How many lumens?

[Dustin Liu]

How many lumens is the sun?

Seriously

I really want to know.

[Illumination]

Lumens is a measure of total light output...the total light output of the sun is simply not worth comparing to any hand held flashlight. The sun lights up half the earth, the moon, and the rest of the planets in the solar system, etc. That is like comparing the weight of a grain of salt to the weight of the earth. Maybe that is what you are looking for...but I'm not sure why.

Or are you trying to compare brightness of sunlight versus the brightness of a flashlight on a particular object (e.g., a light meter). Then you should be comparing a measure of brightness, like lux (which is defined as lumens per square meter), of one versus the other.

Of course, you are then going to have to think about how far away the light will be held from the object you are illuminating. Lets first think about the brightness of flashlights. The Throw measure on Flashlight Reviews Throw and Output Table shows the distance (in meters) a given light throws 1 lux. You can then use the inverse square law to figure out brightness at a given distance. The formula would be Brightness (in lux) @ Distance (in meters) = (1/ (Distance/Throw) )^2.

For an example, according to throw and output chart, the Surefire A2 Incan throws 45. Using the inverse square law, that light has a brightness of 2025 Lux at 1 meter.

To compare it to sunlight, look at this table I found this table on the internet:

Brightness Values:

Candle light at 20 cm 10-15 Lux
Street light 10-20 Lux
Normal living room lighting 100 Lux
Office fluorescent light 300-500 Lux
Halogen lamp 750 Lux
Sunlight, 1 hour before sunset 1000 Lux
Daylight, cloudy sky 5000 Lux
Daylight, clear sky 10,000 Lux
Bright sunlight > 20,000 Lux

So...an A2 at it's brightest spot shining at something one meter away is about half as bright as sunlight on a cloudy day. This seems reasonable - remember at night flashlights look so bright because everything else is dark and your eyes adapt.

[ringzero]

Originally Posted by Dustin Liu

How many lumens is the sun?

It's fairly straightforward:

1) Look up the Sun's total output in Watts. I've seen the figure, but don't remember offhand.

2) Look up the percentage of the total ouput that falls in the visible light part of the spectrum.

3) Calculate the visible light output of Sun in watts by multiplying 1) times 2). Maybe you can find this figure somewhere and skip the first two steps.

4) Last step: convert Watts to Lumens.

[winny]

~3.75×10^28 lm according to wikipedia.org

link

[Gnufsh]

Only a very tiny fraction of the light from the sun hits the earth, or any planet at all for that matter. The vast majority just heads off into space.