The Color Temperature is the absolute temperature of a black radiator - reference light source - which emits the same color irradiation as a given light source measured in degrees Kelvin (K).
| Light Source | Color Temperature (K) |
| Blue sky | 10000 |
| Uniform overcast sky | 7000 |
| Average natural daylight | 6500 |
| HP mercury cool white lamp | 4000 |
| Fluorescent warm white lamp | 3000 |
| Halogen filament lamp | 3000 |
| GLS tungsten filament | 2700 |
| HP sodium lamp | 2050 |