Most of the information about the world around us is perceived visually. This determines the crucial role of lighting for life. However, natural sources (the sun, scattered light from the cloudy sky, the moon, insects, lightning, aurora borealis, etc.) do not always provide the necessary quality of illumination. That is why since ancient times man has faced the task of creating lighting with the help of man-made sources – fire or lamps of different types and designs. It is called artificial light. This article provides an overview of artificial lighting, its types, characteristics, classifications, sources.
Definition
Lighting created by natural sources is called natural. In some cases, it is not enough, so use specially created sources that provide artificial light (in modern conditions, usually electric). Such lighting is called artificial. Its purpose is to provide the established sanitary norms value of illumination.
As a rule, depending on the situation, to create artificial lighting uses a different number of different light sources located in different places. Therefore, the term “artificial lighting system” is often used. It is a group of artificial light sources for specific tasks (e.g. escape lighting system for exits in the event of an emergency shutdown of the main system).
Characteristics
Artificial lighting, like natural lighting, is characterized by a number of values, among which the main ones are the following
Luminous flux
The greater the power of the source, the brighter it shines. The light from the same source can be amplified by a reflector. Therefore, for lighting engineering plays a role not so much the power of the source, as its concentration, focus. The value that characterizes this parameter is called “luminous flux”. It is measured in lumens. One lumen equals the luminous flux of a light source with power of 1 candela inside a solid angle of 1 steradian (remember that a full sphere is a solid angle of 4π steradian).
Luminous flux is a more convenient value than luminous intensity, because people perceive concentrated light brighter, even if the light intensity is the same.
Illuminance
From everyday experience, we know that any light source illuminates better near than far. The value taking into account this feature – illuminance. The unit of illuminance is taken as lux. 1 lux is the illuminance of the surface with area of 1 m2, on which light flux of 1 lumen falls.
Luminous intensity
Light intensity describes the amount of energy emitted by a light source per unit of time. The unit of light intensity is candela. One candela is equal to the luminous intensity emitted by a surface with an area of 1/600000 m2 of the cross-section of a total emitter perpendicular to this cross-section at an emitter temperature equal to platinum solidification temperature (2042 K) at a pressure of 1 atm.
By strict definition, it is difficult to visualize this value. However, it is enough to remember that “candela” means “candle”. Consequently, the light intensity of 1 candela is the light intensity of approximately one candle.
In addition to these basic characteristics, there are special ones that are used in special cases – color rendering, color and spectral characteristics, etc.
What constitutes artificial light
Artificial refers to lighting for a certain range of tasks, created by artificial sources, usually electric (lamps, projectors, projectors). For example, the lighting of an open warehouse of building materials at night for security purposes. Another example – lamps in a mine or in an underground corridor.
Types and classifications
Artificial lighting is divided into varieties on the following grounds.
Purpose
The most common basis for classification is purpose. Artificial lighting is:
- working;
- emergency;
- duty;
- security;
- evacuation;
- standby.
Working lighting provides light conditions in the premises in accordance with sanitary standards in the normal, everyday mode. If there are no people in the room most of the time, but lighting is still necessary, it is advisable to use a special duty mode with mild requirements.
In many cases, security lighting is necessary as part of the physical security measures of the enterprise. It is designed to record illegal actions. Some authors point out that security lighting helps to create a sense of security for the staff of the enterprise and the residents of the surrounding areas.
An important part of the security system of enterprises and residential buildings is emergency lighting. It is used when the main one stops functioning. Fixtures for emergency operation have an autonomous power system, so they are used in case of complete power failure of the building.
In case of emergency, evacuation and backup lighting is also used. The main function of the emergency lighting is to make it possible for personnel to continue or complete work safely. Evacuation lighting is intended to evacuate building employees and residents as quickly and as safely as possible in an emergency. Some authors consider it a type of emergency lighting.
Sometimes as part of the working lighting is a separate subspecies – lighting of industrial areas of increased danger. It is used in jobs involving high risk, where the sanitary standards have particularly high demands on lighting.
Some authors are allocated in separate types of illumination, advertising and architectural lighting. Their main feature – they are designed to attract the attention of the viewer and for decoration. In this case, the color characteristics are of particular importance and are determined by the artistic concept.
According to location
Another basis for classification – the location of light sources. They can illuminate the entire room, and such lighting is called general. If the source illuminates only a small part of the room, this light is local.
Exclusively local lighting is undesirable. It creates too much contrast and the eye needs time to adjust when moving between different areas of the room. This causes discomfort and can affect safety.
Sometimes there is a difference between overhead and side lighting. The first is usually general. The second is local. Lateral lighting can be single or multifaceted.
According to the distribution of luminous flux
Another basis for classification is by distribution.
Ceiling luminaires with large diffusers of wide direction, as a rule, provide a uniform soft light flux across the room. Such light is called diffused, or general.
But if the room has several zones with different conditions and requirements, it is advisable to distribute lighting fixtures unevenly, according to the zones of the room. This lighting is called localized.
Sometimes indirect lighting is used – when the light source illuminates not the lighting zone, but a surface nearby, and the zone is illuminated by the light reflected from that surface.