Laser powers and visibility: A laser beam is only visible if there is particulate matter in the air, such as dust, fog, and smoke. The power of a laser beam is measured in watts and milliwatts (1/1000 watts). The minimum power needed for a laser light show in a dark, medium-sized room (like a hotel ballroom) is about 500 milliwatts to 1 watt. Somewhere between 5 and 20 watts is typical for indoor use. In large arenas and outdoors, 10 to 80 watts are common.
Wattage alone does not determine how visible the beam will be. For example, a 1-watt green laser beam can appear as bright as a 3-watt red beam, since the eye sees green light better than red or blue.
Therefore, when deciding how much laser power to use for your show, there are many factors the laser company will consider.
These include:
Laser color: Green is the most visible You can use a less powerful (and thus easier-to-use and less expensive) laser if green is acceptable.
Ambient light: Keep your event as dark as possible during the laser show. The laser won’t need extra wattage to “punch through” ambient light.
Laser beam divergence: Some types of lasers have tighter beams than others. Low-divergence beams look brighter since the light is concentrated in a smaller area.
Amount of fog and smoke: Fog helps the laser beams be more visible. If you can’t use a lot of fog, then you’ll need a more powerful laser.
Area projected: If the audience is spread out, then the laser’s power will be spread over a larger area. A higher-wattage laser is required.
Audience safety: In many parts of the world, the audience is scanned with laser beams. The beam power and divergence must be sufficient so that the beam and scanned effects are visible, but that there is no eye hazard. One solution is to have the beam be at full power when above the audience, but at lower power when scanning the audience.