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Show
Basics: Audience Scanning |
Can I Shine Beams
Into the Audience?
By
David Lytle, Editor, The Laserist
First Published: October 2000
In
two short weeks after I finish writing this story, I'll be in
Stuttgart, Germany, enjoying what may be the peak experience
when it comes to laser light shows. Even though it's one of the
most awe inspiring, eye-boggling effects you can do with lasers,
it's an effect you won't see in the US.
That's not exactly true--you can see it if you slip into late-night,
smoke-shrouded parties where the crowds aren't too concerned
about venue management following health and safety regulations.
But if you are at one of these parties and see this effect, you
might suddenly find yourself taking an interest in federal safety
rules covering laser light shows …
The
effect I'm talking about is called audience scanning. It happens
when laser beams are directed into the crowd itself, immersing
the audience in cones, tunnels and dancing shafts of iridescent
laser light. Crowds love this effect, and it's no secret why.
Looking at laser beams hop scotching over your head is pleasant
enough, but when the beams reach out and actually touch you,
it's good-bye planet earth and hello next dimension.
I saw my first legally produced audience scanning show (we're
not counting late-night sessions in a private laser studio, where
you dial-up the laser and stand inside a hastily erected field
of beams) two years ago in Amsterdam. Like most Americans attending
the event, I was in wide-eyed wonder. Of course, this was the
annual awards banquet for the International Laser Display Association
(ILDA), so the shows were among the best in the world. But for
many of us poor Americans, deprived all our lives of such tactile
photon fixes, audience scanning was suddenly the Holy Grail of
Laserdom.
I'll
be at ILDA's award banquet in Stuttgart a short time from now,
once again itching to get my eyeballs in the middle of rapidly
oscillating laser beams. But why can't Americans see audience
scanning in the USA? The short answer is safety. Laser light
is brighter than the sun, and direct exposure to a powerful laser
beam is an eye hazard.
Many
lighting professionals assume that laser safety standards in
the US are tougher than in Europe. That's not true: standards
for laser light are nearly identical throughout the world. The
key piece of the puzzle is called the Maximum Permissible Exposure
(MPE) level, which roughly translates into how much laser light
the human eye can handle before damage might occur. Countries
that have safety standards covering laser light (and most Western
nations do) all use the same MPE levels.
Audience
scanning in the US is legal as long as you stay within the MPE,
have equipment safeguards to protect against any malfunctions,
and have a show "variance" approved by the government
regulators. Which brings us to another myth about audience scanning
in the US: hard-nosed safety regulators would find a way to shut
down an audience-scanning show, no matter what safety steps were
taken. Although US regulators are perhaps more active than their
European counterparts when it comes to scrutinizing laser light
shows, they have approved audience scanning in the past.
It
happened back in the late 1970s, during the height of the discotheque
wars in New York City. The club was called Xenon, and its owners
wanted the most exciting lighting effects possible. Dick Sandhaus,
president of Science Faction in New York,
answered the call. He designed an audience scanning system and
got it approved by the Food and Drug Administration, which had
recently begun to regulate laser light shows. Using a full-color
laser, Sandhaus covered the crowd with broad, angular sweeps
of laser light. "People loved it," recalls Sandhaus.
"It worked especially well during a hard blackout. People
would yell and scream for it from the dance floor."
Like
the disco beat itself, however, audience scanning was soon to
vanish from the dance floor. "We chose to stop because other
people were doing it (audience scanning) in unsafe ways, "
said Sandhaus. The outlaw laser operators, who bypassed government
regulations and performed any type of show they wanted, spoiled
the market for legitimate companies, he said. There was, for
example, the notorious heavy-metal rock group that routinely
exposed audiences to a high-powered beams of laser light without
taking any semblance of safety measures. That forced federal
regulators to step up enforcement efforts, and in turn made reputable
companies worry that they might be caught in a safety backlash
against audience scanning.
Since
those glorious days of disco, audience scanning has been all
but absent from legitimate US venues. "Early on, people
who weren't knowledgeable about gave the safety community reasons
for saying that audience scanning should not be done," said
Greg Makhov, president of Lighting Systems Design, Inc., of Orlando,
Fla., and one the leading experts on laser safety in the US.
"While audience scanning can be done safely, it's a delicate
balance between safety and the effect. If the effect wasn't so
good, it wouldn't be worth the risk."
This
concern, for safety, by the way, occurred despite there being
virtually no record of any audience member filing a complaint
about laser light shows-whether the shows were legitimate or
outlaw. Despite a clean safety record that persists to the present
day, regulators around the world will still crack down on laser
shows if they feel the all-important MPE level is being exceeded.
It's recently happened in the UK, where audiences scanning shows
were completely stopped for a long period. In the rest of Europe,
a host of established companies continue to perform audience
scanning shows with a professional attitude toward safety.
The
MPE level itself, however, is once source of trouble. While few
dispute the biomedical evidence supporting the MPE, even knowledgeable
people will disagree on how to compute the level for a particular
laser show. Some will take a conservative approach to crunching
the numbers, while others will do the math differently and come
up with higher permissible light levels. The range of interpretation
is possible because measuring the safety of an effect is rarely
as easy as putting up a meter and reading a number. Because shows
usually contain numerous audiences scanning effects, the safety
of each effect must be determined and then the cumulative impact
of the entire show needs to be evaluated. For a complex show,
it can be a time-consuming process.
For
audience members, it's even worse. Relying on your eye alone
to judge the safety of a show is far from foolproof, said Makhov.
Bright green and white colors, for instance, can make you blink
and avert your eyes even when the MPE is not exceeded. On the
other hand, deep reds and blues can easily exceed the MPE yet
not cause an averse reaction.
If
you find yourself in a show that features audience scanning,
is there anything you can do to determine a show is safe? The
best measures is to know the company that's producing the show.
Any legitimate company doing audience scanning will be able to
point to their equipment safeguards and safety measurements.
If
you find yourself at a rave or other situation with an outlaw
laser company, you can still check the basics. Fist and foremost,
ask the laser operator what kind of laser is being used. If it's
a pulsed laser, then stay away from the show entirely. These
units fire individual "bursts" of laser light that
generate a shock wave in human tissue. Even though the power
level of a continuos wave laser and a pulsed unit might be identical,
the concentrated pulse of light is far more dangerous than light
delivered in a continuous wave. Unfortunately, there have been
a frightening number of reports of audience scanning shows using
pulsed lasers both in the US and Europe.
The
next step to increase your safety is to put distance between
you and the source of the beams. Laser beams expands as they
travel through the air, reducing the safety risk by spreading
the beam's energy over a larger area. If the show feels too hot,
move to the back of the room. Finally, make sure the beam is
moving all the time, and moving very rapidly. How fast is fast
enough? A beam that stays in one spot for just a few milliseconds
can be a hazard, and this can often occur when the beam pauses
for a moment at the end of scanned line segments. But unless
you have the right tools, it's practically impossible to measure
this.
The
best rule of thumb, obviously, is to make sure that whoever's
doing audience scanning has taken measurements of the show, done
the safety calculations, and installed the proper equipment safeguards
to protect against a mechanical breakdown.
I hope
a company in the US will take up the audience scanning challenge
and open the eyes of Americans to this dazzling effect. Until
then, it's off to foreign shores.
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