What is Color Temperature?

Color temperature is a unit of measurement that represents the color components within light, expressed in Kelvin (K).

The Concept of Color Temperature

The concept of color temperature is based on “black body theory.” A pure black object can absorb all the heat that falls on it and can release all the energy generated by the heat in the form of “light.” When a black body is heated to different temperatures, it emits different colors. The temperature at which the black body emits light that matches the color of light emitted by a given light source is called the color temperature of that light source, or simply, the color temperature. For example, when a black body is heated to 3000K, it turns yellow, and we define the color temperature of a light source emitting yellow light as 3000K. Therefore, color temperature essentially refers to the color of the light.

Examples of Color Temperatures

Different light sources have different color temperatures. For instance, candlelight is orange-yellow, while moonlight is white. Different color temperatures of light sources can affect the colors of objects within their radiation range. Generally speaking, orange gives a warm feeling, while blue feels cold.

• 1700 K: Match light
• 1850 K: Candlelight
• 2800 K: Typical color temperature of tungsten (incandescent) lamps
• 3000 K: Halogen lamps and yellow fluorescent lights
• 3350 K: Studio “CP” lamps
• 3400 K: Studio lamps and photographic floodlights
• 4100 K: Moonlight, light yellow fluorescent lights
• 5000 K: Daylight
• 5500 K: Average daylight, electronic flash
• 5770 K: Effective solar temperature
• 6420 K: Xenon arc lamps
• 6500 K: Common white fluorescent lamps

The Impact of Color Temperature

The higher the color temperature (>5000K), the cooler the tone of the emitted light, providing a sense of coolness and depth. Lower color temperatures (<3000K) emit warmer tones, appearing warm and vibrant. Mid-range color temperatures (3000-5000K) tend to emit white tones, which feel calm and refreshing. The progression is generally from red to orange-red, yellow, yellow-white, white, and finally blue-white.

Daily Variations in Color Temperature

Throughout the day, the color temperature changes continuously. For example, the color temperature is blue before sunrise, orange after sunrise, white at noon, and yellow in the evening. These changes in sunlight color are mainly due to the reflection effect of the atmosphere, rather than significant changes in the sun’s temperature.