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More on LED lighting retrofit

Since some people asked, I got out my photometer and measured the light output of my LED lamp strings vs. a 2-lamp 48" fluorescent fixture. I had to back away from the fixtures quite a distance so it was integrating the whole, rather than picking up the hot spots. But, the 20 LED strings running at 350 mA were definitely brighter, by 10 - 15% than the fluorescent. This was a good result, I wasn't sure, due to the somewhat more concentrated output of the LEDs, that they were actually providing more light. It gets pretty subjective.

I found the most repeatable reading was about 2 feet below the fixture. This was looking at the plastic patterned diffuser typical with home ceiling fluorescent fixtures.

Jon

Reply to
Jon Elson
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If you want to measure the total optical output, you need to cob up an approximate integrating sphere: .

An empty room with white walls will do. Put the sensor somewhere it can see the wall opposite the luminaire, shielded such that there is no direct path from luminaire to sensor.

This crude setup will allow you to measure relative output, but not to measure absolute optical output.

Joe Gwinn

Reply to
Joe Gwinn

Way too much trouble! I just wanted a rough indication. We have converted

2 2-lamp fluorescent ceiling fixtures now in the kitchen. There are 3 of them there, I will do the last one fairly soon. I wanted to be sure they were reliable before converting everything.

Light output is quite subjective, and I know I'm partly measuring luminance and not illuminance, but I think it is good enough.

Jon

Reply to
Jon Elson

converted

Actually it is not, but the equipment to measure it well is rather uncommon and often rather expensive. 70 years ago it was easy to get a photographers light meter (which would do the job quite nicely). Now the best you can hope for is an antique match the pointers light meter in that darned old film SLR).

?-)

Reply to
josephkk

it feels like it should be possible to do with a smartphone maybe adding a ping-pong ball as a diffuser

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Reply to
Jasen Betts

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