Senior Member
QS Safety Check Request
Hi,
Is there anyone with QS who's familiar with cue safety who'd like to check a cue for me prior to it being made public?
The worry is there's a cross over point in the cue and I want to try to ensure that its not "Hot".
Impossible to tell from the preview alone. Probably either needs a projection test or a metered projection test.
Its a great cue BTW and highly unusual.
Senior Member
Ok well I guess this one will have to go on the back burner until such time as I'm able to make the necessary safety adjustments my self.
I just can't release it in all conscience until I know that there aren't hot spots caused by the crossover.
Pity because its a really complex and unusual beam effect, twin segment, quad colour tunnel, morphing to 3 smaller tunnels, morphing to 4 wrap around sheets / flat tunnels which are split left and right between red & white and Green and Yellow combinations making a different colour sheets / flat tunnels effect for each eye, morphing back to the original tunnel.
This preview is squashed and off centre. To make the effects visible I had to stretch the window large and thus out of ratio so what is round appears oblong. I've also raised the pattern above centre to give a better look inside the flat tunnels / sheets.
Obviously normally displayed the pattern is round and the tunnels / sheets are designed to come at your eye level head on.
The idea behind the cue is to place the audience in a position where they are constantly being taken through walls into new coloured experiences as the pattern both rotates and morphs around them.
Senior Member
Given that anyone playing the effect should be making their own safety checks, AND could be using a vastly different power projector to you, don't you think you're over-egging the safety 'pudding' somewhat (so-to-speak)?I just can't release it in all conscience until I know that there aren't hot spots caused by the crossover.
Most live shows (to quote you - when 'multi-cueing') will have overlapping patterns at some point. People don't test every possibility before playing them, because its essentially random when you start combining cues.
So long as the brightest point possible by your projector at that location is below MPE (or 10x) then you're fine
Senior Member
I'm being careful given the crossover is more or less static.
As its a synth file, I'm not able to examine the individual frames in QS to establish where the points are and thus if they lie side by side at crossover or if any actually intersect causing a doubling up of power at the point.
I think the easiest answer would be to colour a short section of one of the intersecting lines black using keying so that effectively there was a very short break in one line at the point where they cross thereby preventing any power doubling. The trouble is QS is limited in this way (obviously it has editing and creation limitations to stop it competing with Beyond). So I'm kind of stuck.
I also don't have a projector so I can't make any kind of visual assessment or place a power meter at the respective points of intersection to check for hotspots.
Senior Member
Ok, so the point will be hot/bright. Does that matter if the person using the effect has ensured that the projector at full power, at closest point of entry into the the audience is at or below MPE?
Senior Member
Well if the general beams are at MPE then the spot is going to be at 2x mpe. If its at 10x mpe then it could be as high as 20x mpe. Thats why I'm trying to avoid releasing with a hot spot because unless projected at 50% of the mpe setting calculated as safe then the cue is likely to result in mpe being exceeded by a factor of 2 (assuming of course the points do intersect).
If you have QS and want to try the cue then please feel free to ask me and I'll supply the file.
Its always been my intention to make it a community release.
Senior Member
How can that be if you use the simplified method of calculating MPE as detailed on the forum?Well if the general beams are at MPE then the spot is going to be at 2x mpe.
A laser cannot produce more power than it is capable of producing, regardless of how many hot spots or crossovers you have.
Because that "simplified method" has other assumptions in it that you are forgetting about, namely beam speed, pulse duration, and most importantly, number of pulses per second. Remember: The 10X MPE level is *NOT* eye-safe for a continuous exposure. (Not by a long shot!)Originally Posted by norty303
Of the three exposure levels you need to be concerned with (average irradiance, single pulse irradiance, and multiple-pulse irradiance), the multiple-pulse limit is the one that is most restrictive. That is very important in this example.
For a given scan speed, it's assumed that the beam will never be in the same place twice for a given frame. Thus, you can divide the number of points in the frame by the scan speed to get the number of pulses per second at any given point in the frame. Plug that into the formula, and you can calculate the multi-pulse MPE. But if you have a cross-over point in the frame (like the pattern above), then that will double the exposure at the cross-over point, since the beam will be there twice for each scan. Get it?
This is why audience-scanning is so difficult. You really do need to test all the frames in your cue list (or at least be sure you know how many points each one has, assuming no duplicate points) in order to ensure safety.
Adam
Senior Member
But correct me if I'm wrong, but if you're scanning the same point twice you double the exposure (or more correctly 1/2 the interval between scan repeats) compared with an ordinary scan don't you?
As the same point gets a second scan when the laser is tracing the 2nd half of the shape during a time when the power would otherwise be off at that point.
EDIT: Cross posted with Adam who I think probably explained it better.
Senior Member
Hmm, well then that sort of calls into question how useful the simplified method is, as just about every live show will have some cross-over.
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