two different terminologies for the same thing
Lumens refers to the total amount of light a lighting apparatus emits. The higher the lumens value of a lighting device, the greater the area it illuminates. On the other hand, candela refers to the amount of light emitted by a lighting device in a particular direction.
The lumens unit does not consider the spread or divergence of the light being emitted by the device. But the candela value of a lighting device is concerned primarily with a focused beam of light. For instance, a standard fluorescent light device that emits a wide-spread beam can have a rating of 1,700 lumens and 135 candelas. But if the light emitted from this apparatus narrows and must shine within a 20-degree beam, then its candela value will increase to 18,000.
Candela is another word for candlepower. Candlepower measurement is from times when the candle was the primary source of illumination. The word candlepower was substituted with the term candela in 1948. One candela is approximately equal to the light that a candle with specific dimensions, produces. In this context it is worth mentioning that the term Maximum Beam Candlepower (MBCP) is often used to refer to the maximum intensity of the focused beam of light emitted usually from the center of the lighting device, which is usually the source, and projected in a single direction.
