C4-9:10 Flashcards
It is a graphical representation that illustrates the luminous intensity around the cross-section of a lamp or luminaire. It is a curve on a polar graph that shows the relative luminous intensity, in candela, around the lamp or luminaire.
Candlepower (Candela) Distribution Curve
90 to 100% of the light is directed downward for maximum use.
Direct
90 to 100% of the light is directed to the ceilings and upper walls and is reflected to all parts of a room or 90 to 100% of the light is directed downward for maximum use.
Indirect
60 to 90% of the light is directed downward with the remainder directed upward.
Semidirect
Equal portions of the light are directed upward and downward.
General diffuse/ direct-indirect
Beam projection distance and focusing ability characterize this luminaire
Highlighting
Is excessive brightness in the field of vision that causes discomfort or, in extreme cases, produces a disability from a temporary loss of vision. It is a visual sensation caused by luminance that is sufficiently greater than the luminance to which the eyes are adapted.
Glare
Is a rating of a lighting installation expressed as a percentage of individuals who, when viewing from a specified location and in a specified direction, will be expected to find it acceptable in terms of discomfort glare.
Visual Comfort Probability (VCP)
This type of glare causes visual discomfort without necessarily impairing vision.
Discomfort glare
Occurs when visibility is impaired from excessive brightness
Disability glare
Occurs when excessive light enters the eye directly from a light source
Direct glare
The result of light entering the eye after reflecting off a glossy surface.
Reflected glare
The reflection on a glossy surface that impedes seeing such as the reflection on a compute screen or on a glossy sheet in a magazine.
Veiling reflection
A zone above a 45° angel from the fixture’s vertical axis.
Glare zone
Typically made from clear UV-stabilized plastics. Usually much less expensive but they provide less glare control that louvered fixtures.
Lenses
Slats in a light fixture that create openings for emitting light. It provide superior glare control and high visual comfort compared with lens-diffuser systems.
Louvers
Opaque or translucent elements that shield a light source from direct view. They are typically part of the light fixture. It prevents the light source from throwing light beyond a 30° angle from the fixture’s vertical axis.
Baffles
The amount of light incident (striking) a surface.
Illuminance
The amount of light leaving an object, this relating to how bright an object appears to the human eye.
Luminance
Unit of measure of illuminance (E), the intensity of light falling on a surface.
Foot-candle (fc)
The SI unit for illuminance, which is one lumen of light uniformly illuminating a one square meter surface.
Lux (lx)
_________________ are measured in foot-candles or in terms of lumens per square meter or lux. ____________ is measured in lumens.
Light Intensity, Light Output
These categories have ranges of illuminance from 2-3-5 to 10-15-20 fx. For ambient lighting in public and working spaces.
Categories A through C
These categories have ranges of illuminance from 20-30-50 to 100-150-200 fc. For common visual task requiring more difficulty.
Categories D through F
