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Important lighting terminology explanation (Basic knowledge of Optics )
Commonly used terminology:
Luminous flux:
symbol is Φ, unit is lm, illustrated by the sum amount of light emitted by luminous body per second.
Light intensity:
symbol is I, unit is cd, illustrated by the luminous flux emitted by luminous body per solid angle in a specific direction.
Illumination intensity:
symbol is E, unit is lm/m2, illustrated by the luminous flux on the surface of object per square metre,which is irradiated by luminous body.
Brightness:
symbol is L, unit is cd/m2, illustrated by the luminous flux emitted by luminous body per solid angle and per square metre in a specific direction.
Light effect:
unit is lm/w, illustrated by the ability that electric light source converts electrical energy into light energy,and expressed by the luminous flux,which is divided by the power consumption.
Average life span:
unit is hour, referring to hours when more than fifty percent of a group bulbs are damaged.
Economic life span:
unit is hour, referring to certain hours the comprehensive beam output is reduced to, in considering the condition of both bulb damage and output beam attenuation.The ratio for outdoor lights is seventy percent,and for indoor lights, such as fluorescent lamp, is eighty percent.
Color temperature:
refers to the blackbody temperature when the color of blackbody is same as that of light emitted from lighting source. Blackbody temperature is higher, spectrum components include more blue,but less red. For example, incandescent light color is warm white, the color temperature is expressed as 2700K, while fluorescent lamp’s color temperature is 6000K.
Ps:Light color varies with the color temperature of light source.Color temperature below 3300K has a sedate atmosphere and warm feeling;color temperature between 3000K and 5000K,namely intermediate temperature,has a refreshing feeling;color temperature above 5000K has a cold feeling. But the best environment are created by different color from different lighting sources, Quote.
Color temperature > 5000K;color is cool (bluish white);cold atmosphere effect;
Color temperature between 3300 and 5000K; color is intermediate (white);good atmosphere effect;
Color temperature < 3300K;color is warm (reddish white);sedate atmosphere effect;
Light color：
Light color is the color temperature. It has three categories:Warm color,cold color and intermediate color from 3300K to 5000K.
Since light spectral composition vary, so even if the light color is same, the color rendering may be different.
Color rendering property:
In principle, artificial light should be same as natural light, so that human eyes can correctly tell things’ colors.Of course, it depends on the illumination position and purpose.The degree of object color displayed in light source is often called " color rendering index" ( Ra ).Color rendering properties of light sources is determined by color rendering index,whice indicates the deviation of object color in lighting than in standard light (sunlight ),namely the relations between true colors of things (the color) and displayed color in a standard light source. It can comprehensively reflect the color of light source. Determination of Ra value depends on comparison of 8 tested colors defined in DIN6169 standard in standard light source and tested light source. The smaller color is measured,the better color rendering property is tested. The Ra value of 100 light sources means displayed color of things is consistent in light of lamps to that in standard light source.
Two kinds of color rendering:
Faithful color rendering:to show object original color,you need to use high color rendering index (Ra) of light source,the value of whice is close to 100, the color you see will be the best.
Effect color rendering: to emphasize sharply the performance of certain color and beautiful life,you can use additive color method to enhance the color effect.
Ps:Low color temperature light source can make red more bright;
Intermediate color temperature light source can make blue feel cool;
High color temperature light source can make objects feel cold.
Light and radiation
Light is an electromagnetic wave radiation which cast on human eyes,and be converted into light by optic nerve.It’s part of spectrum that can be seen with the naked eyes. This type of radiation in the wavelength range from 360 to 830nm,and is only very small part of electromagnetic radiation spectrum. If temperature is much higher than that of 50Hz working temperature,it’ll result in a high color temperature white surface and better color rendering.
Lamp efficiency:
Luminaire efficiency ( also called light output coefficient ) is an important standard to measure the efficiency of lamp energy utilization, it is ratio between the output energy of lamp and that of built-in light source.
On the inner artificial lighting details, please refer to DIN5035 standard.
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