LED Lumens & Tungsten Lamp Lumens ???

As stated in SureFires L1 Operator's Manual.

"Accurately specifying light output ( lumens ) and runtime is
more complicated for LED flashlights than it is for tungsten
lamp flashlights."

"What can be said, in simple terms at this time, is that the light
output of the L1 exceeds the 60 lumen output of comparable
SureFire tungsten lamp flashlights, and runtime is longer than
the one hour specified for the tungsten lamp flashlights."

This is an interesting statement. Does anybody know why LED
lumens are different than tungsten lamp lumens ???

The SureFire Web Site says that the output of the L1 in the high
beam is "15 lumens".

.............. /ubbthreads/images/graemlins/thinking.gif

I think it was agreed in the past that the 60 lumen figure in the L1 manual was an error - the paragraph probably cut and pasted from an L2 or L4 manual.

I think this has to do with the difference between regular (photopic) lumens and scotopic lumens (sometimes called brightness lumens). If two light sources have the same scotopic lumens but different color temperatures, the one with the high color temperature will be perceived as brighter at levels typical of indoor artificial lighting. The difference can be as much as a factor of two when comparing 6000K to 2700K.

Maybe they are making reference to the V-lambda curve and its static application when in fact its dynamic.

Just as we are more sensitive to sounds in the 3khz area than we are in the 120khz region, same too are we with light. Obviously a lamp that produces 1000lumens (in terms of blackbody temperature increase) of IR would not be very useful for us. So the wavelength of light is actually accounted for in lumen and cd derivation.


However, this curve is setup for optical sensitivity to light while the eye is in an adjusted state. When our eyes have adjusted to the dark, we have a different sensitivity curve. Ever notice how red looks black at night? Obviously, red is taken into account when developing the spectral power distribution but it shouldn't be weighed as much in the low light conditions. So in this way a blue/white led can portray higher effective lumens in low light than is derived by the integrating sphere. You can really notice this effect if you have a car with HIDs then try to drive a car with tungsten lamps.


This is a better explanation of the concept: Lumens and the eyes sensitivity


HTH

-Craig

Interesting thread.
I've noticed myself that under relatively similar conditions as far as ambient light goes, LED based lights seem to cause more immediate discomfort and leaves an after-image behind that seems to last for longer than an incandescent lamp does.
Ofcourse, this is all very subjective, but I've long considered this to be a factor that may count for LED's being used for "tactical" purposes. Worth investigating further, I think.

[ QUOTE ]
ErickThakrar said:
Interesting thread.
I've noticed myself that under relatively similar conditions as far as ambient light goes, LED based lights seem to cause more immediate discomfort and leaves an after-image behind that seems to last for longer than an incandescent lamp does.


[/ QUOTE ]


You should try driving on poorly marked Oregon roads in the rain, and an oncomming car is using HID lights. When there is basically no ambient lighting, and an oncomming car's light basically blind you, and then the very high amount of glare off the wet pavement that has weak paint marking in the first place, toss a little rain on the window on roads that aren't city slicker straight, and you are basically driving blind.

I've even had to hit the brakes and stop, and wait for the driver that has HID lights to pass, as I cannot see the road at all, under non-straight road conditions.

In the city, with it's very high night ambient lighting levels, HIDs are no bother at all, even in otherwise similar conditions, especially with the city straight roads.

Then there is the all brown deer argument, which can be difficult to see with HID.

There is a very good discussion of night lighting, its issues, and such, with some great tidbits dispersed around, that Daniel Stern lighting did for the government:
http://dmses.dot.gov/docimages/pdf82/176157_web.pdf

Here is the human eye response:



Here is an incandescent I measured:



Here is a white Luxeon I measured:

.

Newbie,

That incan -- does it continue to rise into the infrared and tail off, per textbook blackbody curve?

Scott

[ QUOTE ]
Luna said:Obviously a lamp that produces 1000lumens .... of IR would not be very useful for us.

[/ QUOTE ]

This is a good one, unfortunately a week too late (for an April's fool joke). .-))

How can a lamp, which emits invisible radiation, give 1000 lm?

Back to the question:

Which other differences do we have in between incandescent bulbs and LEDs except light colour?

Newbie:
I was the first one here around using white LED lights for caving in a previous millenium.
While my light was relatively bright, I had a much harder time to find red survey marks than people had with carbide lights (ceiling burner type, that means completely unfocused, no throw at all).

when balancing for White LEDs both Luxeon, and Nichita, both driven hard.
i saw the spectrum, and thought,
Add CYAN , And Red to get more incadescent looking for a video camera (Seperated RGB Hyper CMOS stuff)
i ended up adding in LOADS of Yellow & Amber, tiny bits of cyan, and little red. less red and cyan than i had suspected via the charts, and WAY more Yellow and Amber.

didnt make sence, i see this chart (above) newbie makes which is almost exactally what is shown on the luxeon specs ( i was using), and added accordingly.

it did eventually make sence that cyan wasnt working, to much green, but it still makes no sence why it wanted so much yellow, when the chart shows a plethera of it.
adding in a fair ammount of red, just turned too red FAST.

[ QUOTE ]
beezaur said:
Newbie,

That incan -- does it continue to rise into the infrared and tail off, per textbook blackbody curve?

Scott

[/ QUOTE ]


My setup doesn't measure out that far.

[ QUOTE ]
PeLu said:
[ QUOTE ]
Luna said:Obviously a lamp that produces 1000lumens .... of IR would not be very useful for us.

[/ QUOTE ]

This is a good one, unfortunately a week too late (for an April's fool joke). .-))

How can a lamp, which emits invisible radiation, give 1000 lm?


[/ QUOTE ]

That would be a byproduct of a normal distribution if CIE and IR starting in the 710nm range /ubbthreads/images/graemlins/wink.gif

Funny how your clippage of "(in terms of blackbody temperature increase)" changes things /ubbthreads/images/graemlins/twakfl.gif

1000 lumens =1.4 watts of power measured blackbody temperature increase without a CIE filter inplace.

-Craig

[ QUOTE ]
NewBie said:
Here is a white Luxeon I measured:




[/ QUOTE ]

Take note of the two peaks, the blue being the LEDs primary wavelength and the yellow being the phosphors.

I believe it is the distribution and density of the phosphors on the die being the primary determiner of color binning. The proportion of the two outputs determining the color


-Craig