Quote Originally Posted by bractdoctor
... You cannot get more lumens from a bulb than it is rated. That is a mistake.
BDrx
I'm sorry we will have to disagree on that one. The lumen rating for all bulbs are measured by measuring the light intensity at a distance of 12". You can Google that. I did.

Light also obeys the same inverse-square law that gravity and sound wave intensity follows. If you move a bulb closer to an object, it gets more light (measured by lumens per sq. ft.).

Note the difference between "lumens" [the bulb's output at 12"] and "lumens per sq. ft." [the amount of light hitting an object at x distance away]. It's the Illuminance (amount of light per unit area) that counts, which is related to the lumen rating of a bulb and distance it is from an object.

If you move a bulb closer, the light gets more intense. Try this:
Foot-candle - Wikipedia, the free encyclopedia

To quote one piece from that link: "A source that is farther away casts less illumination than one that is close, so one lux is less illuminance than one footcandle. Since illuminance follows the inverse-square law ... <snip>"

Although you are correct in saying you cannot get more lumens from a bulb than it is rated for, I did not say you could. I said you can get more lumens/sq. ft. by moving the bulb closer.

Illuminance is what we used to call "brightness." It is a measure of lumens/sq. meter (also related to "lux" and "foot-candles" and "candellas").

Here is a link that explains illuminance: Luminance - Wikipedia, the free encyclopedia

PS: I have checked out many many sites already. Want an example? Go here:
lumens per sq ft./please halp!!! - Grasscity.com Forums