It would be very helpful to me to have ordinary lighting reference points expressed in lumens as means of visualizing the lumens of flashlights. For example, if a flashlight's output is expressed as a certain [x] number of lumens utilizing common experiences of lighting amounts it would be much easier to visualize a particular amount of light expressed in lumens (2-5 lumens is like the amount of light from the moon on a clear night, or the lumens of light at a night game of a football stadium) Is anyone aware of such examples of amounts of light expressed in lumens?
Ordinary lighting experiences expressed in lumens
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Well, someone who knows what they're talking about will probably step in shortly with the right answer, but I think you're comparing apples and oranges.
If you take a flashlight out on a moonlit night, the beam will be much brighter than the moonlight at close distances, but falls off rapidly as distance increases. If your flashlight is floody, that will be different than one with more throw. So, I don't think you can compare brightness the way you want unless you specify distance, pattern and perhaps a few other things I haven't thought of.
A simple exposure meter would tell you relative brightness of a specific flashlight at a specific distance compared to whatever reference you choose. You will also have to specify whether you are talking about the center hot spot or the floody surround.
If you take a flashlight out on a moonlit night, the beam will be much brighter than the moonlight at close distances, but falls off rapidly as distance increases. If your flashlight is floody, that will be different than one with more throw. So, I don't think you can compare brightness the way you want unless you specify distance, pattern and perhaps a few other things I haven't thought of.
A simple exposure meter would tell you relative brightness of a specific flashlight at a specific distance compared to whatever reference you choose. You will also have to specify whether you are talking about the center hot spot or the floody surround.
I am not sure to be right but for me you are trying to compare two different things. The light emitted (e.g.) by your flashlight - in lumen(s) - and the light received (e.g.) from the moon - in lux -.
The light of the moon may vary a lot during the night, may vary a lot at the same moment between different places, may vary a lot between seasons, etc. That is not a good way to find a reference for comparison (= a standard).
The best way is to measure lumen and lux with a dedicated tool.
"the lumens of light at a night game of a football stadium". i'm still not sure but if you measure the lux "where you are" and know the distance between you and a light source then you can calculate (lux @ 1 m of this source and then) lumens of this light source. But in a football stadium, you would probably measure the light received from several sources in the same time.
The light of the moon may vary a lot during the night, may vary a lot at the same moment between different places, may vary a lot between seasons, etc. That is not a good way to find a reference for comparison (= a standard).
The best way is to measure lumen and lux with a dedicated tool.
"the lumens of light at a night game of a football stadium". i'm still not sure but if you measure the lux "where you are" and know the distance between you and a light source then you can calculate (lux @ 1 m of this source and then) lumens of this light source. But in a football stadium, you would probably measure the light received from several sources in the same time.
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asdalton
Flashlight Enthusiast
Lumens are the unit of measure for luminous flux, which is the total amount of visible light emitted by an object.
(This is a different quantity from illuminance, measured in lux, which is the intensity of light incident on a surface.)
Some approximate luminous flux values for common items:
60 W incandescent light: 900 lumens
100 W incandescent light: 1700 lumens
Typical 2D alkaline incandescent flashlight: 15 lumens
Typical 2-cell lithium incandescent tactical flashlight: 60 lumens
(This is a different quantity from illuminance, measured in lux, which is the intensity of light incident on a surface.)
Some approximate luminous flux values for common items:
60 W incandescent light: 900 lumens
100 W incandescent light: 1700 lumens
Typical 2D alkaline incandescent flashlight: 15 lumens
Typical 2-cell lithium incandescent tactical flashlight: 60 lumens
parnass
Flashlight Enthusiast
According to this info, a Pyralis firefly emits 1/40th of a lumen (0.025 lumens).
MikeAusC
Enlightened
No, you're getting confused between -
- Lux - the brightness at one point, something you can measure with a lightmeter
- Lumen - the TOTAL amount of light put out by a source.
You can measure the Lux from moonlight, but to determine Lumens emitted by the moon, you'd MEASURE the Lux on the earth, then use the distance from Earth to Moon and make assumptions about the beam width of light coming off the moon to CALCULATE the Lumens put out by the moon.
MikeAusC
Enlightened
There are tables available of the light level in Lux to perform various tasks e.g. reading.
To know how many Lumens are needed you'd also have to specify what area you want illuminated.
E.g. if you're reading and you're happy with having an area the size of a postage stamp lit up, you might be happy with 1 Lumen. If you wanted a complete newspaper lit up to the SAME BRIGHTNESS, you'd need 100 Lumens.
To know how many Lumens are needed you'd also have to specify what area you want illuminated.
E.g. if you're reading and you're happy with having an area the size of a postage stamp lit up, you might be happy with 1 Lumen. If you wanted a complete newspaper lit up to the SAME BRIGHTNESS, you'd need 100 Lumens.
The best way is just experience with various multiple mode flashlights.
joema
Flashlight Enthusiast
1 lux = 1 lumen per square meter, so if all the output of a 1 lumen light was focused on a 1 square meter target, that would be 1 lux.
With that relationship understood, below are lux values of common experiences:
110,000 lux - bright sunlight
10,000-25,000 lux - typical overcast day
50-200 lux - recommended level for average reading
10-20 lux - outdoor parking lot at night
1 lux - moonlight
0.002 lux -starlight on a clear night
0.0001 lux - starlight on a cloudy night
http://en.wikipedia.org/wiki/Daylight
http://www.engineeringtoolbox.com/light-level-rooms-d_708.html
When going from an office building at 200 lux to sunny outdoors, you don't perceive that being 500 times brighter. Your eyes perceive light levels logarithmically -- double the lumen or lux level only appears a little brighter. This is obvious from the above values. The lesson is don't over-emphasize flashlight lumen differences, as you often can't see the difference.
MikeAusC
Enlightened
If you see it, then it's emitting Lumens, in fact the moon is as bright as any object which has full sunlight falling on it - something that surprises people trying to photograph the moon.
It doesn't matter whether the light from an object is due to -
- incandescence (filaments)
- fluorescence (white LEDs, fluorescent lamps)
- ionisation (HID lamps)
- nuclear reaction (sun)
- reflection (moon, reflector-torch)
- refraction (indirect daylight)
