first film to have a bit of facial work done. Here are a few famous flicks that have cut-and-pasted actors’ mugs.Problem Brandon Lee expires in an on-set mishap. Solution Digitally add Lee’s face to a stunt double to complete missing scenes. Result Choppy but convincing. The Crow grosses more than $50 million. 
http://www.imdb.com/title/tt0120915/ Star Wars: The Phantom Menace =
description Problem Parts of the climactic light saber duel could be mastered only by seasoned stunt people. Solution Replace the stunt people’s faces with those of Liam Neeson and Ewan McGregor. Result The visceral two-on-one battle is one of the film’s few highlights. 
http://www.imdb.com/title/tt0172495/ Gladiator (2000) =
description Problem Actor Oliver Reed suffers a fatal heart attack before filming wraps. Solution https://www.youtube.com/watch?v=Aag7KG9Hctk Cobble together his remaining scenes with a body double and a CGI face. Result Five Oscar wins, including a nod for visual effects.
