Freeze frame: artists use creative compositing as the framework for innovative effects.(Video)

Picture this: In a television commercial for Hewlett-Packard's digital photography line, actors seemingly re-arrange segments of the live action by reaching out and adding or removing a "picture" from the scene.

In the spot, titled "Picture Book," the action is momentarily frozen, mimicking a camera snapshot. Then, actors within the scene physically interact with that "photo," which is actually a frame of video that was cut, or rotoscoped, from the scene when the video was frozen. Next, the frame is composited back into the subsequent action as a photograph.

This plays out in a number of ways. For instance, one segment contains several people who, standing side by side, outline their head and face by holding up a white, hollow frame. The action pauses for less than a second, after which each actor exchanges "looks" with the person next to him or her by first handing off the initial picture frame (now with that actor's portrait inside) to someone else and then "reframing" his or her face with the white-bordered portrait the actor had just received from another. In a different scene, a woman sitting on a park bench reaches up and grabs a "picture" containing the image of a girl who's bouncing on a trampoline in the background. In yet another sequence, a person at a masquerade party "unmasks" guests by removing--and, in some instances, adding--a piece of video containing the party-goer's made-up face.

The face that's behind this creative commercial is that of Francois Vogel, an experimental film director who has extensive experience with digital compositing techniques--which are key to the video effects in the commercial. "Using those [compositing] skills, Vogel did extensive planning and testing before pitching the concept to HP's ad agency, to ensure that it could be done," says Chris Jones, creative director at Zoic Studios, which executed the effects. "As a result, we had a good idea of what he was thinking, and that's rare when you are planning visual effects."

While the effects remained constant in the various scenarios, each one required a different treatment on set and in postproduction, specifically with respect to tracking and compositing. In fact, some segments implement a still video image, while others use several seconds of a video clip.

For instance, in the change-of-identity scene, people are handling what appear to be prints with white borders. But in reality, they are passing around white foam-core frames so that each person would have a physical object to interact with. Later, in postproduction, the artists used Discreet's Combustion to track the physical white frame. Also using Combustion, they rotoscoped a single frame of video from the live action, and with Discreet's Flame, composited that still image inside each white frame.

For the trampoline sequence, the girl was filmed separately against greenscreen, allowing the artists to change her positioning ...