5mm LED Lumens Output

Can someone tell me or calculate out for me the LUMENS/ Luminous flux (lm) For this White 5mm LED.. The datasheet Link is Below.

http://underwaterseaplants.awardspace.com/led.pdf

I would be really thankful to you. This LEDs is being used in a Flash Light..

Candela don't really convert to lumens well, but according to this wizard a rough guestimation of 10,000 mcd @ 15degree beam is about 0.6lumens, @30degree beam about 2lumens, so that gives you an extremely rough ballpark.

RoGuE_StreaK said:

Candela don't really convert to lumens well, but according to this wizard a rough guestimation of 10,000 mcd @ 15degree beam is about 0.6lumens, @30degree beam about 2lumens, so that gives you an extremely rough ballpark.

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I read that formula is only good for the Green LED with a different Wavelength than the WHite One.. for the White LED their needs to be weighting attached to it.. Any idea how it would work out...

Farhaj said:

I read that formula is only good for the Green LED with a different Wavelength than the WHite One.. for the White LED their needs to be weighting attached to it.. Any idea how it would work out...

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No, its the same for all wavelengths.

DollarIn said:

No, its the same for all wavelengths.

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See this PAge.. Where it says a weighting should be applied.. here is the Link,.. http://www.compuphase.com/electronics/candela_lumen.htm

this is what it refers to,,,

"""[h=2]Evaluation[/h]The outcome of the equations (and the calculators based on them) may differ from the data given by a LED or spotlight manufacturer, or from what you measure with a Lux meter, for several reasons. The manufacturer may specify the luminous intensity (in candela or milli-candela) perpendicular to the light source, instead of the average value over the apex angle. Another complexity is that the values for candela, lumen and lux are standardized for light with a wave length of 555 nm, or green light. For LEDs of a different colour, a weighting function should be applied, using a standardized model of the human eye. Standard Lux meters have, at best, only filters for daylight and incandescent light, and may therefore deviate significantly for LEDs (even white LEDs, as the spectrum is not the same as for incandescent lamps)."""""

RoGuE_StreaK said:

Candela don't really convert to lumens well, but according to this wizard a rough guestimation of 10,000 mcd @ 15degree beam is about 0.6lumens, @30degree beam about 2lumens, so that gives you an extremely rough ballpark.

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you can't convert like that. mcd rating is highly dependant of the angle. at 30* same led will not have same mcd as at 15*.


usually those leds around 30 lm/w, those are good ones cree and nichia, no name leds would be less

Farhaj said:

See this PAge.. Where it says a weighting should be applied.. here is the Link,.. http://www.compuphase.com/electronics/candela_lumen.htm

this is what it refers to,,,

"""Evaluation

The outcome of the equations (and the calculators based on them) may differ from the data given by a LED or spotlight manufacturer, or from what you measure with a Lux meter, for several reasons. The manufacturer may specify the luminous intensity (in candela or milli-candela) perpendicular to the light source, instead of the average value over the apex angle. Another complexity is that the values for candela, lumen and lux are standardized for light with a wave length of 555 nm, or green light. For LEDs of a different colour, a weighting function should be applied, using a standardized model of the human eye. Standard Lux meters have, at best, only filters for daylight and incandescent light, and may therefore deviate significantly for LEDs (even white LEDs, as the spectrum is not the same as for incandescent lamps)."""""

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That applies to measuring light, not converting between candela and lumens. If you're measuring candela or lumens the wavelength of the light is important. but if you already know the value, it's a simple calculation.

DollarIn said:

That applies to measuring light, not converting between candela and lumens. If you're measuring candela or lumens the wavelength of the light is important. but if you already know the value, it's a simple calculation.

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Ok so how do u measure light then .. measuring light is also in lumens right..? and how the calculation is done using the wave length,,,

5mm LEDs are often measured in intensity (candelas). This is good for comparing 5mm LEDs as long as the the beam angle is taken into consideration. Why do you need lumens? The brightest, reasonably priced obtainable 5mm LEDs are the Cree C503D series. They are typically 40,000cd (confirmed on my light meter) at a 15 Deg beam angle. I don't have the equipment to measure the lumens.

JohnR66 said:

5mm LEDs are often measured in intensity (candelas). This is good for comparing 5mm LEDs as long as the the beam angle is taken into consideration. Why do you need lumens? The brightest, reasonably priced obtainable 5mm LEDs are the Cree C503D series. They are typically 40,000cd (confirmed on my light meter) at a 15 Deg beam angle. I don't have the equipment to measure the lumens.

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Their are some Forumlas to calculate Lumens.. DO you know any of those... I want to know coz of the Light Output Lumens from the flashlight...

5mm leds are around 3-5lm. some manufacturers still make keychain lights with 5mm leds, they also rate them by lumens
http://www.photonlight.com/led-flashlights/photon-micro-light-ii-led-keychain-flashlight/

alpg88 said:

5mm leds are around 3-5lm. some manufacturers still make keychain lights with 5mm leds, they also rate them by lumens
http://www.photonlight.com/led-flashlights/photon-micro-light-ii-led-keychain-flashlight/

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some even say are in 7-8 Lumens.. some calculations as per datasheet or results would be more helpful and valid...

Farhaj said:

some even say are in 7-8 Lumens.. some calculations as per datasheet or results would be more helpful and valid...

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no, calculations are not as good as acually mesuring output in lightsphere, as pbly manufactures did, before putting lumen number on the box.

but we will be interesting to see what your calculations find, let us know when you fiinish calculations

alpg88 said:

no, calculations are not as good as acually mesuring output in lightsphere, as pbly manufactures did, before putting lumen number on the box.

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This is correct. Unless the light intensity follows a simple mathematical curve across its beam angle or is flat, it would be difficult to figure without lots of sample points. Also, some light is emitted from the sides and behind the LED.

There is no way to directly measure lumens.

Lumens are CALCULATED from the lux, and, that lux has to be measured in a device that spreads the lumens out evenly, so that no one spot is brighter than another. (The device is called an Integrating Sphere (IS), and, amateurs attempt to approximate this with various homemade versions. )

A LUX measurement is then made of that homogeneous light, based upon the assumption that all areas measured yield the same lux reading as the light is homogeneous.

Lumens = Lux per square meter, so, knowing the surface area if the IS (the square meters), and the lux, you can CALCULATE the lumens from that lux reading.

In real life, without a real IS, its actually almost impossible to get a truly homogeneous distribution of light, and, therefore, depending upon the exact spot chosen to measure, the lux levels tend to differ, which changes the calculated lumen estimates.


So, other than using an IS, there is no DIRECT way to convert lux or cd to lumens, any more than you could DIRECTLY convert speed to horsepower. (You'd need more information, and then be able to calculate it, etc...)

well if you want to go into specifics, no dmm mesures volts or resistance, all it does is mesures current. but depending on the settings, it calculates values you are looking for.
same with lightbox, it may mesure lux, but it mesures it, so calculation to get lumens will be based or real performance of that specific led.

alpg88 said:

well if you want to go into specifics, no dmm mesures volts or resistance, all it does is mesures current. but depending on the settings, it calculates values you are looking for.
same with lightbox, it may mesure lux, but it mesures it, so calculation to get lumens will be based or real performance of that specific led.

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Not in this case. The DMM can at least mathematically interpret other values, but, its getting the entire signal to work with. The lux or cd you get is NOT the entire signal.

So, sure, you can be given a cd value someone measured quite accurately....but, there's no way to take a lux value that represents ONLY THE HOTTEST PART OF A HOT SPOT, and have it tell you the lux that you would have gotten to the side of the hottest part of the hot spot, or the corona or the spill, etc....

I can have a light with a cd of 100,000, and it could be one lumen, or a million lumens, there's no relationship between the numbers themselves.

I could have a light with 1,000 lumens, and a cd of 100 or a cd of a million, again, there's no relationship between the numbers themselves....they are simply not representing the same thing.



Its like being told the thickness of the paint on a small piece of wood, and being asked to tell how large a container of paint the paint came from.

They can give you thickness down to the last Aº unit, the most accurate thickness measurement you can get....and you STILL have no way of knowing if the paint came from a 1 qt can, a 1 gal or 5 gal pail....the numbers are simply not related to each other.

do you know how lightsphere works????

alpg88 said:

do you know how lightsphere works????

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If you mean an IS as referred to in my post above, yes.

As I mentioned a few times...if they use one you HAVE the lumens. ..and don't need to ask how to convert.

there are forumlas given on this page to convert various data into Lumens.. I used this http://www.rapidtables.com/calc/light/how-candela-to-lumen.htm
and forund the results per led to 0.54 lm.. which is not at all possible in the real LED. so low..
then, I found out that theformula is good for only upto certain limit of wavelengths in LED.. not for the white LEDS..
I do not know the realty..

can you now excplain..