Lumen vs range? (Solved)

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Krister.student
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Lumen vs range? (Solved)

How can a flashlight with lower luminosity have longer “throw”?

If I understand it correctly, lumen is light intensity per area. A flashlight with a brighter, more focused beam gets a higher luminosity value.
Edit: I was wrong, lumen is total light flow.

Example:
Astrolux EC03 3x XHP50.2 Luminosity: 6 700 lm Throw: 500 m
Astrolux FT03 SST40-W Luminosity: 2 400 lm Throw: 900 m

So the manufacturer’s own specs claim that the flashlight with 2.7 times higher luminosity has a “throw” half as long.
How does this add up?

Edited by: Krister.student on 05/03/2021 - 16:54
Jack Kellar
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Light intensity per area is not measured in lumens, but in candelas. Lumen is the unit for raw luminosity.

raccoon city
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Make yourself at home, Krister.student!

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Firelight2
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Quote:
If I understand it correctly, lumen is light intensity per area.

Incorrect.

  • “lumens” is the total amount of light emitted by a light source. NOT per area.
  • “lux” or “candela” is the intensity of the light emitted. It is the lumens per area at a fixed distance. This, combined with the optic or reflector is what determines throw.

In general, more LEDs or larger surface area LEDs tend to produce the most lumens. Smaller emitters usually produce less overall light, but may have much greater intensity for the light they do produce. A small very intense emitter like the Oslon White 1 in a large reflector might only produce 400 lumens, but still easily out-throw 4,000 lumen multi-emitter light with less intense LEDs and smaller reflectors.

Of course that intensity comes at a price. The beam is very focused and the hot-spot might be tiny. The light might be great for long-range, but be almost useless for up-close. Meanwhile the high-lumen floody light is great for illuminating everything around you up close, but is useless for looking at things 500 meters away.

Krister.student
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Thank you!

roostre
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Krister.student wrote:
How can a flashlight with lower luminosity have longer “throw”? ...

The link below is to a blog post by forum member "dave1010" about "Converting Candela to Throw" and explains the difference between lumens, lux, and candela.

https://davestechreviews.wordpress.com/2020/05/26/converting-candela-to-...

I especially enjoyed the explanation for the ANSI measurement of throw with a comparison to the light from a full moon and the practical expectations of that.

How many flashlights does a "real man" need?

None, real men are not afraid of the dark.

jon_slider
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> How can a flashlight with lower luminosity have longer “throw”?

by focusing the light beam into a smaller area

xxo
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Here’s a vid that explains it:

zoulas
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Lumens and candela are both desirable, however there is typically (not always) a tradeoff. For example the Osram leds tend to have higher candela and lower lumens. They are really two different tools for two different applications.

Scotty321
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I tend to think of it like a spray bottle. With each squirt, you are putting the same amount of liquid. However, if you twist the nozzle to “spray” it spreads that water over a large area but doesn’t reach that far, versus if you twist the nozzle to “stream” all the liquid goes in one direction with longer range, but hitting a small spot.

I would assume from your example that the 6,700 lumen light is more floody (spray) than the 2,400 lumen light (stream).

kennybobby
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Nice analogy Scotty, thanks for sharing.

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ChibiM
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Hmmm. that analogy may go a little wrong Big Smile 

Or maybe I am thinking too deeply. 

Many new people may think: when you have a 10,000-lumen bottle with a spray nozzle, it should be throwing much farther when you change from spray to 'stream' than a 2,000 lumen bottle with a 'stream' nozzle (even though the bottle is smaller)

But the problem is: the 2,000-lumen spray bottle could outspray the 10,000 lumen spray bottle with the same diameter reflector/nozzle....(if you compare this to how LEDs work)

The size of the hole is even more important.. for throwing farther. Not just the wideness of the spray/stream.

 

Scotty321
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True, it is an oversimplification, but I think it helps to get a general understanding of lumens and throw specs when shopping online.

Similarly, I usually do a quick cd/lumen calculation to get an idea on how floody a beam will be when just looking at specs. That too is an oversimplification, but it helps me get an idea of what to expect when ordering online.