Comparing lumens and candlepower?

I'm shopping for a good flashlight, but I can't figure out the difference between lumens and candlepower. Since the ones I'm looking at have only one or the other, it's really hard to compare. If you could help, it would be much appreciated.

[thesmartfisherman.com]

It is virtually impossible to compare. Candlepower is an archaic measurement that is not standardized.

If you want flashlight help im me with its intended use and I may be able to help you out.

Hello Matt,

If you've already received the information you needed from thesmartfisherman, then ignore the rest of this post.

Otherwise, here's the short (but somewhat deceptive) answer: 1 candlepower = 12.57 lumens. But in order to interpret that statement, you need to understand that candlepower and lumens do not actually measure the same thing.

Candlepower is most useful as a measure of illumination in a particular direction, while lumens are most useful as a measure of total illumination. The conversion above is saying that a light source shining with 1 candlepower in all directions would produce 12.57 lumens.

Imagine you're in a dark room with just a thin beam of sunlight shining through a tiny opening between heavy curtains. That beam represents high candlepower, but modest lumens. You wouldn't want to look straight into the direction it's coming from, even though the sunbeam doesn't brighten the whole room much. On the other hand, a table lamp could brighten the room much more than that sunbeam, even though it's not nearly as bright as the sun when you look directly at it. That lamp represents high lumens, but modest candlepower. See the difference?

If you'd like to know more, have a look at this article, "Measuring Light Intensity":
http://www.energybooks.com/pdf/D1150.pdf

Oh, and if you're mathematically inclined, the origin of the factor 12.57 is simple--it's actually just 4*pi. That's also the basis for the number 8% in the "Candlepower" section of the article I cited, because 1/12.57 = 8%.

Thanks for the link, it was very helpful information.

I need a 1 million candle power searchlight/spotlight. I have been slowly following the progress of LED torches as they get brighter and brighter. Any ideas on how many lumens a (multi bulb) LED torch would need to kick out the same power spotlight if say 75% of it's light actually went to the spot?
Thanks
Dave

i have a 2mil candle power q-beam and i seen an led q-beam with 530 lumens. is the led close to the same as the 2mil?

I have a 10,000,000 candle power super search light. And it's amazing for spotting far off objects such as deer chupacabras etc.. But it's not so great for just lighting a wide area close up with intense clarity.

I am looking at basically two of the sme type of lights. They are the remote contolled spots that has magnetic mount to put on top of truck cab. One says 500,000 candle power, the other says 4400 lumens. Which is the best as far as light goes. Thanks

[JohnS]

Originally Posted by Unregistered

I am looking at basically two of the sme type of lights. They are the remote contolled spots that has magnetic mount to put on top of truck cab. One says 500,000 candle power, the other says 4400 lumens. Which is the best as far as light goes. Thanks

There is no way to answer without knowing the beam angle, or the spot size at some distance. Each gives you half the answer.

For a lightbulb that radiates in all directions 1 cd (candlepower) emits 12.57 lumens (4*pi) because that is the solid angle of a complete sphere). For a light that emits a moderately small angle of light, any type of spotlight or flashlight, you need the solid angle to relate the two units.

Candle power (properly called candela) measures the brightest part of the beam. Lumens integrate the candlepower at each angle and give the total light emitted. If you are trying to light up a room, lumens are what counts. If you are trying to throw light a long way, and small spot size or beam angle is acceptable, candlepower is what counts.

[QUOTE=Unregistered;70513]conversion of 10,000,000,00 candle light power vs. lumens?