Most commonly associated with outdoor flood lights, there are many options to choose from when designing an outdoor security lighting system. The most well-thought systems combine a mixture of lights designed for continual use with those designed to instantly switch on and and automatically turn off by means of a motion sensor detector. When properly implemented, the lamps should not only act as a deterrent against potential crime and mischief, but also allow homeowners to clearly see objects in the lit areas.

1. Outdoor Security Lighting - High-Intensity Discharge Lights
Most commonly associated with outdoor flood lights, there are many options to choose from
when designing an outdoor security lighting system. The most well-thought systems combine
a mixture of lights designed for continual use with those designed to instantly switch on and
automatically turn off by means of a motion sensor detector. When properly implemented, the
lamps should not only act as a deterrent against potential crime and mischief, but also allow
homeowners to clearly see objects in the lit areas.
Many lamp varieties are used in outdoor security lighting. Which lamps you decide to use is
going to depend, at least in part, on where you want the lights situated and how brightly you
want the area lit. Other factors that will affect your decision are desired light intensity, color
rendering index (CRI), correlated color temperature (CCT), lifespan, and energy efficiency.
Color rendering index refers to a lamp's ability to faithfully render colors, as compared with a
natural or optimal light source. Daylight is the typical benchmark. The higher a light registers
on this quantitative index, the more capable it is of faithfully producing colors.
CRI does not describe the visible color of the lamp. That is the job of correlated color
temperature.
Correlated color temperature refers to the specific temperature a theoretical light source
would need to be heated to achieve a light that produces a color of a reference source of
light. It is measured in degrees kelvin (K). Kelvin is a unit of absolute temperature; a topic
beyond the scope of this article.
CCT essentially measures the overall warmth or coolness of a lamp's appearance. Lower
temperatures refer to warmer light sources, and vice versa. Colors below 3200 K are
considered warm (red/yellow/gold), while colors above 4000 K are generally considered cool
(blue hue).
Lamps can be broken down into two main types: high intensity discharge (HID) and halogen.
Here's a brief description for HID:
HID lamps - have the longest lifespan and highest efficacy of any light source. Efficacy refers
to the amount of light produced as measured against the amount of energy expended in the
process. Simply put, this means they radiate more light per watt of electricity consumed
because a higher proportion of their radiation is light, as opposed to heat.
HID lamps manufacture intense light using an electrical arc. Electrical arc, in this instance,
refers to a process that involves a quick breakdown of the resistance of gas contained within
the bulb's quartz or alumina arc tube. This arc tube contains both gas and metal salts and
the breakdown occurs between 2 electrodes within the arc tube. Gas is used to provide the
initial spark.
Once sparked, the electrical arc gradually heats the metal salts contained within the arc tube.
The heating of these metal salts forms into a continuous plasma discharge, which greatly
adds to the light's intensity, while at the same time reducing its energy consumption.

2. HID lights require a ballast: a device used to ignite and harness the current flow within the arc
tube. More specifically, it converts existing voltage into a higher operating voltage in order to
spark the gas and metal salts into producing light. Once ignited, it can sometimes takes 5
minutes or more for the ballast to fully establish the electrical arc. This means it could take
more than 5 minutes for these lights to produce light once activated.
And the upshot of all this is that while HID lights are an excellent source of continual light,
they are much less so when it comes to motion sensor outdoor lighting, which requires a lamp
to immediately produce light. HID lights are best applied when incorporated with other
outdoor security lighting fixtures capable of instant activation.
HID Light Types
The type of gas used within the tube determines what kind of HID lamp you are working with.
Metal halide, neon, xenon, sodium, mercury, argon, and krypton are all HID lamp varieties.
Here's a brief overview of a few of the main types of HID lights:
Mercury vapor lamps - are the first generation HID lamp. Of all HID lights, mercury vapor
lamps are the least efficient. Original models produced a blue/green light, but more recent
models have toned down the blue/green affect by adding a phosphor coating to the bulbs.
The coating improves the CRI (color rendering index) and balances the light spectrum, which
gives the light a “white” appearance. Mercury vapor lights typically have an outer bulb that
contains the inner arc tube. The arc tube is comprised of quartz and is filled with mercury and
argon gas.
Metal halide and sodium vapor lamps are increasingly replacing mercury vapor lamps, both of
which are more efficient and have better color rendition than mercury vapor. Perhaps the
reason mercury vapor lamps have not completely disappeared is because of how long the
bulbs last. The average HID bulb life is 24,000 hours or more.
Metal halide lamps - emit an extremely bright light and provide the best color rendition of all
HID lamps. These lights are most commonly used in construction sites, commercial
buildings, parking lots, sporting arenas, and other areas where safety and security is the
primary goal.
Metal halide lamps have arc tubes that contain mercury, argon and metal halide gas. Metal
halide gas facilitates greater light intensity, better energy consumption, and better CTR and
CCT than what mercury vapors lamps are able to achieve.
Sodium vapor lamps - come in 2 varieties: low pressure and high pressure.
Low pressure sodium vapor lamps have the highest efficacy of all HID lights. The gases in
the arc tube of these lamps are solid sodium, argon, and neon. The lamp emits a faint
pink/red light as it begins to heat the solid sodium. As the sodium vaporizes, the lights display
the red/yellow glow they are known for.
A downside of these outdoor lights is they produce a monochromatic light. This means

3. objects all appear the same shade of color. These lamps are used in instances where color is
not a primary concern, which makes them useful for such things as highway, parking lot and
security lighting.
High pressure sodium lamps - as the name implies, work under high pressure and high
temperature. The result is a more visually appealing light, but this is accomplished at the
expense of energy efficiency.