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#1 Sean Azze

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Posted 15 October 2006 - 05:48 PM

Hey

I'm interested in using blacklight for a sequence in a music video and I want to know whats the farthest the lights can be until the effect no longer works? I have a scenario where a pair of guys drive up in a car (we shoot the car completely profile) and I want to capture this in a wide shot where we see the entire length of the car, the rapper sitting on the hood doing his thing, and his partner popping open the trunk and selling cds from the back.

We will be shooting this is in a soundstage so we will have a grid above us, but this is low budget so we don't exactly have the dough to shell out for personnel to help us rig all this stuff up. Also, in case this has any effect on the situation, the background will probably be lit with some spots ( we want to mix an orange background with the purple from the blacklights to make it appear as if it is dusk or dawn.)

Thanks for your time everybody.
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#2 Dominic Jones

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Posted 17 October 2006 - 12:47 PM

Well, it's much the same as any other coloured light - it's all about relative intensities. So, if your blacklight is registering at the upper end of your exposure scale then the effect will be strong, and as it drops from, say 3 stops over to 3 stops under you will see the effect decrease until, at around 2-3 stops under depending on what stock you're shooting on it starts to dissappear entirely.

Again, just like coloured light, if you hit the same subject with a lot of white light you will also wash out the effect of the blacklight.

As for how far it will travel from your source it will depend on the type of source - I have only ever seen blacklight produced from flourescent fixtures (I don't even know if it *can* be produced any other way - anyone?), and flouros are soft and therefore fall off in intesity pretty rapidly, so if you want to throw the light a long way you've basically got two options:

1) Find a harder source of blacklight - ideally something like a fresnel or par fixture that can concentrate the light into a tight area, thereby allowing you to throw it further. As previously mentioned, I don't know how plausible this option is.

2) Use more fixtures, although if you're wanting to light wides you'll probably need a *lot* of them...

There are a couple of other things you can do to help - firstly, keep all of the other light very low in intensity and shoot on a fast stock - as I said earlier, it's all about relative intensities, so if you can't get that much blacklight on the subject, reduce the other light to match it and expose for the blacklight. Of course, you'll still need a *reasonable* amount of light falling on the subject!

Secondly, you might be able to hide the lights behind something in frame, and thereby bring them closer - try talking to your art dept/props manager/whatever you have. Remember, when all else fails, cheat!!

Edited by Dominic Jones, 17 October 2006 - 12:49 PM.

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