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Monitoring and rendering of visual and photo-biological properties of daylight-redirecting systems
Abstract
We previously developed a Camera-Like Light Sensor (CLLS) to record images using a novel High Dynamic Range (HDR) imaging vision sensor. The device was equipped with customized filters for adapting the camera’s spectral sensitivity to both photopic and circadian sensitivities. Here, we aim at investigating photometric and circadian metrics to assess and simulate the potential of light on non-visual functions. The CLLS was used to monitor luminance and circadian weighted radiance (Lec) over time in two test rooms, equipped with different daylight re-directing devices: venetian blinds (VB) and optical louver systems (OLS). Additionally, a computer simulation was performed for the two test rooms using the software RADIANCE: false colour images were used to demonstrate distribution of luminance and absolute values of Lec. Circadian weighted irradiance (Eec) was also computed at different positions corresponding to the gaze directions of a seated office worker. From our results, the VB provided overall higher illuminance compared to the OLS, but when a virtually seated observer was facing desk, the OLS provided larger circadian weighted irradiance in the afternoon. Our results illustrate the use of simulations for circadian metrics, which will be applicable in the future to predict the potential impact of light on non-visual functions for daylighting optimization in buildings.
... This last characteristic calls for spectrally resolved simulation workflows, or simply "spectral simulations" i.e., simulations in which light transport computations, material and light parameters span the entire visible spectrum and are defined based on N channels with N being more than three . According to this definition, most light simulation platforms (Ayoub, 2020;Ochoa et al., 2012) -including the ubiquitous Radiance rendering engine (Ward, 1987), are not proper spectral simulation tools, since they are usually based on a three-dimensional (e.g., RGB) color space, though they have already been used to discuss nonvisual responses to light (Acosta et al., 2017;Amirazar et al., 2018;Amundadottir et al., 2017;Amundadottir et al., 2013;Andersen et al., 2011;Borisuit et al., 2016;Konis, 2016;Pechacek et al., 2008). A framework based on aopic spectral sensitivity functions (Lucas et al., 2014) has since been adopted by the International Commission on Illumination (CIE) to describe the ability of optical radiation to trigger non-visual effects of light in humans (CIE, 2018). ...
A growing area of research focuses on the relationship between ocular light exposure and the non-visual responses. In order to accelerate research on this topic and improve building design, reliable spectral simulation tools are needed. This study aims at validating two of them, Lark and ALFA, by comparing their outcomes against daylight measurements. The goal is to assess how reliable these tools are in predicting spectral irradiance under different skies for indoor spaces. While spectral irradiance can in principle be simulated with a similar accuracy as for photopic values, there are some caveats in the current versions of both platforms.
... Daylighting in the room is significantly influenced by season, weather, and time of the day. Given these factors, the quantity of daylight entering the room can be controlled through manual shades, automated shades, blinds, or electrochromic windows [93][94][95][96]. Based on the adjustable function of colour temperature and the luminous existence of light-emitting diodes (LEDs), a lighting design with both visual and non-visual effects can be achieved with the combined control of daylight and artificial light by taking the requirements of users at different periods into consideration. ...
As a result of the desire to improve living standards, increasing attention is paid to creating a comfortable and healthy lighting environment that contributes to human health and well-being. It is crucial to understand the effects of environmental lighting regulation on humans' physical responses and mental activities. In this review, we focus on the scientific research on light-induced non-visual effects on humans, providing a systematic review of how the quantity of light, spectral changes, time of day, and duration have effects on the circadian rhythm, alertness, and mood based on eligible literature. The key findings are as follows: (1) The increase of illuminance and correlated colour temperature (CCT) at night were both positively associated with melatonin suppression, thus affecting the circadian rhythm. Meanwhile, a high CCT is conducive to the stimulation of positive mood. (2) Blue light and high CCT light at night induced delayed phase shift, and the objective alertness was reduced under the condition of lack of blue components. (3) High illuminance was positively correlated with subjective alertness during daytime, and increased the positive mood in the morning and decreased it in the afternoon. These findings serve as an important reference for stakeholders to optimise lighting in constructed environments to improve health and well-being considering the non-visual effects above and beyond visual performance.
... One of the problems to be solved before collecting data on spatial distribution of daylight SPD is a need to build a metrological system and establish a procedure and apply them for all assumed locations. There are many solutions that could be usedstarting from classical radiometric devices (Hernández-Andrés et al., 2001), through scanning (Knoop et al., 2015;Suárez-García et al., 2018) or non-scanning devices (Riechelmann et al., 2013;Tohsing et al., 2014), multispectral synthesis based on CCD camera (Nieves et al., 2005), HDR technique (Borisuit et al., 2016;Inanici, 2019a, 2019b, Inanici 2019b. Considering the need to use the same type of the measurement system justified by the comparability of the results (Bauer et al., 2018), a synchronized network of locations for the worldwide measurements campaign would be extremely expensive. ...
The evaluation of non-visual effects of light is a crucial topic in lighting design research and practice. Performing such analysis requires precise information about the spectral distribution of the tested light source. Assessing non-visual effects of daylight is complicated due to its spectral composition continuously changing, depending on many factors. Currently there are no available databases with spectral and spatial radiation patterns of the sky vault for locations spread all over the world, and an easy and common method to evaluate non-visual effects of daylight is lacking.
The goal of the paper is to provide a simple method to evaluate the non-visual potential of daylight, accounting for its variability. In order to present it, spectral measurements were conducted in two European cities in spring and summer. Horizontal and vertical illuminance toward the four cardinal directions was measured. Daylight variability was analysed in terms of illuminance, Correlated Colour Temperature (CCT) and Melanopic to Photopic (M/P) ratio. A comparison between the measured spectra and the CIE standard illuminants was performed and it was found that the usefulness of this method to evaluate non-visual effects of light in terms of M/P is adequate and provides reliable results. Therefore, a simple method to estimate the non-visual potential of daylight based on the use of D series of illuminants was presented and validated by comparing the results with the measured data. Using this method to calculate M/P always achieves RMSPEs below 6%.
... Non-visual effects of daylight are well recognized in the built environment research field and new approaches have been proposed for circadian daylight metrics [43], alertness, mood and rest cycles [62,13,12] and multi-criteria assessment of daylight-driven human responses [4] considering nonvisual health potential, visual interest and gaze behavior. Knoop et al. [42] reviewed human responses to daylight and identified current knowledge gaps. ...
The effects of indoor environmental conditions on human health, satisfaction, and performance have been the focus of research for decades. This paper reviews and summarizes the impact of lighting environment on task performance, specifically for the built environment audience. Existing studies included a variety of performance tests on cognitive performance and perception, visual acuity and reaction, memory, reasoning, and labor productivity. Illuminance, luminance ratio and correlated color temperature were found to affect performance in different ways, reflecting the impact of experimental techniques, conditions, performance evaluation methods used and data analysis methods. These were reviewed and categorized, with discussion on limitations related to sample size, modeling approach, carryover effects and other factors affecting individual differences in performance, with recommendations for future improvement. Although no universal conclusions can be made, in general, task performance seems to improve with higher illuminances, contrast ratios in the range of 7-11:1 (while always making sure that glare will not occur in the space) and higher correlated color temperature, while spectral tuning in the red or blue wavelengths has also shown positive effects. To obtain more generic evidence, future studies should be more consistent in terms of experimental procedures and overall light conditions, and also consider the effects of vertical illuminance, daylight provision/control, and outside views on task performance. Finally, studying performance with multi-factorial designs in a human-centered optimized manner (such as deploying variable lighting scenarios optimized for various tasks) can lead to deeper understanding of lighting effects on task performance, and ultimately to improved lighting design and operation in buildings overall.
... The application of these findings in the design of everyday built environments is in its early stages. Measurement devices that can be used to measure circadian lighting in built environments are evolving (Bierman et al. 2005;Borisuit et al. 2016;Jung and Inanici 2019), but field measurements are scarce (Figueiro et al. 2019;Konis 2018;Konis and Selkowitz, 2017). Given the challenges of long-term field data collections in existing spaces, and the limitations of testing design alternatives in full-scale mock-up models, simulation is a viable method to investigate the impact of design decisions. ...
The use of daylight in the built environment is often preferred to artificial light sources as its successful application can provide visual comfort and satisfaction along with the potential for significant energy savings. Exposure to daylight is also the primary source for stimulus that establishes a healthy day/night cycle in all living organisms. This is known as circadian rhythm. Newly discovered photoreceptors (intrinsically photosensitive retinal ganglion cells – ipRGC) within the mammalian eye, including humans, are specifically linked to the portion of the brain responsible for maintaining a healthy circadian rhythm. This discovery has led to a new subject area in the field of lighting design focused on controlling the spectrum of light that these photoreceptors are sensitive to.
Currently, work in the field of circadian lighting design is concentrated on the use of artificial light sources for circadian stimulus. This is largely due to the advent of the widespread use of LED technology, which has proven that it can be a significant source of light that can delay or advance the circadian clock. The use of daylight to provide circadian stimulus has been a given in this field of design, however, there has not been very much research into how the built environment affects our ability to effectively receive this stimulus from daylight.
In this research, the groundwork is established to start to create a set of guidelines to help architects and designers maximize the potential for daylight to provide circadian stimulus at the earliest stages of a project. This is accomplished through a series of lighting simulations that explore and test various architectural parameters that affect daylight-driven circadian lighting, with simultaneous consideration given to photopic lighting availability and visual comfort. The architectural parameters tested in this study included window head height, building orientation, shading devices, visual obstructions to the sky, and room depth. The results show that informed design decisions could maximize circadian potential in a given space, while achieving visually satisfactory luminous environments.
... Under clear sky conditions, the OLS was found to enhance the ceiling luminance, likewise provide a more uniform luminance distribution over the ceiling surface. Similarly, in a recent studyof Borisuit et al. (2016), a novel Camera-Like Light Sensor (CLLS) was used to monitor luminance ...
Higly glazed facades has been increasing with the intention of more daylight gain in buildings. However, more daylight may not always bring more satisfaction considering many factors that influence daylighting quality. Uncontrolled daylight brings visual and thermal problems which end up with negative interactions with user comfort. Library spaces in which different task activities are performed simultaneously need to be well designed in terms of daylight performance, thus the user satisfaction could enhance.
This thesis particularly focuses on the optimization of visual performance in an academic library with a new layout arrangement and a light shelf-reflective louver system. One of the reading rooms of Izmir Institute of Technology Library was chosen as a reference case, where the instrumental monitoring of existing daylighting conditions was performed. The reference case was then analyzed with daylight simulation tool, so that the outcomes would later be used for the performance testing of the new proposals. Luminance patterns and illuminance distribution of different points were evaluated in terms of visual performance recommendations. A new layout arrangement and light shelf-reflective louver system were proposed respectively in accordance with the deficiencies of simulation results. Ultimately, daylight performance of the library was significantly improved regarding illuminance and luminance based distribution.
Despite a diminution in average illuminance due to the dramatic decrease of excessive amount of daylight near the window, the big picture gives the clues on how a simple layout change and a daylighting system can make enhancement on the visual performance of a library reading room.
Light has been shown to have a non-visual impact on the biological aspects of human health, particularly on circadian rhythms. Building windows are a potential means of regulating daylight conditions for circadian health and well-being. As a result of advancements in window and glazing technologies and variations in outdoor solar/ sky conditions, understanding daylight's spectral characteristics, which pass through building window systems, is complex. Therefore, a systematic review and summary of the knowledge and evidence available regarding windows' impact on human circadian health is necessary. This study provides an overview of research in this domain, compares approaches and evaluation metrics, and underscores the importance of window parameters' influence on circadian health. Published studies available on various online databases since 2012 were evaluated. The findings of this study define a holistic approach to the melanopic performance of windows and provide an overview of current knowledge regarding the effect of windows on circadian health. Additionally, this work identifies future research directions based on the studies reviewed. This research contributes to the growing body of knowledge on the impact of windows on circadian health, which has implications for the design and construction of buildings in ways that support indoor human health and well-being from the circadian light adequacy perspective.
This paper presented a symmetric prismatic daylight collector to collect daylight for the natural light illumination system. We analyzed the characteristics of the emerging light when the parallel light beam illuminate on the horizontally placed symmetric prismatic daylight collector. The ratio of the relative intensities of collected daylight that emerging from each surface of the daylight collector shown that the ratio is varied with the incident angle during a day. The simulation of the emerging light of the daylight collector shown that the ratio of emerging light is varied with the tilted angle when sunshine illuminated on a symmetric prismatic daylight collector which was not placed horizontally. The integration of normalized intensity is also varied with the tilted angle. The symmetric prismatic daylight collector with the benefits of reducing glare and dividing intensity of incident daylight, it is applicable to using in the natural light illumination system and hybrid system for improving the efficiency of utilizing of solar energy.
Chronobiology is the science of biological rhythms, more specifically the impact of the 24-hour light-dark cycle and seasonal changes in day length on biochemistry, physiology and behaviour in living organisms. In the last 20 years, chronobiology has moved from its somewhat obscure scientific corner to a high-impact mainstream research field, notably with respect to the discovery of clock genes and peripheral oscillators ? and a novel photoreceptor in the eye with specific input to the circadian system. Key discoveries in human chronobiology are related to the impact of light. Recognition of the so-called ?biological effects of light? by lighting manufacturers has led to interest in developing new lighting systems that integrate this knowledge. Is it time for the medical mainstream to take notice of what neuroscientists know about the body clock? And is it also time for architects to do so? These questions were explored at a symposium for architects, lighting engineers and manufacturers, initiated by Society for Light Treatment and Biological Rhythms (www. sltbr.org), in order to develop approaches to bridge the gap between these disciplines.
This paper documents the spectral and spatial performance characteristics of two new versions of the Daysimeter, devices developed and calibrated by the Lighting Research Center to measure and record personal circadian light exposure and activity levels, and compares them to those of the Actiwatch Spectrum (Philips Healthcare). Photometric errors from the Daysimeters and the Actiwatch Spectrum were also determined for various types of light sources. The Daysimeters had better photometric performance than the Actiwatch Spectrum. To assess differences associated with measuring light and activity levels at different locations on the body, older adults wore four Daysimeters and an Actiwatch Spectrum for five consecutive days. Wearing the Daysimeter or Actiwatch Spectrum on the wrist compromises accurate light measurements relative to locating a calibrated photosensor at the plane of the cornea.
Light is a potent stimulus for regulating circadian, hormonal, and behavioral systems. In addition, light therapy is effective for certain affective disorders, sleep problems, and circadian rhythm disruption. These biological and behavioral effects of light are influenced by a distinct photoreceptor in the eye, melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs), in addition to conventional rods and cones. We summarize the neurophysiology of this newly described sensory pathway and consider implications for the measurement, production, and application of light. A new light-measurement strategy taking account of the complex photoreceptive inputs to these non-visual responses is proposed for use by researchers, and simple suggestions for artificial/architectural lighting are provided for regulatory authorities, lighting manufacturers, designers, and engineers.
This paper investigates the formulation of a modelling framework for the non-visual effects of daylight, such as entrainment of the circadian system and maintenance of alertness. The body of empirical data from photobiology studies is now sufficient to start developing preliminary non-visual lighting evaluation methods for lighting design. Eventually, these non-visual effects have the potential to become a relevant quantity to consider when assessing the overall daylighting performance of a space. This paper describes the assumptions and general approach that were developed to propose a modeling framework for occupant exposure to non-visual effects of light, and presents a novel means of visualising the ‘circadian potential’ of a point in space. The proposed approach uses current outcomes of photobiology research to define – at this point static – threshold values for illumination in terms of spectrum, intensity and timing of light at the human eye. These values are then translated into goals for lighting simulation, based on vertical illuminance at the eye, that – ultimately – could become goals for building design. A new climate-based simulation model has been developed to apply these concepts to a residential environment. This will be described in Part 2 of this paper.
A new capability that enables annual simulation of optically complex fenestration systems has been added to Radiance. The method relies on bidirectional scattering distribution function (BSDF) input data, which are used in an efficient matrix calculation to compute time-step performance given TMY data. The objective of this study was to explain the value of this capability to designers and developers of innovative daylighting systems and to demonstrate its speed and accuracy via comparisons of simulated to measured illuminance data for a daylight-redirecting optical louver system. The method was shown to provide valid results that accurately replicate real-world conditions with an absolute mean bias error below 13% and a root mean square error below 23%. Routine application of this new capability will not be hindered by slow computational speed for illuminance calculations. Instead, the capability will be dependent on the availability of BSDF data for daylighting, shading and fenestration systems.
This paper introduces a new paradigm to assess daylight in buildings called ‘useful daylight illuminance’, or UDI. The UDI paradigm preserves much of the interpretive simplicity of the conventional daylight factor approach. In contrast to daylight factors however, UDI is founded on an annual time-series of absolute values for illuminance predicted under realistic skies generated from standard meteorological datasets. Achieved UDI is defined as the annual occurrence of illuminances across the work plane where all the illuminances are within the range 100-2000 lux. These limits are based on reports of occupant preferences and behaviour in daylit offices with user-operated shading devices. The degree to which UDI is not achieved because illuminances exceed the upper limit is indicative of the potential for occupant discomfort. The relation between achieved UDI and annual energy consumption for lighting is examined.
The application of lighting simulation techniques for daylight illuminance modelling
in architectural spaces is described in this thesis. The prediction tool used for all the
work described here is the Radiance lighting simulation system.
An overview of the features and capabilities of the Radiance system is presented.
Daylight simulation using the Radiance system is described in some detail. The
relation between physical quantities and the lighting simulation parameters is made
clear in a series of progressively more complex examples. Effective use of the interreflection
calculation is described.
The illuminance calculation is validated under real sky conditions for a full-size office
space. The simulation model used sky luminance patterns that were based directly
on measurements. Internal illuminance predictions are compared with
measurements for 754 skies that cover a wide range of naturally occurring
conditions. The processing of the sky luminance measurements for the lighting
simulation is described. The accuracy of the illuminance predictions is shown to be,
in the main, comparable with the accuracy of the model input data. There were a
number of predictions with low accuracy. Evidence is presented to show that these
result from imprecision in the model specification - such as, uncertainty of the
circumsolar luminance - rather than the prediction algorithms themselves.
Procedures to visualise and reduce illuminance and lighting-related data are
presented.
The ability of sky models to reproduce measured sky luminance patterns for the
purpose of predicting internal illuminance is investigated. Four sky models and two
sky models blends are assessed. Predictions of internal illuminance using sky
models/blends are compared against those using measured sky luminance
patterns. The sky model blends and the Perez All-weather model are shown to
perform comparably well. Illuminance predictions using measured skies however
were invariably better than those using sky models/blends.
Several formulations of the daylight coefficient approach for predicting time varying
illuminances are presented. Radiance is used to predict the daylight coefficients
from which internal illuminances are derived. The form and magnitude of the daylight
coefficients are related to the scene geometry and the discretisation scheme.
Internal illuminances are derived for four daylight coefficient formulations based on
the measured luminance patterns for the 754 skies. For the best of the formulations,
the accuracy of the daylight coefficient derived illuminances is shown to be
comparable to that using the standard Radiance calculation method.
The use of the daylight coefficient approach to both accurately and efficiently predict
hourly internal daylight illuminance levels for an entire year is described. Daylight
coefficients are invariant to building orientation for a fixed building configuration. This
property of daylight coefficients is exploited to yield hourly internal illuminances for
a full year as a function of building orientation. Visual data analysis techniques are
used to display and process the massive number of derived illuminances.
Environmental light synchronizes the primary mammalian biological clock in the suprachiasmatic nuclei, as well as many peripheral clocks in tissues and cells, to the solar 24-hour day. Light is the strongest synchronizing agent (zeitgeber) for the circadian system, and therefore keeps most biological and psychological rhythms internally synchronized, which is important for optimum function. Circadian sleep-wake disruptions and chronic circadian misalignment, as often observed in psychiatric and neurodegenerative illness, can be treated with light therapy. The beneficial effect on circadian synchronization, sleep quality, mood, and cognitive performance depends on timing, intensity, and spectral composition of light exposure. Tailoring and optimizing indoor lighting conditions may be an approach to improve wellbeing, alertness, and cognitive performance and, in the long term, producing health benefits.
We describe two methods which rely on bidirectional scattering distribution functions (BSDFs) to model the daylighting performance of complex fenestration systems (CFS), enabling greater flexibility and accuracy in evaluating arbitrary assemblies of glazing, shading, and other optically-complex coplanar window systems. Two tools within Radiance enable a) efficient annual performance evaluations of CFS, and b) accurate renderings of CFS despite the loss of spatial resolution associated with low-resolution BSDF datasets for inhomogeneous systems. Validation, accuracy, and limitations of the methods are discussed.
2005. The Daysimeter: a device for measuring optical radiation as a stimulus for the human circadian system. Measurement Science and Technology 16: 2292-2299. Abstract Optical radiation incident on the human retina stimulates vision as well as provides time-of-day information to the brain's circadian clock. The visual and circadian systems respond very differently to optical radiation. A device, the Daysimeter, was developed and tested to help progress toward a system of circadian dosimetry. The Daysimeter is a light-weight, head-mounted device that records radiation exposure estimates for both the visual and circadian systems, and is specifically designed for field use. In addition to logging spectrally weighted radiation measurements, it records head position and motion to be utilized as a representation of human circadian activity. This manuscript provides background on the differences between radiation for the visual and circadian systems, as well as a description of the development and testing of this prototype device.
In sighted humans, light intensity, timing, exposure duration, and spectral composition of light are important to entrain the endogenous circadian pacemaker to the 24-h day-night cycle. We tested the impact of two realistic office lighting conditions during the afternoon on subjective sleepiness, hormonal secretion, and cognitive performance in the early evening hours. Twenty-nine young subjects came twice and spent 8 h (12:00-20:00) in our laboratory, where they were exposed for 6 h to either artificial light (AL) or to mainly daylight (DL). In the early evening, we assessed their salivary cortisol and melatonin secretion, subjective sleepiness, and cognitive performance (n-back test) under dim light conditions. Subjects felt significantly more alert at the beginning of the evening after the DL condition, and they became sleepier at the end of the evening after the AL condition. For cognitive performance we found a significant interaction between light conditions, mental load (2- or 3-back task) and the order of light administration. On their first evening, subjects performed with similar accuracy after both light conditions, but on their second evening, subjects performed significantly more accurately after the DL in both n-back versions and committed fewer false alarms in the 2-back task compared to the AL group. Lower sleepiness in the evening was significantly correlated with better cognitive performance (p < .05). In summary, even short-term lighting conditions during the afternoon had an impact on cognitive task performance in the evening. This rapid effect was only distinguishable on the second day of training, when a difficult task had been sufficiently practiced.
Light exposure can cascade numerous effects on the human circadian process via the non-imaging forming system, whose spectral relevance is highest in the short-wavelength range. Here we investigated if commercially available compact fluorescent lamps with different colour temperatures can impact on alertness and cognitive performance.
Sixteen healthy young men were studied in a balanced cross-over design with light exposure of 3 different light settings (compact fluorescent lamps with light of 40 lux at 6500K and at 2500K and incandescent lamps of 40 lux at 3000K) during 2 h in the evening.
Exposure to light at 6500K induced greater melatonin suppression, together with enhanced subjective alertness, well-being and visual comfort. With respect to cognitive performance, light at 6500K led to significantly faster reaction times in tasks associated with sustained attention (Psychomotor Vigilance and GO/NOGO Task), but not in tasks associated with executive function (Paced Visual Serial Addition Task). This cognitive improvement was strongly related with attenuated salivary melatonin levels, particularly for the light condition at 6500K.
Our findings suggest that the sensitivity of the human alerting and cognitive response to polychromatic light at levels as low as 40 lux, is blue-shifted relative to the three-cone visual photopic system. Thus, the selection of commercially available compact fluorescent lights with different colour temperatures significantly impacts on circadian physiology and cognitive performance at home and in the workplace.
Un bâtiment construit doit être avant tout confortable et sain. C'est en fait sa raison d'être. Il doit protéger les occupants de l'environnement extérieur, assurer un climat agréable à l'intérieur et fournir des services tels que communications et transports. L'objectif principal de cet ouvrage est de faciliter l'expression et la création artistiques de bâtiments de haute qualité environnementale. L'auteur démontre qu'au moyen d'une planification intelligente et multidisciplinaire, il est parfaitement possible d'assurer à la fois une bonne qualité architecturale, un excellent environnement intérieur et une très faible consommation d'énergie. A l'aide de modèles provenant de la physique et de la technique du bâtiment, il développe des méthodes permettant de garantir un bon confort thermique, une bonne qualité de l'air, une protection efficace contre les effets de l'humidité, notamment les moisissures, un éclairage optimal et en environnement acoustique agréable.
Bright artificial light suppressed nocturnal secretion of melatonin in six normal human subjects. Room light of less intensity,
which is sufficient to suppress melatonin secretion in other mammals, failed to do so in humans. In contrast to the results
of previous experiments in which ordinary room light was used, these findings establish that the human response to light is
qualitatively similar to that of other mammals.
This work demonstrates that transgenic mice lacking both rod and cone photoreceptors (rd/rd cl) retain a pupillary light reflex (PLR) that does not rely on local iris photoreceptors. These data, combined with previous reports that rodless and coneless mice show circadian and pineal responses to light, suggest that multiple non-image-forming light responses use non-rod, non-cone ocular photoreceptors in mice. An action spectrum for the PLR in rd/rd cl mice demonstrates that over the range 420-625 nm, this response is driven by a single opsin/vitamin A-based photopigment with peak sensitivity around 479 nm (opsin photopigment/OP479). These data represent the first functional characterization of a non-rod, non-cone photoreceptive system in the mammalian CNS.
The photopigment in the human eye that transduces light for circadian and neuroendocrine regulation, is unknown. The aim of this study was to establish an action spectrum for light-induced melatonin suppression that could help elucidate the ocular photoreceptor system for regulating the human pineal gland. Subjects (37 females, 35 males, mean age of 24.5 +/- 0.3 years) were healthy and had normal color vision. Full-field, monochromatic light exposures took place between 2:00 and 3:30 A.M. while subjects' pupils were dilated. Blood samples collected before and after light exposures were quantified for melatonin. Each subject was tested with at least seven different irradiances of one wavelength with a minimum of 1 week between each nighttime exposure. Nighttime melatonin suppression tests (n = 627) were completed with wavelengths from 420 to 600 nm. The data were fit to eight univariant, sigmoidal fluence-response curves (R(2) = 0.81-0.95). The action spectrum constructed from these data fit an opsin template (R(2) = 0.91), which identifies 446-477 nm as the most potent wavelength region providing circadian input for regulating melatonin secretion. The results suggest that, in humans, a single photopigment may be primarily responsible for melatonin suppression, and its peak absorbance appears to be distinct from that of rod and cone cell photopigments for vision. The data also suggest that this new photopigment is retinaldehyde based. These findings suggest that there is a novel opsin photopigment in the human eye that mediates circadian photoreception.
Light can elicit acute physiological and alerting responses in humans, the magnitude of which depends on the timing, intensity, and duration of light exposure. Here, we report that the alerting response of light as well as its effects on thermoregulation and heart rate are also wavelength dependent. Exposure to 2 h of monochromatic light at 460 nm in the late evening induced a significantly greater melatonin suppression than occurred with 550-nm monochromatic light, concomitant with a significantly greater alerting response and increased core body temperature and heart rate ( approximately 2.8 x 10(13) photons/cm(2)/sec for each light treatment). Light diminished the distal-proximal skin temperature gradient, a measure of the degree of vasoconstriction, independent of wavelength. Nonclassical ocular photoreceptors with peak sensitivity around 460 nm have been found to regulate circadian rhythm function as measured by melatonin suppression and phase shifting. Our findings-that the sensitivity of the human alerting response to light and its thermoregulatory sequelae are blue-shifted relative to the three-cone visual photopic system-indicate an additional role for these novel photoreceptors in modifying human alertness, thermophysiology, and heart rate.
Light and dark patterns are the major synchronizer of circadian rhythms to the 24-hour solar day. Disruption of circadian rhythms has been associated with a variety of maladies. Ecological studies of human exposures to light are virtually nonexistent, however, making it difficult to determine if, in fact, light-induced circadian disruption directly affects human health.
A newly developed field measurement device recorded circadian light exposures and activity from day-shift and rotating-shift nurses. Circadian disruption defined in terms of behavioral entrainment was quantified for these two groups using phasor analyses of the circular cross-correlations between light exposure and activity. Circadian disruption also was determined for rats subjected to a consistent 12-hour light/12-hour dark pattern (12L:12D) and ones subjected to a "jet-lagged" schedule.
Day-shift nurses and rats exposed to the consistent light-dark pattern exhibited pronounced similarities in their circular cross-correlation functions and 24-hour phasor representations except for an approximate 12-hour phase difference between species. The phase difference reflects the diurnal versus nocturnal behavior of humans versus rodents. Phase differences within species likely reflect chronotype differences among individuals. Rotating-shift nurses and rats subjected to the "jet-lagged" schedule exhibited significant reductions in phasor magnitudes compared to the day-shift nurses and the 12L:12D rats. The reductions in the 24-hour phasor magnitudes indicate a loss of behavioral entrainment compared to the nurses and the rats with regular light-dark exposure patterns.
This paper provides a quantitative foundation for systematically studying the impact of light-induced circadian disruption in humans and in animal models. Ecological light and activity data are needed to develop the essential insights into circadian entrainment/disruption actually experienced by modern people. These data can now be obtained and analyzed to reveal the interrelationship between actual light exposures and markers of circadian rhythm such as rest-activity patterns, core body temperature, and melatonin synthesis. Moreover, it should now be possible to bridge ecological studies of circadian disruption in humans to parametric studies of the relationships between circadian disruption and health outcomes using animal models.
1. Non-image forming, irradiance-dependent responses mediated by the human eye include synchronisation of the circadian axis and suppression of pineal melatonin production. The retinal photopigment(s) transducing these light responses in humans have not been characterised. 2. Using the ability of light to suppress nocturnal melatonin production, we aimed to investigate its spectral sensitivity and produce an action spectrum. Melatonin suppression was quantified in 22 volunteers in 215 light exposure trials using monochromatic light (30 min pulse administered at circadian time (CT) 16-18) of different wavelengths (lambda(max) 424, 456, 472, 496, 520 and 548 nm) and irradiances (0.7-65.0 microW cm(-2)). 3. At each wavelength, suppression of plasma melatonin increased with increasing irradiance. Irradiance-response curves (IRCs) were fitted and the generated half-maximal responses (IR(50)) were corrected for lens filtering and used to construct an action spectrum. 4. The resulting action spectrum showed unique short-wavelength sensitivity very different from the classical scotopic and photopic visual systems. The lack of fit (r(2) < 0.1) of our action spectrum with the published rod and cone absorption spectra precluded these photoreceptors from having a major role. Cryptochromes 1 and 2 also had a poor fit to the data. Fitting a series of Dartnall nomograms generated for rhodopsin-based photopigments over the lambda(max) range 420-480 nm showed that rhodopsin templates between lambda(max) 457 and 462 nm fitted the data well (r(2) > or =0.73). Of these, the best fit was to the rhodopsin template with lambda(max) 459 nm (r(2) = 0.74). 5. Our data strongly support a primary role for a novel short-wavelength photopigment in light-induced melatonin suppression and provide the first direct evidence of a non-rod, non-cone photoreceptive system in humans.
Light is a potent regulator of systemic physiology. Specifically, environmental light is the primary stimulus for regulating circadian rhythms, seasonal cycles, and neuroendocrine responses in many mammalian species including humans (1,2,3,4). Shortly after the regulatory capacity of light was demonstrated in humans, light was tested as a therapeutic intervention for treating winter depression or Seasonal Affective Disorder (5,6,7). Since then, twenty years of clinical studies have confirmed that light therapy is effective for treating winter depression (8,9,10). In addition, light therapy has been studied as a treatment for selected circadian sleep disorders, nonseasonal depression, menstrual disturbances, eating disorders as well as re-entraining circadian physiology relative to the challenges of shift work or intercontinental air travel (11,12).
The importance of light not only as a therapeutic tool but as an essential element of healthy living has been highlighted by the recent discovery of a specialized photoreceptor in the eye responsible for synchronizing our internal circadian pacemaker. This pigment, melanopsin, differs from visual receptors in several characteristics, here simplified into a blue-shifted spectral sensitivity and a dose-response curve established from night-time studies. While a vast range of tools has been developed to simulate the amount of light in lux or lumens falling on a static, horizontal surface, corneal exposure estimates are needed for modelling the biological responses to light in space, which require a vertical sensor that can rotate and translate as a human eye does. This paper examines the effects of housing design upon the amount of daylight available for maintaining synchronization of the human circadian system considered in conjunction with human movement, using historic Boston row houses as a case study. Based on a series of simulations taking into account the two above-mentioned characteristics of the non-visual system, this paper proposes a preliminary workflow for suggestions regarding lighting restoration and opens new perspectives on future variables to include. This study found that even modest renovations like painting the space a lighter colour have a noticeable impact on the light received by a moving sensor. More aggressive design choices, such as not using the basement floor of the house for apartments, raise the amount and timing of light received to nearly the level of the best-case scenario.
Daylighting as a research topic situates itself at the interface between psycho-physiological and environmental factors, bringing together questions relevant to architectural design and building engineering, but also to human physiology and behavior. While daylighting has a strong impact on human health and well-being, and an undeniable association with (subjective) emotional delight and perceived quality of a space, it is also highly dynamic and variable in nature, based on a combination of predictable (sun course) and stochastic (weather) patterns. This makes it both a challenging and essential aspect of how “performative” a space can be considered.
The implementation of Complex Fenestration Systems (CFS) in the day-to-day life by practitioners, such as lighting designers, architects and façade makers is not an easy task. However, computer design tools can reinforce their usage through the determination of the luminous properties of a building interior prior to its construction or refurbishment. This paper presents a methodology based upon computer daylighting simulations carried out with RADIANCE in which the mkillum procedure was improved in order to render the light distribution due to diffuse daylight and sunlight on the inner surface of a fenestration system by the way of BTDF data. For the sake of standardization, the BTDF data accepted as input may be formatted according to the course of IEA Task 31 "Daylighting in Buildings" (e.g. following Tregenza format).
Daylight-redirecting systems with vertical windows have the potential to offset lighting energy use in deep perimeter zones. Microstructured prismatic window films can be manufactured using low-cost, roll-to-roll fabrication methods and adhered to the inside surface of existing windows as a retrofit measure or installed as a replacement insulating glass unit in the clerestory portion of the window wall. A clear film patterned with linear, 50- to 250-μm-high, four-sided asymmetrical prisms was fabricated and installed in the south-facing, clerestory low-e, clear glazed windows of a full-scale testbed facility. Views through the film were distorted. The film was evaluated in a sunny climate over a 2-year period to gauge daylighting and visual comfort performance. The daylighting aperture was small (window-to-wall ratio of 0.18) and the lower windows were blocked off to isolate the evaluation to the window film. Workplane illuminance measurements were made in the 4.6-m (15-ft)-deep room furnished as a private office. Analysis of discomfort glare was conducted using high dynamic range imaging coupled with the EvalGlare software tool, which computes the daylight glare probability and other metrics used to evaluate visual discomfort.
The present work discusses simulation results of annual indoor illuminance distributions for two office geometries situated in Freiburg, Germany, calculated with six different RADIANCE-based daylight simulation methods. These methods are the ubiquitous daylight factor method, ADELINE 2.0, the classified weather data according to Herkel and Pasquay and two simulation procedures based on daylight coefficients according to Tregenza, namely ESP-r version 9 series and a new accelerated method developed by the authors. The new method calculates 145 diffuse and three ground daylight coefficients in a single raytracing run which considerably reduces the required calculation times for an annual daylight simulation. An explicit calculation of the indoor illuminances under all 4703 annual hourly mean sky luminance distributions from the Freiburg test reference year (TRY) serves as a reference case against which the other methods are tested. The simulation results reveal that the accuracy of an annual daylight simulation method is not necessarily coupled with the required simulation time. The quality of an annual simulation rather depends on the underlying sky luminous efficacy model and whether the method considers the hourly mean direct and diffuse illuminances for each time period explicitly. The two methods relying on daylight coefficients exhibit the lowest relative root mean square errors (RMSEs) for the straightforward office geometry. The results for the advanced office show that internal illuminance contributions due to external ground reflections are only considered by the new method.
High dynamic range imaging has been shown to be a reliable tool to
assess luminance maps and glare risk probability in buildings. However,
there are some limitations of image capturing time, especially when
dealing with highly dynamic and contrasted daylight situations. We used
a newly developed prototype of a digital camera which contains a high
dynamic range pixel array chip, with a logarithmic scale for encoding.
This type of camera allows to effectively assessing luminance, contrast
and contrast directions, by taking only a single image or by performing
real time recordings. The device was equipped with a fisheye lens and
V-lambda filters to adapt the camera's spectral sensitivity to the human
eye. After spectral as well as photometric calibration and vignetting
correction, the device was tested to perform luminance mapping of real
scenes. The results showed that luminance maps of a room can be
efficiently assessed under dynamic daylight and mixed day- and electric
lighting conditions in a very short time (i.e. 100 ms), when compared to
classical HDR imaging techniques. This allows us to calculate glare
indexes of a scene simultaneously. The camera opens a variety of new
applications as a useful tool for architects, building designers and
lighting experts. The device can be used to easily monitor daylight
availability and glare indexes in existing buildings and further
developments for advanced (day-) lighting control can be envisaged.
After decades of intense research, the effects of light on the circadian system have been proved to exist. By studying the relationship between human physiology and light, research has also advanced to the point that there is the belief that these effects will be in future regulated by Standards. Establishing a direct connection among the fundamental radiometric, the traditional photometric and the new circadian approach to lighting becomes a fundamental step for introducing new concepts to lighting practitioners.This theoretical paper has the aim to propose a correlation between the traditional approach to lighting design with the new and still not definitely defined circadian approach by means of a photometric to circadian correlation factor. By this way, once the circadian efficiency function will be experimentally determined, technicians will be able to evaluate also from a numerical point of view the impact of lighting on the circadian system, adding health considerations to the traditional design process.
A set of simple test cases have been defined, within the activities of the CIE technical committee 3.33 and Subtask C of the IEA SHC Task 31, based on analytical or experimental references, with the objective of assessing lighting computer programs. The present paper aims to show the applicability and the usefulness of these test cases through the analyses of a conducted set of benchmarks. It is shown that the use of the CIE test cases allows to verify the level of accuracy of the tested programs with respect to the lighting physical laws that are highlighted separately within the different test cases. The comparison of the results of the different tested programs shows also that a program with a high accuracy in respect to a given aspect of lighting simulation is not necessarily accurate in simulating other aspects, which proves the usefulness of the CIE test cases in identifying the domain of applicability of a tested program.
Optimal three band Gaussian spectra were determined with an additional condition on the nonvisual biological action of the spectra. With this new condition the best possible trade off between the general color rendering index (CRI) and the luminous efficiency was found. The results show that in order to keep a biological effect of a light source equal to that of Planckian light source an additional restriction on the luminous efficiency for the given CRI arises.
Data on the exposure of the human eye to light are essential for investigation into the interaction of light with man. According to present knowledge, two different spectral sensitivities of the visible irradiance are relevant: (1) the spectral luminous efficiency function for vision and (2) the action spectrum for melatonin suppression, also used for other non-visual biological effects. We developed a device called LuxBlick to measure and record both quantities. It consists of two light sensors that are fixed on the wearer's head, and a control unit and data recording mini-computer worn in a bag around the waist. Real-time data are accessible to those wearing the device. Suitable to be worn in everyday life, the parts at the head are of low mass at the head and inconspicuous.
Within computer graphics, the field of predictive rendering is concerned with those methods of image synthesis that yield results that do not only look real, but are also radiometrically correct renditions of nature, i.e. which are accurate predictions of what a real scene would look like under given lighting conditions.
In order to guarantee the correctness of the results obtained by such techniques, three stages of such a rendering system have to be verified with particular care: the light reflection models, the light transport simulation and the perceptually based calculations used at display time.
In this report, we will concentrate on the state of the art with respect to the second step in this chain. Various approaches for experimental verification of the implementation of a physically based rendering system have been proposed so far. However, the problem of proving that the results are correct is not fully solved yet, and no standardized methodology is available. We give an overview of existing literature, discuss the strengths and weaknesses of the described methods and illustrate the unsolved problems. We also briefly discuss the related issue of image quality metrics.
Recent studies have attempted to link environmental cues, such as lighting, with human performance and health, and initial findings seem to indicate a positive correlation between the two. Light is the major environmental time cue that resets the human circadian pacemaker, an endogenous clock in the hypothalamus that controls the timing of many 24-hour rhythms in physiology and behavior. Insufficient or inappropriate light exposure can disrupt normal circadian rhythms which may result in adverse consequences for human performance, health and safety. This paper addresses the problem of prospective analysis of building architecture for circadian stimulus potential based on the state of the art in photobiology. Three variables were considered in this analysis: Lighting intensity, timing, and spectrum. Intensity is a standard design tool frequently used in illuminating engineering. Timing and spectrum are not commonplace considerations, so the analysis that follows proposes tools to quantitatively address these additional requirements. Outcomes of photobiology research were used in this paper to define threshold values for illumination in terms of spectrum, intensity, and timing of light at the human eye, and were translated into goals for simulation - and ultimately for building design. In particular, the climate-based Daylight Autonomy (DA) metric was chosen to simulate the probabilistic and temporal potential of daylight for human health needs.
Anidolic Daylighting Systems (ADS) typically reduce the daylight flux reaching an office room‟s window section and increase it in the rear of the room. They offer interesting possibilities for the combination of comfortable daylighting and highly energy-efficient office lighting designs. The objective of this study was to get an insight into typical ocular daylight exposures in office rooms equipped with ADS and to compare them to an artificial blue-enriched light source. Results from a recent study by Viola et al. [9] demonstrated that the use of the same light source positively influenced subjective wellbeing and sleep quality in office workers. We recorded daytime irradiance values for several weeks from April-May 2009 in an experimental office setup in our laboratory using a portable digital spectroradiometer. The artificial light sources were measured during the night. With respect to more circadian aspects of day- and artificial lighting designs we finally corrected the measured irradiances with a c(λ)-curve. Our results showed to which extent external sky conditions influenced light exposure of office workers in an ADS-equipped office room for different sky types. The considered ADS was able to supply natural blue light irradiance levels during large parts of days with intermediate and clear skies, which were much higher than those created by our artificial lighting installation based on two blue-enriched fluorescent lamps. The same was true for weighted circadian irradiance values Eec. We conclude that for the tested ADS-equipped office room, complementary artificial lighting with blue-enriched polychromatic fluorescent tubes might be useful on days with predominantly overcast skies and before 09:00 and after 16:30 on all days.
The integration of daylighting and electric lighting systems within buildings (also designated by "Green lighting") is a recent issue for the lighting research community: it allows achieving better lighting conditions for building occupants in particular within office rooms. Besides the substitution of electric light, daylighting can contribute in a significant way to improve the users' visual comfort and performance, a large variety of novel daylighting systems and components having been developed during the last years. In order to demonstrate this, an anidolic daylighting system combined with several electric lighting fixtures was set-up in an office room of the LESO solar experimental building located on the EPFL campus in Lausanne (Switzerland). Three different electric lighting modes, involving recessed luminaries (direct lighting), floor lamps (indirect lighting) and desk lamps (task lighting), were considered for that purpose.
Physical or virtual models are commonly employed to visualize the conceptual ideas of architects, lighting designers and daylighting researchers. The models are also used to assess the daylighting performance of their buildings, particularly when Complex Fenestration Systems (CFS) are considered. Recent studies have revealed a general tendency of physical models to over- estimate the performance, usually expressed through work plane illuminance and daylight factor profiles, when compared to that of the real building. These discrepancies can be attributed to several experimental errors. To analyze the main sources of error, a set of comparisons between a real building, a virtual model and a physical model was undertaken. The real building in our case consisted of a full scale test module with a south-facing windows designed for experimentation on daylighting systems. A virtual model was a computed model created in Radiance program while the physical model was a scale model (1:10) of the real case. The fenestration systems considered in this study were a simple window (double glazing) and two CFS (Laser-cut panel and Prismatic film). The physical model was placed in outdoor conditions similar to that of the real building as well as under a scanning sky simulator (for both real sky luminance distribution and CIE standard sky); the virtual model simulations were carried out with the program Radiance using the GenSky function (for CIE standard sky) and the Partial Daylight Factor (PDF) method, the later using the real sky luminance distribution acquired by a digital sky scanner at the same time as the real building's daylight performance was assessed. The daylighting performances of the building, daylight factor (DF) for overcast sky and illuminance ratio (IR) for clear sky, were monitored using illuminance meters: a set of sensors for exterior illuminance and another set of equally spaced 7 sensors placed at 1m intervals starting from the window plane for the interior space were used for that purpose. The interior surface luminance of both real building and physical model was measured using a luminance meter and a High Dynamic Range (HDR) imaging technique (within the Photosphere program). The Radiance program was used to determine the interior surface luminance within the virtual model. The measured performance of the real case, physical models and virtual models were compared, the causes of discrepancies between the real building and models were analyzed. The causes of errors that were evaluated were modeling of building details and dimensions, CFS modeling, mocking-up of the photometric properties (surface reflectance and window transmittance), model location as well as photometer features. To study the impact of these error sources on daylighting performance assessment, virtual models created using the Radiance program were used to achieve a sensitivity analysis of modeling errors. The significant factors were considered, leading to a set of modeling guidelines. The experimental study shows that large discrepancies can occur in daylighting performance figures. For example if glazings are omitted from the model's window, a relative divergence of 25% to 40% can be found at different points in the room, suggesting more light entering than actually measured in the real building. Inaccuracy in window transmittance inaccuracy is a major cause of errors commonly found in daylight modeling. In addition, significant discrepancies can be caused by even slight error in surface reflectance values. Only 10% overestimation of surface reflectance modeling leads up to 80% relative errors in work plane illuminance for a simple window and up to 90% for the assessment of CFS. Continuous sky distribution presented more accurate results than 145 sky sectors simulation, particularly when CFS were evaluated. These discrepancies can be reduced by making an effort to mock up the geometric and photometric features including the daylight simulation of the models carefully. A checklist presented in this thesis can be used as a guideline to help the daylight designers to estimate and avoid errors when assessing daylighting performance.
Human circadian rhythms were once thought to be insensitive to light, with synchronization to the 24-hour day accomplished
either through social contacts or the sleep-wake schedule. Yet the demonstration of an intensity-dependent neuroendocrine
response to bright light has led to renewed consideration of light as a possible synchronizer of the human circadian pacemaker.
In a laboratory study, the output of the circadian pacemaker of an elderly woman was monitored before and after exposure to
4 hours of bright light for seven consecutive evenings, and before and after a control study in ordinary room light while
her sleep-wake schedule and social contacts remained unchanged. The exposure to bright light in the evening induced a 6-hour
delay shift of her circadian pacemaker, as indicated by recordings of body temperature and cortisol secretion. The unexpected
magnitude, rapidity, and stability of the shift challenge existing concepts regarding circadian phase-resetting capacity in
man and suggest that exposure to bright light can indeed reset the human circadian pacemaker, which controls daily variations
in physiologic, behavioral, and cognitive function.
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Human adult males were exposed to combinations of two illuminances and two broadband spectral power distributions over the course of four night-time sessions. Results showed that melatonin suppression is dominated by short visible wavelengths (420-520 nm), consistent with recently published studies. Although the authors of these recent studies suggest that a novel opsin underlies melatonin suppression, the present paper offers a more conservative interpretation of the data based on what is known about existing photoreceptors and associated neuroanatomy and neurophysiology.
Light exerts powerful non-visual effects on a wide range of biological functions and behavior. In humans, light is intuitively linked with an alert or wakeful state. Compared to the effects of light on human circadian rhythms, little attention has been paid to its acute alerting action. Here I summarize studies from the past two decades, which have defined and quantified the dose (illuminance levels), exposure duration, timing and wavelength of light needed to evoke alerting responses in humans, as well as their temporal relationship to light-induced changes in endocrinological and electrophysiological sequelae of alertness. Furthermore, neuroanatomical and neurophysiological findings from animal studies elucidating a potential role of light in the regulation of sleep/wake states are discussed. A brief outlook of promising clinical and non-clinical applications of lights' alerting properties will be given, and its involvement in the design of more effective lighting at home and in the workplace will be considered.
Description de la télémétrie de l'application embarquée u ˆ viewer v3
- S Pangaud
Pangaud, S., 2011. Description de la télémétrie de l'application embarquée
u ˆ viewer v3.5b y ´, DEVISE-IcyCAM VSLOG. Centre Suisse d'e ´lectronique et de microtechnique (CSEM), Neuchâtel.
Assessment of circadian weighted radiance distribution using a camera-like light sensor
- A Borisuit
Borisuit, A., et al., 2013. Assessment of circadian weighted radiance
distribution using a camera-like light sensor. In: Proceedings of
CISBAT 2013 International Scientific Conference. Lausanne,
Switzerland.
Icycam - a High Dynamic Range Vision System
- C Arm
Arm, C., et al., 2008. Icycam -a High Dynamic Range Vision System, in
CSEM Scientific and Technical Report 2008, CSEM. p. 20.
LUMFACTOR: Luminous Efficacy changed from 470 to 179
- G W Larson
Larson, G.W., 1991. LUMFACTOR: Luminous Efficacy changed from
470 to 179. In: RADIANCE Digest.