Candle Power vs Lumens, whats the difference?

[V8TOYTRUCK]

I was reading that my Ultrastinger has 75k candle power, then I find out its not the brightest flashlight out there. The M6 by SureFire is 250-500 Lumens. Since the M6 is almost triple to cost of the Ultrastinger, and doesnt have recharagable batteries. I think I would still perfer my Ultrastinger. So the question is, is there a fomula to figure out CP vs Lumens? Like 100 Cp = 1 Lumen?

 

[Chris M.]

It`s not as simple as that. Candlepower is a measure of the peak beam intensity- the intensity at the very brightest spot, whereas Lumens, put simply, is a measure of the total radiated light output in all directions. A 100 lumen lamp could put out a 100 candlepower beam or a 100 000 candlepower beam depending on how tightly focussed it is. Take a cheap laser pointer for example. It shines for miles and would blind you if you stared straight at it- but you couldn`t use one to light a whole room bounced off the celing cos the total light (lumens) is so low.

Candlepower is a figure that manufacturers like to use because the figures are often really high and it looks good to say "half a million candepower" than it does to say, for example, 300 lumens. But on their own, they are not a good figure as in one case, a really high candlepower light could have a beam so narrow it is simply not practical. Similarly, lumens on their own don`t mean too much in a flashlight cos a 100 lumen flashlight will not necessarily shine as far as a 60 lumen one if it has a really wide beam in comparison.
For a fairer representation we need to know other things like the beam half-angle (the angle from the centre of the beam to the point where it is 50% of the peak brightness) or even, actual beam-profile shots at standard distances like me and Craig do with our test victims, er, subjects- they show the peripheral rings and spill light as well as the size and shape of the hotspot to give a better impression of the useability.


Confused? I think I am a bit too now.

 

[Size15's]

I like to think of Lumens as the total amount of light the beam contains whereas Beam Candlepower is more a measure of how bright the beam is at a given point.

The difference I believe is that a Lumens value is same measured at every distance from the lens whereas a Candlepower value decreases from the focus, the further away from the lens it is measured.

This Candlepower value would be great if the distance from the lens was given.

Therefore, it is virtually impossible to trust a Candlepower value.

I would love to have the equipement to measure Lumens and Beam Candela. This would allow me to create a standardised measurement test that allowed flashlights to be more easily compared.

Al

 

[Chris M.]

Measuring Lumens- apparently the stuff to do that costs an absolute fortune- you`d have to sell all your SFs to be able to buy second hand photometric equipment needed, from what I`ve been led to believe, and the maths involved isn`t fun either.

Beam Candelas however, that one`s easier- at least as a good approximation. Find a light meter that will read in Foot-Candles. Set your lights 1 foot exactly away from the sensor (ideally 1 foot from the origin of the light- ie the bulb filament) with it perfectly face-on to the light. Gently move it round until you get the peak reading. The foot candle ,reading there is your Peak Beam Candelas. The accuracy depends on many things so without certified lab equipment I`d not take it as 100% perfect. I tend to leave things for 1 minute to settle down cos it changes so much initially, what with batteries running down or thermal runaway mildly toasting LEDs, though if your light has a burn time of 20 minutes, 1 minute is quite a long time, and heat.

My meter came from Farnell Electronics though you may have a bit of bother getting one yourself- apparently they only supply to business account holders and I had to order mine through work, and it was sort of special favour kind of thing to let me do it.

I`d offer to order one for you if you wanted one but I don`t think I can. I`ll ask, it can`t hurt...

 

[Size15's]

Thanks for the offer.
However, I won't be going down that road for years yet me thinks.

Light Quality is far more important to me then CP or Lu values.

A good digital camera is far higher on my list!

Al

 

[YeeDude]

Here are my observations to add to the continuing discussion of lumens vs. candlepower...

As has been said time and again, candlepower measures the "hottest" spot in a given light's beam whereas lumens reflect (no pun intended) the overall amount of light.

I witnessed an interesting demonstration of this recently. During a slightly foggy night I shined my UK Light Cannon out the window at a flagpole on a building across the street, down the block and into a heavily tinted minivan. (And no, nobody was in it, ya pervs!

) I then repeated this with my Turbocat S32 bicycle headlight system and then with a MagCharger.

Here are my observations. The S32 (used both high and low beam) and Light Cannon lit up the flag and down the street in a semi-diffuse way. In contrast to this, the MagCharger, despite being WAY less bright overall, was able to light up the flag better. The reason is obvious - the parabolic reflector.

This happened again in the third "tint test". Both the S32 and Light Cannon fully lit up the side of the minivan, but were only able to slightly light up the interior so that I can see through. With the MagCharger I was able to almost make out the fabric of the seats and not only the silhouette of the headrests.

So lumens and candlepower do have their uses so long as one understands the utility of each measurement and knows what one wants/needs a light to do.

(Hmm.. I wonder if UK would ever make a turbohead for Light Cannon - NOT!

)

 

[**DONOTDELETE**]

Manufacturers are giving us ratings in 2 different ways;

1. measure light emitted from bulb separated from bulb housing and reflector
2. measure brightest concentration of resulting light from bulb and reflector

Both are confusing ways of measuring and rating because flashlights' lightbeam is the resulting light coming from bulb and reflector (including bright and dimmer rings).

As of now a picture of flashlights' lightbeam is still better than lumens or footcandle numbers until manufacturers or flashaholics come up with a standard to measure flashlights' lightbeam.

- verge -

 

[**DONOTDELETE**]

YeeDude said: <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>As has been said time and again, candlepower measures the "hottest" spot in a given light's beam whereas lumens reflect (no pun intended) the overall amount of light.<HR></BLOCKQUOTE>

This is patently false.

An isotropic (radiating in all directions equally) light of one candela will produce an illuminance of one lumen per square foot, which is exactly the same as one foot candle per square foot. NOTE: THEY ARE THE SAME!!

The problem with real life comparisons is that beams from reflector equipped or LED devices is far from isotropic, and the fact that a lumen depends on the wavelength of the light being evaluated. 555 nm. is perceived as the brightest to the non dark adapted eye.

"Full spectrum" devices rarely have a uniform level of light throughout the visible spectrum. This is why some lights are referred to in degrees Kelvin, which correspond to the radiation from a body of a given temperature.

Hope this helps. Go here for further information: http://www.intl-light.com/handbook/ch07.html

Walt

 

[Joe Talmadge]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by V8TOYOTATRK:
I was reading that my Ultrastinger has 75k candle power, then I find out its not the brightest flashlight out there. The M6 by SureFire is 250-500 Lumens. Since the M6 is almost triple to cost of the Ultrastinger, and doesnt have recharagable batteries. I think I would still perfer my Ultrastinger. So the question is, is there a fomula to figure out CP vs Lumens? Like 100 Cp = 1 Lumen?<HR></BLOCKQUOTE>

Not to distract from the interesting lumen vs candlepower discussion, but your assertion above isn't correct. I believe the Surefire 10X Dominator, which is a rechargeable, will do a little over 500 lumens, beating out the M6. If you want the brightest rechargeable and don't mind spending a small fortune, check out the Dominator.

 

[lightlover]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Joe Talmadge:
..........I believe the Surefire 10X Dominator, which is a rechargeable, will do a little over 500 lumens, ...................<HR></BLOCKQUOTE>

Both a 110 Lumen and the 500 Lumen bulb can be run at the same time. See Tim Flanagan's review at - http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=000324

I think Brock reviewed it on his site.

Lightlover

 

[V8TOYTRUCK]

Now I just have to decide, UK light Cannon or 10x?
This has to be my final flash light. No more after this. Well, maybe a few more.

 

[pk]

I might sounds like a sales person,
However I like to inject other benefits of my 10X.

* dual light source.
* dual bulb for lamp failure.
* Duble step momentary switching.
(ergonomic)
* Rugged construction.
* etc.

Thanks,
pk

BTW, I also have a Phillips Xenon Short Arc lamps too (2nd generation).
They are Impressive.

 

[Brock]

PK forgot to mention another big plus for the 10X, it is rechargable, while the Light Cannon isn't.

 

[Size15's]

Also, it's got a SureFire quality beam(s)

I believe with better quality light, it is quicker and easier to see things.

Al

 

[Free]

You all forgot to mention one thing about the 10x....you can't get one right now! I paid for mine last March and I still don't have it because surefire is having problems with their bulbs. Who knows when it will be available??

 

[Size15's]

Your dealer actually took your money?!!

I would not expect to be charged until the item is shipped.

Al

 

[Free]

Yeah I bought something else and he said he had to charge the entire order to ship the one that was in stock. Az Gun Runners, great prices and I have ordered more from them since but I am still waiting for my 10x

 

[YeeDude]

Walt Welch said: <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>"This is patently false."<HR></BLOCKQUOTE>

I apologize for the incorrect statements in my previous posting and defer to Dr. Welch's more accurate explanation of lumens and candlepower.

FWIW, UK claims the Light Cannon put out a beam of 6000 degrees Kelvin.

 

[Size15's]

I read on a chart that 5250K is the colour temperature of sunlight.

The beam is not 6000K hot, it has the colour temperature of 6000K hot. This is most likely based on burning some metal????

So maybe I too was getting the Lumens/CP definition wrong.
Of course, we're talking about BEAMS of light.

How about this?

"Lumens is the whole light of the beam, and CP is the light at one point in the beam." (and that point is not usually given)

I think it's best to express the Lu & CP in terms we can relate to flashlight beams because that will make it easier for us (?)

Al

 

[JoeyL]

I might be oversimplifying parts of it, but the degrees kelvin is a reference to the electromagnetic emission pattern of a "blackbody" radiator. For real world applications, opaque objects that can reach these temperatures emit a spectrum of radiation characteristic of a given temp in degrees kelvin. The sun's photosphere is about 6000 degrees kelvin. It looks yellow white. An object at 10000 degrees kelvin would look a lot more blue. The center of the sun is 15 million degrees kelvin. It emits mostly x-rays at that temperature.

What I'm not sure of, is whether the filament of a bulb with a 6000 degree kelvin whiteness actually reaches close to that temperature. I know that LED's do not, but they emit light on a different principle than heating a filament.