# 1 Million CP = How Many Lumens?



## Chris M. (May 1, 2002)

A question that has come up many times in many forms- and unfortunately there is no answer. Put simply, you can`t convert Candlepower (which is the same thing as Candelas or *cd*, *mcd* is millicandelas- 1000mcd = 1cd) to Lumens, they are two totally different measures.

This taken from SureFire`s FAQ page, explains it better than I could......

What is the difference between candlepower and lumens? 
Lumens is what is used to specify the total amount of light coming from any light producing device, and candlepower refers to the highest value of the light intensity to be found anywhere in the lights "beam".

Lumens tell you how "powerful" the light-producing device is, be it a light bulb of any type, a flashlight, or a car headlight. Candlepower tells you how tightly focused the beam is, assuming the light source has a lens or reflector to focus the light into a beam.

Lumens can be measured quite accurately, using an instrument called an integrating sphere, and identical lights would all have similar lumen values. It is an important quantity to know when comparing different lighting products, as it tells you how much light each one produces.

Candlepower can also be measured accurately, using a light intensity meter to measure luminous intensity, and then by applying the appropriate formula, which takes into account how far, the meter is from the light source. The problem is that the value measured depends on where in the beam you take the measurement (the highest value found is what is normally used), and on how well the beam is focused. It is not unusual for candlepower values to vary greatly from unit to unit on otherwise identical lights due to small differences in focusing or reflector tolerances.

Candlepower specifications (if accurate) are really only useful in comparing lights if the lumen values are also provided. If two lights had similar lumen values and one had a higher candlepower value, what it would mean is that light had a more tightly focused beam. This may or may not be an advantage depending on what the light is to be used for. Using candlepower values alone to compare the "power" of different lights, particularly those from different manufacturers, is likely to be at best misleading, particularly since there is a history of overstating actual candlepower values in the flashlight industry. For this reason Sure-Fire does not use candlepower to specify the performance of its lights, but instead uses accurately measured lumen values exclusively. Customers interested in selecting SureFire lights having higher light intensity values can do so by choosing models having larger reflectors, such as our turbo heads.


----------



## **DONOTDELETE** (May 1, 2002)

Chris,

A most succinct and appreciated answer. Thank you for taking the time and making the effort to respond to what is now obviously (to me anyway) a beaten-to-death subject.

Since according to Sure-Fire an accurate apples-to-apples comparison is best made using lumens, it is too bad not all light makers divulge this number. Because we could then simply compare two of the same-type lights using same-type power sources, say, focused spot beam of one maker to focused spot beam of another both using AAs (or wide flood to wide flood using 6-volt, etc.), and make our calculations from there.

Thanks again.


----------



## signals (May 1, 2002)

It's amazing how often you run across stuff like this. Crappy measurments to martket stereos, computers, cars, flashlights, you name it...

-Kevin


----------



## **DONOTDELETE** (May 1, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by signals:
*It's amazing how often you run across stuff like this. Crappy measurments to martket stereos, computers, cars, flashlights, you name it...

-Kevin*<HR></BLOCKQUOTE>

Yeah sadly, it's all about sales numbers. And the typical American consumer usually just chalks it up to experience if they buy a relatively inexpensive product that doesn't live up to expectations. Too much time and trouble in today's busy routines to return things. In fact, that makes me think -- ever wonder why they have mail-in rebates? Why not just redeem everything at the register when you pay? I think it's because a lotta folks don't follow through, or procrastinate till after the expiration date (I'm certainly guilty), and the companies make out.


----------



## **DONOTDELETE** (May 2, 2002)

I know this question is really oversimplified, but still being a newbie is my great excuse.

Seriously though, assuming all the light emitted from a device could be captured, is there some standard formula one could use? Or is there a formula to convert those other measurement units? What exactly is "mcd", anyway?

I plan on investing in an "economy" light meter, not necessarily to get an accurate/true reading, but just to compare my flashlights with one another.

Thanks in advance for any help.


----------



## pjenkins00 (May 2, 2002)

the only way you could really get an answer to this question would be to say "i've got a flashlight that measures blah blah blah candlepower and has a beam angle of 30 degrees, how many lumens is it?"

- Pete


----------



## signals (May 2, 2002)

Mr Bulk,

Not only do people forget to send in the rebate, but even if they do send it in, the company offering the rebate gets to use their money for 4-6 months while they process the rebate. That IMHO is why they do mail-in rebates instead of a sale at the store.

-Kevin


----------



## Chris M. (May 2, 2002)

_the only way you could really get an answer to this question would be to say "i've got a flashlight that measures blah blah blah candlepower and has a beam angle of 30 degrees, how many lumens is it?"_

Even this wouldn`t really work. A detailed analysis would have to be made on how the light is distributed over its entire beam, then a whole wadge of complicated mathematicallics applied. 
The only true way to obtain Lumen readings is to use an Ulbricht Sphere, often known as a Lab or Intergrating Sphere. These are very expensive even for the small ones, so could be one reason most flashlight companies don`t quote Lumen figures- cos it costs them a lot and they`ll sell more torches by faking a high candlepower reading to slap on the packaging.


----------



## BillSJCA (May 2, 2002)

Mr. Bulk,

Welcome to the forum of hard core LED where anything about LED's goes.





I better chill before I get cutoff!


----------



## **DONOTDELETE** (May 2, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by BillSJCA:
*Mr. Bulk,

Welcome to the forum of hard core LED where anything about LED's goes.





I better chill before I get cutoff!*<HR></BLOCKQUOTE>


Thank You!


----------

