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Good lighting for fine pictures
By William Allen, CBE., Bickerdike Allen Partners
People who go to museums, art galleries and great private homes are familiar with the frustration of the bad lighting of pictures. Often incandescent striplights are placed at the top, lighting the upper few inches of a painting, the top of its frame, and some of the wall above it, but not much else.
In fact it is really doing more than this, for it is often lighting the top of the picture well beyond safe conservation levels, and overheating both it and the frame as well, while the reflected glare of the lamps draws attention to the light fitting and away from the subject matter of the painting. Colour rendering is also poor because it becomes unbalanced by the orange emphasis in the spectrum of incandescent filaments, enhancing the warm colours and turning the greens and blues towards greyness. It is unworthy as illumination for fine works of art.
In the late 1980s a small group we had formed to re-light the Chapel Royal at Hampton Court was invited to undertake similar work at a great Rothschild mansion, Waddesdon Manor, about thirty miles Northwest of London, close to Aylesbury. The group comprised an electrical engineer/lighting designer, Paul Ruffles, a precision manufacturing engineer, Cliff Mills and ourselves, museum architects and lighting designers.
Waddesdon Manor was built in the late 1870s by a French Rothschild, Baron Ferdinand, in the manner of a French château and sits grandly on its English hill. It was given to the National Trust by a later owner, Mr James de Rothschild but the present Lord Rothschild remains active in its management and has generously restored the house and put it into good museum-quality working order together with rehabilitating the gardens and grounds to their former splendour.
The collection, for which the house was partly designed, is of world class and principally comprises pictures, furniture and carpets, seventy sets of its original curtains, grand panelling, fine family china and much else, all of which was taken into account, so that a coherent result throughout the house and collection could emerge from the work.
The lighting received a top award and the house as a whole was named Museum of the Year for 1997, as well as best National Trust property.
Pictures are the principal subject of these notes and with the support of Lord Rothschild and the Keeper of the Collection, Miss Rosamund Griffin, we were able to develop equipment and discover ways of utilising it at Waddesdon by which all the disadvantages described above were eradicated and improvements were made taking the picture lighting technology as a whole into a new dimension.
The light sources
The equipment used relies upon the use of tungsten halogen lamps as light sources. These are small, highly efficient capsules about 17 mm long and 66 mm in diameter, containing a filament and halogen gas. They operate on 12 volt power, thus requiring transformers. These are now very small and can be fitted in an envelope on the backs of the frames or in some convenient and unobtrusive place nearby.
The capsules as we use them are of quartz in a range of small wattages; They are also made with clear glass but the quartz prevents the emission of most of the UV. Clear glass types in higher wattages, 20, 35 and 50, are permanently set in multifaceted reflectors of 35 or 50 mm diameter and sealed by a glass cover which filters out most of the UV. The facets of these reflectors are so shaped that about ninety per cent of the visible light emerges in beam spreads of 7° to 60° with the remainder acting to soften the edges of the beams.
We use the capsules in a range of equipment sizes from the minute, for small pictures, through medium sizes containing up to three capsules; we then move to the more powerful dichroic lamps in larger cases used on large pictures. In all but the smallest capsule unit the lamps are held in an inner, directable holder, with an outer case separately rotatable to screen the inner holder from view. A tube containing capsule lamps is often made for supplementary bottom lighting, though normal capsule fittings can equally be useful in this way. Further development of this equipment takes place as new challenges are presented.
A critical feature for success is the location of the lights at the tops of pictures, because sources must be placed farther above pictures than has been customary if glaring reflections of the lamps are not to be visible in the upper part of a painting. It is essentially a simple matter of geometry and of having equipment which provides elegance for use in this way, but it is vital for good lighting because these glaring reflections are unacceptable.
The distribution of light on pictures
Pictures should appear to be reasonably uniformly lit, but not necessarily perfectly. Perfect uniformity can be obtained by diffuse illumination but can look so full as to become boring. As an American colleague said to this author while visiting a great European gallery, "These Rubenses are so uniformly lit by this diffuse lighting that it looks as though the originals are out on loan and we are left with posters".
With the equipment described here it is a simple matter to get an acceptable appearance of uniformity with enough control to provide the emphasis needed to ensure that the principal subject matter remains just that. It can be obtained with this equipment over the range of light levels now regarded as appropriate for conservation from 35 or 40 lux to up to 200 or 250. This equipment offers no risk of overheating to paint or textile surfaces or to papyri.
An unusual point now regarded as very important is a sense of richness which picture surfaces acquire with this lighting equipment. It contracts strongly with the boring appearance of the Rubsenses mentioned earlier and is apparently created by the fact of the capsule and dichroic lamps being in effect point sources in contrast to the diffuse quality of the ambient light that prevails throughout any room by reason of inter reflection and other sources of natural or artificial light. Its ability to reveal gold thread in fabrics is something of a revelation, for example.
In addition to the enhanced appearance of richness in a paint surface, there is a sharper sense of the third dimension in a picture. Faces are rounder, perspectives are deeper. Arguably the richness is due to micro-modelling of the surface texture by tiny highlights and shadows but the cause of the strengthened three-dimension effects has no present explanation.
There are also mysteries one would like to be able to explain. Two Rembrandts which had hung comfortably as a pair for some years were re-lit with the dichroic picture lights, whereupon it appeared that while one was undoubtedly genuine, the other had a possibly less than pure lineage. In a second case - a portrait of Elizabeth I - the face was painted very smoothly in contrast to the remainder of the picture, possibly using a different medium. It remained deadpan under halogen capsules but came to life under a pair of small dichroics. It would be very desirable to discover the reason for this.
These capsule and dichroic sources have the considerable advantage that the spectrum of their light is not significantly different from that of sunlight, which is a great gain over the excessively warm output of tungsten or the fragmented, rather grey spectrum of fluorescents, it may even be regarded as having the same quality as emergent sunshine on an overcast day.
Balance
Balance of brightness, picture-to-picture, pictures-to-walls and to the room ambience, and room-to-room have been found to be more important than previously thought, now we have equipment which enables us to manipulate these characteristics, and sometimes one, or a few pictures will determine what general level should be used. Pastels, in particular, can be determinants because they are not much less sensitive to fading than fabrics.
Frame brightness
Frames perform two principal functions. They mediate between a painting and the surrounding wall surface, and they demarcate the boundaries of the composition. They are designed to do such jobs stylishly and with charm, not abruptly and not in competition with the painting. When the full picture area of an individual painting is lit there is a risk that spillage will over-light the frame's ornament so that shiny highlights and sharp shadows develop and take attention away from the painting. A further problem can be caused by an overlit frame casting strong shadows on the wall. Thus there is much to be said for using lighting which enables some reduction of brightness towards the edges of pictures and to their frames. We have been successful in finding ways to do this.
Most of what has been said here relates to the individual lighting of pictures or other exhibits. In large institutional galleries the problem is different. The approach now customary is to light the whole hanging areas more or less uniformly from distant tracks, and then contrasting highlights and shadows on frames are reduced, shadows around pictures virtually disappear, but the pictures themselves are lit uniformly and smoothly, losing the richness and characteristics gained from some point source content in their illumination.
Picture glass
Mention must be made about the kind of glass used for pictures when this is thought necessary for protection. There is a familiar greenishness about ordinary window glass or float plate, visible most obviously at its edges, and due to a contaminating iron content. When this is used on a picture the viewers are, in effect, looking at the painting through a green filter and its causes greying of the warm colours, most notably those of skin on portraits and nudes. Iron-free glass is available, and although it is a little more expensive, it should always be used when glass is thought necessary on a picture.
Most of what has been said here relates to the individual lighting of pictures or other exhibits. In large institutional galleries the problem is different. The approach now customary is to light the whole hanging areas more or less uniformly from distant tracks, and then contrasting highlights and shadows on frames are reduced, shadows around pictures virtually disappear, but the pictures themselves are lit uniformly and smoothly, losing the richness and characteristics gained from some point source content in their illumination.
Seeing at low illumination levels
Conservation lux levels of 200-250 have been mentioned, and these are not high, but 50 lux is really quite low. Can one still see detail and colour acceptably? This depends on one's level of vision adaptation, and the managing of interior design in order to put peoples into a good state of adaptation for light levels is the key to success with all conservation lighting. Ways of doing this are not easy to discuss briefly but in principle it means not having things like bright lampshades or uncurtained windows near the line of sight of pictures, white or bright wall surfaces, or sky vies or bright skylights in view which light the room as a whole to levels approaching or exceeding those intended for the pictures themselves. Human adaptation is out of one's personal control; the design of the indoor environment determines its level and therefore a person's visual efficiency. It has also been noticed that in galleries where pictures are lit by so-called wall-washing lights set in the ceiling, one's eyebrows and eyelashes pick up this light and their brightness then adversely affects one's adaptation. We call this eyebrow glare.
These are matters which it is difficult to evaluate or predict quantitatively; one has to build up judgement by experience and observation. It is well known that one sees only what one understands, and it is a great help to shield one's eyes from suspect areas of brightness when looking at pictures in order to see to what extent an improvement can be sensed and then try to explain it so it can be corrected.
Energy economy
The lamps used in this approach are not only much more efficient in themselves than incandescent filament types, but have two or three times the life expectancy, and because low illumination levels can be successfully if one understands adaptation, substantial reductions in energy consumption take place, usually not less than forty per cent or so and, in one case, as high as eighty per cent.
William Allen, CBE, B.Arch, RIBA, Hon LLD
Bickerdike Allen Partners
121 Salusbury Road, London NW6 6RG
Key points for success
Experience has shown that success lies essentially in good coverage of this picture, with some light emphasis on the principal subject matter. An anecdote from the Frick in New York summarises this very nicely:
We had very recently re-lit all the rooms except the top-lit rooms at the rear when an experienced gallery visitor came by who had not seem the collection for some sixteen years. He wrote enthusiastically to the Curator to congratulate him on having had all the pictures cleaned at last. The Curator replied that is was more than twenty years since they had cleaned any paintings; had he not noticed the re-lighting? It seems to be a fact that when a picture is lit well, it commands your interest to the point of ignoring how it is lit.
As for energy economy, which will pay for such work in the end, this depends on understanding how to get high visibility at low illumination levels by good management of the indoor environment to provide comfortable visual adaptation.
At present it has been found that while the equipment has the very extended capability described, it needs to be used by people who understand how to use it if is potential advantages are to be realisable in practice.
Waddesdon Manor has already led to numerous other projects in Britain, North America and Europe.