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Author Topic: LED's and Lumens  (Read 1892 times)

BiGReD

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LED's and Lumens
« on: September 29, 2003, 11:24:44 PM »

Does anyone know how many lumens approx. 50 White 8000mcd LED's would be?
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qscwdvefzrax

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LED's and Lumens
« Reply #1 on: September 29, 2003, 11:53:12 PM »

Lumens and candela are somewhat different terms, explained http://www.energybooks.com/pdf/D1150.pdf">here.

Lumens is the measurement of total energy radiated by a source of light, and candelas measure the amount of luminosity, the amount of light shone in a single, cone shaped section. http://www.westsidesystems.com/rays.html"> Reference here

Thus you cannot really extend a calculation from the amount of candlepower to the amount of lumens given off because of the difference in the direction of the radiated light, but if a source were giving 1 candlepower in a uniform sphere, it would be outputting a total of 12.57 lumens. http://www.artograph.com/art_projector_glossary.htm">Reference here

Hope this helps.
Q

EDIT: forgot to actually calculate your units:
50 LED * 8000 mcd/LED * 1cd / 1000mcd * 12.57 lum / 1 cd = 5028 lum
 :o ...... Somehow this does not seem physically correct.... :-?  :wtf:
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BiGReD

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LED's and Lumens
« Reply #2 on: September 30, 2003, 12:46:06 PM »

Quote from: qscwdvefzrax
Lumens and candela are somewhat different terms, explained http://www.energybooks.com/pdf/D1150.pdf">here.

Lumens is the measurement of total energy radiated by a source of light, and candelas measure the amount of luminosity, the amount of light shone in a single, cone shaped section. http://www.westsidesystems.com/rays.html"> Reference here

Thus you cannot really extend a calculation from the amount of candlepower to the amount of lumens given off because of the difference in the direction of the radiated light, but if a source were giving 1 candlepower in a uniform sphere, it would be outputting a total of 12.57 lumens. http://www.artograph.com/art_projector_glossary.htm">Reference here

Hope this helps.
Q

EDIT: forgot to actually calculate your units:
50 LED * 8000 mcd/LED * 1cd / 1000mcd * 12.57 lum / 1 cd = 5028 lum
 :o ...... Somehow this does not seem physically correct.... :-?  :wtf:


Well if you're right, then 5028 lumens focused on one area is gonna be at least 10000 lumens, which is good for what i was planning.

I can't tell you what it is because it is such a good idea you people will steal it.  It's as good an invention as the TV was 50 years ago.
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snow veil

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LED's and Lumens
« Reply #3 on: October 05, 2003, 04:54:12 PM »

Quote from: qscwdvefzrax
Lumens and candela are somewhat different terms, explained http://www.energybooks.com/pdf/D1150.pdf">here.

Lumens is the measurement of total energy radiated by a source of light, and candelas measure the amount of luminosity, the amount of light shone in a single, cone shaped section. http://www.westsidesystems.com/rays.html"> Reference here

Thus you cannot really extend a calculation from the amount of candlepower to the amount of lumens given off because of the difference in the direction of the radiated light, but if a source were giving 1 candlepower in a uniform sphere, it would be outputting a total of 12.57 lumens. http://www.artograph.com/art_projector_glossary.htm">Reference here

Hope this helps.
Q

EDIT: forgot to actually calculate your units:
50 LED * 8000 mcd/LED * 1cd / 1000mcd * 12.57 lum / 1 cd = 5028 lum
 :o ...... Somehow this does not seem physically correct.... :-?  :wtf:


That's because it's not.  If a candela and a lumen are too different to easily convert, your conversion is off.  Plus, note the quote "if a source were giving 1 candlepower in a uniform sphere, it would be outputting a total of 12.57 lumens."  It's not giving off candelas in a sphere, so you won't have that many lumens.  Likely an 8000mcd LED is going to have a very small viewing angle which will in turn bring the lumen value down drastically.

The idea was researched thoroughly at DIYaudio.com forums to look for a feasible LED powered DIY projector, but time after time the idea was tossed out.  At the current time, there is just no efficient way to use LEDs in a DIY projector.

Though I'm no expert in lumen/candela conversion, to get a possibly more accurate reading, try factoring in the ratio of the viewing angle of the aforementioned LED into that of a spherical size in which the candela is measured.  It'll take more research, but it'll possibly provide you with a better estimate.

Theneler

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LED's and Lumens
« Reply #4 on: October 14, 2003, 02:00:30 PM »

Yeah, standard LEDs have a viewing angle of 45 degrees, so technically you should take your total lumans ( it was around 5000 ) and then take 45 percent of that, and you will get a closer idea.
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