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.

BACKGROUND: In many western countries individuals will need to continue their professional careers beyond the current retirement age. This requires adaptation of the working conditions to compensate for age related visual changes. OBJECTIVE: The aim of this paper is to compile and structure knowledge concerning age related changes in visual and non-visual functions among older-age workers and to describe in what way these changes relate to light and work performance. METHOD: An overview of the literature was performed in PubMed and EMBASE concerning visual changes among elderly people, light, visual ergonomics and consequences at work. RESULTS: Visual conditions and lighting design have an impact on work performance in those over age 65 even if there are few studies available. Natural age related changes in the eyes or ocular diseases can result in reduced visual function and performance. Moreover, evidence of the importance of light and dark rhythms for circadian regulation is mounting; there are indications that the older-age population might need specific attention related to this issue. Finally, visual deteriorations might also, secondarily, induce strained postures and musculoskeletal symptoms, pain and injury. CONCLUSION: Age-related changes in the eyes and also ocular diseases among older-age people have an impact on well-being and work performance, and therefore call for reconsideration of their working conditions. Knowledge about how visual functions, light and ocular diseases is needed for work design and preventive actions.

Although there is a documented preference for daylighting over artificial electric lighting indoors, there are comparatively few investigations of behaviour and perception in indoor day-lit spaces at high latitudes during winter. We report a pilot study designed to examine the effects of static artificial lighting conditions (ALC) and dynamic daylighting conditions (DLC) on the behaviour and perception of two groups of participants. Each group (n = 9 for ALC and n = 8 for DLC) experienced one of the two conditions for three consecutive days, from sunrise to sunset. The main results of this study show the following: indoor light exposure in February in Stockholm can be maintained over 1000 lx only with daylight for most of the working day, a value similar to outdoor workers’ exposure in Scandinavia; these values can be over the recommended Melanopic Equivalent Daylight Illuminance threshold; and this exposure reduces sleepiness and increases amount of activity compared to a static artificial lighting condition. Mood and feeling of time passing are also affected, but we do not exactly know by which variable, either personal or group dynamics, view or variation of the lighting exposure. The small sample size does not support inferential statistics; however, these significant effects might be large enough to be of importance in practice. From a sustainability point of view, daylighting can benefit energy saving strategies and well-being, even in the Scandinavian winter.

We investigated whether light conditions have an impact on mental states, perception and perceived health symptoms in a controlled experiment. Twenty-eight participants, divided into groups of two, experienced the same room in two diffused light conditions (Daylight DL or static Artificial Light AL), which were experienced in a repeated measure design layout, controlled for order. Both light conditions offered a stimulus of at least 250 melanopic equivalent daylight illuminance (mEDI) lx, without a view. Participants were observed during different tasks, an individual reading session and a collaborative construction game session. The results show an effect of Light Condition on Mood and Pleasure, Mood was higher and Pleasure was better in the Daylight Condition. We did not find an effect of Light Condition on Arousal and on Sleepiness during the whole duration of the sessions, although results indicate lower Sleepiness in DL during the construction game session. Results indicate that the recommended mEDI levels can be maintained in a day-lit-only space during working hours (9:00 to 17:00 h) around the Equinox in Stockholm, 59°N. In the analysis limited to the DL sessions, we found that illuminance values, together with one measure of variation, are correlated to better pleasure. The current results show that the effects on Mood and Pleasure do significantly differ between Light Conditions but participants were not aware whether the source was artificial or natural. Thus we presume these effects could be even more relevant in a room with a view. 

We investigated whether differences in light levels and spectral properties have effects on motion. Twenty-two participants, divided into groups of two, experienced the same room in two diffused light conditions (Daylight DL or static Artificial light AL), which were experienced in a repeated measure design layout, controlled for order. Both light conditions offered a stimulus of at least 250 melanopic equivalent daylight illuminance (mEDI) lx, without a view. Participants were observed during an individual reading session and a collaborative construction game session. We measured the connectivity of the built structures; Activity by actigraphy; and we automatically extracted Motion Area and Quantity of Motion from video analysis. We found a correlation between mEDI values in the two Light Conditions (Daylight DL or Artificial light AL) and Activity; and a correlation between Light Condition and Motion Area. Diffuse daylight conditions were correlated with lower activity and less extended motion than a diffuse static condition, at levels recommended for office lighting and to ensure alerting responses. Indeed, static artificial light was found to be related to increased spatial exploration, which might indicate restlessness, and high mEDI to a more composed motion. Actigraphy measurements correlate with quantity of motion values, therefore the two methods provide comparable results. Results also show a high correlation between all photometric values in the daylight condition. These findings offer arguments for favoring diffuse daylight conditions in the design of places where it is desirable to avoid fidgetiness, like educational institutions, and to support composed motion, like medical institutions.