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Glaring mistakes

The text below is from an article submitted to Design Week magazine which appeared in May 1997 entitled ‘Glaring mistakes’.

Lighting Screens or screening lights

Why is there so much concern about the lighting of offices where display screens are used? The screens them selves sit there glowing quite happily whatever the lighting of the room. Well of course the lighting isn’t there for the benefit of the screens, but for the poor mortals that have to operate them. Even if you are quite comfortable with the lighting around your screen and the room, you are probably aware that there can be problems with reflections from the screen and poor contrast between the screen images and the room background.

These problems are often easily overcome. The first and most common problem, that of screen reflections from windows or lights, is usually solved by moving the screen or re-orientating the workstation. Of course sometimes this is not possible and action has to be taken to limit the brightness of the windows or the lights.

Altering the brightness of the windows, or rather the brightness of white clouds seen through them, is not as easy as it seems at first. The window is an important source of contact with the outside world and if it is screened-off completely then there can be a sense of disconnection, especially for those remote from the windows. It is better to try to screen the high bright areas of the sky by using a simple roller blind or horizontal venetian blind, as this maintains some view out in the lower part of the windows. Curtains or vertical louvre drapes that have to be drawn across the entire window often result in a loss of a view out. Whatever method is chosen simple local control and adjustability of the screening is important. This allows the users to feel more in control of their environment and allows them to determine the exact degree of shading or admission of daylight.

It should be remembered that the window is often also a source of direct sunlight i.e. thermal gain and glare, which can be a cause of considerable discomfort, especially for users near to windows. Where there is direct sunlight coming through a window it is important that the density of any screening is high otherwise the sunlight hitting the screening will turn it into a large bright object providing a source of glare and screen reflections for most of the room occupants. Where the windows provide means of ventilation then the screening system must be selected to allow users safe and easy access the window catches. The movement of air through a window can also cause annoying flapping or vibration of certain types of screening systems.

The subject of selecting lighting systems for offices is always controversial. There are many lighting designers or manufacturers who will advocate one magic solution or another – uplighting, highly controlled downlights or perhaps task lighting. All these systems can work well if correctly chosen for the types of screen and environment that they are intended for , but – and this is a big but – they can all be disastrous if misapplied. Sharply controlled downlight in a room with rather dark carpets and furniture can result in a very gloomy environment. Uplighting in a low room can result in hotspots on the ceilings which appear as bright blobs on the screens. Where there is the ceiling height a good general solution is some form of combined direct and indirect lighting suspended from the ceiling. This provides soft background light from the ceiling with some direct light to give good modelling and working light.

In terms of the balance of lighting between the workstation and the wider office, this is an area that is often overlooked by many lighting designers, but can be most important for the users of the room. Poor balance of the lighting can leave the screen operator working in a pool of light whilst the room around appears gloomy or oppressive. Conversely bright windows or brightly lit room surfaces along the line of sight beyond the screen can be most distracting. Again, getting the right sort of light in the right place is the most important way to get a good balance of light in the room. Light too near to walls can cause bright flashes, but lights too far from walls can make them seem dark.

Just remind anyone who talks to you about ‘lighting for VDUs’ that the screens can take care of themselves – it’s the users of the screens who should be considered when the lighting is being planned. If they, or you, need more design advise then CIBSE produce a lighting guide on ‘The visual environment for display screen use’. They can be contacted on 0208 675 5211.

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