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May 2018

Overview of the principles of lighting technology

In general, we tend to take light for granted. However, a great deal of work goes into the installation of a lighting system. Lighting a space in the best possible way is no easy task. The principles of lighting technology guide us in the selection of appropriate lighting systems and a suitable setting that will illuminate a space to perfection. These principles represent the set of techniques used to install light systems that produce optimal visual acuity and create a pleasant atmosphere.

Here is an overview of the basic principles of lighting technology.

Basic notions

For lighting to be effective in a given space, a number of variables must be taken into account, namely:

  • the human requirements
  • the spatial architecture
  • the existing economy
  • the existing surroundings

Moreover, proper lighting must necessarily comply with a number of codes and standards. In Canada, we must adhere to the Illuminating Engineering Society (IES) standards as well as the Canadian Occupational Health and Safety Regulations.

A preliminary analysis is indispensable prior to choosing the most suitable lighting system; to that end, the following questions might be helpful:

  • What are the underlying needs that this lighting system installation will address?
  • Who will benefit from the installation of this lighting system?
  • What activities or tasks will be carried out in this space?
  • How does the environment affect the space that needs to be fitted with a lighting system?
  • What are the maintenance requirements of the lighting installation?

Measures related to lighting technology

A number of additional factors and criteria come into play when selecting the most suitable lighting system and illuminating a given space in the most optimal fashion. The following is a list of some of these factors and criteria:

Brightness and illumination

The above two characteristics refer to the link between the fluctuation of light, or the function of the space through which light travels and the thickness it penetrates. Both brightness and illumination are calculated using the Beer-Lambert Law, a mathematical formula that recognizes changes in light intensity based on distance light has travelled in a transparent environment.

Luminance of the sky

Luminance of the sky is merely the light that naturally shines on us at a given moment. We gather that this luminance is continuous whatever its course.

The luminous factor

We must also take the luminous factor into account. It reflects the connection between light intensity level dispersed in one direction and the apparent surface of the light source in the same given direction. This factor is expressed in candela per square metre (cd/m2).


Glare prevents us from seeing clearly. It might be caused by a blazing, inconsistent or even by a poorly projected light source.

The amount of glare that originates directly from a luminaire is calculated using the UGR method (Unified Glare Rating). It gauges the degree of discomfort caused by glare based on background luminance. The rating may vary from 10 to 30. The latter number determines the highest glare level.

The utilization factor

In the field of lighting, the utilization factor corresponds to the ratio of luminous flux consumed versus the total amount of luminous flux originating from a given light source.

Energy efficiency

Growing environmental and economic concerns compel us to prioritize energy efficiency in our lighting systems and make a concerted effort to reduce energy consumption. A cost-efficient, well-adjusted lighting system will help reduce energy usage.

Artificial light sources

Light originates from natural as well as artificial sources. Let us look at possible artificial light sources:

  • Incandescent lamps
  • Fluorescent lamps
  • MH systems (metal halide, sodium, and mercury)
  • Induction systems, LED and plasma, etc.
  • Ballasts as well as type circuits

Faced with this assortment of lighting types, it might be difficult, at times, to select the one best suited for our needs. Fortunately, there are several variables at hand to help make the best choice.

Lamp Designation

We need to select the proper bulb format. Should it be the standard form bulb, the spherical-shaped, flame or spot bulb? The articles entitled Lamps in All Shapes and Lamp Bases in All Shapes and Sizes offer useful information to help you make your decision.

Additionally, there are lamp features to consider. Information in this regard is usually found on the packaging. You might also wish to examine the guidelines in How to Read Lighting Product Labels.

Color Temperature

Color temperature specifies the color of a light source. It is measured in Kelvin and fluctuates from warm colors for a cozy atmosphere to cold colors that suit a contemporary style.

Color Rendering Index

The Color Rendering Index allows us to determine the ability of a light source to accurately generate the colors of a given object. It is usually represented as a number that varies between 0 and 100, 100 being the natural source that renders all colors most accurately.


Efficiency is identified in Lumens per watt (lm/W) and corresponds to the ratio of luminous flux of a light source to the light power it consumes. The need for energy efficiency varies according to the activities carried out in the space. For more information, read our article How to Measure Light.

Light depreciation curve of the flux and lifespan of a lighting system

The light depreciation curve of the flux indicates the useful lifespan of a lighting system while the mortality curve indicates its total lifespan. It is the point in time when the luminous flux no longer operates.

Indeed, while a lighting system might still diffuse light, it may not be sufficient in the long run to meet existing needs. This is what is called light depreciation. Read our article on Luminaire Dirt Depreciation for more information.

Controlling light source

It is also important to examine the means to control a light source in terms of:

  • illumination time
  • dimming capacity
  • the compatibility of a given light source with various communication protocols (DALI, DMX, etc.)

Natural light sources

Above all, any natural light comes to us from the sky, be it a clear blue sky filled with sunlight or a cloudy sky. The amount of available natural light, then, varies according to the time of day, existing weather conditions, and obstacles in the space.

From this perspective, the light of day is a factor. This factor identifies the ratio between an exterior light source and the available light inside a given space.

Moreover, natural light combines two forms of light: direct sunlight and sky diffused light.

  • Direct sunlight is simply luminosity that comes to us directly from the sun. Although this is an important light source, it is not reliable. It can be too insufficient or glare too brightly on the occupants.
  • Sky diffused light is the luminosity that comes to us quite naturally without any sun. It causes little to no glare. However, it might be too insufficient at times to provide adequate lighting.

In the end, the environment and the architecture of a given space may affect the amount of natural light that illuminates a given space.

Influence of the environment

The amount of light that a building receives depends on the environment that surrounds the building (the lay of the land, other facilities in the vicinity of the building, or even the landscape). For instance, a tree planted directly in front of a window prevents light from shining through.

The influence of architecture

The intrinsic architecture of a building may also affect the amount of available natural light.

For example, the location of windows redefines the natural light that shines into a room. Install windows in such a way as to maximize the input of sunlight. In this context, spaces that require morning light should be eastbound while other spaces that are occupied during the day should face south, and rooms that are used in the evening should face in a westerly direction.

Read our Lighting application recommendations to find lighting solutions for specific needs.

In conclusion, the principles of lighting technology are numerous and complex. Leave nothing to chance when selecting a lighting system that produces optimal visual acuity. Our Project department builds energy audits. These are an evaluation of your current lighting situation along with solutions to improve it.

Request a free energy audit today