Lumens & Colour Temperature

Lumens

Lumen (Im) is the unit of luminous flux, which is the measure of the total power emitted by the source.  This is a standard way of measuring the brightness of a light.  We normally would say 1 watt = 100 lumens.

Colour Temperature (Kelvin)

Colour temperature is a characteristic of visible light that has important applications in lighting. The colour temperature of a light source is the temperature of an ideal black-body radiator that radiates light of comparable hue to that light source.  The temperature is conventionally stated in units of absolute temperature, kelvin (K).   Higher colour temperatures (5,000 K or more) are called cool colors (blueish white); lower colour temperatures (2,700–3,000 K) are called warm colors (yellowish white through red).

Temperature

Source

1,700 K

Match flame

1,850 K

Candle flame

2,700–3,300 K

Incandescent light bulb

3,350 K

Studio "CP" light

3,400 K

Studio lamps, photofloods, etc.

4,100 K

Moonlight, xenon arc lamp

5,000 K

Horizon daylight

5,500–6,000 K

Typical daylight, electronic flash

6,500 K

Daylight, overcast

9,300 K

CRT screen