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Jung, B.; Inanici, M. |
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Title |
Measuring circadian lighting through high dynamic range photography |
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Journal Article |
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Year |
2018 |
Publication |
Lighting Research & Technology |
Abbreviated Journal |
Lighting Research & Technology |
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in press |
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in press |
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Keywords |
Instrumentation; Human Health |
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Abstract |
The human ocular system functions in a dual manner. While the most well-known function is to facilitate vision, a growing body of research demonstrates its role in resetting the internal body clock to synchronize with the 24-hour daily cycle. Most research on circadian rhythms is performed in controlled laboratory environments. Little is known about the variability of circadian light within the built and natural environments. Currently, very few specialized devices measure the circadian light, and they are not accessible to many researchers and practitioners. In this paper, tristimulus colour calibration procedures for high dynamic range photography are developed to measure circadian lighting. Camera colour accuracy is evaluated through CIE trichromatic (XYZ) measurements; and the results demonstrate a strong linear relationship between the camera recordings and a scientific-grade colorimeter. Therefore, it is possible to correct for the colour aberrations and use high dynamic range photographs to measure both photopic and circadian lighting values. Spectrophotometric measurements are collected to validate the methodology. Results demonstrate that measurements from high dynamic range photographs can correspond to the physical quantity of circadian luminance with reasonable precision and repeatability. Circadian data collected in built environments can be utilized to study the impact of design decisions on human circadian entrainment and to create guidelines and metrics for designing circadian friendly environments. |
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1477-1535 |
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GFZ @ kyba @ |
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1979 |
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Author |
Laurìa, A.; Secchi, S.; Vessella, L. |
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Title |
Visual wayfinding for partially sighted pedestrians – The use of luminance contrast in outdoor pavings |
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Journal Article |
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Year |
2018 |
Publication |
Lighting Research & Technology |
Abbreviated Journal |
Lighting Research & Technology |
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in press |
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in press |
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Keywords |
Lighting |
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An increase in the number of partially sighted people is one of the effects of population ageing. These people have great difficulties in gathering wayfinding information to move independently in an unfamiliar environment. Guide paths based on the luminance contrast between a strip and surrounding surfaces can be an effective device for mitigating these difficulties, but information provided by the scientific literature on guide paths cannot be usefully applied to the naturally coloured paving materials most commonly found in pedestrian urban spaces. This paper presents a simplified method for measuring the luminance contrast between a guide strip and its background using combinations of naturally coloured paving materials. |
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1477-1535 |
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GFZ @ kyba @ |
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1980 |
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Davidovic, M.; Djokic, L.; Cabarkapa, A.; Kostic, M. |
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Title |
Warm white versus neutral white LED street lighting: Pedestrians' impressions |
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Journal Article |
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Year |
2018 |
Publication |
Lighting Research & Technology |
Abbreviated Journal |
Lighting Research & Technology |
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in press |
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147715351880429 |
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Keywords |
Psychology; Security |
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The subjective impressions of pedestrians are necessary in order to decide on the appropriate colour of light to be used for street lighting. Therefore, a pilot project aimed to compare subjective evaluations of the sidewalk illumination under two street lighting installations, realised by LEDs of 3000 K (warm white) and 4000 K (neutral white), was recently conducted in Belgrade. Both installations had comparable sidewalk illuminances as well as other relevant photometric parameters. The evaluation was done through a questionnaire. A group of 139 (61 male and 78 female) respondents, all of them university students, was asked to grade both lighting installations for the sidewalk light intensity, the appearance of human faces, the colour of light and the colour rendering as well as the overall impression. According to the median values, the 3000 K LED installation was considered better than the 4000 K installation for all aspects assessed as well as the overall impression. Although the survey results convincingly showed a preference for 3000 K LEDs for this comparison, additional research is needed using a more representative sample of people and a wider range of locations before a definite conclusion can be reached. |
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1477-1535 |
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GFZ @ kyba @ |
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2045 |
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Author |
Bará, S.; Rodríguez-Arós, Á.; Pérez, M.; Tosar, B.; Lima, R.; Sánchez de Miguel, A.; Zamorano, J. |
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Title |
Estimating the relative contribution of streetlights, vehicles, and residential lighting to the urban night sky brightness |
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Journal Article |
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Year |
2018 |
Publication |
Lighting Research & Technology |
Abbreviated Journal |
Lighting Res & Tech |
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October 2018 |
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Keywords |
Remote Sensing; traffic; Roadway lighting |
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Under stable atmospheric conditions the brightness of the urban sky varies throughout the night following the time course of the anthropogenic emissions of light. Different types of artificial light sources (e.g. streetlights, residential, and vehicle lights) have specific time signatures, and this feature makes it possible to estimate the amount of brightness contributed by each of them. Our approach is based on transforming the time representation of the zenithal night sky brightness into a modal expansion in terms of the time signatures of the different sources of light. The modal coefficients, and hence the absolute and relative contributions of each type of source, can be estimated by means of a linear least squares fit. A practical method for determining the time signatures of different contributing sources is also described, based on wide-field time-lapse photometry of the urban nightscape. Our preliminary results suggest that, besides the dominant streetlight contribution, artificial light leaking out of the windows of residential buildings may account for a significant share of the time-varying part of the zenithal night sky brightness at the measurement locations, whilst the contribution of the vehicle lights seems to be significantly smaller. |
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Área de Óptica, Dept. Física Aplicada, Facultade de Óptica e Optometría, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Galicia, Spain. salva.bara(at)usc.es |
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SAGE |
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English |
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English |
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1477-1535 |
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GFZ @ kyba @ |
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2052 |
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Author |
Fotios, S.; Monteiro, A.L.; Uttley, J. |
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Title |
Evaluation of pedestrian reassurance gained by higher illuminances in residential streets using the day–dark approach |
Type |
Journal Article |
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Year |
2018 |
Publication |
Lighting Research & Technology |
Abbreviated Journal |
Lighting Research & Technology |
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Volume |
in press |
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Pages |
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Keywords |
Vision; Psychology; Security |
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A field study was conducted to investigate how changes in the illuminance affect pedestrian reassurance when walking after dark in an urban location. The field study was conducted in daytime and after dark in order to employ the day–dark approach to analysis of optimal lighting. The results suggest that minimum illuminance is a better predictor of reassurance than is mean illuminance. For a day–dark difference of 0.5 units on a 6-point response scale, the results suggest a minimum horizontal illuminance of approximately 2.0 lux. |
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1477-1535 |
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GFZ @ kyba @ |
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2159 |
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