Satellite-based methods are proposed to estimate global illuminance from geostationary satellite data under local climate conditions. The data used in this model are global irradiance and global illuminance collected from the International Daylight Monitoring Programme research class station in The Chinese University of Hong Kong and the visible channel data of the Geostationary Operational Environmental Satellite 9 from May 2003 to May 2005. The proposed methods consist of an indirect method, which derives global irradiance from satellite images first and then converts global irradiance to global illuminance by a luminous efficacy model, and a direct method, which derives global illuminance directly from satellite images. The root mean squared errors of hourly global illuminance are 35% and 32% for the indirect and the direct methods, respectively.

A novel apparatus was used to examine the effect of light source, illuminance and observer's age on the ability to detect obstacles in peripheral vision, simulating a raised paving slab under mesopic visual conditions. The data collected were used to determine the height of obstacles above the paving surface required for 50% detection. From these detection heights it was determined that: (1) obstacle detection was influenced by illuminance, the 50% detection height being lower at 20 lux than at 0.2 lux, (2) the young observers (<45 years old) showed the smaller 50% detection height at 0.2 lux, but at 20 lux there was no difference in obstacle detection height between the younger and older (>60 years old) age groups, and (3) obstacle detection was affected by lamp type at 0.2 lux, with the 50% detection height decreasing as lamp S/P ratio increased, but at 2.0 and 20 lux there was no significant difference between the three test lamps.

Metal halide (MH) lighting systems are gaining in acceptance relative to high-pressure sodium (HPS) lighting systems for many night time applications. The present paper describes a series of studies carried out to address some of the ‘quality’ issues associated with MH and HPS lighting systems. HPS and MH installations were compared in terms of perceptions of brightness and safety, acceptability for social interaction, facial recognition and eyewitness identification. At equal photopic light levels, a street scene illuminated at night by an MH lighting system was reliably seen as brighter and safer than the same scene illuminated by an HPS system. In terms of acceptability for social interaction, facial recognition and many aspects of eyewitness identification, the measured differences between lighting systems were not as clear.

This is the second of the three papers providing fundamental information for the development of an adaptive lighting system for older adults. This paper examines the effects of two different forms of dynamic lighting – having the same average illuminance over time – on the performance of the numerical verification task (NVT) by older adults. As a group, the older adults showed no difference between the two forms of dynamic lighting. However, by involving the individual’s sensation seeking needs it was shown that the kind of dynamism (quickly increasing or quickly decreasing) influences both the subjective preferences and the objective visual performance. As individuals, all of the participants’ performances were determined mainly by the time, and illuminance variables proving the effect of dynamic lighting.

This paper examines the psychological and psychophysiological effects of blue light exposure – as compared to red light exposure – on older adults during the day. The blue lighting was found to be significantly more activating and more unpleasant than the red lighting. The mid-frequency high-frequency ratio of the heart period variability slightly decreased under blue lighting indicating an increase of parasympathetic modulation in this lighting condition compared to red lighting.

The objective of these studies was to provide sound empirical data for an intelligent, adaptive home lighting system to be created for the elderly. To meet these objectives involved measuring the psychophysiological reactions/states of the elderly during selected every-day situations and testing the psychophysiological effects of different lighting conditions. The results are that (1) the best psychophysiological measures for the intelligent learning loop are the skin conductance response and the heart period, (2) significant performance differences were found under different lighting conditions and (3) the subjective opinions generally were in accordance with the ideas of the designer of the lighting system.

This paper reviews developments in hybrid light guidance systems. In these daylight and electric light are simultaneously delivered into a building where they are combined and distributed via luminaires. The technology used in hybrid systems, both conceptual and realised, is discussed. The review speculates as to their likely performance in terms of daylight delivery; capital and running costs; user reaction to the systems; potential impact of the systems on the building which they light; and suitable design methods. It is noted that a substantial amount of work remains before the potential of hybrid systems may be realised, notably on their long-term economics and feasibility in different geographic locations.

We investigated the influence of lighting on performance at activities of daily living in 24 older people with low vision from cataract and/or macular degeneration. Participants carried out four everyday tasks, each at three illuminances: 50 lux, 200 lux, and 800 lux. Both objective performance and subjective preference were recorded. Subjects tend to perform better under brighter conditions, but the average results masked large individual variations. Indeed, most participants showed a large effect of lighting on performance in at least one task, but the optimal light level varied idiosyncratically from one subject to another. The best approach to provide optimal lighting for older people with low vision may be to individually assess their preference and performance at different light levels.

The thermodynamics of a radiating and evaporating tungsten filament having a hot-spot defect are examined theoretically. Assuming quasi-steady-states for the main and the hot-spot segments, the time profiles of their temperatures and radii are derived in closed form. Explicit relations among the fractional mass loss, failure time and defect size ratio are obtained and compared against approximate expressions used by Gluck and King⁷ and by Elenbaas.¹⁴ Numerical results computed for vacuum lamps support our theory.

The notion of stages of the lighting profession is examined to identify the main themes that have directed the objectives of the lighting profession. It is proposed that the objective of the first stage was provision of uniform illumination over a horizontal plane, and that of the second stage has been to provide illuminance suited to human need, based on visual performance. This brings us up to the current era, and it is the author’s opinion that the second stage has failed to achieve its objective. While codes and standards pay lip service to visual performance, the reality is that for the vast majority of situations where lighting standards are applied, the aim is to meet user expectations for the spaces they occupy to appear adequately lit. The metrics currently used to specify, measure, and calculate lighting levels are inappropriate for this purpose. The concept of mean room surface exitance is proposed as a basis for lighting standards. Procedures for calculation and measurement lead to some startling conclusions. Familiar notions of lighting effectiveness and efficiency are turned upside down, and an entirely different way of thinking about interior lighting design is revealed. The essential difference is a switch from assessing light incident on planes to assessing light arriving at the eye. Such a change of thinking may be seen as a precursor for the third stage of the lighting profession.

We address the issue of renewal rate of fused filament lamps in an organisation and modify the description given in an old edition of the IESNA Lighting Handbook (1968). This is achieved by applying the standard mortality curve to formulate an exact algebraic relation for the renewal fraction at successive stages. Finally, for the benefit of illuminating engineers a rule of thumb is developed, which estimates the saturation number of lamps to be replaced as a function of burning time, half-life and the total number of lamps installed.