To understand lumens and lux, start with the concept that you can't SEE lumens. Lumens are a measure of the total light sent OUT by the flashlight.
What you SEE is the light that hits something, and bounces back to your eyes. THAT light that you SEE is referred to as LUX. The brighter the OBJECT looks to you, the higher the lux.
When a person says a light is "bright", they might mean it gives you high lux, or, high lumen values...or both....but, might not know why.
If you imagine that water is lumens, and its depth is brightness, so that the deeper the water, the brighter it looks to you...and you look down into a shot glass of water, say an inch deep...and see that brightness in that little glass...
...and then dump that shot glass of water into a kiddie pool, so it spreads out into a wide film of water....it will look "dimmer" but be the same number of lumens.
Humans suck at judging brightness in of itself...but you can see more with more lumens, but, most of the added vision is to the sides in a broad pool of light...and less is added to a central hotspot.
The hotspot generates glare, and the eye tells the brain that more glare = brighter....so people TYPICALLY will say a 100 L focused beam is "brighter" than a 1,000 L floody beam, as the floody one didn't glare and tell the brain how bright it was.
If you looked into the kiddie pool, and saw the dim light, you'd say, "that flashlight is dim".
If you looked into that shot glass, you'd say "that flashlight is bright!".
They both put out exactly the same amount of water/lumens though.
Lux is the lumens per square meter on the target....so, the more lumens you have, the easier to spread them out and still have enough lux to see targets.
If your beam spot is 10 square meters in size, you'd need ten times more lumens to have it look as bright as if it were focused down to only 1 square meter in size.
IE: For the same "brightness", you'd need 1,000 lumens to get your 10 square meters to look as bright as the 1 square meter would look with only 100 lumens.
This is why a guy with a 100 lumen light with a tight beam might say "its impossible to read with it because there's too much glare", but a guy with a 500 lumen floody beam can read the same page with no glare.
What you SEE is the light that hits something, and bounces back to your eyes. THAT light that you SEE is referred to as LUX. The brighter the OBJECT looks to you, the higher the lux.
When a person says a light is "bright", they might mean it gives you high lux, or, high lumen values...or both....but, might not know why.
If you imagine that water is lumens, and its depth is brightness, so that the deeper the water, the brighter it looks to you...and you look down into a shot glass of water, say an inch deep...and see that brightness in that little glass...
...and then dump that shot glass of water into a kiddie pool, so it spreads out into a wide film of water....it will look "dimmer" but be the same number of lumens.
Humans suck at judging brightness in of itself...but you can see more with more lumens, but, most of the added vision is to the sides in a broad pool of light...and less is added to a central hotspot.
The hotspot generates glare, and the eye tells the brain that more glare = brighter....so people TYPICALLY will say a 100 L focused beam is "brighter" than a 1,000 L floody beam, as the floody one didn't glare and tell the brain how bright it was.
If you looked into the kiddie pool, and saw the dim light, you'd say, "that flashlight is dim".
If you looked into that shot glass, you'd say "that flashlight is bright!".
They both put out exactly the same amount of water/lumens though.
Lux is the lumens per square meter on the target....so, the more lumens you have, the easier to spread them out and still have enough lux to see targets.
If your beam spot is 10 square meters in size, you'd need ten times more lumens to have it look as bright as if it were focused down to only 1 square meter in size.
IE: For the same "brightness", you'd need 1,000 lumens to get your 10 square meters to look as bright as the 1 square meter would look with only 100 lumens.
This is why a guy with a 100 lumen light with a tight beam might say "its impossible to read with it because there's too much glare", but a guy with a 500 lumen floody beam can read the same page with no glare.
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