luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The unit of luminous intensity is the candela (cd), an SI base unit.A candle's luminous intensity is about 1cd. Domestic 100W incandescent luminous intensity of about 100cd.
2、Luminous flux:is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. Lumens=(radiant flux)(630lm per watt) 1lm=1cd?sr
Example: ordinary 40W fluorescent lamp luminous flux of 2200 lumens (100 hours)
The fluxof 1W power domestic incandescent light produced is about 12.5lm (4tlm)
3、 Illumination : the luminous flux per unit area. Therefore, the surface illumination is said to a measure of the degree of the surface to be be illuminated by light,short for E,in units of lux (Lx).
4、Brightness (the brightness):
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target.Unit: candela per square meter, symbol: cd / ㎡. Or nits (nt), Xi put (sb). 1nt Bennett = 1cd / m, 1sb Xi put = 10000nt Bennett.
light-emitting efficiency, that is, the ratio of light flux and power consumption. Unit: lm / W, symbol: lm / W
Luminous efficiency of incandescent bulbs normally about 7 ~ 20lm / W
Light effect of Straight fluorescent light is about 30 ~ 60lm / W, so the use of fluorescent lamps is morn engery saving than the use of incandescent lamps.