Apr
13
Difference between lux and lumens?
Hey everyone.
I’ve been wanting to purchase a flash light. I’m a bit confused though.
So far all the flash lights I have taken a look at measure their brightness in lumens, like this one for example: http://www.dealextreme.com/p/ultrafire-u4-mcu-cree-q5-wc-3-mode-230-lumen-led-versatile-flashlight-cr123a-18650-18500-aaa-17401
And this other flash light I found has a different measurement. I don’t understand it.
http://www.dealtoworld.com/reviews-12479-50767-Bright+flushlight.html
The output is 85 lumen…? This flash light is a lot better than the first one, so I’m a bit confused.
Could someone please explain me how this stuff works?
Also, if you have any idea how much lumens the second flash light might be, please let me know.
Thanks everyone.
From Wikipedia
Lux versus lumen
The difference between the lux and the lumen is that the lux takes into account the area over which the luminous flux is spread. A flux of 1,000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1,000 lux. However, the same 1,000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux.
Achieving an illuminance of 500 lux might be possible in a home kitchen with a single fluorescent light fixture with an output of 12,000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures. Thus, lighting a larger area to the same level of lux requires a greater number of lumens
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