The sources of light and lighting at work.

Succeeding in lighting industrial, office and other work environments is dependent on many factors. Good result is not guaranteed if only one of these factors is taken into account. It is essential to choose appropriate light sources and use them correctly for different tasks. Although the amount of light and its composition is considered satisfactory for a certain task, glare and reflected glare still cause inconvenience in the work places making the performance of visual tasks difficult. The lux and luminance levels of the work areas regulate the size of the observer's pupils. The size of the pupil determines for its part how easily and quickly eyes can be accommodated for a sight distance. The indirect disadvantages caused by poor visual conditions are often significant. For example at display work reflected glare does not only slow down reading. The effort to avoid the reflections from the screen by changing the direction of observation effects the working positions. Inconvenient posture may cause pains in the neck and back. In lighting design the problems of age vision are taken into account. We should also bear in mind the significance of the colour of light when considering these problems.