Audience Scanning a few questions..

sorry if this is a noob question but...

If a mini projector is never making anything over the MPE does that mean it requires no variance to use for scanning the dance floor in a club-??
A local club owner has asked me advice.--
These are now as cheap as 20$ (AixiZ sez they made WAY too many and the supply of them is HUGE in China and they are not selling fast enough thus the big discount over what there ere a year or so ago)- they have about 60mW of red650 and maybe 30 mw of 532. The gratings never stop moving (expeet if the dc stepper keep quits working)and the beam has been divided hundreds of times. On sound response mode they TTL blank off and on.- but when they are on ON the gratins are moving- some have a control for this from slow to fast- but he could just set then for fast when installing and IMo that makes they a little safer.

He wants to do a perm install of these( 6 to 8 of them) and likes lasers better then LEDs-These will be about 15 feet above the dance floor- pretty much straight down.

On a side note for $20 w/free ship- These can be used in low power LUMIA (but they blinking spoils the efx IMO) Or remove the lasers,fan and drivers and run direct onto to the LUMIA glass--

Which is related to my other question- Can LUMIA be done safely onto the audience?-(other than just using lasers <5 mW)

Just the MPE part not the PJ itself-- Tim had a 'store-bought' iirc @ $600 RGB Lumia from China- IIRC at TEXLEM I in San Antonio- and here in a thread too - pretty nice kit but very DIY do-able for less$..
TY in advance for your info& opinions-- Hak

hakzaw1 said:

If a mini projector is never making anything over the MPE does that mean it requires no variance to use for scanning the dance floor in a club-??

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Yes, as far as I know. But good luck impressing people with sub-MPE powers.

is there any other 'kind' of safe audience scanning?- It all has to be pretty dim to be safe..
But I do agree with what you say..I read that one way the audience can crudely judge what they are watching is to close your eyes , look away from all light and see how long the afterimages appear. if they fade quick you have not (yet) been hit by 'too much' - There a longer piece at Pangolin on their take on audience scanning. good read -and makes a good argument for still keep trying to do both- be enjoyed and be safe.

But I still need help with LUMIA and how to meter it and do the MPE calculations.

I mostly shoot all mine on the walls- especially in the corners and up on the ceiling.
Small -private - no kids--

But LUMIA on at a 'TOGA' party etc. would be interesting to see audience scanning style.

hakzaw1 said:

is there any other 'kind' of safe audience scanning?

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The idea is to keep the power high when above the audience, and then lower the power as the beams drop into the audience.

Besides, "safe" is relative. There are many venues in Europe that perform audience scanning at 100x MPE with no reported injuries.

Cyparagon said:

The idea is to keep the power high when above the audience, and then lower the power as the beams drop into the audience.

Besides, "safe" is relative. There are many venues in Europe that perform audience scanning at 100x MPE with no reported injuries.

Click to expand...

Highlighted the key word. I do not disagree though. I will say this; the small amount of retinal damage I do have is from crowd scanning at a party.

A lot of the more impressive crowd scanning uses lasers that are located far enough away that the MPE is well below permitted levels at the distancebeams intersect the audience. However, nearing the source -- which is out of reach by the audience -- it is much higher power, creating a bright looking source.

You can only really pull that off if you have a large place like a concert hall. If you're shining downwards onto a dance floor it may be too close to be safe for your audience. You really do need to measure the energy density of the points of light where they may hit your audience's eyes.