User acceptance studies for LED office lighting: Lamp spectrum, spatial brightness and illuminance

Abstract

In order to determine user acceptance for light-emitting diode (LED) office lighting, a full-scale experiment was conducted in two mock-up office rooms with different light spectra at two different illuminances. Six LED spectra and two fluorescent lamp spectra were used for the study. There were four spectra (three LED spectra and one fluorescent lamp spectrum) at a correlated colour temperature (CCT) of 4000 K and four spectra (three LED spectra and one fluorescent lamp spectrum) at a CCT of 6500 K. Forty observers evaluated the lighting environments under different spectra and rated the lighting environments sitting at a working desk and at a meeting table. The observers preferred the task illuminance of 500 lux to 300 lux and the CCT of 4000 K to 6500 K. The observers preferred the spectral power distributions (SPDs) under which they found the lighting environment to look brighter and more spacious. The observers' preferences showed that spatial brightness was affected by illuminances and SPDs. The lighting with a SPD having higher values of a reference-based metric (CQS Colour Preference Scale) and an area-based metric (CQS Gamut Area Scale or Gamut Area Index) was preferred most at a CCT of 4000 K. It was also found that the lighting with the fluorescent lamp was least preferred among the other SPDs at the CCT of 4000 K. The observers preferred both the simple and complex SPDs over fluorescent lamps at 4000 K in the office environment. It would be a good option to develop simple LED SPDs while maintaining the criteria of good lighting for an office environment.

Light dominates colour preference when correlated colour temperature differs

“…Another interesting finding is the negative correlation r between the average value and standard deviation of each trial. Such a result is consistent with previous studies 23, 51 , which indicates that when observers generally prefer certain lighting conditions, the distribution of their ratings will be concentrated, while if they generally dislike certain lighting conditions, the distribution will tend to be scattered.…”

A New Statistical Method for Ranking of Light Sources based on Subjective Points of View

“…, which serves the same rank (3,4,2,1,5) as AHP weights. We computed the normalized exponential weights by (5) and we obtained the vector (0.171, 0.188, 0.255, 0.237, 0.149), which is really close to *  , the maximum difference in the coordinates is 0.005. We can realize that this rank is slightly different from the one which was produced from all observations, actually the 2 nd object is before the 1 st one, but the equality of the two expectations is accepted in both cases.…”

“…Figure 1 shows the different cone sensitivities along the visible wavelength domain (380-780 nm). In order to evaluate the lighting quality of a light source under development, often, human visual experiments are used [4,5]. During the previous decade, this kind of visual experiments were carried out by using lighting booths with miniature models of real objects or small objects (e.g.…”

Visual discomfort associated with ceiling luminaires: Observations, trends and challenges 2009 -2018

“…More recent work by Islam and co-authors (a study which investigated observers preference for LED and fluorescent lighting with office-based tasks) showed a preference for LED over fluorescent lighting. The authors surmise that this preference was probably not related to glare but to the spectral power output of the lamps (the relative proportion of light wavelengths emitted by the lamp, which can affect the colour appearance of the light) (Islam et al, 2015).…”