1. ## Lumens to Candlepower?

Hey I need help on the lumen to candlepower conversion process! How i understand it is that 1 lumen is worth 12 candles. In that case the P61 bulb (120 lumens) is 1440candlepower. right?

Please let me know if I right!

2. ## Re: Lumens to Candlepower?

Nope.

You can not convert lumens to candlepower or candlepower to lumens. They measure different things. It is like converting volume to weight.

Lumens measures the total light output, while candlepower measures only how intense the hotspot of a beam is.

3. ## Re: Lumens to Candlepower?

So why do some companies rate their light in lumens(surefire) and others in candlepower(streamlight)?

4. ## Re: Lumens to Candlepower?

those who are mainly concerned with throw of a light are competing in a mostly hyped candlepower based arena while those seeking overal output and lights possibly favoring a more flood type output lumens is more suited and overall more accurate.

wrong post

6. ## Re: Lumens to Candlepower?

I too heard that 12 candle powers is 1 lumen.

7. ## Re: Lumens to Candlepower?

12 lumens = 1 candle is sort of kind of correct, IF, and it is a big IF, you are talking about an isotropic radiator, ie a black body. The definition of a candle is 1 lumen per steradian. A Steradian is the solid angle subtended by the surface area of a sphere equal to r^2, since the total area of the sphere is 4 pi r^2, a 1 candle output would required 4 pi lumens, or about 12.56 lumens.

If you aren't dealing with an isotropic radiator, but instead a well designed reflector, that same 12 lumens might be concentrated into a far smaller area. For example if you were to use a reflector that took that 12.56 lumens and focused it into a beam that is only a couple of degrees wide, the brightness if you were looking straight into the beam would be about 10,000 candles ! HOwever if you weren't looking straight into the beam, it might well be ZERO candles .

Lumens tells you about the actual output, Candle power tells what the beam looks like in the center and the equivalent Isotropic radiation that would be needed to produce it, it tells you very little about actual power output unless the beam width is actually specified. Very bluntly Surfire has the actual lumen output, and don't mind bragging about it. If you don't have it, you don't brag about it.

In radio and TV, there are two ways to describe ouput. There is real power, measured in watts. If I tell you I am putting out 100,000 watts, it means I am putting out 100,000 watts in total. It says nothing about how I am directing the power. If I tell you I have an Effective radiated power of 100,000 watts, it is 100,000 watts if you happen to be staring straight into the antenna. If the beam width is narrow enough, it might only be a few hundred watts of power, and if I am well off the main lobe, it may look to me like Zero. As a University Student, we had a small search radar. 60 watts RMS. 60,000 Kilowatt peak output, and an effective radiated power in the beam of about 2 million watts (for 1 microsecond per millisecond).

Would I worry about being only 100 yards away from a 2 million watt RMS power transmitter? You bet I would. In fact i probably would be cooked long before I could tell anyone about it!

Would I worry about being 100 yards away from a 2 million watt ERP transmitter?
As long as the beam wasn't pointed at me, probably not.

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