Good lighting in an office ensures that one can read documents easily and that the contrast between the monitor and the surrounding light is not to big. Not enough light may have a bad influence on posture when people get closer to their documents. Too much or too little may be bothersome as well when working with monitors.
Illumination intensity: 500 Lux
The legislation and European standard NBN-EN 12464-1 regarding interior lighting, recommends an illuminance in the region of 500 Lux for at general office work. The Dutch occupational health and safety directive uses a zone of 200 to 800 Lux as acceptable for computer work. This illumination is always the result of the natural light and artificial lighting.
Daylight: rectangular on window
A VDU workstation is best rectangular to a window and at least two metres away. If this is not possible, then the light should be shielded by means of sun blinds. When installed in a rectangular angle to the window the light will enter the work surface sideways and is bounced off the monitor sideways as well and wont reflect in the screen to the user. In addition to this (in the ideal world), for right-handed people it is best for writing that the light comes in from the left. In that case there will be no irritating shadow on the desktop.
Other space planning arrangements of the workstation, more will introduce more disadvantages. Facing the window, the contrast between the bright outside light and the computer screen will be way too large. The eyes will then need to customise continuously what will incur eye problems. Facing away from the window, one works in his own shadow and this prevents good even lighting of the work surface. The light of the sun may also bounce back from the screen, which gives annoying reflections.
In the offices of Perfect Image in Newcastle as of the above has been carefully looked at when designing the floorplan for their office refurbishment in Newcastle.
In most cases, fluorescent or LED lamps are used for general lighting. When choosing the type of lightingh, two important characteristics are important to take into consideration: color temperature and color rendering index. For VDU work a color temperature of between 3000 and 4000 K and a colour rendering of more than 80 Ra is recommended. These values can be read off from the code on the lamp. In the code 36W/830 denotes the 30 on a color temperature of 3000 k and 8 on a colour rendering index between 80 and 89.
When a row of fluorescent tubes are positioned at a 90 degree angle with desktop, it is best to position the desk in between the fixtures. This also applies to the small square luminaires with fluorescent or LED bulbs. The goal remains to avoid disturbing reflections in the monitor. An even light distribution and the good reflection values of the ceiling, the walls, the furniture and the floor will all contribute. As a general rule, you can say that the reflection index decreases from high (white ceiling) to low (grey floor).
Fluorescent tubes are hung in a luminaire box with deviders (matt or high-gloss). This is why the light doesn’t fall directly in the eyes of the office worker. By ways of reflection in the fixture the light will also better be distributed into the space. The fluorescent tubes are usually combined in even number. The reason for this is that they work on alternating current. One tube does actually have a stroboscopic effect. Because the brain will stabilise this, fatigue will occur at the end of the day. When the fluorescent tubes are combined per two, the electric phase is reversed, creating a more stable transmitting of light.