Lumen, Candela, Lux, Kelvin
The Lumen (symbol: lm).
The unit is SI (International System) (metric) lumen. It measures the strength of light as perceived by the human eye. The flux differs from radiant flux, measures the total power emitted light. To Lumen defined in relation to the Candela.lm = cd X sr (where sr = solid angle).
The candela (symbol: cd).
The unit is SI (International System) (metric) of the light intensity. It measures the strength of light emitted from a light source in a particular direction. A common candle emits roughly one candela.
cd = lm / sr (where sr = solid angle).
The Lux (symbol: lx).
The unit is SI (International System) (metric) of lighting and light show. It is used in photometry as a measure of the intensity of light falling on or crossing a surface per square meter, as perceived by the human eye.
lux = lm / m²
The Kelvin (symbol: K).
The range of colors as the cooler and warmer color temperature of the call and the scale used to measure the scale Kelvin. The cooler the colors, the higher the color temperature, while both shows warmer the color, the color temperature goes down. Because different materials, light bulbs emit a different color. This is measured in degrees Kelvin and practically shows how hot (in yellow) or cool (in blue) is the color emitted by a lamp.
Warm white, Soft white ≤ 3.000K
White, Bright White > 3.500K
Cool white > 4.000K
Daylight ≥ 5.000K
An incandescent bulb, the temperature is usually between 2700K and 3300K.