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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    202. In practice, these four points are inter-related. The first two are closely linked, for the choice is broad- bright one. A useful rule of thumb applicable in most viewing conditions is that the screen width should be about one-sixth of the distance from the screen to the back of the audience. So a screen 4 ft wide (or 4 ft square) will suit a room 24 ft deep, and a 5 ft screen will suit a room 30 ft deep (the maximum distance from a chalkboard — see paragraph 196 (1)). Tele- vision and back-projection screens are exceptions to this rule, for they have much greater brightness con- seated more than ten times the screen’s width away, that is, 20 ft from a 24 in television set. Television sets should not be placed in front of a window. 203. For general purposes use in schools, screens with a matt white surface are preferable, as they re- flect light more or less evenly in all directions. Glass- beaded or silvered screens will give a brighter image viewed along the axis of projection, but the bright- ness falls off rapidly outside an angle of about 30° from the axis. If the projector is placed at least as far away as the back row of the audience, this will ensure that none of the audience is distracted by the stray light from the projector. A 16 mm projector with a lens of 50 mm (2 in) focal length will fill a 48 in screen from 20 ft, or a 60 in screen from 25 ft. A 2 in x 2 in slide projector with a 100 mm (4 in) lens will filla 48 in screen from 12 ft or a 60 in screen from 15 ft. Screens which are square will allow slides which shown most conveniently. To avoid a distorted pic- and in line with its centre point. Viewing conditions will in the first place depend upon the quality of the equipment used, but even the most elaborate equip- ment will be ineffective if it is not set up properly and if it is not used in the correct lighting conditions. 204. For the present purpose it may be convenient to divide projection equipment into three groups: first, those which may be seen in normal lighting condi- tions; second, those which are seen best in a partially darkened room; and third, those which require full blackout. In the notes that follow, it is assumed in each case that a 48 in screen will be used, viewed from a distance of not more than 24 ft. Normal lighting 205. At present, equipment that can be used in normal lighting conditions, where there is a general level of illumination of about 10 Im/ft? but not full sunlight or very bright daylight, is limited to tele- vision, some back-projection equipment, and certain overhead projectors. There are obvious educational advantages in visual aids which allow the teacher to see the class (and vice versa), and in being able to use the equipment for brief periods in normal lighting without interrupting the lesson each time with the rigmarole of blacking-out. There may also be econo- mic advantages, for it is likely to be more sensible to use the substantial sum that would be spent on black- out for a powerful projector instead. However, al- though more equipment suitable for projection in normal lighting will/no doubt be developed in due course, at present arrangements for some degree of blackout must be made in rooms where visual aids will be used regularly. Partial blackout 206. Much of the normal projection equipment used in schools can be viewed quite satisfactorily in par- tial blackout (or ‘dim-out’) conditions where the duced to 1-3 Im/ft?. These conditions could be brought about — on days without full sunlight — by drawing opaque curtains, or by turning flat the slats of normal white venetian blinds, or — after dark — by switching off all but one or two of the lights at the back of the room. Such conditions enable the pupils still to see their teacher, and to take notes. Equip- ment used in these circumstances should preferably be slide or cine projectors with 1,000 watt lamps, or more. Full blackout 207. Full blackout will be necessary where low- powered projectors must be used, or where the effec- tive brightness of the projected image is low (as with many micro-projectors, or episcopes which rely upon a reflected image), or where it is important to be able to discriminate close differences in tone or colour. Some optical work will also need full black- out, but a bay off the main laboratory may be all that is required to be blacked-out. Full blackout will need light-proof blinds of the types described in paragraph 95. Special arrangements for ventilation will have to be made. Complete blackout has the drawback that notes cannot be taken. 208. In addition to the rooms used primarily for teaching, a school will contain many areas used at times for teaching, and at times for general social activities. These will include assembly halls, dining areas, common rooms and some larger circulation spaces, such as entrance halls. Often the problems of planning and lighting these parts of a school will spring from their multi-purpose use: the hall which is used at times for physical education will also be the setting for dramatic work; dining may take place in part of a spacious entrance hall. 209. The main hall, with its associations with special occasions in the life of the school, its generous di- mensions with the opportunities of long vistas, its many uses — formal and informal — for drama, music, dance, debate, gives scope for imaginative and varied contributions to the whole design by both day and artificial lighting. Because of the wide variety of uses to which the hall will be put, and the many planning and structural solutions which are possible, it is very difficult to generalise about the lighting. However, there are a number of recurrent problems” that can be usefully discussed. 210. First, the sheer size and height of the hall tempts architects into providing unnecessarily large window areas, sometimes glazing all of one wall. This may be a dramatic solution, but it rarely leads to good light- ing conditions and can create other problems of ex- cessive solar heat gain in summer, of thermal loss in cold weather, and of blackout which will probably be needed for dramatic performances and film shows. In a hall of, say, 3,000 sq ft, about 600 sq ft of glass should be sufficient, if distributed in the right manner, to provide an adequate level of lighting. As in other rooms, cross lighting will help to reduce ex- ———
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