The Colour Temperature
The surface of our sun has a temperature of about 5800 Kelvin (K), which corresponds approximately to the colour temperature one would observe from space. Due to the filtering effect of earth's atmosphere, the observed colour temperature shifts. On clear days it appears, depending on the sun and the prevailing weather conditions, more or less reddish. The colour temperature is lower. Scattered sky light has a much higher proportion of blue and therefore a much higher color temperature.
Some examples of colour temperatures (approx.):
- Candle: 1500K
- Incandescent lamp: 2400-2800K
- Halogen lamp: 2700-3300K
- Fluorescent light (cool white): 4000K
- Xenon lamp: 4500-5000K
- overcast sky: 6500-7500K
- LED: 2200-10000K
In photography considering the colour temperature is important for taking a subject in correct colours. The photo should correspond to the natural visual impression. Therefore converting filters for correcting the colour temperature have to be placed in front of the lens. In digital photography an often automatic white balance is performed prior.
continue reading --> Colour Rendering Index