High-quality daylighting plays a crucial role in creating a comfortable environment in educational auditoriums. It is well known that insufficient daylighting adversely affects both: students’ health and academic performance. The existing methods for designing and evaluating daylighting focus on ensuring the minimum acceptable levels of horizontal illuminance (Daylight Factor, D) required for visual tasks. However, it is equally important to provide comfortable general daylighting in auditoriums.
Currently, requirements for general daylighting are not systematized. This article proposes a structured approach to defining the functions of daylighting as general lighting in indoor spaces and criteria for assessing comfortable general lighting. These proposals aim to refine the requirements not only for daylighting but also for electrical lighting in future design projects. The authors continue to investigatethe relationship between measurable photometric parameters, obtained using a luxmeter, and qualitative lighting criteria such as light saturation, uniformity, and contrast.
The article presents the results of studies conducted in several auditoriums at the National Research Moscow State University of Civil Engineering (NRU MGSU) with side lighting openings, all serving the same functional purpose but differing in room and opening characteristics. An evaluation of D levels was carried out using the existing methodology, alongside an assessment of saturation through the ratio of the coefficient of daylight cylindrical illuminance (CDCI) to Daylight Factor (D). Additionally, the distributions of the coefficient of daylight vertical illuminance (CDVI) in four planes relative to the light opening and the coefficient of daylight spherical illuminance (CDSI) in characteristic cross-sections were analysed.
It was found that the CDVI in the plane oriented towards the wall opposite the light opening remains nearly constant in absolute values across all points of the characteristic cross-section of the room. Suggestions are provided for assessing contrast and light saturation in rooms using the CDVI.

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Currently, modelling light fields in a slab of a turbid medium is a fully solved task within the framework of the so-called discrete transfer theory. The slab model is of great practical importance, but there is a wide range of problems that cannot be reduced to it and have fundamentally three-dimensional (3D) geometry: twilight sky radiance, reflection from transparent objects, light fields in 3D-printed materials, and biological or medical tissues. To date, there is no general solution to the boundary value problems of the radiative transfer equation (RTE) in 3D geometry, and it is unlikely to exist given their diversity and multiparametric nature. Greater progress in solving 3D problems can be achieved by combining approximations with numerical methods.
In this paper, the solution is represented as the sum of an anisotropic part, approximated using a small-angle modification of the spherical harmonics method (SHM), and a smooth regular part, determined from the diffusion approximation, referred to as the quasi-diffusion approximation. The accuracy and applicability domain of this approximation are estimated by comparing the spatial-angular radiance distribution with the numerical solution of the RTE for a slab. It is shown that the difference does not exceed a few percent for most viewing angles. Further development of the method for 3D media is possible using advanced numerical tools for solving partial differential equations. The solution can be refined via the synthetic iteration method.

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Living rooms are shaped by functional, aesthetic, and socio-economic choices and formed by visual factors such as luminance contrast and colour schemes that create distinct atmospheres. Using a single living room image with digitally manipulated luminance contrast levels and colour schemes (warm, cool, and grey), 35 Turkish participants evaluated the emotional and cognitive effects of these variations. Results indicate that luminance contrast significantly shapes the perception of atmosphere, with higher contrast contributing to more vibrant and lively spaces, while low-contrast grey schemes led to more subdued, negative associations. Gender differences emerged in the perception of certain adjectives, such as ‘depressing’ and ‘uncomfortable’. By examining how visual elements create distinct atmospheres in domestic spaces, this study offers insights relevant to interior design and domestic architecture, contributing to a deeper understanding of how material and sensory elements influence the experience of home environments.

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The article introduces the concept of “light-graphic design”, which reveals the synthetic aspects of lighting design that combine informational illumination, graphic design, and urban wayfinding. The authors examine the results of 2018 discussions on terminological changes in the field of lighting design, as presented in publications of the “Svetotekhnika” journal. The study analyses the application of light-graphic design in the structure of the historical centre of St. Petersburg, highlighting existing issues such as the lack of systematization in light signage, light pollution caused by advertising and decorative lighting, and the inconsistency between architectural lighting and the perception of light-graphic information. The authors argue for the necessity of developing a unified wayfinding system based on the synthesis of light and graphics. They emphasize the importance of creating a unified graphic design code to facilitate orientation in the urban environment.
Proposed solutions to these problems outline the main directions for the development of light-graphic design, using urban wayfinding in the protected historical and cultural zones of St. Petersburg as an example. These include structuring innovations in light infographics and existing informational signs, implementing light projection technology, introducing interactive markers into the urban environment, utilizing animated light-graphics, employing light installations and art objects as landmarks, and, finally, creating light scenarios and routes as tools for visual orientation that ensure an organic perception of the urban context.
Key aspects of the research include the modernization of light-graphic tools in the development of tourist routes and the identification of architectural landmarks during night time, as well as the potential use of light routing in the design of urban park spaces.
The authors identify promising directions for the development of light-graphic design in the historical centre of St. Petersburg, justifying the need for a comprehensive light wayfinding system as a significant component of the city’s informational environment.

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The relevance of the topic of the article is caused by the low quality of the architectural environment, which is determined among other things by the requirements for sufficient insolation not only of residential premises in houses, but also in the territories adjacent to them. However, more and more often there are demands to abolish the concept of insolation, leaving only the concept of illumination, which is caused by investment interests to increase the density of buildings not only by a simple increase in the number of storeys, but also by a reduction of insolation gaps between buildings. It is quite obvious that such ill-conceived decisions can adversely affect not only the health of subsequent generations, but also the gene pool of the nation as a whole. At the same time, the already low architectural quality of the mass dwelling will finally become unsuitable for a full life. In this regard, the purpose of this study is a chronological analysis of the impact of insolation requirements on the calculated building density standards and the evolution of the aesthetic appearance of mass housing at different time stages. To achieve the goal, tasks have been set related to the loss of privacy and scale to humans in the environment, the identification of insufficient greenery and places of quiet rest in an open space, which leads to the facelessness and monotony of the spatial pattern of new construction. A hypothesis has been put forward about the need to switch from multi-storey construction to low-rise buildings of comparable density with the obligatory preservation of insolation standards, which will help ensure a high aesthetic and sanitary-hygienic quality of development.
The issues of insolation, and accordingly the quality of mass residential development, were considered in the works of individual scientists and research teams, published in 2004–2023 in free print on the pages of the electronic e-library and the databases of Russian Science Citation Index (RSCI), Scopus, and Web of Science.
The results of search queries include 104 links with a sample of 20 articles, the analysis of which was carried out taking into account the following main directions: the history of changes in the standards for ensuring insolation of premises in residential buildings and in the territories they formed, as well as the effect of the duration of insolation on building density injection and, as a result, deterioration of the architectural appearance of mass residential development.
The prevailing trends in reducing the time of insolation in residential premises and in playgrounds, together with the growing number of square meters per unit of territory, led to a deterioration in the quality of life in areas of new housing construction. The transition from multi-storey to low-format high-density residential buildings will help improve the architectural appearance of mass housing.

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Based on long-term experimental studies and analysis of the specific features of the current-voltage characteristics of quantum well light emitting diodes (LEDs), based on wide-bandgap semiconductors, it has been found that modern quantum well LEDs have an inherent limitation on their operating current density, determined by existing design and technological parameters. This limitation is associated with the formation of a built-in electric field within the quantum well region, caused by the injection of excess charge from the incoming charge carriers. When such a built-in electric field forms in the quantum well region the efficiency decreases inversely with the potential difference between the outermost quantum wells, that is, inversely with the increasing current density.
Thus, a multiple quantum well structure can be modelled as a multi-plate parallel-plate capacitor, where the stored charge is proportional to the charge of the injected excess carriers or depends exponentially on the voltage that lowers the potential barrier of the space charge region. As a result, once a certain current density threshold is exceeded, the external voltage across the LED structure increases sharply.
The current density, at which the excess voltage Ui appears, is approximately the same for all quantum well LEDs with existing design and fabrication parameters. This threshold can be described by the expression JКР=(2kTo)/(q2L), where L is the product of the carrier lifetime in the quantum wells and the distance between the outermost wells. This value typically falls within the range of (1–10) A/cm2.

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Working in the dark requires quality lighting of the construction site. To illuminate large open spaces, floodlights are used to create a powerful directional luminous flux, which improves visibility of working areas, reduces the risk of occupational injuries and improves overall safety at the construction site. Analysis of construction organization projects developed in period of 2014–2024 years revealed that almost all projects determine the number of floodlights for outdoor lighting of construction sites for incandescent lamps using the specific power method. Due to the fact that incandescent lamps are prohibited at the legislative level, LED floodlights are actually used on construction sites in violation of project requirements. This can affect the quality and safety of work, as well as increase the cost of lighting. The results of the study showed that the method of specific power provides at the required level of average illuminance on the horizontal plane, but can only be considered as a preliminary calculation and in the projects of construction organization should not use them, because the method does not take into account other mandatory lighting characteristics that determine the safety of work at the construction site. For the device of general illumination of the studied construction site preferable are floodlights with a capacity of 70 W in the number of 28 pcs. Other LED floodlights turned out to be more than (1.04–4.64) times more expensive to operate and maintain.

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Outdoor public lighting is essential for shaping nocturnal urban environments, as it significantly enhances visibility and fosters a sense of safety perception and visual comfort in public spaces, thus, influencing their usage. While extensive research has been conducted on lighting parameters such as luminance, illuminance, uniformity, and glare, there remains a lack of focus on user preferences for actual outdoor lighting settings. This study aims to address this gap by investigating photo stimuli based on public lighting preferences in a real outdoor environment in Ljubljana, Slovenia. In this research, 116 participants evaluated their levels of comfort, confidence, and spatial awareness based on nine virtual images from two distinct locations featuring various lighting settings, these included continuous and less-continuous lighting environments, low-mounted (4.5 m) lighting poles vs. high-mounted (12 m) lighting poles, three distinct CCTs, and both overhead and peripheral lighting environments. Participants rated each lighting scene on a 5‑point scale, facilitating an assessment of their preferences. The analysis revealed a significant preference for continuous, high-mounted (12 m) lighting poles with a natural white CCT in the square area, and for overhead lighting in the road area. The most substantial difference in user experience was observed between continuous and less-continuous lighting environment, while variations in pole height, CCT, and lighting position demonstrated comparatively minor impacts. Notably, the influence of CCT on participants’ perceptions of safety, comfort, and spatial awareness was the least significant among the factors examined.
These findings provide valuable insights into the design of urban lighting aimed at enhancing safety and comfort, thereby informing future urban planning and lighting design practices.

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The paper reports an experimental photobiological study estimating the effectiveness of different spectral modes of photosynthetically active radiation (PAR) for cultivating tomato vegetables using LED irradiators as electrical grow lighting. Variety of Tomato cv. Katya F1 was used in the study. The purpose of the study was to compare the photobiological efficiency of radiation from dimmable LED irradiators with an adjustable spectrum and high-pressure sodium lamps (DNaT‑600).
PAR irradiance at the upper leaf level was maintained constant in the treatment (using LED) and control (using DNaT‑600) and was (425 ± 15) μmol/(m2·s). Energy consumption was measured using electronic electricity meters separately for the control and treatment part of experiment. The characteristics of plant growth and development were recorded throughout the experiment. The tomatoes were analysed for nitrate, sugar, and vitamin C contents.
The study showed that during the growing period of 80 days, a twofold saving in energy consumption was achieved in the treatments with LEDs compared to the control. At the same time, the yield of vegetables per illuminated area in the control was 63.9 kg, which exceeded the average values of this parameter in the treatments by 1.4 times. Taking into account the consumed electricity, the cost of the tomatoes produced in the treatment was lower by 38 % and amounted to 42.2 kW·h and in the control to 58.1 kW·h per one kg of tomatoes. The assumption is substantiated that the reasons for differences in tomato yields may be associated, first of all, with different qualitative and quantitative characteristics of infrared radiation in LED irradiators and sodium lamps. Ways to improve LED irradiators to increase the photobiological efficiency of their radiation are outlined.

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Lanlan Wei, Grega Bizjak, Matija Svetina, and Matej B. Kobav
Assessing Lighting Preferences in Nocturnal Urban Environments: A Photo Stimuli Survey on Safety Perception and Visual Comfort

Ipek Yalcın and Nilgun Olgunturka
Living Room Atmospheres: Exploring How Luminance Contrast and Colour Influence Domestic Space

George V. Boos, Andrei A. Grigoryev, and Victoria A. Rybina
Analysis of Physiological Colorimetric Systems of Trichromats

Olga A. Vul and Daniil F. Nikandrov
Light-Graphic Design in Wayfinding of the Historical Centre of Saint Petersburg

Irina V. Sokolova
LED Street Lighting

Elena A. Korol and Evgeniy N. Degaev
Calculation and Evaluation of the Effectiveness of Lighting the Construction Site with Floodlights of Various Capacities