# Thought for the day



## degarb (Dec 8, 2014)

http://www.carbonlighthouse.com/2014/02/13/683-lumens-per-watt/

Interesting article. Suggested to me, by my creepy, snooping phone. The article explains why there was so many conflicting posts as to the max lpw. It used to be 270. But Cree broke 300. Maybe 270 is for high cri?


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## KITROBASKIN (Dec 8, 2014)

It is an interesting article. Some elements have been presented by CPF members in the past. Perhaps you will consider changing the title of this thread to reflect more accurately the content thereof...


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## degarb (Dec 9, 2014)

Eric's thought of the day? 683? Why there are conflicting LPW citations? The Green Lantern got it right? My Moto X gives me the creeps?

Better suggestion? I can't decide.


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## CoveAxe (Dec 9, 2014)

degarb said:


> Why there are conflicting LPW citations?



Because it's completely dependent on the photoresponse of the eye. A 100% efficient blue light source is going to look much dimmer than a 100% efficient green light source with the same power, so they will have different LPW numbers. The 250LPW "cap" is based on the assumption that the emitter has a truncated blackbody response in the visible range. A higher LPW than that for white means that some more light is being emitted in the green/yellow band. You can get different numbers based on your spectrum. Here's one paper that goes into a bit more explanation.


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