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Old July 31st, 2009, 10:57 PM   #1
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Strobe lumens per watt?

I asked this as part of a thread in the Canon 5Dii forum but perhaps it is better asked here. How powerful per watt are DJ/disco strobe lights compared to tungsten? I mean, of course, for the moment that they flash in relative lumens to a tungsten light of the same wattage. It seems that strobe lights are an arc light like fluorescent and the like so they should me more efficient in lumens per watt than tungsten.
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Old August 1st, 2009, 09:44 AM   #2
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Yes they should be more efficient but since lumens per watt isn't a quoted spec on that, its not information that would be easily found. And there are several technologies these days for flashes so you'd need to specify which one to be sure as they're all likely different. Xenon strobes are one type for instance. Cree makes an LED though that can be used as a photographic flash and they claim a 74 lumens per watt for it. Some links I turned up in Google claimed about 40 LPW for common flash tubes.
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Old August 1st, 2009, 11:56 PM   #3
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Thanks, Richard! I think what I am seeing as affordable strobes are the xenon DJ effects models. They are very affordable and I think would make an interesting video with flashes of the artists and a continuous flow of properly-exposed fire with all its color and shape. I'm attaching an example of what things look like exposing for the people and not the fire and another example of what the fire looks like with proper exposure. With a flash, I could get a hybrid of the two with a bit of detail in the fire and a dim image of the artist, but never full detail in both.
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Strobe lumens per watt?-firejam.jpg   Strobe lumens per watt?-img_6306.jpg  

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Old August 2nd, 2009, 07:35 PM   #4
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Interesting. What you may encounter though are some color temp issues. Like the fire is super low color temp in the range of 2000 or so and the flash will be in the range of 5500K to 6500K. You may have to gel the flash to get it to look more natural like in the first picture.

Also you may get a "flash-like" look as well on the people which you may not like.

If you try it post pictures back so we can see how it turned out.
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Old August 3rd, 2009, 01:38 AM   #5
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Hi Marcus.............

I think there may be a possible pitfall looming here, or even two if shooting with a CMOS camera.

It all depends on the flash duration and flash repeat rate (flashes per second).

Most of the flashes I'm familiar with have such a short flash duration (1000ths of a second) that unless you were firing them at a tremendous rate (practically continuous, every field/ frame) the result could be, er, interesting, to say the least.

[If you're firing them every field/ frame, you might as well be using, er, lights?]

Of course, what that would do to a CMOS sensor is anyone's guess, but from reading the reports, total wipeout.

I could, of course, be totally wrong, but possibly worth investigating before parting with the readies.


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Old August 3rd, 2009, 04:53 PM   #6
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Richard, I put double full CTO on my photo flash and the color looks fine. Of course, that kills about a stop of light so I need something strong.

Chris, I thought about the short flash duration but I figured if I used a long shutter speed that it would expose the whole flash during that time just like if a regular flash was used for still images. Of course I wouldn't be using the flash every frame. That is not even possible. I just want the dancers to be lit and strobes seem like an effect that will mesh well with the subject. They are also very cheap for their strength bing only $50 for 750W that should be as bright as 1500W tungsten once I add gel. I can not easily run a 1500W tungsten at the location so this might be the way for me to get the light I need from an inverter/battery setup. The strobe won't need 750W continuously since it only fires periodically.

I'll probably have to try this out later as I am traveling soon and wouldn't get the strobe before I leave town. Perhaps I will be able to afford a fluorescent continuous light that can do the job by then...
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