# Candlepower To Lumens???

K

#### K3LAW

##### Guest
A lot of flashlight mfg,s give the candlepower of there lights. And still more give lumens. How do I convert candlepower to lumens?? Also if a light gives out 300 lumens, is this bright or not?? Looking for answers.

I don't think there is a real accurate way of comparing since they are different types of measurements, i do think that mfg's should supply all the information tho, otherwise it could be a little misleading. 300 lumens is extremely bright. i don't know if you have ever seen surefire lights, but most of their larger models LOLA is 225 lumens. The brightest light surefire currently produces is the dominator 10x, which is capable of just over 500 lumens.

Lumens = Total amount of light given out by bulb regardless of reflector, focus

Candlepower = Amount of light at any one point

Mean Spherical Candlepower (MSCP) = Lumens divide by 12.57. So 500 lumens = 39.7 MSCP. Alternatively, multiply MSCP by 12.57 to get lumens rating.

Lumens and candlepower can both be decieving. If your 300 lumens is in an extra wide focus this is totally unpractical for many situations that require a tight spot. However, if your 1 million candlepower spot light has most of the 1 million candlepower in the tiny central spot, you will not be able to see out to the sides at all.

Lumens and Candlepower are really two different ways to measure light brightness

To get an idea, of how bright a light is - a typical 100w light bulb puts out approx 800 lumens

A crude conversion can be made using the value 12.57 which is 4pi between Lumens and Candlepower

Lumens * 4pi -> Candlepower and inverse:

Candlepower / (4pi) -> Lumens

Mike
www.inretech.com

Most likely, the reason that most flashlight companies list their products in Candlepower, is that is the focused amount of light - and the number is Larger than Lumens - which sounds "more powerfull"

I once get some 13C LEDs from a company and the beam width was less than 1degree - the output pattern was a exact copy of the die, you would see a square on the wall with hole in the center - almost totally useless

Mike
www.inretech.com

Originally posted by INRETECH:
To get an idea, of how bright a light is - a typical 100w light bulb puts out approx 800 lumens

A crude conversion can be made using the value 12.57 which is 4pi between Lumens and Candlepower
<font size="2" face="Verdana, Arial">1) A typical 100W lamp is more like 1600 lumen.

2) The conversion between Lumen and Candlepower is _not possible_ without information on how the light is distributed. A 1 candela source which is 1 candela in _all_ directions puts out 4pi lumen, or 1 lumen evenly distributed is 1/4pi candela, _exactly_. But for any other distribution of light from the source, this conversion is wrong. For a really well focused source, the candela value _in the beam_ can be much higher than the lumen value.

3) If someone publishes data for 'mean spherical candlepower', then the conversion that Inretech posted is _exact_.

-Jon

Using either rating alone makes the spec almost useless. It's like when people market an air compressor based on PSI only, or a power supply on volts only. It would be really nice if the flashlight people got their collective act together, and published candlepower vs beam angle graphs, like nearly every company that makes PAR lights does.

My cynical brain says that the reason they don't do that, is that based on light output only, the little rayovac's and brinkmans would look pretty good compared to the streamlights and surefires. The last thing most manufacturers want you to do is compare products, they want you to buy based on brand loyalty and emotion.

Ok....whining done.

Now how about a conversion between lumens and candlepower for, say a 10 degree beam with the center twice as bright as the 10 degree edge? (My trig is way too rusty to try that one.)

There is no point trying to get the different manufacturers to come to an agreement.

An independant body should be used to rate beams. This would require a beam rating system and funding to put the flashlights through the testing.

Al