How many lumens is 30 million candlewatts?

Title says it all

 

42.

 

My previous answer ("42") was an approximation assuming proper
measurement. If you are looking for an exact measure, we need more
information. How was the 30,000,000 candlewatts measured? You really need
to use a fimble damper and a mass-transit (NOT a weight-transit!) to get
an accurate reading, otherwise the Kempfthorne Effect tends to grossly
distort your readings and you'll get a garbage answer.

What's the nature of your project, that you're measuring in candlewatts
rather than the more commonly used Amplumens or Ouncelamberts?

DS

 

Candlewatts are not a unit of anything. Do you perhaps mean
candlepower? But then again, even candlepower is not a unit of light
but rather the luminous intensity of a light source in a given
direction, where the units are usually given in candelas.

If, and only if, your light source had a mean spherical candlepower of
30 million candela, then it would produce 4 PI times 30 million or 377
million lumens. If you do not know the mean spherical candlepower,
then you would need the candlepower distribution in each individual
direction in order to compute the output in lumens.

 

I didn't think there was a candlewatt but that's what the person said.
He's a helicopter pilot and said the search light on his helicopter is
30 million candlewatt.

 

http://web5.andrew.cmu.edu/~bpantano/GIFS/explodinghead.gif

 

I asked him the lumens and he told me candlewatts.. I guess I was just
wondering how much light it puts out compared to a normal 100w bulb for
instance.

 

I suspect this could be candlepower or more properly candela. Maybe it
does not achieve 30 million candela so possibly it is "rated" with some
"less scientific" form of "candlepower".

If you have a candela figure, see if you can determine the beam coverage
in steradians. (As an approximation: Determine the beam diameter in
degrees, square this figure, and divide by 4179.8. Determine the beam
width at distances far enough for this figure to not vary
significantly with distance. For a larger, narrower beam spotlight you
may need at least a few hundred meters of distance to determine the beam
width.) Divide the candela figure by the steradian figure to get (*very
approximately*!) the light output in lumens. This is only roughly, since
the beam is probably not uniform, its edges may be diffuse, the candela
figure may not be honest and some light may be found outside the beam, and
this 4179.8 "circular degrees per steradian" figure only applies for
narrow beams and then never exactly.
For comparison: A "standard" 100 watt lightbulb produces typically 1710
lumens, and the amount of "visible light" (400 to 700 nanometer range) is
approx. 6.7 watts. Also note that visible light does not always have the
same number of lumens per watt of light - the maximum is about 683, for
yellowish green monochromatic light of a wavelength of 555 nanometers.
The minimum is approaching zero, for visible wavelengths that are
borderline ultraviolet or borderline infrared.

- Don Klipstein ()

 

Thank you, Deep Thought

Jeff Waymouth

 

Guessing 1300W short arc xenon giving 30million candlepower peak beam,
helicopter gives clue
Spectrolabs Nightsun:

http://www.spectrolab.com/prd/ils/sl-main.htm

HTH
Adam

 

Short arc xenon lamps of wattage near this have a luminous efficacy
around 40 lumens per watt. This means a 1300 W one would produce
somewhere around 52,000 lumens. 1600 watt ones produce 60,000 lumens.
Not all of this will be formed into a beam by the reflector.

- Don Klipstein ()

 

Only those used on 1960-1970 Ford Populars.