With increasing age, less light reaches the retina so higher levels of illumination are required for doing fine tasks. However there are a small number of people with low vision who find lower levels of illumination beneficial.
In general it is better to maintain a consistent level of ambient illumination, but give individuals the ability to control the level of task lighting. However it is essential to minimise glare and stray reflections.
The level of illumination required for optimum performance is not the same as the maximum level chosen as comfortable by the user.
In various standards and guidelines, the specifications for domestic illumination vary considerably but the consensus is for minimum light levels of 100-200 lux in living areas but at least 500 lux for fine tasks.
For public access terminals, there may be other considerations such as security. If the area immediately around an external ATM (cash dispenser) is well lit but the ambient level of illumination is very low, it is less easy for the user of the ATM to see someone approaching.
For a public telephone booth, it is possible to have a low level of illumination, but automatically turn on task lighting as soon as someone enters the booth. Ideally the user should be able to adjust their task lighting.
For many ICT terminals, a common problem is reading a visual display where the contrast has been degraded by sunlight, reflections from fixed illuminaires or by deterioration of the display itself. Therefore it is important that the contrast is checked at periodic intervals, and the display replaced or repositioned if necessary.
- If the potential users include older people, the ambient illumination should not be less than 200 lux
- Provide adjustable task lighting
- Check for reflections from fixed luminaries and sunlight
- Periodically check the contrast on any visual display
- AS 1680 (1995) Interior Lighting
- BS 8300:2009 Code of Practice for the Design of Buildings and Their Approaches to Meet the Needs of Disabled People
- The Building Act 1984 and it's Building Regulations: Part M - Access to and Use of Buildings (2004 edition); Part L - Conservation of Fuel and Power in Dwellings (2002 edition)
- Chartered Institute of Building service Engineers/Society of Light and Lighting Code for Lighting, 2002
- CIE Publication 123, Low Vision: Lighting Needs for the Partially Sighted. 1997