On Friday, August 30, 2013 3:36:38 PM UTC-5, George Cornelius wrote:
D. Peter Maus wrote:

On 8/9/13 18:48 , Joe from Kokomo wrote:

On 8/9/2013 2:33 PM, D. Peter Maus wrote:



So far, I"m getting the equivalent of 75w incandescent light out of

one 8.5W LED lamp.



The URL/ ad that you quoted said:



Stock Code: ETI-520163MD

8.5 Watt - LED Light Bulb - Omni-Directional A19 - 3000K Warm White -

600 Lumens - 50 Watt Equal



They advertise it a 50 watt equivalent but you are saying it's the same

as 75 watts. If it really is close to 75, one would think they would not

be shy and call it 75.



Are you actually measuring the lumen output or just "eyeballing" it? Do

you have higher than 'normal' line voltage?



Not pickin' on ya, D.P. It's just that inquiring minds want to know why

the difference. :-)





Dial it back, Joe.



I did mention that I used a light meter to measure the output. Were

you not reading?



My understanding is that a lumen is not directly a measure of

output power. It is modified by a weighting curve, I believe,

to reflect our eyes' varying response to different wavelengths.



So you need, of course, a light meter that reads true lumens,

not just power output (energy per unit time).



But I agree with your statement below that they may be quoting average

output over the rated life of the device.



White LEDs do not directly produce light, like a single color LED.

They produce a wavelength and expose it to a phosphor which causes the

phosphor to flouresce. Since that's a ablative process, the output of a

white LED diminishes over time, depending on how hard the phosphor is

worked.



Here's some info, albeit somewhat technical:



http://www.digikey.com/us/en/techzon...of-fading.html



I had no idea that the process involved the additional step. Nor did

I realize that fading might occur, caused by crystalline imperfections

that grow worse over time.



This article claims that the band gap is such that the naturally

produced radiation is towards the short wavelength end of the

visible, and that the fluorescence (phosphorescence?) adds in

the longer wavelengths so that the resulting radiation appears

white, i.e., distributed more uniformly across the visible

spectrum.



George



White LED lamps are correctly rated at an average luminary output over

time.



I'm at the beginning of these lamps' life cycle. So output is higher

than rated.

Roundup: 100 Watt Equvalent LEDs. http://spectrum.ieee.org Sumpin like that. You can find it at www.blacklistednews.com How To Survey A Home For Internet Interference. www.technewsworld.com Sumpin like that.