Luminous intensity measures the power of a light source in a specific direction. The SI unit is the candela (cd).
It supports candela (cd), millicandela (mcd), and candlepower (cp).
Candela measures intensity in one direction. Lumen measures total light output in all directions. A lamp rated at 800 lumens may have a different candela value depending on its beam angle.
A typical 10W LED bulb has a luminous intensity of about 100-150 candela in the direction it faces, with a total output of around 800 lumens.
Candela measures the intensity of a light source in a specific direction. Lux measures how much light falls on a surface at a given distance.
For a light source that emits uniformly in all directions, lumens = candela × 4π (steradians). For directional lights, the relationship depends on the beam angle.
Candlepower is an older unit equal to one candela. It was originally defined as the light output of a standard candle.