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Basic Lighting Concepts
Lighting always begins with an application. If there were no application then there would be no need for light. More specifically an "application" is a need. In many cases it is a specific need. For example let's compare a reading light and a ceiling mounted light which both technically emit the same number of lumens. Both provide light and both will allow you to read a book. However, one is more specifically suited to filling the application of a "reading light". On the other hand however, the light from a ceiling fixture will be far more effective at lighting the room than the reading light ever could be. Because of the seemingly limitless lighting applications in use today, it stands to reason that there are many important factors to consider in the design of a lighting system. Here is a list of a few of these concerns which are not listed in any pertinent order:
Application Details
Size
Beam pattern or light distribution
Heat Output
Goals, Preferences, or Purposes
Legal Requirements
Color
Intensity
Efficiency
Budget
As you may already have noted, some of these factors are actually interrelated. Let's consider each of them further:
Application Details
Application details deals specifically with the details/requirements of the application (the customer's need or existing luminaire (fixture)).
Here are a few examples that further explain the concept:
Does the application require a light source which will emit low levels of heat?
Near babies
Near flammable materials
Near food
Refrigeration/coolers
Food warming
Lighting livestock or poultry areas during winter months
Curing plastics or glue
Any application which requires both light and heat
Does the application require a light source which will operate at low voltages?
Automotive
Flashlights
Battery operated devices
Marine
Aircraft
Does the application require an extremely small light source?
A toy
&nsbp;A very small flashlight
Elevator buttons
Automotive Dashboard
Indicator lights
Beam Pattern or Light Distribution
Dispersal pattern refers to the pattern of how the light disperses or spreads from the light source. This is tied to some degree into "Application Details." A specific dispersal pattern may be required for a particular application or, in a general lighting application, the customer may simply prefer a particular pattern. The dispersal pattern in many cases is defined not only by the light source itself (the bulb) but also by the luminaire (fixture) it is mounted in. To be overly detailed, when considering the total application, the dispersal pattern of a light source is also affected by the distance, size, shape and color of the surfaces that the light from the source will actually strike (this of course includes the surfaces of the luminaire as well). Some luminaires for example affect the dispersal pattern of a light source and some don't.
Here are a couple of examples of "luminaires" that have little to very little affect on the dispersal pattern of a light source:
Here are a couple of example of luminaires that have a greater affect on the dispersal pattern of a light source:
Here are a couple of examples of beam patterns:
Heat Output
Various light sources (e.g. incandescent, fluorescent, LED) emit more or less heat at various sizes and levels of power consumption when compared with others. In a particular application the heat of a light source may or may not be of any great importance. Here are just a few of the factors to consider:
The amount of heat the application needs.
For example: Food warming or curing chemicals
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The amount of heat that is safe in an application that requires heat, For example: animal husbandry or aquarium/terrarium lights
The amount of heat the luminaire can handle, For example: a night light or a recessed can fixture.
The amount of heat the light source can handle, For example: using a light bulb inside an oven or microwave will subject the light source to significant heat (more than normal) which when using the incorrect light source can result in early failure.
Goals, Preferences or Purpose
What is the goal of the customer and/or application? Here are a few examples:
Provide accent lighting
Reduce energy consumption
Increase/decrease light intensity
Direct light more effectively or to light a specific item or spot
Adjust the "mood" or "feel"of the light
Change to or from a dimming lighting system
Light an area via indirect lighting
Light an area using a particular type of luminaire or lighting system (e.g. track lighting, wall sconces)
Increase safety in an area by providing more light
Increase safety by using a shatter resistant light source
Render colors more vividly
Render colors more accurately
Increase/decrease heat output
Reduce flicker (most commonly in fluorescent systems)
Reduce ultraviolet output (which can cause pink colored raw meats to turn grey, accelerate aging for fruits and vegetables or accelerate fading of colored paint or fabrics)
Naturally, the customer's goal or the requirement of the application will either open up or restrict the options or type(s) of light sources that can be used.
Legal Requirements
Are there any legal requirements which will restrict the type of light source that can be used in the lighting application? Here are a few examples of lighting applications which by law not only require specific luminaires but most likely luminaires which use specific light sources. For example:
Exit signs
Emergency lights
Automotive signal lights
Locomotive signal lights
Traffic signals
Marine navigational bulbs
Color
In particular applications a particular color may be desirable or necessary. For example:
in their chicken coops, some farmers use red heat lamps to mask the appearance of blood. When all light is red then chickens cannot see blood.
red light is also used to stimulate the reproductive systems of chickens
bug lights are yellow
during their growth and production cycles plants need the blue and green portions of the spectrum. they do NOT however need green)
when lighting meat a light source which will make the meat appear more colorful (most often pink or red) and fresh is preferable
when lighting a subject that is a specific color, in many cases it is preferable to use a light source which emits a complimentary color
Intensity
Sometimes the intensity of the light in an application is key. The desired/required intensity in an application may more specifically refer to the intensity of the light delivered to one or more points. For example: is a "pin" spot (a very narrow spot beam) or a wide soft flood light desired or necessary? Look at these two pictures:
Note in the first picture how the majority of the intensity of the beam on the left is focused into a smaller "hot spot" in the center. The beam on the right provides a more even delivery but does not however provide the same intense "pin" spot beam that the light source on the left provides. In the second picture we see a conservative oval shaped beam. All three serve a purpose in the proper application.
Efficiency
This is one of the most misunderstood terms in lighting today. Efficiency actually is an EXTREMELY relative term. This is because what in one application is considered "efficient" may be quite inefficient in another application. To determine if a light source is efficient or not you actually have to start at the most basic stage of lighting: the application or need. What is the need? If an application requires no heat then ANY heat generated will be a complete waste (for example in a freezer). On the other hand what is the goal is to light a picture? In that case any light which falls anywhere other than the painting (unless it provides a needed symmetry) is a complete waste. Imagine trying to light a room with a spotlight. Even though the spotlight may emit three times the light output of a ceiling mounted light source with a spherical light distribution it will not light the area sufficiently or effectively. Here are some more examples:
Many have said that because of their inefficiency, traditional incandescent and many halogen bulbs are being phased out completely. First of all incandescent and halogen bulbs are not being phased out completely. In general lighting applications where visible light is the most important consideration, traditional incandescent bulbs are terribly inefficient. However, because of their ability to pack extreme intensity into such small light sources incandescent and halogen bulbs still serve many purposes. Their ability to withstand heat allows them to not only be used in the aforementioned compact high wattage applications but also in high heat applications (ovens for example).
Size
A great question is: "The size of what?" To answer that question