Colors in concert.

I am so psyched! I'm sitting in the front row at a Smashing Pumpkins concert and it's one minute before show time. Flashes of light and color appear. Everyone surges toward the stage. The band starts to rock and the lights flicker wildly. The stage is alive with shades of reds, blues, and greens. Floored by the kaleidoscope of colors, I'm eager to find out how lighting designers create such a spectacular visual display.

So after the concert, I track down Lawrence Upton - who designed the lights for the Smashing Pumpkins - and some other lighting designers of the rock world. Upton says he works hard to give every band a unique onstage presence. By listening to a band's music, he says, "I Can decide which colors will best visually interpret each band's sound, mood, and image."

THE RIGHT LOOK

You might think Upton and other lighting designers would need hundreds of colored bulbs to create the right look. But that's not true, Upton says. Every show starts with plain white light, the kind you get from a regular light bulb (and from the Sun).

That's because white light is made up of all colors. You can see this for yourself by shining a white light beam through a prism, a clear crystal that refracts (bends) light rays to split white light into a spectrum, or range of colors (see "The visible spectrum," p. 8).

Light is a form of energy that travels in waves, explains Dennis Varian of Light and Sound Design in Los Angeles. And each color has a different wavelength. When the light waves travel through the prism, the different wavelengths bend different amounts. That's why they separate into a rainbow of colors.

But lighting designers don't have to use prisms to get color from white light. Instead they use filters, colored pieces of glass, which they place in front of the white light beams. The filters act like wavelength "strainers." They hold back, or subtract, some of the color wavelengths that make up white light, explains Varian - the way a strainer holds back pasta but allows water to pour through. The wavelengths that pass through the filter are the ones your eyes see.

TRI-COLORED CONCERT

But wouldn't you still need hundreds of different-colored filters to come up with a dazzling. variety of eye-catching shades? Upton may use up to 18 colors to design a show, but "you can be creative with just three," he says.

That's because our eyes have only three kinds of color-sensing cells. Each kind detects red, blue, or green light. By stimulating these receptors in different combinations and to different degrees, these three primary colors of light can re-create all the colors of the visible spectrum.

To set a psychedelic mood for the Smashing Pumpkins concert, Upton combined a variety of lights and colors. First he chose the colors he wanted - deep blues, greens, and pastels. The color that's produced, Upton explains, depends on how you combine the filters and beams of light. For example, when Upton wants to shine some yellow light on Billy Corgan (Smashing Pumpkins' lead singer), he could just use a yellow filter. But for a more dramatic effect, he can combine beams of red and green light (see "Mixing primary colors" p. 8). The red filter lets only red wavelengths pass through. The green filter allows only green wavelengths through. When combined, the two beams stimulate your eyes' red and green receptors in equal amounts. Your brain interprets the combined signal as yellow.

After Upton finishes mixing his colors, he chooses a variety of lighting equipment, including strobes (flashing lights) and Icons - stationary lamps that rotate 360 [degrees] to beam colored light anywhere on the stage.

Lighting designers also use light and color to mirror the intensity of a song. "We have to use some very powerful lights," says Patrick Woodroffe, lighting designer for the Rolling Stones, who are now on tour. So, in addition to strobes and lamps, Woodroffe uses Lightning Strikes - powerful strobes that mimic natural lightning (without the danger).

To enhance the Stones' spectacular, Woodroffe uses lots of bright reds, blues, yellows, "and a lot of white light," he says. If you've ever seen the Stones rock, you know the bright colors add drama to the show.

COLOR CUES

Changing the light and color during a concert is a snap. Most of the "changes" are computer-programmed, says Kim Martin, who designed the lighting for The Breeders' 1994 "Last Splash" tour. The computer allows her to recreate the dramatic looks she has designed, performance after performance.

"I decide how I want the colors to change during a song, and where those color `changes' should be placed," she says. "The final step is to program those changes, or cues, into the computer. During the show, I just hit a button to recall a particular color combination."

It must be a nice career: fiddling with lights, working with cool bands, and enjoying the fruits of your labor while you kick back at a concert every night. Patrick Woodroffe agrees. "It's a fantastic job," he says.

Where do I sign up?

LIGHTS,

COLOR,

ACTION!

What happens when you

mix colored beams of

light? See for yourself.

WHAT YOU NEED:

3 flashlights * cellophane wrap (a variety of colors including red, green, and blue) to act as filters * tape * white background (e.g., note card, screen, or wall) * a darkened room

WHAT TO DO:

1. Cover each of two flashlights with a different color wrap. Fasten with tape.

2. Turn off room lights. Switch on flashlights and hold each about a centimeter from the white background so that they form overlapping circles of colored light (see diagram, left). Record what you see in the overlap region.

3. Try different color combinations. For each, predict what you'll see, record your observations, and try to explain your results.

4. Try using three flashlights with your red, green, and blue filters to create the colors in the diagram at left. Do your colors look like the ones in the diagram? Explain.

DON'T STOP NOW!

What happens when you overlap colored filters instead of beams of light? Explain your results.