Solid-state lighting (SSL)
- A technology using
semi-conducting materials to convert electricity into light. SSL is an umbrella term encompassing both
light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs).
Light-emitting diodes (LEDs)
- LEDs are based on
inorganic (non-carbon-based) materials. An LED is a semi-conducting device that produces light when an
electrical current flows through it.
Organic light-emitting diodes
(OLEDs) - OLEDs
are based on organic (carbon-based) materials. In contrast to LEDs, which contain small point sources, OLEDs are
made in sheets that provide a diffuse area light source. OLED technology is developing rapidly, but is still
some years away from becoming a practical general illumination source.
- A measure of the efficacy
of the complete luminaire, or fixture, taking into account the optics, thermal design, and other design factors
that impact efficacy. It is calculated by measuring the total light output of a luminaire, divided by the amount
of power drawn by that luminaire. It is expressed in lumens per watt (lm/W).
- A measure of the
efficacy of the light source, separate from the fixture. It is calculated by measuring the total light output
of a lamp/power supply system, divided by the power drawn by that system. (It does not account for losses
caused when that system is installed in a fixture.) It is expressed in lumens per watt
Illumination - The distribution of light on a
horizontal surface. The purpose of all lighting is to produce illumination.
Lumen - A measure of light emitted by a lamp.
As a universal reference point, a 100-watt incandescent lamp emits about 1750 lumens.
Color rendition (CRI)
- How colors appear when
illuminated by a light source. Color rendition is generally considered to be a more important lighting quality
than color temperature. Most objects are not a single color, but a combination of many colors. Light sources
that are deficient in certain colors may change the apparent color of an object. The Color Rendition Index (CRI)
is a 1–100 scale that measures a light source’s ability to render colors the same way sunlight does. The top
value of the CRI scale (100) is based on illumination by a 100-watt incandescent light bulb. A light source with
a CRI of 80 or higher is considered acceptable for most indoor residential applications.
(CCT) - The color of
the light source. By convention, yellow-red colors (like the flames of a fire) are considered warm, and
blue-green colors (like light from an overcast sky) are considered cool. Color temperature is measured in Kelvin
(K) temperature. Higher Kelvin temperatures (3600–5500 K) are what we consider cool and lower color temperatures
(2700–3000 K) are considered warm. Cool light is preferred for visual tasks because it produces higher contrast
than warm light. Warm light is preferred for living spaces because it is more flattering to skin tones and
clothing. A color temperature of 2700–3600 K is generally recommended for most indoor general and task lighting