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Show
Basics: Laser Show Primer |
Atmospheric Effects Are True
Showstoppers, Indoors Or Out
By
Tim Walsh, Laser Spectacles
http://www.laserspectacles.com
The
laser effect that most causes audiences to gasp with wonder and
delight is the experience of seeing laser beams move through
open air. These effects are called “atmospheric” because
they rely upon beams sculpting the atmosphere of the venue, with
no projection screen involved. Atmospheric and beam effects are
a true 3D experience, with no tricks or 3D glasses needed. There
are, however, some basic guidelines to producing a successful
atmospheric laser show. In this article I will discuss how venues
can maximize the impact of atmospheric displays and I’ll
analyze the different types of effects commonly used to reach
out and “touch” the audience.
The first thing to remember about laser beams concerns visibility:
a laser beam passing through perfectly clean air will be invisible
because there is nothing to reflect or scatter the light. To
help make the beams visible indoors, laserists often introduce
particles into the air, usually using theatrical fog machines.
Beams passing through water fountains or mist will also create
beautiful sparkling displays (be prepared for the high humidity
that comes with this type of effect). Outdoors, the use of higher
powered lasers combined with the normal dust found in the air
means that beams are usually visible in the night sky.
The second component of beam visibility has to do with sight
lines. If a laser beam is coming toward the viewer, the apparent
brightness of the beam is increased. Beams that are perpendicular
to the viewer are perceived as much less bright. Those going
away from the viewer vary in apparent brightness depending upon
the ambient light in the background. For creating successful
beam shows, it is wise to plan the display as coming towards
the audience.
The last element to consider is ambient light. The easiest and
most cost-effective way to increase the brightness of an atmospheric
laser display is to make the venue completely dark. This lets
the laser beams be experienced at their full intensity. Keep
in mind that the audience’s eyes may need up to ten minutes
to adjust to the dark; after that they can perceive laser lights
much more intensely. Check a potential outdoor show site at night
to find ambient light problems. Street lights or security lights
from blocks away may be shining directly at the audience. I have
even seen automobiles being directed by security police during
a show in such a manner that car headlights shined directly into
the audience.
For indoor shows, a “dark check” should be performed
in which total darkness is attempted. Be sure to give your eyes
ten minutes to adjust to the dark, and then identify and eliminate
all sources of possible illumination.
Getting
the Power Right
The power required to produce an effective beam display is directly
related to the size of the venue, the ability to fog the venue,
the ambient light level, and the viewing angle. If the last three
factors can be optimized, you can get by with a lower powered,
less expensive laser. If you are unsure about any of these factors,
however, get the largest laser that your budget will allow.
Now that you’ve got a venue which is properly set up for
atmospheric effects, what kind of laser magic can you do? The
simplest effect is the straight beam, in which a static beam
emanates from the projector. The beam can target single or multiple
mirrors to create a sequence of patterns.
Straight beams can also target remote devices that add interest
to the show. One of these devices is called a reflective diffraction
grating. It reflects a beam like a mirror while also breaking
up the single beam into multiple shafts of light. The grating
also acts like a prism and spreads apart the colors of the output
beams. One of the more popular effects is the Machida grating,
which projects a 180-degree fan of beams from just one point.
Other, more complex remote devices that straight beams can target
are motorized effects. For example, a simple mirror placed on
a rotating shaft produces beams that sweep through the air over
and over again. This concept has generated a product called a
mirror barrel that many companies use as a standard part of their
show.
By positioning the laser beam using standard laser show graphic
X/Y scanners, we can place the beam under artistic computer control.
These effects are called scanned atmospheric effects.
The simplest of these effects is to sweep the laser beam back
and forth creating a thin sheet of light. Under the right conditions,
simply blowing smoke through a sheet of light will create a moving
cloud effect that audiences love to watch. Taking the sheet of
light and moving it up and down adds a whole new dimension to
explore. Changing colors adds depth and interest to any of these
atmospheric effects, especially indoors under low ambient light
levels. The effects compound in complexity from here.
Adequate coverage of the entire audience is important if you
want everyone to feel the laser display close up. Sometimes the
shape of the venue will require multiple projectors so that everyone
experiences the show at the optimum viewing angle. In many cases,
this can be achieved by using fiber optics to feed remote scanners
far from the main laser.
Audience
Scanning
The ultimate in beautiful, intense, laser atmospheric effects
is created by using the above techniques to actually reach out
and touch the audience with laser light. This is called audience
scanning. There is a danger inherent here: the light from a laser
beam can be strong enough to damage the eye. But if the laser
beam is moved rapidly enough through the air, it’s power
can be spread over a sufficiently large area to eliminate the
eye danger.
In the United States, however, government regulations generally
do not allow audience scanning. In the U.S., laser beams can
be no closer to an audience than three meters above the floor.
In other countries, such as Germany, companies use audience scanning
effects in conjunction with light sensors and fail-safe scanning
interlocks that shut off the beam immediately if a safety hazard
is detected.
As technology advances, and our understanding of eye/color/laser
power factors increases, perhaps we will see government-approved
audience scanning become a part of shows in the U.S. In the meantime,
we Americans can always enjoy the beauty of pure laser beams
creating atmospheric beam patterns overhead. There is nothing
else like it!
Tim
Walsh is president of Laser Spectacles, Inc., and currently serves
as Chair of the ILDA Awards Committee.
Additional
Show Basics Links:
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Images from top:
Laser Images, Inc.,
Laserland GmbH,
Laser Systems Europe
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