We all feel the psychological effects of light as we observe it, though this can be hard to describe.

The first characteristic of light that makes observing it possible is intensity or brightness.

The second characteristic, and the one we’ll be diving into in this article, is color temperature. Not to be confused with color – we’ll save that for another discussion.

Origins

Warning: Scientific Content

In the late 19th century, scientists such as Max Planck and Wilhelm Wien conducted experiments to understand the spectral distribution of electromagnetic radiation emitted by black bodies (graphite, carbon nanotubes, etc.) at different temperatures. They discovered that the color of light emitted by a black body shifts as its temperature changes.

Wilhelm Wien formulated Wien’s Displacement Law, which states that the wavelength of maximum emission (peak intensity) of black-body radiation is inversely proportional to the absolute temperature of the black body. In other words, as the temperature increases, the peak wavelength shifts to shorter (cooler) wavelengths, resulting in bluer light. Conversely, as the temperature decreases, the peak wavelength shifts to longer (warmer) wavelengths, resulting in redder light.

This relationship between the temperature of a black body and the color of the light it emits is the basis for the concept of color temperature. The Kelvin scale is used to quantify color temperature, with lower temperatures corresponding to warmer (redder) colors and higher temperatures corresponding to cooler (bluer) colors.

Application

The practical application of color temperature in lighting design emerged from this scientific understanding. By selecting light sources with specific color temperatures, we can create desired visual effects and atmospheres in various environments, from cozy and intimate to bright and invigorating.

Here’s a breakdown of how color temperature relates to the perceived color of light:

Warm Colors (Lower Kelvin Temperatures):

• Light sources with lower Kelvin temperatures appear warmer and more yellowish or reddish in color. They often evoke a cozy and intimate atmosphere. Examples include candlelight and incandescent bulbs.
• Typical color temperature range: 2000K to 3000K.

Neutral White (Mid-Range Kelvin Temperatures):

• Light sources with mid-range Kelvin temperatures produce a neutral white light that closely resembles natural daylight. This type of lighting is versatile and suitable for various applications, from residential to commercial settings.
  Typical color temperature range: 3500K to 4500K.

Cool Colors (Higher Kelvin Temperatures):

• Light sources with higher Kelvin temperatures emit cooler, bluish-white light. They are often associated with a crisp and energizing ambiance, similar to daylight on a clear day.
• Typical color temperature range: 5000K to 6500K.

Color temperature is particularly important in lighting design because it can influence the mood, atmosphere, and functionality of a space. For example:

• In residential settings, warmer color temperatures are often preferred in areas where relaxation and comfort are desired, such as bedrooms and living rooms.
• Cooler color temperatures are commonly used in task-oriented spaces like kitchens, offices, and retail environments, where clarity and focus are important.
• Outdoor lighting, such as streetlights and security lights, may vary in color temperature depending on factors like safety, visibility, and aesthetics. When choosing outdoor lighting, its also important to consider the “Dark Sky” factor.

When selecting lighting for a particular environment, it’s essential to consider the desired mood and functionality, as well as how the color temperature will interact with other elements in the space. Additionally, advancements in LED lighting technology have made it possible to adjust color temperatures dynamically, allowing for greater flexibility and customization in lighting design.