Learning from the last 100 years of illumination history.
On the 18th November 2009 the British lighting community will celebrate the centenary of the formation of the Illuminating Engineering Society of Great Britain with a dinner at the Criterion Restaurant in London. This was the venue for an informal dinner held on the 9th February 1908 to consider a proposal by Mr Leon Gaster to establish a British Illuminating Engineering Society (IES): a body to incorporate not just those directly associated with the production of illumination but also artists and architects, physicists and chemists, ophthalmologists and physiologists who had an indirect involvement.
In January of that year, the journal The Illuminating Engineer had been launched with Leon Gaster as editor. Its aim was to provide a periodical solely for the consideration of all aspects of illumination, addressing the requirements of consumers and professionals, and keeping them in touch with developments.
Leon Gaster (Fig. 1) was born and educated in Romania, graduating from Bucharest University with a Bachelor of Science and Arts degree in 1890. This was followed with a period at the Electro-technical Laboratory at Zurich Polytechnic. In 1895 Gaster moved to England, bringing with him his keen interest in illumination. In 1905 he contributed a leading article to the Times Engineering Supplement entitled The Standardization of Electric Light, and in 1906 he was awarded the silver medal of the Royal Society for his paper Progress in electric lighting. Following the agreement to establish the IES he became its Honorary Secretary until he died in 1928. It is noted that the IES of North America had been formed in 1906.
The Illuminating Engineering Society ran from 1909 until 1978 when it merged with the Institution of Heating and Ventilating Engineers to form the Chartered Institution of Building Services (later to be become the CIBSE by adding Engineers to its title). Although this action enabled some members of the IES to gain professional engineering status the foundations of the organization changed, meaning that those members without engineering qualifications were not suitably recognized. It was considered that one of the strengths of the IES was the mix of disciplines and breadth of knowledge of its membership, but when the focus of the Institution changed some of this range of expertise was lost.
This situation was eventually resolved in 2000 with the formation of the Society of Light and Lighting (SLL) as a wholly owned company of the CIBSE. It has its own classes of membership and designatory letters. This enables it to recognize appropriately those professionals who have a place in defining the science and art of illumination.
[FIGURE 1 OMITTED]
As part of the centenary celebrations the Society decided that a publication describing the past hundred years of lighting in Great Britain should be produced, and David Loe and Rosemary McIntosh agreed to take on the project. It was published in May of 2009 and is entitled Reflections on the Last One Hundred Years of Lighting in Great Britain in time for the SLL and CIBSE Annual General Meetings (Loe 2009).
2 WHAT CAN WE LEARN FROM ILLUMINATION S HISTORY?
2.1 PROFESSIONAL LIGHTING INSTITUTIONS
Reflecting on the last one hundred years of illumination a number of things arise which show both strengths and weaknesses of the past. Perhaps by considering them, changes could be made to help the lighting profession develop and improve illumination in the future, or at least identify those areas that require further consideration? It is also possible that some of the certainties of the past were in fact not as certain as had once been presumed. But maybe they were as certain as they could be at the time.
When the IES began, although the importance of illumination was acknowledged, lighting was powered by gas, oil, acetylene and electricity and various companies were competing for the supremacy to provide the energy as well as the necessary lighting equipment. The IES provided an opportunity where discussions and comparisons could be made without favoring one system over another.
In 1911 the International Commission on Illumination was formed through the collaboration of many national illumination institutions. This developed into the Commission Internationale de Eclairage (CIE). The CIE provided (and still does) an international forum that worked to establish standardized units of measurement of illumination. In 1924 the photopic visual performance distribution (VX) was adopted, which eventually led to the internationally accepted candela, lumen and lumen/[m.sup.2] or lux.
To aid the development of lighting in the UK, industry and government research organisations participated in the study of illumination measurement, and by determining appropriate illumination conditions with respect to safety and visual performance for different tasks and applications. In 1936 the first British recommendations of task illuminance was published in the IES Transactions. Subsequently these were incorporated into the IES Code for Interior Lighting, then the CIBSE-Lighting Division Codes, and more recently those of the SLL. In the 1950s recommendations for daylighting conditions came from the Building Research Station, from a team led by R G Hopkinson.
One of the major benefits of the IES, and other similar institutions around the world, was that because it was an independent Institution it provided an impartial forum where discussion could take place between the different elements of the lighting profession and its clients, without the limitation of professional or commercial bias. It also provided a link between industry and government so that the needs of all could be addressed. In addition it was the vehicle by which international collaboration could take place.
However, as the subject and business of illumination developed, changes occurred in the Institution membership profiles. In the 1930s the members who concentrated on road lighting and related topics decided to break away from the IES to form the Association of Public Lighting Engineers (later to become the Institution of Lighting Engineers (ILE)). Much later, after the need for the independent lighting designer was established, the International Association of Lighting Designers (IALD) was formed, initially in the USA but now with involvement across the world. More recently the Professional Lighting Designers Association (PLDA) in Europe was formed with a similar role to the IALD. As time has gone on, because of this fragmentation, the position of lighting expertise has weakened, making it difficult for potential clients and users from other parts of the building profession and government to know who to consult at a time of need.
This fragmentation of the illumination community is a pity as it detracts from the universal aim: to provide appropriate, high quality illumination for all applications based on the best modern evidence gleaned through research and experience.
In Britain recently, conversations have taken place between various elements of the lighting profession but no clear route for collaboration has yet been established. Nonetheless discussions continue. One of the problems is their different professional profiles, including the education and qualifications of those concerned. But progress will only be possible by all the bodies contributing. Perhaps this could be achieved through a 'federation' type institution to embrace all those involved? This could also help formulate education programs and a professional recognition that serves everyone. Sadly, as each new institution has been formed there have been criticisms of each other, which is unhelpful. The past has shown us that each sector has a role to play and that it is only through collaboration that lighting can develop.
2.2 ILLUMINATION SCIENCE (AND TECHNOLOGY)
One of the major problems with illumination is that the human response to light and lighting does not follow a standard physical relationship. Over the years scientists and physiologists have endeavored to find ways to describe numerically a lit environment based on what we see and to enable designers to provide better and more comfortable illumination.
However, because of the subject's complexities the solution to one problem can cause unforeseen consequences. In the 1950s the IES Glare Index System was developed to reduce the possibility of visual discomfort through over-bright luminaires when seen in the normal field of view (FOV). This provided a system that defined the characteristics that affected the degree of glare, together with numerical recommendations. This encouraged the industry to produce glare-free luminaires and installations. But at times this had a negative effect by creating what appeared as an under-lit environment, even though an appropriate task illuminance was provided. This indicates that appropriate illumination depends not only on task illuminance and the elimination of discomfort glare but also on the lit appearance of the environment. This led to studies involving subjective assessment rather than mechanical tests of visual performance to explore the human response and performance to illumination, and this work continues to the present day.
A further development in the 1960s was the introduction of systems for quantifying the color performance of light sources, which, at the time, was a major advance, giving the industry the CIE Color Rendering Index (color rendering index (CRI)) and the CIE Correlated Color Temperature (CCT). This led lamp manufacturers to develop de luxe type fluorescent lamps with an improved CRI but it was usually achieved at the cost of a reduced efficacy, thus making installations more costly.
This caused H E Bellchambers, of Thorn Lighting, to examine the question of 'visual clarity'. The suggestion being that a lamp with a high CRI would result in a higher task performance through the greater clarity of the task, and therefore a lower illuminance was permissible, thereby countering the issues of lower efficacy and increased cost. Unfortunately this question was never properly resolved but perhaps it deserves further investigation.
Since the launch of the lamp color performance systems, experience has shown that they are not sufficiently detailed to evaluate the color performance of modern light sources and more work is necessary in this area.
2.3 LIGHTING DESIGN
But what about lighting design? The illustration (Fig. 2) shows an office c1910 lit mainly by daylight; note the position of the desks relative to the windows. It also shows that each work position has its own task light, presumably with an independent on/off switch. The room also has a ceiling mounted, three-arm pendent luminaire with glass shades to diffuse the light and minimize glare, which provides background illumination. The lamps would have all been incandescent. This was at a time when electricity was very expensive and lighting equipment was also costly, so the design addresses function as well as running costs.
This combined approach would probably have continued until the invention of the tubular fluorescent lamp around 1940, which provided cheaper illumination and the possibilities of a higher task illuminance from a regular array of ceiling mounted luminaires. Coefficients of Utilization and Glare Indices enabled engineers to provide glare free installations with a near uniform horizontal plane illuminance by calculation. This meant workstations could be placed anywhere in the room.
[FIGURE 2 OMITTED]
The topic of lighting appearance has already been touched on, and some considered it important from the very beginning of illumination studies. One of the earliest was Matthew Luckiesh in his book of 1916, 'Light and Shade and its Application'. However, it was probably J M Waldram's work in the UK, in 1954, which started to consider the lit appearance in an analytical way. Since that time many other researchers have undertaken studies into the lit appearance of spaces with the aim of understanding what affect lighting appearance can have on the occupants in terms of performance and health.
These include John Flynn in the USA in the 1960-70s, and the team at the Bartlett School, University College London in the period 1980-2000, which included the authors, but there were others too. The work of these researchers focused on what people preferred and how to describe it numerically with the idea that these installations would enhance human well-being and hence performance.
More recently (LR&T 2008) Jennifer Veitch and Guy Newsham, from the National Research Council of Canada, who have been investigating lighting appearance since the 1990s together with Peter Boyce, then with Lighting Research Centre at Rensselaer Polytechnic Institute, and Carol Jones from Battelle Memorial Institute, showed that benefits could be shown by using a 'linked assessment analysis' approach. But for this aspect of illumination to be accepted further studies will be needed involving researchers, designers and members of the manufacturing industry to establish practical solutions based on the accumulated information, and to measure any benefits in performance and costs.
Nonetheless, by combining the requirements for task illuminance, glare control and lighting appearance, improved illumination could be provided but also with reduced energy consumption because the need for blanket illuminance over the whole space may not always be necessary. In fact this approach may show improved human performance and health through a lit environment that satisfies the occupants in more ways than just being able to see the task.
2.4 LIGHTING ENERGY EFFICIENCY
This brings us to the current most pressing subject demanding attention - that of lighting energy efficiency. It is estimated that lighting in the UK consumes about 20 percent of the total electricity generated. This is not an insignificant amount and it needs to be reduced. Over the recent past the lighting industry has made significant advances in improved lighting products that consume less energy. These include lamp efficacy, luminaire optical efficiency, as well as lighting controls that can operate either manually or automatically. However, more needs to be done to reduce the electricity used for illumination but without losing lighting quality or the advances made by the lighting profession over the last 100 years.
Recently, on the basis of their low efficacy, governments from around the world have banned the sale of many of the traditional incandescent lamps developed over the last 100 years. It does not appear that the lighting Institutions were consulted, and that the decision was made in haste with the intention of forcing the use of Compact Fluorescent Lamps (CFL). These, according to the industry are considerably more efficient. But compare this to the almost universal outcry: that the light output of an incandescent lamp appears greater than the light output of the Compact Fluorescent Lamp of equivalent lumen output.
The lamp industry claims that typically a CFL has an efficacy five times greater than an incandescent lamp, but many users consider that three times is more likely. So is there something wrong with the measurement? Remember the efficacy of a lamp depends on the relationship between the power consumed (watts) and the visual effect (lumens) currently based on the standard CIE spectral response distribution for photopic illumination, the VX distribution. Is it possible that this is not sufficiently accurate for today's world? This issue must be resolved if we are to ensure that the best illumination can be provided with high-energy efficient equipment, and confirm that we are using an accurate method of measurement. Also it is essential that before further hasty decisions are made, which are based on information that may not be correct, the appropriate Institutions are consulted.
It seems unlikely that the general lighting service (GLS or A lamp) tungsten filament lamp can be saved from extinction but there may still be time to save the halogen versions, which would be a great result.
Another area for consideration is the way many lighting installations are provided by a regular array of ceiling mounted luminaires providing a uniform illuminance over the whole working plane. On the face of it this seems wasteful. Perhaps a better alternative would be to provide a lower uniform illuminance that is topped-up to the normal recommended task illuminance locally as required, and which can be controlled both automatically and manually for optimum user satisfaction and energy efficiency. There may also be a need for some complementary illumination that provides an appropriate lit appearance that is sympathetic to the architecture and the activity of the space. Hence, for improved energy efficiency in lighting it is the installation design that will provide the greatest hope. This area of illumination needs further investigation by both designers and the lighting industry to determine possible solutions.
So far only interior lighting situations have been considered but a similar consideration should be made on road lighting. Generally the approach for road lighting has not changed for many decades but vehicle lighting is now much improved and can effectively illuminate the roadway, but on its own can be visually tiring. Is it time to consider lighting the surrounding area to a low illuminance using lamps that have a high efficacy under mesopic visual conditions and reduce the driver's visual stress of looking down a virtual tunnel? This could also be combined with solar powered cat's eyes, perhaps?
Over recent decades the amount of resources invested in illumination research and development, either by industry or governments, has reduced considerably, but this will need to change if we want good quality lighting installations that serves the users well, and that uses energy efficiently. This will need to be supported by industry and governments for it to be undertaken. It will also require strong Institutions that have a membership that can speak for all aspects of illumination for further improvements to be achieved, which will be essential for illumination to develop for the twenty first century. If not, lighting will just become a commodity rather than an important element of environmental design that has an influence on people's productivity and health, as well as energy efficiency. Lighting has the power to enhance the visual environment for human pleasure and stimulation.
Much of the above draws from the British experiences but is likely to apply equally to other parts of the world.
Loe D, McIntosh R. 2009. Reflections on the Last One Hundred Years of Lighting in Great Britain. Society of Light and Lighting, CIBSE 2009. London. 112 p.
Invited article by: David Loe, MPhil, CEng, Hon. FSLL, FIESNA and Rosemary McIntosh, MSc, MPhil & MSLL
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|Author:||Loe, David; McIntosh, Rosemary|
|Date:||Oct 1, 2009|
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