Lighting Flashcards
Efficacy
A rating based upon the lumens per watt consumed, reflecting the energy efficiency of a lamp. Lumens divided by wattage. The higher the number, the more efficient.
IES / IESNA
Illuminating Engineering Society / Illuminating Engineering Society of North America
Luminous Flux
It is the density of light at any given point on a surface. Measured in footcandles or lux
E (illuminance) = Ø (incident flux) / A (area)
Density of flux incident on a surface is measured perpendicular to the surface.
Luminance
Light that is reflected from a surface in a given direction (back towards the eyes). Properly defined as intensity of flux leaving a surface in a given direction.
Measured in candela per square foot = Intensity / Area
Luminous exitance
Total quantity of light emitted, reflected or transmitted in all directions from a surface. Properly defined as density of flux leaving a surface.
Measured in lumens per square foot.
Luminous exitance = Departing luminous flux / Area
Intensity
Light emitted in a specific direction by a source properly called luminous intensity. Measured in candela.
Flux
It is lighting emitted in all directions by a source. Properly called luminous flux and defined as time rate flow of light.
Measured in lumens (lm)
ADAAG
Americans with Disabilities Act Accessibility Guidelines
Light
Visually evaluated radiant energy
Layers of light
Task, focal/display, ambient, decorative
CRI
Color rendering index. Higher the number, better the rendering. 1-100.
CT
Color temperature
CCT
Correlated color temperature
Illuminance
The total amount of light falling on a surface, measured in lux (lx) or foot-candle (fc).
HID
high intensity discharge
