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Old February 11th, 2008, 09:03 PM   #1
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Watt Equivalent of Fluorescent Tubes

I have some 32w T8, 4-foot tubes. The ACTUAL wattage drawn is 32w, but what is the tungsten equivalent wattage? (I.e. light/lumen output).
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Old February 12th, 2008, 08:49 AM   #2
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Usually about 4x. So a 32w tube puts off about the same as a 120w tungsten.

~~Dave
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Old February 12th, 2008, 11:11 AM   #3
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If you get into comparisons between fluorescent and tungsten, it's not completely simple. On lots of the sites selling fluorescents for production, you'll see comments such as, "Same output as a 500 watt tungsten light."

True, sort of.

A fluorescent light is always a softlight, and if you're going to compare its output in the real world, you have to compare to the equivalent 500 watt tungsten light gelled down or in a softbox to give the same type of light as the fluorescent. A 500 watt hard light is going to put out a lot more light at a longer distance than a fluorescent. So if you have, say, a Lowel DP with a 500 watt bulb, pop on some Lee 251 or stick it in a softbox and check to see how it looks, and that will be reasonably close to what you'd get with something like a 2-bulb Caselight.

I'm not knocking fluorescents--I love 'em, and I also have some 500LED lights from Flolights that I like even better. But when you use these types of lights, it's a good idea to start thinking in fluorescent or LED terms and not trying to translate into hard light terms. Easier said than done...even though I've had the LEDs for awhile I still translate their output into what Caselights give me.
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Old February 13th, 2008, 02:46 PM   #4
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I see your point. Thanks for the clarification. I'll just use the 4:1 ratio as a loose general rule mentioned above, but keeping in mind it's not that cut and dry.
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Old February 13th, 2008, 08:54 PM   #5
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also in those ratings is consideration of a good shiny reflector which helps boost output. that said, I have a 40w 2X24" fixture that puts out a light level similar a 500W DP in a chimera using the inner diffuser when used close - say 5ft. thats a 12X equivalent "by the numbers" so take it all with due care. they should rate the lights in lumens, lux, or footcandles at 2,5,10,15,20ft and area of coverage as the most fair comparison. something you will find on arri and mole's websites.

I do plan to phase out almost all my tungsten lights for flo, HMI, and CID.
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Old February 14th, 2008, 03:09 PM   #6
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Some info on lumens output of the T8 lights...

http://www.sylvania.com/content/disp...x?id=003682607

Hope it helps you some,

Mark
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Old February 17th, 2008, 12:42 PM   #7
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Watts for lumens conversion.

The average 100W lightbulb puts out 1800 lumens.

So, take whatever lumens they are rated, divide by roughly 2000, and there you go.

A 10k lumen light is roughly a 500w tungsten equivalent.

Look at your lumens. That's it. That's the only true measure.
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Old February 17th, 2008, 10:18 PM   #8
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Originally Posted by Alex Lucas View Post
The average 100W lightbulb puts out 1800 lumens.

So, take whatever lumens they are rated, divide by roughly 2000, and there you go.

A 10k lumen light is roughly a 500w tungsten equivalent.

Look at your lumens. That's it. That's the only true measure.
Lumens are the measure at the light bulb level for the general lighting world of fixtures for commercial and residential use, but photometrics are often considered more useful in the photographic / film /video world and those are measured in foot candles or lux.

Also, in the above case, you'd divide by 20 not 2000. And why? Because Tungsten is roughly in the range of 20 lumens per watt (LPW)--but that's the best tungsten. Average tungsten could actually be 10 to 15 LPW and is very common to find that. At 10 LPW, average tungsten doesn't make much more than an efficient heat element because of its super infrared output capability.

Ballast-oriented discharge lighting gives you a better leverage in energy usage and has far less infrared component. Fluorescent is in the range of 40 to 60 LPW. HMI/metal halide is in the range of 85 to 100 LPW. LEDs are in the range of 30 to 50 LPW with some in the laboratory that go as high as 120 LPW (but those are far from commercialization).

If the average fluorescent bulb is in the 40 lumen per watt range then when they say they are comparing 4 to 1 to tungsten they are comparing to average 10LPW tungsten.
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Old February 18th, 2008, 08:08 AM   #9
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Richard, what about the leds in a focused case. I've been using 3-1watt cree leds that are in a single mr-16 case. The spread is about 40 to 50 degrees. Is the brightness effected by the tighter beam?
Gary
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Old February 19th, 2008, 05:19 AM   #10
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Gary,

The brightness is affected of course but IMHO, it doesn't make as efficient a point light source as something like a single high intensity tungsten bulb or metal halide. The source is still pretty small in what you've got, but the source is even more small and concentrated in the tungsten / metal halide type. Why is that important? Well, it helps with compactness for instance. And in any case, the smaller and more intense the source, the harder the light will be for those times we want hard light and projection.

To build an LED fresnel of the same intensity as a 575w HMI, you'd need a lot of those CREE type LEDs. How many I'm not totally sure because I don't have all the lumen figures on what you've got but you can do the math if you know that the 575w HMI puts out about 49,000 lumens. The CREE array will probably be huge and will therefore not be a compact source, but much broader and therefore while its certainly not a softlight to compete with a fluorescent, its not a totally hard light like the 575w HMI either. It's something in between with its own properties. For now, I think trying to make an LED unit to compete with a 575w HMI or 1200w for that matter would not be all that practical. LEDs "shine" in small compact on-camera fixtures or small panels that find uses in places where you might use a nook light.
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Old February 19th, 2008, 07:52 AM   #11
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Richard, I've included (attached) 2 versions that I use. The 5 led I keep in my camera bag and the 11 led I use to support my main lighting package. You can switch on either 1 or all 5 leds on the 5 and you can switch on 5 or all 11 leds on the 11.
According to cree, each led puts out 50 lumens, that would be 150 per mr-16 and 1650 for all 11, probably equivilent to a 100 watt bulb.
The strange thing is that output is pretty strong and beam width is somewhere between a tungston and a fluorescent. The power is quite remarkable. I have used the smaller version (in a pinch) in a restaurant to shoot a German Band. At 15 or 20 feet is was strong enough to change the white balance to daylight. Is it possible that the camera sees much more led output than we do?
Gary
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Old February 19th, 2008, 09:49 AM   #12
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Originally Posted by Gary Moses View Post
Is it possible that the camera sees much more led output than we do?
Gary
Absolutely. White LEDs are manufactured from NUV (near-UV) emitting LEDs, usually with some rare earth elements to produce a "lunar white." Film and video are much more sensitive to UV light than the human eyes are.
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Old February 19th, 2008, 10:31 AM   #13
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Recently I bought three of these http://www.flolight.com/500LED.htm and it is true that the focus is somewhere between a fresnel and a fluorescent. They have just a bit more throw than the equivalent fluorescent, and the beam is tighter. Because of that I have to use diffusion gel when the lights are in close, as when shooting an interview. With fluorescents, they're soft enough so no diffusion is needed under the same conditions. So in a way that's a disadvantage, but it's also an advantage in that you have a harder light when needed. They are, however, in no way comparable to an HMI in terms of focus or throw. Equivalent fluorescents also have a much broader spread. My understanding is that there are currently three types of LEDs--spot, medium and broad. These lights, according to the distributor, are of the medium LED variety. It would be interesting to see what the full spot ones would do.
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Old February 19th, 2008, 12:00 PM   #14
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Wow Bill, those lights would have to put out about 10,000 lumens to be equivalent to 500 watts. They must have quite a recoil when you turn them on! Did you pay $450 each? I have tried many types and styles of LEDS but I'm not sure I love them that much LOL. By the way, LEDS can come in 15 degree, 30 degree, 60 degree and 120 degree. I have found the 50 ro 60 is pretty good for 10 to 20 feet. If I need to get closer I turn off lights or diffuse.
I never have tried to compare them to HMI's, I really don't ever have a need for that kind of lighting.


Hey Ben, that would explain my results then.
Gary
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Old February 19th, 2008, 12:51 PM   #15
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Yep, $450 each. They were originally $400 but they converted to DC and raised the price 50 bucks. Since these are "medium" I guess that would make the LEDs 60 degrees.

I've used daylight fluorescents with HMIs quite a bit but haven't done a shoot mixing these with HMIs. So far I'm happy with them. They don't replace quartz lights or HMIs (although they have replaced fluorescents for me)...just another tool. I don't think they're necessarily any better than fluorescents, just different. In my case their compactness and lighter weight makes them nicer than the fluorescents I used in the past for location interviews.
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