Whats the difference/conversion factor?
It’s not a simple factor. The first complication is that candle power and watts aren’t the same thing expressed in different units. The second, and major complication, is that candle power (and the other variables of photometry) involve only energy that is visible to the human eye. Watts and lumens are similar units, watts being a measure of radiant energy flux, lumens being a measure of only the visible part of radiant energy flux. Watts are also a measure of power (volts x amperes) input into an electric lamp. I notice that physicists seem to avoid using the term “candlepower”, but I’m taking the unit of candle power to be the candle and 1 candle is 1 lumen per sterradian. (A steradian is a measure of solid angle; for example, the size of a flashlight beam in two dimensions – up/down and left/right. There are 12.57 steradians in a sphere, and since 1 radian=57.3 degrees, there are about 3283 square degrees per steradian.) Thus, a flashlight which produces 10 lumens spread out over a
