DIFFICULTIES OF ILLUMINATION
• Shadow will affect the amount of illumination, and its impact on people in working areas will depend on the task being performed and on the disposition of desks, work benches etc. the remedy is to use physical large luminaries or to increase their numbers.
• Glare occurs when there is too much direct or reflected light within the field of view. The most common cause of glare results from looking directly at unscreened lamps from normal viewing angles. Glare causes a decrease in contrast which results in decreased visibility and physical discomfort. Glare from sunlight coming through windows can be reduced by using exterior or interior blinds but this reduces the amount of natural lighting. It may be more effective to rearrange the workplace so that the windows are not in the normal direct field of view.
• Luminance is the amount of light reflected or coming from a light source or surface. It is important that there is not a great difference between the luminance levels for the task and that of the surrounding area. Luminance levels for the immediate area surrounding the tasks should be one third that of the task. The further from the task the less light is
needed.
• Reflectance is the percentage of light falling on a surface that is reflected. In an office the most reflective surface should be the ceiling; the least reflective should be the floor and in between are the reflectance of walls and furniture. In general, reflections from surfaces within the field of view should be minimized. Colour and finish are used to control
the reflectance of a surface. A totally black surface reflects no light. For a white surface the reverse is true. Also a matte finish reflects less light than a shiny one of the same colour.
• Contrast is the relationship between the light coming from an object and the immediate background, such as words on paper. High contrast is important for fine detail work. Using a black pen in place of a pencil
for handwritten copy will increase the contrast and improve the readability.
• The reflection of light falling on a coloured surface produces a Coloured effect in which the amount of colour reflected depends upon the light source and the colour of the surface. The choice of lamp is important if colour effect is required and can be as important a consideration as the illuminance itself. It can affect both the mood and the perception of size
in a workplace. Some of the colour effects are as :
• Blues and greens are considered relaxing or soothing.
• Pastel colours reduce the impact of colour.
• Cool colours such as blues and greens can make a space seem larger.
• Orange, yellow and brown colours are thought to be stimulating.
• Red and violet are considered alarming or aggressive.
• Reds and oranges can make a space seem smaller. Different types of lights will influence how colours are perceived. If the light source is not coordinated with the colour of a work area colours may be perceived as off or strange. Visibility may be more different.