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Glare Control Battens and recessed fittings with flat panel diffusers emit light over a wide angle. This is good for general lighting but becomes a problem in offices where computer screens are used. Light sources of these types will reflect in the computer screens and create glare which makes the screen harder to work with. This problem is worse on older computer systems that use a predominately dark screen. The solution is to control the angle at which the light is able to leave the luminaire. If we can keep the light angled mainly downwards with reduced output at angles above 55 degrees the problem will be greatly reduced. Such fittings are called low brightness luminaires. A room full of low brightness fittings will appear rather dark as there is very little vertical illuminance (on the walls) because most of the light is going downwards. There are three methods of controlling the light angles: 1 - Priamatic Diffusers The use of prismatic diffuser panels as used with T bar and plaster recessed fittings is to lower the light intensity in the direct glare zone of 55 to 90 degrees (compared to a non prismatic opal diffuser). The prismatic panel lowers the brightness in the glare zone and puts out more light in the near vertical angles (more light on the area below the panel). Prismatic diffusers must be installed with the prisms on the outside of the fitting. Common prismatic panel types:
Silver tint versions of K12 & K19 are available. The silver tint versions reduce light output by up to 25% but give better glare control. 2 - Egg Crate Diffusers There are several versions of these plastic open grid type of diffusers. The most common types are:
Both of these will give a light output reduction of about 20% compared to a K12 panel as the light opening area is considerably reduced. 3 - Aluminium Louvres These are the most effective way of controlling the light output with minimal reduction in the output level. |
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