Tilt! Using the Frame for Special Effects

The most powerful video tool at your command is the humble frame that surrounds the image. The four sides of the display monitor determine what your viewers will or won’t see and how they’ll see it. This power lets you play all kinds of tricks with images. You can make subjects float in midair or animate things that are really not moving.

The ability to defy gravity or move still objects is based on two of the universal laws that govern the video universe. Briefly, these laws are:

  •   "Up" and "down" are always parallel to the sides of the frame, no matter what they are in the real world.
  •   Movement is defined by the edges of the frame, rather than by motion in the real world.

    So, let’s see how you can put these two laws to work for you to create simple, but convincing special effects. For faking movement, you’ll need a colored compositing background (though a hard blue sky works well, too). For fooling gravity, however, you’ll need to bring along your imagination.

    What’s Up, Frame?

    In the real world, you spend your waking hours with your eyes parallel to the ground, so "up" and "down" are typically at right angles to your two eyes. Because video displays are also aligned with the ground, on-screen "up" and "down" are parallel to their sides.

    If you tilt your head, your middle ears tell you that you’re off-level, while your environment is still upright. But, if you tilt your camcorder (and frame off giveaway diagonal lines), there’s nothing to reveal the angle. Viewers will continue to believe that up and down align with the sides of the frame. You can use this effect to create steep and slippery slopes, or even to cancel gravity.

    Why would you create a slope? Mainly, to increase the difficulty of climbing it or the excitement and danger of driving, rolling or falling down it. For obvious reasons, mountain climbing sequences appear more perilous if the rock faces are closer to vertical. Cars look especially dynamic on screen when roaring up steep hills or howling down roller coaster drops. Incidentally, if you cut quickly from shot to shot, canted on-screen verticals won’t be very noticeable to viewers.

    You can also use a tilting frame to fake movement, of objects or the entire scene. To use a cornball example, imagine Mandrake the Magician commanding the coins to come to his outstretched hand. Lo and behold! They slide mysteriously across the table and into his palm. The trick:

    1. Get an establishing shot of Mandrake and the coins, emphasizing the horizontal tabletop.

    2. Frame a close angle from the actor’s point of view, with his outthrust hand stretching into the shot from the bottom, and the table edges outside the frame borders. That way, the table-tilt that causes the loot to slide is completely invisible to the audience.

    Here’s another example. Suppose you’re faking an airplane scene from behind the pilot and co-pilot, with blue sky beyond the "windshield" and the actors’ heads and shoulders concealing nonexistent instruments and controls. "There he is!" one actor yells, and the plane snaps into a steep left bank.

    In fact, it is the camcorder that does the sudden banking and to the right. Since the frame around the display monitor stays stubbornly vertical, the cockpit seems to tilt dramatically to the left. (See the sidebar, Tripod Setups for Frame-Shifting, for tips on setting up shot like this.)

    For added effect, it helps if the performers tilt their upper bodies to the right, as if resisting the new direction of gravity; and you should lay in a change in engine noise when you edit the audio. (We call this "selling the gag," as you’ll see in a moment.)

    Another trick is to fake motion by moving the camcorder past a stationary subject. For example, if you suspend a model spaceship in front of a plain background, for compositing with a starry cosmos, for example, panning the camcorder from right to left will make the model "fly" across the screen from left to right. To make your home-built Enterprise rush toward and then past the viewer, simply zoom in on the model and then pan off it as it starts to fill the frame.

    If you tilt the video camera a full 90 degrees, you can make objects defy gravity. The classic joke to illustrate this is still effective – push-ups. The idea is to show an exerciser struggle to do push-ups, then do them easily, then one-handed, then on a single finger. Finally, the subject lifts the finger off the ground and floats in midair.

    To perform the trick, find a location where a concrete wall meets a concrete floor. If the two surfaces are together, the lighting is easier to match, especially if you avoid direct sunshine.

    Shoot the "difficult" push-ups from a front angle with the subject on the ground and really doing them. Then, for the rest of the progression, stand the subject against the matching wall, turn the camera 90 degrees sideways, and frame a waist shot from the side. Have the actor push away from the wall, miming struggle, at first, to match the earlier shots. Then shoot the rest of the sequence, until the last finger is carefully withdrawn and the subject floats above the "ground.

    Selling the Gag

    Why start with actual push-ups on actual ground? To convince viewers that the situation is real. It helps if you begin with a wide shot showing the surroundings (but framing off the wall). To really sell the sense of reality, place a cup by the subject’s head. Have the subject reach off screen for a water bottle (established in the wide opening of the shot), fill the cup, replace the bottle, drink and set the cup down again.

    When you shift to the faked push-ups against the vertical wall, use chewing gum or tape to affix the same cup to the wall in the same position.

    Here are some more general rules for making your effects convincing.

  •   Frame off all background features (horizons, light poles, readable text, cars) whose changed orientation would give away the trick.
  •   Substitute fake references instead, like the water cup. To carry the push-up gag further, you could start by having the subject unroll an exercise mat on the ground, then hanging the mat on the wall for the faked shot.
  •   Match the lighting. As noted, avoid strong directional light because it will appear to change when you shift the frame axis. When using artificial lighting, relight the faked shot to match the lighting in the real one.
  •   Don’t forget gravity. Avoid clothing (like blousing shirts or neckties), hair styles, and other items that will point to real-world "down" rather than screen world "down." Sometimes, you can use undetectable fishing line to pull these indicators toward the supposed ground.

    Finally, shoot cover angles so that editing can embed the faked shots in a convincing context of real ones. For instance, end the opening shot by having the subject get up, collect the cup, mat and bottle, and then leave. Then, in the rotated shot, after the floating subject has drifted back to earth, have the actor grasp the cup again. In assembling the show, make another matched cut between grabbing the cup (rotated) and picking it and the other stuff up (right-side up).

    One more hint: never prolong a special effects shot, no matter how good it is and how proud of it you may be. Even Hollywood’s most expensive efforts give themselves away (when studied in DVD freeze-frames, for example). The trick is to linger on the real setup, keep the fake part snappy, and cut back to the real stuff quickly. In short, keep selling the gag, while keeping the gag itself too brief to analyze.

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