Are LED and incandescent lumens ratings comparable?

AlonzoMosely · Sep 16, 2007

I have a couple of Surefire incandescents and have been reading about the Fenix LEDs on this forum. Is a Fenix P3d Premium 100 really twice as bright as a Surefire 9p and over 3 times as bright as a Surefire E2D??

Dinan · Sep 16, 2007

AlonzoMosely said:
I have a couple of Surefire incandescents and have been reading about the Fenix LEDs on this forum. Is a Fenix P3d Premium 100 really twice as bright as a Surefire 9p and over 3 times as bright as a Surefire E2D??

Well you have to first compare the lumens out the front. From what I understand, Surefire lists lumens out the front, while Fenix lists lumens from the bulb, not taking into account loss from reflector and the window, etc. The general rule of thumb is to multiply the Fenix lumens by 0.65 and you'll get pretty close to what's coming out the front.

Also, suppose you have two flashlights with the exact same light source, reflector, window, etc - but one is rated 200 lumens while the first is 100. Some people may list this as the 200 lumen one is 2x brigher, but to the human eye it only appears a little brighter, certainly not twice as bright. This is because the human eye perceives light logarithmically. I'm not exactly sure on the numbers, but I heard somewhere that squaring the lumens will double the perceived light. But again, I'm not sure so don't quote me on those numbers...

Short answer... no the P3D won't appear twice as bright as the 9P or three times as bright as the E2D. It will certainly appear a little brighter... but not twice as bright. Actually I don't think it would even appear that much brighter than the P90 LA since it's much more of a thrower.

AlonzoMosely · Sep 16, 2007

Very helpful, thanks!

Size15's · Sep 16, 2007

There are several issues to contend with:

1) Ability to trust the output ratings offered by manufactures. As mentioned different manufacturers create their ratings using different methods.

2) Different beam profiles will make it very hard to accurately judge lumen output. The beam profile is the distribution of the light within the beam - how much is in the central beam, and how broad the central beam is, and how much is in the surround beam, and how broad it is, and how the central beam and surround beam are 'blended' (or not) together, as well as the quality (homogeneity) of the light etc etc.

3) The ability of the eyes to see different things under different light-levels and atmospheric conditions using different light sources. (output spectrum relative to the photopic or scotopic luminosity function). Related is whether the light needs to be used to illuminate targets and/or disrupt the vision of people being illuminated etc.

Is 100 lumens of 'white' LED light the same as 100 lumens of 'white' incandescent light?
No.
The lumen is the unit of luminous flux - it is used to measure the perceived power of light. When measuring this power using an integrating sphere the sensors are adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.

Curious_character · Sep 16, 2007

Size15's said:
There are several issues to contend with:

1) Ability to trust the output ratings offered by manufactures. As mentioned different manufacturers create their ratings using different methods. . .

Because one of those methods is pure fabrication -- simply making up whatever number helps them sell lights -- using those numbers to make any kind of comparison is a fool's errand.

The fact that it's so hard to measure and judge lumen output, as you explain, makes it easy and irresistibly tempting for manufactures and dealers to pull off this deception. And it's abetted by the people who willingly believe whatever the manufacturers and dealers tell them.

c_c

WadeF · Sep 16, 2007

P3D Rebel100 is putting out around 140-150 lumens out the front. They claim 200 at the emitter. So if Surefire was rating it with their methods, I would guess they would rate it somewhere around 130-140 lumens, but who knows.

LuxLuthor · Sep 16, 2007

Size15's said:
There are several issues to contend with:

1) Ability to trust the output ratings offered by manufactures. As mentioned different manufacturers create their ratings using different methods.

2) Different beam profiles will make it very hard to accurately judge lumen output. The beam profile is the distribution of the light within the beam - how much is in the central beam, and how broad the central beam is, and how much is in the surround beam, and how broad it is, and how the central beam and surround beam are 'blended' (or not) together, as well as the quality (homogeneity) of the light etc etc.

3) The ability of the eyes to see different things under different light-levels and atmospheric conditions using different light sources. (output spectrum relative to the photopic or scotopic luminosity function). Related is whether the light needs to be used to illuminate targets and/or disrupt the vision of people being illuminated etc.

Is 100 lumens of 'white' LED light the same as 100 lumens of 'white' incandescent light?
No.
The lumen is the unit of luminous flux - it is used to measure the perceived power of light. When measuring this power using an integrating sphere the sensors are adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.

That should be a pinned proclamation. :grin2:

I'm not even sure the integrating spheres are all that useful when it gets into practical useage. There are so many times when I want to have the xxx lumens focused into a far throwing beam, and there is little objective way to quantify something like that when it involves so many variables such as the bulb/LED characteristics, reflector size/shape/texture, lens, and all the other things you mentioned. :thumbsup:

Curious_character · Sep 16, 2007

WadeF said:
P3D Rebel100 is putting out around 140-150 lumens out the front. They claim 200 at the emitter. So if Surefire was rating it with their methods, I would guess they would rate it somewhere around 130-140 lumens, but who knows.

How did you determine the output?

c_c

WadeF · Sep 16, 2007

Curious_character said:
How did you determine the output?

c_c

Chevrofreak constructed a home made integrating sphere and game up with around 140-150 lumens for the P3D Rebel100. Again, these are approximations. I arrived at similar readings from my own testing with a bounce box and a light meter. I compared it with other incans, Surefire, etc, where the company stated lumens out the front figures, and from there you can approximate.

Here's a graph from one of Chevrofreak's tests comparing the various Fenix P3D's, Cree P4, Q5, and Rebel100:

http://lights.chevrofreak.com/runtimes/Fenix P3D - various LED's.png

As others are saying, knowing the lumen output doesn't tell you everything, the beam pattern has a lot to do with how those lumens will perform. An 80 lumen light could have a much brighter hot spot than a 150 lumen light, etc.

Are LED and incandescent lumens ratings comparable?

AlonzoMosely

Newly Enlightened

Dinan

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AlonzoMosely

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Size15's

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Curious_character

Flashlight Enthusiast

WadeF

Flashlight Enthusiast

LuxLuthor

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Curious_character

Flashlight Enthusiast

WadeF

Flashlight Enthusiast

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