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Black (UV) Lights?


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#1 Rhys Cooper

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Posted 08 April 2009 - 06:03 AM

I saw that Robert Rodriguez used Blacklights to enhance and brighten certain glowing materials in Sin City, so he could later composite those colors and edit them to become whatever color he wants, or key them out and replace them with digital effects.

How can one use blacklights properly (how close to glowing material)? Do they need to be strong (I have a fluorescent bulb and an incandescent)? If so, where could I buy strong bulbs? How can I use them in combination with other lights? Can they work with a Canon XL1?

Thanks
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#2 Karel Bata

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Posted 08 April 2009 - 06:42 AM

Been a while since I did this myself, and that was on film, which is more sensitive to the blue end of the spectrum. I used a Wratten 2E on the lens to filter out the UV itself (it won't focus well). An alternative may be a B+W415.

Though it may look bright in a nightclub, the light that UV lighting 'creates' via fluorescence in clothing etc. is actually quite low in intensity and you may have to pour in bucket loads. So BE AWARE that over a prolonged period, and depending on the lamp type, this may give your actors sunburnt eyeballs if they look directly into the lights. It was a problem when they first used carbon arcs! I was using UV lamps intended for stage use (like meant for at least 10ft away) and we all had sore eyeballs after a couple of hours. Be careful.

The pupils of your actor's eyes (and yours) will fully dilate, and a lot of UV will get to the retina (and slowly burn that too!). It will deplete your visual pigments without you actually knowing what is going on, and your vision will be a bit weird when the lights come back on. It is fatiguing. Also, the surface of your corneas will fluoresce mildly and this can get uncomfortable after a while. You may think this sounds nuts, but I'd recommend the crew wear orange tinted glasses. And cast too, until the camera rolls. There may well be Health and Safety regs on this that are worth looking up.

Certain chemicals cause the UV light to be changed to visible light. We have some of these chemicals in our eyes and teeth, but in particular, washing powder manufacturers put it in their products to make 'whites' look brighter. So newly laundered shirts will fluoresce, but you may have to experiment to find the best powder. The 'whiter than white' kind sound like a good candidate.

Check my Krop link below to see an actress with UV make-up on for a test. We abandoned that idea pretty quickly! The big B+W pic is with UV lighting too. That was a long exposure. His skin fluoresced slightly, and his pupils had a weird milky glow! We only had the light on for a few minutes.
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#3 Jamie Metzger

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Posted 08 April 2009 - 12:59 PM

dont know if you want to have them in the frame or not, or use UV active materials; but here is a link to a video we shot recently that has both:
http://www.old.etypi...Radiator_large/

Everyone on CML said to trust your eyes, in regards to exposure for UV reflective tape, and they were right. The grid on the floor was UV tape, and we had 3 400w Blacklights...can't remember the name of them.
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#4 Martin Solvang

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Posted 21 April 2009 - 02:15 PM

Hey,
I shot a short some months ago using UV-lights (fluorecents).
I shot on B&W film, Kodak Plus-X 64ASA, in combination with HMIs and Tungsten.
My experience was that the UVlight was hard to measure. I metered it both reflected and directly, and it
gave me some weird readings.
When I tried to photograph the light with a digital SLR it didnĀ“t have an effect at all... I found out that most CMOS and CCD sensors have
UV-coating and that no visible (to the sensor) UV-light passes through.
I then went back to my old Contax and re-shot everything and finally got the results I needed to go through with the film.

Measuring with a spot meter was the closest thing I got to knowing where the exposure was, but in the end trusting my eye was
even more successful.

Considering the Canon has ccd-sensors I would at least do tests.
When looking at the spectral sensitivity of the sensor compared to the UV-lights I used on my project (different UV-lights produce
wavelenghts in different parts of the spectrum..) I would say your in
an uncertain zone...spectraly speaking...LOL

http://www.ph.tn.tud...p-Spectral.html

Good luck.
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#5 Karel Bata

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Posted 22 April 2009 - 04:17 AM

Interesting how much sensitivity there is at the IR end. If it were a simple matter to remove the internal IR filter we'd have night-vision cameras! I'm not sure why that option isn't more readily available. it would make a good selling point, and could be really useful. But then, would it focus..?

Any chance of seeing what you guys have shot? :)
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Technodolly

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Rig Wheels Passport

FJS International, LLC

Metropolis Post

Abel Cine

Ritter Battery

Media Blackout - Custom Cables and AKS

Tai Audio

The Slider