paradoxism Posted October 25, 2007 Share Posted October 25, 2007 Hi all! I've been asked to design the lighting and video rig for an amateur production of the schools edition of We Will Rock You, and the directors are adamant that they want a laser for the laser cage effect (I'm sure your imaginations can provide you with what it looks like even if you haven't seen it - vertical cone of laser beams making bars!) Aside from the worries I have about the beam spread for the limited height on their stage, my main concern is the intensity level as I have had very little experiance with lasers. They want a bright green laser that has high definition through haze and can be seen (with the rest of the stage dimly lit) but that the actors can walk through and interact with. They helpfully provided me with a 5mw laser pen saying that they could get a number of those and arrange them to make a cone (don't you love non-technical types!) but a quick demo with a hazer showed them the error of their ways. However I'm not sure what power level I need to be looking at. Where would be a good middle ground between safety and brightness? I hasten to add that these are only going to be one off effects (I'm not looking for stuff that I can then use to scan through the audience etc!) and I am also not after lectures on not looking into the beam! I just want a good level that actors can safely walk through for very limited periods without catching fire and losing limbs! Worst case scenario - actor is stood braking a 'bar' withut realising it and so has a laser dot on his arm for maybe 2 minutes in the same general spot. My current feeling from internet research is that a 100mW green (532nm) laser will do what I want but I thought I'd check with those who are wiser than I! Any thoughts? Link to comment Share on other sites More sharing options...
johnhuson Posted October 25, 2007 Share Posted October 25, 2007 No expert on laser's but have you thought about using a gobo instead? I'm sure you probably have but thought I would suggest it anyway as you don't seem 100% happy with the idea of using a laser. Link to comment Share on other sites More sharing options...
J Pearce Posted October 25, 2007 Share Posted October 25, 2007 A ring of VNSP Pinspots gelled in a saturated green gel might be a good compromise. Link to comment Share on other sites More sharing options...
david.elsbury Posted October 25, 2007 Share Posted October 25, 2007 Or AR111's (Brian can tell you more about those, or do a search) Link to comment Share on other sites More sharing options...
greenalien Posted October 25, 2007 Share Posted October 25, 2007 Since it's a school, I'd start by reading this :HSE Laser Safety Guidelines For a 'cage' effect, you need about 30mW per beam for a reasonable effect, so you have several options : 1) Use a number of small laser pointers. You can find red 5mW examples on ebay from a few pounds each but they aren't very bright. Just about usable in a dark room with a smoke haze; choose 632nM rather than 650nM wavelength if you follow this route, they are brighter for the same power.2) Same thing but using multiple green laser pointers. Much brighter but more expensive. Again, look up 'laser' on Ebay.3) larger single laser, bouncing off multiple mirrors - very hard to align, needs expensive first surface (front-coated) mirrors or the beam will get more diffused each time it's reflected.4) single laser with diffraction grating - to give a 'cone' of lines - and a single deflecting mirror for each beam to get each one parallel - probably the cheapest option but you'd need at least a 250mW laser to be bright enough, and enough overhead room above the 'cage'. Bottom line is that for a school production, a spotlight with a suitable gobo will be much easier and more cost-effective, with none of the laser safety implications. Not so challenging though! Good luck! Link to comment Share on other sites More sharing options...
paradoxism Posted October 25, 2007 Author Share Posted October 25, 2007 Thanks for the replies Whilst it is the schools edition of WWRY it is not a school show - it was released under the old licence requirements and is actually an amateur youth theatre branch for quite a successful amateur society. Budget for lighting/visuals is going to be around the £1k mark because the licence prohibits making a profit on it and the take on the door is likely to be high, so they're going to town on it and want to make it the best amateur version possible! I agree that a dot circle gobo would be an easier option and would solve some of the 'beam angle' issues, but they want to try and achieve a laser effect for the futuristic feel. Also with the distance involved the gaps between the gobo beams will be fairly narrow and obscure a lot of the action. Greenalien has given me one of the crucial pieces of information that I was missing - namely the kind of power required for a decent 'bar'. The 100mW laser I was leaning towards in the first place would seem to be bright enough for what I am after as it is a scanning unit with a dot frequency that should allow 100mW bars. Presumably the persistence of vision should have a minimal effect on the brightness as you are seeing a 100mW beam refreshed each time rather than splitting the beam energy 10 (or however many) ways. There are DMX controlled versions around for £200 or so (aimed at the club market) and presumably can be found in hire stock if I ring around. It's a class 3b laser and so as long as steps are taken to avoid direct viewing of the beam source there shouldn't be any hazard risk with skin contact etc. Does all this seem to be reasonable or is my reasoning about the beam intensity flawed somewhere? Show is still a while off but I'm trying to get potential issues ironed out early! Thanks again for help given so far. Link to comment Share on other sites More sharing options...
boatman Posted October 25, 2007 Share Posted October 25, 2007 The team at The Scottish Theatre Forum did this show earlier this year and raised a huge amount of money for the Edinburgh Sick Children's Hospital. They're a friendly bunch and will be able to give you lots of tips. Link to comment Share on other sites More sharing options...
techiegsy Posted October 25, 2007 Share Posted October 25, 2007 The team at The Scottish Theatre Forum did this show earlier this year and raised a huge amount of money for the Edinburgh Sick Children's Hospital. They're a friendly bunch and will be able to give you lots of tips. If you do get any good infomation from these people, I would love to have it as I have a similar dielemma. Link to comment Share on other sites More sharing options...
cedd Posted October 25, 2007 Share Posted October 25, 2007 We have done this show and used a green laser moving head. It wasn't a particularly expensive unit from memory, indeed it may have been from the likes of "showtec" though don't quote me on the name! Did a very good job for a big stage. LX height was reasonably high, but the nice thing with the moving head is that, whilst we didn't need to, you can correct for actors being ou of position and possibly move your laser cage round to different spots on the stage (though you say you are limited by height so maybe not possible). I'd always wondered about the possibilities of multiple laser pens for a varety of effects. Bit of bodging to add an external switched power supply for on and off and you're sorted! Unfortunately the LD from our production of WWRY is out of the country so getting more precise details of our moving head laser is iffy at the minute, but I'll see what I can get out of him when I can. Link to comment Share on other sites More sharing options...
Ben Lawrance Posted October 25, 2007 Share Posted October 25, 2007 I've seen it done with a Mac2K pointing straight down with a suitable gobo selected. Add a dash of haze and the audience are none the wiser. Link to comment Share on other sites More sharing options...
dave singleton Posted October 26, 2007 Share Posted October 26, 2007 It was a VL3000 but close! :) Link to comment Share on other sites More sharing options...
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