Research on Night Light Comfort of Pedestrian Space in Urban Park

The outdoor light environment significantly affects aspects of public psychological and physiological health. This study conducted experiments to quantify the effects of the light environment on visitor light comfort in urban park pedestrian space. Nine sets of lighting conditions with different average horizontal illuminance (2 lx, 6 lx, 10 lx) and colour temperatures (5600 K, 4300 K, 3000 K) were established virtual reality scenarios. Subjective light comfort was evaluated, and electroencephalogram (EEG) was measured on 18 subjects to comprehensively study the effects of different light environments on human light comfort. The results of the comprehensive evaluation showed that colour temperature had a very significant impact on subjective light comfort, with warm light being generally more favourable than cool light in enhancing human subjective light comfort. The results of the EEG analysis show that the average horizontal illuminance is an important factor in the level of physiological fatigue, and that physiological fatigue can be maintained in a superior state at an appropriate level of illuminance. Based on the results of both subjective and objective factors, a comprehensive analysis was carried out to propose a range of average horizontal illuminance (4.08 lx, 6.99 lx) and a range of colour temperature (3126 K, 4498 K) for the comprehensive light comfort zone in urban park pedestrian space.

VISUAL EFFECTS OF OBJECTS UNDER METAMERISM WITH MULTI-SPECTRAL LIGHT SOURCE

This study attempts to simulate the metamerism colour, and the guava was used as the target object. We design four sets of metamers with a correlated colour temperature of 4000K and an illuminance of 750lux. The light source was simulated in the LED cube. The subjects with convenience sampling observed the visual effects, including look delicious, colourful, and colour rendering of guava under metamerism, then analysed its relationship with CRI and CQS. The results showed that colour rendering and visual effects are not a positive relationship, and the effect of CQS is closer to the visual effects of the subjects. The results of this study can be used as a reference for light source lighting designers as a basis for improving lighting conditions. In the future, we can collect databases for the different objects with an optimized multi-spectral light source.

EFFECTS OF LUMINOUS COLOUR SHIFT Duv ON COLOUR PREFERENCE

Subjective experiment was carried out to investigate the combined effect on the colour preference of the interior style, correlated colour temperature (CCT) and duv. Twenty university age subjects evaluated all 28 conditions with 2 types of the interior style, 2 levels of the CCT and 7 levels of the duv. This paper reports the measured results of the chromaticity shift of the interior surface due to duv and the perception of the colour difference between the condition with any other duv and that with duv0. Subjective evaluation on the colour preference of the entire space related to the interior style, CCT and duv is also summarized. It is concluded that the acceptable range of duv to be classified as the same CCT should be reconsidered, considering colour preference.

THE EFFECT OF LIGHTING ENVIRONMENT ON FACIAL EXPRESSION PERCEPTION IN VIDEO TELECONFERENCING

In this study, we investigated whether manipulating the lighting environment in videoconferencing changes the readability of facial expressions. In the experiment, the participants were asked to evaluate their impressions of a video that simulated the situation in a videoconference. A total of 12 lighting conditions were used, including three colour temperature conditions and four lighting directions conditions. As a result of the factor analysis, four factors were identified: "Clarity," "Dynamism," "Naturalness," and "Healthiness." The results of ANOVA showed that placing the lighting in front was effective for all factors. And in all of the factors, it showed that lighting from the front was effective for the participants. In addition, while lower colour temperature decreased clarity, it improved naturalness and healthiness and was particularly effective when the lighting was placed in front of the subject.

Analysis of Tungsten Halogen Lamps Characteristics

The authors briefly review distinctions of tungsten halogen lamps (THL) and analyse the results of their own measurements of characteristics of three types of THL manufactured by Saransk lighting equipment plant LISMA. Rated power, luminous flux, and correlated colour temperature of lamps were measured. Relative measurement errors with consideration of possible technological errors for these products do not exceed 0.84 % for values of rated power and 0.29 % for values of correlated colour temperature in batches of 13 pcs. The analysis conducted shows that the technical level of development and production technology of Saransk lighting equipment plant LISMA provides high quality of THL.

Camera Colour Correction using Neural Networks

We demonstrate that a deep neural network can achieve near-perfect colour correction for the RGB signals from the sensors in a camera under a wide range of daylight illumination spectra. The network employs a fourth input signal representing the correlated colour temperature of the illumination. The network was trained entirely on synthetic spectra and applied to a set of RGB images derived from a hyperspectral image dataset under a range of daylight illumination with CCT from 2500K to 12500K. It produced an invariant output image as XYZ referenced to D65, with a mean colour error of approximately 1.0 ΔE*ab.

Effect of lighting illuminance and colour temperature on mental workload in an office setting

The mental workload of subjects was tested under different lighting conditions, with colour temperatures ranging from 3000 to 6500 K and illuminance ranging from 300 to 1000 lx. We used both psychological and physiological responses for evaluation. The former was based on NASA Task Load Index (NASA-TLX, NASA), and the latter was based on the electroencephalogram (EEG) P3b analysis of event-related potentials using the “oddball” paradigm experimental task. The results show that as illuminance increases, and the response time becomes longer with a colour temperature of 3000 K (P < 0.01). However, when the colour temperature is set at 6500 K, the response time becomes shorter as the illuminance increases (P < 0.01). P3b amplitudes were significantly affected by colour temperature (P = 0.009) and illuminance (P = 0.038) levels. The highest amplitudes occurred at 3000 K and 750 lx, which is consistent with the trend shown by the subjective scale. The data analysis of error rates is not significant. These results suggest that an office environment with a colour temperature of 3000 K and illumination of 750 lx, which exerts the lowest mental workload, is the most suitable for working. However, the interaction between colour temperature and illuminance in affecting the mental workload of participants is not clear. This work provides more appropriate lighting choices with colour temperature and illuminance to reduce people’s mental workload in office settings.

Evaluation of Visual and Nonvisual Levels of Daylight from Spectral Power Distributions Considering Orientation and Seasonality

The evaluation of both visual and nonvisual effects from the spectral power distribution (SPD) of outdoor light is critical in lighting design. The dome-light SPD characteristically changes continuously depending on the seasonality, orientation, altitude of the sun or hour of the day. Traditional photopic parameters, such as the illuminance, luminance or correlated colour temperature (CCT), have been widely studied, but presently, there is no melanopic measurement or evaluation method. This article discusses the processes involved in establishing a simple method to determine the SPD of daylight and solar radiation over the skydome in a location to accurately account for the effects of both photopic and circadian levels around a location. Once per month for one year, natural daylight was spectrally measured in the city of Zaragoza (Spain); radiometric and photometric characteristics were analysed by season; and circadian effects were calculated in terms of standard parameters described by the Commission International de l’Eclairage (CIE), factors recommended by normative and scientific backgrounds. Finally, we suggest that the best parameter is the melanopic versus photopic irradiance ratio, which achieves reliable results at simplifying and correlating calculations.