Lightening is important both at home or work. Our eyes can adjust to a wide range of brightness, but inadequate lighting makes it difficult to work and contributes to accidents. Poor lighting can also result in eye problems. If we cannot see well we may easily suffer from tiredness, over-exertion and headaches.
The eye can be compared to a camera. When rays of light fall on the eye they are broken up by a lens system consisting of the cornea, the lens and a watery liquid between the two. The space inside the eye behind the lens is filled with a transparent liquid through which the rays pass to form an image on the retina, the curved screen at the rear of the eye. The retina is like a light-sensitive film in the camera.
The eye cannot focus simultaneously on objects which are close and far away. When we rapidly change our focus on objects at different distances, the eye becomes tired. This can occur in inspection or assembly work. In such cases there should be plenty of light available, particularly at the area furthest away from the eye.
Changes in the eyesight
Everybody’s eyesight is different. Some people have weaker eyesight. Moreover, the ability of the eye to adjust rapidly to different distances decline as we grow older. Many people need glasses by the age of 40—50. It is particularly important that older people have adequate lighting.
Lighting requirements at workplaces should make good use of natural light and at the same time avoid disturbances by sunlight or other light sources.
Artificial lighting is not as good as daylight, but daylight varies with the seasons and weather conditions. Consequently the amount of lighting required should be determined regardless of the amount of daylight. Adequate lighting should reach your work area without being shadowed by you or part of a machine. This holds true with either daylight or artificial lighting.
It is important to get as much daylight as possible. Stored material should not be piled up where it blocks daylight. Windows should be kept clean, inside and outside. If the window faces a wall, that wall should be painted white so as to reflect more daylight into the work area.
In factories, windows and skylights can help increase lighting. However, adequate general lighting should be provided as sunlight may become inadequate at different times of the day. Walls inside the factory should be painted light colours to make the most of daylight as well as artificial lighting.
The eye has to make an effort to distinguish between objects which have little contrast. It can be particularly difficult to distinguish such objects when lighting is dim. Moving from a very bright area, (from direct sunlight or acetylene lighting) to a shaded area can be dangerous, as the eyes require time to adjust to the different lighting, and therefore vision may be temporarily impaired. In transport routes sharp shadows can lead to accidents if lighting is inadequate. This problem exists in many workplaces.
Reflection is the ability of a surface to throw back light. The darker the surface the less light it will reflect and the more light will be required in the premises. Light reflected directly into the eye can cause glare.
Glare occurs when we look into a light which is brighter than that which the eye can adapt to. This can occur when the artificial lights are placed too low without a shield or when sunlight shines straight into the workplace. Indirect glare can occur when light is reflected off shiny surfaces. This can be avoided by using and properly positioning the correct type of lamp.
Most of the light should fall on the material or objects that we are working with. The light source should as a rule be positioned behind and to the side of the left shoulder if the person is right-handed. This only applies to the actual lighting of the individual work station. The nature of the work. The ability of the surrounding surfaces to reflect light. The size, form and light-reflecting properties of the material or object, and whether the object is easily distinguishable from the background. The eyesight of the workers.
General and local lighting
Poor background lighting and the lack of local lighting causes unsuitable working positions and fatigue, and can also help lower productivity and the quality of the work. The background lighting must provide an even spread of light throughout the entire premises. The light intensity must be adapted to the work being carried out. Stronger light is always needed for work on small workpieces and components and precision work. In practice one way of arranging this is by fitting local workplace lighting. The colour scheme of the premises is also important. The floors, walls and ceilings should be painted in light colours.
Normally the lighting in a work premises consists of general lighting or a combination of general and local lighting. General lighting is lighting from ceiling or wall lamps. General lighting illuminates the entire premises.
Local lighting is lighting placed near workers to give direct light to object(s). Combining general and local lighting allows the lighting to suit the worker and the work. Cleaning and maintaining lamps and fittings. The output of light decreases with the age of the light source. Wear of the light sources (lamps). Dirty fittings and/or dirty light sources. Dirt on the surfaces of the room. Dirty reflectors and dirty anti-glare devices. Dirt on the lamps and fittings is the biggest single reason for loss of lighting. Lamps and fluorescent tubes grow old. After a period of time only half of the original light is produced. It is therefore not enough to replace lamps when they burn out. They should all be replaced when the lighting becomes inadequate.
Regular service for lights is important. It also gives opportunities to think of better lighting.