HBKCS - Basic Lighting Terms

Basic Lighting Terms

Lumen(lm):
Lumen is the international(SL)unit of luminous flux, a measure of overall light emitted by a light source.

Candela(cd):
Candela is the international(sl) unit of luminuous intensity,a measure of light emitted by a light source in a particular direction. Any given light source will have different luminous intensities in different directions considered. [candela = lumen/solid angle]

Beam Angle [Unit:degree]:
Beam angle is the angle between two directions for which the luminous intensity is 50% of the maxmum intensity as measured in a plan through the nominal beam centerline. Beam angle of a bulb gives an idea of how the light beam spreads away from the beam center.

LUX(lx):
	Lux is the international(SL)unit of illuminance, a measure of light arriving at a surface, 1 lumen per square foot equals 1 footcandle, while 1 lumen per square meter equals 1 lux. [lux = lumen/m2]

Color Temperature / Correlated Color Temperature(CCT):
A black-Body radiator will have a different color whent it is heated up to different temperatures(in kevin). The Temperature at which the heated black-body radiator matches the color of the light source is the color temperature of the light source.

Color Rendering Index(CR):

Color rendering index ranges from 0-100 ,measures a light source's ability to reproduce the color of various objects being lit by a reference light source, black body radiator(CRI=100)

Efficacy(lm/W):

Eifficacy is the effciency of a light source to concert electricity energy to light energy which is expressed in lumen output per unit power input (watt)
[Efficacy = lumen / wattage]

Design Life Time:

Design life time is the average life of a lighting product when it is operated at nominal lamp voltage,current and controlled working environment. Actual lamp life varies because of any different from those rating condition.

Dimmability:
Not all lighting prodcuts is designed for dimming function. Dimming a non-dimmable LED lighting product will cause un-predictable result and may affect the life time of the products. The below figure shows the typical input current variation while adjusting the DC voltage input to dimmable and non-dimmable product.

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