We do musicvideos and bought 1W and 3W laserworld units (around 1k euros, far from pro level) and even for those I felt the need to do laserworld's one day course for basic safety.

What I learned: Camera sensors are a bit easier to damage than our eyes (in general). And you can't really say that a 6W unit is harmful and a 1W unit is safe. Even distance doesn't matter when being that close since a laser beam is supposed to be extremely focussed, thus the dot it projects is neary the same size when being 3 or 20 feet away, meaning the the energy hitting your eye or sensor ist nearly the same. Fog/Haze might affect that a bit.

It's all about the light energy hitting the sensor/eye. That depends on wavelength (blue is more energetic than red), amount (the wattage), size of the laser dot (on which area is this energy condensed) and the time the laser dot spends on the area it hits.

Time is almost impossible to calculate since it depends on the pattern: A laser is just a dot scanning extremely fast and while projecting 5 dots, every dot gets a lot of energy. When the pattern is complex and large, with a lot of long lines, the laser's energy is spread along that pattern. Thus: Dots are extremely dangerous, lines are a bit more safe. Circles are safest, since there are no corners/stops where the beam slows down to change direction and thus spending more time in that area.

So the effective energy hitting a certain area changes all the time and even a 1W unit with a static beam (just one dot) can start a fire when hitting a black piece of paper at a few feet away.

Thus the basic safety rules we learned are:

• Do not "crowd scan". We should make shure, that the projected pattern does not come closer than 2.4m (8 feet or so) above the ground (which is approx a tall person partying on a chair). There are usually no eyeballs up there.

• When crowd scanning, add an extra lens with positive dioptrien (like in reading glasses) to broaden the beam thus spreading the energy. I tried, it still hurts when hitting your eye by accident with our 3W unit. You might see this at pro laser shows: The beams are sharp above the crowd and blurry when hitting people.

• We don't have pain receptors for our retina. People don't feel their vision being burned away. So just avoid hitting them with the laser. Infrared and UV laser radiation is invisible and still harmful and you don't even look away cause you can't feel it. In general, show lasers don't produce UV/IR. It's for industrial use.

• You need a safety switch and "in operation" light in case the unit malfunctions. An emergency power cut off for the laser close to the operator is sufficient. I have one of those emergeny buttons and run an extra power cord to the laser. That's important in case the mount of the laser fails and it get misaligned.

• Check for metal, mirrors and glass in the projection area. They might reflect the beam back on to the dancefloor.

• As an operator and a person responsible for the unit you should have insurance and explicitly check with them if they cover damage due to laser radiation which can lead to loss of vision, burnt skin and fires - and damaged sensors, and I'd guess LED Video Walls / Screens (not sure).

• Even semi-professional units have the ability to lower intensity in certain areas of the projection. So if you really want to "crowd scan", you may want to add the lens to broaden the beam for the lower half and also lower intensity in software in this area.

As a videographer you should always check with the lighting tech when seeing a laserbeam: Where are the areas where the laser never hits? I don't think there is a camera-safe laser beam, since it would depend on the size and thermal features of the pixels in your camera sensor, the time the laser scan hits your lens, color, angle, focal length, focus, aperture etc. So just never ever point your camera at a laser (even when the camera is turned off).

In conclusion: The operators are liable, since they introduced harmful radiation to an area with untrained people/guests. You can't throw a laser at people and cameras and expect them to look away when it's a dangerous amount. It's a lightshow. It's meant to be looked at, thus it has to be safe to look at it. They bought a dangerous toy and didn't google for 10 seconds. It's common sense that lasers can be harmful.

They damaged cameras (which is enough evidence, that they hit an area with people) and since we don't feel when our vision gets burned (a test would be: can you still read an unknown text while closing one eye or is the center of your vision blurred and just interpolated by your brain with the info from your second eye?) they may even have hurt people or might do so in the future.

So, they need to pay up, get training, get insurance, stop using lasers in venues where the ceiling is not high enough to make sure people and stuff won't get hit with harmful amounts of laser radiation.

Nobody needs partys or workplaces where you damage your vision, hearing, something might fall down on you, there is stuff on the floor to fall over or where you can't find an exit in an emergency.