No abstract

Short-wavelength (5500 nm) output of light sources enhances scene brightness perception in the low-to-moderate photopic range. This appears to be partially explained by a contribution from short-wavelength cones. Recent evidence from experiments on humans suggests that intrinsically photosensitive retinal ganglion cells (ipRGCs) containing the photopigment melanopsin might also contribute to spectral sensitivity for scene brightness perception. An experiment was conducted to investigate this possibility at two different light levels, near 10 lx and near 100 lx. Subjects provided forced-choice brightness judgments and relative brightness magnitude judgments when comparing two different amber-coloured stimuli with similar chromaticities. A provisional brightness metric including an ipRGC contribution was able to predict the data with substantially smaller errors than a metric based on cone input only.

A study of scene brightness perception was conducted to assess whether spectral sensitivity for scene brightness perception at low to moderate light levels ($3-110 lux) could be partially explained by a contribution of intrinsically photosensitive retinal ganglion cells (ipRGC). An experiment was conducted at two different light level ranges and using two different spectral power distributions. The results suggest an increase in short-wavelength spectral sensitivity as a function of increasing light level. The results also confirm that including ipRGC as well as cone photoreceptor input in scene brightness spectral sensitivity resulted in improved predictions compared to including either cone input only or rod as well as cone input.

In part because of the potential for high levels of glare from work zone illumination, recommendations for light levels from work zone illumination systems are substantially higher than for levels used along roadways in non–work zone locations. In a two-part study, requirements for work zone illumination light levels were assessed. First, levels for workers varying in age from 20 to 60 years were evaluated with the relative visual performance model, with and without the presence of visibility-reducing glare. Except for the smallest, lowest-contrast tasks performed by the older workers, an illuminance of 10 lx resulted in visibility well above the threshold even in the presence of glare, and an illuminance of 30 lx resulted in suprathreshold visibility for these conditions as well. The results of these computational analyses were largely confirmed in a full-scale, outdoor field demonstration attended by transportation agency engineers and highway contractors. Together, the findings suggest that when lighting systems provide sufficient glare control, light levels do not always need to be especially high to ensure adequate visibility for workers.

Light modelling, simulation, and photometric calculations are by now common tasks in the lighting design process. These practices contribute to the definition and comparison of suitable layout arrangements and help predict the impact of lighting devices. Those tasks demand the use of tools to support the simulation of different scenarios, the analyses of their pros and cons according to different criteria (e.g., health and safety, perception, aesthetics, energy consumption, and costs), and decision-making. Digital twins have emerged as relevant technologies to simulate and visualize different ``what-if'' scenarios associated with physical entities and processes. In this paper, we investigate the state-of-the-art research concerning the use of digital twins for supporting lighting analysis in the urban/outdoor context. We also present and discuss challenges and research opportunities related to the design, implementation, and validation of digital twins in this domain.

This paper describes our process in conducting research toward better understanding of the experience and perception of luminous colors in architectural contexts. Our intention is to contribute to a body of knowledge useful for designers by introducing a designerly way of working into an otherwise academic research approach. Luminous color influences our perception of form, space, and ambiance. The use of such color in architectural design has increased significantly over the past two decades, and with the advent of light-emitting diodes (LEDs), this trend is rapidly accelerating. However, LEDs produce luminous color in a different manner than traditional lighting systems. Identical-appearing colors can have different spectral compositions. Current work in health and perception sciences demonstrates that these different spectra can have distinct physiological and neurological effects. Current studies in different academic research fields into luminous color cannot be translated easily into a format relevant to architectural design. We therefore look to ways of studying the phenomenon using hybrid methods that would be consistent with design disciplines and goals. Efforts include structured experimental studies at a large scale to enable participants to experience different vantage points, peripheral perceptions, and free locomotion. The objective is to listen to the phenomenon and let it guide the research. We are following a process and developing research methods that are at a scale and in contexts appropriate to architectural applications. Although we borrow qualitative and quantitative methods from other disciplines for our individual studies, the overall goal is to remain fluid and open, to go beyond such established methods, structuring the endeavor as much as possible as a design process. Our approach is less structured than laboratory research, but targeted to be more ecologically and architecturally valid.

Light is the foundation of the visual perceptual process that initiates the evaluation of the surrounding area. Linked to various aspects and rhythms of the body, light connects us to both the natural environment and the interior space. The process of perceiving and assessing space for children and adults with different viewing heights and viewing perspectives as well as the role of light to facilitate this are the key elements of this study. The paper describes general lighting design strategies for kindergartens, specifically developed to create an environment that takes into account the children’s scale and cognitive processes. The objective was to discuss environments that support the child’s spatial perception along with shape and object recognition by means of lighting design, for example by creating distinct, well-placed shadows. The proposed strategies are informed by a literature review on the concepts and interrelations of light, human physiology and the perception of scale and space. In addition, our process also included visits to kindergartens to observe and analyse existing lighting as well as the use of simulation programs to test lighting scenarios and their patterns/distribution of light and shadow. The outcome described in this paper is a proposal and strategy to take into account children’s vantage points when designing lighting in kindergartens that is still open to practical interpretations in real-world sites.

Researchers and designers use the words “artificial” or “electric” to describe lighting products, design, or research related practices, and there appear to be differing opinions about which is the more appropriate term. Generally, there are challenges with a common use of language and vocabulary in interdisciplinary research and this might be also valid for design and research in lighting design across different disciplines. The authors were educated in opposing practices of using “electric” lighting vs “artificial” lighting; this started a discussion and the conceptualization of this article. The paper explores, summarizes and discusses through literature review and a survey the concepts described and conveyed by both terms in different disciplines. Interestingly we could find differences among and between disciplines and professional backgrounds. This might indicate that the education and nomenclature in the field influences the use of terms. We found a tendency to refer to light sources either in terms of the energy used to generate the light, e.g. electric light or gaslight, but also in terms of the effect that it evokes, e.g. candle light is defined natural. Generally, a common lighting glossary could be developed through continuous discussion and studies. As today’s complex questions are discussed in interdisciplinary teams, a common language might promote effective communication and stimulate sustainable solutions.