Natural light helps us to set our biological clock and affects our wellbeing. And artificial lighting can be used for the same purpose. The circadian rhythm can be stimulated with light, for example by using higher levels with cooler light until noon and then slowly return to lower levels and warm light in the afternoon.
Our preference for colour tempera-ture isn’t static, sometimes we want a cold, activating light, others a warm relaxing one. Tunable White is a new technology permitting the user to alter the colour temperature to what we prefer, via the luminaire itself or the complete lighting system. This kind of dynamic lighting can have a profound impact on the personal wellbeing, alertness and productivity, and the evolution of LEDs has initiated new research within the area.
The first in decades
Tommy Govén and Thorbjörn Laike, researchers in Light and Lighting at Lund University, have previously conducted two studies to investigate how humans are affected by ambient light. This time, the research team has focused on which colour temperatures that people prefer in a laboratory study when using LED lighting.
“A study of this type has only been made on fluorescent tubes. LED brings the question to the table once again”, says Tommy Govén.
How do people react to different colours – warm and cold light – and is there any difference between us? How do we perceive LED light at different level proportions between in the working area and the surroundings within the normal field of view? The study examines the preferred colour temperatures of participants aged 20 to 70 years. The evaluation is holistic and also includes luminance, glare and LED light flicker.
105 different light scenes
During the sessions the subjects could select their preferred colour temperature at different occasions from 21 individually fixed light scenes, easily controlled from a tablet. The intensity of lighting in the working plane was fixed at one of the seven steps in a scale from 50 – 1000 lux and the relation between the working area and the surroundings was set to either 5: 1, 2: 1 or 1:1.
“For each scenario, the subjects could choose between colour temperatures from warm to cold, from 2700 K to 6500 K. This meant we programmed a total of 105 different variations. Fagerhult has participated in the studies by contributing with development and programming of the different lighting scenes.”
Diffence between genders
The results will be presented at the 28th CIE Session in Manchester, June 28th to July 4th and will most certainly get attention.
“Most noticeably we see a clear difference between women and men. Women prefer a light that is slightly warmer, men prefer a light that is a bit colder”, reveals Tommy Govén.
“Of course, you cannot separate men and women to work in different rooms! But this knowledge can mean a lot when developing new lighting solutions with Tunable White in the future. With increased knowledge about the user’s preferences it is possible to create more accurate solutions and probably to reduce the range in colour temperature in working areas.”