Ampere [A]

Ampere is the SI unit of electrical current. It is named after Andre-Marie Ampere (1775 - 1836), a french mathematician and physicist who considered as the father of electrodynamics.
Current [A] = [W] / voltage [V] 

Illumination - Lux [lx]

Illuminance decribes the amount of the luminous flux incident on a given area. It is the ratio of luminous flux to surface.
Sample: If a luminous flux of 1 lumen uniformly on 1 square meter, teh result is an illuminance of 1 lux. => 1LM/ 1m² = 1 Lux
The illuminance is regulated by variouse standards, e.g.:
Place of illumination Illuminance
Route for people 50 lx
Storerooms 50 - 100 lx
Workrooms 300 lx
Measuring rooms, offices 500 lx
Laboratory 500 - 750 lx
Dental / surgical environment 5.000 - 10.000 lx

Color Rendering Index (CRI)

The Color Rendering Index is the calculated rendered colour of an object. The higher the CRI (based on a sacle of 0 - 100) , the more natural the colors appear. Natural sunlight has a CRI of 100. LEDs have a CRI > 80.

Color temperature

The light color of a lamp is described by the color tempertaure in Kelvin (K). The conventional lamps have color temperatures in the order of magnitude of less than 3.300Kelvin (warm white), 3.300 to 5.300 Kelvin (neutral white) to about 5.300 Kelvin (daylight white). The color temperature of the color of a light source is determined by comparsion with the color of a black body.

This is an idealized body, for example made of platinum, which absorbs all light incident on it, so that the reflected radiation is zero therefore. If a black body is slowly heated it passes through a gamut of dark red, red, orange, yellow, white to light blue. The higher the temperature is, the whiter the color. The temperature of a black body , in which is to be determined with the light source color uniformity, is the correlated color temperature of the lamp.
Light source Color temperature
Red heat 500 K
Candle 1.500 K
Late evening sun before dawn 3.500 K
Fluorescent (Warm White) 4.000 K
Morning and evening sun 5.000 K
Midmorning and afternoon sun 5.500 K
Midday sun 5.500 - 5.800 K
Flash photo 6.000 K
Overcast 6.500 - 7.500 K
Fog 8.000 K
Blue sky in the shade 9.000 - 12.000 K
Nothern sky light 15.000 - 25.000 K

Life cycle

The life cycle of a LED refers to the time in which the light intensity has fallen to half of the initial value. LEDs are usually not simple break down, they become weaker and weaker during the life cycle. Since they do not have a hollow body as standard lamps, they cannot simply implode and are therefore insensitive to any kind of shock. The lifetime may range of a thousand hours up to more than 100.000 hours, that is a highly depndent on the semiconductor material and the operating temperatures. Thermal conditions will increase the defects in the crystal and these areas can not longer participate in the generation of light. This results in nonradiative transitions and the LED dims.