Candela (cd) is a luminous intensity unit within the Standard Unit System (SI). Described as the luminous intensity of a source emitting monochromatic radiation, in a given direction. In measurements involving artificial illumination the candela has replaced the traditional candle or lamp as a measure of luminous intensity and is often considered the “new candle.”
A typical wax candle radiates light at a luminous intensity of about one candela. If emission is covered by an opaque shield in certain areas, the emission will always be roughly one candela in the not blurred areas.
The word candela, for candle, is Latin.
- A typical candle emits light at a luminous intensity of about 1 cd.
- A compact fluorescent light bulb of 25 W sends out about 1700 lumens; if the light is radiated in all directions evenly, it would have an intensity of 135 cd.