STEP 1: Carefully Select Your Shots
When compositing faces digitally, it’s important to develop a process to cut down on time and keep the production budget on target. This begins with shooting. Often, when a face replacement is needed for a shot, it will involve a lot of action. We recently completed work on the film Lords of Dogtown, directed by Catherine Hardwicke, and were asked to replace the faces of the stunt doubles who were brought in for the tricky skateboarding scenes with those of the actors appearing in the film. It’s an essential first step to figure out what shots do, or do not, need to be worked out in post. If possible it’s also helpful to get from the camera crew an exact breakdown of the camera and lighting packages used in shooting for the shots that’ll need face replacements. The best approach is to go over the film with the director later and advise which shots can be done easily and which would require a lot of time and yield sub-standard results. If the shots involve an extraordinary amount of movement, ask for dots to be applied to the stunt double’s faces for matching later.
STEP 2: Set Up a Wide and Deep Green Screen
After you select the best shots to use, bring your actors in for a green screen session. You’ll need some room to move, especially with action shots- it’s far easier to move the camera around the actor to mimic the original shot than it is to attempt to move the actor to recreate the stunt double’s movement. When filming these shots I find that the most important thing to focus on is matching the angle of the actor’s face in relation to the camera on the original shot. Don’t worry about framing the shot correctly; you can fix that in post. Just concentrate on the angle of the face and the angle of your lighting. Again, this is why it’s important to get the lighting package down from the original shot. You can also shoot a bit bigger than the original- it’s always easy to shrink to size, but not the other way around.
STEP 3: Use Cranes, Heads or Dollies to Match the original Camera Speed In Your Green Screen Shoot
While shooting to match the movement, speed is also a factor to consider, though this is yet another thing that can be tweaked in post. We used a high techno crane with a power pad head to match the original camera speed and moves as closely as possible. We also put our actor in a swivel chair so we could turn him as needed to achieve shot similarity. It’s essential to check your shot to figure out which way the actor is looking at the camera. The best way to gauge this is by looking at the relationship of the nose or ears to the eyes. From this you can tell if the camera was above or below the actor. Whatever you do, don’t use the actor’s hair. If at all possible, use the stunt double’s hair- it will save you time and trouble during the composite.
STEP 4: Give Your Stunt Double a Nose Job Before You Composite the Actor's Face
Before you start compositing, look to see how much of the original shot can be salvaged. Can you get away with just replacing the eyes and the nose, or is the entire face needed? Can you simply replace the jaw line? Often the nose and the jaw line are the most defining characteristics of an actor’s face for the audience, and they need the most attention. Occasionally, your stunt double will have a nose or jaw that is disproportionately large, and to attempt to skew the actor’s face to cover it creates a very odd, otherworldly result. The best approach is to simply perform a double-background cleanup in Flame by hand. Give your double a nose job, and then touch up any edges with hand tracking.
STEP 5: Use Auto Tracking to Do Your Major Stitching
When attaching the faces, you can often use the auto tracking and composite nodes in Flame. You may also have to hand track as necessary. This is where your stunt double’s dots come in handy. If you’re in the unfortunate position of being "dotless," try to line up the eyes and the bottom of the jaw in your two actors. After finding the zone, position and steady the face to avoid any jittering. You might also need to use the motion blur tool to smooth over any wayward edges. When you’ve lined up your face, apply your color matching and shading tools to catch the highlights and shadows, and blend in the rotoscope area. If you really need it, the warper tool can be tapped to stretch and re-orient the face. But be warned: Doing this is a slippery slope and can distort the actor to the level that audiences will find it disorienting. Be careful!
Video Effects Supervisor
Gray Matter FX
In 1997, Gray Marshall teamed with Visual Effects executive producer Margaux Mackay and formed Gray Matter FX, a facility with a reputation not only for the high caliber of its effects work but also for the projects it selects. Since its inception, Gray Matter FX has created 2D compositing and complex 3D effects sequences for such notable films as The Life Aquatic, Pirates of the Caribbean, The Italian Job, Fight Club, Being John Malkovich, The Secret Window and many others. Gray Matter’s television credits include shots for Six Feet Under, The West Wing and Nike’s "Morning After" commercial, a Cannes Lion winner.
The company’s current projects include the upcoming All the King’s Men, Dreamgirls and The Invisible. Lords of Dogtown has just been released on DVD from Sony Pictures.
Gray Says Keep In Mind…
Often, as compositors, we get caught up in the technical aspects of what we do and forget that we’re working with professional actors. You can match a shot perfectly, pixel for pixel, but if the actor’s emotions aren’t matching the feel of the shot, all of your work and the effects of the scene will be lost. A good director, of course, will also keep an eye on this, but don’t forget to let your actors act.
Face compositing is both one of the most straightforward and most complex of all the visual effects shots. There is literally nothing that human beings are more adept at than recognizing faces, innately and by experience. And they are hard to fool. But if, after layers of compositing, you have paid attention to the subtle clues to the truth of the shot- color, positioning, timing, motion blur, tracking, sizing, angle, lighting and acting- congratulations! No one will ever know you were there. I won’t tell if you won’t.
Gray Matter FX
1503 Abbot Kinney Blvd.
Venice, CA 90291
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