Visual comfort oriented dynamic lighting evaluation of media facade:Based on comparative analysis of laboratory and urban environment
In the context of healthy cities,construction activities in many cities around the world have strengthened the protection towards public life and health.As an important component of urban infrastructure,urban lighting plays an important role in serving the public's night outdoor activities and improving the quality of the city's night scene.Health issues at nighttime were constantly discussed,but the detailed impacts of various newly developed lighting technology on public health is not comprehensive.As one of the important contents of nightscape,media facade has been applied in many cities,and its high brightness,multi-color,dynamic and other characteristics have aroused widespread discussions all over the world.As there are still problems such as insufficient basic research and unclear regulatory control requirements,media facade lighting have caused many issues related to visual comfort,aesthetic quality,etc.Combining the characteristics of displaying to supply the comfort assessment in dynamic scenes could provide scientific support for a more scientific and precise management and control towards media facade.This research were conducted in two steps:laboratory(indoor)and urban(outdoor)environment.The former step simulated the spatial characteristics of media facades in urban environments by building a set of experiments to evaluate the visual comfort in dynamic lighting scenes.The device consists of three parts including observer,observation box and lighting component.The most common scenes in cities were selected as experimental variables through network data,on-site surveys,including six light colors(3000K/4000K/5000K/red/blue/RGB),five dynamic durations(2s/4s/6s/8s/10s),and combined with laboratory's conditions,three observation distances(3m/6m/9m)were obtained.The subjective questionnaire in the experiment was based on SCL-90,four items including sector 17,39,57,and 78 in the"anxiety"dimension and two items of sector one and four in the"somatization"dimension were selected.Combined with research needs,an overall level of comfort evaluation item("overall comfort")is added in the questionnaire.In terms of physiological indicators,an eye tracker(aSee Glasses)was selected to collect eye movement data,including heat maps and eye movement trajectory maps.Data received was analyzed by R language to sort out the changing characteristics of visual comfort produced by subjective scales and eye movement data under key variables explain above.Laboratory conclusions were verified through urban scenes,11 media facades in city were selected and evaluated from three observation distances including near,medium and far through subjective scales.A comparative analysis of results of two scenes was conducted,which showed that the conclusions were consistent including:under the variable of distance,visual comfort and observation distance showed an inverse relationship.Under the variable of brightness,with an acceptable brightness level,the comfort increases as the brightness increases but when the brightness exceeds the acceptable range,higher brightness will cause a sharp decrease in comfort.On the other hand,the highest brightness is more likely to cause discomfort than the average brightness.Under the variable of dynamic duration,the relationship between comfort and dynamic duration is dominated by a direct proportion which is a longer dynamic duration will bring a more comfort feedback.Most subjects prefer dynamic durations of three seconds and above.Under the variable of light color,with an acceptable stimulation intensity,the impact of colored light on individuals varies significantly,while the level of comfort provided by white light is relatively uniform.When stimulation exceeds the acceptable range,colored light will cause stronger discomfort than white light.In the end,suggestions towards media facade design and management were put forward,as well as content to be improved in the future.The study designed a new experimental device that can provide support for subsequent variable related researches in media facade scenes.By comparing the conclusions of laboratory and city,an optimization method for media facade comfort evaluation is proposed,which can provide methodological reference for future related research.Through subjective evaluation and assessment of eye movement data,the applicability of the eye movement method in media facade scenes is demonstrated.The research conclusions can effectively improve the relevant research on key management and control indicators of media facades,which provide support for further studies,construction activities,and management,and promote the improvement of basic research on media facades.
media facadedynamic lightingcomfortevalutioneye movementsubjective scale
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