When people see light level change

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Research indicates that people often perceive dimming levels of 80-85% as similar to 100%, making it difficult for them to visually distinguish between these levels. Factors influencing this perception include the type of light source used (LEDs, incandescents, CFLs) and the method of dimming (potentiometer vs. PWM). The discussion seeks to identify the origins of this finding, with initial suspects being Lutron and EnergyStar, which have promoted the idea of significant dimming without noticeable differences. A user later shared links to studies that support this concept, highlighting the physics behind intensity changes and visibility thresholds. Understanding these findings can help in optimizing lighting solutions for energy efficiency.
jgeverin172
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Hey Guys (my first post!),

I've been trying to dig up this information for quite some time now, and I figure physicsforums may be the place to ask.

I keep 'hearing' of some research that was done that concludes that people interpret 80-85% (or some other fraction) of dim level as the same to them as 100% dimming level; that is, people (for the most part) couldn't see the difference in dim level on some load. Even though in actuality, the presented dim levels would be different. Please ask me to rephrase if it's not clear enough.

Obviously many factors would be involved in said 'study'. What kind of loads was said 'experiment' performed on? (LEDs, incandascents, CFLs, etc.)
Was the dimming done with a potentiometer dimmer or PWM? (if PWM, then 80-85% dimming would imply 80-85% duty cycle!)
There may be other factors too, but anyways...

What I'm trying to figure out is WHO came up with said study? Also, if anyone knows of said experiment, then I'd love to see a link to it! Has anyone heard of this idea before? The idea being again: People can't visually tell the difference in dimming between 100% and 80-85% (or some other dimming level). I've heard of this idea floating around awhile, but could never figure out WHO concluded this; or WHERE did this idea come from?

My initial suspects were Lutron and EnergyStar. Lutron touted their product that produces 70-75% dimming on normally fully on loads, claiming that people don't notice. EnergyStar had a big article on the internet somewhere on potential savings in lighting.

If anyone knows what I'm talking about, and knows where this idea stemmed from, please help.

Thank you for your time!
 
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Look to the definition and discussion of intensity. I think you'll find physics suggesting that intensity changes < 3dB are not visible.
 
Thanks for your response!

However, I actually ended up finding what I needed, but thanks again for your generous feedback.

Here's the article outlining the study where this 'idea' stemmed from, in case any googlers or forum users need this too :) ...

(Powerpoint)
http://www.lrc.rpi.edu/researchAreas/reducingBarriers/pdf/year3/DOEAppendixH.pdf

(follow-up article)
http://www.lrc.rpi.edu/researchAreas/reducingBarriers/pdf/year3/DOEAppendixJ.pdf
 
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