Lights in Motion

Natural lights sparkle, shimmer, flutter, flare, glimmer, gleam, revolve, reflect and radiate. Here's some tips to dazzle your viewers with lively photoplays.

Real-world lights are often moving (e.g. headlights), flashing (neon signs), or flickering (fires, CRTs). Unless you're shooting news or documentary programs, you'll want to control these lively light sources and, if possible, make them part of your lighting design. Since the actual lights are often too bright, too dim, wrongly placed, hard to manage, or just plain absent, you usually have to fake their effects with lighting equipment.

Moving Light Basics

The first step is to imitate the actual light. Consider a representative example: lighthouse beams. Some systems use revolving reflectors that rotate a narrow, continuous beam in endless circles. Others shine the light in all directions at once, but "occlude" (mask or douse) it intermittently. To simulate the first type, you would sweep a spotlight beam repeatedly across the frame; to copy the second type, you would aim a stationary light, masking and unmasking it rhythmically with a flag. It's these tiny details that help "sell the gag" (about which, more later).

In addition to type of movement, you need to emulate the light's character. Car headlights are hard-edged and highly directional, while neon emits a soft, diffuse glow. Headlights throw large, intense beams while neon signs are much feebler. Headlights are (nominally) white, while neon signs are typically red or blue. Your simulations should match the originals.

When you've perfected your impersonation, consider the light's position and direction. Car headlights start perhaps three feet off the ground, while a neon sign in a bar will usually be higher than a subject's face. And don't forget that "direction" means screen direction. If you show opposing closeups of two subjects raked by passing car headlights, make sure the beams come from and move in opposite screen directions.

Finally, be careful with exposure. Moving lights often change the distance from source to subject, and brightness increases dramatically as the distance lessens. To avoid problems, try to stage light movement parallel to backgrounds. Then get a good exposure setting and lock it by switching to manual.

Contrast is also a big problem. Unless you specifically want your subjects blasted white by a prison searchlight or a descending UFO, set your f-stop to include at least some shadow detail and moderate your moving light so that it overexposes the scene only slightly as it passes through.

Moving, Flashing, and Flickering

Lights in motion come in many flavors, but a few examples can suggest how to create most typical effects.

Moving lights that sweep across the frame (headlights, searchlights, etc.) are best mounted on stands. For lights that must tilt as well as pan, try mounting the light on a tripod (the standard camera bolt on a tripod head mates with a 1/4" x 20 nut).

Flashlight effects require free hand-holding. It goes without saying that all lights are hot, so never hold them without heavy gloves. Tough leather work gloves are okay, but if you do this stuff a lot, invest in a pair of welder's gloves with ample wrist and fore-
arm protection.

Flashing lights like neon are created by moving an opaque flag (black foamcore board works great) in and out of the light path. For an extra-spiffy effect, tape a two-inch-wide strip of neutral density filter along the leading edge of the flag. That will make the light seem to brighten as it flashes on and dim as it turns off.

Police car lights are easier to fake, now that most of them flash instead of revolve. Gel the light source red or blue as needed, hold the flag very close to the light, and work it rapidly to simulate a strobe effect. If you have the resources, use both red and blue lights, with a crewmember working each one.

The most common flickering lights are fire and CRT (TV or computer) screens. The classic fire effect uses an orange gel on the light source behind a horizontal stick with a "hula skirt" of cloth strips stapled to it. Wagging this rig in front of the light throws an orange and variegated glow on the scene.

For a convincing "explosion," put a very bright off-screen light on a dimmer that also has on/off capability. Set and lock your exposure, turn the light on full and move it in until it almost wipes out the image, then turn it off again. On cue, snap the light on, then gradually dim it, wiggling the control to vary the light intensity as it drops (you can also experiment with your hula skirt rig).

Lighting Instruments

Small spotlights work best because of their versatility. For more on mounting and using them, see Pulling the Plug, September 2005, which also discusses flashlights and 12-volt spotlights.

For flashlight effects, you may need a hard-edged circle of light too small to achieve with even a spotlight. For this, you need a "snoot," a long tube that further narrows the light beam. You can buy snoots that fit on studio spotlights, or make your own (Figure 1). Cut a square of sheet metal that will fit in your spotlight's gel frame holder, then buy a can of asparagus spears, which come in an unusually long, skinny tin. Cut a circle out of the metal square to match the can diameter, leaving flaps to bend up and attach to the tube (epoxy usually works well). Slip this into the spotlight's holder and you're ready for action.

A final tip before we wrap here: all effects work better if you "sell the gag" by supporting them both visually and aurally. Start with a shot of a lighthouse, squad car, burning building, or whatever to establish the light source before using your lighting effect. Meanwhile, fill the track with fog horn bleats, police radios, roaring fires, etc. to add extra realism. Works every time.

Good lighting!

Contributing Editor Jim Stinson's book Video: Digital Communication and Production is out in a 2nd revised edition

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