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Black Lights on Film?


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#1 Camera

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Posted 29 September 2009 - 06:36 PM

I'm shooting a party sequence this weekend and my art director has purchased black lights for our actors to hold in the shot. Unfortunately, I don't have the time or budget to shoot camera tests to see the effects of black lights.

I'm curious to know if anyone has experience shooting with black lights; how do they read on film, how do they meter, do I need to worry about flicker, etc...

I know I could use regular fluorescent bulbs gelled with lavender to mimic the look of black lights, but since these bulbs have been purchased I would like to use them.

Helps for all the help in advance!
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#2 K Borowski

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Posted 29 September 2009 - 07:10 PM

If you want the "black light effect" to show up, I'd say that tungsten stock is going to be a bad choice, as it is balanced towards the warm end of the spectrum.

As UV light is cooler than blue and the effect of the "black" lights on white objects is to make them seem to be a glowing blue, you'll really have to overexpose the tungsten stock to get this effect to show up.

I've photographed black lights only once and, unless you have a whole lot of them, it'll be incredibly difficult to get them to show up unless you are shooting wide open.

Unless you want shots to come out without any trace of black light effects, I'd highly recommend against even using them unless you do some sort of test. That sounds like a nightmare of color temperature mis-matches and exposure balancing challenge.


What are your primary light sources? Please tell me you aren't using tungsten. . .
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#3 Camera

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Posted 29 September 2009 - 08:31 PM

If you want the "black light effect" to show up, I'd say that tungsten stock is going to be a bad choice, as it is balanced towards the warm end of the spectrum.

As UV light is cooler than blue and the effect of the "black" lights on white objects is to make them seem to be a glowing blue, you'll really have to overexpose the tungsten stock to get this effect to show up.

I've photographed black lights only once and, unless you have a whole lot of them, it'll be incredibly difficult to get them to show up unless you are shooting wide open.

Unless you want shots to come out without any trace of black light effects, I'd highly recommend against even using them unless you do some sort of test. That sounds like a nightmare of color temperature mis-matches and exposure balancing challenge.


What are your primary light sources? Please tell me you aren't using tungsten. . .



Thank you for your response. You brought up a lot of concerns that I didn't take in to account. I'm not lighting the scene with black lights, yet using them as props for the actors to interact with.

My question now is if I use HMIs to light the scene for tungsten balanced film without any form of correction will that help me achieve what I'm after?

And as far as exposure, will black lights not read around a 2/2.8?
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#4 K Borowski

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Posted 29 September 2009 - 09:19 PM

Thank you for your response. You brought up a lot of concerns that I didn't take in to account. I'm not lighting the scene with black lights, yet using them as props for the actors to interact with.

My question now is if I use HMIs to light the scene for tungsten balanced film without any form of correction will that help me achieve what I'm after?

And as far as exposure, will black lights not read around a 2/2.8?


I definitely think HMI is the way to go.

As for exposure, yes, I would count on shooting as wide-open as you can. The stop you are able to light to depends on the size of your set and the power of the lights.

You may have flicker issues too. What sorts of compact black lights are you using, some sort of CFL tubes? There really isn't anyway to cheat with that. You'd almost need to buy special black lights.

The trick to making this work, again assuming you want to get the "black light effect" is to keep practical lighting down as low as possible so as not to "overpower" the weaker black lights.

This may, honestly be better to do by having the black lights "motivated" by supplemental blue-gelled set lights aimed at any white objects.
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#5 Gustavo Brum

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Posted 30 September 2009 - 12:33 AM

I have done a shoot where I mixed the black lights with Kinos (the kinos had the blue globe used for blue screen) and 1200 Hmi's with Congo blue gels...
But remember you need a lot of UV/Black lights to get a decent exposure...
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#6 Serge Teulon

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Posted 30 September 2009 - 05:31 AM

Hi Cait,

You can always use a digital stills camera with the settings you require to do your colour test.
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#7 Phil Rhodes

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Posted 30 September 2009 - 05:43 AM

Hi,

I've shot quite a bit of video under UV light and it is a challenge - some camera/lens combos react strangely to UV light - some see it, some don't, some flare oddly. Some of these issues may affect you on film, too.

Things don't have to glow blue. Paint it fluorescent orange and it'll glow orange. Yellows and reds are also available and would glow in a range favourable to your tungsten-balanced film stock, though the residual deep indigo visible output of most UV-emitting tubes would probably be difficult to reproduce if you want it to actually look like what it is when viewed directly. The only thing that glows blue is any UV-active white, and fluorescent blue.

Consider backing up your exposure with full sized, mercury vapour based UV emitting lights. They're usually in the 400W sort of range, and have a truly enormous output. The other option is to use HMIs with deep blue filtering, which have extremely similar effects to UV lights but also create a particularly beautiful deep blue visible light as well. When I last did this, we got all our UV gear from a stage and event lighting company and rented some Studio Due CityColors, which are really designed for architectural work but provide full RGB colour mixing and are capable of extremely saturated deep blue output.

Hope this helps,

P
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#8 boy yniguez

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Posted 01 October 2009 - 08:46 AM

I'm shooting a party sequence this weekend and my art director has purchased black lights for our actors to hold in the shot. Unfortunately, I don't have the time or budget to shoot camera tests to see the effects of black lights.

I'm curious to know if anyone has experience shooting with black lights; how do they read on film, how do they meter, do I need to worry about flicker, etc...

I know I could use regular fluorescent bulbs gelled with lavender to mimic the look of black lights, but since these bulbs have been purchased I would like to use them.

Helps for all the help in advance!



wikipedia defines ultraviolet light as: "Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.

UV light is found in sunlight and is emitted by electric arcs and specialized lights such as black lights. As an ionizing radiation it can cause chemical reactions, and causes many substances to glow or fluoresce. Most people are aware of the effects of UV through the painful condition of sunburn, but the UV spectrum has many other effects, both beneficial and damaging, on human health."

the key phrases here are:
1. shorter than that of visible light - it just means UV light hitting an object won't make it more visible to us no matter how much you pour in!
2. causes many substances to glow or fluoresce - for objects to be visible to the human eyes they have to be coated with fluorescent paint such as day-glo paint

so your characters can be waving blacklights around but as long as there are no objects painted in day-glo, about the only things that will glow will be certain white textiles and dentures!
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#9 K Borowski

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Posted 01 October 2009 - 11:22 AM

As an ionizing radiation it can cause chemical reactions, and causes many substances to glow or fluoresce.


Most whites will fluoresce under UV light, and that is the effect that Cait appears to be trying to pick up on film.

And, since film is naturally sensitive to the UV end of the spectrum, it is possible to pick up the actual wavelengths as blue light on film, just as it is possible to pick up IR images on digital sensors, as they are natively IR sensitive.
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Aerial Filmworks

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The Slider

Abel Cine

Broadcast Solutions Inc

Paralinx LLC

Wooden Camera

Rig Wheels Passport

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