lm and cd

[emmazhou]

I have a silly question ，can anybody tell me what is the relationship about lumen and candela？

 

[tcphil]

The equations that compare them are not easy for most individuals. Here is a link that puts it and other light related terms in more plain English. If you want the equations, google is great.

Lumens, Footcandles, Candlepower, Measuring Light Output

 

[tursiops]

The equations that compare them are not easy for most individuals. Here is a link that puts it and other light related terms in more plain English. If you want the equations, google is great.

Lumens, Footcandles, Candlepower, Measuring Light Output

Except I think the author of that blog is actually confused. He says, "Lumens are a metric equivalent to foot-candles in that they are measured at an object you want to illuminate." That is not correct; that would imply that the farther away from the source your object is, the fewer lumens the light produces. He should be relating lumens to candlepower, not to foot candles.

In this case, wikipedia might be your friend.
https://en.wikipedia.org/wiki/Lumen_(unit)