bluuebunny/crossref_metadata_2025 huggingface dataset:
Void formation in tungsten lamp filaments
Authors: Day J.H.
Published: December 2008

Microstructural changes occurring during the annealing of tungsten halogen lamp filaments have been investigated using both optical and scanning electron microscopy. In tungsten wires that had completely recrystallised linear arrays of voids were observed approximately parallel to the axis of the wire, the void size being smaller the more extensive the deformation. With progressive annealing the voids increased in size and in the larger wires void coalescence caused the formation of a small number of relatively large voids, preferentially located at the grain boundaries. The mechanical stability of the lamp filaments would appear to be related to the spacings between both the linear arrays and the individual voids. At elevated temperature the voids appeared to contain gas which may have originated from the dopant materials or impurities in the tungsten. The observations also provide further support for the postulate that the doping mechanism in lamp filament tungsten depends on the formation of fine voids which retard recrystallisation and also preferentially inhibit grain boundary movements.
Comparison of some European interior lighting recommendations
Authors: Fischer D.
Published: December 2008

In view of the developing cooperation between European countries in almost every field, the question arises whether it is not also now time to commence international cooperation between European countries in the preparation of common recommendations for interior lighting. In order to stimulate further discussion, a comparison has been made between the current recommendations for interior lighting in Great Britain, France and Germany, taking into account the International Guide on Interior Lighting now under preparation by the CIE. Suggestions are made as to how the various quality aspects of interior lighting should be handled and which parameters should be included in the general recommendations. This refers especially to the values of illuminance which should be recommended for various types of task and interior.
Illuminance and utilance calculations for luminous ceilings
Authors: Bellchambers H.E. , Godby A.C.
Published: December 2008

A general method of determining utilization factors for luminous ceiling installations is given in IES Technical Report No. 2; this includes the uniformly diffusing ceiling. With the wider use of luminous ceilings, new materials and systems of light control have been introduced and early experience using some of the newer materials indicated the need for special care in the application of the Technical Report No. 2 procedure if errors were to be avoided. This paper reports the results of an investigation in which calculated values of workplane illuminance were compared with measured values in practical installations incorporating the newer materials. It is shown that if exact values of utilization factors are to be obtained precise calculation and photometric data are necessary. The method of design given in Technical Report No. 2 is valid for these installations, but a different procedure for calculating the cavity light output ratio is needed to improve the accuracy of the calculated utilization factors.
Tunnel entrance lighting—effect of fixation point and other factors on the determination of requirements
Authors: Narisada K. , Yoseoikawa K.
Published: December 2008

The Japanese recommendations for daytime tunnel entrance luminances are considerably lower than those of CIE and the difference has been attributed to the Japanese assumption that after a certain point on the approach a driver's eyes are increasingly fixated on the tunnel entrance. To verify this the eye movements of drivers approaching tunnel entrances were investigated by means of a corneal reflection eye-marker recorder. The results show that the concept of a fixation. point' is valid and avoids the difficulty of determining the CIE 'adaptation point'. Conditions which may hamper the adaptation of a driver's eyes were investigated and modification of the recommendations to suit these conditions are suggested.
Consistency and variation in preferences for office lighting
Authors: Tregenza P.R. , Romaya S.M. , Dawe S.P. , Heap L.J. , Tuck B.
Published: December 2008

In an experiment in which female office workers could freely adjust the lighting in a full-size model office the following results were obtained: the level of lighting chosen varied with the initial lighting in the room; the relative level chosen by individual subjects remained consistent despite variation in the absolute illuminances; subjects were consistent between experimental sessions several days apart; and there was a significant positive correlation coefficient between the age of subjects and chosen desk illuminance. Preferred illuminance ratios were obtained; no significant variation of the ratios with task illuminance was found, but there were similarities between the lighting choices in the laboratory and lighting in subjects' normal workplaces.
Illuminance, difficulty, complexity and visual performance
Authors: Boyce P.R.
Published: December 2008

Some recent results by Rowlands el al. have challenged the established relationship between illuminance, visual performance and task difficulty. A distinction can be drawn between task complexity, the number of operations needed to complete the task, and visual difficulty, the difficulty in seeing the detail required. It is then pqssible to show that the results of Rowlands et al. fit the established pattern and successfully to predict the results of a visual performance experiment using Landolt rings of the same visual difficulty but different task complexities.
Visibility under night driving conditions
Authors: Hills B.L.
Published: December 2008

Comparison between studies of visibility under night driving conditions has been made difficult by the wide range of test objects and visibility criteria used. This study attempts to provide a model by which the visibilities of a range of items can be estimated for night driving conditions. This first of three papers discusses laboratory studies of the effects of size and shape on visibility and various theoretical interpretations of the findings. It is argued that, despite its limitations, a single-channel model of spatial vision based on measurements of contrast sensitivity with discs remains the most relevant and practical theoretical framework with which to relate the visibilities of objects that are of interest in the night driving environment.
The impact of electronics on lighting
Authors: Isaacs A.
Published: December 2008

In recent years electronics has had an impact on almost every aspect of lamps and lighting from escape lighting to son et lumière, from reduction of gear losses to reduction of flicker, from tunnel lighting to theatre lighting, from automobile lighting to automation of lamp making machinery. Electronics is helping safety with hazard warning lights, automatically compensated tunnel lighting and measuring equipment to correlate street lighting with road accidents. The use of electronic ignitors to start high intensity discharge lamps assists energy conservation and reduces the material content of the control gear while invertor operated fluorescent tubes for transport lighting has to meet stringent requirements on transients.
Visibility under night driving conditions
Authors: Hills B.L.
Published: December 2008

The visibilities of a pedestrian dummy and disc objects of varying size and contrast were measured under dynamic night driving conditions on an unlit open road and in a road lighting situation for which the average pavement luminance was 0. 8 cd/m2. The visibilities of the objects could largely be described by a standard luminous increment-visual area characteristic. Under road lighting conditions, negative contrasts (silhouette vision) were found to give slightly greater visibilities than positive contrasts. It was found that a contrast multiplier of 4 was required in applying laboratory 50% probability of detection thresholds to a 'just visible' criterion level of visibility in the field experiments, though in practical conditions contrast multipliers as large as 30 may be required.
Preliminary study of automatic daylight control of artificial lighting
Authors: Crisp V.H.C.
Published: December 2008

The availability and present use of photo-electric continuous dimming or simple switching lighting controls are described and the cost effectiveness of using such systems is investigated. Although data on use of lighting are lacking, necessitating some assumptions, it is concluded that at present costs automatic dimming systems are likely to be cost effective in new buildings. Fitting existing lighting installations with automatic dimming control is not usually cost effective although an increase in electricity cost of about 4% per annum in real terms could change this. Despite smaller potential savings automatic switching can often be cost effective since initial costs are significantly lower. The maximum conservation potential of automatic controls is between 0.2 and 0.4% of UK primary energy use.
Air-handling luminaires and plenum exhaust systems
Authors: Bedocs L. , Godfrey R.L. , Sanford T.P.
Published: December 2008

There is growing interest in the use of plenum exhaust type air-handling luminaires to handle the return air in air-conditioned or ventilated spaces. One way of collecting the return air from the luminaires is to use the plenum as a duct. The types of air-handling luminaire in use are outlined and a standardized way of testing and presenting the data is proposed. The role of the ceiling in forming a plenum chamber and the types and ranges of ceiling available are examined and the effect of air leakage through the ceiling is described. Practical methods of measuring the air-tightness of commercially available ceilings are suggested and the use of the data with the performance data for air-handling luminaires during the design of plenum exhaust systems is described. Some site experiences and proposals for commissioning these systems are included.
Impression of brightness of objects and interiors
Authors: Bean A.R.
Published: December 2008

Values of scalar illuminance are included in the IES Code for Interior Lighting for certain areas. There is evidence that cylindrical illuminance might be a better correlate with the impression of the brightness of an interior. Experimental work is discussed and reported that suggests that the geometric mean of vertical and horizontal illuminance is also a significant parameter when comparing observers' impressions of the equivalent brightness of objects. Some of the experiments described show that hemispherical illuminance is a very good correlate to the impression of the brightness of objects where a single direction of view is considered.
Hue discrimination and light sources
Authors: Boyce P.R. , Simons R.H.
Published: December 2008

Eight experiments are briefly described in which the influence of lamp type, illuminance and subject's age and experience on the performance of the Farnsworth-Munsell 100 hue test were examined. Statistical analysis showed that either the CIE gamut area or the colour rendering index of the lamp type could be used as an approximate predictor of the level of performance on the test; the larger the CIE gamut area or the higher the colour rendering index, the better the performance. Compared with the effect of lamp type the influence of illuminance was small, the only significant effect being an improvement in performance at higher illuminances for the older age group. Age itself had a large effect. The older age group consistently produced much worse performances than the young or middle age groups. Experience was not found to be a significant factor.
Lighting for the security of premises
Authors: Baker J.E. , Lyons S.L.
Published: December 2008

While light has been used as an aid to security for centuries, it has often been applied intuitively as an aid in detecting intrusion rather than as the result of a considered appraisal of the whole night security problem. From tentative trials of simple floodlighting systems in 1969, the subject has progressed to an efficient technology now recognized as highly effective in limiting night crime. The increased interest of government agencies and police forces encouraged discussion and experiment until practical systems of lighting evolved and became accepted by users, insurers and crime prevention experts. The paper deals with security lighting as a branch of lighting application technology and for conciseness takes the benefits and effectiveness of correctly designed and installed schemes for granted.
The CIE visual performance system
Authors: Levy A.W.
Published: December 2008

The International Commission on Illumination (CIE) has developed a system for evaluating the visual performance aspects of lighting. The system and its concepts are presented with special reference to lighting energy conservation. Some of the problems involved in the application of the CIE system and the data required before widespread application is possible are discussed.
Experimental approach to high-pressure sodium lamp design
Authors: Denbigh P.L.
Published: December 2008

The paper describes a concise experimental procedure for the rapid design of any new rating of lamp, with particular emphasis on low power lamps. Information, in some cases obtained from 400 W lamps, has been used to reduce the number of free variables associated with the design of a lamp from 11 to three. Experiments in which the amalgam temperature is altered in an indium bath are carried out to optimize the lamp and ballast simultaneously. Nine such experiments give six possible designs for any new rating of lamp, and fix the ballast impedance needed for correct operation. From these six designs, one lamp may be chosen to satisfy best the main criteria of good colour, long life, high efficacy, ease of manufacture and commercial considerations.
Influence of impurities on pre-breakdown phenomena in the gas phase of discharge lamps containing mercury
Authors: Bergmann G.
Published: December 2008

The influence of various gaseous impurities (N2, H2, CO2 , H2O, Xe) on the breakdown voltage of argon and its Penning mixture with mercury has been investigated using an electrodeless high-frequency method. The breakdown voltage of the Penning mixture is shown to be more sensitive to these impurities than that of pure argon. The increase of the breakdown voltage observed in (argon + mercury) mixtures containing small amounts of impurities can be interpreted as being due to quenching collisions between argon metastables and impurity particles.
Operation of metal-halide lamps on square wave supply
Authors: Hall R.
Published: December 2008

In a comparison of the operation of high pressure metal halide lamps, on either sine or square wave supplies lamps have been found to operate satisfactorily using both choke and choke/capacitor ballasts. The dependence of lamp power on supply waveform and ballast type has been measured on 250 W MBI lamps for a supply voltage range of 210-270 V. Analysis of the lamp circuit for square wave supply voltage has been made using the simplifying assumption that the lamp voltage is independent of current. Expressions derived for the current waveforms and the power dissipated in the lamp are shown to agree well with experimental values. Although the analysis is used to predict the behaviour of metal-halide lamps, it is equally valid for other types of discharge lamps.
The role of drivers' vision in road safety
Authors: Davison P.A.
Published: December 2008

The literature on relationships between drivers' vision and their driving performance is reviewed. Certain vision tests, particularly those which use moving targets, are weakly associated with measures such as accident frequency and rate; their practical value in terms of road safety is very limited. Some visual abilities, such as extent of visual field, are unassociated with driving performance in general but may be relevant to specific types of accident; any association for tests of night vision remains open to question. Methodological problems are considered and possible reasons why associations are not stronger are discussed. Development of a new rapid test of contrast sensitivity function is mentioned together with some current and future research plans.
Studies concerned with improvement of the low pressure sodium discharge lamp
Authors: Jack A.G.
Published: December 2008

In the low pressure sodium-rare gas discharge lamp the generation of light is strongly dependent on the realization of an optimum sodium vapour pressure and optimum plasma conditions within the complete halfcycle of a.c. operation. Various diagnostic techniques will be discussed which give information about the plasma conditions and thus the light generation in the discharge. The influence of the current waveform and magnitude will also be considered. These studies indicate the necessary conditions which must be fulfilled if improvements in lamp performance are to be realized. Finally the application of these results to the improvement of the low pressure sodium discharge lamp and its associated ballast will be described.
Is equivalent sphere illuminance the future?
Authors: Boyce P.R.
Published: December 2008

Equivalent Sphere Illuminance (ESI) is defined and the quantities underlying it discussed. Its advantages and limitations are considered from theoretical and practical viewpoints. It is concluded that in many practical situations the use of ESI can be misleading. An alternative approach to design criteria which fulfills the same purpose as ESI without its disadvantages, is to specify task illuminance and contrast rendering factor separately.
Standardisation and quality assurance in the lamp industry
Authors: Jansson B.J.N.
Published: December 2008

The lamp industry has always played a leading role in the field of standardization and quality assurance. Lamp Standards were in existence before World War I and the industry was among the first to introduce statistics in its quality control. The use of the manufacturers' own test results for official approvals is explained together with a description of how the present IEC Publication 64 is used for an internal quality assurance system.
Modelling indicators for combined side and overhead lighting systems
Authors: Bean A.R.
Published: December 2008

For an observer the normal direction of viewing of the other occupants of a space is commonly at 90° to the downward vertical and may vary in azimuth over 360°. The light flow from overhead lighting installations intersects this plane of viewing at 90° whereas that from side lighting is parallel to the plane of viewing. A system of modelling indicators is introduced which takes into account these relationships and is offered as a means of studying combined artificial and daylight lighting systems. The point is made that a specification system for modelling simple enough for practical use cannot be completely comprehensive and give a guaranteed appearance. For this reason the concept of the modelling indicator is introduced and stipulated to give an indication of the type and variety of modelling to be expected.
Some aspects of the design of incandescent GLS lamps
Authors: Coaton J.R.
Published: December 2008

The design of general lighting services (GLS) incandescent lamps must take account of many aspects, including the effect of gasfilling content and pressure, filament design, and the influence of the electrical lead-in wires and filament supports. In most instances a compromise must be made to achieve the best overall result.

In general, the predominant failure mechanism is the formation and subsequent burn-out of a 'hot-spot'. Up to about 3000 hours the rate controlling process in most GLS types is tungsten evaporation, however, some evidence exists to show that for longer life lamps, and in particular low power ratings, other mechanisms such as surface and bulk diffusion of tungsten become significant and must also be taken into account in the design stages.
Visual performance of young Chinese observers
Authors: Ching C.C. , Yu B.L. , Jiao S.L. , Kuan L.R. , Chao K.M.
Published: December 2008

The visual performance of Chinese adults, 20 to 30 years of age, is evaluated as a part of a study determining illumination standards intended for use in The People's Republic of China. Spatial acuity was measured with Landolt rings as a function of visual angle, contrast and illuminance. The influence of these variables on visual performance is described by a mathematical model. The results are compared with the standard RCS visual performance curve recommended by the CIE.
Colours of transilluminated traffic signs
Authors: Terstiege H.
Published: December 2008

International recommendations on surface colours for traffic signs and on traffic lights have existed for a long time, but at the present time there are no recommendations for colours of transilluminated traffic signs. This investigation shows that colours of transilluminated traffic signs by day and night could be in agreement with the requirements of CIE Publ. 39, but for white colours by night the white chromaticity region of CIE Publ. 2 would be more appropriate. For the illumination of transilluminated traffic signs fluorescent lamps with light colour 15 "daylight de luxe" and 19 "daylight 5000 de luxe" give the best results.
Characterization of and constricted high pressure arcs by magnetic balancing
Authors: Drop P.C. , van den Hoek W.J.
Published: December 2008

A simple method is proposed to characterize the shape of the temperature profile of the arc in high-pressure discharge lamps. The method is based on the balancing of natural convection by external magnetic forces in the horizontal burning position. Experimental results are given for some well-known lamp systems including the mercury arc, the tin halide arc and the sodium-thallium-indium iodide arc, under various conditions. The results are in accordance with the trends observed in practice. Results are also given for rare-earth iodide arcs. In these systems arc motions occur under certain conditions. The nature of these phenomena is discussed.
The aesthetic function of colour in buildings: a critique
Authors: Whitfield T.W.A. , Wiltshire T.J.
Published: December 2008

This paper briefly reviews the information which is currently available in Britain to aid designers and public in the use of colour for buildings. It commences with an outline of the basic functions of colour: ergonomic, structural and aesthetic. The main discussion focuses upon problems of aesthetics. In this, particular attention is given to the phenomenon of 'fashion', or stylistic change.
Task and background lighting
Authors: Bean A.R. , Hopkins A.G.
Published: December 2008

A series of experiments are described in which groups of twenty observers were asked to complete questionnaires relating to the task and background lighting of an experimental room. The background lighting was varied over a wide range for task illuminances of 200 and 400 lux. The results obtained were used to answer the questions, "What is the lowest value of general illuminance that should be provided in any continuously used interior?" and "What should be the relationship between the task area illuminance and the background illuminance to ensure that visual conditions are satisfactory?"
Sources of error in spectroradiometry
Authors: Moore J.R.
Published: December 2008

Systematic errors in spectroradiometry, as in other areas of metrology, are difficult to quantify. An attempt is made here to identify potential sources of error that can occur at the various stages of the measurement process and to suggest ways in which they might be avoided or, at least, kept to a minimum. The special problems that arise in the case of sources, such as discharge lamps, with complex line spectra have led to the development of a new type of spectroradiometer system, based on a continuous scan principle.
Spectroradiometry in research and development on lamps
Authors: Wharmby D.O.
Published: December 2008

The importance of spectroradiometry in the research and development on discharge lamps is outlined. The developments in highpressure discharge lamps have stimulated improvements in spectroradiometry, particularly in the area of data-logging where methods applicable to any type of spectrum have been developed. Methods of testing precision are discussed, but assessing accuracy still requires well organised intercomparison experiments.
Applications of spectroradiometry
Authors: Jewess B.W.
Published: December 2008

This paper deals with the application of spectroradiometric methods to the measurement of the CIE chromaticity coordinates, and other colour parameters, of a range of different light sources. The data are required for specification and development purposes for lamps and lighting equipment.
A study of the sequential experience of different lighting
Authors: McKennan G.T.
Published: December 2008

A person walking through a building will experience a sequence of lighting installations and the adaptive mechanisms of his visual system will respond to each in succession. The delay in the photochemical response of the retinal cones is appreciable in relation to this movement from room to room. Equations have been derived to model this photochemical response, and both a field study and a scale model study have been carried out in order to calibrate this mathematical model. The effects of three alternative approaches have been compared: (1) the time course of photochemical changes was taken into account, (2) adaptation was determined by the illuminance of the area just vacated, and (3) adaptation effects were ignored. In many cases the simplest assumption was adequate. The more complex mathematical model was, however, found to be more accurate.
Properties of sodium tin halide-mercury discharges
Authors: Whittaker F.L.
Published: December 2008

Tin chloride/tin iodide/sodium chloride/mercury discharges have been studied in two silica arc tube shapes of differing volume and dosing density. The particular parameters examined were the amount of added NaCl and the effective cool spot temperature of the discharge, the latter being varied by means of an electrically-controlled bath of molten indium. High luminous efficacies (100 lm W-1) were found, independent of the amount of added NaCl. Extensive spectral and colour measurements showed that the tendency for the addition of NaCl to lower the colour rendering index can be counteracted by increasing the cool spot temperature. A lamp combining Ra = 75, CCT = 3800K with a luminous efficacy of 90-100 lmW-1 is possible. The method can indicate trends in discharge behaviour without restriction to a particular embodiment.
Tunnel lighting practice world-wide
Authors: van Bommel Wout
Published: December 2008

From a world-wide examination of tunnel lighting practice one has to conclude that many tunnel lighting installations differ on fundamental points of design: for example, in the lighting levels employed, in the lengths of the various lighting zones, and in the type of light sources used. Some of these differences are due to the fact that the lighting designs were based on specifications originating from different codes or based on different investigations, or both. These codes and investigations will be briefly evaluated. It will be argued that in some cases the differences are justifiably caused by differences in the practical conditions prevailing: such as, for example, in local outside adaptation luminances, differences in tunnel constructions and differences in speed limits.
Road lighting-as calculated and as in service
Authors: Hargroves R.A.
Published: December 2008

Extensive measurements have been made of the lighting qualities on about 100 main roads in Britain. Results have been collected for average road surface luminance, illuminance and uniformity, for surrounding luminance, disability and discomfort glare, and for the road surface characteristics. The degree of variation of road surface luminance along the road has also been noted. As such, this constitutes a large body of data on the quality of British lighting today. This paper then compares measured with calculated values of road luminance. Indications are given regarding the effectiveness with which installation performance can be predicted.
A study of the installed performance of industrial luminaires
Authors: Bedocs L. , De P.N.
Published: December 2008

In many industrial installations the luminaires are seldom cleaned except during re-lamping. This may result in substantial loss of luminaire light output and therefore of task illuminance. To minimise the effects, manufacturers have developed luminaires having a so-called 'self-cleaning' action. This paper reports on both field and laboratory studies made on such high-bay and fluorescent lamp luminaires.
Chemistry of metal halide lamps: a review
Authors: Work Dale E.
Published: December 2008

Metal halide lamps are complex high temperature chemical systems which are neither closed (with respect to material flow) nor well defined thermochemically. This complexity, coupled with the commercial importance of this lamp type, has spurred the development of several models which attempt to describe the chemical (and physical) phenomena which occur. This paper reviews the published literature over the past decade which treats the chemical phenomena and the modelling of these processes. The emphases in the paper are three: (1) the availability of pertinent thermochemical data and the bases for these data; (2) material requirements and limitations; and (3) observed chemical interactions among the chemical additives, the envelope, electrode materials, and impurities. A brief discussion of transport processes (chemical, convective, diffusive) is included.
Practical application of the Einhorn (CIE) Glare Index formula
Authors: Lowson J.C.
Published: December 2008

The paper has a twofold purpose. Firstly, to present a method for reducing basic glare formulae to a form simple enough to apply to routine lighting design problems with no more equipment than a slide rule or simple pocket calculator. Secondly, to show how this method can be applied to Dr. Einhorn's new proposed CIE Glare Index formula* including a detailed step-by-step procedure with a worked example. The paper concludes with a brief comparison of the formula with established glare calculation theory and observation, which suggests that it is a useful compromise between the different national schemes.
Effects of optical radiation on man
Authors: Steck B.
Published: December 2008

Optical radiation (ultraviolet, visible and infra-red) produces many effects upon living matter. Seeing is of course the most important, but it is only one of the effects. UV-radiation has the widest effect, as a consequence of its photons rich in energy, though its proportion in the radiation of natural and artificial sources is relatively low compared with the proportions of the visible and the infra-red wavelength range. Visible radiation not only stimulates vision but acts physiologically and psychologically via the eye and the skin upon the endocrine glands, the vegetative nervous system, and upon the whole organism. Infra-red radiation acts in most cases by raising the temperature. In national and international committees effort is made to measure and calculate the actinic effects of optical radiation. (German standard DIN 5031 and CIE TC-1.7 (Actinic effects of optical radiation)). The illumination levels desirable from a photobiological point of view correspond with illumination levels obtained by experiments where a large number of observers have been asked to assess subjectively the lighting conditions.
Preferred lighting conditions for the display of oil and watercolour paintings
Authors: Loe D.L. , Rowlands E. , Watson N.F.
Published: December 2008

The lighting of paintings suffers from the need to meet two conflicting requirements: the visual requirement of the gallery visitor and the conservator's requirement to preserve the works of art. The project explores by experiment in a full-scale mock-up gallery the lighting requirements in terms of three variables: painting illuminance, light source and light distribution within the gallery space. Subjective assessments were made using semantic differential scales and the results were analysed using factor analysis techniques. The findings indicate that a painting illuminance approaching 200 lux was required to give visual satisfaction from an illuminant with a high Colour Rendering Index and a high gamut area: also a degree of non-uniformity in light distribution was preferred. The work recommends that where strict conservation requirements are to be employed, then artificial lighting only should be used but that the galleries should be combined with other spaces lit with natural light, perhaps for the display of non-light-sensitive exhibits.
Effective glass transmission factors under a CIE sky
Authors: Littlefair P.J.
Published: December 2008

Daylight availability in interiors is reduced because the window glazing is not perfectly transparent. The reduction factor will vary throughout a room according to the angles of incidence of the incoming light on the glazing. This note outlines a new method to calculate the reduction of daylight from a CIE overcast sky due to glazing, which gives accurate results throughout the room. The method is compared with existing methods, and it is shown to be especially appropriate when average daylight factor is calculated by averaging values of daylight factor computed at points on a grid extending throughout the room.
A study of lighting in the home
Authors: Simpson J. , Tarrant A.W.S.
Published: December 2008

This paper reports some of the findings of a survey of 101 homes which aimed to see whether the differences in people's use of, and attitudes to, the lighting in their homes varied with such factors as the age, social class and income of the householder, whether the house was owned or rented, etc. The general and task-specific illuminance levels found in the kitchen, living room(s), hall and staircase are compared with those recommended by the CIBS/IES Code, the fixed and portable lighting provisions found are discussed. The illuminance levels were inadequate in the majority of cases. Poor provision of fixed lighting was greatly to blame for this. House owners were more likely than tenants to make changes or additions to their lighting.
The effects of illuminance on tasks performed in domestic kitchens
Authors: McGuiness P.J. , Boyce P.R. , Harker S.D.P.
Published: December 2008

Field measurements have shown that the illuminances used in kitchens tend to be much less than those recommended in the CIBS (IES) Code. This may be because people are unaware of the advantages of having higher illuminances or because the recommended illuminances are unnecessarily high. This paper reports an experiment designed to examine the effect of illuminance on the performance of tasks representative of those done in domestic kitchens. Thirty-two subjects performed four tasks at four different illuminances in a kitchen setting. Details of task performance, subjects' behaviour and the subjects' opinions of the lighting conditions, the task difficulty and the effort required to perform the tasks were collected. Statistical analysis of the results revealed that only one of the four tasks showed any variation in performance with illuminance. This lack of effect can be explained by the nature of the tasks and the ways in which the subjects modified their approach to the tasks as the lighting conditions became more difficult. The subjective results showed a consistent variation with illuminance for all four tasks; namely, a rapid increase in satisfaction with lighting conditions and a decrease in task difficulty and effort required with increasing illuminance. Taken together these results suggest that whilst an illuminance of 100 lux would serve reasonably well for many tasks and many people, an illuminance of 300 lux is undoubtedly an improvement for some tasks and groups of people.
On the uncertainties of photometric data for luminaires
Authors: Frederiksen Erik
Published: December 2008

This paper describes an investigation of the magnitude of uncertainties which can be expected on the photometric data for commercially available luminaires. Ten manufacturers and importers of luminaires in Sweden and Denmark have taken part in the investigation. Fifty-six luminaires have been selected by personnel from the Danish Illuminating Laboratory from the storerooms of these manufacturers and importers and measured at the laboratory. The measurements have been compared to the data, which the manufacturers have published in their catalogues. The comparisons have included light output ratios of the luminaires, coefficients of utilisation and BZ-classifications. Furthermore, the shape of the light distributions as well as the degree of asymmetry have been included. In order to evaluate the differences in these properties two new quantities: 'difference index' and 'asymmetry index' have been proposed. The conclusion of the investigation is that for scarcely half of the luminaires the catalogue data are satisfactory. However, a few of the luminaires show quite unacceptably great discrepancies. The causes of these discrepancies have not been investigated.
Excitation of acoustic instabilities in discharge lamps with pulsed supply voltage
Authors: Stormberg H.-P. , Schäfer R.
Published: December 2008

A problem associated with high frequency operation of high pressure discharge lamps is the occurrence of acoustic resonances of the gas volume inside the lamp in certain frequency regions. These resonances usually cause arc instabilities which make convenient lamp operation impossible. In this paper an investigation is made of the occurrence of acoustic resonances and arc instabilities as a function of the modulation depth of the lamp power. A critical value of this modulation depth, below which no arc instabilities occur in the power frequency range from 0 to 50 kHz, has been determined for different commercial lamp types.
Regional variations of daylight availability—a review of measured data and estimating methods
Authors: Secker S.M.
Published: December 2008

This Note summarises the measured daylight data for Britain and assesses the regional variations, not only with respect to latitude, but also urban polluted and cloudy areas. Methods developed for estimating illuminance are reviewed and some values for the luminous efficacy of total radiation are presented.
A study of the Colour Rendering Capacity of a light source
Authors: Xu H.
Published: December 2008

A new measure called Colour Rendering Capacity (CRC) has been developed to describe a particular aspect of colour rendering properties of light sources, that is, the maximum possible number of different surface colours obtainable under a given source. The CRC is a relative measure expressed as a dimensionless parameter between zero and unity, depending on the spectral power distribution of the source only. The CRC has been calculated for some commonly used sources and the result discussed with respect to other studies concerned with the colour rendering performance of light sources.
Appraisal of a light box as a low vision reading aid
Authors: Southall D.
Published: December 2008

Of fifty visually handicapped teenagers who had undertaken an hour of intensive reading on the transilluminating light box, thirty-eight claimed to prefer it to conventional, over-task, lighting. The three subjects who expressed a dislike of the light box made comments which suggest that design modification could make the box generally acceptable. Transillumination is found beneficial because it overcomes the problem of head shadow associated with conventional lighting systems, and would appear to have very good contrast rendering properties. The most suitable materials for use with the light box will require careful consideration. It is clear from these observations that the light box could become a useful aid to the visually handicapped and should therefore receive further development and investigation.
On the economic life of GLS incandescent lamps
Authors: Huettner M.
Published: December 2008

The paper deals with the determination of the theoretical optimum length of life of GLS incandescent lamps at a rated voltage. The mathematics include both lamps whose wattage is rated and those with a rated luminous flux. An exact mathematical derivation leads to values of life surpassing those derived hitherto. These results support the suggestion, expressed already earlier by another author, that the designed life of GLS incandescent lamps for domestic lighting should be increased—for economic reasons—by at least 50 per cent.
Movement under emergency lighting: the effects of changeover from normal lighting
Authors: Boyce P.R.
Published: December 2008

This paper considers how people's ability to move over an escape route is affected by different procedures for changing from normal room lighting to emergency lighting. The experiment took place in a large open plan office at two emergency lighting illuminances, 0.16 lx and 0.012 lx. The changeover to emergency lighting was either instantaneous or involved a 5 second period of darkness before the emergency lighting came on, as is allowed by BS 5266. The subjects were instructed either to move as soon as the emergency lighting came on or to wait until they felt able to move unhesitatingly over the escape route. The time taken to leave the office, the manner of movement and subjects' opinions of the conditions were all recorded. They showed that movement was faster, smoother and easier at 0.16 lx than at 0.012 lx, for all conditions. When the subjects moved immediately the emergency lighting came on, having a 5 second period of darkness allowed more rapid, steadier movement with fewer collisions once movement started. However, the total time taken to leave the room was slightly longer than if the subjects moved immediately following an instantaneous changeover. Allowing the subjects to wait until they felt able to move unhesitatingly, ensured smooth steady movement but the total time taken at 0.012 lx was much longer than if the subjects started to move immediately after the changeover. Estimates of the state of adaptation of the visual system following a step change in luminance provide a plausible explanation of all these results.
Model equation characteristics of high-frequency fluorescent lamps
Authors: Tola Muhammad , Bo Hiroshi
Published: December 2008

In analysing the operating model equation characteristics of fluorescent lamps it is necessary to use the model equations of equivalent conductance of the lamps on high frequency. The model equations are estimated by the error-rate between the experimental waveform and the simulation waveform on high frequency operation. The method of analysis is found to be useful in predicting the model constants and the characteristics of fluorescent lamps on high frequency operation.
Measured and calculated frequency distributions of daylight illuminance
Authors: Tregenza P.R.
Published: December 2008

Frequency distributions of illuminance in relation to solar altitude are derived from a survey of available daylight at Nottingham. These empirical functions are used to obtain the cumulative distribution of illuminance for a working year. The values obtained are similar to frequency distributions of illuminance published for Garston and Uccle.
A search for an improved ultraviolet radiation source
Authors: Page R.B.
Published: December 2008

This work examines the spectral modifications produced in high-pressure mercury discharge lamps by the iodides of iron, cobalt, manganese and antimony, both individually and in select combinations, at a lamp operating power of 1000 W. Individually, iron, cobalt and manganese iodide additives significantly improve the UVA spectral output at wavelengths beneficial to either the diazo photoprint or suntan application. Increasing the iodide quantity strongly depresses the radiation emitted in the UVB and UVC spectral regions. A select combination of iron and cobalt iodides, with mercury, enhances the UVA spectral response to a level beyond that achieved by the individual iodides alone. This combination has been used to develop a lamp with a spectrum covering adequately both the suntan and photoprint applications. None of the iodides in this trial improved on the performance of mercury in the UVC spectral region, supporting the view that water sterilisation may best be served by lamps dosed only with mercury.
The treatment of obstruction in interior lighting design— calculation of spacing-to-height ratio
Authors: Carter D.J. , McEwan I.
Published: December 2008

Most of the published work on the lighting of obstructed interiors is concerned with the development of calculation procedures to enable designers to investigate the lighting conditions in a quantitative or qualitative way for particular configurations of room geometry, contents and lighting equipment. This general approach is appropriate only if the designer has detailed knowledge of the space to be lit. In the design of a building where the eventual nature of the interior space is not known, more general design guidance for obstructed spaces is required in the initial synthesis stage of the design process. This paper develops the idea of extending existing guidance for lighting design for empty rooms by adopting a modified maximum spacing-to-height ratio which allows for obstruction loss and which could be used in addition to normal spacing-to-height ratio in installation design.
A rapid-light miniature metal halide lamp
Authors: Inouye A. , Honda K.
Published: December 2008

A metal halide lamp shows higher intensity, greater luminous efficacy and longer life as compared with an incandescent lamp. However, a few minutes are needed for it to reach full light output after ignition. This limits the application of the metal halide lamp. A rapid-lighting miniature 35 W metal halide lamp has been developed to extend its applicability. The following technology is applied: A ceramic heater of 30 W operating power is mounted next to the arc tube. The arc tube is heated immediately before or at the time of starting to gain light output rapidly. New electrodes for the discharge tube have been developed; these carry a high current input during starting. The starting pulse waveform starting pulse is in two parts. A short pulse of very high voltage breaks through the arc gap. A long low-voltage pulse, then builds up the arc discharge between the electrodes. Radioisotopes are added to the arc tube to produce initiating electrons which enable the electrode gap to break down instantly. This lamp can emit over 75% of its rated light output immediately after being switched on, if the arc tube has been preheated for at least 10 min. This can be useful for video camera lights or vehicle headlamps.
Spectral power distribution of light sources: New optimisation criterion
Authors: Stanioch W.
Published: December 2008

A new criterion for spectral power distribution (SPD) optimisation is proposed; this is evaluated numerically with a spectral utilisation factor (SUF). SUF is calculable on the basis of relative SPD and takes into account the luminous efficiency of (visible) radiation as well as the colour discrimination ability of the light source. The theoretical optimal light source is obtainable as a trichromatic line SPD of wavelengths 440-530-615 nm. The spectral areas of trichromatic SPD lines to optimise both SUF and colour rendering index (CRI) parameters have also been determined as 440-450 nm for blue, 530-540 nm for green and 610 nm for red lines at a spectral line (band) width of about 20-30 nm. Depending on correlated colour temperature and achromaticity requirements, various radiant intensity ratios of line (band) SPDS should be investigated for both the above criteria. The conclusions of the paper can be applied to improve the performance of practical light sources.