Question about light measurement

rockinbbar

rockinbbar

New member
Ok, I know this gets confusing, at least to me.

I've heard the "candle power" is not a reliable measurement of light output, and that "lumens" is a better guage of it.

Could someone explain, please?/ubbthreads/images/graemlins/confused1.gif

The reason I ask is that I'm looking at lights measured in lumens, and not 300,000 CP as in the Q-Beam type lights.

Thanks /ubbthreads/images/graemlins/grinning-smiley-003.gif

Barry
 
Wouldn't (shouldn't?) there be measure of lumens at a certain range, or ranges?

If the scientific measurement is direct from the source into a sphere at point blank range, how might that vary from light source to light source as a function of the design of that source to concentrate (or disperse) light at a distance?

Or shouldn't there be a measurement system that identifies something akin to field of view as with a scope? So maybe 100 lumens at orgin and 10 lumens at 50 feet distant for 75 feet FOV (10 lumens across the entire 75 foot spectrum). Obviously these numbers are just to make an example.

Some light applications are designed for flooding and others for spotting. Each has it's place. Measuring at the source probably puts the spot and flood lights on an equal footing for measurement at the source, but they are obviously not equal at 50 feet.
 
Candlepower is a rating of light output at the source, using English measurements.
Foot-candles are a measurement of light at an illuminated object. The amount of light measured from the source at one foot away.
Lumens are a metric equivalent to foot-candles in that they are measured at an object you want to illuminate.
Divide the number of lumens you have produced, or are capable of producing, by 12.57 and you get the candlepower equivalent of that light source.

Candlepower is a measure of light taken at the source-not at the target. Foot-candles tell us how much of that light is directed at an object we want to illuminate. You may see candle power expressed at candela.

Lighting terms are very confusing,
 
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