UV calculations

[back_ache]

I have a got a show coming up next year that needs some UV trickery.

 

They would like it to fade up and down so I am thinking of using HF dimmable ballasts, is there anywhere I can get formula to allow me to eventually work out that with a given hanging height for the tubes how watts worth will need to activate transparent UV paint on the stage floor?

 

Basically I want to base the number of ballasts and tubes on science rather than guesswork so I can justify the cost and indemnify myself if they force me too few. Or to jusify using a UV cannon and DMX louvres or to make them forget about trying to do it a fancy way altogether!

[David A]

There are too many variables, particularly the efficiency of the paint to fluores to the level you want.So do an experiment with the materials you are going to use and base your requirements on that.

[nico_ah]

Hi,

 

A manufacturer, WILDFIRE (US) can supply fresnels especially designed

for UV emission. I think you should try and see these...

 

ROBERT JULIAT also designed some UV profiles for DISNEY in PARIS..

 

They might be more efficient than tubes !

[paulears]

The calculation seems to be a bit pointless as they require information that isn't readily available. UV tubes and UV incandescent sources have different frequency responses, the paint, the material and liquids all have slightly different responses batch for batch - mainly due to concentration of the fluorescent elements. Old UV paint still works, but has less output - dirt and wear and tear reduce it more. Some like the see-through stuff get brighter when reapplied strengthening the effect. Dimming the fitting seems a little OTT when you could spend the money on more conventional fittings. If all you want is a smooth fade out, then running modern fittings from dimmer output works ok, and although you can't get a proper 'dim', you can get a quick fade out - staggering lots of fittings over 4 channels and doing a dim, dim, dim, dim with a slight delay works ok in my experience. Light level wise - just go for more and more tubes or cannons. I had some woods glass filter a few years ago, but with a 1.2K profile it wasn't that bright - and very delicate.

[musht]

Wildfire and Altman fresnels are metal halide discharge with added iron for more UV. Great for long range , but only dim with shutters and are very expensive.

 

Without decent UV materials even Wildfire will look weak. Get a UV LED money checker torch and take a wander around some party stores ;-) Flints do decent fluro dry pigments:

 

http://www.flints.co.uk/acatalog/Flints_On...owders_719.html

 

BTW Woods Glass is named after its developer Professor Robert W Wood, Modern Wizard of the Laboratory:

 

http://msp.rmit.edu.au/Article_04/06.html