This work comprised a technical comparison of the LED spectra to daylight spectra, a literature review addressing the effect of light spectra on humans, and a psychological study (between-subjects design) including subjective rating and performance tests with 83 persons in an office setting. Each participant was tested for one hour in one out of 4 lighting settings comparing Full Spectrum LEDs with conventional LEDs covering various aspects like visual comfort, naturalness, concentration, general glare rating, sleepiness, alertness and glossiness.
Main Findings:
• For 6 out of 19 comparisons in this study the results were statistically significant. The Full Spectrum LEDs have led to better results (e. g. higher naturalness, higher ratings of comfortability) than the standard LEDs. However, no short-time effects could be found for performance tests (attention, glossines perception, card sorting, fabric sorting). For none of the comparisons in the study the standard LEDs outperformed the Full Spectrum LEDs.
• In all LED conditions the participants felt more awake and alert at the end of the test session compared to the beginning. However, no difference was found between the four LED settings.
• The technical comparison revealed that due to complexity and costs until now the quality variety of daylight spectra was unaffordable for architectural lighting applications. On the opposite, nowadays unrivalled color rendering for different color temperatures can be provided by Full Spectrum LEDs. This offers the possibility to mimic daylight for artificial lighting solutions unlike before. New rating methods like TM-30-15 help to have a better understanding of the quality of spectra and should be established by the suppliers to enable professionals and non-professionals to qualify and specify lighting criteria.
• The literature review showed that until now there had been only little research on the impact of Full Spectrum LEDs on people’s perception, whereas there is a lot of psychological research on effects of natural and artificial light in general.
Conclusion and Outlook
The new light sources allow the lighting industry to come closer to daylight spectra than before, this at low costs. Investigating the impact on human perception, first psychological testing in office settings showed advantages of these Full Spectrum LEDs over conventional LEDs. The developed and used test material and results shall be used for further investigations on the perception for high demanding sectors like retail and museum and in dynamic settings like workplaces, hospitality industry, education and the health care sector. The lack of knowledge complementary to research on metabolism enhances the motivation to continue with future research in this field.
For further information, stay tuned! LED professional will soon be reporting a summary of this interesting research. Meanwhile you may contact Daniel Neves Pimenta at [email protected] or Lisa-Marie Wadle at [email protected] for more detailed information.
About Fraunhofer Institute for Building Physics IBP:
The Fraunhofer Institute for Building Physics IBP was founded in 1929 and is among the most experienced and established institutes of the Fraunhofer-Gesellschaft. A total of 250 employees work at the three branches in Stuttgart, and Holzkirchen. It has an annual budget of over 25 million euros, with approximately one third coming from industrial projects.
The primary focus of Fraunhofer IBP’s work is on research & development, testing, demonstration and consulting in the various specialist areas of building physics. – www.ibp.fraunhofer.de/en.html
