The theory of color temperature?
What is color temperature? The color temperature of a light source can be defined as the temperature of an ideal black-body radiator that radiates light of a comparable color to that of the light source. This means that the color temperature is an indicator of the level of heat in the heat-up process within the lighting source at which an ideal black-body radiator can project a light in a certain color.
How do you measure color temperature? The measure of color temperature is Kelvin often expressed using the symbol K. Kelvin is defined as a unit of measure for temperature based upon an absolute scale. Overall, you can say Kelvin measures the color of the lighting. If the color temperature measures over 5000 K for a light source the light will be considered a cool color whereas if the color temperature measures between 2700-3000K the light will be considered a warm color. Cool light appears bluish white while warm light appears yellowish or reddish.
What does Color Temperature have to do with Human Centered Lighting?
Human Centric Lighting is the concept describing the connection between lighting and wellbeing, and it’s based on the mechanism of our circadian rhythm. The circadian rhythm is a sort of “internal clock” that keeps our body synchronised with the natural cycle of day and night: it ensures a peak of alertness and energy during the day and allows us to get to sleep during the night. Since we spend so much time indoors, artificial lighting can help keep our internal clock correctly synchronised through the correct selection of colour temperature. In fact, our circadian system is more sensitive to cooler light which helps us stay alert and focused, while it is less sensitive to warmer light. Having a higher colour temperature during the day (4000-5000K) and lower colour temperature during the night (2600K-3000K) would artificially recreate the natural evolution of daylight from sunrise to sunset .
How can we use this information to design spaces for people’s wellbeing? Well this is where LEDs come in to help. A benefit of using LEDs is being able to change the colour temperature of white light sources and control it – creating the best scenario for each situation. Let’s think about an office where no daylight is available: the light fittings could have a high colour temperature and 100% dimming during the day to improve the employees’ performance at work; the lighting levels and the colour temperature could gradually decrease during the afternoon, to “prepare” their brains to go home, relax and go to sleep.
What is the importance of Color Temperature for lighting designer?
Choosing the right colour temperature is crucial for a lighting designer when creating the perfect atmosphere and mood in a space, depending on what people are required to do in that space. We wouldn’t want a warm and soft atmosphere in a classroom, where students need to stay focused and alert. Yet we would want a comfortable and peaceful mood in a spa, where people want to rest and relax.
Using warm or cold lighting has a huge impact on the perception of space and the atmosphere and mood we intend to create, and it’s a factor that must be carefully considered along with lighting levels, colour rendering and directionality of lighting. You can see in the image below how a different colour temperature completely changes the perception of the room: in which would you rather rest after a long day? There’s not a completely “right” answer to this question, since preference on colour temperature is very subjective.
Here is a small guide of which color temperatures to use in various settings
- Light sources with a color temperature of 5000K: this is the color temperature of daylight. This type of light source is suitable in situations where you want the artificial light to look as “real” as possible. This color temperature fits in for example in galleries and ateliers.
- Light sources with a color temperature of 3000K: these light sources have a positive effect on humans when working a long time at the same place sitting still. Therefore, these light sources can with advantage be used in an office with, in the home, or as overall lighting someplace else.
- Light sources with a color temperature of 1200-2700K: This color temperature creates a warm and romantic ambiance and is therefore for example suitable in restaurants, cafes or anyplace else where intimacy and coziness are wanted.
LED lighting solutions are available both in cool and warm light and therefore you can easily find a cost-saving and energy-efficient LED solution that will fit your specific need perfectly. If you want to know more about color temperature or how LED can optimize your lighting you are always welcome to contact us at Linkind.com