Skip to content
News

Person: Mehlika Inanici

Multispectral lighting simulation approaches for predicting opsin-driven metrics and their application in a neonatal intensive care unit

Jung, B., Cheng, Z., Brennan, M., Inanici, M. (2023). Multispectral lighting simulation approaches for predicting opsin-driven metrics and their application in a neonatal intensive care unit. Proceedings of Building Simulation 2023: 18th Conference of IBPSA. https://doi.org/10.26868/25222708.2023.1446.

View Publication

Abstract

Design decisions affect the duration, intensity, and spectra of light exposure in built environments. Therefore, it is necessary to quantify and visualize the interaction of light and biology to inform design decisions that can improve health outcomes. This paper explains the addition of new features in a multispectral lighting simulation tool. Sample workflows are demonstrated through a neonatal intensive care unit (NICU) design. State-of-the-art NICUs have complex lighting designs that provide full-spectrum lighting that changes its spectra and intensity in 24-hour cycles. Prescription of healthy light recipes through thoughtful design decisions and dynamic commissioning practices of shading and programmable electric light systems are discussed.

Keywords

Daylighting; Circadian Rhythms; Non-image forming Ocular Photoreceptors, NICU.

Tri-stimulus Color Accuracy in Image-based Sky Models: Simulating the Impact of Color Distributions throughout the Sky Dome on Daylit Interiors with Different Orientations

Inanici, M. (2019). Tri-stimulus Color Accuracy in Image-based Sky Models: Simulating the Impact of Color Distributions throughout the Sky Dome on Daylit Interiors with Different Orientations. Proceedings of Building Simulation 2019: 16th Conference of IBPSA. https://doi.org/10.26868/25222708.2019.210585.

View Publication

Abstract

Spectral properties of daylight surpasses any other light source. Its dynamic intensity and spectra across the full spectrum facilitates sustainable daylighting practices, produces best color rendition, and regulates circadian rhythms in all living beings. However, simulation models do not typically include spectral variability; daylight is modelled as a uniform, equal energy white source. In this paper, tristimulus calibration procedures are utilized to create spectrally accurate High Dynamic Range (HDR) photographs. HDR photographs of skies are collected and utilized as an input to image based lighting (IBL) simulations. The impact of color variations across the sky dome and between different sky conditions are studied. Per-pixel photopic luminances, tri-stimulus chromatic distributions, Correlated Color Temperatures (CCT) and circadian luminance and illuminance values are quantified for image-based daylighting simulations, and compared with standard colorless Perez skies.

Keywords

color based skies; image based lighting; daylight simulations; high dynamic range imagery; color calibration

Our skies are too grey: Where is the colour?

Knoop, M., Balakrishnan, P., Bellia, L., Błaszczak, U., Diakite-Kortlever, A., Dumortier, D., Hernández-Andrés, J., Inanici, M., Kenny, P., Kobav, M., Liang, S., Luo, T., Maskarenj, M., O’Mahoney, P., Pierson, C., Thorseth, A., & Xue, P. (2025). Our skies are too grey: Where is the colour? Lighting Research & Technology (London, England : 2001). https://doi.org/10.1177/14771535251322618.

View Publication

Abstract

The Daylight Illuminant D65, a standardised reference light source in design and research with a colour temperature of 6500 K, is often used to describe the colour of the daylight. However, it represents the colour of an overcast sky, failing to capture the variability and richness of actual daylight, particularly the blue of clear skies. Recent research shows that both sunlight and skylight significantly influence our mood, perception and physiological responses. The colour of daylight is influenced by factors like sun position, weather conditions, as well as geographical location. To address these variations, researchers are collecting worldwide spectral daylight measurements, emphasising the need for localised spectral reference data to appropriately represent daylight in different locations.

Methodology to modify and adapt the standardised spectral power distributions for daylight to account for geographical, seasonal and diurnal variations for practical applications

Knoop, M., Balakrishnan, P., Błaszczak, U., Diakite-Kortlever, A., Dumortier, D., Hernández-Andrés, J., Inanici, M., Kenny, P., Maskarenj, M., O’Mahoney, P., Pierson, C., Rudawski, F., & Thorseth, A. (2025). Methodology to modify and adapt the standardised spectral power distributions for daylight to account for geographical, seasonal and diurnal variations for practical applications. Lighting Research & Technology (London, England : 2001). https://doi.org/10.1177/14771535251322386.

View Publication

Abstract

In recent years, the spectral properties of solar radiation and daylight have become increasingly important in lighting design and research, and various approaches to implement these have been applied. This paper proposes to modify and adapt the CIE reconstruction method, a procedure developed in the early 1960s to define standardised spectral power distributions (SPDs) of daylight, for this purpose. The CIE D Illuminants resulting from the reconstruction procedure are widely used for standardisation purposes but are based on a smaller number of measurements and do not consider geographical, seasonal and diurnal variations. In order to be able to use the CIE reconstruction method specifically in daylight planning, research and application, a technical committee of the CIE has launched a worldwide measurement campaign to collect spectral daylight measurements. The aim of the committee is to formulate a customised reconstruction method that more accurately reflects the local SPDs of daylight. This paper contributes to the discourse on the improvement of daylight estimation methods and emphasises the importance of accurate daylight data in various scientific and practical contexts.

Research Methods in Daylighting and Electric Lighting

Inanici, M. (2021). Research Methods in Daylighting and Electric Lighting. In: Azari, R., Rashed-Ali, H. (eds) Research Methods in Building Science and Technology. Springer, Cham. https://doi.org/10.1007/978-3-030-73692-7_4

View Publication

Abstract

Research in daylighting and electric lighting focuses on the physical quantity of light, physiological response to the physical stimuli, and the resulting visual perception. This chapter starts with an overview of the measurement and simulation-based research approaches used in understanding and quantifying the lighting availability and variability in the luminous environment. Field and laboratory measurements are discussed along with computational techniques. The rest of the chapter focuses on psychophysical research methods that aim to quantify the human physiological and psychological responses to the quantity and distribution of light.

Keywords

Daylighting; Electric lighting; Visual comfort; Visual performance; Visual perception; Energy efficiency; Circadian lighting

A Critical Investigation of Common Lighting Design Metrics for Predicting Human Visual Comfort in Offices with Daylight

Van Den Wymelenberg, K., & Inanici, M. (2014). A Critical Investigation of Common Lighting Design Metrics for Predicting Human Visual Comfort in Offices with Daylight. Leukos, 10(3), 145–164. https://doi.org/10.1080/15502724.2014.881720

View Publication

Abstract

Existing visual comfort metrics are reviewed and critiqued based upon their ability to explain the variability in human subjective responses in a daylit private office laboratory environment. Participants (n = 48) evaluated visual comfort and preference factors, totaling 1488 discreet appraisals, and luminance-based metrics were captured with high dynamic range images and illuminance-based metrics were recorded. Vertical illuminance outperformed all commonly referenced visual comfort metrics including horizontal illuminance, IES luminance ratios, daylight glare probability (DGP), and daylight glare index (DGI). The bounded borderline between comfort and discomfort is introduced, and preliminary visual comfort design criteria are proposed for several existing metrics. Fundamental limitations of glare indices are documented, and the implications of inconsistent application of luminance ratio calculation methods are quantified. Future research is detailed.

Keywords

daylight glare; daylight metrics; luminance ratio; vertical illuminance; visual comfort

Non-ionizing radiation modeling to predict ambient irradiance in work areas at an indoor cannabis farm

Chmielinski, M., Yost, M. G., Cohen, M., Inanici, M., & Simpson, C. D. (2023). Non-ionizing radiation modeling to predict ambient irradiance in work areas at an indoor cannabis farm. Annals of Work Exposures and Health. https://doi.org/10.1093/annweh/wxad048

View Publication

Abstract

Agricultural workers frequently experience potentially hazardous exposure to non-ionizing radiation from both solar and artificial sources, and measurement of this exposure can be expensive and impractical for large populations. This project develops and evaluates a vegetative radiative transfer model (VRTM) to predict irradiance in a grow room of an indoor cannabis farm. The model uses morphological characteristics of the crop, manufacturer provided lamp emissions data, and dimensional measurements of the grow room and cannabis hedgerows to predict irradiance. A linear regression comparing model predictions with the measurements taken by a visible light spectroradiometer had slopes within 23% of unity and R2 values above 0.88 for visible (400–700 nm), blue (400–500 nm), green (500–600 nm), and red (600–700 nm) wavelength bands. The excellent agreement between the model and the measured irradiance in the cannabis farm grow room supports the potential of using VRTMs to predict irradiance and worker exposure in agricultural settings. Because there is no mechanistic difference between visible and other non-ionizing wavelengths of radiation in regards to mechanisms of radiative transfer, the model developed herein for visible wavelengths of radiation should be generalizable to other radiation bands including infrared and ultraviolet radiation.

Keywords

horticulture; indoor; Marijuana; non-ionizing radiation; radiative transfer; UV

Window View Quality: Why It Matters and What We Should Do

Ko, W. H., Schiavon, S., Altomonte, S., Andersen, M., Batool, A., Browning, W., Burrell, G., Chamilothori, K., Chan, Y.-C., Chinazzo, G., Christoffersen, J., Clanton, N., Connock, C., Dogan, T., Faircloth, B., Fernandes, L., Heschong, L., Houser, K. W., Inanici, M., … Kent, M. (2022). Window View Quality: Why It Matters and What We Should Do. Leukos, 18(3), 259–267. https://doi.org/10.1080/15502724.2022.2055428

View Publication

Measuring Circadian Lighting through High Dynamic Range Photography

Jung, B.; Inanici, M. (2019). Measuring Circadian Lighting through High Dynamic Range Photography. Lighting Research & Technology, 51(5), 742 – 763.

View Publication

Abstract

The human ocular system functions in a dual manner. While the most well-known function is to facilitate vision, a growing body of research demonstrates its role in resetting the internal body clock to synchronize with the 24-hour daily cycle. Most research on circadian rhythms is performed in controlled laboratory environments. Little is known about the variability of circadian light within the built and natural environments. Currently, very few specialized devices measure the circadian light, and they are not accessible to many researchers and practitioners. In this paper, tristimulus colour calibration procedures for high dynamic range photography are developed to measure circadian lighting. Camera colour accuracy is evaluated through CIE trichromatic (XYZ) measurements; and the results demonstrate a strong linear relationship between the camera recordings and a scientific-grade colorimeter. Therefore, it is possible to correct for the colour aberrations and use high dynamic range photographs to measure both photopic and circadian lighting values. Spectrophotometric measurements are collected to validate the methodology. Results demonstrate that measurements from high dynamic range photographs can correspond to the physical quantity of circadian luminance with reasonable precision and repeatability. Circadian data collected in built environments can be utilized to study the impact of design decisions on human circadian entrainment and to create guidelines and metrics for designing circadian friendly environments.

Keywords

Physical Constants; Medical Photography; Photography; Built Environment; Morningness-eveningness Questionnaire; Statistical Reliability; Circadian Rhythms; Action Spectrum; Ganglion-cells; Bright Light; Exposure; Sensitivity; Framework; Daylight; Daytime; Model; Rod

Deep Neural Network Approach for Annual Luminance Simulations

Liu, Yue; Colburn, Alex; Inanici, Mehlika. (2020). Deep Neural Network Approach for Annual Luminance Simulations. Journal Of Building Performance Simulation, 13(5), 532 – 554.

View Publication

Abstract

Annual luminance maps provide meaningful evaluations for occupants' visual comfort and perception. This paper presents a novel data-driven approach for predicting annual luminance maps from a limited number of point-in-time high-dynamic-range imagery by utilizing a deep neural network. A sensitivity analysis is performed to develop guidelines for determining the minimum and optimum data collection periods for generating accurate maps. The proposed model can faithfully predict high-quality annual panoramic luminance maps from one of the three options within 30 min training time: (i) point-in-time luminance imagery spanning 5% of the year, when evenly distributed during daylight hours, (ii) one-month hourly imagery generated during daylight hours around the equinoxes; or (iii) 9 days of hourly data collected around the spring equinox, summer and winter solstices (2.5% of the year) all suffice to predict the luminance maps for the rest of the year. The DNN predicted high-quality panoramas are validated against Radiance renderings.

Keywords

Scattering Distribution-functions; Daylight Performance; Glare; Model; Prediction; Daylighting Simulation; Luminance Maps; Machine Learning; Neural Networks; Hdr Imagery; Panoramic View