# Candela (cd)

The candela is the SI unit of luminous intensity, or the power emitted by a light source in a particular direction. It is equal to one lumen per steradian.

The candela is often used to measure the brightness of light sources, such as lamps and LEDs. It is also used in photometry, for measuring the intensity of light emitted by objects.

One candela is approximately equal to the light emitted by a candle in a particular direction.

### Which unit is candela?

According to the International System of Units (SI), the candela is the SI unit of luminous intensity. It is defined as the luminous intensity of a source that emits monochromatic radiation of frequency 540 x 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

##### What is cd in illumination?

The Illumination Council (CD) is an international trade association representing the lighting industry. The Council’s mission is to promote the efficient use of energy and other resources through the application of quality lighting solutions. The Council is comprised of manufacturers, retailers, distributors, utilities, energy service companies, lighting designers, specifiers, architects, engineers, and other professionals involved in the lighting industry. How is the candela defined? The candela is the unit of luminous intensity in the International System of Units (SI). It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540×10^12 hertz, Kcd, to be 683 when expressed in the unit lumen per watt, which is equal to the value of the luminous intensity in candelas. Who invented candela? The term "candela" was first coined by Iván Rocha Fajardo, a Spanish physicist, in 1845. The International System of Units (SI) defines the candela as the SI unit of luminous intensity. It is equal to the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540×10^12 hertz and that has a radiant intensity in that direction of 1⁄683 watt per steradian.

#### What is the difference between candela and lux?

Candela is the SI unit of luminous intensity. It is defined as the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540 x 10^12 Hz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Lux is the SI unit of illuminance. It is defined as the illuminance on a surface when the surface is illuminated evenly by a point source of one candela.