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Old February 25th, 2007, 08:10 AM   #1
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Fluorescent Lighting Theory Questions

I'm looking to move over to a reasonably low budget fluorescent lighting kit - mostly to avoid the hassle of having to gel every light in mixed light environment interviews, and more importantly to stop the talent wilting in the (barely ventilated) chromakey studio space that I have access to.

I've just purchased a couple of these: http://cgi.ebay.co.uk/Triple-Dayligh...QQcmdZViewItem - and I am getting one of these: http://www.profilmgear.co.uk/00144_a...ALI-13058.html.

The first two heads came with 5000K lamps with (very) noisy ballasts. The third has 5400K lamps.

Now, there seems to be plenty of choice when it comes to finding reasonably well rated, high CRI 5500K(ish) tubes for the third lamp. But over here in the UK I'm having difficulty finding anyone who carries well spec'd 220/240V 30W CFLs at anything in between the 4200K and 6500K colour temperatures.

My questions:
1. Is the difference between 5000K and 5400K a problem?

2. Does anyone know of any sources for colour balanced, European voltage CFLs that run at around 5500K?

3. If 5500K CFLs are not available in 220/240V, would you run at 4200K or 6500K?

4. And can you run a 85 Watt CFL in a fitting rated for a 100 Watt tungsten?

Thanks.
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Old February 25th, 2007, 10:22 AM   #2
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1. You will need to check your lights in front of the camera. Manufacturers don't all seem to rate the color the same way.

3. Only if I was planning to use gels.

4. If it will physically support the lamp, it should be fine. The wattage rating is based on heat and fluorescent lights don't heat up much as long as they have ventilation. Actually, they can not be allowed to get hot or they will burn out. An 85w fluorescent is so spread out that it can't overheat a vented fixture and as long as you stay under the actual wattage rating you won't overload the wires.
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Old February 26th, 2007, 05:20 AM   #3
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Thanks Marcus,

I checked the light temperature and it seems to be okay. In fact it looks hideous to the naked eye, but it looks alright on screen(!).

Although it was a little hard to tell, thanks to the fact that the guy who owns the studio space (who knows not a lot about video) had invested in "cool white" 4200K tubes for lighting the chromakey curtain - because the electrical retailer said "they were very good for skintones" (yes don't ask... I had specifically told him to get 5500K and ONLY 5500K with a CRI of 85 or higher).
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Old February 26th, 2007, 05:52 AM   #4
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If you are lighting a greenscreen, 4200Kelvin should be just fine. You shouldn't be lighting the screen with the same lights as the talent or you will get shadows. If you want a shadow, it should be from the key light. Don't worry about the temperature of your greenscreen lights. In fact, you could put green gel on them so they don't illuminate anything but the greenscreen. If you are using a bluescreen, higher color temperature is good as it will have more blue and be more efficient.

If you are always going to be shooting in a studio environment, you can select any color of light and standardize on that. Of course, that doesn't help when you go out in the wild. I think it's best to go to 5500Kelvin as it is more efficient to gel down than up and you really need a lot of lumens if sunlight is mixing in your scene. 4200Kelvin might look okay if you have sunlight in your shot as it will make things look a bit warm without being completely yellow-looking like tungsten. Still, it's better to start with a match to your typical scenario.
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Old February 26th, 2007, 06:50 AM   #5
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4200K is about as unflattering to the eye as anything but it should white balance fine as long as you're consistent. Like Marcus said, the foreground and background can be different color temps. Only need for consistency is all same color temp on foreground and all same color temp on background. Actually as negatively as we think of 4200K, its a common temp sold in studio lights in some parts of the world--like China for instance.
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