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Black Light Question


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#1 Kip Kubin

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Posted 07 January 2010 - 12:53 AM

I'm DP'ing a video on RED and there is a scene using black light shining on a wall.

Has anyone shot black light on a Red anything I should watch out for?

The black lights are 400 watt UV Flood Stage lights rented from a stage supply and touring company in Nashville.

Does anyone know what the lighting = would be in terms of a tungston light

Does 400w = 400w in black light

Any thoughts and help would be appreciated

Thanks

Kip
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#2 John Sprung

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Posted 07 January 2010 - 02:13 AM

Fortunately with the Red, you'll see what you have during the shoot, so you can adjust to make things work. Go by your monitor and
histograms.

Black light is outside the visible and shootable part of the spectrum, it works by getting converted into the visible range by certain materials. That process is very inefficient, so it'll be a lot less light than you'd get from a visible 400 Watt unit. In those small areas, though, it'll be a light source in frame, sort of like distant Christmas lights or neon signs.





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#3 James Brown

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Posted 29 January 2010 - 09:42 AM

Hi,

I shot something recently with Blacklight (F35) and the amount of light you need or "exposure" is almost unfathomable (obviously i didn't realise this). A double 4ft Batton needed to be about 1/2 a foot away and the 400W stage lights we had were also quite limiting - direct at the talent from a couple of feet away.

Great for CU's - would hate to be doing a bunch of wide shots. Works really well with the white teeth and eyes - grab some fluoro paint and dabble it on things you want to pick out - but as John said - good its digital so you can actually see what you're working with.

Regards, James
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#4 JD Hartman

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Posted 29 January 2010 - 12:10 PM

400w doesn't really equate to anything, it's the power consummation of the fixture. What you want to look at is the photo metrics of the fixture. It will tell you how many lumens you'll have, at "x" distance. What's the beam shape and spread? How large of any area are you trying to light? You should be relying on your Gaffer to get you the look you want and the exposure your camera needs.
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#5 David Rakoczy

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Posted 29 January 2010 - 12:17 PM

Exactly... a photometrics chart is what you need.
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#6 John Sprung

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Posted 29 January 2010 - 01:41 PM

A photometrics chart will tell you how much UV you're getting onto the phosphors. But the phosphors are a wild card, the next step in the process. You'd have to know how efficiently they convert UV to visible. With enough UV, you can saturate some phosphors. More UV won't get you any more visible light beyond that point. In fact, most flourescent lights are designed to operate a little beyond phosphor saturation, so you get a constant output.

Anyhow, this is all too complicated. The thing to do is simplify it by using the camera's histograms and the monitor.




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#7 David Rakoczy

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Posted 29 January 2010 - 02:06 PM

Geez you are right.. I was too fast to reply... when shooting Film, you'd would have to go with your Spot Meter. I remember doing it that way the one time we incorporated black light.
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