Hi Vasile,

I guess I am basing my expectation of long life from low-output LEDs
used for indicators. The high drop-off may just be the higher efficiency
of modern LEDs. If an LED output drops 50% it may not be noticeable. But
if a high-efficiency LED loses 90% it is obvious. But maybe the output
is still higher than a low-efficiency LED.

Cheerful regards, Bob

On Fri, Jul 4, 2014, at 11:37 PM, Vasile Surducan wrote:

> Bob, we irradiating plants in microwaves using anechoic chambers.  Since
> are closed chambers, the light comes from LED spots (27 warm SMD warm
> LEDs
> at 3000K, 4W/12V per spot).
> Experiments took from one week to couple of months. (One type of
> experiment
> with coloured LEDs is here:
> http://www.itim-cj.ro/~vasile/T1_SurducanV.pdf).
> I'm measuring the light intensity using a professional luxmeter. Usually
> in
> the first week, the light intensity is decreasing with 200 to 400lux from
> an initial value of 3000lux measured at 30cm distance to the spot. So, I
> think your blue LED behaviour is absolutely normal after 5 years.


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