Light related terms
- Luminous flux (lm):
Luminous flux is the measure of the perceived power of light. - Luminous intensity in candela (cd):
Light intensity emitted by a light source in a particular direction (luminous flux per solid angle). - Illuminance in lux (lx):
Used for light incident on a surface (luminous flux per unit of area).
Examples for illuminance:
> clear night of new moon: 0.01 lx
> full moon light: 0.24 lx
> street lights at night: 1 to 50 lx
> workplace lighting: 200 to 2.000 lx
> summers day with cloudy sky: 10.000 to 30.000 lx
> sunshine at noon: up to 100.000 lx - Luminance (cd/m3):
Photometric measure of the luminous intensity of the human eye. Luminance describes the amount of light that passes through or is emitted from a particular area.
Examples for luminance:
> sunshine regarding the position of the sun: 6.000.000 to 1.5 * 109 cd/m3
> mat bulb: 20.000 to 500.000 cd/m3
> fluorescent lamp 40W: 4.000 to 8.000 cd/m3
> fluorescent lamp 60W: 12.000 to 15.000 cd/m3
> white paper at 500 lx: 150 cd/m3
> blue sky: 5.000 cd/m3 and more
> full moon: 3.000 to 5.000 cd/m3 - Colour temperature in kelvin (K):
The light of lamps has an inherent colour, the so called light colour. It is conventionally stated through the colour temperature in kelvon (K).
Light colours of lamps:
warm white (ww) < 3.300 K (cosy comfortable atmosphere)
neutral white (nw) 3.300 to 5.300 K (functional atmosphere)
daylight white (dw) > 5.300 K
daylight white light is only suitable in rooms with an illuminance of 1.000 lx.
Terms
Lamps – luminaire – light
- Lamps:
No lamp, no light: "lamp" describes the technical design of an artificial light source. Examples: bulb, energy saving lamp, compact fluorescent lamp. The lamp is put into the luminaire, which spreads the light of the lamp and protects from glare. - Luminaire:
The entire light fitting in which the lamp is affixed, operated and protected is called the "luminaire". It protects the lamp, distributes and directs the light and guards against glare. - Light:
Light is referred to the to the visible radiation, which is a small segment of electromagnetic radiation. Electromagnetic radiation can also be gamma or infrared radiation, x-rays or UV radiation. The spectral range of light can be at a wavelength of 380 to 780 mm. Within this range the spectrum has various colours like violet, blue, green, yellow or red. Outside this range the human eye cannot "see" the radiation.
Light related terms
- Luminous flux (lm):
Luminous flux is the measure of the perceived power of light. - Luminous intensity in candela (cd):
Light intensity emitted by a light source in a particular direction (luminous flux per solid angle). - Illuminance in lux (lx):
Used for light incident on a surface (luminous flux per unit of area).
Examples for illuminance:
> clear night of new moon: 0.01 lx
> full moon light: 0.24 lx
> street lights at night: 1 to 50 lx
> workplace lighting: 200 to 2.000 lx
> summers day with cloudy sky: 10.000 to 30.000 lx
> sunshine at noon: up to 100.000 lx - Luminance (cd/m3):
Photometric measure of the luminous intensity of the human eye. Luminance describes the amount of light that passes through or is emitted from a particular area.
Examples for luminance:
> sunshine regarding the position of the sun: 6.000.000 to 1.5 * 109 cd/m3
> mat bulb: 20.000 to 500.000 cd/m3
> fluorescent lamp 40W: 4.000 to 8.000 cd/m3
> fluorescent lamp 60W: 12.000 to 15.000 cd/m3
> white paper at 500 lx: 150 cd/m3
> blue sky: 5.000 cd/m3 and more
> full moon: 3.000 to 5.000 cd/m3 - Colour temperature in kelvin (K):
The light of lamps has an inherent colour, the so called light colour. It is conventionally stated through the colour temperature in kelvon (K).
Light colours of lamps:
warm white (ww) < 3.300 K (cosy comfortable atmosphere)
neutral white (nw) 3.300 to 5.300 K (functional atmosphere)
daylight white (dw) > 5.300 K
daylight white light is only suitable in rooms with an illuminance of 1.000 lx.
Sources:
- Kleine Ergonomische Datensammlung, Publisher Federal Institute for Occupational Safety and Health, Author: Prof. Dr. W. Lange and Dr. A. Windel, Copyright by TÜV-Verlag GmbH, www.tuev-media.de
- licht.de, Fördergemeinschaft Gutes Licht, 2008, www.licht.de
- Illuminance is decreasing at diverging radiation in inverse ratio of square of the light source.