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Human responses to lighting based on LED (2016) (pdf) (research report)
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Human responses to lighting based on LED (2016) (pdf) (research report)

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Commissioned by CIBSE and the Society of Light and Lighting

LED technology is advancing rapidly and LEDs are being used for lighting in an increasingly wide variety of situations. Energy efficiency data are favourable, but there is a lack of data relating to the effects on health and lighting quality of the current generation of LED lighting solutions. This report seeks to directly address the areas where data are lacking based on up to date knowledge of human responses to light, and international exposure guidelines, applied to measurements taken of a range of LED lighting products currently on sale to the public, businesses and commissioners of outdoor lighting projects in the UK.

The health hazards and the positive impacts from lighting are not exclusive to LEDs, or even to artificial light. LEDs are just one of many technologies used to create artificial light. The importance of LEDs lies in their potential to provide increasingly ergonomically efficient lighting for many applications. The current definition of energy efficiency used in lighting is based on luminous flux. This definition does not always reflect the cost of producing the desired human responses, because it concentrates on only one of a range of effects of lighting on the human body, namely brightness.

It is also hard for energy efficiency measures to capture negative impacts or the changes in the demands on lighting over 24 hours. With a wide choice of lighting technologies, the appropriate measures, including energy efficiency measures, should be selected when deciding which solution and lighting technology is appropriate for any given situation. Inevitably, a balance must be struck between energy efficiency and competing factors. The aim is to describe the light output measured with respect to the main human responses to light as currently understood. The analysis is divided into three packages or work packages: Colour, Flicker and Spectrum.

A range of LED luminaires was tested, which is subdivided into three main categories: Domestic use (or home use), Office and commercial use, and Street lighting.

The report has been produced by Public Health England, PHE, for the Chartered Institution of Building Services Engineers(CIBSE), and the specialist professional body for lighting, the Society of Light and Lighting (SLL).



Executive Summary

1 Introduction
1.1 Colour
1.2 Flicker
1.3 Spectrum
1.3.1 Harm
1.3.2 Benefit
1.3.3 Effects on other species

2 Types of lamps and measurements
2.1 Design
2.2 Measurements
2.2.1 Spectral irradiance
2.2.2 Measurement positions for spectral irradiance
2.2.3 Modulation
2.2.4 Dimming and power

3 Colour package
3.1 Spectral irradiance and illuminance
3.2 Lamp colour
3.3 Colour quality and colour rendering
3.3.1 Colour Rendering Index and Colour Quality Scale 
3.3.2 Gamut area and TM-30
3.3.3 Spectral richness metrics FSCI and Spectral Entropy

4 Flicker package
4.1 Flickering light
4.2 Quantifying flicker
4.2.1 Percent flicker
4.2.2 Flicker index
4.3 Safety
4.4 Dimming and effects on flicker and energy efficiency

5 Spectrum package
5.1 Circadian rhythms and non-visual effects of light
5.1.1 Regulation of circadian rhythms and disruption of sleep by light
5.1.2 The role of artificial lighting
5.2 Blue light hazard and hotspots
5.3 LED street lighting
5.4 LED tablets and e-readers

6 Domestic-class LEDs – results
6.1 Batch variation
6.2 Colour rendering and CCT
6.3 Flicker and dimming
6.4 Power consumption and dimming
6.5 Ocular safety
6.6 Miscellaneous issues

7 Office-class LEDs – results
7.1 Batch variation
7.2 Colour rendering and CCT
7.3 Flicker and dimming
7.4 Power consumption and dimming
7.5 Ocular safety
7.6 Miscellaneous issues

8 Street-class LEDs – results
8.1 Batch variation
8.2 Colour rendering and CCT
8.3 Flicker
8.4 Power consumption
8.5 Ocular safety
8.6 Miscellaneous issues

9 Conclusions
9.1 Flicker
9.2 Spectrum
9.3 Power consumption and dimming 
9.4 Conclusion

10 References

Appendix A Flicker and other types of domestic lamp

Authors: L L A Price, M Khazova and J B O’Hagan

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