The luminous flux is the total light energy emitted by a light source to the surrounding space. The distribution of the luminous flux emitted by different light sources is different. The unit of luminous intensity is candela, symbol cd, it means that the luminous flux emitted by light source in a unit steradian solid angle (the angle formed by the object surface to the center light source). 1 cd = 1 lm / 1 sr (sr: solid angle steradian units).
The luminous intensity referred to as light intensity. 1cd or 1000mcd is the light of the monochromatic light source (frequency 540X1012HZ, wavelength of 0.550 microns), issued luminous intensity within the unit solid angle in a given direction (in the direction of the radiation intensity (1/683) W / steradian)).
The luminous intensity in a given direction is transmitted luminous flux (dΦ) of the light-emitting object in the solid angle divided by the solid angle (dΩ), that is luminous flux per unit solid angle. Its formula is:
The amount of symbols as I, the units is candela (cd) 1CD = 1lm/sr.
Sources: http://www.lednews.org/whats-luminous-intensity-definition/
