Lighting in schools.

  • Department of Education and Science
Date:
1967
Catalogue details

Licence: Public Domain Mark

Credit: Lighting in schools. Source: Wellcome Collection.

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    involve him in looking repeatedly from one part to another, as a pupil will when looking up from the notebook on his desk to the chalkboard and then down again, the general brightnesses of each zone should be as nearly as possible the same to prevent unnecessary muscular effort caused by repeated adaptation of the eyes. This does not mean that there should not be contrasts of light and shade and colour in the detail within each zone, for this will be neces- sary to focus attention and allow detail to be seen easily. This crucial design problem of providing com- fort without a soporific flatness, and stimulus without discomfort is discussed further below. 40. Another important aspect of this process of adaptation is that the eye adjusts itself to the average level of brightness of the scene in front of it, in much the same way as a photographic light meter. This scene may well include areas which are much lighter or darker than the average — a splash of sunlight by the window on the one hand, and deep shadows behind furniture at the back of the room on the other. The occupant’s judgement of the brightness of the part of the room in which he is sitting will depend upon the average level to which he is adapted. If he is sitting on a summer’s day at the back of a classroom from which he can see a brilliant sunlit area by the window and bright clouds through it, his eyes will tend to adapt to the bright areas by the window. By contrast, the illumination on his desk at the back of the room will seem inadequate. If a window blind is lowered enough to cut out the direct sun and the view of the bright sky beyond, then the pupil sitting at the back of the room will adapt after a while to a lower level. The illumination on his desk will then subjectively seem to be higher even though it may, with the blinds down, be a little less as measured by a light meter. The control of the pattern of apparent brightness in the field of view, as well as the actual levels of illumination, is one of the main ways in which the architect can create conditions for good vision. Avoiding glare 41. While the eye is very adaptable, there are limits beyond which it cannot cope with extreme contrasts in brightness which occur side by side in the field of view. If these occur, glare is caused and visibility suffers particularly in the darker parts. This can be demonstrated by looking at a window from which there is a view of a bright patch of sky, or at a bright light fitting, and then trying to look into the shadowed area around it. If you then cover the bright source with your hand, you will see much more de- tail in the shadow. This glare is caused partly by the veiling due to the scattering of bright light in the eye, and partly because the eye tends to adapt itself to the highest average levels in its field of view. There is also the irritation caused by the constant effort to force one’s attention away from the bright areas. 42. Some forms of glare are self-evident, such as the feeling of discomfort bordering on pain that one experiences when looking directly at a bare lamp in a gloomy room. Other forms of glare are not so obvi- ous and may only cause irritation and discomfort after some while. Indeed, children may attribute their headaches and tired eyes to some other cause. This more insidious type of glare commonly occurs in rooms where a high level of illumination has been provided without giving sufficient attention to the quality of the lighting, and where there are a large number of bright light fittings or a range of large windows within the normal field of view. 43. The most common causes of glare are unscreen- ed lamps or fluorescent tubes; bright light fittings seen against a dark background; bright areas of sky seen through large unshaded windows; and the presence of dark surfaces of columns, transoms, mullions or window bars silhouetted against the sky (photographs 9 and 10). 44. The glare caused by the specular reflection of bright light sources in glossy paper or shiny instru- ments, on gloss painted walls or chalkboards which have lost their matt surface, or on polished desk tops can also be troublesome. While it is sometimes possible to move one’s head to avoid these reflections, this becomes increasingly difficult with higher illu- mination levels and the consequent close spacing of light fittings. 45. Ways in which the risk of glare can be reduced are discussed in the two following parts. But before this is dealt with in more detail, it is necessary to consider briefly some other ways in which the quality of lighting can be improved. Aiding concentration 46. The eye is attracted involuntarily to that part of the field of view which is the brighest or has the greatest contrast of light and dark, or of colour. This phenomenon is called phototropism and with appro- priate lighting it can be used to direct the pupils’ attention where it is required: for example, to the book on the library table or to the chalkboard in the lecture room. This can be done by increasing the amount of local lighting on the job in hand, such as with a pendant light over a library table, and this may be reinforced by making sure that the immediate object of attention — book, lathe, ball, instrument dial — is light-coloured and contrasty compared with other objects around it. Harsh contrasts are not necessary to achieve this effect; what is required is a gradual stepping-down of brightness from the work into the immediate and then the general surround- ings. Black print on a white page is clearly a good focal point; this is best seen against a light coloured desk top and beyond that a medium coloured floor of about Munsell Value 6. Vivid contrasts in the surroundings should be avoided in such circumstan- ces, as one’s eye would then be drawn to them by the same phototropic effect; a black-and-white chequer pattern on the floor would be most distracting when seen alongside one’s desk, and glaring windows or light fittings would cause the same trouble. It is of course possible to override this counter-attraction and keep one’s attention on one’s work, but this requires a conscious effort which becomes tiring and irritating after a time. 47. The exploitation of phototropism need not be confined to teaching rooms. It can also be used to draw attention to a change of level in a corridor or perhaps to a lively mural painting at the end of it. The role of modelling 48. Artists from Rembrandt onwards have used shadows to fix the position and confirm the identity of objects or of textured surfaces. In the same way directional lighting can help to place objects and clarify their shape and details. For the general run of school work it is usually sufficient for there to be an overall distribution of light, with modelling empha- sised by a punch of light from one direction, for example, from the main run of windows or from the nearest light fitting. But for more difficult visual tasks, such as operating a sewing machine, dissecting
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