LED lighting related knowledge:

name              symbol       unit      unit       explain
luminous flux          ∮           lumen        lm          Every second light from the light of the sum total, namely luminous quantity.

Light intensity         I          candela       cd          luminous flux emitted by the luminous body in a particular direction per unit solid angle.
The illuminance         E            lux         lm/m2       luminous body irradiation in the irradiation target object unit area of the light flux. Direction is  divided                                                      into a horizontal or vertical, respectively to get the level of illumination, or perpendicular illumination.
Brightness              L            nits        cd/m2       luminous body in the specific direction per unit solid angle per unit area within a light flux
Life expectancy         H                                    Refers to the number of bulbs lighting to fifty percent of the number of damaged light hours

Economic life           H                                    Taking into account the situation of damage to the lamp, and the output beam attenuation, the integrated beamoutput is reduced to a certain proportion of the number of hours.

Color temperature
The color temperature based on absolute temperature K (Kelvin), but the standard black body (such as iron) is heated, the temperature rises to a certain level color from red → the light red → orange-red → blue → white → blue and white, gradually changing, using the changes in the characteristics of such a light color, and rendered light hue while the light color of the light source of a blackbody at a temperature, we will blackbody the absolute temperature at the time referred to as the color temperature of the light source, referred to a color temperature. The color temperature is an important indicator of the quality of evaluation of color, the color temperature is too high will give people a blunt, cold feeling, the color temperature is too low will give people a dim dull hair warm feeling. The color temperature of 3000K below, the light color reddish, to give people a warm feeling. The color temperature of more than 5000k color bias Blu-ray, giving a chilly feeling. More like 4000k color temperature typically subtropical, boreal people prefer less 4000k color temperature.

Light source color temperature
The Category color table correlated color temperature (K) light source
1 Warm <3300 incandescent quartz halogen lamps high pressure sodium
2 the middle of 3300 to 5300 fluorescent lamps metal halide
3 Cold> 5300 fluorescent mercury lamps, dysprosium lamp

The light color of the application
Warm light warm light color temperature below 3300K, warm light similar to incandescent lamps, more red light component, to give people a warm feeling of health and comfort. Use family residential quarters, hotels and other places or low temperature places.The cold white light, also known as neutral light, its color temperature between 3000 ~ 5300K, neutral color due to the soft light, the enjoyable feeling of comfort and serenity. Applies to shops hospital waiting room office hotel restaurant spaces.Cool light called day shade, its color temperature at 5300K light source close to natural light, bright feeling, people focused. Suitable for office conference room classroom drawing room design room library window display and other places.

CRI (Ra)
Called color light on the extent of the color of an object presented, that is, the degree of color fidelity, high color light source for better color reproduction and color we see is also closer to the natural color, low color rendering light on the color reassert poor. We see color deviation. CRI level lies in the spectral characteristics of the light, the blue-violet range of the wavelength of visible light in the range between 300nm to 780nm, which is seen in the spectrum, red, orange, PCV, if the source of light radiated out the colors of light contained similar proportions and natural light, our eyes see the color will be more realistic.

Source efficiency
Light efficiency based on its luminous flux emitted by dividing the ratio of the power consumption resulting.Source efficiency (lm / w) = lumens (lm) / Power Consumption (w) is the light emitted by each watt of electricity, and its value is higher the higher the efficiency of the light source, the light source efficiency is usually an important lighting considerations.

The basic concepts of lighting
Luminaire efficiency in the actual measurement conditions specified, the total luminous flux and the light source lamps emitted under lighting conditions bare light total light through ratio.The axial plane of the beam angle of the beam, the light intensity value is reduced to an angle corresponding to the peak of a certain proportion. The for general projection body, the beam l = 1/2Imax (Europe) or L = the angle of the beam within the range of 1/10Imax (USA).Uniformity refers to the light and dark contrast of indoor lighting, such as light and dark contrast is too large, will cause a lot of shadows. Fixture mounting height installation quantity arranged projection direction, and can not rely on experience to determine, according to the technical data of the lamps, aided design to achieve the most suitable illumination uniformityGlare uncomfortable visual conditions or observed decline in the ability of the brightness distribution or range of unreasonable allocation or space or time on the strong contrast. Generation of glare limit limit curve of the lamp, lamp brightness limit curve photometric test data provided by the lighting products. For direct lighting glare the installation height projection direction and background brightness according to the brightness of the lamps.
Technical indicators of the main light source

The type of light source         Light efficiency (Lm / W)            Color rendering index Ra              Temperature (K)         Average life (hours)

Incandescent                     15              100            2800        1000
Tungsten halogen lamps           25               100           3000        2000-3000
High-pressure mercury lamp       50              45-55        3300-4200     6000-15000
Ordinary fluorescent             70                70          Full range of      10000
Trichromatic fluorescent lamp    85-100          80-98          Full range of       15000
Compact fluorescent lamps          50-85           85            Full range of       8000-12000
A metal halide lamp              75-95           65-95     3000/4500/5600   6000-20000
High pressure sodium             120            23/60/85   1950/2200/2500    24000
Low pressure sodium              200                            1700          28000
Electromagnetic induction lamp   70              85           3000/4000       60000
LED lights                                                                                                     10 0000